JP2003272705A - Film packaged nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film packaged nonaqueous electrolyte secondary battery with high battery characteristics especially high charging discharging characteristics and shelf life characteristics, and furthermore having high safety and no swelling of the outer shape of the battery. <P>SOLUTION: The nonaqueous electrolyte secondary battery is prepared by covering a power generating element containing at least a positive electrode, a negative electrode, an electrolyte, and a separator, and using a lithium manganese composite oxide in the positive electrode, and in the case where the electrolyte contains a composition which can generate hydrogen ions by reacting with water, a hydrogen ion trapping agent is arranged in a place in contact with the electrolyte inside the battery. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a film-covered non-aqueous electrolyte secondary battery in which a power-generating element is covered with a film. More specifically, it relates to a film-coated non-aqueous electrolyte secondary battery in which swelling is suppressed.

[0002]

2. Description of the Related Art A power generating element is enclosed in a film outer package such as an aluminum laminate film obtained by laminating a heat-fusible resin film on an aluminum foil, and metal leads for taking out an electric current pass through the fused portion of the film outer package. Conventionally, a non-aqueous electrolyte battery having a configuration of being taken out from inside to outside is known. With the recent trend toward thinner and lighter electronic devices, there is a strong demand for thinner and lighter batteries, and such film-encased batteries are more advantageous than batteries using a hard metal can as an outer body. is there.

In addition to general battery performance such as (a) high energy density (high charge / discharge capacity), high cycle characteristics, and storage capacity characteristics due to self-discharge, (b) Since the outer packaging is a flexible film, it has characteristics such as safety, for example, less deformation of the outer shape, etc., as compared with a battery using a metal can as the outer packaging.

Recently, lithium manganate has been highly expected as one of the positive electrode materials for lithium ion secondary batteries. Lithium manganate has a spinel structure represented by the chemical formula LiMn ₂ O ₄ , and functions as a 4V-class positive electrode material in the composition with λ-MnO ₂ . Since lithium manganate having a spinel structure has a three-dimensional host structure different from the layered structure of LiCoO _{2 and the} like, most of the theoretical capacity can be used and it is expected that the cycle characteristics will be excellent.

In addition, since lithium manganate having a spinel structure can extract lithium ions while maintaining the basic skeleton, the oxygen desorption initiation temperature during charging is higher than that of lithium cobalt oxide having a layered rock salt structure. And is expected as a positive electrode material with excellent safety. Such safety is important especially in the case of a film-clad battery using a flexible film as an outer package.

However, in practice, a lithium secondary battery using lithium manganate as a positive electrode cannot avoid capacity deterioration in which the capacity gradually decreases due to repeated charging and discharging, and there is a big problem in its practical application. Was left.

Therefore, various methods have been investigated to improve the cycle characteristics of the organic electrolyte secondary battery using lithium manganate as the positive electrode. For example, characteristic improvement by improving reactivity during synthesis (Japanese Patent Laid-Open No. 3-67464, Japanese Patent Laid-Open No. 3-119656, Japanese Patent Laid-Open No. 3-12).
7453, JP-A-7-245106, JP-A-7-73883, etc.), and characteristic improvement by controlling the particle size (JP-A-4-198028, JP-A-5-28307, JP-A-6-295724, JP-A-7-97216, etc.), and characteristic improvement by removing impurities (JP-A-5-21063).
However, none of them have achieved satisfactory improvement in cycle characteristics.

In addition to the above, Japanese Patent Laid-Open No. 2-270268 makes an attempt to improve the cycle characteristics by making the Li composition ratio sufficiently excess with respect to the stoichiometric ratio. Regarding the synthesis of a similar excess Li-composite composite oxide, JP-A-4-123769 and JP-A-4-1-1.
It is also disclosed in Japanese Patent No. 47573, Japanese Patent Laid-Open No. 5-205744, Japanese Patent Laid-Open No. 7-228798. The improvement in cycle characteristics by this method can be clearly confirmed experimentally.

[0009] As an effect similar to the Li excess composition, an Mn spinel material LiMn ₂ O ₄ and a Li-Mn composite oxide Li ₂ M richer in Li than this material are used.
A technique in which n ₂ O ₄ , LiMnO ₂ , Li ₂ MnO _{3 and the} like are mixed and used as a positive electrode active material is also disclosed in JP-A-6-338320.
Japanese Patent Laid-Open No. 7-262984 and the like. However, if Li is added excessively or another L
When mixed with an i-rich compound, the cycle characteristics are improved while the charge / discharge capacity value / charge / discharge energy value is decreased, so that there is a problem that both high energy density and long cycle life cannot be achieved at the same time. On the other hand, in Japanese Patent Laid-Open No. 6-275276, a high energy density,
Attempts have been made to increase the specific surface area with the aim of improving the high-rate charging / discharging characteristics (the current during charging / discharging is larger than the capacity) and the completeness of the reaction. Have difficulty.

On the other hand, studies have been conducted to improve the characteristics by adding another element to the three-component compound of Li-Mn-O. For example, addition or doping of Co, Ni, Fe, Cr, Al or the like (Japanese Patent Laid-Open No. 14195/1992).
No. 4, JP-A-4-160758, and JP-A-4-160758.
169076, Japanese Patent Laid-Open No. 4-237970,
JP-A-4-282560, JP-A-4-28966
No. 2, JP-A-5-28991, JP-A 7-1.
Disclosed in Japanese Patent No. 4572). Addition of these metal elements is accompanied by a reduction in charge / discharge capacity, and further improvement is required to satisfy the total performance.

In the study of the addition of other elements, the addition of boron is expected to improve other characteristics such as cycle characteristics and self-discharge characteristics with almost no decrease in charge / discharge capacity.
For example, JP-A-2-253560 and JP-A-3-29
This is disclosed in Japanese Patent No. 7058 and Japanese Patent Laid-Open No. 9-115515. In both cases, manganese dioxide or lithium-manganese composite oxide is solid-phase mixed with a boron compound (for example, boric acid) or immersed in an aqueous solution of a boron compound, and heat-treated to synthesize a lithium-manganese-boron composite oxide. ing. Since the surface activity of these composite particle powders of a boron compound and manganese oxide was reduced, it was expected that the reaction with the electrolytic solution would be suppressed and the storage characteristics of the capacity would be improved.

[0012] However, the mere addition of boron causes grain growth, a reduction in tap density, and the like, which does not directly lead to an increase in battery capacity. In addition, depending on the synthesis conditions, the capacity may decrease in the effective potential range when combined with the carbon negative electrode, or the reaction with the electrolytic solution may be insufficiently suppressed, and there is an effect that is satisfactory in improving storage characteristics. It didn't happen.

On the other hand, when lithium manganate was used for the positive electrode of the film-clad battery, the expected safety was not satisfactory. That is, if the charge / discharge cycle is repeated or if the battery is stored in a charged state at a high temperature, a gas that is considered to be derived from the decomposition of the electrolytic solution is generated and the internal pressure rises. There was a problem of swelling. It is a safety issue if the battery exterior ruptures due to excessive gas generation, but even if it does not rupture, the expansion of the battery outline will exceed the storage dimensions when it is installed in an electric device and press the surroundings. There is also the problem of doing.

[0014]

Although lithium manganate LiMn ₂ O ₄ as has been described above [0005] a composite oxide gather great expectations current mainstream of the positive electrode active substitute material for material LiCoO _2, a conventional LiMn ₂ Batteries using O ₄ have two problems: (1) it is difficult to achieve both high energy density (high charge / discharge capacity) and high cycle life, and (2) reduction of storage capacity due to self-discharge. In addition, (3) When LiMn ₂ O ₄ is used in a film-clad battery, repeated charge / discharge cycles or storage in a charged state at high temperature may result in decomposition of the electrolytic solution. There was a problem that the possible gas is generated and the outer shape of the battery swells.

As the causes of these problems, it has been pointed out that there are technical problems in battery production and compatibility with the electrolytic solution.
Focusing on the positive electrode material itself and the influence of the positive electrode material, the following can be considered.

(1) High energy density (high charge / discharge capacity)
Achieving both high cycle life and high cycle life: The cause of the problem of capacity deterioration associated with charge / discharge cycles is that the average valence of Mn ions changes between trivalent and tetravalent as charge compensation due to the inflow and outflow of Li. Teller strain is generated in the crystal and Mn from lithium manganate
The increase in impedance is caused by the elution of Mn or the elution of Mn. That is, as the cause of capacity deterioration in which the charge / discharge capacity is reduced by repeating the charge / discharge cycle, influences of impurities, elution of Mn from lithium manganate and precipitation of the eluted Mn on the negative electrode active material or on the separator, activity It is considered that the particles are inactivated by the release of the substance particles, the effect of the acid generated by the water content, and the deterioration of the electrolytic solution due to the release of oxygen from the lithium manganate.

When a single spinel phase is formed, Mn is eluted in the electrolytic solution by partially disproportionating trivalent Mn in the spinel structure into tetravalent Mn and divalent Mn. It is considered that Mn easily dissolves in the metal and that it is eluted due to the relative lack of Li ions. Repeated charging / discharging causes irreversible capacity generation and disorder of atomic arrangement in the crystal. Is promoted, the eluted Mn ions are deposited on the negative electrode or the separator, and L
It seems to hinder the movement of i-ions. In addition, lithium manganate is distorted in cubic symmetry due to the Jahn-Teller effect when Li ions are taken in and out, and accompanied by expansion and contraction of several% of the unit lattice length. Therefore, it is expected that by repeating the cycle, some electrical contact failure may occur, or the released particles may not function as the electrode active material.

Further, it is considered that release of oxygen from lithium manganate is facilitated in association with elution of Mn. Lithium manganate, which has many oxygen defects, has a large 3.3V plateau capacity as the cycle progresses, and as a result, the cycle characteristics deteriorate. Further, it is presumed that a large amount of released oxygen affects the decomposition of the electrolytic solution, which may cause cycle deterioration due to deterioration of the electrolytic solution. In order to solve this problem, improvement of synthesis method, addition of other transition metal elements, excess Li composition, etc. have been studied so far, but it is necessary to secure both high discharge capacity and high cycle life at the same time. I haven't arrived. Therefore, reducing Mn elution,
Measures such as reducing lattice distortion and reducing oxygen deficiency are derived.

(2) Regarding the problem of decrease in storage capacity due to self-discharge: The cause of decrease in storage capacity due to self-discharge is due to insufficient alignment of positive and negative electrodes due to battery manufacturing process, internal contamination of electrode metal scraps, etc. Excluding the phenomenon of short-circuiting, it is considered that the storage characteristics are also improved by improving the stability of lithium manganate in the electrolytic solution, that is, suppressing the elution of Mn, the reaction with the electrolytic solution, the release of oxygen, and the like.

(3) Expansion of battery outer shape when LiMn ₂ O ₄ is used in a film-sheathed battery: As a cause of gas generation leading to expansion of the battery outer shape, M is formed on the negative electrode active material.
It is considered that n is deposited to form a high-resistance film on the surface of the negative electrode, which easily causes decomposition of the electrolytic solution on the surface of the negative electrode to generate hydrogen gas. Further, it is considered that oxygen gas, carbon monoxide gas, carbon dioxide gas, etc. are generated on the surface of the positive electrode due to the release of oxygen from lithium manganate. This leads to swelling of the outer shape of the battery in the film-clad battery.

The problems (1) to (3) described above are a major obstacle to the expansion of applications because the deterioration thereof is promoted particularly when used in a high temperature environment. However, the charge / discharge capacity is limited because the material systems that can expect the potential to satisfy the performance required for current high-performance secondary batteries, such as high electromotive force, voltage flatness at discharge, cycle characteristics, and energy density, are limited. There is a demand for a new spinel-structured lithium manganate without deterioration, which has excellent cycle characteristics and storage characteristics.

By the way, JP-A-10-112318 describes that a mixed oxide of a lithium manganese composite oxide such as LiMn ₂ O ₄ and a lithium nickel composite oxide such as LiNiO ₂ is used as a positive electrode active material. Has been done. According to this publication, the irreversible capacity in the first charge / discharge is compensated, and a large charge / discharge capacity is obtained. Further, JP-A-7-235291 also describes that LiMn ₂ O ₄ is mixed with LiCo _0.5 Ni _0.5 O ₂ and used as a positive electrode active material.

However, according to the study by the present inventor,
If only the mixed oxide of lithium-manganese composite oxide and lithium-nickel composite oxide is used as the positive electrode active material, the charge and discharge characteristics, especially the cycle life at high temperature, the capacity storage characteristics and the self-discharge characteristics can be satisfied. No results were obtained. The reason for this will be described in detail later, but not all lithium-nickel composite oxides can capture hydrogen ions, and only the specific lithium-nickel composite oxide specified in the present invention is limited to lithium-manganese composite oxide. This is because it is possible to effectively prevent the deterioration of the product or the electrolytic solution.

Further, if only a mixed oxide of lithium-manganese composite oxide and lithium-nickel composite oxide is used as the positive electrode active material of a battery having a film as an outer package, it will not be possible to reduce the charge / discharge cycle and charge state. No effect was seen on the outer shape swelling of the battery due to storage (especially at high temperature).

Therefore, the present invention has been made in view of the above problems, and is excellent in battery characteristics, particularly charge / discharge cycle characteristics, storage characteristics, and safety, and further, batteries associated with charge / discharge cycles and storage. An object of the present invention is to provide a film-covered non-aqueous electrolyte secondary battery in which external bulging is suppressed.

[0026]

The present invention comprises a positive electrode, a negative electrode,
A power generation element including at least an electrolytic solution and a separator is packaged with a film, and in a film-coated non-aqueous electrolyte secondary battery using a lithium-manganese composite oxide as a positive electrode,
A non-aqueous electrolytic solution for film coating, characterized in that the electrolytic solution contains a composition capable of generating hydrogen ions by reacting with water, and a hydrogen ion scavenger is arranged at a position in contact with the electrolytic solution in the battery. Regarding the next battery.

The present invention also relates to a film-covered non-aqueous electrolyte secondary battery, wherein the electrolyte contains LiPF ₆ or LiBF ₄ as a supporting salt.

The present inventor has achieved the present invention as a result of extensive studies aimed at reducing the elution of Mn from the lithium-manganese composite oxide.

In a non-aqueous electrolyte secondary battery using a lithium-manganese composite oxide as a positive electrode active material, deterioration of cycle characteristics is caused by elution of Mn ions in the electrolyte solution. Can be used as an index, and the deterioration of the capacity storage characteristics is due to the Li in the electrolyte.
It can be judged by the fluctuation of ion concentration. In the case of a film-covered battery, gas generation that causes swelling is caused by decomposition of the positive electrode active material (elution of Mn and release of oxygen), and Mn that is eluted along with it is deposited on the surface of the negative electrode. Since it is possible that the electrolytic solution is electrolyzed, the Mn ion concentration in the electrolytic solution can be used as an index for determination.

According to a study by the present inventor, L was used as the Li supporting salt.
When iPF ₆ or LiBF ₄ was used, the elution of Mn ions into the electrolytic solution was particularly large, while the acidity of the electrolytic solution when these supporting salts were used was obviously high. Therefore, these supporting salts react with a small amount of water present in the organic electrolyte to generate hydrogen ions (H +), which elutes manganese in the lithium-manganese composite oxide to form a crystal structure. It is estimated that it is deteriorating.

Therefore, by allowing a compound capable of capturing hydrogen ions to exist at a place where it can come into contact with the electrolytic solution, an increase in the concentration of hydrogen ions in the electrolytic solution can be suppressed, and as a result, Mn ions in the electrolytic solution can be prevented. We believe that elution was suppressed.

In fact, by using the hydrogen ion scavenger, the Mn ions eluted in the electrolytic solution are greatly reduced, the change in the concentration of Li ions existing in the electrolytic solution is suppressed, and the deterioration and discoloration of the electrolytic solution are further suppressed. Was suppressed, and the production of acid was also suppressed. In addition, the generation of gas was suppressed. As a result of the reduction of the elution of Mn ions into the electrolytic solution, the desorption of oxygen from the lithium-manganese composite oxide is similarly reduced, so that the deterioration of the crystal structure of the lithium-manganese composite oxide can be prevented. At the same time, it is possible to prevent generation of oxygen gas, carbon monoxide gas, and carbon dioxide gas.

As a result, according to the present invention, the cycle characteristics can be improved while maintaining a high charge / discharge capacity, and the increase in impedance can be avoided because the decomposition of the electrolytic solution and the change in Li concentration are suppressed. Moreover, the generation of gas can be further suppressed, and the outer shape of the battery can be prevented from swelling.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the appearance of an example of a film-covered non-aqueous electrolyte secondary battery. In addition, FIG. 2 schematically shows a cross section taken along the line AA ′ of the battery of FIG. The wound power generation element 2 is enclosed by a laminate film including a heat-fusible resin film 11, a metal foil 12 and a heat resistant resin film 13. The two laminated films face the inside of the battery so that the heat-fusible resin film faces, and the four sides of the power generation element are heat-sealed.
One side of them is the positive electrode lead 31 and the negative electrode lead 32.
The laminated film is heat-sealed so as to sandwich them in a state where they are pulled out from the power generation element 2. The laminate film is shaped so as to have a bottom surface portion and a side surface portion on both sides according to the shape of the power generating element 2.
The power generation element 2 is impregnated with a non-aqueous electrolyte solution. The power generation element 2 includes a positive electrode, a negative electrode, an electrolytic solution, and a separator (not shown).

The hydrogen ion scavenger used in the present invention is
Reacts with hydrogen ions (H +) present in the organic electrolyte,
It functions to reduce the hydrogen ion concentration. At this time, it is preferable to change to a compound or an inactive compound that does not adversely affect the battery system of the present invention as a result of reacting with hydrogen ions. On the other hand, those that produce water as a result of reacting with hydrogen ions are not suitable for the present invention because the water again reacts with the supporting salt to generate hydrogen ions. For example, it is not preferable that OH − ions react with hydrogen ions to generate water, such as alkali metal hydroxide. Further, it is not preferable that the reaction results in an excessive increase in battery impedance.

The hydrogen ion scavenger may be arranged in any place as long as it comes into contact with the electrolytic solution in the battery. For example, a method of mixing, dissolving or dispersing in an electrolytic solution or mixing in an electrode can be mentioned.

For example, as long as it can function as an electrode material, it can be mixed with the lithium-manganese composite oxide which is the positive electrode material used in the present invention to form an electrode. The hydrogen ion scavenger may be either an inorganic compound or an organic compound. Examples thereof include lithium-nickel composite oxide, hydrogen storage alloy, and carbon capable of storing hydrogen. These are preferably used in the form of powder, and can be used by being mixed with the positive electrode or dispersed in the electrolytic solution.

Next, a lithium-nickel composite oxide will be described as a preferred example of the hydrogen ion scavenger. The lithium-nickel composite oxide usable in the present invention has a hydrogen ion scavenging function. For example, the above-mentioned JP-A-10-112318 and JP-A-7-23529.
The lithium-nickel composite oxide described in Japanese Patent No. 1 cannot be said to have a hydrogen ion trapping function.

The lithium-nickel composite oxide is an oxide composed of lithium, nickel and oxygen, and LiN
iO ₂ , Li ₂ NiO ₂ , LiNi ₂ O ₄ , Li ₂ Ni ₂ O ₄ ,
In addition, those oxides may be partially doped with other elements for the purpose of stabilization, increase in capacity, and improvement of safety. As the oxide partially doped with another element, for example, an oxide obtained by doping LiNiO ₂ with another element is L
iNi _1-x M _x O ₂ (0 <x ≦ 0.5), M is a doped metal element, and Co, Mn, Al,
Represents one or more metal elements selected from the group consisting of Fe, Cu, and Sr. M may be two or more kinds of doped metal elements, and the sum of the composition ratios of the doped metal elements may be x.

Among these, LiNiO ₂ and LiNi
_1-x Co _x O ₂ (where x is usually 0.1 to 0.4) is preferred.

In the present invention, the Li / Ni ratio (Li / [Ni + M] ratio in the case of LiNi _{1- x} M _x O ₂₎ of the lithium-nickel composite oxide is slightly deviated from the stated stoichiometric ratio. The lithium-nickel composite oxide of the present invention includes such cases.

In the present invention, the lithium-nickel composite oxide having a specific surface area X of 0.3 or more is used to effectively prevent the deterioration of the lithium-manganese composite oxide or the electrolytic solution. Will be possible. The specific surface area is usually 5.0 or less. When the lithium-nickel composite oxide is mixed in the positive electrode, 3.
It is preferable to use one of 0 or less because a slurry that can be easily handled and coated with an electrode can be easily obtained when a positive electrode is manufactured.

Further, in the present invention, as the above-mentioned lithium-nickel composite oxide, one having a D ₅₀ particle size of 40 μm or less may be used, and by setting the D ₅₀ particle size to 40 μm or less,
It is possible to effectively prevent the deterioration of the lithium-manganese composite oxide or the electrolytic solution. The D ₅₀ particle size is usually 1 μm or more. When the lithium-nickel composite oxide is mixed in the positive electrode, it is preferable to use one having a thickness of 3 μm or more, because a slurry which can be easily handled and can be easily applied to the electrode when producing a positive electrode can be obtained. Here, the specific surface area means the surface area per unit weight of the powder (m ² /
g), which is measured by the gas adsorption method in the present invention.

The D ₅₀ particle size is a particle size corresponding to a weight cumulative value of 50% and is measured by a laser light scattering measurement method.

Such a lithium-nickel composite oxide can be manufactured as follows. First, as the lithium raw material, for example, a lithium compound such as lithium carbonate, lithium oxide, lithium nitrate, or lithium hydroxide can be used. Further, nickel hydroxide, nickel oxide, nickel nitrate or the like can be used as a nickel (Ni) raw material.

Both the lithium raw material and the nickel raw material are preferably crushed if necessary and adjusted to have an appropriate particle size before use. In particular, in order to obtain a predetermined specific surface area or D ₅₀ particle size, it is preferable to classify and use the particle size of the nickel raw material.

After that, the Li / Ni ratio is adjusted so as to match the desired composition ratio of the lithium-nickel composite oxide, and after sufficiently mixing, firing is performed in the same manner as in the production of the lithium-manganese composite oxide. The firing temperature is about 500 to 900 ° C.

The lithium-nickel composite oxide obtained by firing is preferably further classified to obtain a lithium-nickel composite oxide having a desired specific surface area or D ₅₀ particle size.

Since such a lithium-nickel composite oxide also has an effect as a positive electrode active material, it is preferably mixed with a lithium-manganese composite oxide and used as a positive electrode material. It is also possible to disperse it in the electrolytic solution.

The function of the lithium-nickel composite oxide as a hydrogen ion scavenger is not always clear, but it is presumed that the lithium ion in the crystal of the lithium-nickel composite oxide is replaced by the hydrogen ion.

When the lithium-nickel composite oxide is mixed with the lithium-manganese composite oxide to be used as the positive electrode material, [LiMn composite oxide]: [LiNi composite oxide] = 100-a: a By setting 3 ≦ a at this time, Mn eluted from the lithium-manganese composite oxide into the electrolytic solution can be further reduced, and thus cycle characteristics and capacity storage characteristics can be improved. . Further, by setting a ≦ 45, it is possible to obtain an extremely safe non-aqueous electrolyte secondary battery.

Next, the lithium-manganese composite oxide used as the positive electrode active material of the present invention will be described. The lithium-manganese composite oxide is an oxide composed of lithium, manganese, and oxygen, and examples thereof include lithium manganate having a spinel structure such as LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ , and LiMnO ₂ . Among these,
A lithium manganate having a spinel structure such as LiMn ₂ O ₄ is preferable, and as long as it has a spinel structure, [Li] / [Mn]
The ratio may deviate from 0.5, [Li] / [Mn]
The ratio is 0.5 to 0.65, preferably 0.51 to
0.6, most preferably 0.53 to 0.58.

Similarly, as long as lithium manganate has a spinel structure, the [Li + Mn] / [O] ratio is 0.
It may deviate from 75.

The particle size of the lithium-manganese composite oxide is a weight average particle size in consideration of easiness of preparation of a slurry suitable for preparing a positive electrode and uniformity of battery reaction.
It is usually 5 to 30 μm.

Such a lithium-manganese composite oxide can be manufactured as follows.

Manganese (Mn) raw material and lithium (L
i) As the raw material, first, as the Li raw material, for example, lithium compounds such as lithium carbonate, lithium oxide, lithium nitrate, and lithium hydroxide can be used, and as the Mn raw material, for example, electrolytic manganese dioxide (EMD), Mn ₂ O ₃ , M
Various Mn such as n ₃ O ₄ and chemical manganese dioxide (CMD)
Manganese compounds such as oxides, manganese salts such as manganese carbonate and manganese oxalate can be used. But L
Ease of securing the composition ratio of i and Mn, energy density per unit volume due to the difference in bulk density, ease of securing the target particle size, ease of process / handling in large-scale industrial synthesis, and prevention of harmful substances A combination of electrolytic manganese dioxide and lithium carbonate is preferable in consideration of the presence or absence of generation and cost.

As a pre-stage of mixing the starting materials, it is preferable that the lithium material and the manganese material are pulverized if necessary to obtain an appropriate particle size. The particle size of the Mn raw material is
It is usually 3 to 70 μm, preferably 5 to 30 μm. The particle size of the Li source is usually 10 μm or less, preferably 5
It is not more than μm, most preferably not more than 3 μm.

Since the reaction of forming the lithium-manganese composite oxide proceeds on the surface of the solid phase, if the mixing of the Li source and the Mn source is insufficient or the particle size is too coarse, the desired composition and In some cases, a lithium-manganese composite oxide having a structure cannot be obtained. For example, in the production of lithium manganate having a spinel structure, if the mixing of the Li source and the Mn source is insufficient or the particle size is too coarse, Mn
₂ O ₃ , Mn ₃ O ₄ , Li ₂ MnO ₃ , Li ₂ Mn ₄ O ₉ , Li ₄
A phase such as Mn ₅ O ₁₂ may be generated, and the battery voltage or the energy density may be lower than that of lithium manganate having a spinel structure. Therefore, in order to obtain a lithium-manganese composite oxide having a desired composition and structure, the particle size as described above is used in order to increase the contact area between the lithium raw material and the manganese raw material in order to increase the uniformity of the reaction. Is preferred. Therefore, particle size control or granulation of mixed powder may be performed. Moreover, by controlling the particle size of the raw material, a lithium-manganese composite oxide having a target particle size can be easily obtained.

Next, the respective raw materials are taken so that the Li / Mn molar ratio matches the desired composition ratio of the lithium-manganese composite oxide, sufficiently mixed, and fired in an oxygen atmosphere. As oxygen, pure oxygen may be used, or a mixed gas with an inert gas such as nitrogen or argon may be used. The oxygen partial pressure at this time is about 50 to 760 torr.

The firing temperature is usually 400 to 1000 ° C., but it is appropriately selected so as to obtain a desired phase. For example, when the firing temperature is too high for producing lithium manganate having a spinel structure, undesired phases such as Mn ₂ O ₃ and Li ₂ MnO ₃ are generated and mixed, and the battery voltage and energy density are insufficient. In addition, if the firing temperature is too low, oxygen may be relatively excessive or the powder density may be low, which may be unfavorable for realizing a high capacity. Therefore, in order to produce lithium manganate having a spinel structure, the firing temperature is preferably 600 to
900 ° C, most preferably 700-850 ° C.

The firing time can be adjusted appropriately, but is usually 6 to 100 hours, preferably 12 to 48 hours. The cooling rate can be adjusted as appropriate, but it is preferable not to quench it during the final firing treatment, and for example, a cooling rate of about 100 ° C./h or less is preferable.

The powder of the lithium-manganese composite oxide thus obtained is further classified, if necessary, and the particle sizes are adjusted to be used as a positive electrode active material.

The positive electrode used in the non-aqueous electrolyte secondary battery of the present invention uses a mixture of such a lithium-manganese composite oxide and a hydrogen ion scavenger as the case may be as a positive electrode active material. Furthermore, as a positive electrode active material,
In addition, a compound generally known as a positive electrode active material such as LiCoO ₂ may be mixed and used. Further, for safety and the like, a commonly used additive substance such as Li ₂ CO ₃ may be further added. The method for producing the positive electrode is not particularly limited, but, for example, a powder of lithium-manganese composite oxide and a powder of lithium-nickel composite oxide,
For example, with a conductivity-imparting agent and a binder, after mixing with a suitable dispersion medium capable of dissolving the binder (slurry method), coating on a collector such as aluminum foil, drying the solvent, and then pressing. Film is formed by compression.

The conductivity-imparting agent is not particularly limited, and commonly used ones such as carbon black, acetylene black, natural graphite, artificial graphite and carbon fiber can be used. Also, as the binder, a commonly used binder such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) can be used.

Next, the electrolytic solution used in the present invention will be described. The electrolytic solution used in the present invention is one in which a supporting salt is dissolved in a non-aqueous solvent. The solvent is usually used as a solvent of the non-aqueous electrolyte, for example, carbonates, chlorinated hydrocarbons, ethers, ketones,
Nitriles and the like can be used. Preferably, the high dielectric constant solvent is ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GB).
L) or the like, and at least one kind of low-viscosity solvent such as diethyl carbonate (DEC) and dimethyl carbonate (D
MC), ethyl methyl carbonate (EMC), at least one kind of ester, etc. is selected, and a mixed solution thereof is used. EC + DEC, PC + DMC or PC + EMC are preferred.

As the supporting salt, LiClO ₄ , LiI, L
iPF ₆ , LiAlCl ₄ , LiBF ₄ , CF ₃ SO ₃ Li
At least one type is used. It is generally difficult to completely remove water from the above non-aqueous solvent, and it is easy to absorb water during the production of the battery. Therefore, the supporting salt often reacts with this trace amount of water to generate hydrogen ions. According to the study by the present inventor, particularly LiPF ₆ or L
It has been confirmed that iBF ₄ remarkably produces hydrogen ions, and the electrolytic solution tends to be acidic.

In the present invention, since hydrogen ions are effectively trapped, the effect of the present invention can be exhibited most effectively when applied to a battery system using an electrolytic solution which easily generates hydrogen ions. That is, LiPF ₆ or LiBF ₄ is most preferable as the supporting salt. The concentration of the supporting salt is, for example, 0.8 to 1.5M.

As the negative electrode active material, a carbon material such as lithium, a lithium alloy or graphite or amorphous carbon capable of inserting and extracting lithium is used.

The separator is not particularly limited, but may be woven cloth,
A glass fiber, a porous synthetic resin film or the like can be used. For example, a polypropylene or polyethylene porous film is suitable as a thin film having a large area, film strength and film resistance.

The film outer package that can be used in the present invention is not particularly limited, and a commonly used resin film, laminate film or the like can be used. When sealing is performed by heat fusion, it is preferable to use a laminate film configured such that a heat-fusible resin film capable of heat fusion is provided at least on the sealing surface side (power generation element side). For example, a heat-resistant resin film is laminated on one surface of the metal foil, and a heat-fusible resin film is laminated on the other surface.
A laminated film having a layered structure, a heat-resistant resin layer having a high melting point between the metal foil and the heat-fusible resin, or an adhesive layer for adhering both the metal and the heat-fusible resin, and if necessary a multilayer Examples include a laminated film having a structure.

Materials that can be used as the metal foil include aluminum, copper, stainless steel, nickel, gold,
Examples thereof include silver. Of these, aluminum is particularly preferable.

As the material of the heat resistant resin film, polyester (eg polyethylene terephthalate), nylon or the like can be used. As the material for the heat-fusible resin film, ionomer, polyethylene, polypropylene, or a material obtained by grafting an acid group such as maleic anhydride onto these, or a material obtained by copolymerizing an acid group such as maleic anhydride is used. it can.

Other examples of the film-like outer package that can be used include a film obtained by laminating the above heat-fusible resin film directly on a heat-resistant resin film such as polyethylene terephthalate or via an adhesive, or a heat-bonded film. Examples of such films include a resin film alone.

[0074]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. The specific surface area is Quant manufactured by Quanta Chrome.
Using aSorb, the D ₅₀ particle size was determined by Micro Tra
It was measured using an FRA manufactured by Company c.

[Evaluation Test Example 1] In the synthesis of lithium manganate, lithium carbonate (Li ₂ CO ₃ ) and electrolytic manganese dioxide (EMD) were used as starting materials.

As a pre-stage of mixing the above starting materials, Li ₂ CO ₃ was pulverized and EMD was classified for the purpose of improving reactivity and obtaining lithium manganate having a target particle size. When lithium manganate is used as a positive electrode active material of a battery, a weight average particle diameter of 5 to 30 μm is preferable in view of ensuring uniformity of reaction, easiness of slurry preparation, safety and the like. The particle size was 5 to 30 μm, which is the same as the target particle size of lithium oxide.

[0077] On the other hand, since the Li ₂ CO ₃ in order to ensure homogeneous reaction the following particle size desired 5 [mu] m, D ₅₀ particle size 1.
Pulverization was performed so as to have a size of 4 μm.

EMD and Li ₂ CO ₃ thus prepared to have a predetermined particle size were [Li] / [Mn] = 1.05 / 2.
Mixed so that

This mixed powder was heated in an atmosphere of oxygen flow to 80
Baked at 0 ° C. Next, fine particles having a particle size of 1 μm or less in the obtained lithium manganate particles were removed by an air classifier. At this time, the specific surface area of the obtained lithium manganate was about 0.9 m ² / g.

The tap density was 2.17 g / cc, the true density was 4.09 g / cc, the D ₅₀ particle size was 17.2 μm, and the lattice constant was 8.227 Å.

On the other hand, as a hydrogen ion scavenger, a specific surface area of 1.7 m ^{2 is} used as an example of a lithium nickel composite oxide.
/ G of LiNi _0.9 Co _0.1 O ₂ was prepared.

Lithium manganate and LiNi _0.9 Co _0.1 O ₂ prepared as described above were used in a weight ratio of 100-a:
When represented by a, a = 0 (comparative example), 1, 2, 3, 5,
Mix so as to be 10, 15, 20 and 5g of the mixed powder
Then, 10 cc of an electrolytic solution of a mixed solvent (50:50 (volume%)) of propylene carbonate (PC) and dimethyl carbonate (DMC) containing LiPF ₆ (concentration 1M) was placed in a closed container.

These closed containers are heated to 80 ° C.
Left for days. After that, the electrolytic solution was extracted, and the Mn ion concentration in the electrolytic solution was analyzed by ICP. The results are shown in Table 1.
Shown in.

[0084]

[Table 1] From these results, it is understood that the higher the LiNi _0.9 Co _0.1 O ₂ mixing ratio, the smaller the amount of Mn eluted in the electrolytic solution, and the higher the effect of trapping hydrogen ions. in this way,
It is expected that the stability of the positive electrode active material will increase even when the battery is used in a high temperature environment.

[Evaluation Test Example 2] The closed container prepared in Evaluation Test Example 1 was heated to 80 ° C. and left for 20 days. After that, the electrolytic solution was extracted, and the Li ion concentration in the electrolytic solution was analyzed by atomic absorption. The results are shown in Table 2.

[0086]

[Table 2] The Li concentration in the electrolytic solution of the mixed solvent of propylene carbonate (PC) and dimethyl carbonate (DMC) (50:50 (volume%)) containing LiPF ₆ (concentration 1M) was about 6
Based on the fact that it is 400 ppm, LiNi _0.9 C
It can be said that the higher the _0.1 O ₂ mixing ratio is, the more the decrease in Li concentration in the electrolytic solution can be suppressed.

From the results of the evaluation test examples 1 and 2, M in the electrolytic solution was mixed by mixing the lithium-nickel composite oxide.
It was found that n elution was reduced and the change in Li ion concentration in the electrolytic solution was suppressed. As a guideline, the mixing ratio of the lithium-nickel composite oxide is [lithium-manganese composite oxide]: [lithium-nickel composite oxide], with 1/3 or less of the Mn concentration when the lithium-nickel composite oxide is not mixed. = 100: a (weight%), a ≧ 3
Becomes Further, from the evaluation test example 2, it can be seen that when a ≧ 3, the Li concentration in the electrolytic solution is kept at 95% or more after being left at 80 ° C. for 20 days. From these results, in particular a
≧ 3 is preferable.

[Evaluation Test Example 3] As the lithium-manganese composite oxide, lithium manganate synthesized in the same manner as in Evaluation Test Example 1 was used, and as the lithium-nickel composite oxide, a specific surface area of 1.7 m ² / g of LiNi _0.8 Co
_A 2320 coin cell was prepared using _0.2 O ₂ . The positive electrode was kneaded at a mixing ratio (a = 10) of lithium manganate: LiNi _0.8 Co _0.2 O ₂ : conductivity imparting agent: PTFE = 72: 8: 10: 10 (wt%) to a thickness of 0.5 mm. It was rolled into a sheet and punched out with a diameter of 12 mm. Here, carbon black was used as the conductivity-imparting agent.
As the negative electrode, metal Li having a diameter of 14 mm and a thickness of 1.5 mm was used.
As the separator, a porous PP film having a thickness of 25 μm was used.
The electrolytic solution is a mixed solvent (5) of ethylene carbonate (EC) and dimethyl carbonate containing LiBF ₄ (concentration 1M).
0:50 (volume%)).

At the same time, for comparison, the positive electrode was made of lithium manganate: conductivity-imparting agent: PTFE = 80: 10: 10.
(% By weight), except that LiNi _0.8 Co _0.2 O ₂ was not included, a 2320 coin cell was prepared in the same manner for the negative electrode, the separator, and the electrolytic solution (Comparative Example).

A charge / discharge cycle test was performed using these coin cells. 0.5m cycle for both charging and discharging
A / cm ² constant current, charge / discharge voltage range is 3.0 to
It was performed at 4.5 V vs Li. The evaluation temperature was 10 ° C to 60 ° C in steps of 10 ° C.

# 50 / # 1 coin cells containing LiNi _0.8 Co _0.2 O ₂ (Example) and those not containing LiNi _0.8 Co _0.2 O ₂ (comparative example) at the cycle evaluation temperature (the 50th cycle of discharge relative to the discharge capacity of the 1st cycle). Table 3 shows the capacity remaining ratio (%). The coin cell of the present invention has a higher capacity remaining rate even if the cycle temperature is raised.

[0092]

[Table 3] [Evaluation Test Example 4] As the lithium-manganese composite oxide, lithium manganate synthesized in the same manner as in Evaluation Test Example 1 was used, and as the lithium-nickel composite oxide,
Using LiNi _0.8 Co _0.2 O ₂ having a specific surface area of 1.7 m ² / g and using an aluminum laminate film as an outer package, a film outer battery was experimentally produced.

First, lithium manganate and LiNi _0.8 C
o _0.2 O ₂ and the conductivity-imparting agent were dry-mixed and uniformly dispersed in N-methyl-2-pyrrolidone (NMP) in which PVDF as a binder was dissolved to prepare a slurry.
Carbon black was used as the conductivity-imparting agent. After coating the slurry on a 25 μm thick aluminum metal foil, N
A positive electrode sheet was obtained by evaporating MP. The solid content ratio in the positive electrode is lithium manganate: LiNi _0.8 Co
_0.2 O ₂ : conductivity imparting agent: PVDF = 72: 8: 10: 1
The mixing ratio (a = 10) was 0 (wt%).

On the other hand, the negative electrode sheet is carbon: PVDF =
Mix 90% (wt%) to NMP
And dispersed on a copper foil having a thickness of 20 μm.

The positive and negative electrode sheets produced as described above were rolled up using an elliptical winding core with a polyethylene porous membrane separator having a thickness of 25 μm interposed therebetween, and further hot pressed to obtain a thin elliptical electrode wound body. Got

On the other hand, polypropylene resin (sealing layer, thickness 70 μm), polyethylene terephthalate (20 μm
m), aluminum (50 μm), and polyethylene terephthalate (20 μm) in that order, two laminated films having a structure of being cut out are cut into a predetermined size, and a bottom surface part corresponding to the size of the above-mentioned electrode winding body is cut out in a part thereof. A recess having a side surface portion was formed. The electrode-wound body was wrapped so that they faced each other, and the periphery thereof was heat-sealed to produce a film-clad battery having a shape as schematically shown in FIGS. 1 and 2. The electrode wound body was impregnated with the electrolytic solution before the last one side was heat-sealed. The electrode winding body impregnated with the electrolytic solution corresponds to the power generation element in FIG. 1 electrolyte
LiPF ₆ of M was used as a supporting salt, and a mixed solvent of propylene carbonate (PC) and diethyl carbonate (DEC) (50:50 (volume%)) was used as a solvent. The last side was sealed under reduced pressure.

At the same time, for comparison, LiNi was added to the positive electrode.
_A film-clad battery was manufactured in the same manner except that _0.8 Co _0.2 O ₂ was not included and the solid content ratio was changed to lithium manganate: conductivity imparting agent: PVDF = 80: 10: 10 (wt%) (Comparative Example). .

Using these film-sheathed batteries,
A charging / discharging cycle test at 0 ° C. was performed. Charge 500
The discharge was performed up to 4.2 V at mA, and to 3.0 V at 1000 mA. FIG. 3 shows a cycle characteristic comparison of the discharge capacities at 55 ° C. of the film-clad battery in the case of containing LiNi _0.8 Co _0.2 O ₂ (Example) and the case of not containing LiNi _0.8 Co _0.2 O ₂ (Comparative Example). It can be seen that the film-clad batteries according to the examples of the present invention show less capacity deterioration even after repeated charge / discharge cycles.

[Evaluation Test Example 5] Lithium manganate synthesized in the same manner as in Evaluation Test Example 1 was used as the lithium-manganese composite oxide, and the lithium-nickel composite oxide as the hydrogen ion scavenger had a specific surface area of 1. 7m ² /
g using _{LiNi 0.8 Co 0.15 Al 0. 05 O} 2 of the trial the film-covered battery.

First, lithium manganate and LiNi _0.8 C
o _0.15 Al _0.05 O ₂ and a conductivity-imparting agent are dry-mixed,
N-methyl-2 in which PVDF as a binder is dissolved
-Pyrrolidone (NMP) was uniformly dispersed to prepare a slurry. The slurry was applied onto an aluminum metal foil having a thickness of 25 μm, and then NMP was evaporated to obtain a positive electrode sheet.

[0102] Lithium manganate solid content in the positive electrode is in _{weight%: LiNi 0.8 Co 0.15 Al 0} .05 O 2: conductive agent: PVDF = 80-x: x : 10: when formed into a 10 x ( The weight%) was tested with the values shown in Table 4. In Table 4, a (= x · 100/80, which is the same as the above-mentioned a) is also shown. As a comparative example, the test was also conducted in the case of x = 0 (a = 0).

On the other hand, the negative electrode sheet is carbon: PVDF =
Mix 90% (wt%) to NMP
And dispersed on a copper foil having a thickness of 20 μm.

The electrolyte solution was 1 M LiPF ₆ as a supporting salt,
A mixed solvent (50:50 (volume%)) of propylene carbonate (PC) and diethyl carbonate (DEC) was used. A 25 μm-thick polyethylene porous membrane was used as the separator.

A capacity preservation test at 55 ° C. was carried out using the film-clad battery thus produced. Charge 5
After constant current charging at 4.2 mA to 4.2 V, constant voltage charging was performed at 4.2 V for 2 hours. Then, the discharge capacities were measured when the battery was discharged at room temperature without any standing time and when it was discharged at room temperature for 28 days and then discharged.
The capacity was measured at 500 mA and a cutoff potential of 3.0 V in a room temperature environment.

Table 4 shows the storage capacity of the prototype film-encased battery after being left for 28 days (expressed as 4 W capacity), and the capacity of the storage capacity when discharged for no storage time (0
(Denoted as W capacity). In contrast to the comparative example, the example according to the present invention has a high storage stability even after being left for 28 days. In addition, the capacity of the film-sheathed battery increased due to the effect of mixing the high-capacity lithium-nickel composite oxide.

[0106]

[Table 4] [Evaluation Test Example 6] Using the film-clad battery produced in Evaluation Test Example 5, a safety test was conducted. The results are shown in Table 5. However, when lithium manganate is used as the main positive electrode active material, the safety is higher than that of Co-based ones, and it is difficult to confirm the difference in each safety evaluation item such as the short circuit test and the hot box. Therefore, in order to highlight the difference in safety under more severe conditions, the density of the positive electrode is 3.1 g / cm ³
Was set to a high value, and a film-clad battery was manufactured, and safety evaluation was performed. In the future, it is highly likely that the direction of higher capacity will be considered, so it is important to evaluate under the condition of high electrode density. The safety evaluation items were an overcharge test and a nailing test. The overcharge test was conducted under the conditions of 12V and 3C. The nailing test is a test for forcibly causing an internal short circuit by inserting a nail into the battery.
It was performed according to UL-1642 using the nail of No.

In the overcharge test, no smoke or ignition was observed even when x was 56 or more. On the other hand, in the nailing test, generation of a slight amount of steam or smoke was observed when x was 40 or more. Therefore, from the viewpoint of safety, x is preferably 36 or less and a ≦ 45.

[0108]

[Table 5] [Evaluation Test Example 7] Lithium manganate synthesized in the same manner as in Evaluation Test Example 1 and LiNi _0.8 Co _0.1 Mn _0.1 O ₂ as a lithium-nickel composite oxide were 100-by weight.
When a: a, a (% by weight) is 0 (comparative example),
3, 5, 10, 15, 20, 30, 35 were mixed at a mixing ratio of 5 g and 10 cc of LiPF ₆ (concentration 1
An electrolytic solution of a mixed solvent (50:50 (volume%)) of ethylene carbonate (EC) and diethyl carbonate (DEC) containing M) was placed in a closed container. At this time, LiN
i _0.8 Co _0.1 Mn _0.1 O ₂ , 3.0 m ² / g, 2.
^{36m 2 /g,1.50m 2 /g,0.71m 2 / g} ,
0.49m ² /g,0.30m ² /g,0.25m ² / g
7 types having a specific surface area of 7 were used.

The closed container thus prepared was heated to 80 ° C. and left for 20 days. Then, the electrolytic solution was extracted, and the Mn ion concentration in the electrolytic solution was analyzed by ICP.
The result is shown in FIG. It was found that the larger the specific surface area, the higher the effect of suppressing the elution of Mn in the electrolytic solution.

As described above, in order to ensure safety, it is desirable that (lithium manganate) :( lithium-nickel composite oxide) = 100-a: a (% by weight) and a ≦ 45. Has become clear. On the other hand, from FIG. 4, when the specific surface area is 0.25 m ² / g, the elution amount of Mn 232 when the lithium-nickel composite oxide is not added is 232
In order to suppress the elution of Mn to 1/3 or less of 0 ppm, the mixing ratio of the lithium-nickel composite oxide must be increased to 50%. Therefore, it is understood that the specific surface area X of the lithium-nickel composite oxide is preferably larger than 0.3 m ² / g.

[Evaluation Test Example 8] Lithium-manganese composite
Manga synthesized as an oxide in the same manner as in Evaluation Test Example 1
Lithium oxide and lithium-nickel composite oxide
Then, the specific surface area is 4.5m²/ G, 3.2m²/
g, 3.0m²/ G, 1.50m²/ G, 0.30m²/
5 kinds of LiNi_0.8Co_0.1Mn_0.1O₂Prepare powder
did. Lithium manganate, LiNi_0.8Co_0.1Mn
_0.1O₂And dry carbon black as conductivity enhancer
N-medium mixed with PVDF dissolved as a binder
Add to chill-2-pyrrolidone (NMP), knead and level.
Dispersed in one to prepare a battery slurry. At this time,
Lithium manganate: LiNi_0.8Co_0.1Mn _0.1O₂:
Conductivity imparting agent: PVDF: NMP = 30: 10: 5:
The mixing ratio (a = 25) was 5:50 (% by weight).

After measurement with a Brookfield viscometer, the slurry was uniformly applied onto a 25 μm thick aluminum metal foil, and then NMP was evaporated to obtain a positive electrode sheet. Table 6 shows the specific surface area of the lithium-nickel composite oxide, the viscosity / state of the slurry, and the coating state of the electrode.

[0113]

[Table 6] From Table 6, it can be seen that when the specific surface area is larger than 3.2 m ² / g, the slurry causes gelation, which makes electrode coating difficult. Therefore, the specific surface area of the lithium-nickel composite oxide is preferably 3.0 m ² / g or less.

Similar results were obtained with a D ₅₀ particle size, and in order to reduce the elution of Mn into the electrolytic solution, a D ₅₀ particle size of 40 μm was obtained.
The particle size of D ₅₀ is preferably 3 μm or more in the range where the electrode can be easily coated.

To summarize the results of the above evaluation test examples, the lithium-nickel composite oxide to be mixed has a specific surface area X from the viewpoint of Mn elution, slurry coatability, and printability.
Is most preferably 0.3 ≦ X ≦ 3.0 (m ² / g).

The lithium-nickel composite oxide to be mixed most preferably has a D ₅₀ particle size of 3 μm or more and 40 μm or less from the viewpoint of Mn elution, slurry coatability, and printability.

The ratio of the lithium-manganese composite oxide and the lithium-nickel composite oxide is [LiMn composite oxide]: from the viewpoint of Mn elution and safety.
[LiNi composite oxide] = (100-a): When a, 3 ≦ a ≦ 45 is preferable.

[Evaluation Test Example 9] Using the film-clad batteries of the present invention and the comparative example prepared in Evaluation Test Example 4, an initial thickness of the battery immediately after preparation and a charge / discharge cycle test at 55 ° C. were performed for 100 cycles. The thickness of the latter battery was measured. Charge 500mA to 4.2V, discharge 1000
It went to 3.0V in mA. The results are shown in Table 7. It can be seen that the example according to the present invention suppresses the outer shape swelling of the battery due to the charge / discharge cycle.

[0119]

[Table 7] [Evaluation Test Example 10] Using the film-clad batteries of the present invention and the comparative example produced in Evaluation Test Example 4, the outer shape swelling amount of the battery when stored at 60 ° C was evaluated. First, the initial thickness of the battery was measured, and then the battery was subjected to constant current charging at 500 mA to 4.2 V, and then constant voltage charging at 4.2 V for 2 hours. Then, the thickness of the battery was measured again after standing at 60 ° C. for 28 days. The results are shown in Table 8. It can be seen that the embodiment of the present invention suppresses the outer shape swelling of the battery due to storage.

[0120]

[Table 8]

[0121]

According to the present invention, since the concentration of hydrogen ions in the electrolytic solution can be effectively reduced, Mn is eluted from the lithium manganese oxide, which is the positive electrode active material, and Li in the electrolytic solution is dissolved. Since the change in concentration is suppressed, the charge / discharge cycle, especially the charge / discharge life at high temperature, is greatly improved.
In addition, the capacity storage characteristics are also improved. Further, the outer shape swelling of the battery due to charge / discharge cycles and storage is suppressed.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a film-covered non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a schematic view (cross-sectional view) showing an example of a film-covered non-aqueous electrolyte secondary battery of the present invention.

FIG. 3 is a diagram showing discharge capacities and cycle characteristics at 55 ° C. of film-clad batteries of Examples and Comparative Examples of the present invention.

FIG. 4 Specific surface area and M of lithium-nickel composite oxide
It is a figure which shows the relationship of n elution amount.

[Explanation of symbols]

1 Laminated film 11 Heat-fusible resin film 12 metal foil 13 Heat-resistant resin film 2 power generation elements 3 electrode lead 31 Positive electrode lead 32 negative lead

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Chinatsu Kambe             5-7 Shiba 5-1, Minato-ku, Tokyo NEC Corporation             Inside the company (72) Inventor Akira Kobayashi             5-7 Shiba 5-1, Minato-ku, Tokyo NEC Corporation             Inside the company (72) Inventor Masato Shirokata             5-7 Shiba 5-1, Minato-ku, Tokyo NEC Corporation             Inside the company (72) Inventor Masatomo Yonezawa             5-7 Shiba 5-1, Minato-ku, Tokyo NEC Corporation             Inside the company F-term (reference) 5H011 AA03 BB03 CC10                 5H029 AJ07 AJ12 AK03 AK18 AL06                       AL07 AL12 AM02 AM03 AM05                       AM07 BJ04 CJ08 DJ09 EJ05                       HJ02                 5H050 AA10 AA13 AA15 BA17 CA08                       CA09 CA29 CB07 CB08 CB12                       DA02 DA15 EA12 GA10 HA02

Claims (8)

[Claims] 1. A film-clad non-aqueous electrolyte secondary battery in which a power generation element including at least a positive electrode, a negative electrode, an electrolytic solution, and a separator is packaged with a film, and a lithium-manganese composite oxide having a spinel structure is used for the positive electrode. The electrolytic solution contains a composition capable of reacting with water to generate hydrogen ions,
A film-clad non-aqueous electrolyte secondary battery in which a hydrogen ion scavenger is arranged in a position in contact with the electrolyte in the battery. 2. The lithium-manganese composite oxide having a spinel structure has a [Li] / [Mn] ratio of 0.5 to
The film-coated non-aqueous electrolyte secondary battery according to claim 1, which is LiMn ₂ O ₄ having a thickness of 0.65. 3. The film-covered non-aqueous electrolyte secondary battery according to claim 1, wherein elution of Mn from the lithium-manganese composite oxide is reduced by disposing the hydrogen ion scavenger. . 4. The electrolyte is LiPF ₆ as a supporting salt.
Alternatively, LiBF ₄ is contained therein.
The non-aqueous electrolyte secondary battery having a film exterior according to any one of 1. 5. The film outer packaging according to claim 1, wherein the hydrogen ion scavenger is mixed with a positive electrode or mixed, dissolved or dispersed in an electrolytic solution. Non-aqueous electrolyte secondary battery. 6. The hydrogen ion scavenger is a material that also has a function as a positive electrode active material, and is mixed with the positive electrode together with the lithium-manganese composite oxide having the spinel structure. 5. The film-clad non-aqueous electrolyte secondary battery according to 5. 7. The film-covered non-aqueous electrolyte secondary battery according to claim 6, wherein the hydrogen ion scavenger is a lithium-nickel composite oxide having a hydrogen ion scavenging function. 8. The lithium-nickel composite oxide,
LiNiO ₂ , Li ₂ NiO ₂ , LiNi ₂ O ₄ , Li ₂ Ni
_The non-aqueous electrolyte secondary battery with a film outer package according to claim 7, which is one of ₂ O ₄ and a material obtained by partially doping these with another element.