JPH09139232A - Lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the influence by an oxidized substance or hydrofluoric acid to suppress the elution of a vessel internal metal by providing, within the vessel, a nonaqueous electrolyte formed of at least one electrolyte selected from fluorine compounds and chloride compounds and a nonaqueous solvent, and containing a boron compound in the electrolyte. SOLUTION: An electrode group 3 formed by winding a laminated stripe matter consisting of a positive electrode 4, a separator 5 and a negative electrode 6 is housed in a bottomed cylindrical vessel 1 having an insulator 2 arranged on the bottom part. An insulating sealing plate 8 is fitted to the upper part of the vessel 1 through an insulating paper 7. The positive electrode 4 containing a boron compound is connected to a positive electrode terminal 9 through a lead wire 10, and the negative electrode 6 is connected to the vessel 1 having an acid resisting thermoplastic resin inner surface. The nonaqueous electrolyte in the vessel 1 is formed of at least one electrolyte selected from fluorine compounds and chloride compounds, and a nonaqueous solvent, and a boron compound is contained in the electrolyte. Thus, the influence of an oxidized substance by the action of contained water, particularly, hydrofluoric acid is suppressed to suppress the elution of the vessel internal metal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium battery, and more particularly to a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, non-aqueous electrolyte batteries have attracted attention as high energy density batteries. Among such non-aqueous electrolyte battery using lithium, sodium, light metal such as aluminum as the negative electrode active material, positive electrode active material of manganese dioxide, carbon fluoride [(-CF _{x) n],} was used thionyl chloride Primary batteries have already been widely used as calculators, clock power supplies, and backup batteries for memories.

Furthermore, in recent years, with the miniaturization and weight reduction of various electronic devices such as VTRs and communication devices, the demand for high energy density secondary batteries as their power source has increased, and research on non-aqueous electrolyte secondary batteries has been made. Is actively carried out. For example, LiClO ₄ , LiBF ₄ , LiAs in a non-aqueous solvent such as propylene carbonate, 1,2-dimethoxyethane, γ-butyrolactone or tetrahydrofuran as an electrolytic solution.
A non-aqueous electrolyte secondary battery using a solution in which an electrolyte such as F ₆ or LiPF ₆ is dissolved has been studied. As the positive electrode active material, compounds such as TiS ₂ , MoS ₂ , V ₂ O ₅ , and V ₆ O ₁₃ which undergo a topochemical reaction with lithium have been studied.

However, the secondary battery described above is currently L
Although a material using iCoO ₂ as a positive electrode material has been put into practical use,
Other than that, it has not been put to practical use. The main reason for this is
This is because the charge / discharge efficiency is low and the charge / discharge cycle (cycle) life is short. It is considered that this is largely due to the deterioration of lithium due to the reaction between the positive electrode lithium and the electrolytic solution. That is, lithium dissolved in the electrolytic solution as lithium ions at the time of discharging reacts with the solvent at the time of deposition at the time of charging, and the surface thereof is partially inactivated. For this reason, when charging and discharging are repeated, dendrite-like (dendritic) lithium is generated, deposited into small spheres, and lithium is desorbed from the current collector.

On the other hand, in US Pat. No. 4,668,595 and US Pat. No. 4,702,977, a carbonaceous material which absorbs and releases lithium as a negative electrode incorporated in a non-aqueous electrolyte secondary battery. The use of substances is described. Further, in the above-mentioned U.S. Pat. No. 4,668,595, as the non-aqueous solvent constituting the non-aqueous electrolytic solution, in addition to the above-mentioned non-aqueous solvent, diethoxyethane, ethylene carbonate,
Alternatively, it is described to use a mixture thereof.

However, in a lithium battery made of the above non-aqueous electrolyte, if a small amount of water is present, the electrolyte is decomposed and an acidic substance or the like is generated. As a result, a metal part in contact with the electrolytic solution, such as a container of a lithium battery, is dissolved and corroded, which causes an adverse effect such as inhibiting the action of lithium in the electrolytic solution.

[0007]

DISCLOSURE OF THE INVENTION The present invention suppresses the decomposition of the electrolytic solution due to the water content, prevents the deterioration thereof, and normalizes the action of lithium, whereby the charge / discharge cycle at a high capacity is achieved. It is an object to provide a lithium battery having an improved life.

[0008]

According to a first aspect of the present invention, in a lithium battery having an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, the electrolytic solution contains a boron compound. Has been.

According to the second aspect of the present invention, in a lithium battery having an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, the electrolytic solution contains a dehydrating agent.

According to the third aspect of the present invention, in a lithium battery having an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, the surface inside the container holding the electrolytic solution is resistant to acid thermoplasticity. A lithium battery which is a resin.

According to a fourth aspect of the present invention, in a lithium battery comprising an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, and a positive electrode and a negative electrode immersed in the electrolytic solution, the positive electrode is Contains a boron compound.

According to a fifth aspect of the present invention, in a lithium battery comprising an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, and a positive electrode and a negative electrode immersed in the electrolytic solution, the battery electrode Contains oxygen compounds of rare elements.

With such a structure, it is possible to provide a lithium secondary battery having a high capacity and a long cycle life, which suppresses decomposition and deterioration of the electrolytic solution due to the water content.

Even when the oxygen compound or the boron compound of the rare earth element is added to the material of the negative electrode and not to the material of the positive electrode, a certain effect can be expected. However, from the viewpoint of improving the charge / discharge cycle life, it is still necessary to use these additives in at least the material of the positive electrode. The reason for this is easily understood from the mechanism of action and effect of these additives, as described below.

That is, considering the case where lithium hexafluorophosphate (LiPF ₆ ) is used as the electrolyte, the following reaction first occurs due to the water content.

[0016]

## EQU1 ## LiPF ₆ + H ₂ O → POF ₄ ⁻ + 2HF + Li ⁺ The hydrofluoric acid generated here corrodes the inner surface of the metallic container by the following reaction.

2HF + Fe → FeF ₂ + H ₂ FeF ₂ is ionized as follows and inhibits the charging / discharging function due to the exchange of lithium ions.

[0018] FeF ₂ → Fe ²⁺ + 2F ^- oxygen compounds and boron compounds Mareshi earth elements is hydrofluoric acid produced by the water content, in practice, to react with fluoride ions, for example, produce a BF ₃ and YF ₃ To do. Since these products do not ionize, they do not have the above-mentioned effect of inhibiting the charge / discharge function.

In consideration of the above, it is understood that it is most effective to add the boron compound and the oxygen compound of the rare earth element to the positive electrode in which a large number of anions such as fluorine ions are collected.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A specific example of the lithium battery according to the present invention will be described with reference to FIG.

The bottomed cylindrical container 1 has an insulator 2 arranged at the bottom. The electrode group 3 is housed in the container 1. The electrode group 3 has a structure in which a band-shaped material in which a positive electrode 4, a separator 5, and a negative electrode 6 are laminated in this order is spirally wound so that the negative electrode 6 is located outside. A non-aqueous electrolyte is contained in the container 1. The insulating paper 7 whose center is opened is placed above the electrode group 3 in the container 1. The insulating sealing plate 8 is arranged in the upper opening of the container 1,
In addition, the sealing plate 8 is liquid-tightly fixed to the container 1 by caulking the vicinity of the upper opening inward. The positive electrode terminal 9 is fitted in the center of the insulating sealing plate 8. One end of the positive electrode lead 10 is connected to the positive electrode 4, and the other end is connected to the positive electrode terminal 9. The negative electrode 6 is connected to the container 1 as a negative electrode terminal via a negative electrode lead (not shown).

As the positive electrode 4, those which have been proposed to be used as a positive electrode for a lithium secondary electrode can be used. For example, a substance containing lithium and a chalcogen compound capable of chemically changing topo with lithium as an active material is used. Examples of the chalcogen compound include TiS ₂ , MoS ₂ , V
₂ O ₅ , V ₆ O ₁₃ , CoO ₂ , MnO ₂ , NiO, Nb
Se _3, and the like.

In addition to the above-mentioned active material, it is preferable to use a conductive material made of a carbonaceous material or the like and a binder such as a fluororesin or a polyolefin resin for the positive electrode. It is used according to the purpose in the shape of.
In particular, when it is used in the form of powder, the active material can be formed into an arbitrary shape such as a sheet and used. As a molding method, a method in which an active material is mixed with a powdery binder such as Teflon powder or polyethylene powder and compression molding is performed is general.

For the negative electrode 6, an active material having a function of inserting and extracting lithium is used. As an active material,
Examples include carbonaceous materials. Further, it is preferable to use a binder such as a polyolefin resin or a fluororesin for the negative electrode.

The non-aqueous electrolyte contained in the container 1 is
It is composed of at least one electrolyte selected from a fluorine compound and a chlorine compound and a non-aqueous solvent.

As the electrolyte, lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ),
Fluorine-containing lithium compounds such as lithium arsenic hexafluoride (LiAsF ₆ ), lithium trifluorometasulfonate (LiCF ₃ SO ₃ ), lithium perchlorate (LiCl
O ₄ ), and the like. Among them, fluorine-containing lithium compounds are desirable because they have a property of being difficult to undergo oxidative decomposition during overfilling, and LiPF ₆ is particularly desirable because of high conductivity per mole.

As the non-aqueous solvent, organic propylene carbonate, ethylene carbonate, tetrahydrofuran, γ-butyrolactone, 1,2-dimethoxyethane,
1,2-diethoxyethane or the like is used. For these media, a mixture thereof can be used, and the mixing ratio thereof is arbitrary.

In the lithium battery formed as described above, charging / discharging is performed as follows. First, in the positive electrode, the following reaction is performed. Reaction progresses to the right when charging and to the left when discharging.

[0029]

[Formula 2] LiCoO ₂ ← → Li _1-x CoO ₂ + x
² Li ⁺ + xe ^{− In} addition, the following reaction takes place at the negative electrode. Here, similarly, the reaction progresses to the right when charging and to the left when discharging.

C _n + xLi ⁺ + xe ⁻ ← → C _n Li _{x When} these are combined, the reaction that proceeds in the entire battery is expressed as follows.

[0031]

[Formula 3] LiCoO ₂ + C _n ← → Li _1-x CoO
₂ + C _n Li _{x Although} non-aqueous batteries have been excellent in performance such as high energy density and small size and light weight compared to conventional ones, they have drawbacks in output characteristics as compared with aqueous batteries and have not been widely used. In particular, in the field of secondary batteries where output characteristics are required, this drawback is one of the factors that hinders practical use.

The reason why the non-aqueous battery has inferior output characteristics is that the aqueous electrolyte has a high ionic conductivity, and the non-aqueous battery usually has a low ionic conductivity.

As one method for solving such a problem, increasing the electrode area and forming a thin film or a large area electrode are particularly preferable methods. For that purpose, organic polymers can be used as binders. In this case, a method in which an electrode active material dispersed in a binder solution in which an organic polymer is dissolved in a solvent is used as a coating liquid, a water-emulsion dispersion of an organic polymer dispersed in an electrode active material is used as a coating liquid. Examples thereof include a method of use and a method of applying a solution (dispersion liquid) of the organic polymer to a preformed electrode active material. The amount of binder used is not particularly limited, but is usually in the range of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the electrode active material.

As the organic polymer, acrylonitrile,
Polymers such as methacrylonitrile, vinyl fluoride, vinylidene fluoride, chloroprene and vinylidene chloride, nitrocellulose, cyanoethyl cellulose, and polysulfide rubber can be used. Of course, these organic polymers are representative of those used here and are not particularly limited, but they are not limited to the battery performance, cycle characteristics,
Excellent in terms of overvoltage characteristics.

When this electrode is manufactured, it is molded by coating the coating liquid on a base material and drying it. At this time, it may be formed on the base material together with the current collector material, aluminum foil,
It is also possible to use a collector such as a copper foil as a base material and apply the coating solution thereon and dry it.

The present invention is characterized in that the electrolyte and the non-aqueous solvent further contain a boron compound in the non-aqueous electrolytic solution.

It is essential that the boron compound is a boron compound that does not function as an electrolyte in a lithium battery, that is, a boron compound that does not contain fluorine or chlorine and lithium, such as B ₂ O ₃ and H _3.
BO ₃ , (CH ₃ O) ₃ B, (C ₂ H ₅ O) ₃ B, (C
_{H 3 O) 3 B-B} 2 O 3 or the like can be used. Among them, B ₂ O ₃ is particularly desirable.

The boron compound is used in such an amount that the concentration in the electrolytic solution does not exceed 10% by weight as elemental boron, and the amount used is 0.1 to 7% by weight, particularly 0.5 to 5% by weight. Is desirable.

By including the above-mentioned boron compound in the electrolytic solution, it is possible to greatly reduce the amount of acidic substances generated by the water content in the electrolytic solution, which is caused by deterioration of the electrolytic solution and corrosion of the battery container. As a result, it is possible to prevent a decrease in the activity of the negative electrode due to the metal ions.

Examples of the dehydrating agent further contained in the electrolytic solution include activated alumina, zeolite, sodium sulfate, activated carbon, silica gel, magnesium oxide, calcium oxide and the like. The addition amount of these dehydrating agents is usually 20% by weight or less in the electrolytic solution, 2 to 15% by weight, particularly 5 to 10% by weight.
% By weight is preferred. It is desirable that these dehydrating agents be sufficiently dried by a method such as heat treatment before being added to the electrolytic solution.

By including these dehydrating agents, the decomposition of the electrolyte by water is prevented, and the deterioration of the electrolytic solution is prevented.
Generation of acidic substances can be suppressed. Further, the suppression of the generation of the acidic substance prevents an increase in the pressure inside the battery container, thereby making it possible to make the outer wall of the battery thin and reduce the weight of the battery.

Further, the present invention is characterized in that the oxygen compound of the rare earth element is contained in the battery electrode.

The above-mentioned binder, conductive auxiliary agent, and other additives such as a tackifier, a dispersant, a filler, and an adhesion auxiliary agent may be added to the battery electrode containing the oxygen compound of a rare earth element. , Containing at least one oxygen compound of the rare earth element of the present invention. Examples of the conductive auxiliary agent include metal powder, conductive metal oxide powder, carbon and the like.

It is important that the compound of these additive elements is a compound that does not function as an electrolyte and a carrier material in a lithium battery, that is, a compound that does not contain fluorine, chlorine and lithium. For example, Y ₂ O ₃ ,
La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Nd ₂ O ₃ , P
m ₂ O ₃ , Sm ₂ O ₃ , Fu ₂ O ₃ , Gd ₂ O ₃ and Tb
₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂
Typical examples are O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ , Sc ₂ O _{3 and the} like.

The compound content of the rare earth element is preferably such that the rare earth element content is not less than 0.1% by weight and not more than 2% by weight. The amount of electrolyte applied in the electrode material is 300 to 500 μg / cm ² , preferably 250 to
It is preferably 400 μg / cm ² . here,
The electrolytic solution coating amount is the amount of the electrolytic solution existing on the electrode surface when the electrode is immersed in the electrolytic solution and then pulled up.

By adding the rare earth compound to the electrode material and controlling the amount of the electrolytic solution applied in the electrode material, the amount of acidic substances produced by the water content in the electrode and the electrolytic solution can be greatly reduced. This is due to corrosion of the current collector of the electrode, deterioration of the carrier material, deterioration of the electrolytic solution, deterioration of the electrolyte, deterioration of the negative electrode activity and deterioration of the positive electrode oxidation number due to metal ions, etc. that constitute the container due to corrosion of the battery container, This brings about a result of preventing or suppressing a decrease in adhesion between the electrode coating film and the current collector.

Furthermore, the present invention is characterized in that the battery compound contains a boron compound.

It is essential that the boron compound is a boron compound which does not function as an electrolyte and a carrier material in a lithium battery, that is, a boron compound which does not contain fluorine or chlorine and lithium, for example, B ₂ O ₃ , H ₃ BO ₃ , (CH ₃ O) ₃ B, (C ₂ H ₅
O) ₃ B-B ₂ O ₃ , etc. can be used. Among them, B ₂ O ₃ is particularly desirable.

The content of the boron compound is not more than 10% by weight as elemental boron, and the amount used is 0.5 to 7% by weight, particularly 0.5 to 5% by weight. Is desirable.

By including the above-mentioned boron compound in the electrode material, it is possible to greatly reduce the acidic substances produced by the water content in the electrode and the electrolytic solution, which is caused by the corrosion of the electrode current collector and the carrier material. Deterioration, deterioration of electrolyte solution, deterioration of electrolyte, deterioration of negative electrode activity due to metal ions etc. constituting the container due to corrosion of battery container, decrease in oxidation number of positive electrode, decrease in adhesion between electrode coating film and current collector, etc. Bring

Further, the present invention is characterized in that at least a part of the inner surface of the battery container is an acid resistant thermoplastic resin. The portion in contact with the electrolytic solution is typically the inner wall of the battery container. The inner wall is made of stainless steel, for example.

Examples of the acid-resistant thermoplastic resin include fluorine resin, polyolefin resin, polyvinyl chloride resin, acrylonitrile-butadiene-styrene copolymer resin, polyester resin and the like. You may use 2 or more types of these.

As the fluororesin, polytetrafluoroethylene (PFTE), polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-propylene copolymer (FEP),
Examples thereof include polyvinylidene fluoride (PVDF), perfluoroalkoxyfluorinated plastic (PFA), and tetrafluoroethyne-hexachloroethylene copolymer.

Examples of the polyolefin resin include high density polyethylene (HDPE), polypropylene (PP), propylene-ethylene copolymer, polybutene-1, polymethylpentene-1 and the like. Examples of the polyester resin include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).

Among the above acid-resistant thermoplastic resins, fluororesins are particularly preferable. When covering the portion in contact with the electrolytic solution with the thermoplastic resin, the thickness of the coating layer is usually 100.
Å to 200 μm.

By covering the battery portion other than the electrodes, which is in contact with the electrolytic solution, with the above-mentioned thermoplastic resin, the contact portion can be protected from the acidic substance generated by the decomposition of the electrolyte due to the water content. When the contact portion is made of stainless steel, it prevents the generation of ions of nickel, chromium, iron, etc., which are the constituent metals of the contact portion, and the transfer to the electrolytic solution, and the formation of a carbonaceous substance as the active material of the negative electrode. Since the amount of occlusion / release of lithium ions can be improved, the deterioration of the structure of the negative electrode can be suppressed, and the deterioration of the non-aqueous electrolyte can be suppressed, a lithium secondary battery having a high capacity and a long cycle life can be obtained.

In the present invention, the electrolytic solution contains a boron compound (Requirement 1), the electrode material contains an oxygen compound of a rare earth element (Requirement 2), and the electrode material contains a boron compound (Requirement 2). Requirement 3), the electrolytic solution contains a dehydrating agent (Requirement 4), and the portions other than the electrodes that come into contact with the electrolytic solution are covered with the thermoplastic resin (Requirement 5),
The present invention can be naturally adopted not only in each of those requirements alone, but also in any combination of each requirement, and in the case of each of these combinations, than in the case of each of these requirements alone,
It is clear from the description of the examples below that the positive effects are exhibited.

Hereinafter, the present invention will be described in detail by carrying out.

(Example 1) Lithium cobalt oxide (L
iCoO ₂ ) powder 80% by weight, acetylene black 15
%, And 5% by weight of polytetrafluoroethylene powder were mixed and then made into a sheet. Next, this sheet was laminated with a current collector made of aluminum foil to prepare a sheet-shaped positive electrode.

98% by weight of carbonaceous material powder obtained by firing phenol resin powder in nitrogen gas at 1700 ° C. for 2 hours and 2% by weight of ethylene-propylene copolymer.
Was mixed and laminated with a current collector made of nickel foil to prepare a negative electrode.

The positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located on the outer side to manufacture an electrode group.

Furthermore, LiP was added to 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane (mixing volume ratio 40:40:20).
After 1.0 mol of F ₆ was dissolved, boron oxide (B ₂ was added so that the concentration in the electrolytic solution was 0.8% by weight as a boron element.
O ₃ ) was added to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

Example 2 In Example 1, B ₂ O ₃
The content of magnesium oxide is 5% by weight instead of
An electrolytic solution was prepared in the same manner as in Example 1 except that the above was added so that a lithium battery was assembled using this electrolytic solution.

Example 3 An electrolytic solution was prepared in the same manner as in Example 1 except that magnesium oxide was further added so that the content thereof was 5% by weight.
Furthermore, a lithium battery was assembled using this electrolytic solution.

Comparative Example 1 An electrolytic solution was prepared in the same manner as in Example 1 except that boron oxide was not used, and a lithium battery was assembled using this electrolytic solution.

The lithium batteries assembled in Examples 1 to 3 and Comparative Example 1 were left for 3 hours to 35 days, respectively,
The electrolytic solution was decomposed with a hot aqueous sodium hydroxide solution, diluted with methanol, and then the fluorine ion concentration was measured by an ion chromatography method. Table 1 shows the results.

From these results, it is understood that in the electrolytic solution to which the boron compound and / or the dehydrating agent is added, the production of fluorine ions is suppressed, and the amount is greatly decreased with the passage of time. In particular, the addition of both the boron compound and the dehydrating agent increases the degree of reduction.

[0069]

[Table 1] Example 4 The lithium battery was assembled by housing the electrode group manufactured in Example 1 and the electrolytic solution prepared in Comparative Example 1 in a bottomed cylindrical container made of stainless steel. In particular, here, as shown in FIG. 2, the inner wall of the bottomed cylindrical container 1 is coated with polytetrafluoroethylene (PTFE) to a thickness of 100 μm to protect the inner wall of the acid-resistant thermoplastic resin.
Was provided.

Example 5 A lithium battery was assembled in the same manner as in Example 4 except that the electrolytic solution prepared in Example 3 was used instead of the electrolytic solution prepared in Comparative Example 1.

The lithium batteries assembled in Example 4, Example 5 and Comparative Example 1 were each discharged at 400 mA for 10 hours, and then the carbonaceous negative electrode powder was taken out and extracted with aqua regia, and the extract was subjected to ICP (induction). Contaminant metal content was measured by combined plasma) emission spectrometry. As a result, Table 2
Shown in

From these results, it is understood that by covering the inner wall of the battery container with PTFE, the metal constituting the container is not eluted into the electrolytic solution and is not contained in the negative electrode. Then, when an electrolytic solution containing a boron compound and a dehydrating agent is used, the effect becomes more remarkable.

[0073]

[Table 2] Further, the lithium batteries assembled in Examples 1 to 3 and Comparative Example 1 were charged up to 4.2 V at a current of 50 mA, and 5
After repeating the charge / discharge cycle of discharging to 2.7 V at a current of 0 mA, the discharge capacity and cycle life of each battery were measured.

The results are shown in FIG.

As is clear from FIG. 3, the batteries assembled in the respective examples have a longer cycle life than the batteries assembled in the comparative example.

Example 6 1.05 mol of lithium carbonate,
1.90 mol of cobalt oxide and 0.084 mol of stannic oxide are mixed in a mortar, calcined at 650 ° C. for 5 hours, and then calcined in air at 850 ° C. for 12 hours. Then, the obtained lithium cobalt oxide having the composition Li _1.03 CoSnO ₂ is ball-milled to prepare a powder having an average particle diameter of 3 μm.
80% by weight of the lithium cobalt oxide powder thus obtained was mixed with 15% by weight of acetylene black and 5% by weight of polytetrafluoroethylene powder, and the mixture was kneaded with isopropyl alcohol to form a paste, and the current was collected. The sheet-shaped positive electrode was produced by applying it to a body aluminum foil, drying it, and performing roll pressing.

On the other hand, 96% by weight of carbonaceous material powder having an average particle diameter of 3 μm and 2% by weight of polytetrafluoroethylene powder obtained by firing the phenol resin powder in nitrogen gas at 1700 ° C. for 2 hours and then ball-milling. % And yttrium oxide 2% by weight was kneaded with isoprohill alcohol, applied to a copper foil serving as a current collector, dried, and roll pressed to produce a sheet-shaped negative electrode.

The positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside, to produce an electrode group.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane (mixing volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolytic solution were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolytic solution lithium secondary battery shown in FIG.

Example 7 80% by weight of lithium cobalt oxide powder prepared by the method described in Example 6 was mixed with 13% by weight of acetylene black, 5% by weight of polytetrafluoroethylene powder and 2% by weight of yttrium oxide. The mixture was mixed and kneaded with isopropyl alcohol to form a paste, which was applied to an aluminum foil serving as a current collector, dried, and roll-pressed to produce a sheet-shaped positive electrode.

Similarly, a mixture of 96% by weight of carbonaceous material powder prepared by the method of Example 6 and 4% by weight of polytetrafluoroethylene powder was kneaded with isopropyl alcohol to form a copper foil as a current collector. A sheet-shaped negative electrode was prepared by applying, drying and roll pressing.

The positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located on the outer side to manufacture an electrode group.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2 dimethoxyethane (mixing volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

Example 8 A negative electrode was produced by the method of Example 6 and a positive electrode was produced by the method of Example 7. Then, as in Example 6 and Example 7, the positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside. An electrode group was manufactured.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2 dimethoxyethane (mixing volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

Comparative Example 2 A positive electrode was manufactured by the method of Example 6 and a negative electrode was manufactured by the method of Example 7. That is, yttrium oxide is not used. Then, as in Example 6 and Example 7, the positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside. An electrode group was manufactured.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2 dimethoxyethane (mixing volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

(Comparative Example 3) An electrode group was prepared by the method of Example 6. Then, after dissolving 2.0 mol of lithium hexafluorophosphate in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane (mixing volume ratio 40:40:20), HF was further dissolved in the solvent. A non-aqueous electrolytic solution was prepared by adding it so as to be 1.0 mol.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

The lithium batteries assembled in Examples 6, 7, and 8 and Comparative Examples 2 and 3 were charged and discharged by charging each with a current of 50 mV to 4.2 V and discharging with a current of 50 mV to 2.7 V. After repeating the cycle 500 times, the negative electrode and the positive electrode are separated, methanol is added to each, water is further added, and the mixture is heated at 100 ° C. for 2 hours and then cooled to room temperature. Further, a hot water soluble component and an insoluble component were separated by a filter.

Regarding the hot water-soluble component, F was quantified by an ion chromatographic method for both the negative electrode and the positive electrode, and Co was quantified only for the positive electrode by ICP (inductively coupled plasma) emission spectrometry.

Regarding the insoluble component, the negative electrode was extracted with aqua regia and Al, Cu, Cr, Fe, Ni and Co were extracted, and the positive electrode was decomposed with nitric acid and then Al, Cu, Cr, Fe and Ni were added to I.
The amount of contaminant metals was quantified by CP emission spectrometry. Table 3 shows the metal contamination amount and the hot water-soluble component quantification result of the negative electrode, and Table 4 shows the metal contamination amount and the hot water-soluble component quantification result of the positive electrode.

[0097]

[Table 3]

[Table 4] From these results, it is understood that the negative electrode and the positive electrode to which the rare compound is added have the metal elution and the generation of fluorine ions in the electrolytic solution suppressed, and do not increase with the passage of time.
Also, similar results were obtained when the concentration of LiPF _{6 in} the solvent was appropriate.

Further, Examples 6, 7 and 8 and Comparative Examples 2 and 3
After repeating the charge-discharge cycle of charging the lithium battery assembled in (1) to 4.2 V at a current of 50 mA and discharging it to 2.7 V at a current of 50 mA, the discharge capacity and cycle life of each battery were measured. FIG. 4 shows the results.

As is clear from FIG. 4, the battery assembled in the example has a longer cycle life than the battery assembled in the comparative example.

Example 9 1.05 mol of lithium carbonate,
1.90 mol of cobalt oxide and 0.084 mol of stannic oxide are mixed in a mortar, calcined at 650 ° C. for 5 hours, and then calcined in air at 850 ° C. for 12 hours. Then, the obtained lithium cobalt oxide having the composition Li _1.03 CoSnO ₂ is ball-milled to prepare a powder having an average particle diameter of 3 μm.
80% by weight of the lithium cobalt oxide powder thus obtained was mixed with 15% by weight of acetylene black and 5% by weight of polytetrafluoroethylene powder and kneaded with isopropyl alcohol to form a paste, The sheet-shaped positive electrode was produced by applying it to a body aluminum foil, drying it, and performing roll pressing.

On the other hand, 96% by weight of carbonaceous material powder having an average particle diameter of 3 μm and 2% by weight of polytetrafluoroethylene powder obtained by firing the phenol resin powder in nitrogen gas at 1700 ° C. for 2 hours and then ball-milling. % Of boron oxide and 2% by weight of boron oxide were kneaded with isopropyl alcohol, applied on a copper foil serving as a current collector, dried, and roll-pressed to produce a sheet-shaped negative electrode.

The positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was positioned on the outer side to manufacture an electrode group.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane (mixing volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

(Example 10) Lithium carbonate 1.05 mol, cobalt oxide 1.90 mol, and stannic oxide 0.08 mol.
4 mol is mixed in a mortar, calcined at 650 ° C. for 5 hours, and then calcined in air at 850 ° C. for 12 hours. Then, the obtained lithium cobalt oxide having the composition Li _1.03 CoSnO ₂ is ball-milled to prepare a powder having an average particle diameter of 3 μm. 80 wt% of the lithium cobalt oxide powder thus obtained was mixed with 13 wt% of acetylene black, 5 wt% of polytetrafluoroethylene powder and 2 wt% of boron oxide, and kneaded with isopropyl alcohol. A sheet-shaped positive electrode was prepared by forming a paste, applying it to an aluminum foil serving as a current collector, drying it, and performing roll pressing.

On the other hand, 96% by weight of carbonaceous material powder having an average particle size of 3 μm and 4% by weight of polytetrafluoroethylene powder obtained by firing the phenol resin powder in nitrogen gas at 1700 ° C. for 2 hours and then ball-milling. % Of the mixture was kneaded with isopropyl alcohol, applied to a copper foil serving as a current collector, dried, and roll-pressed to produce a sheet-shaped negative electrode.

The positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located on the outer side to manufacture an electrode group.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2 dimethoxyethane (mixing volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

(Example 11) A negative electrode was manufactured by the method of Example 9 and a positive electrode was manufactured by the method of Example 10. Then, as in Example 9 and Example 10, the positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside. An electrode group was manufactured.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane (mixing volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

Comparative Example 4 A positive electrode was manufactured by the method of Example 9 and a negative electrode was manufactured by the method of Example 10. That is, boron oxide or rare earth oxide is not used. Then, as in Example 9 and Example 10, the positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside. An electrode group was manufactured.

Further, 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in 1 liter of a mixed solvent of ethylene carbonate, propylene carbonate and 1,2 dimethoxyethane (mixed volume ratio 40:40:20). Further, HF was further added so as to be 1.0 mol in the solvent to prepare a non-aqueous electrolytic solution.

The electrode group and the non-aqueous electrolyte were housed in a stainless steel bottomed cylindrical container to assemble the non-aqueous electrolyte lithium secondary battery shown in FIG.

The lithium batteries assembled in Examples 9 to 11 and Comparative Example 4 were allowed to stand for 1 hour to 5 days, and
The carbonaceous negative electrode powder was taken out and extracted with aqua regia, and the amount of contaminating metal was measured by ICP emission spectrometry. Further, the electrolytic solution from which the electrodes were removed was decomposed with a hot sodium hydroxide aqueous solution, diluted with methanol, and then the fluorine ion concentration was measured by an ion chromatography method. Table 5 shows the results.

[0117]

[Table 5] Further, the lithium batteries assembled in Examples 9 to 11 and Comparative Example 4 were each left for 1 hour to 5 days, and then LiC was added.
The positive electrode containing oO ₂ was taken out, and after decomposing nitric acid, the amount of contaminating metal was measured by ICP emission spectrometry. Table 5 shows the results.

From these results, it is understood that the negative electrode and the positive electrode to which boron is added suppress the elution of metal and the production of fluorine ions in the electrolytic solution, and do not increase with the passage of time.

Further, the lithium batteries assembled in Examples 9, 10, 11 and Comparative Example 4 were tested at a current of 50 mA.
After repeating the charge / discharge cycle of charging to 2 V and discharging to 2.7 V at a current of 50 mA, the discharge capacity and cycle life of each battery were measured. The result is shown in FIG.
Shown in

As is apparent from FIG. 5, the battery assembled in the example has a longer cycle life than the battery assembled in the comparative example.

[0121]

INDUSTRIAL APPLICABILITY The present invention suppresses the influence of an oxidizing substance generated by the action of contained water, particularly hydrofluoric acid, by containing a boron compound and an oxygen compound of a rare earth element in the battery electrode and the battery electrode. In addition, since the electrolytic solution contains a dehydrating agent, various adverse effects due to the contained water can be eliminated, and by coating and protecting the inner wall of the battery container, the elution of metal in the container can be suppressed.

Further, along with these improvements, the cycle life can be greatly extended with a high capacity without deteriorating the characteristics of the lithium battery.

[Brief description of the drawings]

FIG. 1 is a partially sectional front view of a lithium battery according to the present invention.

FIG. 2 is a partially sectional front view of another lithium battery according to the present invention.

FIG. 3 is a characteristic diagram showing the relationship between the charge / discharge cycle and the charge capacity of the lithium battery according to the present invention.

FIG. 4 is a characteristic diagram showing a relationship between a charge / discharge cycle and a charge capacity of another example of the lithium battery according to the present invention.

FIG. 5 is a characteristic diagram showing a relationship between charge and discharge cycles and charge capacity of still another example of the lithium battery according to the present invention.

[Explanation of symbols]

 1 Container 3 Electrode Group 4 Positive Electrode 5 Separator 6 Negative Electrode 8 Sealing Plate 9 Positive Electrode Terminal 11 Inner Wall Protection Film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsu Hayashi 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Stock R & D Center, Toshiba Corporation (72) Inventor Motoo Yabuki Toshiba, Komukai-shi, Kawasaki-shi, Kanagawa Machi 1 Co., Ltd., Toshiba Research and Development Center (72) Inventor Hiroshi Endo Komukai, Kouki-ku, Kawasaki-shi, Kanagawa 1 Toshiba-cho, Toshiba Research Consulting Co., Ltd. Muko Toshiba Town 1 Co., Ltd. Toshiba Research and Development Center (72) Inventor Tomoka Matsumoto Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture 1 Kobayashi Toshiba Research and Development Center (72) Inventor Hideyuki Sasaki Kawasaki City, Kanagawa Prefecture Komukai Toshiba-cho 1 Ward Stock Company Toshiba Research and Development Center

Claims (4)

[Claims] 1. A lithium battery having an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, wherein the electrolytic solution contains a boron compound. 2. A lithium battery having an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, wherein the electrolytic solution contains a dehydrating agent. 3. A lithium battery having an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound in a container, wherein the container inner surface is an acid resistant thermoplastic resin. 4. A lithium battery comprising an electrolytic solution containing at least one selected from a fluorine compound and a chlorine compound, and a positive electrode and a negative electrode immersed in the electrolytic solution, wherein the positive electrode contains a boron compound. Lithium battery.