JPH09219219A - Manufacture of lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assemble a lithium secondary battery in a well-workable manner by assembling a negative electrode formed of Li-carried carbon based material stable in the air and a positive electrode formed of positive electrode active material not containing Li in the air. SOLUTION: A positive electrode formed of positive electrode active material not containing Li related to charge and discharge and a negative electrode formed of Li-carried carbon based material stable in the air in a Li-carried state are used to assemble a battery cell in the air. The positive electrode active material is formed by firing V2 O5 , CoCO3 , etc., at 100-500 deg.C. The carbon based material is formed by firing organic polymeric compound such as polyphenine, poly(p-phenylene vinylene), poly(p-phenylene xylene), etc. By using the positive electrode and the negative electrode to assemble the battery cell in the air, a lithium secondary battery is provided in a well-workable manner without requiring large facilities including an inactive atmosphere.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a lithium secondary battery using a carbonaceous material as a negative electrode.

[0002]

2. Description of the Related Art In recent years, miniaturization of electronic devices has progressed, and along with this, there has been a demand for higher energy densities of batteries. In response to this, lithium carbon intercalation compounds can be electrochemically easily formed and charged. A battery has been proposed in which a carbonaceous material having a large discharge capacity and excellent cycle stability is used as a negative electrode. As such a battery, for example, LiCoO ₂ , L
There is a rocking-chair type battery that uses iNiO ₂ , LiMn ₂ O ₄ or a lithium-containing transition metal oxide that is a mixture thereof as a positive electrode. In this battery, since lithium, which is an active material, exists in the positive electrode, it can be used by assembling it with the negative electrode carbon and then charging it. However, in such a positive electrode, there is a problem that the energy density is inferior because the lithium ion supply source is limited to the positive electrode.

Therefore, a battery has been proposed in which a positive electrode that does not contain lithium as an active material is combined with a carbon negative electrode supporting lithium. But with such a battery,
Since it lacks stability after supporting lithium on the negative electrode,
There is a problem in that large-scale equipment with an inert atmosphere is required for assembling the battery, and the work becomes complicated.

[0004]

The present invention has been made against the background of the problems of the prior art as described above, and it is possible to assemble in the atmosphere even in the state that lithium is supported, and a large-scale assembly facility is required. It is an object of the present invention to provide a method for assembling a lithium secondary battery which is excellent in workability.

[0005]

The present invention is a method for producing a lithium secondary battery comprising a negative electrode made of a carbonaceous material and a positive electrode made of a positive electrode active material containing no lithium involved in charging and discharging. The present invention provides a method for manufacturing a lithium secondary battery, which comprises supporting lithium on a carbonaceous material of a negative electrode that is stable in the air while supporting lithium, and then assembling battery cells in the air. .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the production method of the present invention, the negative electrode is made of a carbonaceous material that is stable in the atmosphere while supporting lithium, and the positive electrode is made of a positive electrode active material that does not contain lithium involved in charging and discharging. It is applied to lithium secondary batteries.

The carbonaceous material which is stable in the air in the state of supporting lithium as used herein means that the reaction with water or the like is sufficiently mild even in the charged state, that is, in the state of supporting lithium. Examples of such a carbonaceous material include a carbonaceous material having a condensed aromatic structure and having a disordered laminated structure. The disordered laminated structure refers to a structure in which the orientation of the condensed aromatic ring plane is completely disordered or does not have an orientation of more than four, preferably more than three. Having a condensed aromatic structure and having a disordered laminated carbonaceous material that is stable in the atmosphere even when lithium is supported not only intercalates lithium ions between layers but also has a covalent bond. It is considered that this is because the lithium metal and lithium ions that it has are occluded between carbon-carbon atoms.

Further, by using such a carbonaceous material as a material for an electrode, the structural stability of the material due to adsorption / desorption is small, the lithium absorption amount is large, and the adsorption / desorption reaction rate is high. And a lithium secondary battery having a high energy density can be obtained.

The carbonaceous material having a condensed aromatic structure and having a disordered laminated structure can be obtained by firing an organic polymer compound having a factor that inhibits the laminated structure of the carbonaceous material. Examples of the organic polymer compound having a factor that inhibits stacking include a bent structure containing an o-bond or an m-bond,
It is an organic polymer compound having an aromatic structure containing at least one structure selected from the group of a branched structure and a crosslinked structure, and may contain an organic compound having a 5-membered ring or a 7-membered ring. As such an organic polymer compound, a non-heterocyclic polymer having a developed conjugated polymer structure, that is, polyphenylene, poly (p-phenylene vinylene) (PPV), poly (p-phenylene xylene) (PPX), polystyrene , Novolac resins and the like.

Among these organic polymer compounds, those having low crystallinity are preferable, and 2θ of X-ray diffraction =
The full width at half maximum of the diffraction peak near 20 ° is preferably 0.75
It is desirable that the angle be at least 0 °, more preferably at least 0.95 °. Furthermore, the organic polymer compound preferably contains a quinoid structure. Here, the inclusion of the quinoid structure can be confirmed by observing the absorption edge in the range of 600 to 900 nm in the diffuse reflection spectrum of the powder of the organic polymer compound.

Preferred as such an organic polymer compound is polyphenylene having a high degree of polymerization to some extent. The carbonaceous material obtained by firing such polyphenylene is an amorphous carbon having a condensed aromatic structure and a disordered laminated structure, which is excellent in large-current property. In the present invention, the R value defined by the following formula is applied as a measure of the degree of polymerization of polyphenylene. Among them, the R value is preferably 2 or more, more preferably 2.3 to 20. R = A [δ (para)] / {A [δ (mono1)]
+ A [δ (mono2)]} where A [δ (para)] is the absorbance of the absorption band in the C—H out-of-plane bending vibration mode near 804 cm ⁻¹ in the infrared absorption spectrum, A [δ (mono1) ], A
[Δ (mono2)] is around 760 cm ^-1 , 6 respectively
The absorbance of the absorption band of the terminal phenyl group near 90 cm ^-1 is shown.

Various methods are known as methods for synthesizing polyphenylene. For example, a method of obtaining polyphenylene by polymerizing benzene under mild reaction conditions using various combinations of Lewis acid catalysts and oxidizing agents (P. Koacic;
A. Kyriakis; Am. Chem. Soc.
85, 454～458,1963) (hereinafter referred to as "Kobachikku Act"), poly (1,3-cyclohexadiene)
To obtain polyphenylene by dehydrogenating (J. Am. Chem. Soc. 81 , 448-45).
2, 1959), a dehalogenation polymerization of dihalobenzenes using a nickel catalyst, Yamamoto method (T. Yamamot).
o; A. Yamamoto; Chemistry Le
tters, 353-356, 1977) and the like.
In the case of the above Kobatik method, as a catalyst,
Using an aluminum chloride-cupric chloride system, at 35 ° C,
Polyphenylene can be obtained in high yield in about 30 minutes.

In the present invention, the method for synthesizing polyphenylene is not particularly limited, but the cobatic method is preferable because of its low production cost and excellent carbonization yield due to partial crosslinking. According to the Kobatik method,
The fact that polyphenylene having a condensed ring structure can be obtained is
R (G. Froyer et al., Polymer
r, 23 , 1103, 1982), and mass spectrometry (CE Brown et al., J. Polyme.
r Science, Polym. Chem. Ed. ,
24 , 255, 1986).

The firing of the organic polymer compound is carried out at a temperature near the carbonization temperature, that is, from the carbonization temperature to the carbonization temperature + 300 ° C.
It is preferable to carry out at a temperature within the range of about. The carbonization temperature is a temperature at which hydrogen or the like is desorbed from an organic polymer compound as a starting material and can be measured by TG (thermogravimetric measurement) or DTA (differential thermal analysis). When the organic polymer compound is polyphenylene, the preferable firing temperature is 500 to 1,000 ° C., particularly 600 to 80.
0 ° C. is more preferred. When fired in this range, a carbonaceous material in which a carbon component and an organic component are mixed without being completely carbonized. However, if the firing temperature is lower than 500 ° C, the carbonization becomes insufficient, while if it exceeds 1,000 ° C, the carbonization proceeds too much and the organic component does not remain.

In the carbonaceous material, the mixture of the carbon component and the organic component is important for obtaining a negative electrode excellent in cycle stability. This is because if the carbon component and the organic component are mixed in the carbonaceous material, structural collapse is unlikely to occur even if the volume changes due to the charge / discharge reaction.
In the carbonaceous material, the carbon component is preferably 80 to 99% by weight, more preferably 90 to 99% by weight. The organic component is preferably 1 to 20% by weight, and particularly 1 to 20% by weight.
About 10% by weight is more preferable. The carbon component here is the amount of carbon by elemental analysis. The organic component is the amount of elements such as hydrogen, nitrogen, sulfur, oxygen, etc. excluding carbon contained in the starting materials.

Hydrogen / carbon atomic ratio (H / C) of carbonaceous material
Is preferably 0.05 to 0.6, particularly 0.15 to 0.
6 is more preferable. If it is less than 0.05, the graphite structure will develop, and the crystal structure will be destroyed by the expansion and contraction of the crystal during the lithium doping / de-doping reaction during charge / discharge, and the cycle stability will decrease, while if it exceeds 0.6, The discharge capacity may decrease significantly.

As a specific firing method, any heating rate may be used up to the weight reduction start temperature of the organic compound as a raw material, but 5 ° C./hour to 200 ° C./hour from the weight reduction start temperature to the firing temperature. , Preferably 20 ° C / hour to 100
It is preferable to raise the temperature at a temperature raising rate of ° C / hour. The firing atmosphere of the organic polymer compound may be an inert atmosphere or a reducing atmosphere, and examples thereof include nitrogen, argon and hydrogen atmospheres. The firing time is preferably 0 to 6 hours.
Here, the firing time is the time after the set temperature is reached.

The carbonaceous material obtained by firing in this manner is usually powder or solid, and when used as a negative electrode material, this carbonaceous material is mechanically crushed before use.
The particle size in this case is not necessarily limited, but a high-performance negative electrode can be obtained by setting the average particle size to 5 μm or less. The negative electrode body is obtained by adding and mixing a binder to these carbonaceous material powders and rolling them with a roll. The binder content is 5 to 50 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the electrode material.

Here, as the binder, both organic and inorganic binders can be used. As the organic binder, in addition to the poly (ethylene), many binders such as fluoro resins such as polytetrafluoroethylene and polyvinylidene fluoride, polyvinyl alcohol, polyvinyl chloride and the like can be used. In this case, except for polyethylene, after mixing with the binder, a heat treatment near the carbonization temperature of the binder is required. Further, as the inorganic binder, a silicon-based binder such as silicon glass can be used, but in this case as well, heat treatment at a temperature exceeding the melting point is necessary in order to exert the performance as a binder.

The method for producing the negative electrode body is not limited to the above-described method, and for example, the organic polymer compound as a starting material is mixed with a binder and molded to obtain a negative electrode body directly. Alternatively, as described below, the carbonaceous material obtained by firing may be further mixed with organic fibers to obtain a negative electrode body.

As the organic fiber mixed with the carbonaceous material,
Examples thereof include cellulose fibers, rayon fibers, pitch fibers, lignin fibers, phenol resin fibers, acrylic resin fibers, and the like, and among them, cellulose fibers having good dispersibility in water and excellent in cost are preferable. The shape of the organic fiber is not particularly limited, and various shapes such as chopped yarn, strand, and wavy shape can be used. Such an organic fiber not only serves as a support when the carbonaceous material is formed into a film or sheet, but also has a function of giving the film or sheet a certain thickness. Further, the length of the organic fiber is preferably 0.2 to 10 mm, particularly preferably 0.2 to 2 mm. If the length of the organic fiber is less than 0.2 mm, the bulkiness of the organic fiber is not exhibited, while if it exceeds 10 mm,
Moldability may be reduced.

It is preferable that the organic fiber is well dried before use. Furthermore, by subjecting the organic fiber to heat treatment in advance, the organic fiber is given shrinkage, and shrinkage during subsequent heating can be reduced. The heating temperature needs to be a temperature that does not impair the strength of the organic fiber, and is preferably in the range of 120 to 250 ° C.

The papermaking method is most preferable as the method for forming the carbonaceous material and the organic fiber into a film or sheet. The papermaking method is a method in which a turbid liquid of a carbonaceous material and organic fibers and an organic solvent is prepared, spread to a predetermined thickness, and then the organic solvent is evaporated to form a film or sheet.

The mixing ratio of the organic fibers to the carbonaceous material is preferably 10 to 70% by weight, particularly preferably 15 to 40% by weight. If the organic fiber content is less than 10% by weight, the moldability may decrease, while if it exceeds 70% by weight, the discharge capacity as an electrode may decrease.

In making paper, first, a carbonaceous material and organic fibers are mixed in a solvent to form a suspension. The solvent used at this time can be appropriately selected, but when cellulose fibers are used as the organic fibers, water, ethanol, or a mixture of water and ethanol is preferable.

The total ratio of the carbonaceous material and the organic fibers in the suspension is preferably 1 to 5% by weight, particularly 1.7 to 3.3% by weight. If the proportion is less than 1% by weight, it is difficult to homogenize the suspension. On the other hand, if it exceeds 5% by weight, the viscosity becomes too high, which may make it difficult to make a paper with a uniform thickness when forming a film or sheet. Any device may be used for mixing the carbonaceous material, the organic fiber and the organic solvent, but it is preferable to use a ball mill or a mixer.

At this time, if necessary, the organic solvent may contain
Surfactants, paper strength agents or binders may be added. Examples of the surfactant include polyoxyethylene phenyl ether, polyoxyoctyl phenyl ether, ethanol and methanol. As the paper-strengthening agent, cationic starch, cationic or anionic polyacrylic amide, melamine resin, urea resin,
In addition to epoxidized amide, carboxy-modified polyvinyl alcohol, etc., synthetic resin emulsions can be mentioned.
Examples of the binder include vinyl chloride fiber and rayon for papermaking.

The film or sheet thus obtained is subjected to a drying treatment at 50 to 80 ° C. to evaporate the solvent (hereinafter, the film or sheet after the drying treatment is referred to as “fiber film or sheet”). The thickness of the fiber film or sheet is preferably 0.05 to 1 mm, particularly 0.2 to
1 mm is preferred. In the present invention, the thickness of the fiber film or sheet can be adjusted by changing the basis weight as in the conventional papermaking method. Here, since the above-mentioned organic fibers are mixed in the fiber film or sheet, even if the solvent is evaporated and removed, the thickness does not change so much and voids are formed in the fiber film or sheet.

The fiber film or sheet thus obtained is impregnated with a thermosetting resin and then heated to cure the resin. By doing so, the impregnated thermosetting resin is cured by heating to form a thin plate (hereinafter referred to as "fiber thin plate").

Here, examples of the thermosetting resin include a phenol resin and a polyimide resin, but a resol-type phenol resin is preferable because of its low cost.
The resol-type phenol resin is produced by carrying out an addition condensation reaction between phenols and formalin in an alkaline manner, and is a LiOH catalyst or NH ₄ OH.
What was synthesize | combined with is preferable. LiOH catalyst or NH
_The one synthesized with ₄ OH is not harmful even if the impurities in the electrode are slight or present. On the other hand, Na
The one synthesized with an OH catalyst is not preferable because the sodium content remains in the electrode. Further, when a thermoplastic resin is used, the shape as a thin plate cannot be maintained during firing which will be described later, which is not preferable.

The thermosetting resin with which the fiber film or sheet is impregnated has a nonvolatile content of 10 to 200% by weight, particularly 50 to 150% by weight, based on the fiber film or sheet.
Is preferred. When the thermosetting resin is less than 10% by weight,
It is difficult to obtain the effect as a binder. On the other hand, when it exceeds 200% by weight, the carbonaceous material may be covered too much and the function as an active material may be deteriorated.

Next, the fiber thin plate is fired to form a carbon thin plate used as a negative electrode body. Here, the firing may be performed to such an extent that the organic fibers and the thermosetting resin forming the fiber thin plate are carbonized in an amorphous state. Therefore, the firing conditions are preferably 600 to 1,200 ° C. for 0 to 4 hours, and particularly preferably 650 to 800 ° C. for 0.5 to 2 hours. At this time, it is preferable to raise the temperature gradually, preferably 3 ° C. /
Minutes or less. The firing atmosphere is preferably a non-oxidizing atmosphere, particularly an inert gas atmosphere. In order to keep the carbon thin plate flat, it is preferable that the fibrous thin plate is sandwiched between flat graphite plates during firing.

The thus obtained negative electrode made of a carbonaceous material is loaded with lithium corresponding to the amount of lithium lost during the charging / discharging cycle to obtain a negative electrode for a lithium battery.

As described above, by supporting lithium in advance, the amount of the positive electrode active material can be limited, so that a battery having an excellent energy density can be obtained. As a method of supporting lithium, a lithium foil is brought into contact with the substrate to thermally diffuse it, or lithium is electrochemically doped in a lithium salt solution, or it is immersed in molten lithium to diffuse lithium into carbon. It can be whatever method is used.

On the other hand, the positive electrode of the lithium secondary battery to which the present invention is applied is made of a positive electrode active material containing no lithium involved in charging / discharging. In the present invention, the lithium involved in charging / discharging means lithium exclusively scheduled to be involved in charging / discharging.

The positive electrode active material is preferably a metal composite oxide, among which V ₂ O ₅ , CoCO ₃ , P ₂ O ₅ , and MO (where M represents an alkaline earth metal element).
A solid solution of a metal composite oxide consisting of is more preferable. Alkaline earth metal oxides (MO) include, for example, MgO and Ca.
O etc.

The proportion of V ₂ O _{5 in} the solid solution is preferably 64 to 92 mol%, particularly preferably 65 to 80 mol%.
The ratio of CoCO _{3 to 2} O ₅ is 10 mol% or less, preferably 1 to 6 mol%, and the ratio of P ₂ O ₅ to V ₂ O ₅ is 1 to 24 mol%, particularly 2 to 15 mol%. And the ratio of MO to V ₂ O ₅ is 2 to 25 mol%, particularly 2 to 15 mol% (provided that V ₂
O ₅ + P ₂ O ₅ + CoCO ₃ + MO = 100 mol%) is preferable.

Of these, V ₂ O ₅ is 64 mol% in the solid solution.
If it is less than 90%, the discharge capacity is lowered, while if it exceeds 92% by mole, it becomes difficult to amorphize, and a satisfactory result cannot be obtained as a positive electrode material. Further, the ratio of CoCO ₃ to V ₂ O ₅ is 1
If it is less than 10 mol%, the effect due to addition, that is, the cycle stability may not be further improved in some cases, while if it exceeds 10 mol%, both the initial capacity and the cycle stability will decrease. Furthermore, amorphized becomes difficult is less than 1 mole percent ratio of P ₂ O ₅ with respect to V ₂ O _5, satisfactory results as a positive electrode material can not be obtained, whereas the discharge capacity exceeds 24 mol%, is reduced I will end up. Further, if the ratio of MO to V ₂ O ₅ is less than 2 mol%, it becomes difficult to crystallize it, and a satisfactory result cannot be obtained as a positive electrode material, while if it exceeds 25 mol%, the discharge capacity decreases.

The metal composite oxide used in the present invention includes
It is more preferable that the metal composite oxide contains a lithium compound in addition to the metal oxide. The lithium compound is at least one selected from the group consisting of a lithium oxide compound, a lithium halide, and a lithium oxyacid salt (hereinafter, simply referred to as “lithium compound”), and specifically, for example, Li ₂ O, LiOH · H. ₂ O, L
Examples thereof include i ₂ CO ₃ , LiF, LiCl, LiBr, LiI and the like. The lithium contained in the lithium compound used here is not exclusively involved in charging / discharging, and is previously doped between the V ₂ O ₅ layers as irreversible lithium that is not undoped in the initial cycle. As described above, by using the lithium compound together with other metal oxides, it is possible to improve the charge / discharge efficiency 1 from the first cycle.
A charge / discharge cycle of 00% can be performed.

[0040] The amount of Li compound, relative to the charge-discharge cycle capacity design value of the positive electrode material, from the initial stage may be adjusted so as to a reversible cycle, but 2 against Preferably, V ₂ O ₅ 1 mol. 0 mol or less, more preferably 0.1 to
2.0 mol, more preferably 0.25 to 1.65 mol, and still more preferably 0.30 to 1.0 mol. If the amount of the lithium compound added exceeds 2.0 mol per 1 mol of V ₂ O ₅ , the solid solution will not become amorphous, which is not preferable.

The positive electrode material used in the present invention is V ₂ O.
The metal composite oxide of ₅ , ₅ , CoCO ₃ , P ₂ O ₅ , MO and Li compounds is preferably an amorphous solid solution. Such an amorphous solid solution includes V ₂ O ₅ , CoCO ₃ ,
It can be obtained by mixing P ₂ O ₅ , MO, and Li compounds, melting them, and then rapidly cooling them. Upon melting, it is preferable to hold at 200 to 500 ° C. for 30 minutes to 6 hours, and further to hold at 560 to 740 ° C. for 5 minutes to 1 hour. For quenching, use twin rollers made of copper at room temperature (1
0 ⁶ ℃ / sec), water drop (quenching rate 10 ² to 10 ³
℃ / sec) or metal plate pressing method (quenching rate 10 to 10 ⁴ ℃ /
Second) etc. The obtained amorphous solid solution is very stable, and the positive electrode material can be obtained by mechanically pulverizing this amorphous solid solution and subjecting it to heat treatment.

Further, the amorphous solid solution thus obtained is preferably after being poured into water or after being pressed with a metal plate and before or after crushing.
By heat treatment at a temperature of 0 to 500 ° C., more preferably 150 to 400 ° C., and particularly preferably 210 to 300 ° C., the solid solution changes from a uniform isotropic amorphous structure to a crystalline structure to improve conductivity. However, it is possible to obtain a positive electrode material which is excellent in cycle stability even with a large current, has small polarization, and has a small decrease in energy density.

When a positive electrode is manufactured using this positive electrode material, the particle size of the positive electrode material is not necessarily limited, but a high performance positive electrode can be manufactured by using an average particle size of 5 μm or less. In this case, for these powders,
Add conductive agent such as acetylene black or binder such as fluororesin powder, dry mix, roll and roll,
The positive electrode can be produced by a method such as drying. The conductive agent may be mixed in an amount of 5 to 50 parts by weight, particularly 7 to 10 parts by weight, based on 100 parts by weight of the positive electrode material, and in the present invention, the positive electrode material has good conductivity. Therefore, the amount of conductive agent used can be reduced. The amount of the binder mixed is preferably 5 to 10 parts by weight with respect to 100 parts by weight of the positive electrode material.

Further, the non-aqueous electrolyte used in the present invention is chemically stable with respect to the positive electrode material and the negative electrode material, and is a non-aqueous electrolyte capable of moving to cause an electrochemical reaction with the positive electrode active material. Any water substance can be used, in particular, a compound composed of a combination of a cation and an anion, wherein Li ⁺ is a cation,
Examples of anions include PF ₆ ⁻ , AsF ₆ ⁻ , Sb.
F ₆ ^- halide anions of Va group elements, such as, I
^- , I ₃ ⁻ , Br ⁻ , Cl ⁻ , a halogen anion such as ClO ₄ ⁻ , a perchlorate anion, HF ₂ ⁻ ,
CF ₃ SO ₃ ^-, SCN ^- can be exemplified compounds having an anion such as, but not necessarily limited to these anions. Specific examples of the electrolyte having such cations and anions include LiPF ₆ and Li
AsF ₆ , LiSbF ₆ , LiBF ₄ , LiClO ₄ ,
LiI, LiBr, LiCl, LiAlCl ₄ , LiH
F _2, LiSCN, and the like LiCF ₃ SO _3. Among these, especially LiPF ₆ , LiAs
F ₆ , LiSbF ₆ , LiBF ₄ , LiClO ₄ , Li
CF ₃ SO ₃ is preferred.

The non-aqueous electrolyte is usually used in a state of being dissolved in a solvent. In this case, the solvent is not particularly limited, but a solvent having a relatively large polarity is preferably used. Specifically, propylene carbonate, ethylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, dioxane, dimethoxyethane, glymes such as diethylene glycol dimethyl ether, lactones such as γ-butyrolactone, phosphoric acid esters such as triethyl phosphate, boric acid. Boric acid esters such as triethyl, sulfolane, sulfur compounds such as dimethyl sulfoxide, nitriles such as acetonitrile, amides such as dimethylformamide and dimethylacetamide, dimethyl sulfate, nitromethane,
Mention may be made of one kind or a mixture of two or more kinds such as nitrobenzene and dichloroethane. Of these, propylene carbonate, ethylene carbonate, butylene carbonate, tetrahydrofuran, 2-
One or a mixture of two or more selected from methyltetrahydrofuran, dioxane, dimethoxyethane, dioxolane and γ-butyrolactone is preferable.

Further, as the non-aqueous electrolyte, the above non-aqueous electrolyte is impregnated with a polymer such as polyethylene oxide, polypropylene oxide, an isocyanate cross-linked product of polyethylene oxide, or a phosphazene polymer having an ethylene oxide oligomer as a side chain. It is also possible to use an organic solid electrolyte, an inorganic ion derivative such as Li ₃ N or LiBCl ₄ , or an inorganic solid electrolyte such as lithium glass such as Li ₄ SiO ₄ or Li ₃ BO ₃ .

A lithium secondary battery to which the manufacturing method of the present invention is applied will be described with reference to the drawings. In this lithium secondary battery, as shown in FIG. 3, the opening 10 a has the negative electrode cover plate 2.
A button-shaped positive electrode case 10 sealed with 0 is partitioned by a separator 30 having fine holes, and a positive electrode 50 having a positive electrode current collector 40 arranged on the positive electrode case 10 side is housed in the partitioned positive electrode side space. On the other hand, the negative electrode current collector 60 is provided in the negative electrode side space.
The negative electrode 70 in which the negative electrode 70 is arranged on the side of the negative electrode cover plate 20 is housed.

As the separator 30, a non-woven fabric, a woven fabric or a knitted fabric, which is porous and capable of passing or containing an electrolytic solution, such as polytetrafluoroethylene, polypropylene or polyethylene, is used. can do. Further, as the positive electrode material used for the positive electrode 50, burned particles such as lithium-containing vanadium pentoxide and lithium-containing manganese dioxide can be used. Reference numeral 80 denotes a polyethylene insulating packing that is provided around the inner peripheral surface of the positive electrode case 10 to insulate and support the negative electrode cover plate 20.

[0049]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The following parts and percentages are by weight unless otherwise specified.

Example 1 Preparation of Negative Electrode Polyphenylene synthesized by the Kovacic method was dried and classified to obtain a powder having a particle size of 300 μm or less. This was heated in nitrogen from room temperature to 500 ° C. in 2 hours, then heated from 500 ° C. to 700 ° C. in 5 hours, and held at 700 ° C. for 1 hour to perform firing. 1.4 g of this baked powder, 0.6 g of cellulose, 0.1 g of Denka Black (produced by Denki Kagaku Kogyo Co., Ltd.), 20 ml of ethanol, and 20 ml of 0.5 wt% polyoxyethylene octyl phenyl ether aqueous solution were measured, These were mixed with a mixer for 10 minutes, then poured into a 130 × 130 mm stainless steel vat and dried to obtain a paper-like carbon film.

On the other hand, in a 500 ml separable flask, 94 g of phenol, 4 ml of ammonia water and Li were added.
10 g of OH.H ₂ O and 97 g of 37% by weight concentration formalin were added in this order, and the mixture was boiled for 60 minutes while mixing. After completion of the reaction, heat dehydration is performed under a reduced pressure of about 20 mmHg,
The dehydration was stopped when the resin temperature reached 75 ° C. After cooling, when the resin temperature reached 65 ° C, 200 ml
Was added to obtain a varnish of resol-based phenol resin.

A carbon film was impregnated with 4 ml of the above varnish and kept at 80 ° C. for one day to cure. After curing, while applying a pressure of 100 kgf / cm ² at 160 ° C., 1
Hold for 0 minutes. This was sandwiched between graphite plates, the temperature was raised from room temperature to 160 ° C in a nitrogen atmosphere in 30 minutes, and then 640
The temperature was raised to 3 ° C. in 3 hours, the temperature was maintained at 640 ° C. for 1 hour, and firing was performed to obtain a carbon thin plate. 40 x 40 m of this carbon thin plate
It was cut out into m and used as a negative electrode.

87 parts by weight of V ₂ O ₅ , ₅ parts by weight of CoCO ₃ , 4 parts by weight of P ₂ O ₅ and 4 parts by weight of CaO were weighed in a molar ratio for preparing the positive electrode .
Further, LiOH.H ₂ O was weighed so as to be 60 mol% with respect to V ₂ O ₅ , and the total amount was adjusted to 10 g, and they were well mixed in a mortar.

The above mixture was put into a 30 ml porcelain crucible, heated from room temperature to 400 ° C. at a temperature rising rate of 10 ° C./min, kept at 400 ° C. for 30 minutes, and then heated at 30 ° C./min. The temperature was raised to 740 ° C. and held for 30 minutes to melt. Then, the melt was dropped onto a copper plate having a thickness of 20 mm, and a copper plate having a thickness of 10 mm was dropped from above and sandwiched, and the mixture was rapidly cooled to obtain a thin plate-like amorphous material. This amorphous material was put into a 500 ml Cr steel crushing pot, and the diameter was 10 m.
1 with a planetary ball mill using crushed balls made of Cr steel
After pulverizing for a time to form a powder, the powder was classified to have a diameter of 106 μm or less, and the pulverized powder was further pulverized with a jet mill to obtain a positive electrode active material powder having an average particle diameter of 2 μm.

85% by weight of amorphous V ₂ O ₅ as an active material and 7.5% of Ketjen black as a conductive agent were used.
% By weight, Teflon 65 as a binder is weighed to be 7.5% by weight, and these are mixed in a mortar to give a diameter of 20 m.
It was press-molded with a metal mold of m at 400 kgf / cm ² to obtain pellets. The pellets were rolled and cut into a sheet of 40 × 40 mm, and a current collector carbon fiber was pressure-bonded thereto. After that, heat treatment in vacuum at 250 ° C. for 2 hours,
It was used as the positive electrode.

Charge / Discharge Cycle Test The negative electrode thus obtained, a lithium metal foil as a counter electrode, and EC (propylene carbonate) and DME (dimethyl ether) as an electrolytic solution (volume ratio = 1: 1)
A temporary cell was prepared by dissolving LiPF ₆ in the solvent of 1 mol / l at a concentration of 1 mol / l (hereinafter referred to as “LiPF ₆ EC / DME”) and using a glass filter as a separator. This cell was electrically short-circuited from the outside to support Li in the negative electrode. Next, this temporary cell was disassembled in a glove box in an argon atmosphere, and then the negative electrode was left in the atmosphere for 60 minutes.

The negative electrode was again placed in a glove box in an argon atmosphere, and the positive electrode and the battery cell shown in FIG. 1 were assembled using the electrolytic solution LiPF ₆ EC / DME. Charge / discharge was repeated at a charge / discharge current density of 1.6 mA / cm ² , a discharge end potential of 1.5 V, and a charge end potential of 3.8 V. The weight of the positive electrode was 0.98 g, and the weight of the negative electrode was 0.58 g. FIG. 2 shows the results of the charge / discharge cycle test. According to FIG. 2, the energy density per electrode weight is about 175 Wh / kg.
It can be seen that the high energy density is maintained and the cycle stability is extremely excellent.

Comparative Example 1 A negative electrode and a positive electrode were prepared in the same manner as in Example 1, the lithium was supported on the negative electrode, and then immediately assembled in a glove box in an argon atmosphere with the positive electrode. Then, a charge / discharge cycle test was conducted. The weight of the positive electrode was 0.96 g, and the weight of the negative electrode was 0.55 g. The result is shown in FIG.

According to FIG. 2, the lithium secondary battery of Example 1 using the negative electrode which was left in the atmosphere for 60 minutes after supporting lithium was compared with Comparative Example 1 using the negative electrode which was not left in the atmosphere. It was found that there was no difference in cycle stability as compared with the lithium secondary battery of. Further, it was found that the lithium secondary battery of Example 1 was a lithium secondary battery having high energy density and good performance.

[0060]

EFFECTS OF THE INVENTION According to the present invention, even when carbon is loaded with lithium, it is stable in the atmosphere. Therefore, an inert atmosphere for assembling a battery combined with a positive electrode that does not contain lithium involved in charging and discharging, etc. No need for large-scale equipment and workability is dramatically improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional structural diagram of a battery cell of Example 1.

FIG. 3 is a chart showing the number of cycles and the discharge energy density per electrode weight in Examples and Comparative Examples.

FIG. 3 is a sectional structural view showing an example of a lithium secondary battery to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case (Cu) 2 Sealing plate (Al) 3 Negative electrode 4 Separator (containing electrolytic solution) 5 Positive electrode 6 Current collector (Al) 7 O-ring

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Atsushi Demachi 1-4-1 Chuo, Wako-shi, Saitama, Ltd. Inside Honda R & D Co., Ltd.

Claims (4)

[Claims] 1. A method for producing a lithium secondary battery, comprising a negative electrode made of a carbonaceous material and a positive electrode made of a positive electrode active material that does not contain lithium involved in charging and discharging, wherein lithium is supported on the positive electrode. A method for producing a lithium secondary battery, comprising assembling battery cells in the atmosphere after supporting lithium on a carbonaceous material of a negative electrode that is stable in the atmosphere. 2. The method for producing a lithium secondary battery according to claim 1, wherein the carbonaceous material is one obtained by firing an organic polymer compound, and the positive electrode active material is a metal composite oxide. 3. The organic polymer compound is an organic polymer compound having an aromatic structure containing at least one structure selected from the group consisting of a bent structure, a branched structure and a crosslinked structure containing an o-bond or m-bond. The method for manufacturing the lithium secondary battery according to claim 1. 4. The positive electrode active material is V ₂ O ₅ , CoCO ₃ ,
P ₂ O ₅ , MO (where M represents an alkaline earth metal element), and at least one selected from the group consisting of a lithium oxide compound, a lithium halide, and a lithium oxyacid salt were fired at 100 to 500 ° C. The method for producing a lithium secondary battery according to claim 1, which is a battery.