JP2006004805A - Nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution secondary battery in which weight energy density is high, and a cycle life characteristic is superior. <P>SOLUTION: This nonaqueous electrolytic solution secondary battery is provided with (1) an anode which contains a negative active material composed of a material in which an alkaline metal ion can be stored and released electrochemically, (2) a cathode which contains the lithium salt of an organic compound composed of carbon, nitrogen, and oxygen which has a partial structure shown in a chemical formula as a positive active material, and (3) a nonaqueous electrolytic solution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte secondary battery using an organic nitrogen compound as a positive electrode active material, and particularly to a non-aqueous electrolyte secondary battery that is lightweight and has a high capacity density.

  Among various non-aqueous electrolyte secondary batteries, the lithium secondary battery has a feature of high electromotive force and high energy density. For this reason, the demand as main power supplies, such as a mobile communication apparatus and a portable electronic device, is expanding.

In most of the lithium secondary batteries currently on the market, Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , or a part of the transition metal contained in the compound is replaced with another transition metal. Are used as positive electrode active materials. The above x is a numerical value representing the lithium content in the active material, and changes depending on the charge / discharge of the battery.

  Since the positive electrode active material for a lithium secondary battery as described above contains a transition metal having a large mass number, there is a limit to the response to weight reduction and high capacity, which are constant demands from the market. Based on this background, an attempt has been made to use a material containing a large amount of an element having a small mass number as the positive electrode active material. As an example, it has been proposed to use an organic sulfur compound with improved reversible reactivity between sulfur and lithium as a positive electrode active material of a non-aqueous electrolyte secondary battery (see Non-Patent Document 1). This proposal makes use of a reaction in which one or more sulfur-sulfur bonds that change the apparent oxidation state are cleaved to form sulfur-lithium bonds. It is stated that this organic sulfur compound has the advantage of having high conductivity by having a π-conjugated system, and improving the stability as a material by polymerizing the organic sulfur compound. .

As another example, a non-aqueous electrolyte secondary battery using a material that can be an organic stable radical compound as a reaction intermediate during a charge / discharge reaction as a positive electrode active material has been proposed (see Patent Document 1). In the charge / discharge reaction, the active material changes between a cation species, a stable radical species, and an anion species. Since such an active material is composed of only an element having a small mass number, it is stated that it is advantageous to achieve a significant increase in capacity and weight.
JP 2002-117852 A Proceedings of Fall Meeting of the Electrochemical Society of Japan 2003 35

However, in the organic sulfur compound described in Non-Patent Document 1, the sulfur-sulfur bond is relatively unstable and easily causes a cleavage reaction under the charging environment of the battery.
Moreover, the organic stable radical described in Patent Document 1 may cause a reaction of extracting a hydrogen atom from a solvent molecule of the electrolytic solution.
Therefore, when the material as described above is used for the positive electrode active material, the electrolytic solution is likely to be deteriorated by a side reaction with the electrolytic solution, and the cycle is compared with a battery using a conventional lithium-metal oxide as the positive electrode active material. The deterioration of the life characteristics becomes remarkable.

  Furthermore, since side reactions with the electrolyte involve gas generation, the battery case is deformed, which is a bottleneck for commercial practical use.

  The present invention has been accomplished in view of the above problems, and an object of the present invention is to provide a nonaqueous electrolyte secondary battery having a high weight energy density and improved cycle life characteristics.

  The present invention includes (1) a negative electrode including a negative electrode active material made of a material capable of electrochemically occluding and releasing alkali metal ions, and (2) the following formula:

And a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte comprising a lithium salt of an organic compound composed of carbon, nitrogen and oxygen as a positive electrode active material, having the partial structure shown in FIG.

  In the non-aqueous electrolyte secondary battery, a lithium salt of an organic compound composed of carbon, nitrogen and oxygen has the following formula:

It is preferable that it is shown by. In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are each independently a hydrogen atom, alkyl group, cycloalkyl group, alkenyl group, alkoxy group, alkoxycarbonyl group, aryl group, And one or more hydrogen atoms selected from the group consisting of an acyl group, an alkyl group, a cycloalkyl group, an alkenyl group, an alkoxy group, an alkoxycarbonyl group, an aryl group, or an acyl group are substituted with a sulfur atom or a nitrogen atom. Alternatively, a cyclic structure may be formed between at least one selected from R ₁ , R ₂ , and R ₃ and at least one selected from R ₄ and R ₅ .

  In the non-aqueous electrolyte secondary battery, the material capable of electrochemically occluding and releasing alkali metal ions is preferably a material capable of electrochemically occluding and releasing lithium ions.

  In the non-aqueous electrolyte secondary battery, the material capable of electrochemically inserting and extracting lithium ions is preferably a carbon material.

  According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery having a high weight energy density and improved cycle life characteristics.

An example of the non-aqueous electrolyte secondary battery of the present invention will be described with reference to FIG.
The non-aqueous electrolyte secondary battery of FIG. 1 includes a battery case 1, a positive electrode 4 disposed in the battery case 1, a negative electrode 5, a separator 6 disposed between the positive electrode 4 and the negative electrode 5, and a positive electrode current collector 7. , A negative electrode current collector 8, and a power generation element comprising a non-aqueous electrolyte (not shown). The opening of the battery case 1 is sealed by caulking the opening end of the battery case 1 to the sealing plate 2 via the insulating gasket 3.

  The battery case 1 also serves as a positive electrode terminal and is in contact with the positive electrode current collector 7. The sealing plate 2 also serves as a negative electrode terminal and is in contact with the negative electrode current collector 8. The battery case 1 and the sealing plate 2 are insulated by an insulating gasket 3.

  The positive electrode may contain a conductive material, a binder and the like in addition to the positive electrode active material. Similarly, the negative electrode may contain a conductive material, a binder and the like in addition to the negative electrode active material.

  In the present invention, the positive electrode active material has the following partial structure:

And a lithium salt of an organic compound composed of carbon, nitrogen and oxygen.

  The lithium salt as described above is composed of an element having a small mass number. Since the transition metal element with a large mass number such as Co is not included as in the prior art, the active material itself can be reduced in weight. By using such a positive electrode active material, a battery having a high weight energy density can be obtained.

  Moreover, the above lithium salt is chemically more stable than the compound which has a structure as described in the said patent document 1 and the nonpatent literature 1. For this reason, compared with the past, reaction with an active material and a non-aqueous electrolyte solution becomes difficult to occur, and a reduction in battery cycle life is reduced. In addition, since the reaction between the active material and the non-aqueous electrolyte hardly occurs, gas generation is also reduced. Thereby, deformation of the battery case due to gas generation can be reduced.

  Further, the lithium salt of an organic compound composed of carbon, nitrogen and oxygen having the above partial structure has the following formula:

It is preferable that it is a compound shown by these. Here, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ in the above formulas are each independently a hydrogen atom, alkyl group, cycloalkyl group, alkenyl group, alkoxy group, alkoxycarbonyl Selected from the group consisting of a group, an aryl group, and an acyl group, and at least one hydrogen atom of an alkyl group, cycloalkyl group, alkenyl group, alkoxy group, alkoxycarbonyl group, aryl group, or acyl group is a sulfur atom or a nitrogen atom It may be substituted with an atom, and a cyclic structure may be formed between at least one selected from R ₁ , R ₂ , and R ₃ and at least one selected from R ₄ and R ₅ .

  Among these, an alkyl group, an aryl group, a substituted alkyl group, and a substituted aryl group are preferable.

  Next, a method for producing a lithium salt of an organic compound composed of carbon, nitrogen, and oxygen having the above partial structure, which is a positive electrode active material, will be described below. An organic compound composed of carbon, nitrogen, and oxygen can be produced.

  This positive electrode active material is synthesized by a reaction process for producing an organic compound composed of carbon, nitrogen and oxygen having the above partial structure and a reaction process using this as a lithium salt.

First, production of an organic compound having carbon, nitrogen, and oxygen having the above partial structure will be described.
An organic compound composed of carbon, nitrogen, and oxygen having the above partial structure can be easily produced by oxidizing secondary amines.
For example, secondary amines are composed of carbon, nitrogen and oxygen having the above partial structure by stirring in an organic solvent such as methylene chloride using a hydrogen peroxide solution as an oxidizing agent and a tungsten compound as a catalyst in an organic solvent such as methylene chloride. Organic compounds are obtained quantitatively.
As shown above, the resulting product has two carbon atoms at the α-position of the nitrogen atom, one of which is a single bond and the other carbon-nitrogen bond is a double bond. Any bond may be used.
The secondary amine may be aromatic or aliphatic, and may be, for example, a cyclic nitrogen compound such as pyridine.

Subsequently, the obtained organic compound composed of carbon, nitrogen and oxygen having the above partial structure is lithiated using an alkyllithium reagent such as n-butyllithium. Thereby, the target organic lithium salt (positive electrode active material) is obtained quantitatively.
The secondary amines may be synthesized or commercially available reagents may be used as they are.

  When the positive electrode active material used in the present invention is compared with the positive electrode active material described in Patent Document 1 or Non-Patent Document 1, the positive electrode active material described in Patent Document 1 or Non-Patent Document 1 is originally Some do not contain lithium. When such a lithium-free material is used as the positive electrode active material, it is necessary to use a material that can supply lithium, such as lithium foil, but is relatively unstable, as the negative electrode active material.

On the other hand, since the positive electrode active material used in the present invention contains lithium in its structure, it is not necessary to use a material capable of supplying lithium as the negative electrode active material. Accordingly, as the negative electrode active material, a material made of a material capable of inserting and extracting alkali metal ions such as lithium ions can be used. Among these, chemically stable materials, such as carbon materials such as graphite materials and non-graphitizable carbonaceous materials, or at least one metal element selected from the group consisting of silicon, tin, aluminum, zinc, and magnesium A negative electrode active material made of a material capable of occluding and releasing lithium ions, such as a lithium alloy containing hydrogen, is preferable. By using such a negative electrode active material, the cycle life characteristics of the battery can be greatly improved.
Of course, it is also possible to use a material capable of supplying lithium, such as a lithium foil, as the negative electrode active material.

  Furthermore, among these, since the chemical stability is higher, a negative electrode active material made of a carbon material is more preferable. In the case of a negative electrode active material made of a material that can occlude and release lithium ions, such as a carbon material, the average particle size is preferably 1 to 30 μm.

As the conductive material for the positive electrode, a chemically stable electron conductive material is used in the constituted battery. Examples include graphites such as natural graphite (such as flake graphite), artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, carbon fibers, and metal fibers. Conductive fibers such as carbon powder, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, or organic conductive materials such as polyphenylene derivatives Etc. These may be used alone or in combination.
Among these conductive materials, artificial graphite and acetylene black are particularly preferable from the viewpoints of chemical stability and conductivity.

  Although the addition amount of a electrically conductive material is not specifically limited, 1-50 weight% of a positive electrode is preferable and 1-30 weight% is more preferable. In addition, in the case of artificial graphite and acetylene black described above, the addition amount is preferably 2 to 15% by weight of the positive electrode.

As the positive electrode binder, any of a thermoplastic resin and a thermosetting resin may be used as long as it is stable under the charging environment of the battery. Preferable binders include, for example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoro. Propylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoro Ethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer , Ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer Examples thereof include a polymer or a sodium ion (Na ⁺ ) crosslinked product thereof, an ethylene-methacrylic acid copolymer or a sodium ion crosslinked product thereof, an ethylene-methyl acrylate copolymer, and an ethylene-methyl methacrylate copolymer. These materials may be used alone or in combination.
Among these binders, polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) are particularly preferable from the viewpoints of chemical stability and binding properties.

  The binder may or may not be included in the positive electrode. When the binder is contained in the positive electrode, the amount is generally 0.8 to 8% by weight of the positive electrode.

As the positive electrode current collector, a chemically stable electron conductor can be used in the constituted battery. Examples thereof include aluminum, stainless steel, nickel, titanium, carbon, and conductive resin. Alternatively, a surface of aluminum or stainless steel coated with carbon or titanium may be used.
Among the above materials, aluminum or an aluminum alloy is particularly preferable. Moreover, what oxidized the surface of such a material can also be used.

The positive electrode current collector is desirably provided with irregularities on the surface by surface treatment.
The positive electrode current collector may be a foil shape, a film shape, a sheet shape, a net shape, or the like. The positive electrode current collector may be a punched one, a lath processed body, a porous body, a foamed body, a molded body of a fiber group, or the like.
The thickness of the positive electrode current collector is not particularly limited, but is preferably 1 to 500 μm.

The negative electrode preferably contains a conductive material for the purpose of improving battery characteristics. As this conductive material, a chemically stable electron conductive material is used. Examples include graphites such as natural graphite (flaky graphite, etc.), artificial graphite, expanded graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber. And conductive fibers such as metal fibers, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives. These materials may be used alone or in combination.
Among these conductive materials, artificial graphite, acetylene black and carbon fiber are particularly preferable.
The addition amount of the conductive material is preferably 1 to 30 parts by weight and particularly preferably 1 to 10 parts by weight per 100 parts by weight of the negative electrode active material.

  The negative electrode binder may be either a thermoplastic resin or a thermosetting resin as long as it is stable in the battery charging environment. Examples thereof include styrene-butadiene copolymer rubber (SBR), carboxymethyl cellulose (CMC), polyethylene oxide (PEO) and the like.

As the negative electrode current collector, a chemically stable electron conductor can be used in the constituted battery. Examples thereof include stainless steel, nickel, copper, titanium, carbon, conductive resin, and the like. Moreover, you may use what coated the surface of copper or stainless steel with carbon, nickel, or titanium.
Among the above materials, copper or a copper alloy is particularly preferable. The surface of these materials can be oxidized and used.

The negative electrode current collector is desirably provided with irregularities on the surface by surface treatment. The negative electrode current collector may be a foil shape, a film shape, a sheet shape, a net shape, or the like. The negative electrode current collector may be a punched one, a lath processed body, a porous body, a foamed body, a molded body of a fiber group, or the like.
The thickness of the negative electrode current collector is preferably 1 to 500 μm.

  In addition to the conductive material and the binder, a filler, a dispersant, an ionic conductor, a pressure enhancer, and / or various other additives may be added to the positive electrode and the negative electrode.

As the filler, any material may be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used.
Moreover, it is preferable that the addition amount of a filler is 0 to 10 weight% of a positive electrode or a negative electrode.

  In the battery, it is preferable that there are one or more pairs of positive and negative electrodes facing each other with a separator interposed therebetween.

  The non-aqueous electrolyte is composed of a non-aqueous solvent and a lithium salt that dissolves in the non-aqueous solvent.

Examples of non-aqueous solvents include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), cyclic carbonates such as vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl. Chain carbonates such as methyl carbonate (EMC) and dipropyl carbonate (DPC), aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate, and γ-lactones such as γ-butyrolactone Chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE) and ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, dimethylsulfate Hoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3-dimethyl Examples include aprotic organic solvents such as 2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, diethyl ether, 1,3-propane sultone, anisole, and N-methylpyrrolidone. These may be used alone or in combination.
Among these, a mixed system of a cyclic carbonate and a chain carbonate, or a mixed system of a cyclic carbonate, a chain carbonate, and an aliphatic carboxylic acid ester is preferable.

Examples of the lithium salt (solute) dissolved in these solvents include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiCF ₃ SO ₂ , LiAsF _6. , LiN (CF ₃ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate, imides and the like. These may be used alone or in combination.
Among these, it is particularly preferable to use LiPF ₆ as a solute.

In the present invention, a preferred non-aqueous electrolyte is a non-aqueous electrolyte in which the non-aqueous solvent includes at least ethylene carbonate and ethyl methyl carbonate, and LiPF ₆ as a solute.

  The amount of these nonaqueous electrolytes added to the battery is not particularly limited, but varies depending on the amount of positive electrode material or negative electrode material, the size of the battery, and the like.

  The amount of the solute dissolved in the nonaqueous solvent varies depending on the combination of the solute and the nonaqueous solvent, but is preferably 0.2 to 2 mol / l, and more preferably 0.5 to 1.5 mol / l. preferable.

  Furthermore, other additives may be added to the non-aqueous electrolyte for the purpose of improving the charge / discharge characteristics of the battery. For example, other additives include triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, pyridine, hexaphosphoric triamide, nitrobenzene derivatives, crown ethers, quaternary ammonium salts, ethylene glycol dialkyl ethers. Etc.

As the separator, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. These separators preferably have a function of increasing resistance to ion permeation by closing pores of the separator at a predetermined temperature or higher.
In view of the organic solvent resistance of the separator and the affinity between the separator and the non-aqueous solvent, it is preferable to use a separator made of a sheet, a nonwoven fabric or a woven fabric made of an olefin polymer or glass fiber. Here, examples of the olefin polymer include polypropylene and polyethylene. These polymers may be used alone or in combination.

It is desirable that the pore diameter of the pores provided in the separator is within a range in which the positive and negative electrode materials, the binder, the conductive material and the like detached from the electrodes are not transmitted. The pore diameter is preferably 0.01 to 1 μm, for example.
The porosity of the separator is determined according to the permeability of electrons and ions, the material, and the membrane pressure. In general, the porosity is desirably 30 to 80%.
The thickness of the separator is generally preferably 10 to 300 μm.

  Further, a polymer material that absorbs and holds a non-aqueous electrolyte composed of a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent may be mixed in the positive electrode and / or the negative electrode. Furthermore, it is also possible to form a battery by integrating a porous separator made of a polymer material capable of absorbing and retaining a nonaqueous electrolytic solution with a positive electrode and a negative electrode.

As the polymer material, any polymer material may be used as long as it can absorb and retain the nonaqueous electrolytic solution. As such a polymer material, a copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferable.
Moreover, the polymer material contained in the positive electrode and / or the negative electrode and the polymer material constituting the separator may be the same or different.

  The non-aqueous electrolyte secondary battery of the present invention may have any shape such as a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a square type, a large type used for an electric vehicle, etc. Good. Further, the nonaqueous electrolyte secondary battery of the present invention can be used for portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles, hybrid electric vehicles, and the like, but is not limited thereto. I don't mean.

  Hereinafter, the present invention will be described in more detail with reference to examples.

<Study 1. About positive electrode active material>
First, a method for synthesizing a positive electrode active material will be described.
Table 1 shows raw materials (raw material amine and raw material chloride), intermediate product (secondary amine), and final product (positive electrode active material) used for producing positive electrode active material 1d. In addition, as a raw material amine and raw material chloride as raw materials, all reagents manufactured by Aldrich, USA were used.
Tables 1 and 2 show the raw materials (raw material amine and raw material chloride), intermediate product (secondary amine), and final product (positive electrode active material) used for the positive electrode active materials 2d to 11d, respectively.
Moreover, about the active material 11d, the synthesis | combination process was abbreviate | omitted by not using the morpholine (11c) which is an intermediate product from the raw material, but using the morpholine by the US Aldrich company.

A method for synthesizing the positive electrode active material 1d will be described below.
To 500 ml of methylene chloride, 0.1 mol of t-butylamine (1a) and 0.15 mol of triethylamine were added. The obtained solution was poured into a three-necked flask having a volume of 1000 ml. While the flask was cooled to 0 ° C., 2-chloropropane (1b) was added dropwise from the funnel in an amount of 0.1 mol.
After complete addition of 2-chloropropane (1b), the reaction solution was stirred at room temperature for 3 hours.
The reaction solution was transferred to a 1000 ml separatory funnel and the reaction solution was washed 3 times with 500 ml distilled water.
To the extracted organic layer, 20 g of anhydrous sodium sulfate was added and left for 3 hours to dehydrate the organic layer. Thereafter, the organic layer was filtered using a filter paper to remove the sodium sulfate. Next, the solvent, methylene chloride and triethylamine, were removed from the filtrate using a rotary vacuum evaporator. Thereafter, the product liquid was distilled under reduced pressure to obtain a secondary amine (1c) as an intermediate product.

Next, the intermediate product (1c) was dissolved in 100 ml of methylene chloride. Methylene chloride in which this intermediate product was dissolved was added to a 500 ml flask. To this flask, 100 ml of 35% aqueous hydrogen peroxide and 1 g of sodium tungstate as a catalyst were added, and then stirred at room temperature for 20 hours.
100 ml of methylene chloride was added to the reaction solution in the flask. The solution was transferred to a 500 ml separatory funnel and washed 3 times with 100 ml distilled water.

To the extracted organic layer, 20 g of anhydrous sodium sulfate was added and left for 3 hours to dehydrate the organic layer. Thereafter, the organic layer was filtered using a filter paper to remove the sodium sulfate. Next, methylene chloride as a solvent was evaporated from the filtrate using a rotary vacuum evaporator.
The product white solid was purified by a recrystallization method using n-hexane, and then dried under an argon atmosphere to obtain a purified product.

This purified product was dissolved in 100 ml of anhydrous tetrahydrofuran in an amount of 0.01 mol. The resulting solution was poured into a three-necked flask and the solution was cooled to 0 ° C.
Thereafter, 0.01 mol of n-butyllithium was added to the cooled reaction solution by dropping a predetermined amount of an n-hexane solution in which n-butyllithium was dissolved at a concentration of 1.6 mol / l, This was followed by stirring for 3 hours.
The temperature of this solution was returned to room temperature and reacted for another 20 hours. Then, when the solvent tetrahydrofuran and n-hexane were removed, a yellow solid was obtained. The obtained yellow solid was used as an active material (1d).

It was identified that the obtained yellow solid had a structure like 1d in Table 1 by using nuclear magnetic resonance spectra ( ¹ H and ¹³ C), infrared absorption spectrum, and mass spectrum of hydrogen and carbon.

  The positive electrode active materials 2d to 11d were synthesized in the same manner as the positive electrode active material 1d by using an appropriate reaction temperature and reaction time. Further, the positive electrode active materials 2d to 11d were identified in the same manner as the positive electrode active material 1d.

(Preparation of positive electrode)
85 mg of the active material (1d) obtained as described above is weighed, 10 mg of acetylene black powder (manufactured by Denki Kagaku Kogyo Co., Ltd.) is weighed, and PTFE powder (manufactured by Daikin Industries, Ltd .; F-101F) is obtained. 5 mg was weighed. These were thoroughly mixed in an agate mortar.
The obtained mixture was rolled with a roller-type rolling mill equipped with a roller having a diameter of 10 cm to form a sheet having a thickness of 200 μm. A circular pellet having a diameter of 12.5 mm was punched out from this sheet. The punched circular pellet was dried under reduced pressure at 110 ° C. for 20 hours to obtain a positive electrode mixture layer.

(Battery assembly)
A battery as shown in FIG. 1 was produced.
Lithium hexafluorophosphate was dissolved in an ethylene carbonate / ethyl methyl carbonate mixed solvent (volume ratio 1: 3) at a concentration of 1.5 mol / l to obtain a non-aqueous electrolyte. The positive electrode mixture layer obtained as described above was impregnated with this nonaqueous electrolytic solution. Thereafter, the positive electrode mixture layer impregnated with the non-aqueous electrolyte and the stainless steel plate (thickness: 100 μm) as the positive electrode current collector were integrated.

  Next, the separator which consists of a polyethylene porous membrane (thickness: 20 micrometers) was arrange | positioned on the positive mix layer. A negative electrode active material made of a metal lithium foil (thickness: 150 μm) was laminated on the separator, and a negative electrode current collector (thickness: 10 μm) made of electrolytic copper was laminated thereon. In this way, an electrode group was produced.

  Next, the obtained electrode group was accommodated in a stainless steel battery case provided with an insulating packing. A sealing plate was disposed in the opening of the battery case. Next, this was pressed with a flat plate press at a pressure of 20 t, and the opening end of the battery case was caulked to the sealing plate via the insulating packing, and the opening of the battery case was sealed. Thus, a coin-type battery having a diameter of 20 mm and a thickness of 1.6 mm was produced. The obtained battery was designated as battery 1.

  Then, the battery was produced like the case of the battery 1 except having made the positive electrode active material into 2d-11d. The obtained batteries were designated as batteries 2 to 11, respectively.

  A battery was produced in the same manner as in the case of the battery 1 except that the positive electrode active material was an intermediate product 1c of the positive electrode active material 1d. The obtained battery was designated as comparative battery 1.

  A battery was fabricated in the same manner as for the battery 1 except that the organic sulfur compound 12 or the organic stable radical compound 13 shown in FIG. 2 was used as the positive electrode active material. The obtained batteries were designated as comparative battery 2 and comparative battery 3, respectively.

  The following tests were performed on the batteries produced as described above.

(Capacity confirmation test)
The battery immediately after fabrication was charged in a 45 ° C. environment at a constant current (0.1 mA) until the battery voltage reached 4.0 V, and then the battery voltage was set to 2.0 V at a constant current (0.1 mA). Discharging was performed until the discharge capacity was calculated. The obtained discharge capacity was defined as the discharge capacity at the first cycle. The results obtained are shown in Table 3.

(Cycle life test)
In each battery, the charge / discharge cycle was repeated 20 times under the same conditions as in the capacity confirmation test. The discharge capacity and battery thickness at the 10th and 20th cycles were measured for each battery. The results obtained are shown in Table 3.

First, the comparative battery 2 using the organic sulfur compound 12 as the positive electrode active material and the comparative battery 3 using the organic stable radical compound 13 remarkably increase the battery thickness at a relatively early stage by repeating the charge / discharge cycle. The discharge capacity decreased.
The gas in the battery case of the comparative battery 2 and the comparative battery 3 was sampled, and the composition was examined by gas chromatography. As a result, carbon dioxide gas and carbon monoxide, which are considered to be a reaction product of the nonaqueous electrolytic solution and the positive electrode active material, were detected.

  On the other hand, all of the batteries 1 to 11 exhibited relatively good cycle life characteristics. Moreover, the increase in battery thickness was not seen. Therefore, it was found that the positive electrode active material used for the batteries 1 to 11 is a chemically stable material under the usage environment of the battery.

  However, the comparative battery 1 using 1c, which is not a lithium salt, as the positive electrode active material is not fully charged at the initial stage. This is because the transfer of electrons from the positive electrode to the negative electrode, which is a charging reaction, did not occur because the positive electrode active material does not contain a cationic species.

  From the above results, it was found that a lithium salt of an organic compound composed of nitrogen, oxygen and carbon having the partial structure as described above is effective as a positive electrode active material of a non-aqueous solution secondary battery.

<Study 2. About negative electrode active material>
As the negative electrode active material, artificial graphite (manufactured by Timcal Japan Co., Ltd .; KS-4) was used, and this was molded into a 100 μm-thick pellet as a negative electrode. A battery was produced. The obtained battery was designated as battery 12.

  A battery was produced in the same manner as in the case of the battery 1 except that a metal tin foil was used as the negative electrode active material, and this was molded into a pellet having a thickness of 100 μm to form a negative electrode. The obtained battery was designated as battery 13.

  The battery produced as described above was subjected to a capacity confirmation test and a cycle life test in the same manner as in Example 1. Table 4 shows the obtained results.

As with the battery 1 of Example 1, the battery 12 and the battery 13 were able to be charged and discharged satisfactorily without increasing the battery thickness.
Moreover, the cycle life characteristics of the battery 13 were lower than the cycle life characteristics of the battery 12 within the practical range. After the cycle life test, the battery 13 was disassembled and the positive electrode and the negative electrode were observed. As a result, in the negative electrode, a white film thought to be an oxide was confirmed on the tin foil. Therefore, it is considered that the capacity of the battery was lowered because the positive electrode was not deteriorated during the cycle life test but because of the resistance of the film formed on the negative electrode.

  From the above results, when a lithium salt of an organic compound composed of carbon, nitrogen, and oxygen having a partial structure as described above is used as a positive electrode active material, a material that can occlude lithium in the structure, such as a carbon material or metallic tin It is understood that charging / discharging is possible even when a negative electrode active material made of is used. Furthermore, it can be seen that when a graphite material, which is a carbon material, is used, a battery superior in cycle life characteristics can be obtained.

  According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery having a high weight energy density and excellent cycle life characteristics.

The longitudinal cross-sectional view of the nonaqueous electrolyte secondary battery concerning one Embodiment of this invention is shown. The structure of the organic sulfur compound 12 used as the positive electrode active material of the comparative battery 2 and the comparative battery 3 and the organic stable radical compound 13 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulation packing 4 Positive electrode 5 Negative electrode 6 Separator 7 Positive electrode collector 8 Negative electrode collector

Claims (4)

(1) A negative electrode including a negative electrode active material made of a material capable of electrochemically storing and releasing alkali metal ions,
(2) The following formula:

A positive electrode comprising, as a positive electrode active material, a lithium salt of an organic compound comprising carbon, nitrogen and oxygen, having a partial structure represented by
(3) A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte. The lithium salt of the organic compound comprising carbon, nitrogen and oxygen has the following formula:

R ₁ , R ₂ , R ₃ , R ₄ and R ₅ in the above formula are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group, an alkoxy group, an alkoxycarbonyl group, Selected from the group consisting of an aryl group and an acyl group, and one or more hydrogen atoms of an alkyl group, a cycloalkyl group, an alkenyl group, an alkoxy group, an alkoxycarbonyl group, an aryl group, or an acyl group are a sulfur atom or a nitrogen atom The ring structure may be substituted and may form a cyclic structure between at least one selected from R ₁ , R ₂ and R ₃ and at least one selected from R ₄ and R _5. The nonaqueous electrolyte secondary battery as described.   The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the material capable of electrochemically occluding and releasing alkali metal ions is a material capable of electrochemically occluding and releasing lithium ions.   The nonaqueous electrolyte secondary battery according to claim 3, wherein the material capable of electrochemically inserting and extracting lithium ions is a carbon material.

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