CN106099191B - Nonaqueous electrolyte and nonaqueous electrolyte battery - Google Patents

Abstract

The invention provides a nonaqueous electrolyte and a nonaqueous electrolyte battery. The nonaqueous electrolyte includes: a solvent; an electrolyte salt; and at least one of heteropolyacid salt compounds represented by the following formulae (I) and (II): h_xA_y[BD₁₂O₄₀].zH₂O (I)H_pA_q[B₅D₃₀O₁₁₀].rH₂O (II) wherein A represents Li, Na, K, Rb, Cs, Mg, Ca, Al, NH₄Or an ammonium or phosphonium salt; b represents P, Si, As or Ge; d represents at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Tc, Rh, Cd, In, Sn, Ta, W, Re and Tl; x, y and z are values falling within the ranges 0. ltoreq. x.ltoreq.1, 2. ltoreq. y.ltoreq.4 and 0. ltoreq. z.ltoreq.5, respectively; and p, q and r are values falling within the ranges of 0. ltoreq. p.ltoreq.5, 10. ltoreq. q.ltoreq.15 and 0. ltoreq. r.ltoreq.15, respectively.

Description

Nonaqueous electrolyte and nonaqueous electrolyte battery

The present application is a divisional application of an invention patent application having an application date of 2011, 2, 23, and an application number of 201110044358.0, entitled "nonaqueous electrolyte and nonaqueous electrolyte battery".

Technical Field

The invention relates to a nonaqueous electrolyte and a nonaqueous electrolyte battery. More particularly, the present invention relates to a nonaqueous electrolyte including an organic solvent and an electrolyte salt, and a nonaqueous electrolyte battery using the same.

Background

In recent years, portable electronic devices such as camera-integrated VTRs (video tape recorders), mobile phones, and laptop personal computers have been widely spread, and there is a strong demand for realizing their miniaturization, light weight, and long life. Along with this, development of batteries as portable power sources for electronic devices, particularly secondary batteries that are lightweight and from which high energy density can be obtained, has been advanced.

In particular, secondary batteries (so-called lithium ion secondary batteries) utilizing insertion and extraction of lithium (Li) for charge/discharge reactions are widely put into practical use because a high energy density can be obtained as compared with conventional lead batteries and nickel cadmium batteries as nonaqueous electrolyte secondary batteries. Such a lithium ion secondary battery is provided with an electrolyte, and a positive electrode and a negative electrode.

In particular, a laminate type battery using an aluminum laminate film for a package member has a large energy density due to its light weight. Also, in the laminate type battery, when the nonaqueous electrolytic solution swells into the polymer, deformation of the laminate type battery can be suppressed, and therefore, the laminate type polymer battery is also widely used.

However, in the laminate type battery, since the package is soft, there is involved a problem that the battery is liable to cause swelling (blistering) due to gas generated inside the battery at the time of initial charging and also at the time of high-temperature storage. In response to this problem, as described in patent document 1(JP- ｃA-2006-. However, such a reactive cyclic carbonate cannot suppress the expansion of the battery when used at high temperatures.

Further, patent document 2(JP-A-2002-289188) proposes the use of ｃA heteropolyacid salt as an electrode active material, which is ｃA compound capable of intercalating and deintercalating lithium ions and which attains ｃA relatively stable structure.

Disclosure of Invention

However, patent document 1 does not result in obtaining sufficient battery characteristics because of the reactivity of the heteropoly-acid itself as the redox agent. The reason why sufficient characteristics are not obtained is because: heteropolyacids are themselves strong redox agents and are strong acids; the heteropoly-acid contains crystal water and the like in its structure. Therefore, when such a heteropoly acid compound is added to an electrode mixture or a nonaqueous electrolytic solution in advance, heteropoly acids having very high redox ability and free acids derived from crystal water, for example, tetrahydrofuran (hydrofuran) and the like corrode a current collector or a binder, resulting in deterioration of battery characteristics such as resistance.

Further, patent document 2 relates to the use of a heteropoly acid for the active material itself, but does not relate to the improvement of safety by the use of a heteropoly acid.

Therefore, it is desirable to provide a nonaqueous electrolyte and a nonaqueous electrolyte battery each capable of suppressing gas generated inside the battery at the time of initial charging and also at the time of high-temperature storage and hardly causing swelling of the battery.

According to an embodiment of the present invention, there is provided a composition comprising a solvent; an electrolyte salt and at least one of heteropolyacid salt compounds represented by the following formulae (I) and (II).

According to another embodiment of the present invention, there is provided a nonaqueous electrolyte battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein a gel-like coating layer containing one or more multi-element amorphous polyacids and/or polyacid compounds is provided on a surface of at least a portion of the negative electrode, the coating layer being derived from at least one of heteropolyacid salt compounds represented by the following formulae (I) and (II).

H_xA_y[BD₁₂O₄₀]·zH₂O (I)

In formula (I), A represents lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), aluminum (Al), ammonium (NH)₄) Ammonium or phosphonium salts (phosphonium salts); b represents phosphorus (P), silicon (Si), arsenic (As) or germanium (Ge); d represents at least one element selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), rhodium (Rh), cadmium (Cd), indium (In), tin (Sn), tantalum (Ta), tungsten (W), rhenium (Re), and thallium (Tl); and x, y and z are values falling within the ranges of 0. ltoreq. x.ltoreq.1, 2. ltoreq. y.ltoreq.4 and 0. ltoreq. z.ltoreq.5, respectively.

H_pA_q[B₅D₃₀O₁₁₀]·rH₂O (II)

In formula (II), A represents lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), aluminum (Al), ammonium (NH)₄) Ammonium or phosphonium salts; b represents phosphorus (P), silicon (Si), arsenic (As) or germanium (Ge); d represents at least one element selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), rhodium (Rh), cadmium (Cd), indium (In), tin (Sn), tantalum (Ta), tungsten (W), rhenium (Re), and thallium (Tl); and p, q and r are values falling within the ranges of 0. ltoreq. p.ltoreq.5, 10. ltoreq. q.ltoreq.15 and 0. ltoreq. r.ltoreq.15, respectively.

According to the embodiment of the invention, due to the fact that the nonaqueous electrolytic solution contains at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II), the moisture and the acid component in the nonaqueous electrolytic solution can be reduced. Thus, in the nonaqueous electrolyte battery using the nonaqueous electrolyte, not only can a coating layer be formed on the negative electrode, but also a side reaction due to moisture and an acid component in the electrolyte can be suppressed.

According to the embodiment of the present invention, decomposition of the electrolyte can be suppressed, whereby gas generation can be suppressed. Also, deterioration of each part of the battery can be suppressed.

Drawings

Fig. 1 is a sectional view showing a configuration example of a nonaqueous electrolyte battery according to an embodiment of the present invention.

Fig. 2 is a sectional view showing a part of the wound electrode body in fig. 1 in an enlarged manner.

Fig. 3 is an SEM photograph of the surface of the anode according to the embodiment of the present invention.

Fig. 4 is a diagram showing an example of a secondary ion spectrum by time-of-flight (ToF-SIMS) secondary ion mass spectrometry on the surface of a negative electrode on which deposits (precipitates) are deposited by adding silicotungstic acid to a battery system.

Fig. 5 is a diagram showing an example of a radial structure function (radial structure function) of a W-O bond obtained by fourier transform of a spectrum, analyzed by X-ray absorption micro structure (XAFS) on a surface of a negative electrode on which deposits are deposited by adding silicotungstic acid to a battery system.

Fig. 6 is an exploded perspective view showing a configuration example of a nonaqueous electrolyte battery according to an embodiment of the present invention.

Fig. 7 is a sectional view taken along line I-I of the rolled electrode body shown in fig. 6.

Fig. 8 is a sectional view showing other configuration examples of the nonaqueous electrolyte battery according to the embodiment of the invention.

Fig. 9 is a sectional view showing other configuration examples of the nonaqueous electrolyte battery according to the embodiment of the invention.

Detailed Description

Embodiments according to the present invention are described below by referring to the drawings. The description is made in the following order.

1. First embodiment (nonaqueous electrolytic solution containing heteropolyacid salt compound according to the present invention)

Examples of (2)

2. Second embodiment (example of Using cylindrical nonaqueous electrolyte Battery)

3. Third embodiment (example of using a laminate film type nonaqueous electrolyte Battery)

4. Fourth embodiment (example of Using a laminate film type nonaqueous electrolyte Battery)

5. Fifth embodiment (example of using a Square nonaqueous electrolyte Battery)

6. Sixth embodiment (example of nonaqueous electrolyte Battery Using laminated electrode body)

7. Other embodiments

1. First embodiment

A nonaqueous electrolytic solution according to a first embodiment of the present invention will be described. The nonaqueous electrolytic solution according to the first embodiment of the invention is used for an electrochemical device such as a battery, for example. The nonaqueous electrolytic solution contains a solvent, an electrolyte salt, and a heteropolyacid salt compound. The electrolyte salt and the heteropolyacid salt compound may be dissolved in the solvent.

(1-1) Heteropoly acid salt Compound

The heteropolyacid salt compound according to the first embodiment of the present invention is represented by at least one of the following formula (I) having a Keggin structure and the following formula (II) having a Preyssler structure.

H_xA_y[BD₁₂O₄₀]·zH₂O (I)

In formula (I), A represents lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), aluminum (Al), ammonium (NH)₄) Ammonium or phosphonium salts; b represents phosphorus (P), silicon (Si), arsenic (As) or germanium (Ge); d represents at least one element selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), rhodium (Rh), cadmium (Cd), indium (In), tin (Sn), tantalum (Ta), tungsten (W), rhenium (Re), and thallium (Tl); and x, y and z are values falling within the ranges of 0. ltoreq. x.ltoreq.1, 2. ltoreq. y.ltoreq.4 and 0. ltoreq. z.ltoreq.5, respectively.

H_pA_q[B₅D₃₀O₁₁₀]·rH₂O (II)

In the formula (II)A represents lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), aluminum (Al), ammonium (NH)₄) Ammonium or phosphonium salts; b represents phosphorus (P), silicon (Si), arsenic (As) or germanium (Ge); d represents at least one element selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), rhodium (Rh), cadmium (Cd), indium (In), tin (Sn), tantalum (Ta), tungsten (W), rhenium (Re), and thallium (Tl); and p, q and r are values falling within the ranges of 0. ltoreq. p.ltoreq.5, 10. ltoreq. q15 and 0. ltoreq. r.ltoreq.15, respectively.

That is, in the formulas (I) and (II), in the heteropolyacid salt compound, the acid component (H in the formula (I))_xOr H in the formula (II)_p) The proton is not more than that of the salt of the heteropolyacid salt compound (A in the formula (I))_yOr A in the formula (II)_q) Half of that.

When the heteropolyacid salt compound represented by the formula (I) and/or the formula (II) is contained in the nonaqueous electrolytic solution, a coating called a stable SEI (solid electrolyte interface coating) is formed on the electrode surface, particularly the anode surface by charge/discharge at the initial stage of use. Since the coating layer derived from the heteropolyacid salt compound capable of intercalating and deintercalating Li has excellent Li ion permeability, it is considered that gas generation at the time of use at high temperatures can be reduced without deteriorating cycle characteristics while suppressing the reaction between the electrode and the nonaqueous electrolytic solution. And, in particular, when the heteropolyacid salt compound represented by the formula (II) having a Preyssler structure is used, it is more easily dissolved in the solvent of the battery and can be stably present in a wide pH range.

When the acid component is present in the nonaqueous electrolytic solution, its redox ability is strong, so that there is involved a problem that an undesirable side reaction such as decomposition and corrosion of the nonaqueous electrolytic solution may be caused. Also, when moisture is present in the nonaqueous electrolytic solution, there is involved a problem that a free acid derived from crystal water, for example, tetrahydrofuran or the like corrodes a current collector or a binder, and causes decomposition of an electrolyte salt.

Meanwhile, since the heteropolyacid salt compound according to the first embodiment of the present invention has a structure in which a part or all of protons are replaced (substituted) with the alkali metal cation, a free acid cannot be produced. Also, by using the heteropolyacid salt compound having an anion with a higher valence, even when it is in a state without crystal water, the heteropolyacid salt compound is easily dissolved in the nonaqueous electrolytic solution similarly to the heteropolyacid, and it becomes possible to obtain a stable structure. Inside the battery, the heteropolyacid salt compound having the highest valence in a stable structure in a wide pH range is easily reduced, thereby easily forming a coating layer electrochemically.

It is preferable that the content of moisture in the nonaqueous electrolytic solution, which causes decomposition of the electrolyte salt, is as small as possible. Specifically, it is preferable that the amount of moisture in the nonaqueous electrolytic solution is not more than 50 ppm. The amount of moisture can be measured, for example, by karl fischer method or the like.

Further, it is preferable that the content of an acid component in the nonaqueous electrolytic solution which causes decomposition of the nonaqueous electrolytic solution and corrosion of the metal material is as small as possible. Specifically, it is preferable that the amount of the acid component in the nonaqueous electrolytic solution is not more than 100 ppm. Here, the acid component means a protic acid such as HF. The amount of the acid component in the nonaqueous electrolytic solution can be measured, for example, by using an acid-base titration method or the like.

The heteropolyacid salt compound according to the first embodiment of the present invention is composed of a heteropolyacid as a condensate of two or more kinds of oxoacids (oxoacids). In the first embodiment according to the present invention, it is preferable that the heteropoly-acid has a structure in which it is easily dissolved in a solvent of a battery, such as a Keggin structure as in formula (I) and a Preyssler structure as in formula (II). Also, heteropoly acids having an Anderson (Anderson) structure or a Dawson (Dawson) structure in which the acid component has no more than half of the proton of the salt are preferable.

The heteropolyacid salt compound and the heteropolyacid constituting the heteropolyacid salt compound are a heteropolyacid salt compound and a heteropolyacid having a polyatomic group selected from the following element group (a); or a heteropoly acid salt compound having a polyatomic atom selected from the following element group (a) in which a part of polyatomic atoms are replaced with at least any one element selected from the following element group (b), and a heteropoly acid.

Element group (a): mo, W, Nb, V

Element group (b): ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Tc, Rh, Cd, In, Sn, Ta, Re, Tl, Pb

And, the heteropolyacid salt compound and the heteropolyacid are a heteropolyacid salt compound and a heteropolyacid having a heteroatom selected from the following element group (c); or a heteropoly acid salt compound and a heteropoly acid having a hetero atom selected from the following element group (c), in which a part of the hetero atom is replaced with at least any one element selected from the following element group (d).

Element group (c): B. al, Si, P, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As

Element group (d): H. be, B, C, Na, Al, Si, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Zr, Rh, Sn, Sb, Te, I, Re, Pt, Bi, Ce, Th, U, Np

Examples of the heteropoly acid contained in the heteropoly acid salt compound used in the first embodiment according to the present invention include heteropoly tungstic acids such as phosphotungstic acid and silicotungstic acid; and heteropolymolybdic acids such as phosphomolybdic acid and silicomolybdic acid. Also, as a material containing a plurality of kinds of multiple elements (elements), materials such as phosphovanadomolybdic acid, phosphotungstomolybdic acid, silicovanadomolybdic acid, and silicotungstomolybdic acid can be used.

Preferably, the heteropolyacid salt compound has a cation, for example, Li⁺、Na⁺、K⁺、Rb⁺、Cs⁺、R₄N⁺、R₄P⁺And the like, wherein R is H or a hydrocarbyl group having no more than 10 carbon atoms. And, the cation is more preferably Li⁺Tetra-n-butylammonium or tetra-n-butylphosphonium.

Examples of such a heteropolyacid salt compound include heteropolytungstic acid compounds such as sodium silicotungstate, sodium phosphotungstate, ammonium phosphotungstate, and tetra (tetra-n-butylphosphonium) silicotungstate. Also, examples of the heteropoly-acid compound include heteropolymolybdic acid compounds such as sodium phosphomolybdate, ammonium phosphomolybdate, and tri (tetra-n-butylammonium) phosphomolybdate. In addition, examples of the compound containing a plurality of polyacids include materials such as tris (tetra-n-ammonium) phosphotungstic molybdate. Such heteropoly acids or heteropoly acid compounds can be used in a mixture of two or more of them. Such heteropoly-acid or heteropoly-acid compound is easily dissolved in a solvent, is stable in a battery, and hardly causes adverse effects such as reaction with other materials.

Also, in the first embodiment according to the present invention, a polyacid compound may be used. As the polyacid compound, an isopolyacid compound may be used together with the heteropoly acid compound. Also, the isopolyacid compound tends to be slightly deteriorated in the effect per added weight as compared with the heteropoly acid compound. However, since the solubility of the isopolyacid compound in a polar solvent is low, when used in a positive electrode or a negative electrode, there are excellent aspects (situations) in coating properties such as viscoelasticity and its change with time, so that it has usefulness from an industrial point of view.

The polyacid compound according to the first embodiment of the invention, like the heteropolyacid salt compound, is a polyacid compound having a polyatomic atom selected from the following element group (a); or a polyacid compound having a polyatomic atom selected from the following element group (a) in which a part of polyatomic atoms are replaced with at least any one element selected from the following element group (b).

Element group (a): mo, W, Nb, V

Element group (b): ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Tc, Rh, Cd, In, Sn, Ta, Re, Tl, Pb

Examples of the polyacid contained in the polyacid compound used in the first embodiment according to the present invention include tungsten (VI) acid and molybdenum (VI) acid. Specific examples thereof include tungstic anhydride, molybdic anhydride and hydrates thereof. Examples of hydrates that may be used include as tungstic acid monohydrate (WO)₃·H₂O) ortho-tungstic acid (ortho-tungstic acid) (H)₂WO₄) Molybdic acid dihydrate (H)₄MoO₅、H₂MoO₄·H₂O or MoO₃·2H₂O) and as molybdic acid monohydrate (MoO)₃·H₂O) orthomolybdic acid (H)₂MoO₄). And, canTo use a tungstic anhydride having a hydrogen content smaller than that of metatungstic acid, paratungstic acid and the like which are isopolyacids as the above hydrate and eventually having a zero hydrogen content (WO)₃) (ii) a Molybdic anhydride (MoO) having a smaller hydrogen content than metamolybdic acid, paramolybdic acid, etc. and eventually having a zero hydrogen content₃) And so on.

The nonaqueous electrolytic solution contains at least one of the compounds represented by the aforementioned formulae (I) and (II). Also, a combination of two or more compounds represented by the formulae (I) and (II) may be used. By adding a polyacid salt compound having such a structure in which protons and moisture are removed to the nonaqueous electrolytic solution, it is possible to control the moisture content in the nonaqueous electrolytic solution and suppress the generation of free acid, regardless of the addition amount of the heteropolyacid salt compound.

Also, the content of the heteropolyacid salt compound composed of at least one of the compounds represented by the formulae (I) and (II) in the nonaqueous electrolytic solution is preferably 0.01% by weight or more and not more than 3% by weight from the viewpoint of battery swelling after initial charging, and more preferably 1.0% by weight or more and not more than 3.0% by weight from the viewpoint of battery swelling after each operation of initial charging and high-temperature storage. When the content of the heteropolyacid salt compound is too small, the formation of SEI is insufficient, so that the effect caused by the addition of the heteropolyacid salt compound can hardly be obtained. Also, too large a content of the heteropolyacid salt compound is not preferable because irreversible capacity by the reaction becomes too large, so that the battery capacity is lowered.

In addition, lithium hexafluorophosphate (LiPF), for example, may be used in combination₆) And lithium tetrafluoroborate (LiBF)₄) And adding to the nonaqueous electrolytic solution. Accordingly, since aluminum fluoride or the like derived from a lithium salt is generated, the occurrence of corrosion due to, for example, moisture and acid components in the heteropolyacid salt compound can be more effectively prevented.

In the heteropolyacid salt compound according to the first embodiment of the present invention, as shown by the formulae (I) and (II), the acid component (H in the formula (I))_xOr H in the formula (II)_p) Can be used in combination with salt (A in formula (I))_yOr in the formula (II)A of (A)_q) Are present together in the compound. Also, for example, as described previously, it is preferable that the amount of moisture and the amount of the acid component in the nonaqueous electrolytic solution are not more than 50ppm and not more than 100ppm, respectively. As long as the amount of moisture and the amount of acid component fall within the above ranges, a mixture of a salt-free heteropoly acid and the heteropoly acid salt compound according to the first embodiment of the present invention can be used.

(1-2) Synthesis method of Heteropoly acid salt Compound

Although the synthesis method of the heteropolyacid salt compound according to the first embodiment of the present invention is not particularly limited, examples of the synthesis method include a method of mixing a heteropolyacid with an acid salt, a hydroxide or the like; and a method of mixing tungsten oxide, molybdenum oxide and an acid salt. The heteropolyacid salt is isolated by methods such as crystallization isolation and vacuum drying. Also, the structure of the synthesized heteropolyacid salt compound can be confirmed by means of X-ray diffraction or UV or IR measurement.

Also, the nonaqueous electrolytic solution containing the heteropolyacid salt compound according to the first embodiment of the present invention may be prepared by mixing the solvent to be used for the nonaqueous electrolytic solution and the heteropolyacid, followed by dehydration by an azeotrope or using a drying agent, an acid component removal method by ion exchange, or other methods.

(1-3) constitution of nonaqueous electrolytic solution to which heteropolyacid salt compound is added

[ electrolyte salt ]

The electrolyte salt may, for example, comprise one or two or more light metal salts such as lithium salts. Examples of the lithium salt include lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium perchlorate (LiClO)₄) Lithium hexafluoroarsenate (LiAsF)₆) Lithium tetraphenylborate (LiB (C)₆H₅)₄) Lithium methane sulfonate (LiCH)₃SO₃) Lithium trifluoromethanesulfonate (LiCF)₃SO₃) Lithium aluminum tetrachloride (LiAlCl)₄) Dilithium hexafluorosilicate (Li)₂SiF₆) Lithium chloride (LiCl) and lithium bromide (LiBr). In particular, from lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium perchlorate(LiClO₄) And lithium hexafluoroarsenate (LiAsF)₆) At least one member of the group of (a) is preferred, and lithium hexafluorophosphate (LiPF)₆) Is more preferred. This is because the resistance of the nonaqueous electrolyte decreases. In particular, lithium hexafluorophosphate (LiPF) is preferable₆) Lithium tetrafluoroborate (LiBF) together₄). This is because a high effect can be obtained.

[ non-aqueous solvent ]

Examples of the nonaqueous solvent that can be used include Ethylene Carbonate (EC), Propylene Carbonate (PC), Butylene Carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methylethyl carbonate (EMC), methylpropyl carbonate (MPC), γ -butyrolactone, γ -valerolactone, 1, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 3-dioxane, 1, 4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl pivalate, ethyl pivalate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N-dimethylformamide, N-dimethylformamid, N-methylpyrrolidone, N-methyloxazolidinone, N' -dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, and dimethyl sulfoxide. This is because excellent capacity, cycle characteristics, and preservation characteristics can be obtained in an electrochemical device such as a battery provided with a nonaqueous electrolyte. These substances may be used alone or in a mixture with a plurality of them.

In particular, it is preferable to use a solvent containing at least one member selected from the group consisting of Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and Ethyl Methyl Carbonate (EMC) as a solvent. This is because sufficient effects can be obtained. In this case, in particular, it is preferable to use a solvent containing a mixture of ethylene carbonate or propylene carbonate each of which is a high-viscosity (high dielectric constant) solvent (e.g., a specific dielectric constant ε.gtoreq.30) and dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate each of which is a low-viscosity solvent (e.g., a viscosity ≦ 1mPa · s). This is because the dissociation property of the electrolyte salt and the mobility of the ions can be improved, so that higher effects can be obtained.

Preferably, the electrolyte contains a cyclic carbonate represented by the following formula (III) or (IV). A combination of two or more selected from the compounds represented by formulae (III) and (IV) may also be used.

In formula (III), each of R1 to R4 represents a hydrogen group, a halogen group, an alkyl group, or a halogenated alkyl group, with the proviso that at least one of R1 to R4 represents a halogen group or a halogenated alkyl group.

In formula (IV), each of R5 and R6 represents a hydrogen group or an alkyl group.

Examples of the cyclic carbonate having halogen represented by the formula (III) include 4-fluoro-1, 3-dioxolan-2-one, 4-chloro-1, 3-dioxolan-2-one, 4, 5-difluoro-1, 3-dioxolan-2-one, tetrafluoro-1, 3-dioxolan-2-one, 4-chloro-5-fluoro-1, 3-dioxolan-2-one, 4, 5-dichloro-1, 3-dioxolan-2-one, tetrachloro-1, 3-dioxolan-2-one, 4, 5-bistrifluoromethyl-1, 3-dioxolan-2-one, 4-trifluoromethyl-1, 3-dioxolan-2-one, 4, 5-difluoro-4, 5-dimethyl-1, 3-dioxolan-2-one, 4-difluoro-5-methyl-1, 3-dioxolan-2-one, 4-ethyl-5, 5-difluoro-1, 3-dioxolan-2-one, 4-fluoro-5-trifluoromethyl-1, 3-dioxolan-2-one, 4-methyl-5-trifluoromethyl-1, 3-dioxolan-2-one, 4-fluoro-4, 5-dimethyl-1, 3-dioxolan-2-one, 5- (1, 1-difluoroethyl) -4, 4-difluoro-1, 3-dioxolan-2-one, 4, 5-dichloro-4, 5-dimethyl-1, 3-dioxolan-2-one, 4-ethyl-5-fluoro-1, 3-dioxolan-2-one, 4-ethyl-4, 5-difluoro-1, 3-dioxolan-2-one, 4-ethyl-4, 5, 5-trifluoro-1, 3-dioxolan-2-one, and 4-fluoro-4-methyl-1, 3-dioxolan-2-one. These may be used alone or as a mixture of a plurality of them. Among them, 4-fluoro-1, 3-dioxolan-2-one and 4, 5-difluoro-1, 3-dioxolan-2-one are preferable. This is because not only are these substances easily available, but also a high effect can be obtained.

Examples of the cyclic carbonate having an unsaturated bond represented by the formula (IV) include vinylene carbonate (1, 3-dioxol-2-one), methylvinylene carbonate (4-methyl-1, 3-dioxol-2-one), ethylvinylene carbonate (4-ethyl-1, 3-dioxol-2-one), 4, 5-dimethyl-1, 3-dioxol-2-one, 4, 5-diethyl-1, 3-dioxol-2-one, 4-fluoro-1, 3-dioxol-2-one and 4-trifluoromethyl-1, 3-dioxol-2-one. These may be used alone or as a mixture of a plurality of them. Among them, vinylene carbonate is preferable. This is because not only the substance is easily available, but also a high effect can be obtained.

[ Polymer Compound ]

In the first embodiment according to the present invention, the nonaqueous electrolytic solution having the nonaqueous solvent and the electrolyte salt mixed therein may contain a retaining material containing a polymer compound to form a so-called gel.

A substance capable of gelling after adsorbing a solvent therein can be used as the polymer compound. Examples thereof include fluorocarbon-based high molecular compounds such as polyvinylidene fluoride and copolymers of vinylidene fluoride and hexafluoropropylene; ether-based high molecular compounds such as polyethylene oxide and crosslinked materials containing polyethylene oxide; and compounds containing polyacrylonitrile, polypropylene oxide or polymethyl methacrylate as a repeating unit. The polymer compound may be used alone or as a mixture of two or more of them.

In particular, a fluorocarbon-based polymer compound is desirable from the viewpoint of redox stability; and, in particular, a copolymer containing vinylidene fluoride and hexafluoropropylene as components is preferable. Also, the copolymer may contain, as components, monoesters of unsaturated dibasic acids such as monomethyl maleate, vinyl halides such as chlorotrifluoroethylene, cyclic carbonates of unsaturated compounds such as vinylene carbonate, epoxy group-containing acryloyl vinyl monomers (acryl vinyl monomers), and the like. This is because higher characteristics can be obtained.

The method for forming the gel-like electrolyte layer is described later.

< effects >

In the first embodiment according to the present invention, the heteropolyacid salt compound represented by at least one of the formulae (I) and (II) is contained in the nonaqueous electrolytic solution. This makes it possible to reduce the amount of water and acid components in the nonaqueous electrolytic solution. Thus, by using such a nonaqueous electrolytic solution for a nonaqueous electrolyte battery, a coating layer can be formed on the surface of the negative electrode, whereby an effect for suppressing a side reaction of the nonaqueous electrolytic solution can be obtained.

2. Second embodiment

A nonaqueous electrolyte battery according to a second embodiment of the present invention will be described. The nonaqueous electrolyte battery in the second embodiment according to the present invention is a cylindrical nonaqueous electrolyte battery.

(2-1) construction of nonaqueous electrolyte Battery

Fig. 1 shows a sectional configuration of a nonaqueous electrolyte battery according to a second embodiment of the present invention. Fig. 2 shows a part of the wound electrode body 20 shown in fig. 1 in an enlarged manner. The nonaqueous electrolyte battery is, for example, a lithium ion secondary battery in which the capacity of the negative electrode is expressed based on the intercalation and deintercalation of lithium as an electrode reactant.

[ entire construction of nonaqueous electrolyte Battery ]

In this nonaqueous electrolyte battery, a wound electrode body 20 in which a cathode 21 and an anode 22 are laminated and wound via a separator 23, and a pair of insulating plates 12 and 13 are mainly housed inside a substantially hollow cylindrical battery can 11. The battery structure using this cylindrical battery can 11 is referred to as a cylinder type.

The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are respectively disposed perpendicularly to the wound peripheral surface so as to interpose the wound electrode body 20 therebetween.

At the open end of the battery can 11, a battery cover 14 is mounted by caulking via a gasket 17 with a safety valve mechanism 15 and a positive temperature coefficient device (PTC device) 16 provided inside the battery cover 14, and the inside of the battery can 11 is hermetically sealed.

The battery cover 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery cover 14 via the positive temperature coefficient device 16. In this safety valve mechanism 15, when the internal pressure of the battery reaches a certain value or more due to internal short circuit, heating from the outside, or the like, the disk plate 15A is inverted, thereby cutting off the electrical connection between the battery cover 14 and the wound electrode body 20.

When the temperature rises, the positive temperature coefficient device 16 controls the current by increasing the resistance value, thereby preventing abnormal heat generation caused by a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is coated on the surface thereof.

For example, a center pin 24 is inserted into the center of the wound electrode body 20. In the wound electrode body 20, a positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21; and an anode lead 26 made of nickel (Ni) or the like is connected to the anode 22. The positive electrode lead 25 is electrically connected to the battery cover 14 by being welded to the safety valve mechanism 15; and the anode lead 26 is electrically connected to the battery can 11 by welding.

[ Positive electrode ]

The cathode 21 is, for example, a cathode in which a cathode active material layer 21B is provided on both surfaces of a cathode current collector 21A having a pair of surfaces opposed to each other. However, the cathode active material layer 21B may be provided on only one surface of the cathode current collector 21A. A coating layer derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is formed on the surface of the positive electrode. The deposit deposited by electrolysis of the heteropolyacid salt compound is contained in the formed coating layer by pre-charging or charging. The deposit comprises a polyacid and/or a polyacid compound. The deposit deposited on the positive electrode is formed depending on the amount of the heteropolyacid salt compound to be added to the battery system.

The positive electrode collector 21A is composed of, for example, a metal material such as aluminum, nickel, and stainless steel.

The cathode active material layer 21B contains one or two or more cathode materials capable of inserting and extracting lithium as a cathode active material, and may further contain other materials such as a binder and a conductive agent, if desired.

As a positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing compound is preferable. This is because a high energy density can be obtained. Examples of the lithium-containing compound include a composite oxide containing lithium and a transition metal element and a phosphate compound containing lithium and a transition metal element. Among them, a compound containing at least one member selected from the group consisting of cobalt, nickel, manganese, and iron as a transition metal element is preferable. This is because a higher voltage can be obtained.

Examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li)_xCoO₂) Lithium nickel composite oxide (Li)_xNiO₂) Lithium nickel cobalt composite oxide (Li)_xNi_1-zCo_zO₂(z<1) Lithium nickel cobalt manganese composite oxide (Li)_xNi_(1-v-w)Co_vMn_wO₂(v+w<1) And lithium manganese complex oxide (LiMn) each having a spinel-type structure₂O₄) Or lithium manganese nickel composite oxide (LiMn)_2-tNi_tO₄(t<2)). Among them, a composite oxide containing cobalt is preferable. This is because not only a high capacity but also excellent cycle characteristics can be obtained. In addition, examples of the phosphate compound containing lithium and a transition metal element include lithium iron phosphate compounds (LiFePO)₄) And lithium iron manganese phosphate compounds (LiFe)_1-uMn_uPO₄(u<1))。

Also, from the viewpoint that higher electrode filling performance and cycle characteristics can be obtained, the positive electrode material capable of inserting and extracting lithium may be formed as a composite particle obtained by coating the surface of a core particle composed of any of the above-described lithium-containing compounds with fine particles composed of any of other lithium-containing compounds.

In addition, examples of the cathode material capable of inserting and extracting lithium include oxides such as titanium oxide, vanadium oxide, and manganese dioxide; disulfides such as titanium disulfide and molybdenum sulfide; chalcogenides, such as niobium selenide; sulfur; and conductive polymers such as polyaniline and polythiophene. Needless to say, the positive electrode material capable of inserting and extracting lithium may be other materials than those described above. Also, the series of positive electrode materials listed above may be a mixture of two or more of them in any combination.

[ negative electrode ]

The anode 22 is, for example, an anode in which an anode active material layer 22B is provided on both surfaces of an anode current collector 22A having a pair of surfaces opposed to each other. However, the anode active material layer 22B may be provided on only one surface of the anode current collector 22A. A coating layer derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is formed on the surface of the anode. The coating formed comprises a deposit which is deposited in a three-dimensional network structure after electrolysis of the heteropolyacid salt compound by pre-charging or charging. The coating layer is formed on at least a part of a surface of the negative electrode, and includes an amorphous polyacid and/or a polyacid compound containing one or more kinds of multiple elements, and the amorphous polyacid and/or the polyacid compound contains an electrolytic solution and takes a gel form.

The gel-like coating formed on the surface of the anode according to the second embodiment of the present invention, which contains an amorphous polyacid and/or polyacid compound composed of one or more kinds of multielement, can be confirmed, for example, by SEM (scanning electron microscope), as shown in fig. 3. Fig. 3 is an SEM image of the surface of the negative electrode after charging, and is a photograph taken after washing the electrolyte and then drying.

Also, the deposition of the amorphous polyacid and/or polyacid compound may be confirmed based on the structural analysis of the coating formed on the surface of the anode by X-ray absorption fine structure (XAFS) analysis and the molecular chemical information by time-of-flight type secondary ion mass spectrometry (ToF-SIMS).

Fig. 4 shows an example of secondary ion spectrum by time-of-flight type secondary ion mass spectrometry (ToF-SIMS) on the surface of a negative electrode of a nonaqueous electrolyte battery, in which a negative electrode coating according to a second embodiment of the present invention is formed by adding silicotungstic acid to a battery system and charging the battery. As can be noted from fig. 4, there are molecules containing tungsten (W) and oxygen (O) as constituent elements.

And, fig. 5 shows an example of a radial structure function of a W — O bond obtained by fourier transform of a spectrum by X-ray absorption fine structure (XAFS) analysis on a surface of a negative electrode of a nonaqueous electrolyte battery, in which a negative electrode coating according to a second embodiment of the present invention is formed by adding silicotungstic acid to a battery system and charging the battery. Also, fig. 5 shows tungstic acid as a polyacid that may be used in accordance with the second embodiment of the present invention, together with the analysis results of the anode coating (WO)₃Or WO₂) And silicotungstic acid (H) as a heteropolyacid which can be used in the second embodiment according to the present invention₄(SiW₁₂O₄₀)·26H₂O) is used as an example of the radial structure function of the W-O bond of each of the above.

As can be noted from FIG. 5, the peak L1 of the deposit on the surface of the negative electrode had a peak value in the range of being in contact with silicotungstic acid (H), respectively₄(SiW₁₂O₄₀)·26H₂O), tungsten dioxide (WO)₂) And tungsten trioxide (WO)₃) Peaks L2, L3 and L4 in different positions and having different structures. Tungsten trioxide, both of which are typical tungsten oxides (WO)₃) And tungsten dioxide (WO)₂) And silicotungstic acid (H) as a raw material according to the second embodiment of the invention₄(SiW₁₂O₄₀)·26H₂O), the main peak exists in the range of 1.0 to 2.0 angstroms in consideration of the radial structure function, and it can also be confirmed that the peak is in the range of 2.0 to 4.0 angstroms.

On the other hand, in the distribution of W — O bond distances of the polyacid mainly composed of tungstic acid deposited on each of the cathode and the anode in the second embodiment according to the present invention, although the peak was confirmed to be in the range of 1.0 to 2.0 angstroms, no different peak comparable to that in the peak L1 was found outside the above range. That is, substantially no peak was observed in the range exceeding 3.0 angstroms. In such a case, it was confirmed that the deposit on the surface of the anode was amorphous.

The anode current collector 22A is composed of, for example, a metal material such as copper, nickel, and stainless steel.

The anode active material layer 22B contains one or two or more anode materials capable of inserting and extracting lithium as an anode active material, and may further contain other materials such as a binder and a conductive agent, if desired. In this case, it is preferable that the negative electrode material capable of inserting and extracting lithium has a rechargeable capacity larger than the discharge capacity of the positive electrode. The details regarding the binder and the conductive agent are the same as those in the positive electrode.

Examples of the anode material capable of intercalating and deintercalating lithium include carbon materials. Examples of such carbon materials include graphitizable carbon, graphitizable carbon having (002) plane spacing of 0.37nm or more, and graphite having (002) plane spacing of not more than 0.34 nm. More specifically, pyrolytic carbon, coke, glassy carbon fiber, an organic polymer compound fired body, activated carbon, and carbon black are exemplified. Examples of coke include pitch coke, needle coke, and petroleum coke, among others. The organic high molecular compound fired body as referred to herein is a substance obtained by firing a phenol resin, a furan resin, or the like at an appropriate temperature through carbonization. The carbon material is preferable because the change in crystal structure accompanying the intercalation and deintercalation of lithium is very small, and therefore a high energy density can be obtained, excellent cycle characteristics can be obtained, and the carbon material also functions as a conductive agent. The shape of the carbon material may be any of fibrous, spherical, granular, or flaky (scaly).

Examples of the anode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and containing at least one member selected from the group consisting of metal elements and semimetal elements as a constituent element, in addition to the above-described carbon material. This is because a high energy density can be obtained. Such an anode material may be a simple substance, an alloy, or a compound of a metal element or a semimetal element, or may be a material having one kind or two or more kinds of phases in at least a part thereof. In addition to alloys composed of two or more metal elements, "alloys" as referred to herein also include alloys comprising one or more metal elements and one or more semimetal elements. Also, "alloys" may contain non-metallic elements. Examples of the structure thereof include a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and a structure in which two or more of them coexist.

Examples of the metal element or the semimetal element include metal elements or semimetal elements capable of forming an alloy together with lithium. Specific examples thereof include magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), and platinum (Pt). Among them, at least one member selected from silicon and tin is preferable, and silicon is more preferable. This is because silicon and tin have a large ability to intercalate and deintercalate lithium, so that a high energy density can be obtained.

Examples of the anode material containing at least one member selected from silicon and tin include a simple substance, an alloy, or a compound of silicon; a simple substance, alloy or compound of tin; and a material having one or two or more phases in at least a portion thereof.

Examples of the alloy of silicon include alloys containing at least one member selected from the group consisting of tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr) as a second constituent element other than silicon. Examples of the alloy of tin include alloys containing at least one member selected from the group consisting of silicon (Si), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr) as a second constituent element other than tin (Sn).

Examples of the compounds of tin or silicon include compounds containing oxygen (O) or carbon (C), and these compounds may further contain the above-described second constituent element in addition to tin (Sn) or silicon (Si).

As the anode material containing at least one member selected from silicon (Si) and tin (Sn), for example, a material containing tin (Sn) as a first constituent element, and a second constituent element and a third constituent element other than the tin (Sn) is particularly preferable. Needless to say, the anode material may be used together with the above-described anode material. The second constituent element is at least one member selected from the group consisting of cobalt (Co), iron (Fe), magnesium (Mg), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), indium (In), cerium (Ce), hafnium (Hf), tantalum (Ta), tungsten (W), bismuth (Bi), and silicon (Si). The third constituent element is at least one member selected from the group consisting of boron (B), carbon (C), aluminum (Al), and phosphorus (P). This is because when the second constituent element and the third constituent element are contained, the cycle characteristics can be improved.

In particular, the anode material is preferably an SnCoC-containing material that contains tin (Sn), cobalt (Co), and carbon (C) as constituent elements, and has a content of carbon (C) in a range of 9.9% by mass or more and not more than 29.7% by mass, and a ratio of cobalt (Co) to the sum of tin (Sn) and cobalt (Co) (Co/(Sn + Co)) in a range of 30% by mass or more and not more than 70% by mass. This is because not only a high energy density but also excellent cycle characteristics can be obtained within the above composition range.

The SnCoC-containing material may further contain other constituent elements, if desired. As other constituent elements, for example, silicon (Si), iron (Fe), nickel (Ni), chromium (Cr), indium (In), niobium (Nb), germanium (Ge), titanium (Ti), molybdenum (Mo), aluminum (Al), phosphorus (P), gallium (Ga), and bismuth (Bi) are preferable. The SnCoC-containing material may contain two or more of these elements. This is because the capacity characteristic or the cycle characteristic can be greatly improved.

The SnCoC-containing material has a phase containing tin (Sn), cobalt (Co), and carbon (C), and preferably the phase has a low crystalline structure or an amorphous structure (amorphous structure). Further, in the SnCoC-containing material, at least a part of carbon as a constituent element is preferably combined with a metal element or a semimetal element as another constituent element. This is because although it is considered that the cycle characteristics are lowered due to aggregation or crystallization of tin (Sn) or the like, such aggregation or crystallization can be suppressed when carbon is combined with other elements.

Examples of the measurement method for checking the binding state of an element include X-ray photoelectron spectroscopy (XPS). In this XPS, with graphite, in an energy correction device such that the peak of the 4f orbital of a gold atom (Au4f) is obtained at 84.0eV, the peak of the 1s orbital of carbon (C1s) appears at 284.5 eV. Also, with respect to the surface contamination carbon, the peak of the 1s orbital (C1s) of the carbon appears at 284.8 eV. In contrast, when the charge density of the carbon element is high, for example, when carbon is combined with a metal element or a semimetal element, the peak of C1s appears in a region smaller than 284.5 eV. That is, when the peak of the synthetic wave of C1s obtained with respect to the SnCoC-containing material appears in a region smaller than 284.5eV, at least a part of carbon (C) contained in the SnCoC-containing material is bonded with a metal element or a semimetal element as other constituent element.

In XPS measurements, for example, the peak of C1s is used to correct the energy axis of the spectrum. In general, since surface contamination carbon exists on the surface, the peak of C1s of the surface contamination carbon is fixed at 284.8eV, and this peak is used as an energy reference. In the XPS measurement, since the waveform of the peak of C1s is obtained as a form including the peak of the surface contamination carbon and the peak of carbon in the SnCoC-containing material, the peak of the surface contamination carbon and the peak of carbon in the SnCoC-containing material are separated from each other by analysis using, for example, a commercially available software program. In the analysis of the waveform, the position of the main peak existing on the lowest binding energy side was used as an energy reference (284.8 eV).

Also, examples of the anode material capable of inserting and extracting lithium include metal oxides and high molecular compounds each of which is capable of inserting and extracting lithium. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide; and examples of the high molecular compound include polyacetylene, polyaniline, and polypyrrole.

The negative electrode material capable of intercalating and deintercalating lithium may be other materials than those described above. Also, the anode material enumerated above may be a mixture of two or more of them in any combination.

The anode active material layer 22B may be formed, for example, by any one of a gas phase method, a liquid phase method, a spray method, a firing method, or a coating method, or a combination method of two or more of these methods. When the anode active material layer 22B is formed by employing a gas phase method, a liquid phase method, a spray method, a firing method, or a combination method of two or more of these methods, it is preferable that the anode active material layer 22B and the anode current collector 22A are alloyed on at least a part of the interface therebetween. Specifically, it is preferable that, at the interface, the constituent elements of the anode current collector 22A are diffused into the anode active material layer 22B, the constituent elements of the anode active material layer 22B are diffused into the anode current collector 22A, or these constituent elements may be mutually diffused into each other. This is because not only the cracking (destruction) due to the expansion and contraction of the anode active material layer 22B accompanying the charge/discharge can be suppressed, but also the electron conductivity between the anode active material layer 22B and the anode current collector 22A can be improved.

Examples of the vapor phase method include a physical deposition method and a chemical deposition method, specifically, a vacuum vapor deposition method, a sputtering method, an ion plating method, a laser ablation (ablation) method, a thermal Chemical Vapor Deposition (CVD) method, and a plasma chemical vapor deposition method. As the liquid phase method, known techniques such as electroplating (electrolytic plating) and electroless plating can be employed. The firing method as referred to herein is, for example, a method in which after a particulate anode active material is mixed with a binder or the like, the mixture is dispersed in a solvent and coated, and then the coated material is subjected to heat treatment at a temperature higher than the melting point of the binder or the like. As for the firing method, a known technique can also be utilized, and examples thereof include an atmosphere firing method, a reaction firing method, and a hot press firing method.

[ separator ]

The separator 23 separates the cathode 21 and the anode 22 from each other, and allows lithium ions to pass therethrough while preventing a current short circuit due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, and polyethylene; porous films made of ceramics, and the like, and a laminate of two or more of these porous films may also be used. The separator 23 may be impregnated with the electrolytic solution according to the above-described first embodiment of the present invention.

(2-2) method for producing nonaqueous electrolyte Battery

The above-described nonaqueous electrolyte battery can be manufactured in the following manner.

[ production of Positive electrode ]

First, the positive electrode 21 is manufactured. For example, a positive electrode material, a binder, and a conductive agent are mixed to form a positive electrode mixture, which is then dispersed in an organic solvent to form a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is uniformly coated on both surfaces of the positive electrode collector 21A by a doctor blade, a bar coater, or the like, and then dried. Finally, the coating layer is subjected to compression molding by a roll press or the like, and simultaneously heated if necessary, thereby forming the positive electrode active material layer 21B. In this case, the press molding may be repeated a plurality of times.

[ production of negative electrode ]

Next, the anode 22 is manufactured. For example, a negative electrode material and a binder and optionally a conductive agent are mixed to form a negative electrode mixture, which is then dispersed in an organic solvent to form a paste-like negative electrode mixture slurry. Subsequently, the anode mixture slurry is uniformly coated on both surfaces of the anode current collector 22A by a doctor blade, a bar coater, or the like, and then dried. Finally, the coating layer is subjected to press molding by a roll press or the like, and simultaneously heated if necessary, thereby forming the anode active material layer 22B.

[ Assembly of nonaqueous electrolyte Battery ]

Next, the cathode lead 25 is mounted in the cathode current collector 21A by welding or the like, and the anode lead 26 is also mounted in the anode current collector 22A by welding or the like. After that, the cathode 21 and the anode 22 are wound via the separator 23; welding the front end of the positive electrode lead 25 to the safety valve mechanism 15; and the front end of the anode lead 26 is also welded to the battery can 11. Then, the wound cathode 21 and anode 22 are interposed between the pair of insulating plates 12 and 13 and accommodated inside the battery can 11. After the cathode 21 and the anode 22 are housed in the battery can 11, the nonaqueous electrolytic solution according to the first embodiment of the invention is injected into the battery can 11 and impregnated in the separator 23. Thereafter, the battery cover 14, the safety valve mechanism 15, and the positive temperature coefficient device 16 are fixed to the open end of the battery can 11 after being caulked via the gasket 17. The nonaqueous electrolyte battery shown in fig. 2 and 3 is thus completed.

In such a nonaqueous electrolyte battery, at the time of initial charging, at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) contained in the nonaqueous electrolytic solution is electrolyzed and deposited, thereby forming a coating layer on the surface of the negative electrode. Due to the fact that the nonaqueous electrolytic solution contains at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II), the compound capable of intercalating and deintercalating lithium ions forms a stable SEI coating on the negative electrode by charge/discharge at the initial stage of use, thereby suppressing decomposition of the solvent and the electrolyte salt in the nonaqueous electrolytic solution. The SEI coating formed by the heteropoly acid and/or the heteropoly acid compound is inorganic and strong, and at the same time, the resistance at the time of intercalating and deintercalating lithium ions is small, and thus it can be considered that deterioration of capacity and the like is hardly caused. Further, it is considered that when a monofluorophosphate and/or a difluorophosphate which is close to a lithium salt in the electrolytic solution is added together with a heteropoly acid and/or a heteropoly acid compound, decomposition of a main electrolyte salt is greatly suppressed, whereby an SEI coating having low resistance can be formed.

Due to the fact that the electrolytic solution in which at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is dissolved is impregnated into the anode active material layer 22B, a compound derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) can be deposited within the anode active material layer 22B by charging or precharging. Accordingly, a compound derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) may be present in the anode active material particles.

Also, due to the fact that the electrolytic solution in which at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is dissolved is impregnated into the positive electrode active material layer 21B, the compound derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) can be deposited within the positive electrode active material layer 21B by charging or precharging. Accordingly, a compound derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) may be present in the positive electrode active material particles.

The presence or absence of a compound derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) in the anode coating layer can be confirmed, for example, by X-ray photoelectron spectroscopy (XPS) analysis or time-of-flight secondary ion mass spectrometry (ToF-SIMS). In this case, the cell was disassembled and then rinsed with dimethyl carbonate. This is done in order to remove the solvent component having low volatility and the electrolyte salt present on the surface. It is desirable to take samples in an inert atmosphere if this is possible at all.

< effects >

In a second embodiment according to the present invention, at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is contained in the nonaqueous electrolytic solution. Accordingly, not only deterioration of battery characteristics at the time of initial charging but also side reaction of the electrode active material and the nonaqueous electrolytic solution in a high temperature environment can be suppressed, so that battery characteristics can be improved. The addition of the heteropolyacid salt compound according to the second embodiment of the present invention can be suitably used for the primary battery and the secondary battery, because the effect can be obtained at the time of initial charging and also at the time of high-temperature storage.

3. Third embodiment

A nonaqueous electrolyte battery according to a third embodiment of the present invention will be described. The nonaqueous electrolyte battery according to the third embodiment of the invention is a laminate film type nonaqueous electrolyte battery packaged by a laminate film.

(3-1) construction of nonaqueous electrolyte Battery

A nonaqueous electrolyte battery according to a third embodiment of the present invention will be described. Fig. 6 is an exploded perspective configuration example of a nonaqueous electrolyte battery according to a third embodiment of the invention; and fig. 7 shows a cross section along the line I-I of the rolled electrode body 30 shown in fig. 6 in an enlarged manner.

The nonaqueous electrolyte battery has a configuration in which the wound electrode body 30, to which the positive electrode lead 31 and the negative electrode lead 32 are mainly mounted, is housed inside a film-shaped package member 40. The battery structure using this film-shaped package member 40 is called a laminate film type.

For example, each of the positive electrode lead 31 and the negative electrode lead 32 is drawn out in the same direction from the inside toward the outside of the package member 40. The cathode lead 31 is composed of, for example, a metal material such as aluminum, and the anode lead 32 is composed of, for example, a metal material such as copper, nickel, and stainless steel. Such a metal material is formed in a sheet shape or a network shape, for example.

The packing member 40 is constituted by, for example, an aluminum laminated film obtained by bonding a nylon film, an aluminum foil, and a polyethylene film in this order. For example, this package member 40 has a structure in which respective outer edge portions of two rectangular aluminum laminated films are adhered to each other by fusion or with an adhesive in such a manner that a polyethylene film is disposed opposite to the wound electrode body 30.

In order to prevent the occurrence of the intrusion of the external air, a contact film 41 is interposed between the package member 40 and each of the cathode lead 31 and the anode lead 32. The contact film 41 is composed of a material having adhesiveness to each of the cathode lead 31 and the anode lead 32. Examples of such materials include polyolefin resins such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

The package member 40 may also be constituted by a laminate film having other laminate structures, or by a polymer film such as a polypropylene film or a metal film instead of the above-described aluminum laminate film.

Fig. 7 shows a sectional configuration along the line I-I of the rolled electrode body 30 shown in fig. 6. The wound electrode body 30 is a wound electrode body prepared by laminating a cathode 33 and an anode 34 via a separator 35 and an electrolyte 36 and winding the laminate, and the outermost periphery thereof is protected by a protective tape 37.

The cathode 33 is, for example, a cathode in which a cathode active material layer 33B is provided on both surfaces of a cathode current collector 33A.

The anode 34 is, for example, an anode in which an anode active material layer 34B is provided on both surfaces of an anode current collector 34A, and a coating derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is formed on the anode surface. In the formed coating layer, the deposit deposited by electrolysis of the heteropolyacid salt compound takes a three-dimensional structure, and when the nonaqueous electrolytic solution is contained in the structure within the battery system, a gel-like coating layer containing an amorphous polyacid is formed. The cathode 33 and the anode 34 are provided in such a manner that the anode active material layer 34B and the cathode active material layer 33B are opposed to each other. The configurations of the cathode current collector 33A, the cathode active material layer 33B, the anode current collector 34A, the anode active material layer 34B, and the separator 35 are the same as those of the cathode current collector 21A, the cathode active material layer 21B, the anode current collector 22A, the anode active material layer 22B, and the separator 23 according to the second embodiment of the present invention, respectively.

The electrolyte 36 contains the electrolytic solution according to the first embodiment of the present invention and a polymer compound capable of holding the electrolytic solution therein, and is a so-called gel-like electrolyte. The gel-like electrolyte is preferable because not only high ion conductivity (for example, 1mS/cm or more at room temperature) can be obtained, but also occurrence of liquid leakage can be prevented.

(3-2) method for producing nonaqueous electrolyte Battery

The nonaqueous electrolyte battery is manufactured by, for example, the following three manufacturing methods (first to third manufacturing methods).

(3-2-1) first production method

In the first manufacturing method, first, for example, the cathode active material layer 33B is formed on both surfaces of the cathode current collector 33A to manufacture the cathode 33, and the anode active material layer 34B is formed on both surfaces of the anode current collector 34A to manufacture the anode 34, respectively in accordance with the same manufacturing steps of the cathode 21 and the anode 22 according to the second embodiment of the present invention.

Subsequently, a precursor solution containing the electrolytic solution according to the first embodiment of the present invention, the polymer compound, and the solvent is prepared and coated on each of the cathode 33 and the anode 34, and then the solvent is volatilized to form the gel-like electrolyte 36. Subsequently, the cathode lead 31 is mounted in the cathode current collector 33A, and the anode lead 32 is also mounted in the anode current collector 34A.

Subsequently, the cathode 33 and the anode 34, each having the nonaqueous electrolyte 36 formed thereon, are laminated via the separator 35, the laminate is wound in the longitudinal direction thereof, and then the protective tape 37 is adhered to the outermost peripheral portion thereof, thereby producing the wound electrode body 30. Finally, for example, the wound electrode body 30 is interposed between two package members 40 in a film shape, and outer edge portions of the package members 40 are adhered to each other by thermal fusion bonding or the like, thereby enclosing the wound electrode body 30 therein. At this time, the contact film 41 is inserted between each of the positive electrode lead 31 and the negative electrode lead 32 and the package member 40. Thereby completing the nonaqueous electrolyte battery.

(3-2-2) second production method

In the second manufacturing method, first, the cathode lead 31 is installed in the cathode 33, and the anode lead 32 is also installed in the anode 34. Subsequently, the cathode 33 and the anode 34 are laminated via the separator 35, the laminate is wound in the longitudinal direction thereof, and thereafter, the protective tape 37 is adhered to the outermost peripheral portion thereof, thereby manufacturing a wound body as a precursor of the wound electrode body 30.

Subsequently, the roll is interposed between two film-shaped package members 40, and outer edge portions other than one side are adhered to each other by thermal fusion or the like, thereby accommodating the roll in a bag-shaped package member 40. Subsequently, an electrolyte composition containing the electrolytic solution according to the first embodiment of the present invention, a monomer as a raw material of the polymer compound, a polymerization initiator, and optionally other materials such as a polymerization inhibitor is prepared and injected into the bag-shaped package member 40, and thereafter, the opening of the package member 40 is hermetically sealed by thermal fusion bonding or the like. Subsequently, the monomer is thermally polymerized to prepare a polymer compound, thereby forming the gel-like electrolyte 36. Thereby completing the nonaqueous electrolyte battery.

(3-2-3) third production method

In the third manufacturing method, first, a roll is formed and contained in the bag-like package member 40 in the same manner as the above-described second manufacturing method except that the separator 35 having the polymer compound coated on both surfaces thereof is used.

Examples of the high molecular compound coated on the separator 35 include a polymer composed of vinylidene fluoride as a component, that is, a homopolymer, a copolymer, a multipolymer, or the like. Specific examples thereof include polyvinylidene fluoride; a binary copolymer composed of vinylidene fluoride and hexafluoropropylene as components; and a terpolymer composed of vinylidene fluoride, hexafluoropropylene, and chlorotrifluoroethylene as components.

The polymer compound may contain one or two or more other polymer compounds and the above-mentioned polymer composed of vinylidene fluoride as a component. Subsequently, the electrolytic solution according to the first embodiment of the present invention is prepared and injected into the inside of the package member 40, and thereafter, the opening of the package member 40 is hermetically sealed by thermal fusion bonding or the like. Finally, after heating, the separator 35 is brought into close contact with each of the positive electrode 33 and the negative electrode 34 via the polymer compound while a weight is applied to the package member 40. Accordingly, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte 36. Thereby completing the nonaqueous electrolyte battery.

When the nonaqueous electrolyte battery manufactured by any one of the above-described first to third manufacturing methods is pre-charged or charged, a coating derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is formed on the surface of the negative electrode.

< effects >

In the third embodiment according to the present invention, the same effects as those in the second embodiment according to the present invention are produced.

4. Fourth embodiment

A nonaqueous electrolyte battery according to a fourth embodiment of the invention will be described. The nonaqueous electrolyte battery according to the fourth embodiment of the invention is a laminate film type nonaqueous electrolyte battery packaged by a laminate film and is the same as the nonaqueous electrolyte battery according to the third embodiment of the invention except that the electrolytic solution according to the first embodiment of the invention is used as it is (directly). As a result, hereinafter, the configuration thereof is described focusing on points different from those in the third embodiment according to the present invention.

(4-1) construction of nonaqueous electrolyte Battery

In the nonaqueous electrolyte battery according to the fourth embodiment of the present invention, an electrolytic solution is used instead of the gel-like electrolyte 36. As a result, the wound electrode body 30 has a configuration in which the electrolyte 36 is omitted, and the electrolytic solution is impregnated in the separator 35.

(4-2) method for producing nonaqueous electrolyte Battery

The nonaqueous electrolyte battery is manufactured, for example, in the following manner.

First, for example, a positive electrode active material, a binder, and a conductive agent are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. Subsequently, the cathode mixture slurry is coated on both surfaces of the cathode current collector 33A and dried, and then the resultant is subjected to press molding to form the cathode active material layer 33B. Thereby, the positive electrode 33 is manufactured. Subsequently, the cathode lead 31 is joined to the cathode current collector 33A, for example, by, for example, ultrasonic welding, spot welding, or the like.

Also, for example, an anode material and a binder are mixed to prepare an anode mixture, which is then dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare an anode mixture slurry. Subsequently, the anode mixture slurry is coated on both surfaces of the anode current collector 34A and dried, and then the resultant is subjected to press molding to form the anode active material layer 34B. Thereby, the anode 34 was manufactured. Subsequently, the anode lead 32 is joined to the anode current collector 34A by, for example, ultrasonic welding, spot welding, or the like.

Subsequently, the cathode 33 and the anode 34 are wound via the separator 35; placing the resultant in a package 40; and thereafter, the electrolytic solution according to the first embodiment of the present invention is injected, followed by hermetically sealing the package member 40. The nonaqueous electrolyte battery shown in fig. 6 and 7 was thus obtained.

< effects >

In the fourth embodiment according to the present invention, the same effects as those in the second embodiment according to the present invention are produced.

5. Fifth embodiment

A configuration example of the nonaqueous electrolyte battery 20 according to the fifth embodiment of the invention is described. As shown in fig. 8, the nonaqueous electrolyte battery 20 according to the fifth embodiment of the present invention has a rectangular shape.

The nonaqueous electrolyte battery 20 is manufactured in the following manner. As shown in fig. 8, first, the wound electrode body 53 is housed in a package case 51 which is a rectangular case made of metal such as aluminum (Al), iron (Fe), or the like.

Then, the electrode pin 54 provided on the battery cover 52 and the electrode terminal 55 led out from the wound electrode body 53 are connected to each other, followed by sealing by the battery cover 52. Thereafter, an electrolyte containing at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is injected from the electrolyte injection port 56, followed by sealing by the sealing member 57. By charging or pre-charging the manufactured battery, a nonaqueous electrolyte battery 20 according to a fifth embodiment of the present invention is completed, in which nonaqueous electrolyte battery 20 a compound derived from at least one of the heteropolyacid salt compounds represented by the formulae (I) and (II) is deposited on the surface of the negative electrode.

The wound electrode body 53 is obtained by laminating a cathode and an anode via a separator and winding the laminate. Since the cathode, the anode, the separator, and the electrolyte are the same as those in the first embodiment according to the present invention, detailed descriptions thereof are omitted.

< effects >

According to the nonaqueous electrolyte battery 20 according to the fifth embodiment of the present invention, the generation of gas of the electrolytic solution can be suppressed, and the occurrence of rupture due to the increase in the internal pressure caused by the generation of gas can be prevented.

6. Sixth embodiment

A nonaqueous electrolyte battery according to a sixth embodiment of the invention will be described. The nonaqueous electrolyte battery according to the sixth embodiment of the invention is a laminate film type nonaqueous electrolyte battery in which an electrode body is formed by laminating a positive electrode and a negative electrode and is packaged by a laminate film, and is the same as that in the third embodiment of the invention except for the configuration of the electrode body. For this reason, only the electrode body according to the sixth embodiment of the invention is described hereinafter.

[ Positive and negative electrodes ]

As shown in fig. 9, the positive electrode 61 is obtained by forming positive electrode active material layers on both surfaces of a rectangular positive electrode collector. The positive electrode collector of the positive electrode 61 is preferably formed integrally with the positive electrode terminal. Also, the anode 62 is similarly manufactured by forming an anode active material layer on a rectangular anode current collector.

The positive electrode 61 and the negative electrode 62 are laminated in this order of the positive electrode 61, the separator 63, the negative electrode 62, and the separator 63, thereby forming a laminated electrode body 60. In the laminated electrode body 60, the laminated state of the electrodes can be maintained by bonding an insulating tape or the like. The laminate electrode body 60 is packaged by a laminate film or the like and hermetically sealed in the battery together with the nonaqueous electrolytic solution, and a gel electrolyte may be used instead of the nonaqueous electrolytic solution.

Examples

The present invention is specifically described below with reference to the following examples, but it should not be construed that the present invention is limited to these examples. In the following description, the mass of the heteropoly-acid is defined as a value obtained by subtracting the mass of bound water that the heteropoly-acid has; and the mass of the heteropolyacid salt compound is defined as a value obtained by subtracting the mass of the bound water which the heteropolyacid salt compound has.

The heteropoly acid or heteropoly acid compound used in the following examples 1 and 2 is as follows.

A compound A: lithium phosphotungstate with Keggin structure

Compound B: lithium silicotungstate with Keggin structure

Compound C: tetrabutylammonium silicotungstate with Keggin structure

Compound D: tetrabutylphosphonium silicotungstic acid with Keggin structure

Compound E: phosphotungstic acid heptahydrate with Keggin structure

Compound F: silicotungstic acid heptahydrate with Keggin structure

Compound G: triacontastic acid phosphotungstic acid hydrate with Keggin structure

Compound H: silicotungstic acid thirty hydrate with Keggin structure

[ example 1]

In example 1, the characteristics of the laminate film type battery were evaluated by changing the kind of the heteropolyacid salt compound to be added.

< examples 1 to 1>

[ production of Positive electrode ]

94 parts by mass of lithium cobaltate (LiCoO) as a positive electrode active material was added₂) 3 parts by mass of graphite as a conductive agent and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed, and then N-methylpyrrolidone was added thereto to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was uniformly coated on both surfaces of a 10 μm-thick aluminum (Al) foil serving as a positive electrode current collector, and after drying, the resultant was press-molded by a roll press machine to form a positive electrode sheet in which a positive electrode active material layer having a bulk density of 3.40g/cc was formed. Finally, the positive electrode sheet was cut into a shape of 50mm wide and 300mm long, and a positive electrode lead made of aluminum (Al) was attached to the end of the positive electrode current collector by welding, thereby manufacturing a positive electrode.

[ production of negative electrode ]

97 parts by mass of mesocarbon microbeads (MCMB) as a negative electrode active material and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed, and then N-methylpyrrolidone was added thereto to obtain a negative electrode mixture slurry. Subsequently, the anode mixture slurry was uniformly coated on both surfaces of a 10 μm-thick copper foil serving as an anode current collector, and after drying, the resultant was press-molded by a roll press to form an anode sheet in which an anode active material layer having a bulk density of 1.80g/cc was formed. Finally, the negative electrode sheet was cut into a shape of 50mm wide and 300mm long, and a negative electrode lead made of nickel (Ni) was mounted on the end of a negative electrode current collector by welding, thereby manufacturing a negative electrode.

[ preparation of nonaqueous electrolyte solution ]

0.8mol/kg of lithium hexafluorophosphate (LiPF) as an electrolyte salt was added₆) And 1.0% by weight of compound a as a heteropolyacid salt compound was dissolved in a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 5/5.

The moisture content (water content) in the nonaqueous electrolytic solution as measured by the Karl Fischer method was 18 ppm. And the acid content in the nonaqueous electrolytic solution as measured by an acid-base titration method was 80 ppm. [ Assembly of Battery ]

The positive electrode, the separator made of a microporous polypropylene film having a thickness of 7 μm, and the negative electrode were laminated in this order, the laminate was wound a plurality of times in the longitudinal direction thereof, and then the end portions of the wound body were fixed by an adhesive tape to form a flat-type wound electrode body. The wound electrode body was housed in a bag-like package made of an aluminum laminated film, and 2g of an electrolytic solution was injected thereinto. Finally, the opening of the aluminum laminated film is sealed by thermal fusion in a vacuum atmosphere. Thus, a cylindrical battery of example 1-1 was manufactured.

As a result of disassembling the battery after the pre-charging, it was confirmed that a gel-like coating was formed on the surface of the negative electrode.

< examples 1 and 2>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which compound B was mixed as a heteropolyacid salt compound was used in place of compound A. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 82ppm, respectively.

< examples 1 to 3>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which compound C was mixed as a heteropolyacid salt compound was used in place of compound A. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 15ppm and 58ppm, respectively.

< examples 1 to 4>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which compound D was mixed as a heteropolyacid salt compound was used in place of compound A. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 16ppm and 63ppm, respectively.

< comparative example 1-1>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which compound E was mixed as a heteropolyacid salt compound was used in place of compound A. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 168ppm and 721ppm, respectively.

< comparative examples 1 and 2>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which compound F was mixed as a heteropolyacid salt compound was used in place of compound A. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 223ppm and 582ppm, respectively.

< comparative examples 1 to 3>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which compound G was mixed as a heteropolyacid salt compound was used in place of compound A. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 531ppm and 2,120ppm, respectively.

< comparative examples 1 to 4>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which compound H was mixed as a heteropolyacid salt compound was used in place of compound A. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 622ppm and 2,064ppm, respectively.

< comparative examples 1 to 5>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which 2.0% by weight of compound E was mixed instead of compound a was used as the heteropolyacid salt compound. In comparative examples 1 to 5, a part of the compound E became insoluble, so that the moisture content and the acid content after dissolving the whole amount of the added heteropolyacid salt compound could not be measured.

< comparative examples 1 to 6>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which 2.0% by weight of compound F was mixed instead of compound a was used as the heteropolyacid salt compound. In comparative examples 1 to 6, a part of the compound F became insoluble, so that the moisture content and the acid content after dissolving the whole amount of the added heteropolyacid salt compound could not be measured. Further, a part of the heteropoly acid structure of the added compound F is broken (collapse).

< comparative examples 1 to 7>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which 2.0% by weight of compound G was mixed instead of compound a was used as the heteropolyacid salt compound. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 2,156ppm and 3,590ppm, respectively. Further, a part of the heteropoly acid structure of the added compound G is broken.

< comparative examples 1 to 8>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which 2.0% by weight of compound H was mixed instead of compound a was used as the heteropolyacid salt compound. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 2,261ppm and 3,356ppm, respectively.

< comparative examples 1 to 9>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution to which no heteropoly acid was added was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 56ppm, respectively. As a result of disassembling the battery after the pre-charging, the deposit on the surface of the negative electrode could not be confirmed.

The following initial capacity and cycle tests and high-speed discharge tests were performed on the batteries of examples 1-1 to 1-4 and comparative examples 1-1 to 1-9.

[ evaluation of Battery ]

(a) Amount of expansion of battery after initial charging

After measuring the initial cell thickness of each of the cells in the above examples and comparative examples, constant current charging was performed at a constant current of 800mA in an environment of 23 ℃ until the voltage reached 4.2V, and charging was continued at a constant voltage of 4.2V until the total charging time reached 3 hours. After that, the thickness of the battery after the initial charge was measured. To indicate the amount of swelling of the battery, the rate of change in the thickness of the battery after initial charging was calculated according to the following expression.

Rate of change in battery thickness after initial charge [% ] { (battery thickness after initial charge)/(initial battery thickness) } × 100

(b) Swelling amount of battery after high-temperature storage

With respect to each of the batteries of the above-described examples and comparative examples, constant-current charging was performed at a constant current of 800mA in an environment of 23 ℃ until the voltage reached 4.2V, and charging was continued at a constant voltage of 4.2V until the total charging time reached 3 hours. After that, the thickness of the battery after the initial charge was measured.

Subsequently, the battery in a charged state was stored in a thermostat at 85 ℃ for 12 hours, and thereafter, the thickness of the battery after high-temperature storage was measured. In order to indicate the swelling amount of the battery, the rate of change in the thickness of the battery after high-temperature storage was calculated according to the following expression.

Rate of change in battery thickness after high-temperature storage [% ] { (battery thickness after high-temperature storage)/(battery thickness after initial charge) } × 100

The test results are shown in table 1 below.

TABLE 1

As can be noted from table 1, in the battery using the electrolytic solution containing each of the compounds a to D according to the embodiment of the present invention as the heteropolyacid salt compound, the swelling of the battery at the initial charging and also after the high-temperature storage can be suppressed. It is considered that the increase in the thickness of the battery is correlated with the moisture content and the acid content in the electrolyte; and moisture and protons contained in the heteropoly-acid in its structure react vigorously with the electrode upon charging to cause decomposition, so that the thickness of the battery increases, and deterioration of the battery characteristics is caused.

This is effective for improving battery characteristics to remove crystal water from the structure of heteropoly-acids. However, when crystal water is removed from the proton-containing heteropoly-acid, a part of the structure is hardly maintained, the solubility in the electrolytic solution becomes poor, and it is difficult to obtain a desired effect. In the heteropolyacid salt compound according to the embodiment of the present invention, since the cation exchanged with the proton stabilizes the structure of the heteropolyacid, the high-temperature storage characteristics can be improved without increasing each of the moisture content and the acid content.

[ example 2]

In example 2, the characteristics of the laminate film type battery were evaluated by changing the addition amount of each of the compounds a to D as the heteropolyacid salt compound.

< example 2-1>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which 0.01% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 58ppm, respectively.

< examples 2 to 2>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.05% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 58ppm, respectively.

< examples 2 to 3>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.1% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 15ppm and 65ppm, respectively.

< examples 2 to 4>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.5% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 16ppm and 73ppm, respectively.

< examples 2 to 5>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 1.0% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 80ppm, respectively.

< examples 2 to 6>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 2.0% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 21ppm and 84ppm, respectively.

< examples 2 to 7>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 3.0% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 31ppm and 91ppm, respectively.

< examples 2 to 8>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 5.0% by weight of compound a as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 43ppm and 98ppm, respectively.

< examples 2 to 9>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which 0.01% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 58ppm, respectively.

< examples 2 to 10>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.05% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 58ppm, respectively.

< examples 2 to 11>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.1% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 15ppm and 66ppm, respectively.

< examples 2 to 12>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.5% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 16ppm and 78ppm, respectively.

< examples 2 to 13>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 1.0% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 82ppm, respectively.

< examples 2 to 14>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 2.0% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 22ppm and 95ppm, respectively.

< examples 2 to 15>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 3.0% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 30ppm and 98ppm, respectively.

< examples 2 to 16>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 5.0% by weight of compound B as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 43ppm and 103ppm, respectively.

< examples 2 to 17>

A battery was produced in the same manner as in example 1-1, except that a nonaqueous electrolytic solution in which 0.01% by weight of Compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 56ppm, respectively.

< examples 2 to 18>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.05% by weight of compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 56ppm, respectively.

< examples 2 to 19>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.1% by weight of compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 56ppm, respectively.

< examples 2 to 20>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 0.5% by weight of compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 14ppm and 57ppm, respectively.

< examples 2 to 21>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 1.0% by weight of compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 15ppm and 58ppm, respectively.

< examples 2 to 22>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 2.0% by weight of compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 16ppm and 61ppm, respectively.

< examples 2 to 23>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 3.0% by weight of compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 20ppm and 61ppm, respectively.

< examples 2 to 24>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution in which 5.0% by weight of compound C as a heteropolyacid salt compound was mixed was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 22ppm and 62ppm, respectively.

< examples 2 to 25>

A battery was produced in the same manner as in example 2-1, except that a nonaqueous electrolytic solution was used which was prepared by mixing 1.0% by weight of fluoroethylene carbonate (FEC), 0.8mol/kg of lithium hexafluorophosphate (LiPF) as an electrolyte salt₆) And 1.0% by weight of compound a as a heteropolyacid salt compound was dissolved in a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 5/5. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 82ppm, respectively.

< examples 2 to 26>

Batteries were produced in the same manner as in examples 2 to 25, except that a nonaqueous electrolytic solution in which compound B was mixed as a heteropolyacid salt compound was used in place of compound a. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 83ppm, respectively.

< examples 2 to 27>

Batteries were produced in the same manner as in examples 2 to 25, except that a nonaqueous electrolytic solution in which compound C was mixed as a heteropolyacid salt compound was used in place of compound a. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 16ppm and 59ppm, respectively.

< examples 2 to 28>

Batteries were produced in the same manner as in examples 2 to 25, except that a nonaqueous electrolytic solution in which compound D was mixed as a heteropolyacid salt compound was used in place of compound a. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 71ppm, respectively.

< examples 2 to 29>

Batteries were fabricated in the same manner as in examples 2 to 25, except that Vinylene Carbonate (VC) was added instead of fluoroethylene carbonate (FEC). The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 81ppm, respectively.

< examples 2 to 30>

Batteries were produced in the same manner as in examples 2 to 29, except that compound B was mixed as a heteropolyacid salt compound in place of compound a. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 82ppm, respectively.

< examples 2 to 31>

Batteries were produced in the same manner as in examples 2 to 29, except that compound C was mixed as a heteropolyacid salt compound in place of compound a. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 18ppm and 58ppm, respectively.

< examples 2 to 32>

Batteries were produced in the same manner as in examples 2 to 29, except that compound D was mixed as a heteropolyacid salt compound in place of compound a. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 17ppm and 66ppm, respectively.

[ evaluation of Battery ]

(a) Amount of expansion of battery after initial charging

(b) Swelling amount of battery after high-temperature storage

The rate of change in the thickness of the battery after each operation in the initial charge and high-temperature preservation was calculated in the same manner as in example 1.

The test results are shown in tables 2 and 3 below.

TABLE 2

TABLE 3

As can be noted from table 2, by using the heteropolyacid salt compound according to the embodiment of the present invention, the deterioration of the electrolytic solution can be suppressed in a wide addition amount range, thereby suppressing the swelling of the battery after the initial charge to the high-temperature storage. In particular, the addition amount of the heteropolyacid salt compound is preferably 0.01% by weight or more and not more than 3.0% by weight from the viewpoint of battery swelling after initial charging. Also, the addition amount of the heteropolyacid salt compound is preferably 1.0% by weight or more and not more than 3.0% by weight in the viewpoint including swelling of the battery after high-temperature storage.

Lithium salts of heteropolyacids are preferred as the heteropolyacid salt compound. In the ammonium salt, although the stability of the ammonium cation to charge/discharge is slightly inferior to that of the lithium ion, the effect for suppressing increase in each of the moisture content and the acid content is high even at a high addition amount. As for the anion portion of the heteropoly-acid, silicotungstic acid is preferable from the viewpoint of characteristics at the time of high-temperature storage. This is believed to be due to the fact that the coating produced from the silicon-containing heteropolyacid salt compound is electrochemically stable.

Also, it can be noted from table 3 that when fluoroethylene carbonate and vinylene carbonate, both of which are reactive cyclic carbonates, are used in combination, the swelling of the battery at the time of initial charge can be more effectively suppressed.

Example 3: confirmation of Effect of heteropolyacids having each of Keggin Structure and Preyssler Structure ]

The heteropoly acid or heteropoly acid compound used in the following examples is as follows.

A compound I: lithium phosphotungstate with Preyssler structure

Compound J: potassium phosphotungstate with Preyssler structure

Compound K: tetratetradecyl phosphotungstic acid hydrate with Preyssler structure

A compound L: triacontastic acid phosphotungstic acid hydrate with Keggin structure

In the following description, the mass of the heteropoly-acid is defined as a value obtained by subtracting the mass of bound water that the heteropoly-acid has; and the mass of the heteropolyacid salt compound is defined as a value obtained by subtracting the mass of the bound water which the heteropolyacid salt compound has.

< example 3-1>

[ production of Positive electrode ]

94 parts by mass of lithium cobaltate (LiCoO) as a positive electrode active material was added₂) 3 parts by mass of graphite as a conductive agent and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed, and then N-methylpyrrolidone was added thereto to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was uniformly coated on both surfaces of a 10 μm-thick aluminum (Al) foil serving as a positive electrode current collector, and after drying, the resultant was press-molded by a roll press machine to form a positive electrode sheet in which a positive electrode active material layer having a bulk density of 3.40g/cc was formed. Finally, the positive electrode sheet was cut into a shape of 50mm wide and 300mm long, and a positive electrode lead made of aluminum (Al) was attached to the end of the positive electrode current collector by welding, thereby manufacturing a positive electrode.

[ production of negative electrode ]

97 parts by mass of mesocarbon microbeads (MCMB) as a negative electrode active material and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed, and then N-methylpyrrolidone was added thereto to obtain a negative electrode mixture slurry. Subsequently, the anode mixture slurry was uniformly coated on both surfaces of a 10 μm-thick copper foil serving as an anode current collector, and after drying, the resultant was press-molded by a roll press to form an anode sheet in which an anode active material layer having a bulk density of 1.80g/cc was formed. Finally, the negative electrode sheet was cut into a shape of 50mm wide and 300mm long, and a negative electrode lead made of nickel (Ni) was mounted on the end of a negative electrode current collector by welding, thereby manufacturing a negative electrode.

[ preparation of nonaqueous electrolyte solution ]

0.8mol/kg of lithium hexafluorophosphate (LiPF) as an electrolyte salt was added₆) And 1.0% by weight of compound I as a heteropolyacid salt compound was dissolved in a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 5/5.

[ Assembly of Battery ]

A separator prepared by coating polyvinylidene fluoride having a thickness of 2 μm on each surface of a microporous polypropylene film having a thickness of 7 μm was used. The positive electrode and the negative electrode are laminated via the separator, the laminate is wound a plurality of times in the longitudinal direction thereof, and thereafter, the end portion of the wound body is fixed by an adhesive tape to form a flat-type wound electrode body. Subsequently, the wound electrode body was housed in a bag-like package made of an aluminum laminated film, and 2g of an electrolytic solution was injected thereinto. Subsequently, the opening of the aluminum laminated film was sealed by thermal fusion in a vacuum atmosphere. After that, the resultant was heated while applying pressure from the outside, thereby manufacturing a test secondary battery of a laminate film type in which a gel electrolyte layer was formed.

As a result of disassembling the battery after the pre-charging, it was confirmed that a gel-like coating was formed on the surface of the negative electrode. And the moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 15ppm and 65ppm, respectively.

< examples 3 and 2>

A battery was produced in the same manner as in example 3-1, except that a nonaqueous electrolytic solution in which a compound J was mixed instead of the compound I as a heteropoly-acid compound was used. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 15ppm and 62ppm, respectively.

< examples 3-3 to 3-4>

A test secondary battery was produced in the same manner as in examples 3-1 to 3-2 except that the addition amount of the heteropoly-acid compound relative to the nonaqueous electrolytic solution was adjusted to 2.0% by weight. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 20ppm and 74ppm, respectively, in example 3-3, and 18ppm and 70ppm, respectively, in example 3-4.

< comparative examples 3-1 to 3-2>

A test secondary battery was fabricated in the same manner as in examples 3-1 to 3-2, except that compounds K and L as heteropoly-acid compounds were used instead of compounds I and J as heteropoly-acid compounds, respectively. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 483ppm and 1,955ppm, respectively, in comparative example 3-1, and 531ppm and 2,120ppm, respectively, in comparative example 3-2.

< comparative examples 3-3 to 3-4>

Test secondary batteries were produced in the same manner as in examples 3-1 to 3-2 except that compounds K and L as heteropoly-acid compounds were used instead of compounds I and J as heteropoly-acid compounds, respectively; and the addition amount of each of the heteropoly-acid compounds was adjusted to 2.0% by weight. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 1,918ppm and 3,213ppm, respectively, in comparative example 3-3, and 2,156ppm and 3,590ppm, respectively, in comparative example 3-4.

< comparative examples 3 to 5>

A test secondary battery was produced in the same manner as in example 3-1, except that no heteropoly acid compound or heteropoly acid was added to the nonaqueous electrolytic solution. The moisture content and the acid content in the nonaqueous electrolytic solution as measured in the same manner as in example 1-1 were 12ppm and 56ppm, respectively.

[ evaluation of Battery ]

(a) Amount of expansion of battery after initial charging

(b) Swelling amount of battery after high-temperature storage

The rate of change in the thickness of the battery after each operation in the initial charge and high-temperature preservation was calculated in the same manner as in example 1.

The test results are shown in table 4 below.

TABLE 4

As is clear from table 4, in examples 3-1 to 3-4 using compound I or compound J as the heteropoly acid compound having a Preyssler structure, the swelling of the battery after each of the initial charge and the high-temperature storage can be suppressed, compared to comparative example 3-5 in which the heteropoly acid or the heteropoly acid compound is not added.

On the other hand, in comparative examples 3-1 to 3-4 using compound K or compound L, which are salt-free heteropolyacids having a Preyssler structure or a Keggin structure, the battery swelling at the time of high-temperature storage was suppressed, but the battery swelling at the time of initial charging was increased.

It can be considered from table 4 that the increase in the thickness of the battery is correlated with each of the moisture content and the acid content in the electrolyte; and moisture and protons contained in the heteropoly-acid in its structure react vigorously with the electrode upon charging to cause decomposition, so that the thickness of the battery increases, and deterioration of the battery characteristics is caused. This is effective for improving battery characteristics to remove crystal water from the structure of heteropoly-acids. However, when crystal water is removed from the proton-containing heteropoly-acid, a part of the structure is hardly maintained, the solubility in the electrolytic solution becomes poor, and it is difficult to obtain a desired effect.

The heteropoly acid compound can suppress battery swelling from the time of initial charge to the time of high-temperature storage. In particular, since the heteropoly-acid compound having a Preyssler structure has an anion in which an anion of a Keggin structure is further condensed and is stable against pH change during cation exchange, it is possible to improve high-temperature storage characteristics without increasing each of moisture content and acid content.

Further, by adjusting the addition amount of the heteropoly acid or heteropoly acid compound to 2.0% by weight, a higher expansion suppressing effect can be obtained.

Example 4: confirmation of Effect of heteropolyacids having each of Keggin Structure and Preyssler Structure ]

The heteropoly acid or heteropoly acid compound used in the following examples is the same as that in example 3.

< examples 4-1 to 4-8>

A test secondary battery was produced in the same manner as in example 3-1, except that the addition amount of compound I as a heteropoly-acid was changed as shown in table 5.

< examples 4-9 to 4-16>

A test secondary battery was produced in the same manner as in example 3-1, except that compound J was used as the heteropoly acid; and the amount of compound J added was changed as shown in table 5.

< examples 4-17 to 4-18>

A test secondary battery was fabricated in the same manner as in examples 3-1 to 3-2, except that 1% by weight of fluoroethylene carbonate (FEC) was added to the nonaqueous electrolytic solution. < examples 4-19 to 4-20>

A test secondary battery was fabricated in the same manner as in examples 3-1 to 3-2, except that 1% by weight of Vinylene Carbonate (VC) was added to the nonaqueous electrolytic solution.

< comparative examples 4-1 to 4-2>

A test secondary battery was fabricated in the same manner as in comparative examples 3-1 to 3-2, except that 1% by weight of fluoroethylene carbonate (FEC) was added to the nonaqueous electrolytic solution.

< comparative examples 4-3 to 4-4>

A test secondary battery was fabricated in the same manner as in comparative examples 3-1 to 3-2, except that 1% by weight of Vinylene Carbonate (VC) was added to the nonaqueous electrolytic solution.

[ evaluation of Battery ]

(a) Amount of expansion of battery after initial charging

(b) Swelling amount of battery after high-temperature storage

The rate of change in the thickness of the battery after each operation in the initial charge and high-temperature preservation was calculated in the same manner as in example 1.

The test results are shown in table 5 below.

TABLE 5

As is clear from table 5, in the heteropoly-acid compounds according to compound I and compound J, the battery swelling suppression effect can be obtained in a wide addition amount range. And, potassium salt of heteropoly-acid is preferable as the heteropoly-acid compound. In the potassium salt, since the content of the polyanion is relatively reduced, it is slightly inferior to the lithium salt in terms of the battery swelling suppression effect; however, it has a high effect for suppressing an increase in each of the moisture content and the acid content.

Further, in the case of using a heteropoly acid compound based on compound I and compound J, the battery swelling suppression effect at the initial charge can be greatly improved by using a reactive cyclic carbonate in combination with the nonaqueous electrolytic solution.

On the other hand, in each of the comparative examples using the heteropoly acid, the battery swelling suppressing effect was not sufficiently obtained even by using the reactive cyclic carbonate in combination.

7. Other embodiments

It should not be construed that the present invention is limited to the above-described embodiments according to the present invention, and various modifications and applications may be made therein without departing from the gist of the present invention.

For example, in the above-described embodiment and working examples, the battery having the laminate film type or cylindrical battery structure and the battery having the rectangular battery structure have been described, but it should not be construed that the present invention is limited thereto. For example, the present invention can be applied to a battery having other battery structures such as a coin type and a button type and a battery already having a laminate structure in which electrodes are laminated, and the same effect can be obtained. Also, as for the structure of the electrode body, not only a winding type but also various configurations such as a laminate type and a meander type may be applied.

This application contains subject matter relating to what is disclosed in japanese priority patent applications JP 2010-044810 and JP 2010-138776, filed to the office at 3/2010 and 2/2010 and 17/2010, respectively, the entire contents of which are incorporated herein by reference.

It should be understood by those skilled in the art that various changes, combinations, sub-combinations, and alterations may be made depending on design requirements and other factors insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (7)

1. A non-aqueous electrolyte comprising:

a solvent;

an electrolyte salt; and

a heteropolyacid salt compound which is lithium phosphotungstate having a Keggin structure, lithium silicotungstate having a Keggin structure, tetrabutylammonium silicotungstate having a Keggin structure, tetrabutylphosphonium silicotungstate having a Keggin structure, lithium phosphotungstate having a Preyssler structure or potassium phosphotungstate having a Preyssler structure,

wherein the amount of water in the nonaqueous electrolytic solution is not more than 50ppm,

the nonaqueous electrolyte contains a cyclic carbonate represented by the following formula (III),

wherein the content of the first and second substances,

each of R1 to R4 represents a hydrogen group, a halogen group, an alkyl group or a haloalkyl group, with the proviso that at least one of R1 to R4 represents a halogen group or a haloalkyl group.

2. The nonaqueous electrolyte according to claim 1, comprising 0.01% by weight or more and not more than 3% by weight of the heteropolyacid salt compound.

3. The non-aqueous electrolyte according to claim 1,

the electrolyte salt containsSelected from the group consisting of lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate (LiBF)₄) Lithium perchlorate (LiClO)₄) And lithium hexafluoroarsenate (LiAsF)₆) At least one member of the group.

4. A nonaqueous electrolyte battery comprising:

a positive electrode;

a negative electrode; and

a non-aqueous electrolyte, wherein,

a gel-like coating comprising an amorphous polyacid containing one or more multi-elements and/or a polyacid compound is disposed on a surface of at least a portion of the anode, the coating being derived from a heteropolyacid salt compound that is lithium phosphotungstate having a Keggin structure, lithium silicotungstate having a Keggin structure, tetrabutylammonium silicotungstate having a Keggin structure, tetrabutylphosphonium silicotungstate having a Keggin structure, lithium phosphotungstate having a Preyssler structure, or potassium phosphotungstate having a Preyssler structure,

wherein the amount of water in the nonaqueous electrolytic solution is not more than 50ppm,

the nonaqueous electrolyte contains a cyclic carbonate represented by the following formula (III),

wherein the content of the first and second substances,

each of R1 to R4 represents a hydrogen group, a halogen group, an alkyl group or a haloalkyl group, with the proviso that at least one of R1 to R4 represents a halogen group or a haloalkyl group.

5. The nonaqueous electrolyte battery according to claim 4, packaged by a package member composed of a laminate film.

6. The nonaqueous electrolyte battery according to claim 5,

the rate of change in the thickness of the battery after initial charging is not more than 15% in the case of initial charging at a full charge voltage of 4.2V.

7. The nonaqueous electrolyte battery according to claim 5,

the rate of change in the thickness of the battery after being stored in a fully charged state in an environment at 85 ℃ for 12 hours is not more than 15%.

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