JP2001006667A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

(57) [Problem] To provide a non-aqueous electrolyte secondary battery having higher capacity and superior cycle characteristics than a battery using a conventional carbon material as a negative electrode material. SOLUTION: The negative electrode material is a composite particle in which the whole or a part of the periphery of a core particle composed of a solid phase A is coated with a solid phase B, wherein the solid phase A contains tin as a constituent element, Is selected from the group consisting of tin, which is a constituent element of the solid phase A, and a group 2 element, a transition element, a group 12, a group 13 element, and a group 14 element excluding carbon except for the above-mentioned constituent elements. Using a material that is a solid solution with at least one element or an intermetallic compound, having a nuclear magnetic resonance signal of lithium occluded in the negative electrode material in the range of −10 to 40 ppm with respect to lithium chloride, and − 10-4p
A non-aqueous electrolyte secondary battery is characterized by having at least one signal in the pm range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable information terminal, a portable electronic device, a home, and the like, which have improved electrochemical characteristics such as charge / discharge capacity and charge / discharge cycle life by improving a negative electrode material of a nonaqueous electrolyte secondary battery. The present invention relates to a non-aqueous electrolyte secondary battery used for a small power storage device for use, a motorcycle powered by a motor as a power source, an electric vehicle, a hybrid electric vehicle, and the like.

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries used as main power sources for mobile communication devices and portable electronic devices have the characteristics of high electromotive force and high energy density.
A lithium secondary battery using lithium metal as the negative electrode material has a high energy density, but dendrites are deposited on the negative electrode during charging, and may repeatedly break through the separator to reach the positive electrode side by repeated charging and discharging, causing an internal short circuit. there were. Further, the precipitated dendrite has a high specific activity because of its large specific surface area, and reacts with the solvent in the electrolytic solution on its surface to form a solid electrolyte interface film lacking electron conductivity. For this reason, the internal resistance of the battery is increased, and particles isolated from the electron conduction network are present, and these are factors that lower the charge / discharge efficiency. For these reasons, lithium secondary batteries using lithium metal as the negative electrode material have problems with low reliability and short cycle life.

At present, a carbon material capable of occluding and releasing lithium ions is used as a negative electrode material instead of lithium metal, and has been put to practical use. Normally, metallic lithium does not precipitate on the carbon material negative electrode, so there is no problem of internal short circuit due to dendrite. However, the theoretical capacity of graphite, which is one of the carbon materials, is 372 mAh / g, which is as small as about 1/10 of the theoretical capacity of Li metal alone.

As other negative electrode materials, a simple metal material and a simple nonmetal material which form a compound with lithium are known. For example, the compound formula of tin (Sn) containing the most lithium is Li ₂₂ Sn ₅ , and metallic lithium does not usually precipitate in this range, so there is no problem of internal short circuit due to dendrite. The electrochemical capacity between these compounds and each single material is 993 m
Ah, both of which are larger than the theoretical capacity of graphite.

In addition to a simple metal material and a simple non-metal material which form a compound with lithium, as a compound negative electrode material, a non-ferrous metal silicide comprising a transition element is disclosed in JP-A-7-240201. No. 63651 discloses an intermetallic compound containing a Group 4B element and at least one of P and Sb, and has a crystal structure of CaF ₂ type, ZnS
A negative electrode material or the like made of any one of a metal mold and an AlLiSi mold has been proposed. Japanese Patent Application Laid-Open No. 10-208741 proposes a range of nuclear magnetic resonance signals of lithium occluded in a negative electrode material.

[0006]

However, the negative electrode materials having higher capacities than the above-mentioned carbon materials have the following problems, respectively.

[0007] A single metal material and a single nonmetallic negative electrode material which form a compound with lithium commonly have poor charge / discharge cycle characteristics as compared with a carbon negative electrode material. The reason is not clear, but I think as follows.

For example, tin is a crystallographic unit cell (square
Crystal, space group I4₁/ Amd) contains 4 tin atoms
I have. Lattice constant a = 0.5820 nm, c = 0.317
Converted from 5 nm, the unit cell volume is 0.1075 nm
^ThreeAnd the volume occupied by one tin atom is 26.9 × 10
^-3nm^ThreeIt is. Determined from tin-lithium binary phase diagram
To form an electrochemical compound with lithium at room temperature
In the synthesis, tin and the compound Li_TwoSn_FiveWith
It is considered that the two phases coexist. Li_TwoSn_FiveResult
The crystallographic unit cell (tetragonal, space group P4 / mbm)
Contains 10 tin atoms. The lattice constant a =
1.0274nm, c = 0.3125nm
And the unit cell volume is 0.32986 nm^ThreeAnd tin
Volume per atom (unit cell volume is defined as
Is 33.0 × 10^-3nm^ThreeIn
You. Based on this value, the compound Li can be converted from tin to Li_TwoSn_FiveNana
The volume of the material expands 1.23 times
become. Further electrochemical compound formation reaction with lithium
Progresses, eventually the compound containing the most lithium
Li_{twenty two}Sn_FiveIs generated. Li_{twenty two}Sn_FiveCrystallographic unit case of
Child (cubic, space group F23) contains 80 tin atoms
It is rare. Converted from its lattice constant a = 1.978 nm
The unit cell volume is 7.739 nm^ThreeAnd Suzuhara
Volume per child (unit cell volume is tin in unit cell
(Excluding the number of atoms) is 96.7 × 10^-3nm ^ThreeIt is.
This value is 3.59 times that of tin alone, and the material expands significantly.
Stretch.

As described above, tin undergoes a large change in the volume of the negative electrode material due to the charge / discharge reaction, and repetition of a change in a state in which two phases having a large volume difference coexist causes cracks in the material and fine particles. It is considered something. It is considered that in the miniaturized material, a space is generated between particles, the electron conduction network is divided, a portion that cannot participate in an electrochemical reaction increases, and the charge / discharge capacity decreases.

That is, the large volume change common to the negative electrode materials of a simple metal material and a simple non-metal material forming a compound with lithium and the structural change due to this are the reasons why the charge / discharge cycle characteristics are poor as compared with the carbon negative electrode material. I guess.

On the other hand, unlike the above-mentioned simple material, it is made of a non-ferrous metal silicide composed of a transition element or an intermetallic compound containing at least one of Group 4B elements and P and Sb, and its crystal structure is CaF ₂ type, ZnS A negative electrode material of any one of the negative electrode type and the AlLiSi type has been proposed as a negative electrode material having improved cycle life characteristics in JP-A-7-240201 and JP-A-9-63651, respectively.

Batteries using a non-ferrous metal silicide negative electrode material comprising a transition element disclosed in Japanese Patent Application Laid-Open No. 7-240201 are described in Examples and Comparative Examples at the first cycle, the 50th cycle, and the 100th cycle. Although the charge / discharge cycle characteristics are improved as compared with the lithium metal negative electrode material, the battery capacity is increased by only about 12% at the maximum as compared with the natural graphite negative electrode material. Therefore, although not explicitly stated in the specification, it is considered that the non-ferrous metal silicide negative electrode material composed of a transition element has not been significantly increased in capacity as compared with the graphite negative electrode material.

Further, the materials disclosed in Japanese Patent Application Laid-Open No. 9-63651 have improved charge-discharge cycle characteristics as compared with the Li-Pb alloy negative electrode material in Examples and Comparative Examples, and have a higher performance than the graphite negative electrode material. It has been shown to be of high capacity.
However, the discharge capacity was remarkably reduced in the charge / discharge cycles of 10 to 20 cycles, and Mg ₂ Sn, which is considered to be the best, was considered.
Also, after about 20 cycles, the capacity is reduced to about 70% of the initial capacity.

The materials disclosed in Japanese Patent Application Laid-Open No. 10-208741 have a nuclear magnetic resonance signal of lithium absorbed in various alloy materials in the range of 5 to 40 ppm, have a high energy density and an excellent cycle life. Suggesting material. However, in the cycle life, LiCo
Even if O ₂ is used, the capacity is reduced to 70% of the maximum capacity in 372 cycles.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a composite particle in which the entire surface or a part of a core particle composed of a solid phase A is coated with a solid phase B, wherein the solid phase A contains tin as a constituent element. The solid phase B is a group consisting of tin, which is a constituent element of the solid phase A, and a group 2 element, a transition element, a group 12 element, a group 13 element, and a group 14 element excluding carbon except for the above-mentioned constituent elements. By using a material which is a solid solution or an intermetallic compound with at least one element selected from the group consisting of: a solid phase A having a higher capacity, and a solid phase B having a role of suppressing expansion and contraction caused by charging and discharging of the solid phase A. This provides a negative electrode material having excellent charge / discharge cycle characteristics, furthermore, a nuclear magnetic resonance signal of lithium occluded in the negative electrode material is generated in a range of -10 to 40 ppm with respect to lithium chloride, and -10 to 4 pp
m has a main signal, or -10 to 0 pp
It is an object of the present invention to solve the conventional problem by being characterized in that the main signal of m is 1 to 10 times the intensity of the signal appearing at 10 to 20 ppm.

Since the solid phase A of the negative electrode material of the present invention contains high-capacity tin as a constituent element, it is considered that the solid-phase A mainly contributes to an increase in the charge / discharge capacity. Further, the solid phase B covering the whole or a part of the periphery of the core particle composed of the solid phase A contributes to the improvement of the charge / discharge cycle characteristics, and the amount of lithium contained in the solid phase B is usually , Solid solution, and intermetallic compound, respectively, are less than in the case of single use.

When lithium reacts with this material, lithium exists covalently or ionically.
Lithium covalently present appears in the range of 10 to 20 ppm in the ⁷ Li nuclear magnetic resonance signal, and its existing site is designated as “X site”. Further, lithium ionically present appears in the range of -10 to 40 ppm in a ⁷ Li nuclear magnetic resonance signal, and its existing site is defined as a “Y site”.

[0018] The Y site contains a signal related in part to the irreversible factor. This is generally found in carbon systems but is slight.

If the reversible lithium sites X and Y are present in a large amount, high capacity and excellent cycle characteristics can be obtained. That is, in the charged state, the ⁷ Li nuclear magnetic resonance signal appears in the range of -10 to 40 ppm, and also appears in the range of -10 to 4 ppm, so that both the X site and the Y site are present, so that high capacity and excellent cycle characteristics are obtained. Can be realized.

Further, -10 to 4 indicating the presence of the Y site
The signal appearing in ppm indicates the presence of the X site 10
If the intensity is 1 to 10 times that of the signal appearing at 20 ppm, the capacity is further increased.

[0021] The present patent the presence state of lithium occluded in Honmakekyoku material, the existence ratio of covalent if the case ionically, by limiting in ⁷ Li nuclear magnetic resonance signals, a high capacity Further, the present invention provides a material having excellent cycle characteristics.

Thus, in order to exhibit high capacity and excellent cycle characteristics, the ⁷ Li nuclear magnetic resonance signal in the charged state appears in the range of -10 to 40 ppm indicating that the ionic state and the covalent bond state are mixed. And the presence of lithium in an ionic state leading to high capacity-
It is preferable that a signal appears at 10 to 4 ppm. Further, a signal occurring at -10 to 4 ppm indicating an ionic lithium state is 10 to 10 indicating a covalent lithium state.
If the intensity is 1 to 10 times that of the signal appearing at 20 ppm, the capacity will be higher.

The positive electrode and the negative electrode used in the present invention are composed of a positive electrode active material capable of electrochemically and reversibly inserting and releasing lithium ions and a mixture layer containing a conductive agent, a binder and the like in a negative electrode material. It was prepared by coating on the surface of a.

The negative electrode material used in the present invention is a composite particle in which the whole or a part of the periphery of the core particle composed of the solid phase A is coated with the solid phase B, and the solid phase A contains tin as a constituent element. The solid phase B is a group consisting of tin, which is a constituent element of the solid phase A, and a group 2 element, a transition element, a group 12, a group 13 element, and a group 14 element excluding carbon, other than the above constituent elements. And a material that is a solid solution with at least one element selected from the group consisting of: or an intermetallic compound (hereinafter, referred to as “composite particles”).

As one of the methods for producing the composite particles used in the present invention, a melt of the charged composition of each element constituting the composite particles is prepared by a dry spray method, a wet spray method, a roll quenching method and a rotating electrode method. Rapid cooling and solidification by such as
There is a method of performing heat treatment at a temperature lower than the solidus temperature of the solid solution or the intermetallic compound determined by the charged composition. By rapid solidification of the melt, solid phase A particles as core particles and solid phase B covering the entire surface or a part of the periphery of the solid phase A particles are precipitated.
The purpose of the present invention is to increase the uniformity of the composite particles, but the composite particles according to claim 1 can be obtained even without heat treatment. In addition, any method other than the above-mentioned cooling method can be used as long as it can sufficiently cool.

As another manufacturing method, an adhesion layer made of an element other than the elements contained in the solid phase A necessary for forming the solid phase B is formed on the surface of the powder of the solid phase A,
There is a method of performing heat treatment at a temperature lower than the solidus temperature of the solid solution or the intermetallic compound determined by the charged composition. By this heat treatment, the component elements in the solid phase A diffuse into the adhesion layer, and the solid phase B is formed as a coating layer. The adhesion layer can be formed by a plating method or a mechanical alloying method. In the mechanical alloying method, heat treatment may not be required. In addition, any method capable of forming an adhesion layer can be used.

The negative electrode conductive agent used in the present invention may be any material as long as it is an electron conductive material. For example, graphites such as natural graphite (flaky graphite etc.), artificial graphite, expanded graphite, carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fibers, Conductive fibers such as metal fibers, metal powders such as copper and nickel, and organic conductive materials such as polyphenylene derivatives can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite, acetylene black and carbon fiber are particularly preferred. The addition amount of the conductive agent is not particularly limited, but may be 1 to 50 with respect to the negative electrode material.
% By weight, and particularly preferably 1 to 30% by weight. Further, since the negative electrode material of the present invention has electronic conductivity itself, it can function as a battery without adding a conductive material.

The binder for the negative electrode used in the present invention may be either a thermoplastic resin or a thermosetting resin. Preferred binders in the present invention include, for example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexa Fluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetra Fluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene Polymer, ethylene - chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene copolymer, vinylidene fluoride - perfluoromethyl vinyl ether - tetrafluoroethylene copolymer,
Ethylene-acrylic acid copolymer or (Na
⁺ ) Ion crosslinked product, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl methacrylate Copolymers or (Na ⁺ ) ion crosslinked products of the above materials can be mentioned, and these materials can be used alone or as a mixture. Further, a more preferable material among these materials is
Styrene butadiene rubber, polyvinylidene fluoride, ethylene-acrylic acid copolymer or (Na ⁺ )
Ion crosslinked product, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl methacrylate copolymer It is a combined or (Na ⁺ ) ion crosslinked product of the above materials.

As the current collector for the negative electrode used in the present invention, any collector may be used as long as it does not cause a chemical change in the constructed battery. For example, in addition to stainless steel, nickel, copper, titanium, carbon, conductive resin, and the like, a material obtained by treating the surface of copper or stainless steel with carbon, nickel, or titanium is used. Particularly, copper or a copper alloy is preferable. The surface of these materials can be oxidized and used. In addition, it is desirable to make the current collector surface uneven by surface treatment. As the shape, in addition to a foil, a film, a sheet, a net, a punched material, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like are used. The thickness is not particularly limited, but 1 to
Those having a size of 500 μm are used.

As the positive electrode material used in the present invention, a compound containing or not containing lithium can be used. For example, Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , L
_{i x Co y Ni 1-y} O 2, Li x Co y M 1-y O z, Li x Ni
_{1-y M y O z,} Li x Mn 2 O 4, Li x Mn 2-y M y O 4 (M =
Na, Mg, Sc, Y, Mn, Fe, Co, Ni, C
u, Zn, Al, Cr, Pb, Sb, and B) (where x = 0 to 1.2, y = 0 to 0.9,
z = 2.0 to 2.3). Where x
The value is a value before the start of charge / discharge, and increases / decreases due to charge / discharge. However, it is also possible to use other positive electrode materials such as transition metal chalcogenides, vanadium oxides and lithium compounds thereof, niobium oxides and lithium compounds thereof, conjugated polymers using organic conductive substances, and Chevrel phase compounds. . It is also possible to use a mixture of a plurality of different positive electrode materials. The average particle size of the positive electrode active material particles is not particularly limited, but is preferably 1 to 30 μm.

The positive electrode conductive agent used in the present invention may be any electronic conductive material which does not cause a chemical change at the charge and discharge potential of the positive electrode material used. For example, graphites such as natural graphite (flaky graphite, etc.), artificial graphite, acetylene black, Ketjen black, channel black, furnace black, lamp black,
Carbon blacks such as thermal black, carbon fiber,
Conductive fibers such as metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide and organic conductive materials such as polyphenylene derivatives Materials and the like can be included alone or as a mixture thereof. Among these conductive agents, artificial graphite and acetylene black are particularly preferred. The addition amount of the conductive agent is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 1 to 30% by weight based on the positive electrode material. For carbon and graphite, 2 to 15% by weight is particularly preferred.

The binder for the positive electrode used in the present invention may be either a thermoplastic resin or a thermosetting resin. Preferred binders in the present invention include, for example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene -Hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene -Tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene Polymer, ethylene - chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene copolymer, vinylidene fluoride - perfluoromethyl vinyl ether - tetrafluoroethylene copolymer,
Ethylene-acrylic acid copolymer or (Na
⁺ ) Ion crosslinked product, ethylene-methacrylic acid copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl acrylate copolymer or (Na ⁺ ) ion crosslinked product of the above material, ethylene-methyl methacrylate Copolymers or (Na ⁺ ) ion crosslinked products of the above materials can be mentioned, and these materials can be used alone or as a mixture. Among these materials, more preferred materials are polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

The current collector for the positive electrode used in the present invention may be any electronic conductor that does not cause a chemical change in the charge / discharge potential of the positive electrode material used. For example, in addition to stainless steel, aluminum, titanium, carbon, conductive resin, and the like, a material obtained by treating the surface of aluminum or stainless steel with carbon or titanium is used. Particularly, aluminum or an aluminum alloy is preferable. The surface of these materials can be oxidized and used. In addition, it is desirable to make the current collector surface uneven by surface treatment. The shape is a foil, a film,
A sheet, a net, a punched material, a lath body, a porous body, a foamed body, a fiber group, a molded body of a nonwoven fabric, and the like are used. The thickness is not particularly limited, but a thickness of 1 to 500 μm is used.

In the electrode mixture, a filler, a dispersant, an ionic conductor, a pressure enhancer and other various additives can be used in addition to a conductive agent and a binder. As the filler, any fibrous material that does not cause a chemical change in the configured battery can be used. Usually, fibers such as olefin-based polymers such as polypropylene and polyethylene, glass, and carbon are used. The addition amount of the filler is not particularly limited, but is 0 to 30% by weight based on the electrode mixture.
Is preferred.

The structure of the negative electrode plate and the positive electrode plate in the present invention is as follows.
It is preferable that the negative electrode mixture surface exists at least on the surface opposite to the positive electrode mixture surface.

The non-aqueous electrolyte used in the present invention comprises a solvent and a lithium salt dissolved in the solvent. Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC).
Cyclic carbonates such as dimethyl carbonate (D
MC), linear carbonates such as diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC), and aliphatic carboxylic esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate. , Γ-lactones such as γ-butyrolactone, 1,2-dimethoxyethane (DM
E), chain ethers such as 1,2-diethoxyethane (DEE) and ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolan, formamide, Acetamide, dimethylformamide, dioxolan, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3-dimethyl-2-
Aprotic organic solvents such as imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propanesultone, anisole, dimethylsulfoxide, N-methylpyrrolidone; Can be used alone or in combination of two or more. Among them, a mixed system of a cyclic carbonate and a chain carbonate or a mixed system of a cyclic carbonate, a chain carbonate and an aliphatic carboxylic acid ester is preferable.

Examples of lithium salts dissolved in these solvents include LiClO ₄ , LiBF ₄ , LiPF ₆ and Li
AlCl ₄ , LiSbF ₆ , LiSCN, LiCl, Li
CF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ ,
LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiB ₁₀ C
l ₁₀ , lithium lower aliphatic carboxylate, LiCl, Li
Br, LiI, chloroborane lithium, there may be mentioned lithium tetraphenylborate, and imides like, can be used alone or in combination of two or more in the electrolyte solution or the like to use them, in particular free of LiPF ₆ More preferably.

A particularly preferred non-aqueous electrolyte in the present invention is an electrolyte containing at least ethylene carbonate and ethyl methyl carbonate and LiPF ₆ as a supporting salt. The amount of these electrolytes to be added to the battery is not particularly limited, but a required amount can be used depending on the amounts of the positive electrode material and the negative electrode material and the size of the battery. The amount of the supporting electrolyte dissolved in the nonaqueous solvent is not particularly limited.
2-2 mol / l is preferred. In particular, 0.5-1.5m
ol / l is more preferable.

In addition to the electrolytic solution, the following solid electrolyte can be used. Solid electrolytes are classified into inorganic solid electrolytes and organic solid electrolytes. Well-known inorganic solid electrolytes include nitrides, halides, and oxyacid salts of Li. Among them, Li ₄ SiO ₄ , Li ₄ SiO _{4
-LiI-LiOH, xLi 3 PO 4} - (1-x) Li 4 S
_{iO 4, Li 2 SiS 3,} Li 3 PO 4 -Li 2 S-Si
S ₂ and a phosphorus sulfide compound are effective. In the organic solid electrolyte, for example, polyethylene oxide, polypropylene oxide, polyphosphazene, polyaziridine,
Polymer materials such as polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, polyhexafluoropropylene, and derivatives, mixtures, and composites thereof are effective.

It is also effective to add another compound to the electrolyte for the purpose of improving the discharge and charge / discharge characteristics.
For example, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, pyridine, hexaphosphoric triamide, nitrobenzene derivative, crown ethers, quaternary ammonium salt, ethylene glycol dialkyl ether and the like can be mentioned.

As the separator used in the present invention,
Has a large ion permeability, has a predetermined mechanical strength,
An insulating microporous thin film is used. Further, it is preferable to have a function of closing a hole at a certain temperature or higher to increase resistance. Sheets, nonwoven fabrics or woven fabrics made from olefin polymers such as polypropylene and polyethylene alone or in combination or glass fibers are used because of their organic solvent resistance and hydrophobicity. The pore diameter of the separator is desirably in a range in which the positive and negative electrode materials detached from the electrode sheet, the binder, and the conductive agent do not pass.
A thickness of 1 μm is desirable. Generally, the thickness of the separator is 10 to 300 μm. The porosity is determined according to the electron and ion permeability, the material, and the film pressure, but is generally preferably 30 to 80%.

Further, a mixture of a polymer material and an organic electrolytic solution composed of a solvent and a lithium salt dissolved in the solvent is absorbed and held in the positive electrode mixture and the negative electrode mixture, and the organic electrolytic solution is further absorbed. It is also possible to configure a battery in which a porous separator made of a retained polymer is integrated with a positive electrode and a negative electrode. As the polymer material, any material can be used as long as it can absorb and hold an organic electrolytic solution, and a copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferable. The shape of the battery can be any of a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a square type, and a large type used for electric vehicles.

Further, the non-aqueous electrolyte secondary battery of the present invention can be used for a portable information terminal, a portable electronic device, a small household power storage device,
The present invention can be used for a motorcycle, an electric vehicle, a hybrid electric vehicle, and the like, but is not particularly limited thereto.

[0044]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

Method for manufacturing negative electrode material (Table 1) Components (solid element, intermetallic compound, solid solution) of solid phase A and solid phase B of negative electrode material (material A to material G) used in this Example Show the element ratio, melting temperature, and solidus temperature at the time. In this embodiment, a specific manufacturing method will be described below.

Powders or blocks of each element constituting the negative electrode material are charged into a melting tank at a charging ratio shown in (Table 1), melted at a melting temperature shown in (Table 1), and the melt is rapidly cooled by a roll. The mixture was quenched and solidified by a method to obtain a solidified product. continue,
The solidified product is 10 ° C. to 50 ° C. higher than the solid solution temperature of the solid solution or intermetallic compound determined by the charged composition shown in (Table 1).
The heat treatment was performed at a low temperature in an inert atmosphere for 20 hours. The heat-treated product was pulverized by a ball mill and classified by a sieve to obtain materials A to G in particles of 45 μm or less. From these electron microscopic observation results, it was confirmed that the entire surface or a part of the periphery of the solid phase A particles was covered with the solid phase B.

[0047]

[Table 1]

FIG. 1 is a longitudinal sectional view of a cylindrical battery according to the present invention. The positive electrode plate 5 and the negative electrode plate 6 are spirally wound a plurality of times via a separator 7 and housed in the battery case 1. Then, a positive electrode lead 5 a is drawn out from the positive electrode plate 5 and connected to the sealing plate 2, and a negative electrode lead 6 a is drawn out from the negative electrode plate 6 and connected to the bottom of the battery case 1. The battery case and the lead plate can be made of a metal or an alloy having an organic electrolyte resistance and electron conductivity. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum or alloys thereof are used. In particular, the battery case is preferably formed by processing a stainless steel plate or an Al-Mn alloy plate, the positive electrode lead is most preferably aluminum, and the negative electrode lead is most preferably nickel. For the battery case, various types of engineering plastics and a combination thereof with a metal can be used to reduce the weight. Reference numeral 8 denotes an insulating ring provided on the upper and lower portions of the electrode plate group 4, respectively. Then, an electrolytic solution is injected, and a battery can is formed using the sealing plate. At this time, the safety valve can be used as a sealing plate. In addition to the safety valve, various conventionally known safety elements may be provided. For example, a fuse, a bimetal, a PTC element, or the like is used as the overcurrent prevention element. In addition to the safety valve, as a countermeasure against an increase in the internal pressure of the battery case, a method of making a cut in the battery case, a gasket cracking method, a sealing plate cracking method, or a cutting method with a lead plate can be used. Also, the charger may be provided with a protection circuit incorporating measures for overcharging and overdischarging, or may be connected independently. As a measure against overcharging, a method of interrupting the current by increasing the internal pressure of the battery can be provided. At this time, a compound for increasing the internal pressure can be contained in the mixture or the electrolyte. Compounds that increase the internal pressure include Li ₂ CO ₃ and Li
HCO ₃ , Na ₂ CO ₃ , NaHCO ₃ , CaCO ₃ , Mg
Carbonates such as CO ₃ . As a method for welding the cap, the battery case, the sheet, and the lead plate, a known method (eg, DC or AC electric welding, laser welding, ultrasonic welding) can be used. A conventionally known compound or mixture such as asphalt can be used as the sealing agent for closing.

The negative electrode plate 6 was prepared by mixing 20% by weight of carbon powder as a conductive agent and 5% by weight of polyvinylidene fluoride resin as a binder with respect to 75% by weight of the obtained negative electrode material, and dehydrating the mixture. A slurry is prepared by dispersing in methylpyrrolidinone, coated on a negative electrode current collector made of copper foil, dried,
It was produced by rolling.

On the other hand, positive electrode plate 5 is prepared by mixing 10% by weight of carbon powder as a conductive agent and 5% by weight of polyvinylidene fluoride resin as a binder with respect to 85% by weight of lithium cobalt oxide powder, and dehydrated N-methyl. A slurry is prepared by dispersing in pyrrolidinone and applied on a positive electrode current collector made of aluminum foil,
After drying, it was produced by rolling.

As the organic electrolyte, a solution prepared by dissolving 1.5 mol / l of LiPF ₆ in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 1 was used.

As described above, the material A shown in (Table 2)
To G were used as negative electrodes, to produce batteries A to G. In addition, the produced cylindrical battery has a diameter of 18 mm and a height of 65 mm. These batteries were charged at a constant current of 100 mA until the voltage reached 4.2 V, and then a charge / discharge cycle in which the batteries were discharged at a constant current of 100 mA until the voltage reached 2.0 V was repeated. Charge and discharge were performed in a constant temperature bath at 20 ° C.

The charge and discharge are repeated up to 400 cycles, and the discharge capacity at the initial stage and after 400 cycles, and the ratio of the discharge capacity at the 400th cycle to the initial discharge capacity are shown in Table 2 as the capacity retention ratio. ⁷ Li-NMR measurement of the charged negative electrode material was performed, and a nuclear magnetic resonance signal of the stored lithium was measured with respect to lithium chloride. Multiple signals occurred in the range of -10 to 40 ppm. (Table 2) shows the positions of the generated signals and -10 to 4p
pm and the intensity ratio of signals appearing in the range of 10 to 20 ppm. The signal position and intensity differed in the same material due to lot variation. ⁷ Li-N
The measurement conditions of MR are as follows. Apparatus: INOVA400 manufactured by VARIAN. Temperature; room temperature. Measurement nucleus; ⁷ Li. Sample rotation speed; 10 kHz. Reference material: LiCl1M.

[0054]

[Table 2]

In the batteries A to G using the materials A to G,
The ⁷ Li nuclear magnetic resonance signal position indicated by the stored lithium in the negative electrode material occurs in the range of -10 to 40 ppm,
When no signal is generated in the range of 0 to 4 ppm, when all signal positions are generated in a lower magnetic field than 4 ppm, the capacity retention after 400 cycles is high, but the initial capacity is lower than that of the battery T using a graphite negative electrode. The capacity after 400 cycles is lower than that of the battery T. The signal is 5 ppm
When a lower magnetic field and a higher magnetic field than -10 ppm occur, the initial capacity is large, but the capacity retention after 400 cycles is small, and the discharge capacity after 400 cycles is smaller than that of the battery T. However, the signal occurs in the -10 to 40 ppm range,
In addition, when there is always one signal in the range of -10 to 4 ppm, the initial capacity is larger than that of the battery T, the capacity retention after 400 cycles is 70% or more, and the capacity after the cycle is larger than the battery T.

Further, the intensity of the signal generated in the range of -10 to 4 ppm indicating a lithium state having a strong ionic property is 1 to 10 times that of the signal appearing at 10 to 20 ppm indicating a lithium state having a strong covalent bond. If 40
The capacity after 0 cycles is the largest.

In the non-aqueous electrolyte secondary battery including the non-aqueous electrolyte, the separator, and the positive electrode and the negative electrode capable of inserting and extracting lithium, the negative electrode is formed on the entire surface around the core particles composed of solid phase A. Or a part thereof is a composite particle coated with a solid phase B, wherein the solid phase A contains tin as a constituent element, and the solid phase B is tin, which is a constituent element of the solid phase A, except for the constituent elements, Group 2 element of the periodic table, transition element, 1
A solid solution with at least one element selected from the group consisting of Group 2 and Group 13 elements and Group 14 elements excluding carbon;
Alternatively, a material that is an intermetallic compound is used, and a nuclear magnetic resonance signal of lithium occluded in the negative electrode material is generated in a range of −10 to 40 ppm with respect to lithium chloride standard, and a signal is necessarily generated in a range of −10 to 4 ppm. When one is present, shows excellent cycle characteristics with high capacity, furthermore, a signal generated in a nuclear magnetic resonance signal of lithium occluded in the negative electrode material in the range of -10 to 4 ppm with respect to lithium chloride, When the signal intensity is 1 to 10 times the intensity of the signal appearing at 10 to 20 ppm, a higher capacity and superior cycle characteristics are exhibited.

When the solid phase A is tin (Sn), the elements constituting the negative electrode material used in this embodiment are Mg as a Group 2 element, Fe and Mo as a transition element, Zn and Cd as a Group 12 element. Although In was used as the Group 13 element and Pb was used as the Group 14 element, similar effects were obtained by using other Group elements.

The charge ratio of the constituent elements of the negative electrode material is not particularly limited, and the phases become two phases.
One phase (solid phase A) is a phase mainly composed of tin, and another phase (solid phase B) may partially or entirely cover the periphery thereof. Is not particularly limited. Furthermore, the phase A is not only composed of tin, but also composed of elements other than each element, for example, O, C, N, S, C
a, Mg, Al, Fe, W, V, Ti, Cu, Cr, C
This includes the case where trace elements such as o and P are present. The phase B is not only composed of the solid solution and the intermetallic compound shown in (Table 1), but also each element constituting the solid solution and the intermetallic compound and other elements, for example, O, C,
N, S, Ca, Mg, Al, Fe, W, V, Ti, C
This includes the case where elements such as u, Cr, Co, and P are present in trace amounts.

[0060]

According to the present invention, in a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte, a separator, and a positive electrode and a negative electrode capable of inserting and extracting lithium, the negative electrode is formed on the entire surface around the core particles composed of solid phase A or A part of the composite particles is coated with a solid phase B. The solid phase A contains tin as a constituent element, and the solid phase B has a periodic structure except for tin as a constituent element of the solid phase A and the constituent elements. Group 2 element, transition element, group 12 and 1
Using a material that is a solid solution with at least one element selected from the group consisting of Group 3 elements and Group 14 elements excluding carbon, or an intermetallic compound, the nuclear magnetic resonance signal of lithium occluded in the negative electrode material is Occurs in the range of -10 to 40 ppm with respect to the lithium chloride standard, and -10 to
A non-aqueous electrolyte secondary battery, which always has one signal in the range of 4 ppm. Further, the nuclear magnetic resonance signal of lithium stored in the negative electrode material is such that a signal generated in a range of -10 to 4 ppm with respect to lithium chloride is 1 to 10 times as strong as a signal appearing at 10 to 20 ppm. A non-aqueous electrolyte secondary battery characterized by a higher capacity and better cycle characteristics than a non-aqueous electrolyte battery using a conventional carbon material as a negative electrode material.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical battery according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulating packing 4 Electrode plate group 5 Positive plate 5a Positive lead 6 Negative plate 6a Negative lead 7 Separator 8 Insulation ring

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H029 AJ03 AJ05 AK03 AL01 AM03 AM04 AM05 AM12 AM16 BJ02 BJ14 DJ12 DJ16 DJ17 HJ01 HJ02 HJ13

Claims (2)

[Claims] 1. A non-aqueous electrolyte secondary battery including a non-aqueous electrolyte, a separator, and a positive electrode and a negative electrode capable of inserting and extracting lithium, wherein the negative electrode is formed on the entire surface around the core particles composed of solid phase A or A part of the composite particles is coated with a solid phase B. The solid phase A contains tin as a constituent element, and the solid phase B has a periodic structure except for tin as a constituent element of the solid phase A and the constituent elements. Group 2 element, transition element, group 12 and 1
Using a material that is a solid solution with at least one element selected from the group consisting of Group 3 elements and Group 14 elements excluding carbon, or a material that is an intermetallic compound, a nuclear magnetic resonance signal of lithium occluded in the negative electrode material is obtained. Occurs in the range of -10 to 40 ppm with respect to the lithium chloride standard, and -10 to
A non-aqueous electrolyte secondary battery having at least one signal in the range of 4 ppm. 2. The nuclear magnetic resonance signal of lithium stored in the negative electrode material is -10 to 4 with respect to lithium chloride standard.
ppm and -10 to 20 ppm, and -1
A signal having a range of 0 to 4 ppm is 10 to 20 p.
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the intensity of the signal is 1 to 10 times that of a signal in a pm range.