JP2002367602A - Nonaqueous electrolyte secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary cell with small variation of volume at charging and discharging even a negative electrode activator with high capacity is used. SOLUTION: The nonaqueous electrolyte secondary cell comprises a positive electrode and a negative electrode capable of charging and discharging, and a nonaqueous electrolyte. The negative electrode contains at least one material chosen from metals or an alloy capable of stocking and releasing lithium as an activator when charging and discharging, of which, porosity is not less than 50% and not more than 90% at the time it is formed. At least one or more kinds of metals are chosen from Al, Si, Sn, an the alloy is Lix TiαSnβSiγ (where, 0<=x<=10, 0.1<=α<=10, 0.1<=β<=10, 0.1<=γ<=30).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a negative electrode of a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art A non-aqueous electrolyte secondary battery using lithium or a lithium compound as a negative electrode is expected to have a high voltage and a high energy density, and much research has been conducted. The positive electrode active material of the non-aqueous electrolyte secondary battery is LiMn ₂ O ₄ , LiCoO ₂ ,
LiNiO ₂ , V ₂ O ₅ , Cr ₂ O ₅ , MnO ₂ , TiS ₂ , M
Transition metal oxides such as oS ₂ and transition metal chalcogen compounds are known. These have a layered or tunnel structure and can occlude and release lithium ions. On the other hand, as the negative electrode active material, many studies have been made of metallic lithium. However, there has been a problem that dendritic lithium precipitates on the lithium surface during charging, and the charge / discharge efficiency is reduced or an internal short circuit occurs due to contact with the positive electrode.

As a means for solving such a problem, the dendritic growth of lithium is suppressed, and lithium ions are occluded.
Attempts have been made to use a lithium alloy, such as a lithium-aluminum alloy, which can be released, using a negative electrode. However, the alloy negative electrode has a problem that when deep charge and discharge are repeated, the size of the electrode is reduced, and the capacity is accordingly reduced. Under such circumstances, a lithium ion battery using a graphite-based carbon material which can reversibly occlude and release lithium, and has excellent cycleability and safety as a negative electrode has been put to practical use.

When graphite is used as a negative electrode active material, its theoretical capacity is 372 mAh / g. In the above-mentioned lithium-ion battery currently in practical use, the charge / discharge capacity of the negative electrode active material is actually used at 350 mAh / g. That is, it can be said that the battery using graphite as the negative electrode active material has almost reached the capacity limit at present. In addition, graphite has a low theoretical density of 2.2 g / cc, and when actually incorporated into a battery as a negative electrode sheet, the density further decreases.Therefore, it is desirable to use a metal material with a higher capacity per volume as the negative electrode. It is rare.

Under such circumstances, a patent application for a technique using a metal oxide for the negative electrode has been filed for the purpose of further increasing the capacity. For example, it has been shown that crystalline SnO and SnO2 have higher capacities than conventional WO2 (JP-A-7-122274, JP-A-7-2352).
No. 93). In addition, SnSiO3 or SnSi1
A proposal has been made to improve the cycle characteristics by using an amorphous oxide such as -xPxO3 for the negative electrode.
-288123).

The inventor has also proposed that nitric acid, sulfuric acid, hydrogen sulfate, thiocyanic acid, cyanide, cyanic acid, carbonic acid, hydrogen carbonate, hydrogen borate, hydrogen phosphate, selenic acid, hydrogen selenate, telluric acid, hydrogen tellurate, Metal salts or metalloid salts containing at least one selected from the group consisting of tungstic acid, molybdic acid, titanic acid, chromic acid, zirconic acid, niobic acid, tantalic acid, manganic acid, and vanadic acid are used in non-aqueous secondary batteries. As a negative electrode material having a high capacity and an excellent cycle life (Japanese Patent Application No. Hei 9-132298).

Further, (Si, Ge, Sn, Pb, B
i, P, B, Ga, In, Al, As, Sb, Zn, I
A crystalline compound containing at least two elements selected from the group consisting of r, Mg, Ca, Sr, and Ba and at least one element selected from the group consisting of oxygen, sulfur, selenium, and tellurium has a high capacity. (Japanese Patent Application No. 9-163285) also proposed a negative electrode material having excellent cycle life.

On the other hand, instead of metal oxides, various alloy materials have been proposed for the purpose of increasing the discharge capacity per volume and suppressing the irreversible capacity at the time of initial charge (Japanese Patent Laid-Open No. 09-2).
No. 46472).

Furthermore, the inventors have proposed Li _x M ¹ _a M ² (M ¹ is Ti, Z) as an alloy having a high capacity and excellent cycle characteristics.
r, V, Sr, Ba, Y, La, Cr, Mo, W, M
n, Co, Ir, Ni, at least one element selected from the element group m ¹ consisting of Cu, and Fe, M ² is M
g, Ca, at least Al, In, Si, Sn, Pb, are selected from an element group consisting m ² consisting of Sb, and Bi 1
Species elements, M ¹ and M ² are different elements, and 0 ≦ x ≦ 1
0, 0.1 ≦ a ≦ 10. However, when M ¹ consists only of Fe, 2 ≦ a ≦ 10. ) And further comprises at least two phases, each phase being M ³ cM ⁴ and M ⁵ dM ⁶ (M ³ and M ⁵ are each at least one selected from the above element group m ¹⁾ , M ⁴ and M ⁶ are each at least one element selected from the above element group m ² , and 0.25 ≦ c <3;
1 ≦ d ≦ 10 and c <d. ) Was proposed (JP-A-12-133261).

[0010]

However, the trend toward more advanced functions of portable equipment and the use of large batteries such as electric vehicles is now becoming even more active, and more and more batteries are being used as driving power supplies. Demand for longer life has increased. In response to such a demand, the above-mentioned negative electrode material is
At present, sufficient cyclability has not yet been achieved. As described above, the reversibility of charge and discharge can be improved by devising the composition and phase structure of the alloy material. However, as a problem common to metals and alloys capable of storing lithium, a large change in volume during charge and discharge has not been solved.

[0011] The expansion coefficient of the active material at the time of charging is calculated based on crystallographic or metallurgical values.
When the active material is Sn, the metallurgical Li
Has a maximum insertion of 4.4 mol. On the other hand, from the crystal lattice volume, the theoretical volume expansion coefficient after insertion before lithium insertion is 358%. When the negative electrode active material having such a large expansion coefficient is manufactured by a conventional electrode configuration or method, the electrode body expands or undergoes a large change in shape, particularly during charging. When a practical battery is configured with conventional electrodes, particularly, the deformation of the electrode body during charging and discharging and the deterioration of the cycle characteristics due to the non-uniform existence of the electrolyte, and in the worst case, the deformation of the battery appearance May result.

The present invention has been made in view of such a demand, and has been made to realize a non-aqueous electrolyte secondary battery in which no lithium dendrite is generated even during charge and discharge and the cycle life is significantly improved.

[0013]

Means for Solving the Problems It is possible to prevent the above-mentioned problems such as deformation of the electrode body due to expansion and contraction during charge and discharge, deterioration of cycle characteristics due to non-uniform existence of the electrolyte, and deformation of the battery appearance. The present invention provides a negative electrode of a nonaqueous electrolyte secondary battery having excellent cycle characteristics. Therefore, the non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery including a chargeable and dischargeable positive electrode and a negative electrode, and a non-aqueous electrolyte, wherein the negative electrode absorbs and releases lithium ions. At least one of a metal and an alloy is used as an active material, and the porosity of the negative electrode is 50% by volume or more and 90% by volume or less.

At this time, the metal is Al, Si or Sn.
It is effective to include at least one selected from the group consisting of:

The alloy is Li _x TiαSnβSiγ.
(However, 0 ≦ x ≦ 10, 0.1 ≦ α ≦ 10, 0.
1 ≦ β ≦ 10 and 0.1 ≦ γ ≦ 30. ) Is effective.

The alloy is CoSn or Cu6Sn
It is effective to include at least one of the following.

In the above, the negative electrode can have an active material obtained by porous plating the negative electrode substrate.

Further, the negative electrode can have a structure in which the active material is made into a particle state, and the particles are applied to a negative electrode substrate and then sintered to be in a porous state.

Further, the negative electrode can have a porous metal current collector carrying an active material. Further, the negative electrode may include a sponge-like foamed metal such as a foamed metal, a punching metal, and an expanded metal that supports an active material. Further, it is effective that the material of the porous metal current collector is at least one selected from copper and nickel.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can prevent the deformation of the electrode body due to expansion and contraction during charging and discharging, the deterioration of the cycle characteristics due to the non-uniform existence of the electrolyte, and the deformation of the battery appearance. Thus, an attempt was made to provide a negative electrode of a nonaqueous electrolyte secondary battery having excellent cycle characteristics.

A nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including a chargeable / dischargeable positive electrode and negative electrode, and a nonaqueous electrolyte, wherein the negative electrode stores and releases lithium ions. At least one of a metal and an alloy is used as an active material, and the porosity of the negative electrode is 50% by volume or more and 90% by volume or less. The mechanism for suppressing deformation of the electrode body and non-uniformity of the presence of the electrolytic solution during charging and discharging according to the present invention is as follows.

When a metal or an alloy capable of electrochemically occluding lithium is used as the negative electrode active material, MxLi (M: a metal or alloy capable of occluding lithium) as a charge product is charged before charging. In general, the volume is increased as compared to the M of FIG. For example, in the case of metal Sn, when lithium is occluded in the maximum amount, Li4.4Sn is obtained, and the volume increase rate by charging in this case is 3.58 times. On the other hand, when the carbon material that stores lithium by the intercalation reaction is, for example, graphite, the volume increase rate is about 10%.
%. Thus, when a metal or alloy capable of electrochemically storing lithium is used as the negative electrode active material,
High capacity, but large volume change during charging.

Therefore, when an electrode plate having an excessively low porosity is formed, the negative electrode active material expands during charging due to expansion.
Changes in the shape or breakage of the electrode body occur. In addition, with the large change in the volume of the electrode, the state of impregnation of the electrode with the electrolyte becomes non-uniform, and the electrochemical reaction in the electrode does not proceed homogeneously, and the part where the charge / discharge reaction is performed smoothly and so on. Is not generated. As a result, a part that deviates from the utilization rate and the charging depth assumed at the time of design occurs, and a part that exceeds the utilization rate and the charging depth allowed from the viewpoint of cycle life occurs. In particular, at the time of charging, metallic lithium is generated as a part of the anode in a part of the negative electrode, and as a result, the cycle characteristics may be deteriorated.

On the other hand, when the electrode plate is formed in a state where the porosity is excessively high, a sufficient space can be secured for the volume change of the active material at the time of charging / discharging. In addition, the current collecting property at the time of charging and discharging becomes insufficient, and as a result, the cycle property is deteriorated. Therefore, the porosity of the negative electrode has an appropriate range.
From the above, it has been found that an electrode having 90% by volume or less is a suitable range for the battery of the present invention.

At this time, it is preferable that the metal used for the negative electrode active material includes at least one selected from Al, Si and Sn, and the alloy is Li
_x TiαSnβSiγ (where 0 ≦ x ≦ 10, 0.
1 ≦ α ≦ 10, 0.1 ≦ β ≦ 10, 0.1 ≦ γ ≦ 30
It is. ) Have been found to be preferred. Among them, it has been found that CoSn or Cu ₆ Sn gives excellent characteristics.

Preferred methods for producing these metal and alloy materials are a gas atomization method and a mechanical alloy method. In addition, a liquid quenching method, an ion beam sputtering method, a vacuum evaporation method, a plating method, and a gas phase chemical reaction method can be applied.

Further, when the diameter of the alloy particles exceeds 45 μm, since the actual negative electrode sheet has a thickness of about 80 μm, the surface of the negative electrode has many irregularities, which adversely affects the battery characteristics. A particularly preferred particle size is 30 μm or less.

Further, a negative electrode can be prepared from an active material obtained by porous plating a negative electrode substrate. As the plating method, an electroless plating method, an electroplating method, a molten salt electrolytic method, or the like can be applied.

Further, as the separator used in the present invention, it is effective to use a microporous thin film having high ion permeability, predetermined mechanical strength, and electronic insulation. Desirable materials are polypropylene resin and polyethylene resin from the viewpoints of organic solvent resistance and hydrophobicity, and aramid resin alone or a laminate or composite of these resins from the viewpoint of heat resistance. Moreover, the thickness of the separator can be 5 to 100 μm,
In particular, 5 to 20 μm is preferable. The porosity is determined by physical properties such as ion permeability and viscosity of the electrolyte, or separation.
It is determined according to the mechanical properties such as strength and elongation of the sheet itself, but is preferably 20 to 80%.

In the present invention, it is desirable to use a lithium-containing transition metal oxide as the positive electrode active material. In particular, Li _x CoO ² , Li _x NiO ² , Li ^x MnO ² , Li
^{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 = N
a, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu,
(At least one of Zn, Al, Cr, Pb, Sb, and B), (where x = 0 to 1.2, y = 0 to 0.9, z =
2.0-2.3) is desirable. Here, the above x value is
This is a value before the start of charge / discharge, and increases / decreases due to charge / discharge. However, transition metal chalcogenide, vanadium oxide and its lithium compound, niobium oxide and its lithium compound, conjugated polymer using an organic conductive substance, it is also desirable to use other positive electrode material such as Chevrel phase compound, It is also possible to use a mixture of a plurality of different positive electrode materials. The average particle diameter of the positive electrode active material particles is preferably 1 to 30 μm.

The conductive agent for the positive electrode used in the present invention must be an electron conductive material which does not cause a chemical change at the charge / 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 amount of the conductive agent to be added is preferably 1 to 50% by weight with respect to the positive electrode material, and more preferably
% By weight is preferred. For carbon and graphite,
15% by weight is particularly preferred.

The positive electrode binder used in the present invention includes polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PV
DF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FE
P), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-
Tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-
Chlorotrifluoroethylene copolymer (ECTFE),
A vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, a vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, an ethylene-acrylic acid copolymer or a (Na ⁺ ) ion cross-linked product of the above-mentioned material, 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 or the above material (Na ⁺ ) ion crosslinked product is desirably used, and these materials can be used alone or as a mixture. Among these materials, more preferred materials are polyvinylidene fluoride (PVDF),
Polytetrafluoroethylene (PTFE).

The positive electrode current collector used in the present invention must be an electron conductor that does not cause a chemical change in the charge and discharge potential of the positive electrode material used. As a material, in addition to stainless steel, aluminum, titanium, carbon, conductive resin, and the like, aluminum or stainless steel whose surface is coated with carbon or titanium is used. Of these, aluminum or aluminum alloy is particularly preferred. 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 fiber group, a nonwoven fabric, or the like is used. The thickness is 1-5
A thing of 00 μm is used.

The negative electrode of the present invention may be made of a carbon material having reversibility to charge and discharge, aluminum, various alloys mainly composed of aluminum, metallic lithium, and various materials such as SnO2. Metal oxide can be used.

As the binder for the negative electrode used in the present invention, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PV
DF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FE
P), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-
Tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-
Chlorotrifluoroethylene copolymer (ECTFE),
A vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, a vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, an ethylene-acrylic acid copolymer or a (Na ⁺ ) ion cross-linked product of the above-mentioned material, 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 or the above material (Na ⁺ ) ion crosslinked product is preferred, and these materials can be used alone or as a mixture. Among these materials, more preferred materials are styrene butadiene rubber, polyvinylidene fluoride, ethylene-acrylic acid copolymer or (Na ⁺ ) ion cross-linked product of the above-mentioned material, ethylene-methacrylic acid copolymer or the above-mentioned material. (Na ⁺ ) ion crosslinked product, ethylene-methyl acrylate copolymer or (Na ⁺ )
⁺ ) An ion cross-linked product, an ethylene-methyl methacrylate copolymer or a (Na ⁺ ) ion cross-linked product of the above material.

The current collector for the negative electrode used in the present invention must be an electron conductor that does not cause a chemical change in the constructed battery, and may be made of stainless steel, nickel,
In addition to copper, titanium, carbon, and a conductive resin, it is preferable that the surface of copper or stainless steel is coated with carbon, nickel, or titanium, and 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, a porous material, a foam, or a molded product of a fiber group is used. The thickness is 1 to 500 µm
Use

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 cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), and diethyl carbonate. (DEC), chain carbonates such as ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC), aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate, and γ-butyrolactone Γ-lactones, 1,2-dimethoxyethane (DME), 1,2-
Chain ethers such as diethoxyethane (DEE) and ethoxymethoxyethane (EME), tetrahydrofuran,
Cyclic ethers such as 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphate triester, trimethoxymethane, dioxolane derivative , Sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propanesultone, anisole, dimethylsulfoxide, N Aprotic organic solvents such as -methylpyrrolidone are preferred. These may 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.

As a lithium salt dissolved in these solvents,
Is LiClO^Four, LiBF^Four, LiPF⁶, LiAlC
l^Four, LiSbF⁶, LiSCN, LiCl, LiCF^Three
 SO ^Three, LiCF^ThreeCO^Two, Li (CF^ThreeSO^Two)^Two, Li
AsF⁶, LiN (CF^ThreeSO^Two)^Two, LiB^TenCl^Ten, Low
Lithium aliphatic carboxylate, LiCl, LiBr, L
iI, lithium chloroborane, lithium lithium tetraphenylborate
And imides are desirable.
Can be used alone or in combination of two or more
But especially LiPF⁶Is more preferable.

A particularly preferred non-aqueous electrolyte in the present invention is an electrolyte containing at least ethylene carbonate and LiPF ⁶ as a supporting salt. The amount of these electrolytes to be added to the battery is limited by the amount 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 preferably 0.2 to 2 mol / l. In particular,
More preferably, it is 0.5 to 1.5 mol / l.
Further, it is effective to add another compound to the electrolyte for the purpose of improving the discharge and charge / discharge characteristics. Triethyl phosphite, triethanolamine, cyclic ether,
Preferred are ethylenediamine, n-glyme, pyridine, hexaphosphoric triamide, nitrobenzene derivatives, crown ethers, quaternary ammonium salts, ethylene glycol dialkyl ether, and phosphate esters.

As the electrode mixture, a filler, a dispersant, an ion conductor, a pressure enhancer, and other various additives are used in addition to the conductive agent and the binder. The filler must be a material that does not cause a chemical change in the constructed battery.
An olefin-based polymer such as polypropylene or polyethylene, glass, or carbon fiber is used. The addition amount of the filler is preferably 0 to 30% by weight based on the electrode mixture.

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. Further, the shape of the battery can be applied to any of coin type, button type, sheet type, laminated type, cylindrical type, flat type, square type, large type used for electric vehicles and the like. In addition, the nonaqueous electrolyte secondary battery of the present invention can be used for portable information terminals, portable electronic devices, home small power storage devices, motorcycles, electric vehicles, hybrid electric vehicles, and the like, but is not particularly limited thereto. Not necessarily.
Hereinafter, the present invention will be described in more detail with reference to Examples. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0042]

EXAMPLES (Method of Manufacturing Test Cell) In order to clarify the characteristics of the electrode shown in the present invention, a test cell shown in FIG. 1 was manufactured. This creation method and evaluation method will be described. The produced electrode was punched out to a diameter of 16 mm to obtain a test electrode 1. This was placed in case 2 and microporous polypropylene separator 3 was placed on the electrode body.

A mixture of ethylene carbonate (EC) and dimethoxyethane (DME) at a volume ratio of 1: 1 was used as a solvent, and lithium perchlorate (LiCl
O ₄ ) was dissolved to prepare an electrolyte having a concentration of 1 mol / l. This electrolytic solution was injected onto the separator. On top of this,
A metal Li having a diameter of 17.5 mm was adhered to the inside, and a sealing plate 6 with a gasket 5 made of polypropylene was placed on the outer peripheral portion, and sealed to form a test cell.

(Evaluation Method) In this example, the cycle characteristics were measured at 45 ° C., and the effect on the expansion and contraction of the electrodes described above was verified. For the above test cell,
At a constant current of 5 mA, the test electrode is energized until the voltage of the test electrode becomes 0 V with respect to the Li counter electrode. That is, cathode polarization (corresponding to charging when the active material electrode is viewed as a negative electrode). Electric current was applied until the voltage reached 1.5 V, that is, anodic polarization (corresponding to discharge when the active material electrode was viewed as a negative electrode). Thereafter, this charge / discharge was repeated.

The evaluation contents include the thickness at the time of forming the electrode,
The porosity, the thickness at the time of charging, the porosity, and the maintenance rate of the discharge capacity after 100 cycles by the above-described charge / discharge method were determined. In addition, about all the test cells shown in the Example,
After repeating charge / discharge for 100 cycles, the test electrode plate was taken out and observed. As a result, no metal lithium was precipitated on the electrode plate surface. From this result, it was confirmed that dendrite did not occur in the negative electrode of this example. After performing the above-described cathode polarization, the test electrode plate was subjected to ICP analysis, and the amount of Li contained in the active material did not exceed the range described in the claims.

(Production of Cylindrical Battery and Evaluation Method) Next, a cylindrical battery shown in FIG. 2 was produced in order to evaluate the cycle characteristics of the battery using the above-mentioned electrode as the negative electrode.

First, a battery was manufactured according to the following procedure.
LiMn2O4 as a positive electrode active material is composed of Li2CO3 and Mn.
3O4 was mixed at a predetermined molar ratio and synthesized by heating at 900 ° C. Furthermore, what classified this into 100 mesh or less was used as the positive electrode active material. Cathode active material 1
To 100 g, 10 g of carbon powder as a conductive agent and 8 g of polytetrafluoroethylene dispersion as a binder and pure water were added to form a paste, applied to a titanium core material, dried and rolled to form a positive electrode. Obtained. Microporous polypropylene was used as the material of the separator.

Between a positive electrode plate 1 having a positive electrode lead 4 of the same material as the core material attached by spot welding and a negative electrode plate 2 having a negative electrode lead 5 of the same material as the core material attached by spot welding, The electrode body was formed by spirally winding the whole through a wide band-shaped separator 3. Further, insulating plates 6 and 7 made of polypropylene are arranged on the upper and lower sides of the electrode body, respectively, inserted into the battery case 8, and a step portion is formed on the upper portion of the battery case 8, and then the above-mentioned electrolytic solution is injected. , Sealing plate 9
To make a battery.

The purpose of these batteries is to verify by high-rate charge / discharge at a high temperature, at a test temperature of 45 ° C., a charge / discharge current of 4.0 mA / cm ² (corresponding to a 30-minute rate), and a charge / discharge voltage range of 4. A charge / discharge cycle test was performed at 3 V to 2.6 V, and 2
The capacity retention ratio at the 100th cycle with respect to the first cycle of the discharge capacity at the cycle was determined.

(Embodiment 1-7) In the present embodiment, a configuration in which an active material is contained in a porous metal body will be described as a configuration of an electrode body. A urethane resin foam having a thickness of 0.1 mm, a width of 500 mm, and a length of 20 m having 60 continuous pores per inch is prepared, and Cu is deposited on the average by 0.1 μm by pretreatment by an electroless plating method. Was. After electroplating, by burning and reducing the resin, the porosity is 90% C
u metal porous body was obtained.

Next, in order to obtain the porous metal body containing each of the active material powders shown in Table 1, the following method was carried out. The average particle size of each powder used is 5 μm.

[0052]

[Table 1]

Each powder and polyvinylidene fluoride as a binder were mixed at a weight ratio of 90: 5.
N-dimethylformamide was added to paste. This paste is filled into the above-mentioned porous Cu metal body,
And dried. At this time, the filling amount is adjusted so that the porosity of the dried electrode body is from 62% to 70%, and the thickness is 100%.
A μm electrode body was obtained. As a comparative example, the above electrode body was molded by pressure to produce an electrode body having a porosity of 40% and a thickness of 50 μm.

Table 1 shows the porosity of the electrode body at the time of construction, the porosity of the electrode body at the time of initial charging, and the cycle deterioration rate. The electrodes of the examples maintain the thickness of 100 μm even during charging, and the decrease in porosity is only 40%. In addition, 1
The capacity retention after the 00 cycle also showed good results.

On the other hand, in the electrode of the comparative example, the thickness at the time of charging greatly increased compared to the thickness at the time of construction, and the porosity was 10
%. Further, the capacity retention rate after 100 cycles was as low as 40% to 50%. This result is considered as follows.

That is, regarding the expansion coefficient of the active material at the time of charging, when the active material is Sn or Si, Li is based on 1 mole of each.
Assuming that the maximum insertion amount of each is 4.4 moles, the theoretical volume expansion coefficients after insertion with respect to before Li insertion are 358% and 405%, respectively. Further, the alloys shown in Table 1 also expand upon charging. Therefore, Table 1
As described above, in the battery of the embodiment having a large porosity, the expanded volume is absorbed in the space in the electrode, and the change in the form of the electrode due to charging and discharging is reduced without changing the electrode thickness.
As a result, the cycle characteristics were also improved.

On the other hand, the battery of the comparative example has a low porosity at the time of construction, making it difficult to absorb the expansion of the active material during charging in the space inside the electrode. Brought. Further, such a large change in the electrode configuration at the time of charging / discharging causes deterioration of the cycle characteristics, and the porosity at the time of charging is 10%, which makes supply of the electrolytic solution to the active material inconvenient. It became.

In the present embodiment, the above-described alloy composition has been described. However, similar results were obtained when other combinations of α, β, and γ were used.

(Embodiments 8-10) In this embodiment, a case where porous plating is performed on a negative electrode substrate will be described.

First, a microporous polyethylene film (porosity: 80%, average pore diameter: 0.5 μm, thickness: 100 μm) was prepared, and the metal or alloy shown in Table 2 was coated thereon by electroless plating. - Thereafter, a metal or alloy porous plated electrode having a porosity of 70% was obtained by burning and reducing the polyethylene resin. As a comparative example, a Sn metal porous plating electrode having a porosity of 30% was produced. The porosity was determined using a mercury porosimeter method.

[0061]

[Table 2]

The manufacturing method of the electroless plating in this embodiment is as follows. The solution composition for Sn plating is 0.1
0.1 molar SnSO4 in H2SO4 aqueous solution
Was used. The above-mentioned microporous polyethylene membrane was immersed in 100 ml of this plating solution. Bath temperature is 40 ° C
And the immersion time was 15 minutes. As the composition of each alloy plating solution, CoSn and CuSO4 having a molar concentration of CoSn and Cu6Sn5, respectively, were added to the above solution.
Was additionally dissolved. Other conditions are the same as those of the Sn plating. The obtained electrode was subjected to a quantitative analysis of Sn by a chemical analysis method to determine the amount of Sn. The method of manufacturing the test cell and the method of testing the discharge cycle are the same as those of the above-described embodiment.

After the cathode polarization in the 100th cycle was completed, the test cell was disassembled.
Was not observed. 1g of active material in 1st cycle
Table 2 shows the discharge capacity per battery and the capacity retention rate at the 100th cycle. As a result, it was found that the battery of the present invention constituted in this example had a high capacity retention ratio due to charge / discharge cycles.

As another method for producing the negative electrode of the present invention, the same study was conducted on a vacuum deposition method, an ion plating method, a sputtering method, a chemical vapor reaction method, and an electrolytic plating method. It was confirmed that the capacity retention rate was high.

(Examples 11-17) In order to obtain a porous structure by applying active material particles to a negative electrode substrate and then sintering, the following method was used. The active material particles shown in Table 3 were used. The average particle size of each powder is 1
μm.

[0066]

[Table 3]

Each powder was mixed with carboxymethyl cellulose as a thickening binder at a weight ratio of 95: 5,
Further, water was added to form a paste. This paste is Cu
The composition was applied to a metal foil substrate, dried in a hydrogen stream at 200 ° C., and sintered to form active material particles. The temperature in this sintering step was 200 ° C. for metal Sn and Sn alloy, 560 ° C. for metal Al, and 1200 ° C. for metal Si and Si alloy. The porosity of the electrode after sintering was adjusted to 70% based on the paste concentration, the filling amount, and the drying rate, to obtain a sintered porous electrode having a thickness of 100 μm.

As a comparative example, the above electrode body was molded under pressure to produce an electrode body having a porosity of 40% and a thickness of 50 μm. Table 3 shows the porosity of the electrode body in the configuration, the porosity of the electrode body at the time of initial charging, and the cycle deterioration rate. The electrodes of the examples maintain the thickness of 100 μm even during charging, and the decrease in porosity is only 40%. Furthermore, the capacity retention rate after 100 cycles also showed good results.

On the other hand, in the electrode of the comparative example, the thickness at the time of charging greatly increased compared to the thickness at the time of construction, and the porosity was 10%.
%. Further, the capacity retention rate after 100 cycles was an extremely low value of 10% to 20%.

As shown in Table 3, as shown in Table 3, in Examples having a relatively large porosity, the expanded volume was absorbed into the space in the electrode, and the electrode was charged and discharged without changing the electrode thickness. There is very little change in the electrode configuration with it,
As a result, it is considered that the cycle characteristics were also good.

On the other hand, in the comparative example, the porosity at the time of construction was low, and it was difficult to absorb the expansion of the active material during charging in the space in the electrode, resulting in a significant increase in the electrode thickness. Further, such a large change in the electrode configuration at the time of charging / discharging causes deterioration of the cycle characteristics, and the porosity at the time of charging is as low as 10%. It is thought that supply became difficult.

In particular, since the sintering porous electrode is in a state in which the particles are firmly fixed by sintering, the sintering is poor in flexibility with respect to morphological change due to expansion during charging. Can be presumed to have been destroyed. In addition,
In the present embodiment, the above alloy composition has been described, but similar results are obtained when other combinations of α, β, and γ are used.

(Examples 18-24) In this example, the performance of the electrodes fabricated in Examples 11-17 was verified in a cylindrical battery by designing the performance of a practical battery.
The production of the negative electrode plate is the same as the method shown in Example 11-17 and Comparative Example 11-17. The method for manufacturing the positive electrode and the method for manufacturing the battery were as described above.

Table 4 shows the porosity of the negative electrode body at the time of construction, the porosity of the negative electrode body at the time of initial charging, and the cycle deterioration rate. The thickness of the negative electrode of the example was maintained at 100 μm even during charging, and the decrease in porosity was only 40%. In addition, 100
The capacity retention after cycling also showed good results.

[0075]

[Table 4]

On the other hand, in the negative electrode of the comparative example, the thickness at the time of charging increased greatly with respect to the thickness at the time of construction, and the porosity was reduced to 10%. Further, the capacity retention rate after 100 cycles was as low as 10% to 20%. The results of these comparative examples were inferior to those of the test cells described above. It is considered that when a negative electrode that is expanded and a positive electrode body composed of a metal oxide powder are used, the function of alleviating the expansion of the negative electrode is low, and as a result, the battery is greatly deteriorated. Also, in the case of a coin battery, the battery case is deformed by a relatively low internal pressure, but in the case of a cylindrical battery, the fact that the battery case is not easily deformed also led to the difference in the result. As described above, it has been found that it is substantially difficult to construct a practical battery when the electrode that causes expansion is used as the negative electrode.

In this example, the above alloy composition was described, but similar results were obtained when other combinations of α, β, and γ were used. In the above embodiment, the case where a cylindrical battery is used has been described.However, the present invention is not limited to this structure, and the same applies to a secondary battery having a rectangular or flat shape. It was confirmed that the invention had an effect.

In this example, LiMn 2 O was used as the positive electrode.
4, but LiCoO2, LiNiO2,
Needless to say, the same effect can be obtained when combined with a positive electrode having reversibility with respect to charge and discharge such as the above.

Example 25 In this example, the porosity of the negative electrode was examined in detail.

In the present embodiment, as in the case of the first embodiment, a description will be given of a configuration in which a porous metal body contains an active material as a configuration of an electrode body. A urethane resin foam having a thickness of 0.1 mm, a width of 500 mm, and a length of 20 m having 60 continuous pores per inch is prepared.
u was deposited on average 0.1 μm. Cu is added to this resin porous body.
Electroplating was performed. After the electroplating, a Cu metal porous body having a porosity of 90% was obtained by burning and reducing the resin. Next, in order to obtain a porous metal body containing each of the active material powders shown in Table 5, the following method was used.
The average particle size of each powder used is 5 μm.

[0081]

[Table 5]

Each powder and polyvinylidene fluoride as a binder were mixed at a weight ratio of 90: 5.
-Dimethylformamide was added to paste. The paste was filled in the above-mentioned porous Cu metal body and dried at 100 ° C. At this time, the filling amount was adjusted so that the porosity of the electrode body after drying became 70% to 80%, and the thickness was 100 μm.
m electrode bodies were obtained. Further, the above-mentioned electrode body is pressure-molded to have a porosity of 40% to 80% and a thickness of 50 μm.
From 100 μm was produced. Table 5 shows the porosity of the electrode body in the configuration, the porosity of the electrode body at the time of initial charging, and the cycle deterioration rate.

The porosity of the electrode of the embodiment is 50% to 9%.
In the case of 0%, the capacity retention rate after 100 cycles was good. When the porosity is lower than 50%, the porosity after 100 cycles is in a very low state, the amount of the electrolyte is insufficient, and it is considered that the charge / discharge reaction becomes non-uniform. When the porosity exceeds 90%, the porosity is excessively high, and the current collecting property during charging and discharging is insufficient, which is considered to be a cause of deterioration. In this embodiment, the case where Sn and Si are used as the active materials has been described.
1 or Li _x TiαSnβSiγ (where 0 ≦
x ≦ 10, 0.1 ≦ α ≦ 10, 0.1 ≦ β ≦ 10,
0.1 ≦ γ ≦ 30. ) And Co
It was confirmed that the same result was obtained for Sn or Cu6Sn.

[0084]

According to the present invention, as described above, a non-aqueous electrolyte secondary battery having a longer service life and high reliability can be obtained by using a negative electrode having an extremely excellent cycle life. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a test cell for evaluating electrode characteristics of a negative electrode material of the present invention.

FIG. 2 is a schematic cross-sectional view of a cylindrical battery for evaluating the battery characteristics of the negative electrode of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test electrode 2 Case 3 Separator 4 Metal lithium 5 Gasket 6 Sealing plate 11 Positive electrode 12 Negative electrode of the present invention 13 Separator 14 Positive electrode lead plate 15 Negative electrode lead plate 16 Upper insulating plate 17 Lower insulating plate 18 Battery case 19 Sealing plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Nitta 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (Reference) 5H017 AA03 AS10 BB16 DD01 DD05 5H029 AJ04 AJ05 AK03 AL12 AM03 AM04 AM05 AM07 BJ02 BJ03 CJ02 CJ22 DJ13 HJ02 HJ09 5H050 AA07 AA09 BA17 CA08 CA09 CB12 DA03 FA09 GA02 GA22 HA02 HA09

Claims (7)

[Claims] 1. A non-aqueous electrolyte secondary battery including a chargeable / dischargeable positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the negative electrode activates at least one of a metal or an alloy that absorbs and releases lithium ions. A non-aqueous electrolyte secondary battery, wherein the material has a porosity of 50% by volume or more and 90% by volume or less. 2. The metal according to claim 1, wherein the metal includes at least one selected from Al, Si and Sn.
The non-aqueous electrolyte secondary battery according to the above. 3. The alloy is Li _x TiαSnβSiγ.
(However, 0 ≦ x ≦ 10, 0.1 ≦ α ≦ 10, 0.1
≦ β ≦ 10 and 0.1 ≦ γ ≦ 30. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein: 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the alloy contains at least one of CoSn and Cu ₆ Sn. 5. The negative electrode according to claim 1, wherein the negative electrode has an active material obtained by porous plating on a negative electrode substrate.
The non-aqueous electrolyte secondary battery according to the above. 6. The negative electrode has a structure in which the active material is made into a particle state, and the particles are applied to a negative electrode substrate, and then sintered to form a porous state.
Or the non-aqueous electrolyte secondary battery according to 4. 7. The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode has a current collector made of a porous metal carrying an active material.