JP2001093524A - Negative electrode for a non-aqueous electrolytic secondary cell, preparation thereof, and non-aqueous electrolytic secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a non-aqueous electrolytic secondary cell with high energy density, in which short-circuiting by dendrites is not caused and a cycle life is excellent. SOLUTION: The non-aqueous electrolytic secondary cell is an active material having A-phase expressed in the formula 1: M1aM2 and having composition satisfying 0.25<=a<3 and B-phase expressed in the formula 2 M1bM2 and having composition satisfying 1<=b and a<b, where M1 and M1 are each at least one element selected from (m1) group consisting of Na, K, Rb, Cs, Ce, Ti, Zr, Hf, V, Nb, Ta, Ca, Sr, Ba, Y, La, Cr, Mo, W, Mn, Tc, Ru,Os, Co, Rh, Ir, Ni, Pd, Cu, Ag and Fe, and M2 and M2 are each at leasts one element selected rom (m2) group consisting of Al, Ga, In, Si, Ge, Sn, Pb, Sb and Bi.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a negative electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, and 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 can be expected to have a high voltage and a high energy density, and much research has been conducted. The positive electrode active material of the nonaqueous electrolyte secondary battery includes a transition metal oxide and a chalcogen compound, for example, LiMn ₂ O ₄ , LiCoO ₂ , L
iNiO ₂ , V ₂ O ₅ , Cr ₂ O ₅ , MnO ₂ , TiS ₂ , M
oS _{2 and the} like are known. These have a layered structure or a tunnel structure, and have a crystal structure through which lithium ions can enter and exit.

On the other hand, lithium metal has been widely studied as a negative electrode active material. However, when metallic lithium is used, there is a problem that dendritic lithium, ie, dendrite, precipitates on the lithium surface during charging, which lowers charging / discharging efficiency or causes internal short-circuiting due to contact with the positive electrode. Therefore,
Investigations have been made to use a lithium-based alloy capable of absorbing and releasing lithium, such as a lithium-aluminum alloy, as a negative electrode active material, while suppressing dendritic growth of lithium. However, when deep charge / discharge is repeated, the electrode material becomes finer, which causes a problem in cycle characteristics.

At present, a lithium ion battery using a graphite-based carbon material for a negative electrode, which has a smaller capacity than metallic lithium and a lithium-based alloy, can reversibly insert and extract lithium, and has excellent cycle characteristics and safety. Has been put to practical use. However, when a graphite-based carbon material is used for the negative electrode, its practical capacity is the theoretical capacity (372 mAh / g).
350 mAh / g. The theoretical density is 2.
The density is as low as 2 g / cc, and if a sheet-shaped negative electrode is actually used, the density is further reduced. Therefore, in order to further increase the capacity of the battery, it is necessary to use a metal-based inorganic material having a high capacity per unit volume as the negative electrode active material.

[0005]

When a metal-based inorganic material is used for a negative electrode active material, the active material is pulverized due to repetition of expansion and contraction accompanying occlusion and release of lithium. The finely divided active material loses physical contact with another active material or a conductive agent in the negative electrode, and loses electron conductivity. Therefore, the active material is apparently inactive and is a major factor in capacity reduction.

Therefore, a technique of coexisting a phase occluding lithium and a phase not occluding lithium in one particle to relieve stress in a charged state (occluding state) by a phase not absorbing lithium (Japanese Patent Laid-Open No. 11-86854). ), A technique of coexisting two or more phases that occlude lithium in one particle to relieve stress due to structural change of each phase during occlusion of lithium (Japanese Unexamined Patent Publication No. 11-86)
No. 853), which states that reducing the crystal size improves the effect of stress relaxation. However, the effect is insufficient.

Even when a plurality of phases coexist in the active material particles and the expansion stress is released to the grain boundaries by making the crystal size fine, the stress in the active material particles is non-uniform if the expansion coefficients of the respective phases are largely different. become. For this reason, it is considered that pulverization occurs in some of the phases having a large expansion stress and is separated from the active material particles.
If one phase is a simple element of an element that easily alloys with lithium,
The tendency for this phenomenon to occur is even greater.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to achieve both high capacity and long life of a battery by suppressing pulverization accompanying expansion and contraction of a negative electrode active material. That is, the present invention provides an A phase represented by the formula (1): M ¹ _a M ² , which satisfies 0.25 ≦ a <3, and a formula (2): M ¹ ′ _b M ² ′ An active material having a B phase having a composition satisfying 1 ≦ b and a <b, wherein M ¹ and M ¹ ′ are Na, K, Rb, Cs, Ce, Ti, Zr, H
f, V, Nb, Ta, Ca, Sr, Ba, Y, La, C
r, Mo, W, Mn, Tc, Ru, Os, Co, Rh,
Consists of Ir, Ni, Pd, Cu, Ag and Fe (m
¹⁾ is at least one element selected from the group, M ²
And M ² ′ are Al, Ga, In, Si, Ge, Sn,
The present invention relates to a negative electrode active material for a non-aqueous electrolyte secondary battery, which is at least one element selected from the group (m ² ) consisting of Pb, Sb and Bi.

[0009] The active material comprises 20 to 80% by weight of phase A,
20-80% by weight of phase and phase 0 other than phase A and phase B
Preferably, it consists of 〜50% by weight. Also, A phase and B
It preferably has an interface in contact with the phase. Also, A
50% by weight or more of the phase contains the B phase in the B phase matrix.
Preferably, they are dispersed in contact. Also, A
Phase or phase B is the matrix of the other phase
Dispersed in islands with an average particle size of 0.05 to 20 μm
Or both the A phase and the B phase each have an average particle size of 1
It is preferably in the form of particles of up to 20 μm. A phase
And the B phase have an intricate lamellar structure
Is preferred. In addition, at least one of the A phase and the B phase
Are dispersed like needles with an aspect ratio of 1.5 or more
Is preferred. In addition, the A phase observed in an arbitrary cross section and
The average cross-sectional area of the B phase crystal grains is 10 ^-7cm^TwoIs below
Is preferred. The average particle size of the active material is 45.
It is preferably not more than μm.

[0010] In the active material, the A phase may be NaS.
n_Two, KSn_Two, SrSn_Three, BaSn_Three, LaSn_Two, C
eSn_Three, ZrSn_Two, MnSn_Two, CoSn_Two, PdSn
_TwoAnd FeSn_TwoAt least selected from the group consisting of
One phase, B phase is Na_TwoSn, KSn, La_TwoS
n, Zr_ThreeSn_Two, Zr_FourSn, V_ThreeSn, Nb_ThreeSn, T
a_ThreeSn, MnSn, Mn_TwoSn, Mn_ThreeSn, FeS
n, Fe_1.3Sn, Fe_ThreeSn, CoSn, Co_ThreeSn_Two,
Ni_ThreeSn_Two, Ni_ThreeSn, Cu₆Sn_Five, Cu_ThreeSn, Cu
_FourSn, Ti₆Sn_FiveAnd Ti_TwoSelect from the group consisting of Sn
Preferably, it is at least one type of phase.

In the above active material, the phase A may be Na
At least one phase selected from the group consisting of Sn, KSn, FeSn, CoSn, and PdSn, wherein the B phase is Na ₂ Sn, La ₂ Sn, Zr ₃ Sn ₂ , Zr ₄ Sn,
V ₃ Sn, Nb ₃ Sn, Ta ₃ Sn, Mn ₂ Sn, Mn ₃ S
n, Fe _1.3 Sn, Fe ₃ Sn, Co ₃ Sn ₂ , Ni ₃ S
n ₂ , Ni ₃ Sn, Cu ₆ Sn ₅ , Cu ₃ Sn, Cu ₄ Sn,
Preferably, it is at least one phase selected from the group consisting of Ti ₆ Sn ₅ and Ti ₂ Sn.

[0012] In the active material, the A phase may be Ti
_At least one phase selected from the group consisting of ₆ Sn ₅ and Cu ₆ Sn ₅ , wherein the B phase is Na ₂ Sn, La ₂ S
n, Zr ₃ Sn ₂ , Zr ₄ Sn, V ₃ Sn, Nb ₃ Sn, T
a ₃ Sn, Mn ₂ Sn, Mn ₃ Sn, Ti ₃ Sn, Cu ₃ S
n, Fe ₃ Sn, Fe ₆ Sn, Fe ₁₂ Sn, Co ₃ Sn ₂ ,
_{Ni 3 Sn 2, Ni 3 Sn} , is preferably at least one phase selected from the group consisting of Cu ₄ Sn and Ti ₂ Sn.

[0013] In the above active material, the phase A may be Na.
₂ Sn, K ₂ Sn, Mg ₂ Sn, Ca ₂ Sn, SrSn, B
at least one phase selected from the group consisting of a ₂ Sn, La ₂ Sn and Ti ₂ Sn, wherein the B phase is Mn ₃ S
n, Fe ₃ Sn, Fe ₆ Sn, Fe ₁₂ Sn, Ni ₃ Sn,
It is preferably at least one phase selected from the group consisting of Ni ₆ Sn, Cu ₃ Sn, Cu ₄ Sn and Ti ₃ Sn.

In the above-mentioned active material, the phase A may be Na
Si_Two, CaSi_Two, SrSi_Two, BaSi_Two, YSi_Two,
LaSi_Two, CeSi_Two, TiSi_Two, ZrSi_Two, VSi
_Two, NbSi_Two, TaSi_Two, CrSi_Two, MoSi_Two, W
Si_Two, MnSi_Two, CoSi _Two, CuSi_Two, FeSi_Two
And NiSi_TwoAt least selected from the group consisting of
One phase, B phase is NaSi, KSi, Mg_TwoS
i, Ca_TwoSi, Ce_TwoSi, TiSi, Ti_FiveSi_Three, Z
rSi, V_ThreeSi, Nb_FiveSi_Three, Ta_TwoSi, CrSi,
Cr_TwoSi, Mo_ThreeSi, W_ThreeSi_Two, MnSi, Mn_FiveS
i_Three, Mn_ThreeSi, FeSi, Fe_FiveSi_Three, Fe_ThreeSi,
CoSi, Co_TwoSi, Co_ThreeSi, NiSi, Ni_ThreeS
i_Two, Ni_TwoSi, CuSi, Cu₆Si_Five, Cu_ThreeSi
And Cu_FourAt least one selected from the group consisting of Si
Preferably, it is a seed phase.

[0015] In the active material, the A phase may be Na.
Si, KSi, CaSi, BaSi, TiSi, ZrS
i, CrSi, MnSi, FeSi, CoSi, PdS
i, selected from the group consisting of NiSi and CuSi
At least one phase, wherein the B phase is Mg_TwoSi, Ca_Two
Si, Ce_TwoSi, Ti_FiveSi_Three, V_ThreeSi, Nb_FiveSi_Three,
Ta_TwoSi, Cr_TwoSi, Mo_ThreeSi, W_ThreeSi_Two, Mn_FiveS
i_Three, Mn_ThreeSi, Fe _FiveSi_Three, Fe_ThreeSi, Co_TwoSi,
Co_ThreeSi, Ni_ThreeSi_Two, Ni_TwoSi, Cu₆Si_Five, Cu
_ThreeSi and Cu_FourSelected from the group consisting of Si
Both are preferably one kind of phase.

[0016] In the active material, the A phase may be Ti
_{5 Si 3, Nb 5 Si 3} , W 3 Si 2, Mn 5 Si 3, Fe 5 S
at least one phase selected from the group consisting of i ₃ and Cu ₆ Si ₅ , wherein the B phase is Mg ₂ Si, Ca ₂ S
i, Ce ₂ Si, V ₃ Si, Ta ₂ Si, Cr ₂ Si, Mo
_{3 Si, Mn 3 Si, Fe} 3 Si, Co 2 Si, Co 3 S
Preferably, it is at least one phase selected from the group consisting of i, Ni ₂ Si, Cu ₃ Si and Cu ₄ Si.

In the above-mentioned active material, the A phase may be composed of Mg
_TwoSi, Ca_TwoSi, SrSi, Ce _TwoSi, Cr_TwoSi,
Co_TwoSi, Pd_TwoSi and Cu_TwoFrom the group consisting of Si
At least one selected phase, wherein phase B is V_ThreeS
i, Mo_ThreeSi, Mn_ThreeSi, Fe_ThreeSi, Co_ThreeSi, C
u_ThreeSi and Cu_FourA few selected from the group consisting of Si
Preferably it is at least one phase.

In the above-mentioned active material, the phase A is Ca
Al_Four, CaAl_Two, SrAl_Four, BaAl_Four, BaA
l_Two, LaAl_Four, LaAl_Two, CeAl_Four, CeAl_Two,
TiAl _Three, ZrAl_Three, ZrAl_Two, VAl_Three, V_FiveA
l₈, NbAl_Three, TaAl_Three, CrAl_Four, MoAl_Three,
WAl_Four, MnAl_Four, MnAl_Three, Co_TwoAl_Five, CuA
l_Two, FeAl_Three, FeAl_Two, NiAl_ThreeAnd Ni_TwoA
l_ThreeAt least one phase selected from the group consisting of
B phase is SrAl, BaAl, LaAl, La_ThreeA
l_Two, CeAl, Ce_ThreeAl_Two, TiAl, ZrAl, Z
r_TwoAl, Mo_ThreeAl, MnAl, FeAl, Fe_ThreeA
1, CoAl, NiAl, CuAl and Cu_FourAl_ThreeYo
At least one phase selected from the group consisting of
Is preferred.

In the above active material, the phase A is Sr.
Al, BaAl, LaAl, CeAl, TiAl, Zr
At least one phase selected from the group consisting of Al, MnAl, FeAl, CoAl, NiAl and CuAl, wherein the B phase is La ₃ Al ₂ , Ce ₃ Al ₂ , Zr ₂ A
Preferably, it is at least one phase selected from the group consisting of 1, Mo ₃ Al, Fe ₃ Al and Cu ₄ Al ₃ .

The present invention also relates to a method for producing the active material, wherein the active material is synthesized by a plasma method, an atomizing method, a quenching method, a casting method, a mechanical alloy method, or a mechanochemical method. Further, the present invention provides a step of mixing various raw material elements in a block, plate or granule at an arbitrary ratio and casting the mixture in an arc melting furnace. 0.5-5mmφ, injection pressure 5
The present invention relates to a method for producing the active material, comprising a step of forming spherical particles by a gas atomization method at 0 to 300 kgf / cm ² . Further, the present invention relates to a non-aqueous electrolyte secondary battery including a chargeable / dischargeable positive electrode, a non-aqueous electrolyte, and a negative electrode made of the active material. In the present invention, the active material refers to a material including an electrochemically active portion, and a material including an inactive portion is also included in the active material.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The active material of the present invention has the formula (1): M
¹ _a M ² , 0.25 ≦ a <3, preferably 0.5
A phase having a composition satisfying ≦ a ≦ 2 and formula (2): M ¹ ′
_b M ² ′, 1 ≦ b and a <b, preferably 1 ≦ b
It has a B phase having a composition satisfying b ≦ 5 and a <b. When the active material has the A phase and the B phase, pulverization of the active material is suppressed, and deterioration of the battery due to charge / discharge cycles is suppressed. This is presumably because the difference between the expansion stress of the A phase during the occlusion of lithium and that of the B phase is small, so that the expansion stress in the entire active material is uniformly reduced. In the formula (1), a
Is less than 0.25, the expansion stress of the A phase is extremely large, and the powder is easily pulverized. When it is 3 or more, the Li reaction amount per unit weight and volume becomes too small, resulting in low capacity. In addition, in equation (2), when b is less than 1, B
The phase expansion stress also increases, and both phases expand. When the phase exceeds 5, the stress difference between the A phase and the B phase increases. The balance between the relaxation of the expansion stress caused by the presence of a plurality of phases that occlude lithium and the uniformization of the expansion stress in the entire active material by reducing the difference between the expansion stress of the A phase and that of the B phase. , A and b are 1 <(b / a) <10,
Further, it is preferable to satisfy 1.5 ≦ (b / a) ≦ 5.

In the formulas (1) and (2), M ¹ and M ¹ ′ are Na, K, Rb, Cs, Ce, Ti, Zr, H
f, V, Nb, Ta, Ca, Sr, Ba, Y, La, C
r, Mo, W, Mn, Tc, Ru, Os, Co, Rh,
Consists of Ir, Ni, Pd, Cu, Ag and Fe (m
¹ ) At least one element selected from the group. Although a plurality of elements may be contained, one phase is preferably made of an element selected from one kind of (M ¹ ) group.
If the A-phase and B-phase is composed of an element selected from each of only one kind (m ¹⁾ groups, among the (m ¹⁾ group, T
i, Zr, Sr, Ba, Mn, Co, Ni, Cu or Fe, preferably Ti, Mn, Co, Cu
Alternatively, it is particularly preferable to be composed of Fe.

In equations (1) and (2), M^Twoand
M^Two'Is Al, Ga, In, Si, Ge, Sn, Pb,
Consisting of Sb and Bi (m^Two) A few selected from the group
It is at least one element. Even if it contains multiple elements
Good, but one phase consists of one (m ^Two) Elements selected from the group
It preferably comprises A phase and B phase respectively
Only one type (m^Two) If it consists of elements selected from the group,
(M^Two) Group, Al, In, Si, Ge, Sn
Or Pb, Al, Si or S
It is particularly preferred that it consists of n.

The active material having the A phase and the B phase is the A phase 2
0 to 80% by weight, further 30 to 60% by weight, phase B 20
-80% by weight, furthermore 40-70% by weight and 0-50% by weight of phases other than the phases A and B, furthermore 5-30.
Preferably it consists of% by weight. Further, it is preferable to have an interface where the A phase and the B phase are in contact. This is because the contact interface between the A phase and the B phase plays an important role in relaxing the stress during the occlusion of lithium and securing a lithium transmission path in the active material particles. Therefore, it is preferable that the number of contact interfaces is large.
Preferably, at least 50% by weight of the phase is dispersed in the B-phase matrix in contact with the B-phase. Also, A
When either one of the phase and the B phase is dispersed in the form of islands in the matrix of the other phase, or when both the A phase and the B phase are each dispersed in the form of islands or from particles In this case, the average particle size of each of the islands and the particles is 0.1.
05 to 20 μm, further 0.1 to 5 μm and 0.1
-20 μm, further 1-20 μm, especially 1-5 μm
It is preferable that Here, the average particle diameter is determined, for example, from the average of the diameters of the cross sections of the islands or particles observed in the cross section obtained when the active material particles are cut along an arbitrary plane. Further, as a more preferable structure, A
A lamella structure in which the phase and the B phase are intertwined, that is, a structure in which the cross section of the active material is intertwined with each other like a mesh. In order to obtain a lamellar structure, it is necessary to synthesize by a quenching method such as a roll quenching method or an atomizing method and to perform a heat treatment. In order to further reduce the difference between the expansion stress of the A phase and that of the B phase and to suppress the pulverization of the active material more efficiently, at least one of the A phase and the B phase has an aspect ratio of 1.5 or more. It is preferably dispersed in a needle shape. Here, the aspect ratio refers to the ratio of the length and width of the acicular particles, for example, the length and width of the cross section of the acicular particles observed in a cross section obtained when the active material particles are cut on an arbitrary surface. From the average of the ratios

Average grain size of crystal grains constituting phase A and phase B
The diameter should be 13 μm or less, and further 0.1 to 5 μm.
Is preferred. When the average particle size exceeds 13 μm,
The crystal grains themselves are crushed by the expansion stress during occlusion of titanium.
The active material tends to be pulverized. Also,
Average breakage of A-phase and B-phase crystal grains observed in the desired cross section
Area is 10 ^-7cm^TwoBelow, and even 10^-9-10^-8c
m^TwoIt is preferred that Also, the average particle size of the active material particles
The diameter of the negative electrode of a non-aqueous electrolyte secondary battery is generally about 80 μm.
45 μm or less, and even 5
It is preferably from 30 to 30 μm. Particle size exceeds 40μm
As a result, the surface of the sheet-shaped negative electrode becomes uneven,
Properties tend to decrease.

In the active material of the present invention, in addition to the phase A and the phase B,
And yet another phase, such as the formula: M¹" _xM^Two"
A phase having a composition satisfying b <x may be present. This
Where M¹"Is the above (m¹) At least selected from group
One kind of element, M^Two"Is the above (m^Two) Selected from the group
And at least one element. For example, (m¹)
At least one phase consisting of only the elements selected from the group
You may. In this case, the discharge capacity decreases slightly,
Further, active material particles having a longer life can be obtained. Ma
(M^Two) Some phases consist only of elements selected from the group
However, due to the characteristics of the battery, 10% by weight of the total active material
The following is preferred.

In the above-mentioned active material, the phase A is NaS
n ₂ , KSn ₂ , SrSn ₃ , BaSn ₃ , LaSn ₂ , C
eSn ₃ , ZrSn ₂ , MnSn ₂ , CoSn ₂ , PdSn
₂ or FeSn ₂ alone or in combination of two or more,
The phases are Na ₂ Sn, KSn, La ₂ Sn, Zr ₃ Sn ₂ , Z
r ₄ Sn, V ₃ Sn, Nb ₃ Sn, Ta ₃ Sn, MnSn,
Mn ₂ Sn, Mn ₃ Sn, FeSn, Fe _1.3 Sn, Fe ₃
Sn, CoSn, Co ₃ Sn ₂ , Ni ₃ Sn ₂ , Ni ₃ S
_{n, Cu 6 Sn 5, Cu} 3 Sn, Cu 4 Sn, is preferably Ti ₆ Sn ₅ or Ti ₂ Sn alone or in combination.

In the above-mentioned active material, the phase A is Na
Sn, KSn, FeSn, CoSn or PdSn
In the case of Germany or two or more, the phase B is Na_TwoSn, L
a_TwoSn, Zr_ThreeSn_Two, Zr_FourSn, V_ThreeSn, Nb_ThreeS
n, Ta_ThreeSn, Mn_TwoSn, Mn_ThreeSn, Fe_1.3Sn,
Fe_ThreeSn, Co_ThreeSn_Two, Ni_ThreeSn_Two, Ni_ThreeSn, Cu
₆Sn_Five, Cu_ThreeSn, Cu_FourSn, Ti₆Sn_FiveOr Ti
_TwoIt is preferable that Sn is used alone or in combination of two or more.

In the above-mentioned active material, the phase A is Ti
_{When 6} Sn ₅ or Cu ₆ Sn ₅ is used alone or in combination,
The B phase is composed of Na ₂ Sn, La ₂ Sn, Zr ₃ Sn ₂ , and Zr ₄ S
n, V ₃ Sn, Nb ₃ Sn, Ta ₃ Sn, Mn ₂ Sn, Mn
₃ Sn, Ti ₃ Sn, Cu ₃ Sn, Fe ₃ Sn, Fe ₆ S
n, Fe ₁₂ Sn, Co ₃ Sn ₂ , Ni ₃ Sn ₂ , Ni ₃ Sn,
It is preferable that Cu ₄ Sn or Ti ₂ Sn be used alone or in combination.

In the above active material, the phase A may be Na
₂ Sn, K ₂ Sn, Mg ₂ Sn, Ca ₂ Sn, SrSn, B
a ₂ Sn, if it is La ₂ Sn or Ti ₂ Sn alone or two or more, B _{phase, Mn 3 Sn, Fe 3 Sn} , Fe
₆ Sn, Fe ₁₂ Sn, Ni ₃ Sn, Ni ₆ Sn, Cu ₃ S
It is preferable that n, Cu ₄ Sn or Ti ₃ Sn be used alone or in combination.

In the above-mentioned active material, the phase A is Na
Si_Two, CaSi_Two, SrSi_Two, BaSi_Two, YSi_Two,
LaSi_Two, CeSi_Two, TiSi_Two, ZrSi_Two, VSi
_Two, NbSi_Two, TaSi_Two, CrSi_Two, MoSi_Two, W
Si_Two, MnSi_Two, CoSi _Two, CuSi_Two, FeSi_Two
Or NiSi_TwoB alone or in combination of two or more
The phases are NaSi, KSi, Mg_TwoSi, Ca_TwoSi, Ce
_TwoSi, TiSi, Ti_FiveSi_Three, ZrSi, V_ThreeSi, N
b_FiveSi_Three, Ta_TwoSi, CrSi, Cr_TwoSi, Mo_ThreeS
i, W_ThreeSi_Two, MnSi, Mn_FiveSi_Three, Mn_ThreeSi, F
eSi, Fe_FiveSi_Three, Fe_ThreeSi, CoSi, Co_TwoS
i, Co_ThreeSi, NiSi, Ni_ThreeSi_Two, Ni_TwoSi, C
uSi, Cu₆Si_Five, Cu_ThreeSi or Cu_FourSi alone
Alternatively, two or more kinds are preferable.

In the above-mentioned active material, the phase A is Na
Si, KSi, CaSi, BaSi, TiSi, ZrS
i, CrSi, MnSi, FeSi, CoSi, PdS
i, NiSi or CuSi alone or in combination of two or more
If the B phase is Mg_TwoSi, Ca_TwoSi, Ce_TwoSi,
Ti_FiveSi_Three, V_ThreeSi, Nb_FiveSi_Three, Ta_TwoSi, Cr _Two
Si, Mo_ThreeSi, W_ThreeSi_Two, Mn_FiveSi_Three, Mn_ThreeSi,
Fe_FiveSi_Three, Fe_ThreeSi, Co_TwoSi, Co_ThreeSi, Ni_Three
Si_Two, Ni_TwoSi, Cu₆Si_Five, Cu_ThreeSi or Cu_Four
It is preferable that Si is used alone or in combination.

In the above active material, the phase A is Ti
_FiveSi_Three, Nb_FiveSi_Three, W_ThreeSi_Two, Mn_FiveSi_Three, Fe_FiveS
i_ThreeOr Cu₆Si_FiveIs a single or two or more
If the B phase is Mg_TwoSi, Ca_TwoSi, Ce_TwoSi, V_ThreeS
i, Ta_TwoSi, Cr_TwoSi, Mo _ThreeSi, Mn_ThreeSi, F
e_ThreeSi, Co_TwoSi, Co_ThreeSi, Ni_TwoSi, Cu_ThreeS
i or Cu_FourSi alone or two or more types
preferable.

Further, in the above active material, the phase A may be composed of Mg
_TwoSi, Ca_TwoSi, SrSi, Ce _TwoSi, Cr_TwoSi,
Co_TwoSi, Pd_TwoSi or Cu_TwoSi alone or 2
If more than one species, phase B_ThreeSi, Mo_ThreeSi, Mn
_ThreeSi, Fe_ThreeSi, Co_ThreeSi, Cu_ThreeSi or Cu_Four
It is preferable that Si is used alone or in combination.

In the above active material, the phase A is Ca
Al ₄ , CaAl ₂ , SrAl ₄ , BaAl ₄ , BaA
_{l 2, LaAl 4, LaAl 2} , CeAl 4, CeAl 2, T
iAl ₃ , ZrAl ₃ , ZrAl ₂ , VAl ₃ , V ₅ Al ₈ ,
NbAl ₃ , TaAl ₃ , CrAl ₄ , MoAl ₃ , WAl
₄ , MnAl ₄ , MnAl ₃ , Co ₂ Al ₅ , CuAl ₂ , F
When eAl ₃ , FeAl ₂ , NiAl ₃ or Ni ₂ Al ₃ is used alone or in combination of two or more, the B phase is SrAl, Ba
Al, LaAl, La ₃ Al ₂ , CeAl, Ce ₃ Al ₂ ,
_{TiAl, ZrAl, Zr 2 Al,} Mo 3 Al, MnA
1, FeAl, Fe ₃ Al, CoAl, NiAl, Cu
It is preferable that Al or Cu ₄ Al _{3 be used} alone or in combination.

In the above active material, the phase A is Sr
Al, BaAl, LaAl, CeAl, TiAl, Zr
Al, MnAl, FeAl, CoAl, NiAl or
When CuAl is used alone or in combination of two or more, the B phase is L
a_ThreeAl_Two, Ce_ThreeAl_Two, Zr _TwoAl, Mo_ThreeAl, Fe_Three
Al or Cu_FourAl_ThreeSingly or two or more
Is preferred.

The active material according to the present invention may be, for example, a method in which simple elements of various raw materials are mixed in an arbitrary ratio in the form of a block, a plate, or a granule and subjected to a predetermined heat treatment, for example, a plasma method, an atomizing method, a quenching method or a casting method. It can be synthesized by using the methods alone or in combination. Also,
Alternatively, it can be synthesized by a mechanical alloy method or a mechanochemical method. According to the plasma method, minute particles are easily obtained, and according to the atomizing method, minute spherical particles are easily obtained, and mass productivity is good. According to the quenching method, particles having a fine structure are easily obtained, and according to the casting method, synthesis is easy. According to the mechanical alloy method or the mechanochemical method, fine particles and a fine structure can be realized. As a more preferable method for producing the active material, for example, a step of mixing simple substances of various raw materials in an arbitrary ratio in a lump, a plate, or a granule, and casting in an arc melting furnace, Bottom, injection nozzle diameter 0.5-5mmφ, injection pressure 50-300kgf
/ Cm ² , which includes a step of forming spherical particles by a gas atomizing method.

The non-aqueous electrolyte secondary battery of the present invention can be obtained by preparing a negative electrode by a general method using the active material, and combining the negative electrode with a chargeable / dischargeable positive electrode and a non-aqueous electrolyte.

[0039]

EXAMPLES Next, the present invention will be described more specifically based on examples, but these do not limit the present invention. << Examples 1 to 65 >> A phase having an active material composition (composition of raw material elements) shown in Tables 1 to 3 and consisting of only an element selected from the A phase, the B phase, and the (m ² ) group (Tables 1 to 6) 3 shows the phase C.
In the column of the C phase, the numerical value in parentheses indicates the weight% of the C phase in the active material. Same in Table 4. ) And other phases (the indication of “-” in the row of other phases in Tables 1 to 3 does not mean that there is no other phase; the same applies in Table 4). It was prepared by the following procedure. Simple materials of various raw material elements were mixed in an arbitrary ratio in a lump, plate, or granule, and cast in an arc melting furnace. The obtained casting is placed under an argon atmosphere.
Spherical particles were formed by using a gas atomizing method. At this time,
Injection nozzle diameter is 1mmφ, injection pressure is 100kgf / cm
^{Was 2} . The obtained particles were passed through a 45-micron mesh sieve to obtain active material particles having an average particle size of 28 μm.

The obtained active material particles were analyzed by X-ray diffraction, and consisted of a plurality of phases shown in Table 1, and were selected from A-phase 30 to 65% by weight, B-phase 30 to 70% by weight, (m ² ) group. A phase (C phase) composed of only the selected elements (0 to 10% by weight) and another phase composed of 0 to 20% by weight were selected. When the selected active material particles were subjected to surface analysis by EPMA, the average particle size of the crystal grains was 0.3 to 13 for all the active material particles.
It was in the range of μm. The average sectional area of the crystal grains constituting the A phase and the B phase was 5 × 10 ⁻⁸ cm ² at the maximum.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

The states of the A phase and the B phase in the cross section of the obtained active material particles were as follows. That is, each active material had an interface where the A phase and the B phase were in contact with each other, and 50% by weight or more of the A phase was dispersed in the matrix of the B phase in a state of being in contact with the B phase. .

A test cell as shown in FIG. 1 was prepared by using the active material as a negative electrode material. To 7.5 g of the active material powder, 2 g of graphite powder as a conductive agent and 0.5 g of polyethylene powder as a binder were mixed to form a mixture. The mixture 0.
1 g was pressure-molded to a diameter of 17.5 mm to form an electrode 1, which was placed in a case 3. A microporous polypropylene separator 7 was placed on the electrode. A 1: 1 by volume mixed solution of ethylene carbonate and dimethoxyethane in which lithium perchlorate (LiClO ₄ ) was dissolved so as to be 1 mol / liter was poured on the separator as a non-aqueous electrolyte.
On this, metal lithium 4 having a diameter of 17.5 mm was adhered on the inside, and a sealing plate 6 with a polypropylene gasket 8 attached on the outer peripheral portion was placed thereon to form a test cell. FIG.
Among them, 2 indicates a current collector of the electrode 1 and 5 indicates a current collector of metallic lithium.

The test cell was cathode-polarized at a constant current of 0.5 mA until the electrode 1 became 0 V with respect to the lithium counter electrode (corresponding to charging when the active material electrode was viewed as a negative electrode). Anode polarization was performed until the voltage of the electrode reached 1.5 V (corresponding to discharge when the active material electrode was viewed as a negative electrode). Thereafter, cathodic polarization and anodic polarization were repeated. Tables 1 to 3 show the initial discharge capacity per 1 g of the active material at this time. Next, the test cell was disassembled, and the electrode 1 after cathode polarization and after repeating 10 times of cathode polarization and anodic polarization was taken out and observed. As a result, no deposition (dendrite) of metallic lithium on the electrode surface was observed.

Next, in order to evaluate the cycle characteristics of the battery using the active material for the negative electrode, a cylindrical battery shown in FIG. 2 was prepared. LiMn _1.8 Co _0.2 O ₄ , which is a positive electrode active material,
It was synthesized by mixing Li ₂ CO ₃ , Mn ₃ O _4, and CoCO ₃ at a predetermined molar ratio and heating at 900 ° C. Furthermore, what classified this into 100 mesh or less was used as the positive electrode active material. To 100 g of the positive electrode active material, 10 g of carbon powder as a conductive agent, 8 g of an aqueous dispersion of polytetrafluoroethylene as a binder, and 8 g of pure water as a resin component are added to form a paste, which is applied to a titanium core material. Then, drying and rolling were performed to obtain a positive electrode plate 11.

Next, each of the above active materials, graphite powder as a conductive agent, and a fluororesin (Teflon) binder as a binder were mixed at a weight ratio of 70:20:10, and a petroleum solvent was added. Into a paste, apply to the copper core,
It dried at 100 degreeC and the negative electrode plate 12 was obtained.

Between the positive electrode plate 11 having the positive electrode lead 14 of the same material as the core material attached by spot welding and the negative electrode plate 12 having the negative electrode lead 15 of the same material as the core material attached by spot welding, The whole was spirally wound with a band-shaped separator 13 wider than the plate. An upper insulating plate 16 and a lower insulating plate 17 made of polypropylene were arranged on the upper and lower sides of the wound material, respectively, and inserted into the battery case 18. Battery case 1
After forming a step on the top of 8, a non-aqueous electrolyte
A mixed solution of lithium carbonate and dimethoxyethane in a volume ratio of 1: 1 in which lithium perchlorate was dissolved at a molar ratio of 1: 1 was injected and sealed with a sealing plate 19 to complete the battery. Porous polypropylene was used for the separator 13. In FIG. 2, reference numeral 20 denotes a positive electrode terminal.

The obtained battery was tested at a test temperature of 30 ° C.
, Charge / discharge current 1 mA / cm ² , charge / discharge voltage range 4.3
A charge / discharge cycle test was performed at ~ 2.6V. Tables 1 to 3 show the capacity retention ratio at the 100th cycle with respect to the first cycle.

<< Comparative Examples 1 to 7 >> Particles of Sn alone and Al alone (average particle diameter 26 μm), particles composed only of Cu ₆ Sn ₅ phase, particles composed only of FeAl phase (all shown in Table 4) 28 μm, average grain size of crystal grains 2.1 μm)
And particles composed of an Mg ₂ Ge phase and a Mg single phase (average particle diameter 25 μm, average crystal grain diameter 3.2 μm, Mg ₂ G
e: Mg: 7: 3 (molar ratio), particles composed of Mg ₂ Sn phase and Mg single phase (average particle diameter 27 μm, average crystal particle diameter 5.3 μm, Mg ₂ Sn: Mg 8: 2) (Molar ratio)), particles composed of Mg ₂ Sn phase and Sn phase (average particle size 27 μm, average crystal particle size 5.3 μm, Mg ₂ S
In the case where n: Sn is 7: 3 (molar ratio)), the initial discharge capacity of the test cell and the capacity retention ratio at the 100th cycle with respect to the first cycle of the cylindrical battery are obtained in the same manner as in the example. Was. Table 4 shows the results.

[0052]

[Table 4]

Tables 1 to 4 show that the batteries using the active material according to the present invention for the negative electrode have higher capacities than the comparative examples, and the cycle characteristics are remarkably improved. In the above-described example, a cylindrical battery was manufactured. However, it has been confirmed that the same effect can be obtained in coin-type, square-type, and flat-type secondary batteries. Further, in the above embodiment, the gas atomizing method was adopted, but the plasma method, the quenching method, the casting method,
It has been confirmed that the same effect can be obtained even when the mechanical alloy method and the mechanochemical method are employed. Further, in the above example, LiMn _1.8 Co _0.2 O ₄ was used as the positive electrode. However, it has been confirmed that similar effects can be obtained when LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ or the like is used.

[0054]

According to the present invention, a non-aqueous electrolyte secondary battery having a high energy density, no short circuit due to dendrite, and excellent cycle life can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a test cell used in an example to evaluate characteristics of a negative electrode active material of the present invention.

FIG. 2 is a schematic cross-sectional view of a cylindrical battery used in an example to evaluate characteristics of a negative electrode active material of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode 2 Current collector of electrode 1 3 Case 4 Metal lithium 5 Current collector of metal lithium 6 Sealing plate 7 Microporous polypropylene separator 8 Gasket 11 Positive electrode plate 12 Negative electrode plate 13 Separator 14 Positive electrode lead 15 Negative electrode lead 16 Upper insulating plate 17 Lower insulating plate 18 Battery case 19 Sealing plate 20 Positive electrode terminal

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hideharu Takezawa 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5H003 AA04 BA00 BB02 BC06 BD02 BD04 5H014 AA02 EE10 HH01 HH08 5H029 AJ05 AK03 AL11 AM03 AM04 AM05 BJ02 BJ03 BJ14 CJ00 HJ01 HJ15

Claims (10)

[Claims] 1. Formula (1): M ¹ _a M ² , 0.25
A phase having a composition satisfying ≦ a <3 and formula (2): M ¹ ′
_b B having a composition represented by M ² ′ and satisfying 1 ≦ b and a <b
An active material having a phase, wherein M ¹ and M ¹ ′ are Na,
K, Rb, Cs, Ce, Ti, Zr, Hf, V, Nb,
Ta, Ca, Sr, Ba, Y, La, Cr, Mo, W,
Mn, Tc, Ru, Os, Co, Rh, Ir, Ni, P
at least one element selected from the group consisting of d, Cu, Ag, and Fe (m ¹ ); M ² and M ² ′
Represents Al, Ga, In, Si, Ge, Sn, Pb, Sb
A negative electrode active material for a non-aqueous electrolyte secondary battery, characterized in that it is at least one element selected from the group consisting of (m ² ) and Bi. 2. 20% to 80% by weight of phase A, 20 to 80% of phase B
% By weight and 0 to 50% by weight of phases other than the phases A and B
The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, comprising: 3. The phase A, wherein 50% by weight or more of the phase A is dispersed in a matrix of the phase B in contact with the phase B.
Or the negative electrode active material for a non-aqueous electrolyte secondary battery according to 2. 4. One of the phases A and B is dispersed in the matrix of the other phase in the form of islands having an average particle size of 0.05 to 20 μm, or both the A and B phases are dispersed. Comprises particles having an average particle size of 1 to 20 μm, respectively.
3. The negative electrode active material for a non-aqueous electrolyte secondary battery according to any one of 3. 5. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the A phase and the B phase have a lamellar structure in which they are intertwined with each other. 6. The non-aqueous electrolyte secondary according to claim 1, wherein the average cross-sectional area of the crystal grains of the A phase and the B phase observed in an arbitrary cross section is 10 ⁻⁷ cm ² or less. Negative active material for batteries. 7. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the average particle size of the active material is 45 μm or less. 8. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is synthesized by a plasma method, an atomizing method, a quenching method, a casting method, a mechanical alloy method, or a mechanochemical method. Manufacturing method of negative electrode active material. 9. A process of mixing various raw material elements in a lump, plate or granule at an arbitrary ratio and casting in an arc melting furnace. 5-5mmφ, injection pressure 50-300kgf / c
preparation of the negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, characterized in that it comprises a step of spherical particles by a gas atomizing method in m ^2. 10. A chargeable / dischargeable positive electrode, a non-aqueous electrolyte,
A nonaqueous electrolyte secondary battery comprising: a negative electrode comprising the negative electrode active material according to claim 1.