JP2003297339A - Positive electrode for non-aqueous electrolyte secondary battery and secondary battery using such positive electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode having a high energy density, an excellent heavy load characteristic, and an excellent low-temperature characteristic and safety and provide a non-aqueous electrolyte secondary battery using such a positive electrode. <P>SOLUTION: The positive electrode 3 includes positive electrode active material layers 15 and 16 located on the sides of a positive electrode current collector 13 and containing LiXMn<SB>2-</SB>YMYO<SB>4</SB>provided that the conditions 0.95≤x≤1.25 and 0.01≤y≤0.20 should be met (where M is one or more metals selected among Ti, Cr, Fe, Co, Ni, Zn, Al) and Li<SB>x</SB>Co<SB>1-y</SB>M<SB>y</SB>O<SB>2</SB>provided that the conditions 0.95≤x≤1.25 and 0.01≤y≤0.50 should be met (where M is one or more metals selected among Ti, Cr, Fe, Ni, Mn, Zn, Al, Mo, W), wherein the thickness T<SB>1</SB>of the positive electrode current collector 13 and the total (T<SB>2</SB>+T<SB>3</SB>) of the thicknesses of the positive electrode active material layers 15 and 16 should meet the conditions 2.5≤(T<SB>2</SB>+T<SB>3</SB>)/T<SB>1</SB>and (T<SB>2</SB>+T<SB>3</SB>)≤250 μm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the same.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries have higher energy density and longer life than conventional batteries, and are used as power sources for, for example, mobile phones and notebook personal computers.

In such a non-aqueous electrolyte secondary battery, for example, a carbonaceous material is used as the negative electrode active material, a lithium transition metal composite oxide is used as the positive electrode active material, and a non-aqueous electrolyte having a lithium salt as a supporting salt is used as the electrolyte. However, in particular, the positive electrode active material is an important constituent element that determines performance such as discharge capacity, discharge voltage, cycle life characteristics, and safety of the non-aqueous electrolyte secondary battery.

By the way, in a small non-aqueous electrolyte secondary battery currently on the market, lithium cobalt oxide having a layered structure is used as a positive electrode active material. However, lithium cobalt oxide is a rare metal, which is a raw material, and its price is unstable, and battery safety is low when it is overcharged. Therefore, there is a problem in using it alone as a positive electrode active material. Many.

Therefore, it has been considered to use, as a positive electrode active material, manganese, which has a large amount of reserves and is excellent in thermal stability at high temperatures, as a raw material and which has a low battery cost and a high battery safety. . However, since the lithium manganese oxide has a small battery capacity and is an active material having a spinel structure, it is known that the lithium ion diffusion coefficient is remarkably small, which is about 1/10 to 1/100 of that of the active material having a layered structure. ing.

Therefore, the heavy load characteristics and the low temperature characteristics are not always sufficient, and improvement of the heavy load characteristics and the low temperature characteristics has been earnestly desired. Further, improvement of energy density is also desired.

[0007]

The present invention has been completed based on the above circumstances, and is a positive electrode having high energy density, excellent heavy load characteristics, excellent low temperature characteristics, and high safety. And a non-aqueous electrolyte secondary battery using the same.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to develop a positive electrode that can solve the above problems and a non-aqueous electrolyte secondary battery using the positive electrode. As a result, high energy density, and by using a positive electrode active material obtained by mixing a lithium cobalt composite oxide having an excellent lithium diffusion rate and a lithium manganese composite oxide having high safety and high energy density, It was found that a non-aqueous electrolyte secondary battery having excellent heavy load characteristics, excellent low temperature characteristics, and high safety can be obtained, and the present invention has been completed.

[0009] Namely, a first aspect of the invention, on both sides of a cathode current _{collector, Li X Mn 2-Y M} Y O 4 (0.95 ≦ x ≦ 1.
25, 0.01 ≦ y ≦ 0.20, M is Ti, Cr, F
e, Co, Ni, Zn, at least one metal selected from Al) and Li _X Co _1-Y M _Y O ₂ (0.95
≦ x ≦ 1.25, 0.01 ≦ y ≦ 0.50, M is T
i, Cr, Fe, Ni, Mn, Zn, Al, Mo, W) and a positive electrode active material layer containing a positive electrode active material layer. Of the thickness T1 and the thickness of the positive electrode active material layer (T2 + T
3) and 2.5 ≦ (T2 + T3) / T1 and (T2
The positive electrode for a non-aqueous electrolyte secondary battery is characterized by satisfying the relationship of + T3) ≦ 250 μm.

According to a second aspect of the present invention, on both sides of the positive electrode current collector,
Li _X Mn _2-Y M _Y O ₄ (0.95 ≦ x ≦ 1.25,
0.01 ≦ y ≦ 0.20, M is Ti, Cr, Fe, C
o, Ni, Zn, at least one metal selected from Al) and Li _X Co _1-Y M _Y O ₂ (0.95 ≤ x ≤
1.25, 0.01 ≦ y ≦ 0.50, M is Ti, C
r, Fe, Ni, Mn, Zn, Al, Mo, W) and a negative electrode active material layer containing a positive electrode active material layer containing at least one metal selected from the group consisting of a negative electrode current collector and a negative electrode active material layer. In a non-aqueous electrolyte secondary battery including a negative electrode including a negative electrode and a non-aqueous electrolyte, the total thickness T1 of the positive electrode current collector and the positive electrode active material layer (T2 + T3) is 2.5 ≦. (T2 +
The non-aqueous electrolyte secondary battery is characterized by satisfying the relationship of T3) / T1 and (T2 + T3) ≦ 250 μm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a prismatic non-aqueous electrolyte secondary battery 1 according to an embodiment of the present invention. The prismatic non-aqueous electrolyte secondary battery 1 includes a positive electrode 3 and
A flat wound electrode group 2 in which a negative electrode 4 is wound via a separator 5 and a non-aqueous electrolytic solution (not shown) containing an electrolyte salt are housed in a battery case 6.

A battery lid 7 provided with a safety valve 8 is attached to the battery case 6 by laser welding, the positive electrode terminal 10 is connected to the positive electrode 3 via a positive electrode lead 11, and the negative electrode 4 is an inner wall of the battery case 6. Is electrically connected by contact with.

The positive electrode 3 is, for example, as shown in FIG.
For example, aluminum, titanium, or stainless steel positive electrode collection
A substance that absorbs and releases lithium ions on both sides of the electric body 13
A positive electrode active material layer 15 composed of a positive electrode mixture containing
16 is provided. This positive electrode active material layer 1
5 and 16 are Li as a positive electrode active material._XMn_2-YM_YO
_Four(0.95 ≤ x ≤ 1.25, 0.01 ≤ y ≤ 0.2
0, M are Ti, Cr, Fe, Co, Ni, Zn, Al
At least one metal selected from the above) and Li_XC
o_1-YM_YO₂(0.95 ≤ x ≤ 1.25, 0.01
≦ y ≦ 0.50, M is Ti, Cr, Fe, Ni, M
At least 1 selected from n, Zn, Al, Mo and W
And more than one kind of metal).

Lithium-manganese composite oxide, which is one of the positive electrode active materials, has a spinel structure, and ideally, lithium ions are in 4-coordinate 8a position and manganese ions are in 6-position.
It exists at the coordination 16d position. Lithium ions can move through a diffusion path composed of manganese oxygen octahedra, and from this feature, spinel structure type lithium manganese composite oxide can be used as a positive electrode active material of a non-aqueous electrolyte battery, and in particular, a non-aqueous electrolyte. It is suitable as a positive electrode active material for an electrolyte lithium secondary battery. Further, M is preferably Co or Ni. This is because the battery capacity is improved by using Co and Ni.

The other lithium cobalt composite oxide has a layered structure. Lithium ions can move through a two-dimensional diffusion layer of lithium alone and have a higher diffusion coefficient than that of a spinel structure. From this feature, the layered structure type lithium cobalt composite oxide can be used as a positive electrode active material of a non-aqueous electrolyte battery, and is particularly suitable as a positive electrode active material of a non-aqueous electrolyte lithium secondary battery. Also,
M is preferably Al, Mo, W, or Ni. This is because when Al or Ni is used, the crystal structure is stabilized and the cycle life is improved, and when Mo or W is used, the thermal stability is improved. These may be used alone or in combination of two or more.

The lithium-manganese composite oxide can be prepared by a known method, for example, lithium carbonate, lithium nitrate, lithium oxide, lithium hydroxide, manganese carbonate, manganese nitrate or manganese nitrate. It can be obtained by pulverizing and mixing an oxide and a hydroxide of manganese at a predetermined ratio and firing at 600 to 1000 ° C. in an oxygen-containing atmosphere.

The lithium-cobalt composite oxide can be prepared by a known method, for example, lithium carbonate, lithium nitrate, lithium oxide, lithium hydroxide, cobalt carbonate, cobalt nitrate, or cobalt oxide. It can be obtained by pulverizing and mixing an oxide and a hydroxide of cobalt at a predetermined ratio and firing at 600 to 900 ° C. in an oxygen-containing atmosphere.

The positive electrode 3 is manufactured as follows, for example. A positive electrode active material is mixed with a conductive agent such as graphite or carbon black and a binder such as polyvinylidene fluoride to prepare a positive electrode mixture. Then, this positive electrode mixture is dispersed in a solvent such as N-methylpyrrolidone to obtain a slurry. This is applied to both surfaces of the positive electrode current collector 13, dried, and then compressed and smoothed by a roll press or the like to manufacture the positive electrode 3.

Here, the thickness of the positive electrode current collector 13 of the positive electrode 3 is T1, and the thicknesses of the positive electrode active material layers 15 and 16 are respectively
Let T2 and T3. In this embodiment, the total thickness T1 of the positive electrode current collector 13 and the thickness of the positive electrode active material layer (T2 + T3).
And 2.5 ≦ (T2 + T3) / T1, and (T2 + T
3) The relationship of ≦ 250 μm is satisfied.

The value of (T2 + T3) / T1 is 2.5 ≦
(T2 + T3) / T1 is required, and preferably
4.0 ≦ (T2 + T3) / T1, especially 5.0 ≦ (T2 +
It is preferably T3) / T1. (T2 + T3) /
This is because when the value of T1 is less than 2.5, the proportion of the positive electrode current collector 13 in the positive electrode 3 increases and the energy density decreases.

Further, it is necessary that (T2 + T3) ≦ 250 μm, preferably (T2 + T3) ≦ 200 μm,
It is particularly preferable that (T2 + T3) ≦ 150 μm. As described above, when the thickness is 250 μm or less, it is considered that the discharge capacity at the time of heavy load can be improved for the following reason.

In the non-aqueous electrolyte secondary battery, lithium ions move from the negative electrode 4 to the positive electrode 3 via the electrolyte during discharging. Then, the lithium that has moved to the positive electrode 3 is
It diffuses from the surface of the positive electrode 3 toward the inside.

In the lithium-cobalt composite oxide, the lithium ions reaching the surface of the positive electrode rapidly diffuse through the two-dimensional layer of lithium alone existing between the oxygen layers.

However, in the lithium-manganese composite oxide, the diffusion rate of lithium ions is slow. Therefore, if the active material layers 15 and 16 are thicker than 250 μm, lithium ions will come out of the positive electrode active material layers 15 and 16 on the surface of the positive electrode 3. It takes a very long time to reach the positive electrode active material layers 15 and 16 inside the positive electrode 3, that is, the positive electrode active material layers 15 and 16 near the positive electrode current collector 13.

As a result, the positive electrode active material layers 15 and 16 in the vicinity of the positive electrode current collector 13 cannot be effectively used, and the discharge capacity under heavy load is reduced.

Therefore, in this embodiment, (T2 + T3)
It is assumed that ≦ 250 μm, and the lithium ions rapidly move to the positive electrode active material layers 15 and 16 near the positive electrode current collector 13, and the positive electrode active material layers 15 and 1 near the positive electrode current collector 13.
By effectively using No. 6, the discharge capacity under heavy load is improved.

If (T2 + T3) ≦ 250 μm, the discharge capacity can be secured even at low temperature where the diffusion rate of lithium ions in the lithium manganese composite oxide is slower.

Thus, the thickness T1 of the positive electrode current collector 13
Total thickness of positive electrode active material layers 15 and 16 (T2 + T3)
2.5 ≦ (T2 + T3) / T1, and (T2 + T
3) It is necessary to satisfy the relationship of ≦ 250 μm.

The negative electrode 4 is made of, for example, copper, nickel, titanium,
It has a structure in which a negative electrode active material layer made of a negative electrode mixture containing a substance that absorbs and releases lithium ions is provided on both surfaces of a negative electrode current collector made of stainless steel. Note that the negative electrode active material layer may be provided not only on both surfaces but also on one surface.

The negative electrode 4 is manufactured, for example, as follows. The negative electrode active material is mixed with a binder such as polyvinylidene fluoride to prepare a negative electrode mixture. Then, this negative electrode mixture is dispersed in a solvent such as N-methylpyrrolidone to form a slurry. This is applied on both surfaces of the negative electrode current collector, dried, and then compressed and smoothed by a roll press or the like to manufacture the negative electrode 4.

The negative electrode active material is not particularly limited, and examples thereof include known cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbonaceous materials such as carbon fibers, and metals. Lithium, lithium alloy, polyacene, or tin oxide glass, lithium / titanium composite oxide, iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide, tin oxide, metal oxide such as tin oxide, etc. Alternatively, two or more kinds may be mixed and used, but it is particularly preferable to use a carbonaceous material because of its high safety.

The separator 5 is not particularly limited,
For example, a known woven fabric, non-woven fabric, synthetic resin microporous film, or the like can be used, and a synthetic resin microporous film can be preferably used. Among them, a polyolefin-based microporous film such as a polyethylene and polypropylene microporous film or a composite microporous film thereof is preferably used in terms of thickness, film strength, film resistance and the like.

Further, by using a solid electrolyte such as a polymer solid electrolyte, it can also serve as a separator.
In this case, the solid polymer electrolyte may further contain an electrolytic solution, for example, by using a porous solid polymer electrolyte membrane as the solid polymer electrolyte.

As the non-aqueous electrolyte of the present invention, either a non-aqueous electrolytic solution or a solid electrolyte can be used. When the non-aqueous electrolyte is used, it is not particularly limited, and for example, a mixed solvent of ethylene carbonate and ethyl methyl carbonate or a mixed solvent of ethylene carbonate and dimethyl carbonate is used. In the mixed solvent, propylene carbonate, butylene carbonate, vinylene carbonate, trifluoropropylene carbonate, γ-butyrolactone, 2-methyl-γ-butyl lactone, acetyl-γ-butyrolactone, γ-valerolactone, sulfolane, 1,2-dimethoxy. Ethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate , Dipropyl carbonate, methyl propyl carbonate, ethyl isopropyl carbonate, dibutyl carbonate, etc. may be used alone or in admixture of two or more.

The electrolyte salt as a solute of the non-aqueous electrolyte is not particularly limited, and may be, for example, LiClO ₄ , LiAsF ₆ , Li.
PF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiCF ₃ C
F ₂ SO ₃ , LiCF ₃ CF ₂ CF ₂ SO ₃ , LiN
_{(CF 3 SO 2) 2,} LiN (C 2 F 5 SO 2) 2 and the like may be used alone or as a mixture of two or more. Among them, LiPF ₆ is preferably used as the electrolyte salt.

As the solid electrolyte, a known solid electrolyte can be used, for example, an inorganic solid electrolyte or a polymer solid electrolyte can be used.

[0037]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. Examples 1 to 7 and Comparative Example 1
4 to 4, the rectangular non-aqueous electrolyte secondary battery 1 shown in FIG. 1 was produced. First, as a positive electrode active material, 1.0 mol of lithium carbonate and 4.0 mol of manganese dioxide were mixed, and the mixture was baked in air at a temperature of 800 ° C. for 15 hours. When X-ray diffraction measurement was performed on the product, it was in good agreement with the peak of LiMn ₂ O ₄ registered in the JCPDS file. Therefore, the product was confirmed to be LiMn ₂ O ₄ .

Next, 1.0 mol of lithium hydroxide and 1.0 mol of cobalt hydroxide were mixed, and the mixture was calcined in air at a temperature of 700 ° C. for 15 hours. When X-ray diffraction measurement was performed on the product, it was in good agreement with the peak of LiCoO ₂ registered in the JCPDS file. Therefore, the product was confirmed to be LiCoO ₂ .

50 parts by weight of the above LiMn ₂ O ₄ powder,
41 parts by weight of LiCoO ₂ powder, 3 parts by weight of acetylene black as a conductive agent, and 5 parts by weight of polyvinylidene fluoride as a binder were mixed, and N-methyl-2-pyrrolidone was appropriately added and dispersed. A slurry was prepared. As shown in Table 1, this slurry has a thickness (T1) of 10 to 100.
Evenly coated on both sides of the positive electrode current collector 13 made of aluminum of μm,
After drying, compression molding was performed by a roll press to prepare positive electrodes 3 having different values of (T2 + T3) / T1 (T2 and T3 are the thicknesses of the positive electrode active material layers 15 and 16) (see Table 1). In addition, in Examples 1 to 7 and Comparative Examples 1 to 4, only the positive electrode 3 is different, and the other constituent elements described later are the same.

The negative electrode mixture was prepared by mixing 90 parts by weight of scaly graphite and 10 parts by weight of polyvinylidene fluoride and adding N-methyl-2-pyrrolidone as appropriate to disperse the slurry. The slurry was uniformly applied to a copper negative electrode current collector having a thickness of 10 μm, dried, and compression-molded with a roll press to prepare a negative electrode 4.

For the separator 5, a microporous polyethylene film having a thickness of 25 μm was used.

A prismatic non-aqueous electrolyte secondary battery 1 having a width of 48 mm, a height of 90 mm and a thickness of 4.15 mm was produced using the above-mentioned components.

As the non-aqueous electrolyte, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 30:70, and LiPF ₆ was added to the solution in an amount of 1.2.
Mol / liter dissolved therein was used.

Next, as Examples 8 to 13 and Comparative Examples 5 to 6, the positive electrode active material Li was prepared in the same manner as in Examples 1 to 7 above.
A prismatic non-aqueous electrolyte secondary battery having different mixing ratios of Mn ₂ O ₄ and LiCoO ₂ (see Table 4) was produced. (T2 + T
3) / T1 = 4, and the components other than the mixing ratio of LiMn ₂ O ₄ and LiCoO ₂ were the same as in Examples 1 to 7 and Comparative Examples 1 to 4 above.

(Normal temperature low load battery capacity test) The prismatic nonaqueous electrolyte secondary batteries 1 of Examples 1 to 13 and Comparative Examples 1 to 6 described above were subjected to a maximum voltage of 4 at a constant current of 0.5 A under an environment of 23 ° C. .2V
After carrying out constant current constant voltage charging (initial charging) for 6 hours,
A room temperature low load battery capacity test was conducted in which constant current discharge was performed at a current of 0.5 A in a 23 ° C. environment to a final voltage of 2.75 V.
The capacity of this room temperature low load battery capacity test is represented by C1.

(Normal Temperature Heavy Load Battery Capacity Test) Two prismatic non-aqueous electrolyte secondary batteries 1 of Examples 1 to 7 and Comparative Examples 1 to 4 described above were used.
In a 3 ° C. environment, a constant current constant voltage of 0.5 A and a constant current constant voltage charge (initial charge) with a maximum voltage of 4.2 V were performed for 6 hours, and then 2
A room temperature heavy load battery capacity test was performed in which constant current discharge was performed at a current of 3 A in a 3 ° C. environment to a final voltage of 2.75 V. Here, when the discharge capacity in the room temperature heavy load battery capacity test is C2 and the capacity in the room temperature low load battery capacity test is C1, the heavy load characteristic is represented by C2 / C1.

(Low-temperature low-load battery capacity test) The rectangular non-aqueous electrolyte secondary batteries 1 of Examples 1 to 7 and Comparative Examples 1 to 4 described above were used.
After performing constant-current constant-voltage charging (initial charging) with a maximum voltage of 4.2 V at a constant current of 0.5 A in an environment of 3 ° C. for 6 hours,
After being left in an environment of ° C for 1 hour, a low temperature low load battery capacity test was conducted in which constant current discharge was performed at a current of 0.5 A to a final voltage of 2.75V. Here, when the discharge capacity of the low temperature low load battery capacity test is C3 and the capacity of the above room temperature low load battery capacity test is C1, the low temperature load characteristic is represented by C3 / C1.

(Safety Test) The above-mentioned Examples 1 and 8 to
13 and the rectangular non-aqueous electrolyte secondary batteries 1 of Comparative Examples 5 and 23
After performing constant-current constant-voltage charging (initial charging) with a maximum voltage of 4.2 V at a constant current of 0.5 A in an environment of ℃ for 6 hours, pierce the battery with a 3 mmφ iron nail to check for heat generation and smoke generation. Examined.

(Test Results) Table 1 to Table 5 and FIGS. 3 to 6 show the test results of the room temperature low load battery capacity test, the room temperature heavy load battery capacity test, the low temperature low load battery capacity test, and the safety test. .

[0050]

[Table 1]

First, the influence of the value of (T2 + T3) / T1 on the capacity C1 in the room temperature low load battery capacity test will be examined. In Table 1 and FIG. 3, 2.5 ≦ (T2 + T
3) / T1 in Examples 1 to 7, 2.5> (T2 + T
It was found that the discharge capacity C1 was large because the energy density was increased as compared with Comparative Examples 1 and 2 of 3) / T1. Further, since C1 of Example 5 is larger than C1 of Examples 6 and 7, it was found that 4.0 ≦ (T2 + T3) / T1 is preferable. Furthermore, C1 of Example 3
However, since it is larger than C1 of Example 5, especially 5.0
It has been found that it is preferable that ≦ (T2 + T3) / T1.

[0052]

[Table 2]

[0053]

[Table 3]

Next, the influence of the value of (T2 + T3) on the heavy load characteristic C2 / C1 and the low temperature load characteristic C3 / C1 will be examined. In Table 2 and FIG. 4, (T2 + T
3) C2 / C1 of Examples 1 to 7 in which ≦ 250 μm is:
(T2 + T3)> 250 μm C2 of Comparative Examples 3 to 4
It was found to be larger than / C1. Example 2
C2 / C1 in Example 2 was larger than C2 / C1 in Example 1, it was found that (T2 + T3) ≦ 200 μm was preferable. Furthermore, C2 / C of Examples 3 and 4
Since 1 is larger than C2 / C1 in Example 2, it was found that (T2 + T3) ≦ 150 μm is particularly preferable.

The low temperature load characteristic C shown in Table 3 and FIG.
For 3 / C1, (T2 + T3) ≦ 250 μm, C3 / C1 of Examples 1 to 7 is (T2 + T3)> 25.
It was found to be larger than C3 / C1 of Comparative Examples 3 to 4 which is 0 μm.

The above results were obtained because, when the active material layers 15 and 16 were thicker than 250 μm, lithium ions were transferred from the positive electrode active material layers 15 and 16 on the surface of the positive electrode 3 to the positive electrode active material layer inside the positive electrode 3. It takes a very long time to reach the positive electrode active material layers 15 and 16 in the vicinity of the positive electrode current collectors 15 and 16, that is, the positive electrode current collector 13. As a result, it is considered that the positive electrode active material layers 15 and 16 in the vicinity of the positive electrode current collector 13 could not be effectively used and the heavy load characteristics and the low temperature load characteristics were deteriorated.

From the above results, the thickness T1 of the positive electrode current collector is
And the total thickness (T2 + T3) of the positive electrode active material layer,
2.5 ≦ (T2 + T3) / T1, and (T2 + T3) ≦
By satisfying the relationship of 250 μm, a non-aqueous electrolyte secondary battery having high energy density, excellent heavy load characteristics, and excellent low temperature characteristics can be obtained.

[0058]

[Table 4]

[0059]

[Table 5]

Next, the influence of the mixing ratio of LiMn ₂ O ₄ and LiCoO ₂ as the positive electrode active material on the capacity C1 in the room temperature low load battery capacity test will be examined. Table 4 and FIG.
In Examples 8 and 9 in which the content of LiMn ₂ O ₄ is low
It was found that, as compared with Examples 12 and 13 in which the content of LiMn ₂ O ₄ was high, the discharge capacity C1 was large because the energy density was increased. On the other hand, in the safety test,
As shown in Table 5, in Comparative Example 5 containing no LiMn ₂ O ₄ , abnormal heat generation and smoking of the battery were observed.

From the above results, it is preferable to lower the content of LiMn ₂ O ₄ in order to increase the capacity of the battery, but in order to maintain high safety, L having high thermal stability is used.
It is preferable to add iMn ₂ O ₄ . To achieve a high level of energy density and safety, LiMn
It is preferable that the content of ₂ O ₄ is 40 to 90%.

In this example, a mixture of LiMn ₂ O ₄ and LiCoO ₂ (mass ratio 5
0:41), but if LiMn ₂ O ₄ has a spinel structure, Li _X Mn _{2 -Y} M _Y O ₄ (0.95
≦ x ≦ 1.25, 0.01 ≦ y ≦ 0.20, M is T
It is clear that the same effect can be obtained by using an active material represented by at least one kind of metal selected from i, Cr, Fe, Co, Ni, Zn and Al). LiC
The same applies to oO ₂ , and the general formula Li _x Co _{1- y My} O ₂ (0.9
5 ≤ x ≤ 1.25, 0.01 ≤ y ≤ 0.50, M is T
The same effect can be obtained by using an active material represented by at least one kind of metal selected from i, Cr, Fe, Co, Mn, Zn, Al, Mo, and W). Regarding the mixing ratio of the active material, Li _x Co is based on Li _x Mn _{2- y My} O ₄ .
_1-y M _y O ₂ is seen a similar effect if it contains a range of 10% to 90%, to achieve both the energy density and safety at a high _{level, Li x Mn 2-y M} y The O ₄ content is more preferably in the range of 40% to 80%.

<Other Embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings. For example, the following embodiments are also included in the technical scope of the present invention. In addition to the above, various modifications can be made without departing from the scope of the invention.

In the above-described embodiment, the prismatic non-aqueous electrolyte secondary battery 1 has been described, but the battery structure is not particularly limited, and a cylindrical, lithium polymer battery, and strip-shaped electrodes are laminated via a separator. Of course, a prismatic battery or the like may be used.

[0065]

According to the positive electrode for a non-aqueous electrolyte secondary battery and the non-aqueous electrolyte secondary battery using the same according to the present invention, high energy density, excellent heavy load characteristics, excellent low temperature characteristics, and high safety are provided. Can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a prismatic nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a positive electrode according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between the ratio (T2 + T3) / T1 of the thickness T1 of the positive electrode current collector of the present invention and the thickness (T2 + T3) of the active material layer, and the room temperature low load discharge capacity C1.

FIG. 4 is a characteristic diagram showing the relationship between the thickness (T2 + T3) of the positive electrode active material layer of the present invention and the ratio C2 / C1 of the room temperature low load discharge capacity C1 and the room temperature heavy load discharge capacity C2.

FIG. 5 is a characteristic diagram showing the relationship between the thickness (T2 + T3) of the positive electrode active material layer of the present invention and the ratio C3 / C1 of the room temperature low load discharge capacity C1 and the low temperature low load discharge capacity C3.

[Fig. 6] LiCo of positive electrode active material LiMn ₂ O ₄ of the present invention
Characteristic diagram showing the relationship between the content rate with respect to O ₂ and the room temperature low load discharge capacity C1

[Explanation of symbols]

3 ... Positive electrode 13 ... Positive electrode current collector 15 ... Positive electrode active material layer 16 ... Positive electrode active material layer

Continued front page    F term (reference) 5H029 AJ02 AJ03 AJ12 AK03 AL02                       AL06 AL07 AL12 AL18 AM03                       AM04 AM05 BJ02 BJ14 DJ07                       EJ04 EJ12 HJ02 HJ04                 5H050 AA02 AA06 AA08 AA15 BA16                       BA17 CA08 CA09 CB02 CB07                       CB08 CB12 DA04 EA10 EA24                       HA02 HA04

Claims (2)

[Claims] 1. Li on both sides of the positive electrode current collector_XMn_2-YM
_YO_Four(0.95 ≦ x ≦ 1.25, 0.01 ≦ y ≦ 0.
20, M is Ti, Cr, Fe, Co, Ni, Zn, A
at least one metal selected from the above) and Li_X
Co_1-YM _YO₂(0.95 ≤ x ≤ 1.25, 0.0
1 ≦ y ≦ 0.50, M is Ti, Cr, Fe, Ni, M
At least 1 selected from n, Zn, Al, Mo and W
Positive electrode having a positive electrode active material layer containing at least one metal)
At Thickness T1 of the positive electrode current collector and thickness of the positive electrode active material layer
(T2 + T3) is 2.5 ≦ (T2 + T3) /
Satisfies the relationship of T1 and (T2 + T3) ≦ 250 μm
A positive electrode for a non-aqueous electrolyte secondary battery, which is characterized in that: 2. A positive electrode current collector is provided with Li on both sides thereof._XMn_2-YM
_YO_Four(0.95 ≦ x ≦ 1.25, 0.01 ≦ y ≦ 0.
20, M is Ti, Cr, Fe, Co, Ni, Zn, A
at least one metal selected from the above) and Li_X
Co_1-YM _YO₂(0.95 ≤ x ≤ 1.25, 0.0
1 ≦ y ≦ 0.50, M is Ti, Cr, Fe, Ni, M
At least 1 selected from n, Zn, Al, Mo and W
Positive electrode having a positive electrode active material layer containing at least one metal)
When, A negative electrode having a negative electrode active material layer on a negative electrode current collector, and a non-aqueous electrolyte
In a non-aqueous electrolyte secondary battery comprising and, Thickness T1 of the positive electrode current collector and thickness of the positive electrode active material layer
The sum of (T2 + T3) is 2.5 ≦ (T2 + T3) / T
1 and (T2 + T3) ≦ 250 μm.
And a non-aqueous electrolyte secondary battery.