JP2000077072A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep high safety and high capacity even if lithium nickelate is used as a main positive active material by including a Li.Mn composite oxide in a positive electrode in a range not exceeding the weight of a Li.Ni composite oxide, and limiting the specific surface area of the Li.Ni composite oxide to a specified value or lower. SOLUTION: A specific surface area of a Li.Ni composite oxide is made 1.0 m2/g or less. As the Li.Ni composite oxide, LiNiO2 and an oxide doped with other element in its part are listed. The oxide doped with other element is represented by LiNi1-xMxO2 (0<x<=0.5), M is a doping metal element of at least one selected from Co, Mn, Al, Fe, Cu, and Sr. As the Li.Mn composite oxide, lithium manganate having spinel structure such as LiMn2O4 is preferable, and generally represented by LiyMn2O4. Wherein 1.02<=y<=1.25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a lithium secondary battery or a lithium ion secondary battery, and more particularly to a nonaqueous electrolyte secondary battery having a large battery capacity and excellent safety.

[0002]

2. Description of the Related Art In a non-aqueous electrolyte secondary battery using lithium metal or a lithium compound as a negative electrode, an electromotive force exceeding 4 V can be obtained by using lithium cobaltate, lithium nickelate, and spinel-type lithium manganate as a positive electrode active material. Research has been widely conducted. Among these, lithium cobalt oxide, which has excellent battery characteristics and is easy to synthesize, is currently in practical use as a positive electrode active material of a lithium ion secondary battery. However, since cobalt has a small recoverable reserve and is expensive, lithium nickelate is promising as a substitute substance.

Lithium nickelate has a layered rock salt structure (α-NaFeO ₂ structure) like lithium cobaltate, has a potential of about 4 V with respect to the lithium electrode, and has a capacity of 4.2 V or less based on lithium. About 200mAh
/ G and very high capacity for lithium cobalt oxide. However, in the layered rock salt structure, the desorption of lithium during charging leads to the adjoining oxygen phase with a large electronegativity. If the electrostatic repulsion between the oxygen layers exceeds the chemical bonding force, irreversible conversion to the CdCl ₂ structure occurs. A structural change occurs.

[0004] Furthermore, the chemical instability of Ni ⁴⁺ generated by charging is the reason that the structure of lithium nickel oxide during charging is unstable and the temperature at which oxygen desorption from the crystal lattice is started is low. I have. Solid State
Ionics, 69, No. 3/4, 265
(1994) shows that the oxygen desorption start temperature of lithium nickelate in a charged state is lower than that of lithium cobaltate.

Therefore, although a battery system using lithium nickel oxide alone as a positive electrode active material can be expected to have a high capacity, sufficient safety cannot be ensured due to thermal instability at the time of charging. is there.

On the other hand, spinel-type lithium manganate belongs to the space group Fd3m, and when viewed from the lamination pattern in the direction of the (111) crystal axis, unlike lithium cobaltate or lithium nickelate, there is no lithium-only phase. For this reason, even if all lithium is extracted, manganese ions become pillars and the oxygen layer does not directly adjoin. Therefore, it is possible to extract lithium ions while maintaining the basic cubic skeleton. The oxygen desorption initiation temperature during charging is also higher than that of lithium nickelate or lithium cobaltate having a layered rock salt structure, and thus spinel-type lithium manganate is a highly safe cathode material. However, there is a problem that the charge / discharge capacity is smaller than that of lithium cobaltate or lithium nickelate.

JP-A-10-112318 discloses an example in which lithium nickel oxide is mixed with spinel-type lithium manganate and used as a positive electrode. But,
In this method, spinel-type lithium manganate mainly functions as a positive electrode active material, and the high charge / discharge capacity characteristic which is an advantage of lithium nickelate is not utilized. Since the battery cycle is performed with only the capacity of the spinel type lithium manganate, the capacity is insufficient in comparison with a battery system using lithium cobalt oxide which is currently in practical use.

Further, Japanese Patent Application Laid-Open No. 7-235291 discloses that a lithium manganese composite oxide such as LiMn ₂ O _{4 is} used as a positive electrode active material and a Li _x Co such as LiCo _0.5 Ni _0.5 O _{2 is} used as a positive electrode active material.
_{It describes that 1-y} Ni _y O ₂ (0 <x <1, 0 ≦ y ≦ 1) is used as a mixture. However, Li _x Co _1-y Ni
amount capable of _y O ₂ is the maximum 50 mol% relative to the lithium manganese composite oxide is a main active material, high charge-discharge capacity characteristics, which is an advantage of the lithium nickelate is not fully exploited .

[0009]

As described above, while lithium nickelate is expected to be an alternative material to lithium cobaltate, when it is actually evaluated as a battery,
There are problems to be improved. However, the discharge capacity,
Since there are limited material systems that can be expected to satisfy the performance required of current high-performance secondary batteries, such as energy density, nickel that has maintained a high capacity and has improved safety to a practically usable level There is a need for a non-aqueous electrolyte secondary battery using a lithium-nickel composite oxide material such as lithium oxide.

The present invention provides a non-aqueous electrolyte secondary battery which is excellent in safety even when lithium nickel oxide is used as a main positive electrode active material and has a higher capacity than a conventional battery using lithium cobalt oxide. The purpose is to provide.

[0011]

The present invention relates to a secondary battery using a lithium-nickel composite oxide as a positive electrode active material, wherein the lithium-manganese composite oxide does not exceed the weight of the lithium-nickel composite oxide. The present invention relates to a nonaqueous electrolyte secondary battery which is contained in a positive electrode in a range.

When the lithium-nickel composite oxide is used alone, the oxidizing power rapidly increases as lithium is extracted from the crystal layer during charging, and the oxygen release reaction starts at a lower temperature than lithium cobalt oxide. Occurs. On the other hand, according to the present invention, lithium-manganese composite oxides having low crystal phase transition instability during charging due to the crystal structure, particularly spinel-type lithium manganate, are mixed to allow lithium nickelate and the like existing in the battery to be mixed. Is diluted, the oxygen release reaction does not proceed rapidly, and the oxidizing power does not increase rapidly. Therefore, the safety as a battery is improved.

At this time, the use of a lithium-nickel composite oxide having a specific surface area of 1.0 m ² / g or less further improves the safety.

A lithium-nickel composite oxide, for example, lithium nickelate, is about 1.10 times less than lithium cobaltate.
Since it has five times the discharge capacity, the addition of a lithium-manganese composite oxide having a slightly inferior discharge capacity has the effect of improving the capacity by 2 to 15% compared to lithium cobalt oxide.

By including the lithium-manganese composite oxide in addition to the lithium-nickel composite oxide in the positive electrode, the safety of the battery can be maintained while maintaining a high battery capacity as compared with the Co-based battery. Can be improved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The lithium-nickel composite oxide used in the present invention is an oxide composed of lithium, nickel and oxygen, and is composed of LiNiO ₂ , LiNi ₂ O ₄ , L
i ₂ Ni ₂ O _4, and stable and high capacity of these oxides, and the like can be exemplified those obtained by doping a portion other elements for improving safety. As an oxide doped with another element, for example, an oxide obtained by doping another element with respect to LiNiO ₂ is represented by LiNi _1-x M _x O ₂ (0 <x ≦ 0.5). M is a doped metal element, and Co,
Represents one or more metal elements selected from the group consisting of Mn, Al, Fe, Cu, and Sr. M may be two or more types of doped metal elements, and the sum of the composition ratios of the doped metal elements may be x.

Among them, lithium nickelate (LiN
iO ₂ ) and those doped with a metal element are preferred. In summary, LiNi ₁ -xM _x O ₂ (x is 0 ≦
It is a number that satisfies x ≦ 0.5. ), And M is preferably at least one element selected from the group consisting of Co, Mn, Al, Fe, and Sr. In particular, LiNi _1-x Co _x O ₂ (x is 0 <x ≦ 0.
This is a number that satisfies 4. Is preferred.

In the present invention, the lithium / nickel composite
Li / Ni ratio of the composite oxide (LiNi _1-xM_xO_TwoIn the case of
Li / [Ni + M] ratio is slightly different from the stoichiometric ratio
The lithium-nickel composite acid of the present invention may be shifted.
The compound includes such a case.

Specific surface area of lithium / nickel composite oxide
Is 1.0m^Two/ G or less, and
0.3m to improve safety^Two/ G or less is preferred
No. Even if the specific surface area is too small, the large current discharge characteristics are not sufficient.
0.1m ^Two/ G or more. here
The specific surface area is the surface area per unit weight of powder (m^Two/
g), which is measured by the gas adsorption method in the present invention.
It is.

The particle size of the lithium-nickel composite oxide is determined by considering the ease of preparing a slurry suitable for preparing a positive electrode, the uniformity of a battery reaction, and the prevention of deterioration of an electrolytic solution. And the weight average particle size is preferably 30 μm or less.

Further, it is preferable that there is no adsorbed water or structured water, or that heat dehydration treatment has been performed.

Such a lithium-nickel composite oxide can be produced as follows. First, as a lithium raw material, for example, a lithium compound such as lithium carbonate, lithium oxide, lithium nitrate, and lithium hydroxide can be used. Further, nickel hydroxide, nickel oxide, nickel nitrate, or the like can be used as a nickel (Ni) raw material.

It is preferable that both the lithium raw material and the nickel raw material are pulverized, if necessary, so as to have an appropriate particle size. In particular, in order to obtain a predetermined specific surface area, it is preferable to classify and use the particle size of the nickel raw material.

Thereafter, the Li / Ni ratio is adjusted to the desired composition ratio of the lithium-nickel composite oxide, mixed well, and then fired in the same manner as in the production of the lithium-manganese composite oxide. The firing temperature is about 500 to 900 ° C. The lithium-nickel composite oxide obtained by firing is preferably further classified to obtain a lithium-nickel composite oxide having a desired specific surface area.

On the other hand, the lithium-manganese composite oxide used in the present invention is an oxide composed of lithium, manganese and oxygen, such as lithium manganate having a spinel structure such as LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ , and LiMnO _{2. 2} and Li ₂ MnO ₃ . Among them, L
lithium manganate are preferable spinel structure such as IMN ₂ O _4, as long as taking a spinel structure [Li] / [Mn] ratio may be shifted from 0.5, when expressed as Li _y Mn ₂ O ₄ , Y is 1.0 to 1.3, preferably 1.02
１．２1.25.

Similarly, as long as lithium manganate has a spinel structure, the ratio of [Li + Mn] / [O] is 0.1.
It may be shifted from 75.

The particle size of the lithium-manganese composite oxide is determined by considering the ease of preparing a slurry suitable for preparing the positive electrode, the uniformity of the battery reaction, and the prevention of deterioration of the electrolyte. The diameter is preferably 30 μm or less, and usually 5 μm or more.

Further, it is preferable that there is no adsorbed water or structured water, or that a heat dehydration treatment is performed.

Such a lithium-manganese composite oxide can be produced as follows.

Manganese (Mn) raw material and lithium (L
i) As a raw material, first, as a Li raw material, for example, a lithium compound such as lithium carbonate, lithium oxide, lithium nitrate, and lithium hydroxide can be used. As a Mn raw material, for example, electrolytic manganese dioxide (EMD), Mn ₂ O ₃ , M
Various Mn such as n ₃ O ₄ and chemical manganese dioxide (CMD)
Manganese compounds such as oxides and manganese salts such as manganese carbonate and manganese oxalate can be used. But L
Easy to secure the composition ratio of i and Mn, energy density per unit volume due to difference in bulk density, easy to secure target particle size, easy to process and handle in industrial mass synthesis, In consideration of the occurrence, cost, etc., a combination of electrolytic manganese dioxide and lithium carbonate is preferable.

As a step before mixing the starting materials, it is preferable that the lithium material and the manganese material are pulverized, if necessary, so as to have an appropriate particle size. The particle size of the Mn raw material is
Usually, it is 3 to 70 μm, preferably 5 to 30 μm. The particle size of the Li source is usually 10 μm or less, preferably 5 μm or less.
μm or less, most preferably 3 μm or less.

Since the reaction of forming the lithium-manganese composite oxide proceeds on the surface of the solid phase, if the mixing of the Li source and the Mn source is insufficient or the particle size is too coarse, the desired composition and In some cases, a lithium-manganese composite oxide having a structure cannot be obtained. For example, when producing lithium manganate having a spinel structure, if the mixing of the Li source and the Mn source is insufficient or the particle size is too coarse,
₂ O ₃ , Mn ₃ O ₄ , Li ₂ MnO ₃ , Li ₂ Mn ₄ O ₉ , Li ₄
A phase such as Mn ₅ O ₁₂ may be generated, and the battery voltage or the energy density may be lower than that of lithium manganate having a spinel structure. Therefore, in order to obtain a lithium-manganese composite oxide having a desired composition and structure, it is necessary to use the above particle size in order to increase the contact area between the lithium raw material and the manganese raw material in order to increase the uniformity of the reaction. Is preferred. Therefore, particle size control and granulation of the mixed powder may be performed. Further, by controlling the particle size of the raw material, a lithium-manganese composite oxide having a target particle size can be easily obtained.

Next, the respective raw materials are taken so that the molar ratio of Li / Mn matches the target composition ratio of the lithium-manganese composite oxide, mixed sufficiently, and fired in an oxygen atmosphere. Oxygen may be pure oxygen, or may be a mixed gas with an inert gas such as nitrogen or argon. The oxygen partial pressure at this time is about 50 to 760 torr.

The firing temperature is usually from 400 to 1000 ° C., but is appropriately selected so as to obtain a desired phase. For example, if the calcination temperature is too high to produce lithium manganate having a spinel structure, undesired phases such as Mn ₂ O ₃ and Li ₂ MnO ₃ are generated and mixed, and the battery voltage and energy density are not sufficient. If the firing temperature is too low, oxygen may become relatively excessive or the powder density may be low, which is also not preferable for realizing high capacity. Therefore, in order to produce lithium manganate having a spinel structure, the calcination temperature is preferably 600 to
900 ° C., most preferably 700-850 ° C.

The firing time can be appropriately adjusted, but is usually 6 to 100 hours, preferably 12 to 48 hours. Although the cooling rate can be adjusted as appropriate, it is preferable not to rapidly cool during the final baking treatment, and it is preferable to set the cooling rate to, for example, about 100 ° C./h or less.

The powder of the lithium-manganese composite oxide thus obtained is further classified, if necessary, and the particle size is adjusted. The powder is mixed with the lithium-nickel composite oxide and used as a positive electrode active material. .

As the positive electrode used in the nonaqueous electrolyte secondary battery of the present invention, a mixture of lithium / nickel composite oxide and lithium / manganese composite oxide is used as a positive electrode active material.

The method for producing the positive electrode is not particularly limited. For example, for example, a powder of lithium-manganese composite oxide and a powder of lithium-nickel composite oxide are mixed with a binder together with, for example, a conductivity-imparting agent and a binder. After mixing (slurry method) with a suitable dispersing medium that can be dissolved, the mixture is applied on a current collector such as an aluminum foil or a copper foil, and then the solvent is dried and then compressed by a press or the like to form a film.

There are no particular restrictions on the conductivity-imparting agent, and those commonly used such as carbon black, acetylene black, natural graphite, artificial graphite, and carbon fiber can be used. As the binder, a commonly used binder such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) can be used.

On the other hand, as the negative electrode active material, a carbon material such as lithium, lithium alloy, graphite or amorphous carbon capable of inserting and extracting lithium is used.

The separator is not particularly limited.
Glass fibers, porous synthetic resin films and the like can be used. For example, a polypropylene or polyethylene porous film is suitable in terms of a thin film, large area, film strength and film resistance.

As the solvent for the non-aqueous electrolyte, those which are commonly used may be used, and examples thereof include carbonates, chlorinated hydrocarbons, ethers, ketones, and nitriles. Preferably, ethylene carbonate (EC), propylene carbonate (P
C), at least one of γ-butyrolactone (GBL) and the like, and diethyl carbonate (DE) as a low-viscosity solvent.
C), at least one selected from dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), esters and the like, and a mixture thereof is used. EC + DEC, P
C + DMC or PC + EMC is preferred.

As the supporting salt, LiClO ₄ , LiI, L
iPF ₆ , LiAlCl ₄ , LiBF ₄ , CF ₃ SO ₃ Li
For example, at least one type is used. In the present invention, the use of a supporting salt which easily generates an acid can suppress the acid in the electrolytic solution, and is particularly preferable when LiPF ₆ or LiBF ₄ is used, since the most effective effect can be obtained. The concentration of the supporting salt is, for example, 0.8 to 1.5M.

The structure of the battery is a square, paper type,
Various shapes such as a laminated type, a cylindrical type, and a coin type can be adopted. In addition, components include a current collector, an insulating plate, and the like, but these are not particularly limited, and may be selected according to the above shape.

[0045]

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto. The specific surface area was measured by Quanta Chrome's Quant.
Measured using aSorb.

[Evaluation Test Example 1] Nickel nitrate was used as a nickel source, lithium hydroxide was used as a lithium source, a Co compound (cobalt carbonate) was added as an additive element, and the mixture was fired at 750 ° C. in an oxygen flow atmosphere. did. The composition after firing was LiNi _0.8 Co _0.2 O ₂ . The specific surface area was 0.27 m ² / g.

For the synthesis of spinel-type lithium manganate, lithium carbonate (Li ₂ CO ₃ ) and electrolytic manganese dioxide (EMD) were used as starting materials, and the molar ratio [L
i] / [Mn] = 1.05 / 2.
This mixed powder was fired at 800 ° C. in an atmosphere of oxygen flow.

Using the thus synthesized lithium nickelate and lithium manganate as a positive electrode active material, a prototype 18650 cell was produced as follows.

First, lithium nickel oxide, lithium manganate, and carbon black as a conductivity-imparting agent were dry-mixed, and N-
The slurry was uniformly dispersed in methyl-2-pyrrolidone (NMP) to prepare a slurry. The slurry was applied on an aluminum metal foil having a thickness of 25 μm, and NMP was evaporated to obtain a positive electrode sheet.

The solid content ratio in the positive electrode is lithium nickelate: lithium manganate: conductivity imparting agent: PVD by weight ratio.
When F = 80−α: α: 10: 10, α =
The evaluation was made as 1, 10, 30, 40, and 50. In this case, a (= α · 100/80) is a =
1.25, 12.5, 37.5, 50, 62.5.

On the other hand, the negative electrode sheet is made of carbon: PVDF =
NMP was mixed so as to have a ratio of 90:10 (% by weight).
And applied to a copper foil having a thickness of 20 μm. The electrolytic solution uses 1M LiPF6 as a supporting salt, and propylene carbonate (PC) and diethyl carbonate (DE
C) A mixed solvent (50:50 (vol%)) was used. As the separator, a polyethylene porous film having a thickness of 25 μm was used.

As a comparative example, lithium cobalt oxide (LiCoO ₂ ) was used as the positive electrode active material, the spinel type lithium manganate was not included in the positive electrode, and the solid content ratio was LiCoO _2.
An 18650 cylindrical cell was produced in the same manner except that O2: conductivity imparting agent: PVDF = 80: 10: 10 (% by weight).

Using the cylindrical cell thus manufactured, 2
A charge / discharge cycle test at 5 ° C. was performed. Charging is 50
Discharge to 3.0V at 1000mA to 4.2V at 0mA
I went up. FIG. 1 shows a comparison of the cycle characteristics of the discharge capacity at 25 ° C. of the manufactured cylindrical cell. As compared with the cylindrical cell of Comparative Example 1 using lithium cobaltate, 1.25 ≦ a ≦
It can be seen that the discharge capacity is large in the range of 50.

[Evaluation Test Example 2] An 18650 cylindrical cell was prototyped in the same manner as in Evaluation Test Example 1, and its safety was evaluated.
At this time, the solid content ratio in the positive electrode was lithium nickelate: lithium manganate: conductivity imparting agent: PVDF in weight ratio.
= 80-α: α: 10: 10, so that α was a value shown in Table 1.

As a comparative example, the same procedure was repeated except that the positive electrode contained no spinel-type lithium manganate (α = a = 0).
A 650 cylindrical cell was prototyped.

Table 1 shows the results of a safety test performed using these cylindrical cells. The safety evaluation items were an overcharge test and a short-circuit test. The overcharge test was performed under the conditions of 12 V and 3 C, and the short circuit test was performed by forcibly short-circuiting at 4.2 V full charge and room temperature. For details of other test conditions, see UL-164.
According to 2.

In the overcharge test, a small amount of steam was observed when α was 20 or less, and ignition occurred at 13 or less. On the other hand, in the short circuit test, α
However, slight steam was observed at 17 or less, and ignition occurred at 9 or less.
As the proportion of lithium nickelate increases, it becomes more difficult to ensure safety. Therefore, to obtain the effect of improving safety by mixing spinel-type lithium manganate, α
Is larger than 13, that is, if (lithium nickelate) :( lithium manganate) = 100-a: a (% by weight), 16.25 <a is preferable. It is more desirable that 21.25 <a when including the results of the overcharge test.

[0058]

[Table 1]

[0059]

According to the present invention, a non-aqueous electrolyte having excellent safety even when lithium nickel oxide is used as a main positive electrode active material and having a higher capacity than a battery using conventional lithium cobalt oxide is provided. A secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing cycle characteristics of a cylindrical cell in an evaluation test example 1.

[Procedure amendment]

[Submission Date] June 28, 1999 (1999.6.2
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010] The present invention is excellent in still safety with lithium nickel oxide as the main positive electrode active material, and non <br/> water electrolysis solution Ru higher capacity der than batteries using conventional lithium cobaltate It is intended to provide a secondary battery.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

[0011]

The present invention relates to a secondary battery using a lithium-nickel composite oxide as a positive electrode active material, wherein the lithium-manganese composite oxide does not exceed the weight of the lithium-nickel composite oxide. The lithium-nickel composite oxide contained in the positive electrode in the range
Has a specific surface area of 1.0 m ² / g or less .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction contents]

[0059]

According to the present invention is excellent in still safety with lithium nickel oxide as the main positive electrode active material, and nonaqueous electrolyte Ru higher capacity der than batteries using conventional lithium cobaltate A secondary battery can be provided.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Chinatsu Kanbe 5-7-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Inventor Masato Shikata 5-7-1 Shiba, Minato-ku, Tokyo No. NEC Corporation F term (reference) 5H003 AA02 AA10 BB05 BC06 BD03 BD04 BD05 5H014 AA02 EE10 HH01 HH06 5H029 AJ03 AJ12 AK03 AL06 AL07 AL12 AM01 AM02 AM03 AM04 AM05 AM07 BJ02 BJ03 BJ04 H17

Claims (6)

[Claims] 1. A secondary battery using a lithium-nickel composite oxide as a positive electrode active material, wherein the lithium-manganese composite oxide is contained in the positive electrode within a range not exceeding the weight of the lithium-nickel composite oxide. Non-aqueous electrolyte secondary battery characterized by the following. 2. The weight ratio of the lithium-nickel composite oxide to the lithium-manganese composite oxide is expressed as [LiNi composite oxide]: [LiMn composite oxide] = 100-a: a
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein a satisfies 16.25 <a ≦ 50. 3. The non-aqueous electrolyte secondary battery according to claim 2, wherein said a further satisfies 21.25 <a. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the specific surface area of the lithium-nickel composite oxide is 1.0 m ² / g or less. 5. The lithium-nickel composite oxide,
LiNi _1-x M _x O ₂ (M represents at least one element selected from the group consisting of Co, Mn, Al, Fe, and Sr, and x is a number satisfying 0 ≦ x ≦ 0.5 The non-aqueous electrolyte secondary battery according to claim 1, which is a compound represented by the following formula: 6. The lithium-manganese composite oxide,
Nonaqueous according to any one of Li _y Mn ₂ O ₄ according to claim 1 to 5 (y is a number satisfying 1.02 ≦ y ≦ 1.25.) Is a spinel-type lithium manganate represented by Electrolyte secondary battery.