JPH0845498A - Nonaqueous electrolytic liquid secondary battery - Google Patents

Abstract

PURPOSE:To provide a nonaqueous electrolytic liquid secondary battery having a high energy density and an excellent cycle life. CONSTITUTION:A nonaqueous electrolytic liquid second battery is provided with a positive pole 2 using a lithium compound as a positive pole active material, a negative pole 1 using cabonic material capable of doping and deposing lithium as a negative pole active material and nonaqueous electrolytic liquid. A lithium and mangan synthetic oxide represented by LixMn2O4 (x is x>=0.95) and a lithium, nickel and cobalt synthetic oxide represented by LiNiyCo1-yO2 (y is 0.3<=y<=1.0) are used as a positive pole active material. Preferably, a mixture rate of the lithium and mangan synthetic oxide in the mixture is 20 to 80wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery having a positive electrode containing a lithium compound as a positive electrode active material, and more particularly to improving cycle characteristics.

[0002]

2. Description of the Related Art In recent years, due to advances in electronic technology, higher performance, smaller size, and more portable electronic devices have been developed, and batteries used in these electronic devices are required to have ever higher energy densities. Has become.

Conventionally, an aqueous solution type secondary battery such as a lead battery or a nickel-cadmium battery has been mainly used as a secondary battery used in these electronic devices. However, these aqueous solution type secondary batteries have a discharge potential of It is low and it is hard to say that the energy density is sufficiently satisfactory.

On the other hand, recently, a lithium secondary battery using metallic lithium or a lithium alloy as a negative electrode and a lithium compound as a positive electrode has attracted attention as a battery system satisfying the above-mentioned requirements, and research and development have been carried out. Is being actively conducted.

However, this lithium secondary battery has come to be recognized as having problems in terms of cycle life, safety, quick charging performance, etc., which is a major obstacle to practical use. It is considered that this is due to the dissolution of metallic lithium, which is the negative electrode, and the generation and miniaturization of dendrites during precipitation. Therefore, the lithium secondary battery is only partially put into practical use as a coin type.

Therefore, in order to solve these problems,
A lithium ion secondary battery (non-aqueous electrolyte secondary battery) using a carbonaceous material such as coke as a negative electrode active material has been proposed.

In this lithium ion secondary battery, since lithium does not exist in a metallic state, there is no problem of deterioration of cycle characteristics and safety due to the metallic lithium negative electrode, and further, a lithium compound having a high redox potential is used for the positive electrode. By using it, the voltage of the battery can be increased and a high energy density can be obtained.

Further, this lithium-ion secondary battery has less self-discharge than the nickel-cadmium battery,
It is a very good secondary battery. For this reason,
This lithium ion secondary battery is, for example, an 8 mm video tape recorder (VTR), compact disc (CD).
It has already been commercialized as a power source for portable electronic devices such as players, laptop computers, and cellular telephones, and there are great expectations in the future.

[0009]

In the above lithium ion secondary battery (non-aqueous electrolyte secondary battery), the positive electrode active material is a lithium-cobalt composite oxide or lithium nickel having a high redox potential. Composite oxides, lithium-manganese composite oxides, etc. are known.
Above all, from the viewpoint of raw material price and raw material supply stability,
A lithium-manganese composite oxide is promising, and a non-aqueous electrolyte secondary battery combining this lithium-manganese composite oxide as a positive electrode active material and a carbonaceous material that can be doped or dedoped with lithium as a negative electrode active material has been developed. Proposed by various research institutes.

However, this non-aqueous electrolyte secondary battery has two drawbacks due to the positive electrode. That is, first, the deterioration of the cycle characteristics is large, and the battery capacity is small.

On the other hand, for example, J. M. Tara
According to Scon et al., when LiMn ₂ O ₄ is used as a lithium-manganese composite oxide in the positive electrode active material, cycle deterioration is large and Ti, Ge, Ni, Z as different metals
It has been reported that the cycle characteristics can be improved by adding n and Fe [J. Electrochem. Soc., vol13.
8, No. 10, p2859 (1991)].

However, although the method of adding different metals as described above can suppress cycle deterioration,
On the contrary, the battery capacity becomes small, and good results cannot be obtained.

On the other hand, as a technique for improving the battery capacity,
As disclosed in JP-A-4-147573,
Li _{1 + x} Mn ₂ O ₄ (x> where lithium-manganese composite oxide is electrochemically and chemically doped with lithium in advance
A method using 0) as a positive electrode active material is known.

However, in this method, the cycle deterioration is not so different from the conventional one, and an urgent solution is desired.

Therefore, in the non-aqueous electrolyte secondary battery using a lithium-manganese composite oxide as a positive electrode active material, the fact is that the technology for satisfying both battery capacity and cycle characteristics has not yet been established.

Therefore, the present invention has been proposed in view of such circumstances, and an object thereof is to provide a non-aqueous electrolyte secondary battery having a high energy density and an excellent cycle life.

[0017]

Means for Solving the Problems The inventors of the present invention have earnestly studied that they cannot achieve the above-mentioned object, and as a result, the lithium-manganese composite oxide, which is a positive electrode active material, has a lithium-nickel-based material as a second active material. By mixing the composite oxide,
The inventors have found that it is possible to reduce the volume change of the positive electrode active material due to charge and discharge and improve the cycle characteristics, and have completed the present invention.

That is, the present invention comprises a positive electrode using a lithium compound as a positive electrode active material, a negative electrode using a carbonaceous material capable of doping and dedoping lithium as a negative electrode active material, and a non-aqueous electrolyte. The non-aqueous electrolyte secondary battery is characterized in that the positive electrode active material comprises a mixture of a lithium-manganese composite oxide and a lithium-nickel composite oxide.

In the non-aqueous electrolyte secondary battery of the present invention, a mixture of lithium / manganese composite oxide and lithium / nickel composite oxide is used as the positive electrode active material.

As the lithium-manganese composite oxide, one represented by Li _x Mn ₂ O ₄ (where x is x ≧ 0.95) is preferable.

As the lithium-nickel composite oxide, LiNi _y Co _1-y O ₂ (where y is 0.3 ≦ y
≦ 1.0) is preferable.

Thus, Li _x Mn ₂ O ₄ (however, x
Is x ≧ 0.95) and a lithium-manganese composite oxide represented by the formula: LiNi _y Co
By mixing a lithium-nickel-based composite oxide represented by _1-y O ₂ (where y is 0.3 ≦ y ≦ 1.0), Li _x Mn ₂ O ₄ is used as a positive electrode active material. It is possible to reduce the volume change due to contraction and expansion of the positive electrode active material due to charging and discharging, which is considered to be the cause of the deterioration of the cycle characteristics of the non-aqueous electrolyte secondary battery, and to suppress the stress applied to the positive electrode active material itself. it can. As a result, the cycle characteristics can be improved while sufficiently securing the large battery capacity of the non-aqueous electrolyte secondary battery using Li _x Mn ₂ O ₄ as the positive electrode active material.

In such a mixture of the lithium-manganese composite oxide and the lithium-nickel composite oxide, the mixture ratio of the lithium-manganese composite oxide in the mixture is 2
It is preferably from 0 to 80% by weight. Lithium
When the mixing ratio of the manganese composite oxide exceeds the above range, it is not possible to sufficiently suppress the volume change due to the contraction and expansion of the positive electrode active material due to charge and discharge, and conversely, when it is less than the above range, The effect of the lithium-nickel composite oxide is too great, and the cycle deterioration due to the volume change becomes remarkable.

On the other hand, a carbon material is used as the negative electrode active material used for the negative electrode, and any carbon material may be used so long as it can be doped or dedoped with lithium, such as pyrolytic carbons, cokes ( Pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, organic polymer compound fired bodies (carbonized by firing furan resin at an appropriate temperature), carbon fibers, activated carbon, etc. It can be used.

As the carbon material which becomes the negative electrode active material,
A carbon material having a (002) plane spacing of 3.70 angstroms or more and a true density of less than 1.70 g / cc and having no exothermic peak in a temperature range of 700 ° C. or more by differential thermal analysis in an air stream is preferable. .

As the electrolytic solution, a solution in which a lithium salt is used as an electrolyte and this is dissolved in an organic solvent is used.

The organic solvent is not particularly limited, but for example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate. It is possible to use either a single solvent such as dipropyl carbonate or a mixed solvent of two or more kinds.

Examples of the electrolyte include LiCl
O ₄ , LiAsF ₆ , LiPF ₆ , LiBF _4, etc. can be used.

Further, in the non-aqueous electrolyte secondary battery of the present invention, in order to obtain a safer sealed non-aqueous electrolyte secondary battery, in order to obtain a more safe sealed non-aqueous electrolyte secondary battery, the current depending on the increase in the battery internal pressure at the time of an abnormality during overcharge It is desirable to provide a shutoff.

[0030]

The cycle characteristics are improved by using a mixture of lithium-manganese composite oxide and lithium-nickel composite oxide as the positive electrode active material.

The reason for this is considered as follows.

That is, in a non-aqueous electrolyte secondary battery comprising a positive electrode using a lithium compound as a positive electrode active material, a negative electrode using a carbonaceous material capable of doping and dedoping lithium as a negative electrode active material, and a non-aqueous electrolyte solution. In the charging reaction, lithium is dedoped from the positive electrode. At that time, the crystal structure lattice of the lithium-manganese composite oxide contracts, but the crystal structure lattice of the lithium-nickel composite oxide expands. Further, in the discharge reaction, the positive electrode is doped with lithium. At that time, the crystal structure lattice of the lithium-manganese composite oxide expands, but the crystal structure lattice of the lithium-nickel composite oxide contracts.

Therefore, when viewed as the whole positive electrode active material, the volume change due to contraction and expansion due to charge and discharge becomes small. Therefore, even if charging and discharging are repeated for a long time, the positive electrode active material is hardly subjected to stress due to volume change, and as a result, contact with the conductive agent is hardly damaged.

[0034]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

First, a method for preparing the positive electrode active material (lithium-manganese composite oxide, lithium-nickel composite oxide) used in this example is shown below.

<Preparation Method 1 of Lithium-Manganese Composite Oxide (Thermochemical Method)> A mixture of 1 mol of manganese dioxide and 0.25 mol of lithium carbonate was heated to 850 in air.
Li _x Mn ₂ O ₄ was obtained by firing at 5 ° C. for 5 hours. The Li composition ratio x of this Li _x Mn ₂ O ₄ was measured by an atomic absorption method and found to be x = 0.95.

<Preparation Method 2 of Lithium-Manganese Composite Oxide (Electrochemical Method)> Li _0.95 M obtained in Preparation Method 1
86% by weight of n ₂ O ₄ and 1 graphite as a conductive agent
0% by weight and 4% by weight of polyvinylidene fluoride were mixed to prepare a positive electrode mixture, which was dispersed in N-methyl-2pyrrolidone to prepare a positive electrode mixture slurry.

This positive electrode mixture slurry was uniformly applied to both sides of a strip-shaped aluminum foil, dried, and compression-molded with a roller press to obtain a positive electrode.

On the other hand, strip-shaped metallic lithium was prepared as the negative electrode.

The strip-shaped negative electrode, the positive electrode and the strip-shaped separator were successively laminated and wound many times to produce a spiral electrode body.

Then, the spirally wound electrode body was incorporated into a battery can to prepare a cylindrical battery having a diameter of 18 mm and a height of 65 mm.

Next, the battery thus produced was discharged at 0.2 mA / cm ² to 2.0 V to dope the positive electrode with lithium. Li _x after lithium doping
When the Li composition ratio x of Mn ₂ O ₄ was measured by an atomic absorption method, it was x = 1.85.

<Preparation Method 3 of Lithium-Manganese Composite Oxide (Chemical Method)> Li _0.95 Mn ₂ obtained in Preparation Method 1
100 g of O ₄ was reacted in 400 ml of a hexane solution containing 15% of n-butyllithium for several hours, and this solution was filtered. Then, the residue obtained by filtration was vacuum dried at a temperature of 120 ° C. for 24 hours. L obtained
The Li composition ratio x of i _x Mn ₂ O ₄ was measured by an atomic absorption method and found to be x = 2.05.

<Preparation Method 1 of Lithium-Nickel Composite Oxide> Cobalt oxide, nickel oxide and lithium hydroxide were mixed so that Li / Ni / Co = 1 / 0.8 / 0.2, and the mixture was mixed in oxygen. LiN by firing at 750 ° C for 5 hours
i _0.8 Co _0.2 O ₂ was obtained.

<Preparation Method 2 of Lithium / Nickel Composite Oxide> Cobalt oxide, nickel oxide and lithium hydroxide were mixed so that Li / Ni / Co = 1 / 0.3 / 0.7 and the mixture was mixed in oxygen. LiN by firing at 750 ° C for 5 hours
i _0.3 Co _0.7 O ₂ was obtained.

<Preparation Method 3 of Lithium-Nickel Composite Oxide> Nickel oxide and lithium hydroxide are mixed with Li / Ni =
Mix so that it becomes 1/1, and mix in oxygen at a temperature of 750 ° C for 5
It was calcined for an hour to obtain LiNiO ₂ .

In the following Examples, Comparative Examples and Experimental Examples, batteries were prepared using these positive electrode active materials and the cycle characteristics were examined.

Example 1 First, the structure of the non-aqueous electrolyte secondary battery produced in this example will be described.

In this non-aqueous electrolyte secondary battery, as shown in FIG. 1, a negative electrode 1 formed by coating a negative electrode current collector 10 with a negative electrode active material and a positive electrode current collector 11 coated with a positive electrode active material. The positive electrode 2 formed as described above is wound around a separator 3, and the insulating plate 4 is placed on the upper and lower sides of the wound body and housed in a battery can 5.

A battery lid 7 is attached to the battery can 5 by caulking with a sealing gasket 6, and the negative electrode 1 is provided with a negative electrode lead 12 and a positive electrode lead 13, respectively.
Alternatively, it is electrically connected to the positive electrode 2 and is configured to function as a negative electrode or a positive electrode of a battery.

In the non-aqueous electrolyte secondary battery of this embodiment, the positive electrode lead 13 is attached to the safety valve device 8 by welding, and electrical connection with the battery lid 7 is achieved through the safety valve device 8. Has been.

In the non-aqueous electrolyte secondary battery having such a structure, when the pressure inside the battery rises, the safety valve device 8 is pushed up and deformed. Then, the positive electrode lead 13 is cut, leaving the portion welded to the safety valve device 8, and the current is cut off.

In this example, the non-aqueous electrolyte secondary battery having the above structure was prepared as follows.

First, the negative electrode 1 was manufactured as follows.

As the negative electrode active material, petroleum pitch was used as a starting material, 10 to 20% of oxygen-containing functional groups were introduced (oxygen cross-linking), and the mixture was calcined at a temperature of 1000 ° C. in an inert gas. A non-graphitizable carbon material having properties close to those of the glassy carbon material was used.

90% by weight of the above carbon material and 10% by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture, which was dispersed in N-methyl-2pyrrolidone. It was a mixture slurry.

Then, this negative electrode mixture slurry was uniformly applied on both sides of a 10 μm-thick copper foil as a negative electrode current collector, dried and then compression-molded with a roller press machine to prepare a strip-shaped negative electrode.

Next, the positive electrode 2 was manufactured as follows.

80% by weight of the lithium-manganese composite oxide Li _1.85 Mn ₂ O ₄ obtained by the above-mentioned preparation method 2,
A mixture of 20% by weight of lithium-nickel composite oxide LiNi _0.8 Co _0.2 obtained in Preparation Method 1 was used as a positive electrode active material, and 91% by weight thereof was used, 6% by weight of graphite was used as a conductive agent, and 3% of polyvinylidene fluoride. A positive electrode mixture was prepared by mixing the components in a weight percentage and dispersed in N-methyl-2pyrrolidone to prepare a positive electrode mixture slurry.

The positive electrode mixture slurry having a thickness of 2
A strip-shaped positive electrode was prepared by uniformly coating both surfaces of an aluminum foil, which is a positive electrode current collector having a thickness of 0 μm, and drying and then compression molding with a roller press.

Subsequently, the strip-shaped negative electrode, the positive electrode, and the separator made of the microporous polypropylene film having a thickness of 25 μm, which were manufactured as described above, were successively laminated and wound in large numbers to manufacture a spiral electrode body.

This spiral electrode body was housed in a nickel-plated iron battery can, and insulating plates were arranged on the upper and lower surfaces of the spiral electrode body. Then, in order to collect the current of the positive electrode and the negative electrode, the aluminum lead is led out from the positive electrode current collector to the safety valve device having the current interruption device and the PTC element, and the nickel lead is led out from the negative electrode current collector to the battery can. Welded to each.

Next, in the above battery can, 50% by volume of propylene carbonate and 50% by volume of diethyl carbonate were added.
An electrolyte solution in which 1 mol of LiPF ₆ was dissolved in the mixed solvent of was injected.

Then, the battery lid is fixed to the battery can by caulking with a gasket coated with asphalt,
A cylindrical battery having a diameter of 18 mm and a height of 65 mm was produced.

Example 2 As the positive electrode active material, Li _1.85 Mn ₂ O ₄ and LiNi _0.8
A cylindrical battery was produced in the same manner as in Example 1 except that a mixture of Co _0.2 O ₂ and 60 wt% and 40 wt% respectively was used.

Example 3 As the positive electrode active material, Li _1.85 Mn ₂ O ₄ and LiNi _0.8
A cylindrical battery was produced in the same manner as in Example 1 except that a mixture of Co _0.2 O ₂ and 40 wt% and 60 wt% respectively was used.

Example 4 As the positive electrode active material, Li _1.85 Mn ₂ O ₄ and LiNi _0.8
A cylindrical battery was produced in the same manner as in Example 1 except that Co _0.2 O ₂ was mixed in the proportions of 20% by weight and 80% by weight, respectively.

Example 5 Li _1.85 Mn ₂ O ₄ as a positive electrode active material and LiNi obtained by the preparation method 2 of lithium-nickel composite oxide
_0.3 Co _0.7 O ₂ , 80 wt%, 20 wt%
Example 1 except using a mixture mixed in the following proportions
A cylindrical battery was produced in the same manner as in.

Example 6 Li _1.85 Mn ₂ O ₄ and LiNiO _{2 were} used as positive electrode active materials.
A cylindrical battery was produced in the same manner as in Example 1 except that a mixture in which each of the above components was mixed at a ratio of 80% by weight and 20% by weight was used.

Example 7 As the positive electrode active material, Li _2.05 Mn ₂ O ₄ and LiNi _0.8 obtained by the preparation method 3 of lithium-manganese composite oxide were used.
A cylindrical battery was produced in the same manner as in Example 1 except that a mixture of Co _0.2 O ₂ and 80 wt% and 20 wt% respectively was used.

Example 8 As positive electrode active materials, Li _0.95 Mn ₂ O ₄ and LiNi _0.8 obtained by the preparation method 1 of lithium-manganese composite oxide were used.
A cylindrical battery was produced in the same manner as in Example 1 except that a mixture of Co _0.2 O ₂ and 80 wt% and 20 wt% respectively was used.

Example 9 As the positive electrode active material, Li _1.85 Mn ₂ O ₄ and LiNi _0.8
A cylindrical battery was produced in the same manner as in Example 1 except that a mixture of Co _0.2 O ₂ and 90 wt% or 10 wt% was used.

Example 10 As the positive electrode active material, Li _1.85 Mn ₂ O ₄ and LiNi _0.8
A cylindrical battery was produced in the same manner as in Example 1 except that a mixture of Co _0.2 O ₂ and 10 wt% and 90 wt% respectively was used.

Comparative Example 1 As a positive electrode active material, 100% by weight of Li _1.85 Mn ₂ O ₄ obtained by the method 2 for preparing a lithium-manganese composite oxide was used.
A cylindrical battery was produced in the same manner as in Example 1 except that it was used.

Comparative Example 2 As the positive electrode active material, 10 LiNi _0.8 Co _0.2 O ₂ obtained by the preparation method 1 of the lithium-nickel composite oxide was used.
A cylindrical battery was produced in the same manner as in Example 1 except that 0% by weight was used.

A cycle life test was conducted on the cylindrical battery manufactured as described above as follows.

That is, first, the charging voltage of each battery is set to 4.
After charging under the conditions of 20 V, charging current 1000 mA and charging time 2.5 hours, the charging / discharging cycle of discharging under the conditions of discharge current 500 mA and end voltage 2.75 V is repeated, and the capacity of the second cycle of each battery Against 20
The capacity retention rate at the 0th cycle was examined.

The results are shown in Table 1 below.

[0079]

[Table 1]

As can be seen from Table 1, the batteries of Examples 1 to 10 using the mixture of the lithium-manganese composite oxide and the lithium-nickel composite oxide as the positive electrode active material, especially the lithium-manganese composite oxide. The batteries of Examples 1 to 8 having a mixing ratio of 20 to 80% by weight have a higher capacity retention rate than the batteries of Comparative Examples 1 and 2.

This is because when a mixture of a lithium-manganese composite oxide and a lithium-nickel composite oxide is used as the positive electrode active material, the lithium-manganese composite oxide and the lithium-nickel composite oxide are This is because the volume changes of the positive electrode active material as a whole are reduced by canceling out the volume changes associated with charge and discharge. In particular, when the mixing ratio of the lithium-manganese composite oxide is 20 to 80% by weight, such an action works properly, and the volume change due to charge and discharge is further suppressed.

As in Comparative Example 1, only with the lithium-manganese composite oxide, the volume change due to the charging and discharging thereof greatly affects the volume of the whole positive electrode active material, and the cycle deterioration becomes large. Further, as in Comparative Example 2, only with the lithium-nickel-based composite oxide, similarly, the volume change due to charging / discharging greatly affects the volume of the whole positive electrode active material, and the cycle deterioration becomes large.

The lithium-nickel composite oxide L
For the composition of iNi _y Co _1-y , here is LiNi
_0.8 Co _0.2 O ₂ , LiNi _0.3 Co _0.7 O ₂ , LiN
Although iO ₂ is used, the same effect is obtained regardless of which is used.

Further, lithium-manganese composite oxide Li
_{For x} Mn ₂ O ₄ , Li prepared by thermochemical method
_0.95 Mn ₂ O ₄ , Li _1.85 M prepared by electrochemical method
Although n ₂ O ₄ and Li _2.05 Mn ₂ O ₄ prepared by a chemical method are used, the same effect can be obtained in any case.

From this, the Li composition ratio x of the lithium-manganese composite oxide Li _x Mn ₂ O ₄ is 0.95 or more,
Lithium-nickel composite oxide LiNi _y Co _1-y O
It was confirmed that the composition ratio y of Ni of ₂ is suitably 0.3 or more and 1.0 or less.

Although the present invention is applied to the cylindrical battery in the present embodiment, it is needless to say that the present invention exerts the same effect even when applied to the prismatic type, coin type and button type.

[0087]

As is apparent from the above description, in the present invention, since the mixture of the lithium-manganese composite oxide and the lithium-nickel composite oxide is used as the positive electrode active material, the lithium-manganese composite oxide is used. It is possible to offset the mutual properties of the oxide and the lithium-nickel-based composite oxide, and reduce the volume change of the positive electrode active material as a whole due to charge and discharge. As a result, the positive electrode active material hardly receives stress due to volume change, and good contact with the conductive agent is maintained, so that the cycle life is improved.

Therefore, according to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery having excellent cycle characteristics while ensuring a high energy density, and its industrial value is great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a non-aqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

 1 negative electrode 2 positive electrode

Claims (4)

[Claims] 1. A nonaqueous electrolytic solution comprising a positive electrode using a lithium compound as a positive electrode active material, a negative electrode using a carbonaceous material capable of doping and dedoping lithium as a negative electrode active material, and a nonaqueous electrolytic solution. A secondary battery, wherein the positive electrode active material is a mixture of a lithium-manganese composite oxide and a lithium-nickel composite oxide. 2. The lithium-manganese oxide is Li _x
The non-aqueous electrolyte secondary battery according to claim 1, wherein Mn ₂ O ₄ (where x is x ≧ 0.95). 3. The lithium-nickel composite oxide is LiNi _y Co _{1 -y} O ₂ (where y is 0.3 ≦ y ≦ 1.
It is 0), The non-aqueous electrolyte secondary battery according to claim 1 or 2. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the mixture ratio of the lithium-manganese composite oxide in the mixture is 20 to 80% by weight.