JP2003217568A - Positive electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery that has high capacity and is superior in cycle characteristics as well as heat resistance. <P>SOLUTION: This is a non-aqueous electrolyte secondary battery that comprises a positive electrode active material made of a mixture of a lithium manganese complex oxide as expressed by LiMn<SB>2-x</SB>M<SB>x</SB>O<SB>4</SB>(provided that the element M is at least one kind selected from Co, Ni, Fe, Mg, Cr, and Al and the composition ratio x is 0<x≤0.4) and a lithium nickel complex oxide as expressed by LiNi<SB>1-y</SB>L<SB>y</SB>O<SB>2</SB>(provided that the element L is at least one kind selected from Co, Ni, Fe, Mg, Cr, and Al, and the composition ratio y is 0<y≤0.5). The composition ratio of the lithium nickel complex oxide in the positive electrode active material is 0.1 mass % or more and 5 mass % or less. <P>COPYRIGHT: (C)2003,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,
In particular, the present invention relates to a technique for improving heat resistance of a non-aqueous electrolyte secondary battery that can be used as a power source for a power storage device, an electric vehicle, an outdoor UPS, and the like.

[0002]

2. Description of the Related Art With the recent increase in energy and environmental problems, development of high-performance lithium secondary batteries is urgently needed. Among various lithium secondary batteries, a lithium secondary battery using a metal oxide as a positive electrode active material is most promising in that it has a high energy density. Conventionally, batteries using lithium cobalt oxide (LiCoO ₂ ) as a metal oxide have been commercially available. However, since cobalt is a rare resource and is expensive, recently, lithium cobalt oxide has been replaced with cheaper manganese. Lithium acid (LiMn
The use of ₂ O ₄ ) is under consideration.

Lithium manganate is cheaper than lithium cobaltate, but when stored in an organic electrolyte at a high temperature of 60 ° C., a part of manganese elutes in the organic electrolyte, and the cycle characteristics of the lithium secondary battery at high temperature and There is a problem that self-discharge is severely deteriorated. Further, since lithium manganate has a theoretical capacity lower than that of lithium cobalt oxide, there is a problem that the energy density of the lithium secondary battery decreases. Therefore, recently, an attempt is being made to increase the capacity of the battery by adding lithium nickel oxide (LiNiO ₂ ) having a relatively higher capacity than lithium manganate or lithium cobalt oxide to lithium manganate.

Lithium nickelate has a higher capacity than lithium manganate, but has the property of being easily thermally decomposed at a relatively high temperature of 100 to 200 ° C. Therefore, like lithium manganate, by substituting a part of nickel contained in lithium nickelate with another element,
Attempts have been made to increase heat resistance, but at present it is not sufficient.

[0005]

Each of the above-mentioned series of positive electrode active materials has merits and demerits, but in a large capacity lithium secondary battery used for power storage etc., an inexpensive material is used from the viewpoint of cost reduction. Therefore, lithium manganate is most promising among the above-mentioned positive electrode active materials. Therefore, it is required to increase the capacity of lithium manganate and improve the cycle characteristics.

The present invention has been made in view of the above circumstances, and is a non-aqueous electrolyte 2 having a high capacity and excellent cycle characteristics.
The purpose is to provide a secondary battery.

[0007]

In order to achieve the above object, the present invention has the following constitutions. The electrode for a non-aqueous electrolyte secondary battery of the present invention comprises LiMn _2-x M _x O ₄ (where the element M is at least one selected from Co, Ni, Fe, Mg, Cr and Al, and the composition is The ratio x is 0 <x ≦
Lithium manganese composite oxide represented by 0.4) and LiNi _1-y L _y O ₂ (where the element L is Co, Ni,
At least one selected from Fe, Mg, Cr, and Al, and the composition ratio y is 0 <y ≦ 0.5). And a composition ratio of the lithium nickel composite oxide in the positive electrode active material is in the range of 0.1% by mass or more and 5% by mass or less.

The non-aqueous electrolyte secondary battery electrode comprises a positive electrode active material composed of a lithium manganese composite oxide and 0.1 to 5% by mass of a lithium nickel composite oxide,
Since the lithium manganese composite oxide is the main component, a battery having higher heat resistance than the conventional non-aqueous electrolyte secondary battery can be provided. In addition, since the lithium-nickel composite oxide has a higher capacity and excellent cycle characteristics than the lithium-manganese composite oxide, the disadvantage of the lithium-manganese composite oxide can be compensated by adding it in the range of 0.1 to 5 mass%. it can.

The electrode for a non-aqueous electrolyte secondary battery of the present invention is the electrode for a non-aqueous electrolyte secondary battery described above, wherein the composition ratio of the lithium nickel composite oxide in the positive electrode active material is 0. It is characterized by being in the range of 1% by mass or more and less than 3% by mass.

According to the non-aqueous electrolyte secondary battery electrode,
Since the addition amount of the lithium nickel composite oxide is limited to the range of 0.1% by mass or more and less than 3% by mass, thermal decomposition of the positive electrode active material is prevented even when the temperature of the battery rises, and charge / discharge of the battery is performed. Capacity does not decrease.

The non-aqueous electrolyte secondary battery electrode of the present invention is the above-mentioned non-aqueous electrolyte secondary battery electrode, wherein the positive electrode active material contains polyaniline in an amount of 0.1% by mass or more and 5% by mass or less. It is characterized by being included in the range of.

According to the non-aqueous electrolyte secondary battery electrode,
Since the positive electrode active material contains polyaniline and the resistance of the positive electrode active material itself can be reduced, the internal impedance of the battery can be reduced and the charge / discharge capacity can be increased.

Next, the non-aqueous electrolyte secondary battery of the present invention is made of Li
Mn _2-x M _x O ₄ (where element M is Co, Ni, Fe, M
g, Cr, at least one selected from among Al, and lithium-manganese composite oxide represented by the composition ratio x is 0 <x ≦ 0.4), LiNi 1-y L y O 2 (However, the element L is at least one selected from Co, Ni, Fe, Mg, Cr, and Al, and the composition ratio y is 0 <y.
≦ 0.5), and a composition ratio of the lithium nickel composite oxide in the positive electrode active material is 0.1 mass. % Or more and 5 mass% or less.

The non-aqueous electrolyte secondary battery comprises a positive electrode active material composed of a lithium manganese composite oxide and 0.1 to 5% by mass of a lithium nickel composite oxide, and is mainly composed of the lithium manganese composite oxide. Therefore, the heat resistance can be improved as compared with the conventional non-aqueous electrolyte secondary battery. In addition, since the lithium nickel composite oxide has a higher capacity and better cycle characteristics than the lithium manganese composite oxide,
By adding in the range of up to 5% by mass, the disadvantage of the lithium manganese composite oxide can be compensated.

The non-aqueous electrolyte secondary battery of the present invention is the non-aqueous electrolyte secondary battery described above, wherein the composition ratio of the lithium nickel composite oxide in the positive electrode active material is 0.1.
It is characterized by being in the range of 1% by mass or more and less than 3% by mass.

According to such a non-aqueous electrolyte secondary battery, since the amount of the lithium nickel composite oxide added is limited to the range of 0.1% by mass or more and less than 3% by mass, even when the temperature of the battery rises, The thermal decomposition of the positive electrode active material is prevented, and the charge / discharge capacity of the battery does not decrease.

The non-aqueous electrolyte secondary battery of the present invention is the non-aqueous electrolyte secondary battery described above, wherein the positive electrode active material contains polyaniline in a range of 0.1% by mass or more and 5% by mass or less. It is characterized by being

According to such a non-aqueous electrolyte secondary battery, since the positive electrode active material contains polyaniline and the resistance of the positive electrode active material itself can be reduced, the internal impedance of the battery is lowered and the charge / discharge capacity is increased. You can

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a non-aqueous electrolyte secondary battery that is an embodiment of the present invention. This non-aqueous electrolyte 2
The secondary battery 1 is of a so-called prismatic type, and has a plurality of positive electrode electrodes (electrodes) 2, a plurality of negative electrode electrodes 3, and separators 4 arranged between the positive electrode electrode 2 and the negative electrode electrode 3. And a non-aqueous electrolytic solution (non-aqueous electrolyte). The positive electrode 2, the negative electrode 3, the separator 4, and the nonaqueous electrolytic solution are housed in a battery case 5 made of stainless steel or the like. A sealing plate 6 is attached to the upper part of the battery case 5. A safety valve 9 for preventing an increase in the internal pressure of the battery is provided at substantially the center of the sealing plate 6. For the separator 4, a porous polymer material film such as polyethylene or polypropylene, glass fiber, or a non-woven fabric made of various polymer fibers is used.

A positive electrode tab 12 is formed at one end of the positive electrode 2, and the positive electrode tab 12 is formed above the positive electrode tab 12a.
A positive electrode lead 12b for connecting a ... Is attached. A positive electrode terminal 7 penetrating the sealing plate 6 is attached to the positive electrode lead 12b. Similarly, the negative electrode 3 ...
Is formed at one end of the negative electrode tab 13a.
A negative electrode lead 13b for connecting the negative electrode tabs 13a is attached to the upper part of a. This negative electrode lead 13b
A negative electrode terminal 8 penetrating the sealing plate 6 is attached to the. With the above configuration, current can be taken out from the positive electrode terminal 7 and the negative electrode terminal 8.

Next, as shown in FIG. 2, the negative electrode 3 is made of Cu.
It is composed of a negative electrode collector 3a made of foil or the like, and a negative electrode film 3b formed on the negative electrode collector 3a. The above-mentioned negative electrode tab 13a is formed to project at one end of the negative electrode current collector 3a. The negative electrode film 3b is formed, for example, by mixing a negative electrode active material powder such as graphite and a binder such as polyvinylidene fluoride. In addition, a conductive auxiliary material powder such as carbon black may be added to the negative electrode film 3b.

As the negative electrode active material, in addition to graphite, various carbon materials such as coke, amorphous carbon, graphitized carbon fiber, and a fired body of various polymer materials can be used. In addition to the carbon material, lithium metal, alloys of lithium and various metals, various metal oxides represented by tin, and the like can also be used. The metallic lithium or alloy is not necessarily limited to powder and may be foil-like. Further, as the binder for the negative electrode 3, besides poly (vinylidene fluoride), poly (tetrafluoroethylene), polyimide or the like can be used.

Similarly, the positive electrode 2 is composed of a positive electrode current collector (current collector) 2a made of, for example, Al foil, and a positive electrode electrode film (electrode film) 2b formed on the positive electrode current collector 2a. Has been done. The positive electrode tab 12a described above is formed to project from one end of the positive electrode current collector 2a. The positive electrode film 2b is formed into a film by mixing a solid content and a binder, and the solid content contains at least a positive electrode active material powder (electrode active material) and a conductive auxiliary material powder.

Then, as shown in FIG. 2, the positive electrode film 2b
And the negative electrode film 3b face each other via the separator 4. In FIG. 2, the electrode films 2b and 3b are formed on one surface of each of the current collectors 2a and 3a for the sake of simplification of description. Needless to say, the films may be formed on both surfaces of the electric bodies 2a and 3a.

The positive electrode film 2b contains at least a positive electrode active material, a conductive auxiliary material, and a binder. The positive electrode active material is a mixture of a lithium manganese composite oxide represented by the composition formula LiMn _2-x M _x O ₄ and a lithium nickel composite oxide represented by the general formula LiNi _1-y L _y O _2. In other words, the lithium manganese composite oxide is contained as the main component and the lithium nickel composite oxide is contained as the auxiliary component. The lithium-manganese composite oxide has a relatively small theoretical capacity and a relatively short cycle life, but has a property that it is relatively stable even at a high temperature of 100 to 200 ° C. and is hardly decomposed by heat. On the other hand, the lithium nickel composite oxide is
Excellent theoretical capacity and cycle life, but 100-2
It has the property of being relatively unstable at high temperatures such as 00 ° C and easily decomposed.

Since the positive electrode active material is mainly composed of lithium manganese composite oxide, the temperature inside the battery is 100 to 2
Even when the temperature rises to about 00 ° C., the positive electrode active material is not likely to be thermally decomposed, and the charge / discharge capacity of the battery can be maintained high. In addition, since the lithium nickel composite oxide has a higher capacity and superior cycle characteristics than the lithium manganese composite oxide, adding the lithium nickel composite oxide compensates for the disadvantages of the lithium manganese composite oxide and makes the positive electrode active material have a high capacity. And the cycle characteristics can be improved.

The lithium manganese composite oxide is LiMn.
_2-x M _x O ₄ (However, element M is Co, Ni, Fe, Mg,
At least one selected from Cr and Al,
The composition ratio x is represented by 0 <x ≦ 0.4),
A part of Mn (manganese) of LiMn ₂ O ₄ showing a spinel crystal structure is replaced with the element M. It is said that the addition of the element M is effective in preventing the displacement of the crystal structure due to the yarn-Teller transition caused by the charge / discharge reaction and the reduction of the diffusion rate of lithium in the composite oxide. The composition ratio x of the element M is 0 <x ≦ 0.4
Is preferred. When the element M is not added, the crystal structure is displaced due to the yarn-Teller transition, and the spinel crystal structure cannot be maintained, which is not preferable. When the composition ratio x of the element M exceeds 0.4, the crystal structure of the active material is not obtained. In addition, it is not preferable because the charge / discharge capacity is reduced due to the decrease in the number of manganese occupied sites.

The lithium nickel composite oxide is L
iNi _1-y L _y O ₂ (provided that the element L is Co, Ni, Fe,
It is at least one selected from Mg, Cr and Al, and the composition ratio y is represented by 0 <y ≦ 0.5), and Ni (nickel) of LiNiO ₂ showing a layered rock salt structure. In which a part of is replaced by the element L. By adding the element L, it is possible to improve the heat resistance of the lithium nickel composite oxide and prevent thermal decomposition at high temperatures. The composition ratio y of the element L is preferably in the range of 0 <y ≦ 0.5. When the element L is not added, the heat resistance of the lithium nickel composite oxide is lowered and the lithium nickel composite oxide is thermally decomposed at about 100 to 200 ° C., which is not preferable. If the composition ratio y of the element L exceeds 0.5, the LiNiO ₂ phase Since the composition is relatively decreased, the charge / discharge capacity is decreased, and at the same time, the electron conductivity of the active material itself is decreased, which may increase the internal resistance of the battery, which is not preferable.

The composition ratio of the lithium nickel composite oxide in the positive electrode active material is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and less than 3% by mass. When the composition ratio of the lithium-nickel composite oxide is less than 0.1% by mass, the charge / discharge capacity of the positive electrode active material is lowered and the cycle characteristics are deteriorated, which is not preferable. It is not preferable because the heat resistance of the active material decreases. Further, if the composition ratio of the lithium nickel composite oxide is less than 3% by mass, the heat resistance of the non-aqueous electrolyte secondary battery can be further improved. Specifically, the heat resistance of the battery can be improved without decomposing the positive electrode active material even when the battery temperature rises by performing a severe destructive test such as a nailing test.

Further, it is preferable to add a conductive polymer material such as polyaniline, polypyrrole, polythiophene and polyimidazole to the positive electrode active material, and it is particularly preferable to add polyaniline. Since the conductive polymer material is electrochemically stable and has excellent electronic conductivity, the resistance of the positive electrode film 2b is reduced by adding these conductive polymer materials, and the internal impedance of the battery is reduced. Has the effect of lowering the charge and discharge capacity. The composition ratio of the conductive polymer material such as polyaniline in the positive electrode active material is preferably 0.1% by mass or more and 5% by mass or less. If the composition ratio is less than 0.1% by mass, the above-described effect of the addition of the conductive polymer material is not observed, which is not preferable, and if the composition ratio exceeds 5% by mass, the electron conductivity due to excessive coating of the conductive polymer material is caused. Is inhibited, which is not preferable.

Next, a carbon material such as carbon black, acetylene black, graphite or carbon fiber is preferably used as the conductive auxiliary material. As the binder, it is preferable to use a polymer binder such as polyvinylidene fluoride, polytetrafluoroethylene, or polyimide. Further, as the positive electrode current collector 2a, it is preferable to use a metal foil, a metal net, an expanded metal or the like, and these materials are Al and T.
i, stainless steel, etc. are preferable.

The composition ratio of the positive electrode film 2b is preferably in the range of 60 to 90% by weight of the positive electrode active material, 5 to 20% by weight of the conductive auxiliary material, and 5 to 20% by weight of the binder. The positive electrode active material at this time includes a lithium manganese composite oxide, a lithium nickel composite oxide, and a conductive polymer material.

Next, as the non-aqueous electrolyte (non-aqueous electrolyte),
For example, in a mixed solvent obtained by mixing a cyclic carbonic acid ester such as ethylene carbonate and butylene carbonate and a chain carbonic acid ester such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, LiPF ₆ , L
iBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ S
It is possible to use one in which one or two or more solutes composed of a lithium salt such as O ₃ and Li (CF ₃ SO ₂ ) ₂ N are dissolved.

A solid electrolyte (non-aqueous electrolyte) may be used instead of the separator 4 and the non-aqueous electrolyte solution. As the solid electrolyte, a lithium ion conductive polymer such as polyethylene oxide containing the above solute,
A gel electrolyte obtained by impregnating a polymer matrix such as polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile or the like with the above non-aqueous electrolyte can be used.

The method for producing the positive electrode 2 is not particularly limited, but the lithium manganese composite oxide powder and the lithium nickel composite oxide powder are mixed with a conductive auxiliary material such as carbon black, and this mixture is mixed. NMP in which a binder such as polyvinylidene fluoride and polyaniline are dissolved in advance
It is obtained by adding a dispersion medium such as the above to form a slurry, applying the slurry to a positive electrode current collector by a doctor blade method or the like, removing the dispersion medium by heating, and compressing by a press or the like.

[0036]

[Example] [Experimental Example 1 (Investigation of capacity retention rate at high temperature)]
For the synthesis of lithium manganate, lithium carbonate and manganese dioxide were used as starting materials. Lithium manganate having a composition of LiMn ₂ O ₄ was obtained by sufficiently pulverizing these starting materials, mixing them so that Li / Mn = 1/2 (atomic ratio), and firing at 850 ° C. in an oxygen atmosphere. Got Next, for the synthesis of lithium nickelate, lithium nitrate and nickel hydroxide were used as starting materials. After sufficiently pulverizing these starting materials, Li / Ni = 1/1
(Atomic ratio) and mix in an oxygen atmosphere at 700 ° C
By firing at, lithium nickel oxide having a composition of LiNiO ₂ was obtained. The lithium manganate had an average particle diameter of 15 μm and a specific surface area of 0.1 m ² / g, and the lithium nickel oxide had an average particle diameter of 11 μm and a specific surface area of 0.2 m ² / g.

The above-mentioned lithium manganate and lithium nickelate were mixed at a mixing ratio shown in Table 1 to prepare a positive electrode active material,
To 90 parts by weight of this positive electrode active material, 10 parts by weight of carbon black as a conduction aid was added to obtain a mixture. The obtained mixture is mixed with NMP (N-methylpyrrolidone) in which polyvinylidene fluoride is dissolved in advance to form a slurry, and the slurry is applied to an aluminum foil and dried,
Further pressing was performed to form a positive electrode film. Thus, the positive electrode active material was 82% by mass, the carbon black was 9% by mass, the polyvinylidene fluoride was 9% by mass, and the density of the positive electrode active material in the positive electrode film was 25 mg /
A positive electrode having a cm ² and a density of the positive electrode film of 2.4 g / cm ³ was manufactured. The positive electrode used was punched into a circular shape having a diameter of 16 mm.

Next, natural graphite is mixed with NMP (N-methylpyrrolidone) in which polyvinylidene fluoride is dissolved in advance to form a slurry. The slurry is applied to a copper foil, dried, and further pressed. A negative electrode film was formed. Thus, 90% by mass of natural graphite and 10% by mass of polyvinylidene fluoride, the density of natural graphite in the negative electrode film is 10 mg / cm ² , and the density of the negative electrode film is 1.2 g / cm ³ . A negative electrode was manufactured. In addition,
As with the positive electrode, the negative electrode was also punched into a circular shape having a diameter of 16 mm.

By putting a porous polypropylene separator between the positive electrode and the negative electrode in a battery container, injecting an organic electrolytic solution, and then sealing the container,
A coin type non-aqueous electrolyte secondary battery (Examples 1 to 3 and Comparative Examples 1 and 2) having a diameter of 16 mm and a thickness of 3 mm was obtained. The composition of the organic electrolyte is a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC: DMC = 1: 2 by volume ratio).
LiPF ₆ was added so that the concentration became 1 mol / L.

With respect to the obtained non-aqueous electrolyte secondary battery, the capacity retention at high temperature was measured while repeating the charge / discharge cycle. For charging, constant current charging is performed at a current of 1 / 3C until the voltage reaches 4.2V, and then constant voltage charging is performed at 4.2V for 5 hours, and discharging is performed at a current of 1 / 3C and a voltage of 2.2V.
It was decided to carry out constant current discharge until. 5 under this condition
After charging and discharging until the cycle, the temperature is 60 ℃ in the charged state.
After 30 days of storage, discharge was performed, and the rate of change in discharge capacity before and after storage was determined as the capacity retention rate. The results are shown in Table 1.
Shown in.

[0041]

[Table 1]

As shown in Table 1, in Examples 1 to 3, the capacity retention rate increased as the composition ratio of lithium nickel oxide increased. It is considered that this is because the amount of lithium nickel oxide, which has relatively better cycle characteristics during high temperature storage than lithium manganate, increased. It was also confirmed that the capacity retention rate was further improved by adding polyaniline to the positive electrode. It is considered that this is because the elution of manganese was suppressed because polyaniline appropriately covered the positive electrode active material particles. In addition, Comparative Examples 1 and 2
Lithium manganate and lithium nickelate were added individually, and it is shown that lithium nickelate is superior to lithium manganate in the capacity retention rate at high temperatures.

[Experimental Example 2 (Investigation of heat resistance)] A strip electrode was prepared as a positive electrode, and a strip electrode was prepared as a negative electrode. Porous polypropylene made between these positive and negative electrodes was prepared. A diameter of 1 was obtained in the same manner as in the case of Experimental Example 1 above, except that a separator was placed and spirally wound together with the positive and negative electrodes and inserted into the battery container.
A cylindrical non-aqueous electrolyte secondary battery having a height of 8 mm and a height of 650 mm was manufactured. The obtained non-aqueous electrolyte secondary battery was charged with a constant current at a current of 1/3 C until the voltage reached 4.15 V, and then charged with a constant voltage at 4.15 V for 5 hours to fully charge the battery. Charged. A nail penetration test was performed by driving a nail having a diameter of 2 mm and a length of 50 mm into the fully charged non-aqueous electrolyte secondary battery to investigate the behavior of the battery. The results are shown in Table 2. In order to correct the influence of variations for each test battery, three batteries were manufactured under each condition and tested. In Table 2, "1" shown in the column of result of battery behavior
The description such as "/ 3" means that, for example, one of the three batteries tested for each example caused valve operation.

[0044]

[Table 2]

As shown in Table 2, in Examples 6 to 7, the operation of the safety valve and the generation of white smoke occurred, but the leak of the built-in solid did not occur and the ignition did not occur. Comparative Example 3 containing 100% lithium manganate was also the same as Examples 6-7. However, as the composition of lithium nickelate increases, the frequency of leakage of built-in solids increases, and as shown in Example 9, under the condition of containing 5 mass% of lithium nickelate, two out of three batteries leak to the built-in solids. Really
On the other hand, in Comparative Example 4 containing 100% lithium nickelate, in addition to the operation of the safety valve and the generation of white smoke, the contents spouted and further ignition occurred. The above results are due to the fact that lithium nickel oxide is more likely to cause thermal runaway at a lower temperature than lithium manganate. It was confirmed that the content is preferably not more than mass%.

As is clear from Experimental Examples 1 and 2, the non-aqueous electrolyte secondary batteries of Examples 1 to 6 in which a part of lithium manganate was lithium nickelate were manufactured using lithium manganate or lithium nickelate. It was found that the batteries of Comparative Examples 1 and 2 which contained alone had a higher capacity retention rate at high temperature and a higher heat resistance.

[0047]

As described above in detail, according to the non-aqueous electrolyte secondary battery of the present invention, the positive electrode active material composed of the lithium manganese composite oxide and the lithium nickel composite oxide of 0.1 to 5 mass% is used. Since it is made of a substance and is mainly composed of lithium manganese composite oxide, the conventional non-aqueous electrolyte 2
The heat resistance can be improved as compared with the secondary battery. Moreover, since the lithium nickel composite oxide has a higher capacity and better cycle characteristics than the lithium manganese composite oxide, 0.1 to 5% by mass is used.
Addition within this range can compensate for the disadvantages of the lithium-manganese composite oxide.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a main part of the non-aqueous electrolyte secondary battery shown in FIG.

[Explanation of symbols]

1 Non-aqueous electrolyte secondary battery 2 Positive electrode (electrode) 2a Positive electrode current collector (current collector) 2b Positive electrode film (electrode film) 3 Negative electrode 3a Negative electrode current collector 3b Negative electrode film 4 separator 5 battery case 6 sealing plate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hidehiko Tajima             1-1 Satinoura Town, Nagasaki City, Nagasaki Prefecture Mitsubishi Heavy Industries             Nagasaki Shipyard Co., Ltd. F term (reference) 5H029 AJ03 AJ05 AJ12 AK03 AK16                       AK18 AL02 AL06 AL07 AL12                       AM03 AM05 AM07 AM16 BJ02                       CJ08 DJ16 DJ17 HJ01 HJ02                 5H050 AA07 AA08 AA15 BA17 CA08                       CA09 CA20 CA29 CB02 CB07                       CB08 CB12 DA02 FA17 FA19                       GA10 HA01 HA02

Claims (6)

[Claims] 1. LiMn _2-x M _x O ₄ (where the element M is C
o, Ni, Fe, Mg, Cr, Al, and at least one kind, and the composition ratio x is 0 <x ≦ 0.4.
i _1-y L _y O ₂ (provided that the element L is Co, Ni, Fe, M
g, Cr, Al, which is at least one selected from the group consisting of Al, and the composition ratio y is 0 <y ≦ 0.5). A positive electrode for a non-aqueous electrolyte secondary battery, characterized in that the composition ratio of the lithium nickel composite oxide in the positive electrode active material is in the range of 0.1% by mass or more and 5% by mass or less. 2. The composition ratio of the lithium nickel composite oxide in the positive electrode active material is 0.1% by mass or more and 3% by mass.
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode is in the range below. 3. The positive electrode active material contains polyaniline in an amount of 0.1.
The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the positive electrode is contained in the range of 5% by mass or more and 5% by mass or less. 4. LiMn _2-x M _x O ₄ (provided that the element M is C
o, Ni, Fe, Mg, Cr, Al, and at least one kind, and the composition ratio x is 0 <x ≦ 0.4.
i _1-y L _y O ₂ (provided that the element L is Co, Ni, Fe, M
g, Cr, Al, which is at least one selected from the group consisting of Al, and the composition ratio y is 0 <y ≦ 0.5). The non-aqueous electrolyte secondary battery, wherein the composition ratio of the lithium nickel composite oxide in the positive electrode active material is in the range of 0.1% by mass or more and 5% by mass or less. 5. The composition ratio of the lithium nickel composite oxide in the positive electrode active material is 0.1% by mass or more and 3% by mass.
The non-aqueous electrolyte secondary battery according to claim 4, wherein the non-aqueous electrolyte secondary battery is in a range below. 6. Polyaniline is added to the positive electrode active material in an amount of 0.1.
The non-aqueous electrolyte secondary battery according to claim 4 or 5, wherein the non-aqueous electrolyte secondary battery is contained in the range of 5% by mass or more and 5% by mass or less.