JP2003264006A - Lithium ion secondary battery and method of charging lithium ion secondary battery - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a lithium ion secondary battery that has improved energy density and excellent cycle life. SOLUTION: When charging a lithium ion secondary battery containing a positive electrode containing a lithium transition metal composite oxide and a negative electrode containing a carbon material, the following general lithium transition metal composite oxide is used. The one represented by the formula (1) is used, and the upper limit voltage of charging is 4.15 to 4.4.
V. ## STR00001 ## Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) (where X is 0 <X ≦ 1.2, and Y and Z are 0.7 ≦ Y /
Represents a number satisfying the relationship of Z ≦ 9 and 0 ≦ (1-YZ) ≦ 0.5, and Q is a transition metal of the fourth period, B, Al,
It represents at least one element selected from Ga, Zn, Be, Mg and Ca. )

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, it has become possible to reduce the size and weight of electronic equipment.
Then, as its power source, lithium for electronics
Ion secondary batteries have been put to practical use,
It is used in portable personal computers and mobile phones. further
, Electric cars are attracting attention due to environmental issues, etc.
High energy density, sealed type and maintenance-free
Attention is focused on the lithium-ion secondary battery. Conventional
The positive electrode of the lithium-ion secondary battery is a positive electrode active material, a conductive material,
LiCoO composed of a binder and used as a positive electrode active material ₂,
LiNiO₂Lithium transition metal composite oxide such as
It is known that a carbon material is used as a negative electrode.

In order to maintain a long life, such a lithium ion secondary battery is usually used with the upper limit voltage set to 4.1V. If the upper limit voltage is set high, the energy density can be improved, and it is required to increase the upper limit voltage in order to realize a more compact battery. Further, if the upper limit voltage is high, more rapid charging can be made possible, and in addition to the above effects, a battery advantageous for automobiles, industrial use, etc. can be realized.

[0004]

However, almost no lithium secondary battery having an upper limit voltage higher than 4.1 V has been found. This is because the layered composite oxide such as LiCoO ₂ or LiNiO ₂ has a reduced cycle life when the upper limit voltage is higher than 4.1V. Some spinel Mn-based positive electrodes have an upper limit voltage of 4.2 V, but the discharge capacity is small and the energy density is low. Also, the cycle life cannot be said to be sufficiently long.

Recently, a layered lithium nickel manganese composite oxide was announced as a positive electrode material that can be replaced with these lithium transition metal composite oxides (The 41st Battery Conference 2D)
20 (2000)). Thus, an oxide having a structure in which a part of the nickel site is replaced with manganese (hereinafter referred to as Li-NMC
(Sometimes abbreviated as complex oxide) has attracted attention from the viewpoint that it may bring out the advantages of each element in terms of price, high temperature stability, capacity, and safety. Also,
According to the study by Petr. Novak (LiBD-Electrode ma
terials / Arcachan, France / May27-June1,2001 AbstNo5
6) In the case of a lithium secondary battery in which the negative electrode is Li metal,
The cycle test is performed with the upper limit voltage of 4.4 V, and a long life is obtained. However, since the lithium secondary battery contains pyrophoric lithium metal inside the battery, its safety is not only a concern, but such a lithium secondary battery can be used under the condition that usable Li is inexhaustible. Therefore, even if the movable Li is deactivated to some extent on the positive electrode and the negative electrode along with the cycle, Li is supplemented one after another, so that there is little influence on the life.

On the other hand, the lithium ion secondary battery uses a carbon material as the negative electrode and is more safe than the lithium secondary battery, but the Li contained in the positive electrode in the initial stage.
When is deactivated, this is not supplemented. It is expected that when charge and discharge are repeated at a high voltage, Li easily reacts with the electrolytic solution and the Li involved in charge and discharge is lost, which immediately leads to reduction in battery capacity and shortens life. It is.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a lithium ion having a positive electrode using a lithium transition metal composite oxide and a negative electrode using a carbon material. When a layered lithium nickel manganese composite oxide having a specific composition containing both Ni and Mn is used as the lithium transition metal composite oxide in a secondary battery, an excellent cycle maintenance rate can be obtained even if the upper limit voltage is set high. The inventors have found that they can be achieved and completed the present invention.

That is, the gist of the present invention is as follows (1)
~ (4). (1) In a lithium ion secondary battery containing a positive electrode containing a lithium transition metal composite oxide and a negative electrode containing a carbon material, the lithium transition metal composite oxide is represented by the following general formula (1). And the upper limit voltage of 4.15
To 4.4V for use in lithium-ion secondary battery

[0009]

Embedded image Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) (where X is 0 <X ≦ 1.2 and Y and Z are 0.7 ≦ Y /
It represents a number satisfying the relationship of Z ≦ 9 and 0 ≦ (1−Y−Z) ≦ 0.5, and Q is a transition metal of the fourth period, B, Al,
It represents at least one element selected from Ga, Zn, Be, Mg and Ca. (2) In a lithium ion secondary battery containing a positive electrode containing a lithium transition metal composite oxide and a negative electrode containing a carbon material, the lithium transition metal composite oxide is represented by the following general formula (1). And the voltage is 4.15 ~
Lithium-ion secondary battery characterized by being charged to 4.4V

[0010]

Embedded image Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) (where X is 0 <X ≦ 1.2, Y and Z are 0.7 ≦ Y /
It represents a number satisfying the relationship of Z ≦ 9 and 0 ≦ (1−Y−Z) ≦ 0.5, and Q is a transition metal of the fourth period, B, Al,
It represents at least one element selected from Ga, Zn, Be, Mg and Ca. ) (3) Element Q is Co, B, Al, V, Cr, and F
The lithium ion secondary battery according to (1) or (2) above, which is at least one metal element selected from the group consisting of e. (4) In a charging method for a lithium ion secondary battery containing a positive electrode containing a lithium transition metal composite oxide and a negative electrode containing a carbon material, the lithium transition metal composite oxide has the following general formula (1). And a charging method for a lithium-ion secondary battery, which comprises charging up to an upper limit voltage of 4.15 to 4.4V.

[0011]

Embedded image Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) (where X is 0 <X ≦ 1.2 and Y and Z are 0.7 ≦ Y /
It represents a number satisfying the relationship of Z ≦ 9 and 0 ≦ (1−Y−Z) ≦ 0.5, and Q is a transition metal of the fourth period, B, Al,
It represents at least one element selected from Ga, Zn, Be, Mg and Ca. )

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a Li-NMC layered composite oxide is used as the positive electrode of a non-aqueous electrolyte secondary battery. The Li-NMC composite oxide of the present invention is usually represented by the following general formula (I).

[0013]

Embedded image Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) Here, in the general formula (1), X is 0 <X ≦ 1.2, preferably 0 <X ≦ 1.15. , And more preferably 0 <X ≦ 1.
Represents the number 1. If the value of X is too large, the crystal structure may become unstable or the battery capacity of the lithium secondary battery using this may be reduced. The value of X is usually 0.8 or more, preferably 0.9 or more in the state before assembling the lithium ion secondary battery. On the other hand, the value of X in the lithium-ion secondary battery varies depending on the charging / discharging state and is usually 0.8 to 1.2, preferably 0.9 to 1.1 in the discharging state, and in the charging state. It is usually 0.0 to 0.5, preferably 0.05 to 0.4.

In the above general formula (1), Y and Z are 0.7≤Y / Z≤9, and 0≤ (1-YZ) ≤0.
5 represents a number satisfying the relationship of 5. Y / Z corresponds to the molar ratio of Ni / Mn, 0.7 ≦ Y / Z ≦ 9, preferably 0.8
≦ Y / Z ≦ 8, more preferably 0.9 ≦ Y / Z ≦ 6. When the proportion of manganese is relatively large, it becomes difficult to synthesize a single-phase lithium nickel manganese composite oxide, and conversely, when the proportion of nickel is relatively large,
Overall cost goes up.

Further, in the above general formula (1), a part of the sites of Ni and Mn is replaced with a metal element Q other than these (this metal element may be referred to as "substitution metal element" hereinafter). It is also possible. Such a substitution element Q
As for Q, a transition metal of the fourth period, B, Al, G
Mention may be made of a, Zn, Be, Mg and Ca.
Specifically, Al, Fe, Ga, Bi, Sn, V, C
r, Co, Cu, Zn, Mg, Ti, Ge, Nb, T
a, Zr, Li, and the like, and preferably C
o, B, Al, V, Cr, and Fe. Above all, it is preferable to contain cobalt as the element Q. If the content of the substitutional metal element Q is too large, the capacity when used as an electrode for a battery may be lowered, or the effect of the present invention may not be remarkable, so that (1-Y in the above general formula (1) is used.
The value of -Z) is 0.5 or less, preferably 0.4 or less, more preferably 0.3 or less. The value of 1-Y-Z may be 0, but when the substitutional element Q is contained, the battery performance such as cycle characteristics is further improved. Therefore, the value of 1-Y-Z is usually 0.01 or more, It is preferably 0.05 or more, and more preferably 0.1 or more.

In the composition of the above general formula (1), the oxygen content may have some nonstoichiometry. Li-N
MC composite oxides usually have an average primary particle size of 0.0
1 μm or more, preferably 0.02 μm or more, more preferably 0.1 μm or more, usually 30 μm or less, preferably 5
It is not more than μm, more preferably not more than 2 μm. The average secondary particle size is usually 1 μm or more, preferably 4 μm or more,
It is usually 50 μm or less, preferably 40 μm or less. Further, the Li-NMC composite oxide has a BET specific surface area of usually 0.1 m ² / g or more and 10.0 m ² / g or less, preferably 0.5 m ² / g or more and 9.0 m ² / g or less, and further It is preferably 0.5 m ² / g or more and 7.0 m ² / g or less.

In the present invention, the Li-NM is used.
The specific surface area of the C complex oxide is measured by a known BET type powder specific surface area measuring device. The measurement principle of this method is as follows. That is, the measurement method is the BET one-point method measurement by the continuous flow method, and the adsorption gas and carrier gas used are nitrogen and helium, respectively. The powder sample is degassed by heating with a mixed gas at a temperature of 450 ° C or lower,
Then, the mixed gas is adsorbed by cooling to the liquid nitrogen temperature. This is heated to room temperature with water to desorb the adsorbed nitrogen gas, and the amount is determined as a desorption peak in the thermal conductivity detector to calculate the specific surface area of the sample. Li-
The NMC composite oxide is a mixture of a lithium compound, a nickel compound, a manganese compound, and a compound containing the element Q if necessary, such as a mixture of lithium, nickel, manganese and, if necessary, a raw material containing the element Q. It can be manufactured by subjecting to.

The positive electrode contains the above Li-NMC composite oxide as a positive electrode active material, and usually further contains a binder and a conductive auxiliary agent. The positive electrode is usually the above Li-N
A positive electrode layer containing an MC composite oxide, a conductive additive and a binder is formed on a current collector. Such a positive electrode is usually manufactured by applying a slurry of the above components to a current collector and drying. Alternatively, the positive electrode active material may be roll-formed as it is to form a sheet electrode, or compression-molded to form a pellet electrode. As the positive electrode active material in the positive electrode, a material other than the above Li-NMC composite oxide can be used.

The conductive agent in the positive electrode is not particularly limited, and various conductive materials can be used. Specifically, a carbon material is used as a material having conductivity, and is not particularly limited, and examples thereof include acetylene black, Ketjen black, activated carbon, and carbon fiber. Plural kinds of conductive materials can be used in combination.

Examples of the binder for the positive electrode active material include polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride and EPDM.
(Ethylene-propylene-diene terpolymer), SB
Examples thereof include R (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), and fluororubber, but are not limited to these as long as the active material can be effectively retained on the electrode.

As a solvent for forming a slurry, an organic solvent that dissolves or disperses a binder is usually used. Examples thereof include, but are not limited to, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. . In some cases, the active material is slurried with latex such as SBR by adding a dispersant and a thickener to water.

For the positive electrode current collector, aluminum, stainless steel, nickel-plated steel or the like is used. Aluminum is preferable. In the lithium ion secondary battery of the present invention, a carbon material is used as the negative electrode active material. The type of the carbon material is not particularly limited, but natural or artificial graphite, petroleum-based coke, coal-based coke, petroleum-based pitch carbide, coal-based pitch carbide, phenolic resin / crystalline cellulose resin, and the like. Partially carbonized carbon materials, furnace black, acetylene black, pitch-based carbon fibers, PAN-based carbon fibers, or a mixture of two or more of these may be mentioned.

Of these, artificial graphite, purified natural graphite produced by subjecting easily graphitizable pitches obtained from various raw materials to high temperature heat treatment, and graphite materials obtained by subjecting these graphites to surface treatment at various pitches are preferable. As such a graphite material, the d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by Gakushin method is 0.335 to 0.338 nm, and particularly 0.335 to 0.337 nm. Those are preferable. The ash content is preferably 1% by weight or less, more preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less. The crystallite size (Lc) determined by X-ray diffraction by Gakushin method is 30 n.
m or more is preferable, 50 nm or more is more preferable, 10
0 nm or more is more preferable.

The median diameter of the carbonaceous material powder by the laser diffraction / scattering method is preferably 1 to 100 μm,
It is more preferably 3 to 50 μm or less, further preferably 5 to 40 μm, and particularly preferably 7 to 30 μm. The BET specific surface area is preferably 0.3 to 25.0 m ² / g and is 0.5
-20.0 m < ² > / g is more preferable, 0.7-15.0
m is more preferably ² / g, ^{0.8~10.0m 2} / g is particularly preferred.

The carbonaceous material is 1570 to 1 as determined by Raman spectrum analysis using argon ion laser light.
Peak P _A (peak intensity I _A ) in the range of 620 cm ⁻¹ and 1
Intensity ratio R = I _B / I _A between 300～1400Cm ^-1 in the range of peak P _B (peak intensity I _B) is 0.01.
0, particularly 0.1 to 0.7 is preferable, and 1570 to 162
The full width at half maximum of the peak in the range of 0 cm ^-1 is preferably 26 cm ^-1 or less, and particularly preferably 25 cm ^-1 or less.

A plurality of types of carbon materials may be used as the negative electrode active material in the negative electrode, or active materials other than carbon materials may be used. The average particle size of the carbon material is
1 to 1000 nm is preferable, 10 to 500 nm is more preferable, and 30 to 400 nm is further preferable. If the average particle size is too large, the capacity deterioration due to repeated charging / discharging cycles may increase and the usefulness as an electrode may be impaired. On the contrary, if the average particle size is too small, the surface area increases and the battery safety decreases. The particle size distribution is preferably within these ranges.

The negative electrode is usually formed by forming a negative electrode layer on a current collector as in the case of the positive electrode. The binder used at this time, and the conductive agent and the like used as necessary and the slurry solvent may be the same as those used for the positive electrode. Further, the negative electrode current collector includes copper, nickel,
Stainless steel, nickel plated steel, etc. are used. Copper is preferred.

The active material capacity ratio between the negative electrode and the positive electrode (negative electrode initial charge capacity / positive electrode initial charge capacity: hereinafter abbreviated as cell balance) is usually 0.9 or more and 1.8 or less, preferably 1.0 or more 1. 0.7 or less, more preferably 1.1 or more 1.
It is 6 or less. If the cell balance is too small, the capacity of the lithium ion secondary battery will decrease, and if it is too large, the irreversible capacity due to the negative electrode will increase, and the initial efficiency will decrease. A separator is usually arranged between the positive electrode and the negative electrode. The separator used is usually a microporous polymer film, nylon, cellulose acetate,
Materials made of nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, and polyolefin polymers such as polypropylene, polyethylene, and polybutene are used. The chemical and electrochemical stability of the separator is an important factor. From this point of view, a polyolefin-based polymer is preferable, and from the viewpoint of self-closing temperature which is one of the purposes of the battery separator, polyethylene is preferable.

In the case of a polyethylene separator, ultrahigh molecular weight polyethylene is preferable from the viewpoint of shape retention at high temperature, and the lower limit of its molecular weight is preferably 500,000, more preferably 1,000,000, and most preferably 1,500,000.
On the other hand, the upper limit of the molecular weight is preferably 5,000,000, more preferably 4,000,000, and most preferably 3,000,000. This is because if the molecular weight is too large, the fluidity is so low that the pores of the separator may not close when heated.

A non-aqueous electrolyte is usually used in the lithium ion secondary battery of the present invention. As non-aqueous electrolyte,
An electrolyte solution in which a lithium salt is used as an electrolyte and this is dissolved in an organic solvent is used. Examples of the organic solvent include carbonates, ethers, ketones, sulfolane compounds,
Lactones, nitriles, halogenated hydrocarbons, amines, esters, amides, phosphoric acid ester compounds and the like can be used. To list these representative ones, propylene carbonate, ethylene carbonate,
Chloroethylene carbonate, trifluoropropylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, vinylene carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 4-methyl-2-pentanone, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, 1,3-dioxolane, 4
-Methyl-1,3-dioxolane, diethyl ether,
Sulfolane, methylsulfolane, acetonitrile, propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, dimethylformamide, dimethylsulfoxide, trimethyl phosphate, triethyl phosphate and the like can be used alone or in combination of two or more kinds. In addition, gases such as CO ₂ , N ₂ O, CO, SO _{2 and the} like, polysulfide Sx2-, vinylene carbonate,
An additive such as catechol carbonate that forms a good film capable of efficiently charging and discharging lithium ions on the surface of the negative electrode may be added to the above-mentioned single or mixed solvent at an arbitrary ratio.

The above organic solvent preferably contains a high dielectric constant solvent in order to dissociate the electrolyte. The high dielectric constant solvent in the present invention has a relative dielectric constant of 2 at 25 ° C.
It means 0 or more compounds. In the high dielectric constant solvent, it is preferable that the electrolytic solution contains ethylene carbonate, propylene carbonate, and a compound obtained by substituting hydrogen atoms thereof with another element such as halogen or an alkyl group.
The proportion of the high dielectric constant compound in the electrolytic solution is preferably 2
It is 0% by weight or more, more preferably 30% by weight or more, and most preferably 40% by weight or more. This is because if the content of the compound is small, desired battery characteristics may not be obtained.

As the electrolyte, any conventionally known one can be used.
Can be used, LiClO_Four, LiAsF₆, LiPF₆, Li
BF_Four , LiB (C₆H_Five)_Four, LiCl, LiBr, L
iCH ₃SO₃Li, LiCF₃SO₃, LiN (SO₂C
F₃)₂, LiN (SO₂C₂F_Five) ₂, LiC (SO₂C
F₃)₃, LiN (SO₃CF₃)₂Lithium salts such as
To be

As the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can also be used. The lithium ion secondary battery according to the present invention can be manufactured by a conventional method using the above-mentioned negative electrode, positive electrode and non-aqueous electrolyte solution. The form of the battery can be any commonly used form such as a coin type, a lamin pack type, a cylindrical type, and a single plate laminated type.

The lithium ion secondary battery of the present invention is normally charged at the shipping stage or the like. In the charged state, the battery voltage of the lithium ion secondary battery is 4.15V.
It is preferable that the voltage is 4.4 V or less. Particularly preferably, it is 4.2 V or higher, more preferably 4.25 V or higher,
Further, it is particularly preferably 4.4 V or less, and further preferably 4.35 V or less. If the upper limit voltage is too small, the discharge capacity cannot be expected to be improved, and if the upper limit voltage is too high, the electrolytic solution is decomposed, and as a result, the cycle life tends to be shortened.

The charging method is not particularly limited, and constant voltage charging, constant current charging or a charging method combining these can be adopted. The upper limit voltage in charge / discharge operation of the lithium ion secondary battery of the present invention is 4.15 V or more and 4.4 V or more.
It is the following. The voltage is preferably 4.2 V or higher, more preferably 4.25 V or higher. Further, it is preferably 4.4 V or less, more preferably 4.35 V or less. If the upper limit voltage is too small, the discharge capacity cannot be expected to be improved, and if the upper limit voltage is too high, the electrolytic solution is decomposed, and as a result, the cycle life tends to be shortened.

The lower limit voltage in charging and discharging is not particularly limited, but is usually 2.7 V or higher, preferably 2.75 V or higher, and usually 3.2 V or lower, preferably 3.1 V or lower, more preferably 3.0 V or lower. is there. If the lower limit voltage is too low, the crystal structure of the positive electrode active material may become unstable, and if the lower limit voltage is too high, the capacity of the lithium ion secondary battery may be reduced.

The discharging method is not particularly limited, and a constant voltage discharge, a constant current discharge or a charging method combining these can be adopted.

[0038]

The present invention will be described in more detail below, but the present invention is not limited to the following examples unless it exceeds the gist. (Creation of positive electrode) Lithium transition metal composite oxide shown in Table 1 as a positive electrode active material, electrified black (acetylene black manufactured by Denki Kagaku) as a conductive material, and polytetrafluoroethylene powder (PTFE) as a binder in a weight ratio. 7
It was weighed at a ratio of 5: 20: 5, sufficiently mixed, and formed into a sheet. This sheet having a diameter of 12 mm and a total weight of about 18 mg was adjusted, and then subjected to pressure bonding to an expanded metal of aluminum having a diameter of 16 mm to obtain a positive electrode (1).

(Measurement of Capacity of Positive Electrode) The battery capacity of the positive electrode active material was measured by preparing a coin battery. The positive electrode sheet was punched out into 9φ and the total weight was about 8 mg (active material amount Mg).
It adjusted so that it might become, and was pressure-bonded to the expanded metal of Al, and it was set as the positive electrode (2). Place the positive electrode (2) on the positive electrode can,
A 25 μm porous polyethylene film was placed on top of it and pressed with a polypropylene gasket, and then the negative electrode was 0.5 mm thick and 12 mmφ metal Li.
And a spacer for adjusting the thickness are placed, and then ethylene carbonate (EC) and diethyl carbonate (DEC) in which 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) is dissolved as a non-aqueous electrolyte solution. After using this mixed solvent of No. 1 and adding it to the inside of the battery to allow it to sufficiently permeate, the battery with the negative electrode can was sealed. The coin-type battery created is
The charge / discharge capacity was measured at a constant current of ² mA / cm ² . At this time, the upper limit voltage (II) V is set to 0.1 V lower than the upper limit value (upper limit voltage (I) V) in the lithium ion secondary battery including the positive electrode and the carbonaceous negative electrode, and the lower limit voltage is 3.2 V. And For example, when the upper limit voltage (I) is 4.4 V in a lithium ion secondary battery, the upper limit voltage (I
I) is 4.3V. As a result of such measurement, the initial charge capacity of the positive electrode active material is Qc and the initial discharge capacity is Qd (mAh /
g). In addition, the measurement used the commercially available charging / discharging apparatus. (Preparation of negative electrode) Average particle size of negative electrode active material is about 8 to 12 μm
Polyvinylidene fluoride as a binder
(PVdF) was weighed in a ratio of 92.5: 7.5 by weight, and this was mixed in an N-methylpyrrolidone (NMP) solution to prepare a negative electrode mixture slurry. This slurry is applied to one side of a copper foil having a thickness of 20 μm, dried, and the solvent is evaporated.
Negative electrode (1) was obtained by punching into φ and pressing.

Using this negative electrode as a test electrode and Li metal as a counter electrode, a coin-type battery was assembled in the same manner as in the case of measuring the capacity of the composite oxide, and Li ions were inserted into the negative electrode at a sufficiently low current amount ( The initial insertion capacity at the time of performing a test of lower limit 0 V) and desorption (upper limit 1.5 V) was set to Q (F) mAh / g. (Assembly of Ion Cell Coin Type Battery) The battery performance was evaluated using a coin type cell. That is, the positive electrode (1) was placed on the positive electrode can, the porous polyethylene film of 25 μm was placed thereon, and the polypropylene gasket was pressed, then the negative electrode (1) was placed and the spacer for thickness adjustment was placed. Then, as a non-aqueous electrolyte solution, 1 mol /
Using a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in which 1 liter of lithium hexafluorophosphate (LiPF ₆ ) was dissolved, add this to the inside of the battery and allow it to sufficiently soak, and then place the negative electrode can on it. The battery was sealed.

At this time, since the cell balance was 1.2, the weight of the positive electrode active material and the weight of the negative electrode active material were calculated by the following mathematical formula (1) and set to be almost calculated values.

[0042]

[Equation 1] Amount of negative electrode active material [g] * Q (F) / amount of positive electrode active material [g] * Qc = 1.2 Formula (1) (Test method: high temperature cycle test) 25 coin type ion cells prepared as described above The upper limit voltage (I) is set as shown in Table 1 at 0 ° C., the lower limit voltage is set to 3.0 V, and 0.2
C-constant current charging / discharging was performed once, followed by 1C-constant current charging / discharging twice, and then 0.2 V was discharged at 3V. The atmosphere was further changed to 50 ° C., 0.2 C-constant current charge / discharge was repeated once, and then 1 C-constant current charge / discharge was repeated 100 times. 50 ° C atmosphere 1C-
Of the 100 times of constant current charging / discharging, Qd
The discharge capacity at the _1st and 100th times is Qd ₁₀₀ ,

[0043]

Was calculated by the following equation 2] cycle retention ratio = Qd ₁₀₀ / Qd ₁ * ₁₀₀ formula (2). The results are shown in Table-1. The 1-hour rate current value, that is, 1C, is a current value that can reach a fully charged state from the lower limit discharge state to the upper limit voltage in 1 hour when performing constant current charging. This time, the value Qd obtained by measuring the capacity of the positive electrode
Was calculated by the formula (3).

[0044]

## EQU00003 ## 1C [mA] = Qd (mAh / g) * amount of positive electrode active material M (g) Formula (3) (Examples 1 to 4 and Comparative Examples 1 to 4) Lithium composite oxides shown in Table-1 Was used as a positive electrode active material to prepare a coin-type ion cell. A high temperature cycle test of this battery was conducted at the upper limit voltage shown in Table-1. Table 1 shows the high temperature cycle retention rate.

[0045]

[Table 1]

[0046]

According to the present invention, it is possible to supply a lithium ion secondary battery having an improved energy density and excellent cycle life.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5H029 AJ03 AJ05 AK03 AL06 AL07                       AL08 AL18 AM03 AM04 AM05                       AM07 CJ08 CJ16 DJ16 DJ17                       HJ02 HJ18                 5H030 AA01 AS20 BB01                 5H050 AA07 AA08 BA17 CA08 CA09                       CB07 CB08 CB09 CB29 GA10                       GA18 HA02 HA18

Claims (4)

[Claims] 1. A lithium ion secondary battery comprising a positive electrode containing a lithium transition metal composite oxide and a negative electrode containing a carbon material, wherein the lithium transition metal composite oxide has the following general formula (1): Represented and upper limit voltage 4.
Lithium-ion secondary battery characterized by being used at 15 to 4.4 V. embedded image Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) (where X is 0 <X ≦ 1 .2, Y and Z are 0.7 ≦ Y /
It represents a number satisfying the relationship of Z ≦ 9 and 0 ≦ (1−Y−Z) ≦ 0.5, and Q is a transition metal of the fourth period, B, Al,
It represents at least one element selected from Ga, Zn, Be, Mg and Ca. ) 2. A lithium ion secondary battery comprising a positive electrode containing a lithium transition metal composite oxide and a negative electrode containing a carbon material, wherein the lithium transition metal composite oxide has the following general formula (1): Represented and voltage 4.15
Li-ion secondary battery characterized by being charged to up to 4.4 V. embedded image Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) (where X is 0 <X ≦ 1.2, Y and Z are 0.7 ≦ Y /
It represents a number satisfying the relationship of Z ≦ 9 and 0 ≦ (1−Y−Z) ≦ 0.5, and Q is a transition metal of the fourth period, B, Al,
It represents at least one element selected from Ga, Zn, Be, Mg and Ca. ) 3. The element Q is Co, B, Al, V, Cr,
The lithium ion secondary battery according to claim 1 or 2, which is at least one metal element selected from the group consisting of Fe and Fe. 4. In a charging method for a lithium ion secondary battery containing a positive electrode containing a lithium transition metal composite oxide and a negative electrode containing a carbon material, the lithium transition metal composite oxide is represented by the following general formula ( Represented by 1),
In addition, a charging method for a lithium ion secondary battery is characterized in that charging is performed up to an upper limit voltage of 4.15 to 4.4V. Embedded image Li _X Ni _Y Mn _Z Q _(1-YZ) O ₂ (1) (where X is 0 <X ≦ 1.2, Y and Z are 0.7 ≦ Y /
It represents a number satisfying the relationship of Z ≦ 9 and 0 ≦ (1−Y−Z) ≦ 0.5, and Q is a transition metal of the fourth period, B, Al,
It represents at least one element selected from Ga, Zn, Be, Mg and Ca. )