JPH09266011A - Nonaqueous solvent secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous solvent secondary battery excellent in charge and discharge cycle characteristic with high capacity by setting the capacity ratio of positive electrode constant current charging capacity to negative electrode constant current charging capacity within a specified range. SOLUTION: In a nonaqueous solvent secondary battery, when a positive constant current charging capacity is Cc , and negative electrode constant current charging capacity is CA, the capacity ratio of positive electrode to negative electrode is set so as to have 0.85<=Cc /CA<=1.15. As the method of regulating Cc /CA within this range, regulation of thickness of positive and negative electrodes, regulation of conductivity of positive and negative electrodes or the like is given. In such a secondary battery, a carbon material containing amorphous carbon fiber and crystalline carbon fiber is preferably used as negative electrode active material. A lithium composite oxide is preferably used as positive electrode active material. The lithium composite oxide is selected from Lix CoO2 (0<=x<=1.0), Lix NiO2 , and those obtained by partially substituting these metal elements by an alkali earth metal element and a transition metal element.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a non-aqueous solvent secondary battery having a high capacity and excellent cycle characteristics.

[0002]

2. Description of the Related Art In recent years, with the widespread use of portable devices such as video cameras and notebook computers, demand for small and high capacity secondary batteries has increased. Most of the secondary batteries currently used are nickel-based using alkaline electrolyte.
The cadmium battery has a low battery voltage of about 1.2 V, and it is difficult to improve the energy density. Therefore, a lithium secondary battery using lithium metal, which has a specific gravity of 0.534, which is the lightest among solid solids, has a very low potential, and has the largest current capacity per unit weight among metal negative electrode materials, has been studied. .

However, in a secondary battery using lithium metal for the negative electrode, dendritic lithium (dendrites) is recrystallized on the surface of the negative electrode at the time of discharging, and grows by a charge / discharge cycle. This dendrite growth not only degrades the cycle characteristics of the secondary battery, but in the worst case, breaks through a separator (separator) arranged so that the positive electrode and the negative electrode do not come into contact with each other, and electrically short-circuits with the positive electrode. Ignite and destroy battery. Therefore, for example, as disclosed in JP-A-62-90863, a secondary battery is proposed in which a carbonaceous material such as coke is used as a negative electrode and alkali metal ions are doped and dedoped to repeat charging and discharging. Was done. As a result, it was found that the problem of deterioration of the negative electrode due to the repetition of charge and discharge as described above can be avoided. Further, such various carbonaceous materials can be used as a positive electrode by doping with an anion. As secondary batteries using electrodes based on the above-described principle of doping lithium ions or anions into carbonaceous materials, JP-A-57-20807, JP-A-58-93176, JP-A-58-93176, and -19
No. 2,266, Japanese Patent Application Laid-Open No. 62-90863, Japanese Patent Application Laid-Open No. 62-122066, Japanese Patent Application Laid-Open No. 3-66656, and the like are known.

The carbonaceous material may be used in any form such as powder, carbon fiber (long fiber or short fiber) or carbon fiber structure.

Further, recently, in order to meet the demand for higher energy density, a battery voltage of around 4V has appeared and has attracted attention. Increasing the battery voltage has been promoted by searching for and developing an active material exhibiting a high potential at the positive electrode, and inorganic compounds such as transition metal oxides and transition metal chalcogens containing alkali metals are known. Above all, Li _X C
oO ₂ (0 <x ≦ 1.0), Li _x NiO ₂ (0 <x ≦
1.0) are considered most promising in terms of high potential, stability, and long life. Among them, LiNi
Compared with LiCoO ₂ , the raw material of O ₂ is cheaper in cost, the supply is stable, and, although it is an active material of 4V class, the charging potential is somewhat lower, so that Research has been particularly vigorously pursued because of the advantage that decomposition is suppressed.

[0006]

However, the non-aqueous solvent-based secondary battery in which these negative electrode and positive electrode active materials are combined has a high discharge capacity at the initial stage, but the discharge capacity after repeated charging and discharging. However, there is a problem in that the cycle life characteristic is deteriorated.

The present invention is intended to solve the above-mentioned drawbacks of the prior art, and an object thereof is to provide a high-performance secondary battery having a high capacity and an excellent charge / discharge cycle.

[0008]

The present invention has the following constitution in order to solve the above problems. “When the positive electrode constant current charging capacity is C _C and the negative electrode constant current charging capacity is C _A , the positive and negative electrode capacity ratios are set so that 0.85 ≦ C _C / C _A ≦ 1.15. A non-aqueous solvent-based secondary battery characterized by the above. ”Here, as a result of examining the cause of the deterioration of the discharge capacity due to this charging / discharging cycle, the present invention has been found. That is, in general, these secondary batteries are charged with a constant current and then, when a certain voltage (potential difference between the negative electrode and the positive electrode) is reached, a constant current / constant current is maintained while decreasing the current value at that voltage. Take the voltage charging method. Generally, as a method of matching the positive and negative electrode capacities of batteries, a total capacity C _C ^t and C _A ^t, which is a combination of a constant current charging capacity and a constant voltage charging capacity, is prepared.
The constant current charge capacities C _C and C _A are adjusted.
Here, although C _C = C _A is obvious from the battery characteristics, the constant current charging capacities C _C and C _A in the present invention mean a unipolar constant current charging capacity. Since it is considered that C _C and C _A are affected by the areal weight of the electrode material, the internal resistance, etc., the method of adjusting C _C / C _A within the scope of the present invention is to adjust the thickness of the positive and negative electrodes, Adjustment of the conductivity of the positive and negative electrodes can be mentioned. As for
A method of changing the conductivity of the electrode active material and a method of changing the conductivity by devising a conductive agent or the like can be considered. Regarding the former, a method of adding various additives at the time of synthesis can be mentioned.
Regarding the latter, the kind and amount of the conductive agent may be mentioned.

FIG. 2 schematically illustrates the present invention. FIG. 2 exemplifies what occurs in the positive and negative electrodes when charged by the constant current / constant voltage charging method. For simplicity,
It was assumed that the positive and negative current decay curves after reaching a constant voltage were the same. When C _C / C _A is more than 1.0 (C
_C > C _A ), lithium ions move from the positive electrode to the negative electrode at a speed (amount of ions per unit time) at which the negative electrode can be intercalated, and the surplus lithium ions are converted to metallic lithium on the negative electrode surface. Are deposited (dendrites are generated), and as a result, the discharge capacity is deteriorated due to charge / discharge cycles. When C _C / C _{A is} exactly 1.0 (C _C = C _A ), during charging, lithium ions moving from the positive electrode to the negative electrode can be intercalated into the negative electrode without being deposited on the negative electrode surface. as a result,
The discharge capacity does not deteriorate due to charge / discharge cycles. C _C
When / C _A is smaller than 1.0 (C _C <C _A ), the utilization rate of the negative electrode active material is too small and the capacity of the battery becomes small. However, extensive studies were carried out the results, in fact, positive and such that _{0.85 ≦ C C / C A ≦} 1.15
It has been found that by setting the capacity ratio of the negative electrode, deterioration of the discharge capacity due to charge / discharge cycles is suppressed. C
Although _C / C _A reason is not clear with such a range, the actual current decay curves of the positive and negative electrode after reaching the constant voltage or different, or, can be tolerated without dendrite on the negative electrode surface It is thought that the cause may be that the amount of lithium ion has a range. More preferably, 0.90 ≦ C _C / C _A ≦ 1.05.

Next, a method of obtaining C _C and C _A will be described. For the negative electrode, if there is an initial capacity loss,
First, the initial capacity loss is eliminated by preliminary charging / discharging at a low current density, and then the battery is charged by a constant current / constant voltage charging method at a constant current density up to a predetermined charging potential V _A. The charge capacity until reaching the constant potential V _A at this time is the negative electrode constant current charge capacity C
_A. Similarly, in the case of the positive electrode, when there is an initial capacity loss, first the initial capacity loss is eliminated by preliminary charging / discharging at a low current density, and then a constant current / constant voltage charging method up to a predetermined charging potential V _C. Charge with. The charge capacity until reaching the constant potential V _C at this time was defined as the positive electrode constant current charge capacity C _C. The positive electrode active material used in the present invention is not particularly limited, and an inorganic compound such as a transition metal oxide containing an alkali metal or a transition metal chalcogen is used. Among them, Li _X CoO ₂ (0 <x ≦ 1.0), L
i _X NiO ₂ (0 <x ≦ 1.0) is considered to be the most promising in terms of high potential, stability, and long life.
Among them, LiNiO ₂ is cheaper in raw material and stable in supply than LiCoO ₂ , and it is a 4V class active material, but its charge potential is somewhat low. Therefore, it is preferably used in the present invention because of the advantage that the decomposition of the electrolytic solution is suppressed.
Furthermore, for example, as shown in Japanese Patent Application No. 6-275432, LiNiO ₂ in which a part of the metal elements is replaced with an alkaline earth metal element and / or a transition metal element,
It is preferably used.

As the negative electrode active material used in the present invention,
The material is not particularly limited, and for example, carbonaceous materials, metal sulfides, metal oxides, etc. are used. The carbonaceous material is not particularly limited, and generally, a material obtained by firing an organic substance is used. When an amorphous carbon material is used as the negative electrode active material, it is generally said that it has lower conductivity than the crystalline carbon material. In order to improve conductivity, it is effective to add a crystalline carbon material, but as a result of studies by the present inventors, in particular, a crystalline carbon powder in which granular and flake-like particles are mixed with amorphous carbon fiber is added. Then, it was found to be very effective. The ratio of crystalline carbon powder in the carbon material is
5 to 60 wt% is preferable, more preferably 20 to 45
wt%. Although the reason is not clear, it is considered that the crystalline carbon powder enters the gaps between the amorphous carbon fibers to improve the conductivity between the amorphous carbon fibers. The granular crystalline carbon powder alone is insufficient in binding property, and the flake crystalline carbon powder alone is difficult to uniformly disperse, and improvement in conductivity is insufficient. Further, when these crystalline carbon powders function as a negative electrode active material, when the crystalline carbon powders are mixed with the amorphous carbon fibers, the expansion / contraction of the crystalline carbon powders due to doping / dedoping of Li ions, It relaxes in the gap (the expansion / contraction of the amorphous carbon fiber itself due to the doping / de-doping of Li ions is small).

When the carbonaceous material is carbon fiber, the carbon fiber to be used is not particularly limited, and generally fired organic material is used. Specifically, P obtained from polyacrylonitrile (PAN)
AN-based carbon fiber, pitch-based carbon fiber obtained from pitch such as coal or petroleum, cellulose-based carbon fiber obtained from cellulose, vapor-grown carbon fiber obtained from gas of low-molecular-weight organic substances, and the like, Carbon fibers obtained by firing polyvinyl alcohol, lignin, polyvinyl chloride, polyamide, polyimide, phenolic resin, furfuryl alcohol, and the like may be used.
Among these carbon fibers, carbon fibers satisfying the characteristics are appropriately selected according to the characteristics of the electrode and the battery in which the carbon fibers are used. When the carbon fiber is used for a negative electrode of a secondary battery using a non-aqueous electrolyte containing an alkali metal salt, a PAN-based carbon fiber, a pitch-based carbon fiber, and a vapor-grown carbon fiber are preferable. In particular, PAN-based carbon fibers and pitch-based carbon fibers are preferable in that doping of alkali metal ions, particularly lithium ions, is favorable,
Among them, PAN-based carbon fibers such as “Torayca” T series or “Torayca” M series manufactured by Toray Industries,
Pitch-based carbon fibers obtained by firing mesophase pitch coke are more preferably used.

When the carbon fiber is used as an electrode, it may have any form, but a preferred form is to arrange it in a uniaxial direction, or to form a fabric-like or felt-like structure. Examples of the structure such as a fabric or a felt include a woven fabric, a knitted fabric, a braid, a lace, a net, a felt, a paper, a nonwoven fabric, a mat, and the like. Felt and the like are preferred. Further, the carbon fiber may be used by attaching it to a current collector such as a copper foil with a binder or the like, and a conductive agent such as carbon powder may be added. In view of operability and productivity, short fiber carbon fibers are more preferable. Like ordinary carbon powder, it can be used in the form of an electrode together with a conductive agent and a binder, and has structural characteristics unique to carbon fibers. An average length of 100 μm or less is more preferable because it is easy to handle and high bulk density can be achieved. The electrolytic solution of the secondary battery using the electrode of the present invention is not particularly limited, and a conventional non-aqueous solvent-based electrolytic solution is used. Among them, as the electrolytic solution of the secondary battery composed of the above-mentioned non-aqueous electrolytic solution containing an alkali metal salt, propylene carbonate, ethylene carbonate, γ-butyrolactone, N-methylpyrrolidone, acetonitrile, N, N-dimethylformamide,
Dimethyl sulfoxide, tetrahydrofuran, 1,3
-Dioxolane, methyl formate, sulfolane, oxazolidone, thionyl chloride, 1,2-dimethoxyethane, diethylene carbonate and derivatives and mixtures thereof are preferably used. The electrolyte contained in the electrolytic solution is an alkali metal, particularly a lithium halide, perchlorate, thiocyanate, borofluoride, phosphorofluoride,
Arsenic fluoride, aluminum fluoride, trifluoromethyl sulfate, etc. are preferably used.

The secondary battery using the electrode of the present invention is lightweight, has a high capacity and high energy density, and can be used in a portable small size such as a video camera, a laptop computer, a word processor, a radio-cassette or a mobile phone. It can be widely used for electronic devices.

[0015]

EXAMPLES Specific embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 Commercially available high-purity reagent lithium hydroxide (Li (OH)),
Cobalt hydroxide (Co (OH) ₂ ), L in terms of oxide
i _0.98 CoO ₂ and weighed well in an automatic mortar, filled into an alumina crucible, and air-flowed (flow rate 1 liter / min) using an atmosphere firing furnace.
It was kept at 0 ° C. for 6 hours and prebaked. After cooling to room temperature, the mixture was pulverized again in an automatic mortar for 30 minutes to break up aggregation of secondary particles. Then, under the same atmosphere as the preliminary firing, 85
After maintaining at 0 ° C. for 12 hours for main calcination, cooling to room temperature, crushing again in an automatic mortar for 1 hour to obtain a positive electrode active material powder of the present invention. The positive electrode mixture was prepared by adding N-methylpyrrolidone (NMP) solution prepared by mixing polyvinylidene fluoride active material, which is a binder, in an amount of 10 wt% to the above active material: conductive agent (acetylene black): binder. Parts by weight: 4 parts by weight: 7 parts by weight, and the mixture was prepared in an automatic mortar for 30 minutes in a nitrogen stream. This is applied on an aluminum foil having a thickness of 20 μm, dried in a dryer at 90 ° C., then applied on the back side, dried at 200 ° C. to form positive electrodes on both sides, and then pressed to obtain four types of positive electrode sheets. It was made.

Next, a commercially available short fibrous PAN-based carbon fiber ("MLD-30", manufactured by Toray Industries, Inc .; average fiber length of about 30).
μm; d ₍₀₀₂₎ : 0.35 nm, L _C : 1.4 nm)), and the active material: conductive agent (acetylene black): binder was 89 parts by weight: 4 parts by weight: 7 parts by weight. A negative electrode sheet was prepared in the same manner as the positive electrode except that it was mixed as described above.
At this time, the capacity ratio C _C / C _A of the positive and negative electrodes is set to 0 by combining positive and negative electrode sheets having different thicknesses.
It was set to 85, 1.00 and 1.15. The thicknesses of the positive electrode and the negative electrode are as shown in Table 2. Here, as the positive electrode constant current charging capacity C _C and the negative electrode constant current charging capacity C _A , a sample cut out in strips from each of the positive and negative electrode sheets was used, and a triode glass cell using metallic lithium for the counter electrode and the reference electrode. Was measured using. As an electrolyte, propylene carbonate and dimethyl carbonate (each at a volume ratio of 1: 1) containing 1M LiPF ₆ were used. In the case of the negative electrode, since the carbon material used in this example has an initial capacity loss, first, in order to eliminate the initial capacity loss, at a current density of 0.02 A / g (per weight of the negative electrode active material), the charging potential was 0 V. It was charged for 48 hours by the constant current / constant voltage charging method of (VSLi ⁺ / Li). 0.0 after charging
1.5 V at constant current of 2 A / g (per weight of negative electrode active material)
It was discharged to (VSLi ⁺ / Li). Next, the current density 0.2
A / g (per weight of negative electrode active material), charging potential 0 V (VS
It was charged for 2 hours by the constant current / constant voltage charging method of Li ⁺ / Li). After charging, the battery was discharged to 1.5 V (VSLi ⁺ / Li) at a constant current of 0.14 A / g (per weight of negative electrode active material). The charge capacity until reaching the constant potential (0 V) at this time was defined as the negative electrode constant current charge capacity C _A. Similarly, in the case of the positive electrode, first, the battery was charged at a current density of 0.02 A / g (per weight of the positive electrode active material) for 10 hours by a constant current / constant voltage charging method with a charging potential of 4.3 V (VSLi ⁺ / Li). After charging, the battery was discharged to 3.0 V (VSLi ⁺ / Li) at a constant current of 0.02 A / g (per weight of positive electrode active material). Next, the battery was charged at a current density of 0.1 A / g (per weight of the positive electrode active material) for 2 hours by a constant current / constant voltage charging method with a charging potential of 4.3 V (VSLi ⁺ / Li). After charging 0.
3.0 at a constant current of 07 A / g (per weight of negative electrode active material)
It was discharged to V (VSLi ⁺ / Li). The charge capacity until reaching the constant potential (4.3 V) at this time was defined as the positive electrode constant current charge capacity C _C.

A metal can secondary battery of 18650 size was produced by using these positive and negative electrode sheets and a separator of microporous polyethylene film (manufactured by Mitsubishi Chemical Corporation). As an electrolyte, propylene carbonate and dimethyl carbonate (each at a volume ratio of 1: 1) containing 1M LiPF ₆ were used. Using the secondary battery produced in this manner, charging was performed by a constant current / constant voltage charging method with a current density of 1 A and a charging potential of 4.2 V. After charging, the battery was discharged to 2.75 V with a constant current of 0.7 A. This charging / discharging is repeated 500 times, and the result of the ratio of the 5th discharge capacity (battery capacity), the 5th discharge capacity and the 500th discharge capacity (capacity retention rate: shown by the following formula) is the positive / negative capacity ratio. It is shown in Table 1 together with C _C / C _A.

Capacity retention rate (%) = {(500th discharge capacity) / (5th discharge capacity)} × 100 Comparative Example 1 Positive and negative electrode capacity ratios C _C / C _A of 0.7 and 1. A secondary battery was made in the same manner as in Example 1 except that the setting was 3. Battery capacity, together with the capacitance ratio C _C / C _A of the results of capacity retention positive and negative electrodes shown in Table 1.

Example 2 Nickel hydroxide (Ni (OH) ₂ ) was used instead of cobalt hydroxide (Co (OH) ₂ ), and Li was calculated as oxide.
Weighed so as to be _0.98 NiCoO _2, and prebaked conditions 6
00 ° C. for 10 hours, main firing conditions of 750 ° C. for 6 hours,
A positive electrode sheet was prepared in the same manner as in Example 1 except that it was baked in dry air. When determining the positive electrode constant current charging capacity C _C , the positive / negative electrode capacity ratio C _C / C _A is set to 1.0 in the same manner as in Example 1 except that the charging potential is set to 4.2V. Was produced. Battery capacity, together with the capacitance ratio C _C / C _A of the results of capacity retention positive and negative electrodes shown in Table 1.

Comparative Example 2 _A secondary battery was made in the same manner as in Example 2 except that the positive and negative electrode capacity ratio C _C / C _A was weighed to be 1.3.
The results of battery capacity and capacity retention ratio are the positive / negative capacity ratio C _C /
It is shown in Table 1 together with C _A.

Example 3 Lithium hydroxide (Li (OH)), nickel hydroxide (N
i (OH) ₂ ), strontium hydroxide octahydrate (Sr
_{(OH) 2 · 8H 2 O} ), cobalt hydroxide (Co (O
H) ₂ ) in terms of oxide, Li _0.98 Sr _0.002 Ni _0.90 C
A positive electrode sheet was produced in the same manner as in Example 1 except that the weight was adjusted to _0.10 O ₂ . Then, to prepare a secondary battery to set the volume ratio C _C / C _A positive and negative electrodes in the same manner as in Example 2 as 1.0. Battery capacity, Table 1 together with the capacitance ratio C _C / C _A positive and negative results of capacity retention rate
It was shown to.

Comparative Example 3 _A secondary battery was manufactured in the same manner as in Example 3 except that the positive and negative electrode capacity ratio C _C / C _A was weighed to be 1.3.
The results of battery capacity and capacity retention ratio are the positive / negative capacity ratio C _C /
It is shown in Table 1 together with C _A.

Example 4 Negative electrode MLD-30 had 30 wt% artificial graphite (d (002):
0.37 nm, L _C : 80 nm) was added, and a secondary battery was prepared in the same manner as in Example 3 except that the positive / negative electrode capacity ratio C _C / C _A was set to 1.0. Here, when the morphology of the artificial graphite was observed using a scanning electron microscope, it was confirmed that a mixture of particles and flakes was mixed. Battery capacity, together with the capacitance ratio C _C / C _A of the results of capacity retention positive and negative electrodes shown in Table 1.

Comparative Example 4 _A secondary battery was prepared in the same manner as in Example 4 except that the positive and negative electrode capacity ratios C _C / C _A were weighed to be 1.3.
The results of battery capacity and capacity retention ratio are the positive / negative capacity ratio C _C /
It is shown in Table 1 together with C _A.

From Table 1 showing the results of Examples 1 to 4 and Comparative Examples 1 to 4 and FIG. 1 showing the results of Example 1 and Comparative Example 1, the capacity ratio C _C / C _{A of the} positive and negative electrodes is shown. 0.85 ≦ C _C
It can be seen that when / C _A ≦ 1.15, the cycle life characteristics of the high capacity secondary battery are good.

[0027]

[Table 1]

[Table 2]

[0028]

According to the present invention, it is possible to provide a positive electrode active material having a high capacity and an excellent charge / discharge cycle and a high-performance secondary battery using the same.

[Brief description of drawings]

FIG. 1 is a capacity retention ratio (%) in Example 1 and Comparative Example 1.
And is a diagram showing the relationship of _C C / C _A.

[Fig. 2] Positive when charging by constant current / constant voltage charging method
It is the drawing which illustrated what happens at the negative electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Matsuda 1-1-1, Sonoyama, Otsu City, Shiga Toray Co., Ltd. Shiga Plant

Claims (12)

[Claims] 1. When the positive electrode constant current charging capacity is C _C and the negative electrode constant current charging capacity is C _A , 0.85 ≦ C _C / C _A ≦ 1.
A non-aqueous solvent-based secondary battery, wherein the capacity ratio of the positive and negative electrodes is set to be 15. 2. The non-aqueous solvent secondary battery according to claim 1, wherein 0.90 ≦ C _C / C _A ≦ 1.05. 3. The non-aqueous solvent secondary battery according to claim 1, wherein a carbonaceous material is used as the negative electrode active material. 4. The non-aqueous solvent secondary battery according to claim 3, wherein the carbonaceous material contains carbon fibers. 5. The non-aqueous solvent secondary battery according to claim 4, wherein the carbon fibers are short fibers having an average length of 100 μm or less. 6. The non-aqueous solvent-based secondary battery according to claim 3, wherein the carbonaceous material contains amorphous carbon fiber and crystalline carbon powder. 7. The amorphous carbon fiber has an interplanar distance d ₍₀₀₂₎ of (002) plane of 0.35 nm or more and 0.38 nm or less and a crystallite size L _C in the c-axis direction of 1.0 nm. Or more and 2.0 nm or less, and the inter-plane distance d (00
2) 0.34 nm or less, the crystallite size L in the c-axis direction
The non-aqueous solvent secondary battery according to claim 6, wherein _C is 0.40 nm or more and 1.0 nm or less. 8. The non-aqueous solvent secondary battery according to claim 6 or 7, wherein the crystalline carbon powder has a granular or flake shape. 9. The non-aqueous solvent secondary system according to claim 6, wherein the ratio of the crystalline carbon powder in the carbonaceous material is 5 wt% or more and 60 wt% or less. battery. 10. The non-aqueous solvent secondary battery according to claim 9, wherein the ratio of the crystalline carbon powder in the carbonaceous material is 20 wt% or more and 45 wt% or less. 11. The non-aqueous solvent secondary battery according to claim 1, wherein a lithium composite oxide is used as the positive electrode active material. 12. The lithium composite oxide is Li _X CoO.
₂ (0 <x ≦ 1.0), Li _X NiO ₂ (0 <x ≦ 1.
12. The non-aqueous solvent-based secondary battery according to claim 11, which is selected from 0) and those obtained by substituting a part of these metal elements with an alkaline earth metal element and / or a transition metal element.