JPH05283076A - Nonaqueous electrolyte secondary battery and manufacture of positive electrode active material thereof - Google Patents

Abstract

(57) [Summary] (Modified) [Constitution] The active material has the chemical formula Li _y Ni _1-x Me _x O.
₂ (wherein Me is any one of Ti, V, Mn, and Fe), and the number of moles of x and y is 0.2 <y.
≦ 1.3, when Me is Ti, V, or Fe, 0 <x <0.
5, when Me is Mn, 0 <x <0.6, has a hexagonal crystal structure, and has a lattice constant a identified from an X-ray diffraction pattern.
₀ is 2.83 to 2.89Å, c ₀ is 14.15 to 14.3
It is composed of a positive electrode having a volume of 1 Å, a negative electrode made of lithium, a lithium alloy or a carbon material in which lithium is intercalated, and a non-aqueous electrolyte. [Effect] A non-aqueous electrolyte secondary battery having excellent cycle characteristics can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a non-aqueous electrolyte secondary battery,
In particular, the present invention relates to improvement of a battery using a lithium composite oxide as a positive electrode active material.

[0002]

2. Description of the Related Art In recent years, portable and cordless AV devices or electronic devices such as personal computers have been rapidly developed, and there is a demand for a secondary battery having a small size, a light weight and a high energy density as a power source for driving these devices. high. From this point of view, non-aqueous secondary batteries, especially lithium secondary batteries, are particularly expected as batteries having high voltage and high energy density.

A layered compound capable of intercalating and deintercalating lithium as a positive electrode active material satisfying the above demand, for example, Li _1-x NiO ₂ (where 0 ≦ x <1) (US Pat. No. 4,302,518) Specification), Li _y Ni _2-y O ₂ (JP-A-2-40861) or Li _y Ni _x Co _1-x O ₂ (where 0 <x ≦ 0.
75, y ≦ 1) (Japanese Patent Laid-Open No. 63-299056), and other complex oxides mainly composed of lithium and a transition metal (hereinafter referred to as lithium complex oxides) have been proposed. In addition, A _x M _y N _z O ₂ (where A is an alcal metal, M is a transition metal, and N is at least one selected from Al, In, and Sn).
05 ≦ x ≦ 1.10, 0.85 ≦ y ≦ 1.00, 0.0
01 ≦ z ≦ 0.10) (JP-A-62-90863), Li _x M _y N _z O ₂ (where M is at least one transition metal and N is at least a non-transition metal). 0.05 ≤ x ≤ 1.10, 0.85 ≤ y ≤ 1.00 for one type,
There has been a proposal (Japanese Patent Laid-Open No. 4-22066) in which 0 ≦ z ≦ 0.10) is a main active material and a lithium / copper composite oxide is a secondary active material.

[0004] Then, the practical development of a high energy density secondary battery having a discharge voltage of 4 V class using these active material materials is under way.

[0005]

Here, Li _1-x NiO _{2 is used.}
(However, 0 ≦ x <1) (hereinafter referred to as LiNiO ₂ ) is
A secondary battery having a high energy density can be realized by showing a potential of 4 V or more with respect to lithium and using it as a positive electrode active material. However, its charge / discharge characteristic is 10 at the beginning of the cycle.
A discharge capacity of 0 mAh / g or more can be obtained, but the charge / discharge characteristics deteriorate with an increase in the number of cycles, and at 50 cycles the charge capacity decreases to 65% of the initial capacity, and good cycle characteristics cannot be obtained. was there.

[0006] In order to solve such a problem, in the composition represented by the above formula, nickel is used as a transition metal, and a part of the composition is replaced with a non-transition metal such as indium, ammonium or tin to synthesize a composite oxide. However, it has been proposed that by improving the positive electrode active material, excellent cycle characteristics as a battery can be obtained.

However, the lithium composite oxide obtained by substituting a part of nickel with the above elements tends to have a low discharge voltage, which results in the reduction of the originally desired characteristics of high voltage and high energy density. Become.

[0008]

In order to solve the above problems, the present invention provides a chemical formula Li _y Ni _1-x Me _x O ₂ (where Me is
Is one of Ti, V, Mn, and Fe), where x and y are in the number of moles of 0.2 <y ≦ 1.3, M
When e is Ti, V, Fe, 0 <x <0.5, Me is M
In the case of n, 0 <x <0.6, having a hexagonal crystal structure, and having a lattice constant a ₀ of 2.83 identified from an X-ray diffraction pattern.
Is 2.89Å, c ₀ is 14.15 to 14.31Å, and the range of y is 0.2 <y <1.0, Me
When Ti is V, Fe, 0 <x <0.5, when Me is Mn, 0 <x <0.6, and when 1.0 ≦ y ≦ 1.3, when Me is Ti, V, In the case of Fe, 0 <x <0.5, Me
When Mn is Mn, an active material material satisfying 0.01 ≦ x ≦ 0.4 is used for the positive electrode.

Particularly, in the chemical formula Li _y Ni _1-x Me _x O ₂ , Me is Mn and the number of moles of x and y is 1.0 ≦.
y ≦ 1.3, 0.01 ≦ x ≦ 0.4, the lattice constant a ₀ is 2.87 to 2.89Å, and the c ₀ is 14.15 to 14.
25 Å, which is indicated by the hexagonal Miller index (006)
Intensity ratio of diffraction peaks of plane (101) and plane (006)
Use of a positive electrode active material having a / (101) of 0.60 or less and a unit cell volume of 101 to 103 (Å ³ ) provides even better characteristics.

In the chemical formula Li _y Ni _1-x Me _x O ₂ , Me
Is Mn, and the number of moles of x and y is 1.0 ≦ y ≦
The above complex oxide represented by 1.3 and 0.01 ≦ x ≦ 0.4 is a manganese oxide or hydroxide corresponding to the number of atomic moles of Mn represented by x and an atom of Ni represented by 1-x. At least one nickel compound selected from the group of Ni (OH) ₂ , NiCO ₃ hydrate, and NiO corresponding to the number of moles, and 1.1 to 1.3 times the number of moles of Li atom represented by y At least one lithium compound selected from the group of corresponding LiNO ₃ hydrate, Li ₂ CO ₃ and Li ₂ O is used as a starting material, and the calcination temperature is 700 to 900 ° C. in an oxidizing atmosphere with air or oxygen. It is a composition.

The active material has a chemical formula Li _y Ni.
_{2 (1-x)} Me _2x O ₄ (wherein Me is any one of Ti, V, Mn, and Fe), and the number of moles of x and y is 0.2 <y ≦ 1. .0, and when Me is Ti or V, 0.
1 <x <0.5, 0.1 <x when Me is Mn or Fe
It has a cubic crystal structure with a spinel structure analog of <0.6 and a lattice constant a ₀ identified from an X-ray diffraction pattern is 8.1.
The active material of 5 to 8.30Å is used for the positive electrode.

It has been found that a non-aqueous electrolyte secondary battery having a high battery operating voltage and excellent cycle characteristics can be obtained by using such a positive electrode active material.

[0013]

[Function] The main cation species that determines the skeletal structure of LiNiO ₂ having a hexagonal system, Ni (trivalent), has a low-spin electronic structure configuration, and 7 electrons are present in its 3d level. It is housed. The electronic states of the 6th and 7th electrons of such an oxide are significantly different. That is, when one electron decreases from the 7th, the Fermi level drops to the lower orbits of the two large orbits that form the 3d level, and the electron conductivity due to the upper orbit, which was originally partially filled with electrons, decreases, By changing the occupied orbit itself,
The spin moment changes. As a result, the crystal field that influences the crystal structure changes, which makes it difficult to maintain the original hexagonal system of the basic skeleton. Therefore, when LiNiO ₂ is used as the positive electrode, there is a concern that the crystal structure gradually deteriorates and the depolarizing ability gradually decreases each time the oxidation reaction, that is, the charging operation is repeated during charging and discharging. This is considered to be one factor that hinders good cycle characteristics.

Further, when considering a spinel oxide LiNi ₂ O ₄ using Ni, for example, it is difficult to realize a higher oxide state having 6 electrons in the 3d level during the overcharge due to the above reason. Therefore, it is an extremely unstable substance and poor in practicality.

In the present invention, the transition metal Ti having a vacancy in the 3d level (having a valence of 4 valence electrons) and V (having a valence of 5 valence electrons)
By synthesizing Ni composite oxides containing Si, it is possible to hybridize with the vacant orbitals of lower energy levels formed by these transition metal oxides, and obtain a stable crystal field due to the exchange action during charging and cycle. It is intended to improve the characteristics. In addition, M having 3 to 4 electrons in the 3d level
n (formal valence number of electrons 4 to 3), or 5 to 6 F
By synthesizing a Ni composite oxide containing e (trivalent to divalent number of valence electrons), two orbitals of 3d level filled in the part of the transition metal oxide capable of these mixed valence states And the above-mentioned Ni (trivalent) orbital are hybridized with each other to improve the electronic conductivity by forming a band partially filled with both metal elements, and at the same time, a stable crystal field due to an exchange action during charging is obtained. Therefore, it is intended to improve the cycle characteristics.

The conventionally proposed non-transition metal containing Al has no d orbital, and Sn and In have been satisfied.
There are d levels. However, even if it is replaced with an element like the former, it is difficult to hybridize because the orbits are different, and even if it is replaced with an element having an electronic state with a higher energy level than the 3d level like the latter, it is high. The operating voltage cannot be expected, but the occupied band is Ti, which exists in the 3d level, like Ni,
It can be expected that V, Mn, and Fe will form a potential almost the same as the potential exhibited by the Ni oxide.

The composite oxide obtained by substituting a part of Ni with various transition metal elements forms a layered hexagonal system or a spinel-related cubic system having a lattice constant within a specific range. It is possible to synthesize them easily.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments with reference to the drawings.

Example 1 In the synthesis of Li _y Ni _1-x Me _x O ₂ (where Me is Ti, V, Mn or Fe), for example, Li ₂ O and NiO were substituted as main materials. When the transition metal element is Ti-based, it is TiO ₂ (rutile type), V-based is V ₂ O ₅ , Mn-based is MnO ₂ ,
In the case of Fe system, α or γ type Fe ₂ O ₃ is mixed in a predetermined composition ratio and then molded into tablets at 850 ° C.
And bake in air for 20 hours. This is crushed, washed with water, and then dried at 110 ° C. to obtain particles having an average particle size of 4 μm.

Next, Li _y Ni _{2 (1-x)} Me _2x O ₄ (where Me
In the synthesis of Ti, V, Mn, or Fe), for example, Li ₂ O and NiO as main materials and a Ti-based substitution transition metal element are TiO ₂ (rutile type),
In the case of V type, V ₂ O ₅ , in the case of Mn type, MnO ₂ and in the case of Fe type, α or γ type Fe ₂ O ₃ is mixed in a predetermined composition ratio and then formed into tablets. 20 at 800 ° C
Bake in air for hours. After crushing and washing with water, 1
Dry at 10 ° C. to obtain particles having an average particle size of 5 μm.

Among the obtained samples, y is 0.1, 1.
1 to 6 show the results of the lattice constants calculated from the X-ray diffraction patterns of the composite oxides having compositions corresponding to various x values when 0, 1.3, and 1.5.

As can be seen from FIGS. 1 to 4, Li _y Ni
The lattice constant of the hexagonal complex oxide represented by _1-x Me _x O ₂ (where Me is Ti, V, Mn, or Fe) is
a ₀ is 2.83 to 2.89, c ₀ is 14.15 to 14.3
1. Similarly, as can be seen from FIGS. 5 and 6, Li _y Ni
The lattice constant of the cubic complex oxide represented by _{2 (1-x)} Me _2x O ₄ (where Me is any one of Ti, V, Mn, and Fe) is such that a ₀ is 8.15 to 8. It became 30.

In order to select the optimum value of these positive electrode active materials, the potential width of the sample electrode was scanned to examine the voltage width which forms the peak current value of the cathode response current and the half value of the peak current waveform. The sample electrode had a positive electrode active material, acetylene black, and a fluororesin binder in a weight ratio of 7:
8 cm ^{2 of} the positive electrode mixture mixed to be 1.5: 1.5
Of the counter electrode, the reference electrode is another Li, and the electrolytic solution is ethylene carbonate and diethylene carbonate 1:
The solution was prepared by dissolving 1 mol / l of LiPF _{6 in} the mixed solvent of No. 1, and the scanning speed was 2 mV / s and the range was 3.1 V to 4.5 V.

The peak current value of the cathode response current corresponding to each x value when y is 1.0 is shown in FIGS.

As can be seen from FIG. 7, Li _y Ni _1-x Me _x
The hexagonal complex oxide represented by O ₂ (where Me is any of Ti, V, Mn, and Fe) is Ti, V, and Fe (0 <x <0.5), and Mn ( 0 <x <0.6) is good, but especially in the case of Mn (0.01 ≦ x ≦
0.4) results in a very good peak current value. On the other hand, Li _y Ni _{2 (1-x)} Me _2x O ₄ (where Me is T
The cubic complex oxide represented by any of i, V, Mn, and Fe) is Ti, V (0.1 <x <0.5) as shown in FIG. Case (0.1 <
When x <0.6), the peak current value was good.

Next, FIG. 9 shows the peak current values of the cathode response current for various y when x = 0.2 within the range of x values showing good characteristics in the hexagonal system.

As can be seen from FIG. 9, y is 0.2 to 1.5.
Shows a characteristic of 70 mA or more, especially 1.0 to
1.3 is the best. It is also good when y is 1.5, but since a tendency for excess Li that does not deposit in the reaction to remain in the positive electrode begins to appear, it is considered that the y value in this case should be 1.3. .. Further, the sample synthesized with y of 0.1 resulted in the cathode peak current value being halved. From this, the lower limit value of y is 0.2 and the upper limit value is 1.3.

Although not shown in the figure, the sample synthesized in the cubic system with y of 0.1 resulted in the cathode peak current value being halved. Also in this case, the lower limit of y is 0.2.
Is preferable, and it is difficult in terms of synthesis to dope Li in excess of 1.0. From these results, y is considered to be one of the optimum conditions (0.2 <y ≦ 1.0).

Next, the average value of the voltage range is shown in FIGS. From these figures, when the average value of the voltage width belongs to the range of the above-mentioned x value, the lower and upper limit values are 3.85V to 4.03V, which is valid as a positive electrode active material having a high voltage of about 4V.

From the above results, in the case of hexagonal system, y is (0.2 <y ≦ 1.3) under the optimum synthesis condition, and particularly when the substitutional transition metal element is Mn, 1.0 ≦ y ≦ 1. 3 is considered to be an even better condition. Further, the x, the lattice constant of crystals belonging to the limited range of y, the cathode peak current 2.89 from range 2.83 a ₀ in the result the mating of the measurement, c ₀ from 14.15 14. 31 and particularly when the substituting element is Mn, the range of a ₀ corresponding to the composition range of 0.01 ≦ x ≦ 0.4 is 2.87 to 2.89 and c _0.
Is from 14.15 to 14.25, and better characteristics can be obtained in this region.

On the other hand, in the case of cubic system, y is (0.2 <y
It is considered that ≦ 1.0) is the optimum synthesis condition. Also,
The lattice constant of the crystal belonging to the limited range of x and y is 8.15 to 8.30 in the range of a ₀ together with the result of the above-mentioned cathode peak current measurement, and good characteristics can be obtained in this region.

Next, in the hexagonal system, L, which had particularly good characteristics,
i _y Ni _1-x Me _x O ₂ (where x, y range 0.01 ≦ x ≦
The manufacturing method of 0.4, 1.0 ≦ y ≦ 1.3) will be described.

Example 2 Hexagonal system chemical formula Li _y Ni
_1-x Me _x O ₂ belongs to the space group R3m. Many researchers have examined the relationship between the crystal structure and the y value. For example, the relationship between the cell volume and the y value as a rhombohedral cell of a pure nickel hexagonal crystal having no substitution substance is described in J. B. Good Enough et al. (J.
Phys. Chem. Solids 5 (1958) 1
07) has an almost negative linear relationship. That is, the cell volume decreases as the y value increases. Also, J. R. Dern et al. (Solid S
Tate Ionics 44 (1990) 87) is the Miller index (1) identified from the X-ray diffraction pattern of this crystal structure.
The diffraction peak intensity ratio of the (006) plane to the (01) plane (hereinafter referred to as I) was calculated, and the following conclusions were drawn together with the results of Good Enough et al. That is, the I and rhombohedral cell volumes are positioned as increasing functions of each other, and conversely, the I and y values are expressed as negative functions. This is because I decreases as the y value increases. In the report, I at y = 1 is about 0.5.

From this, the diffraction peak intensity ratio I is positioned as an important crystal parameter showing the character of the crystal structure.

The inventors of the present invention have conducted extensive studies to find out the relationship between the reported results, the influence on the electrochemical properties, and the synthetic starting material.

For example, the synthesis method described in Example 1, that is, Li ₂ O and NiO as main materials and Mn as an additive substance
Adjust to a predetermined composition ratio using O ₂ as a starting material,
FIG. 12 shows the relationship between I and the cathode peak current value of the sample synthesized in the air atmosphere at 850 ° C. for 20 hours. As can be seen from the figure, the cathode peak current value decreases and becomes inactive as I increases. When I is 0.6 or less,
It can be seen that a current value of 80 mA or more is obtained and the device is in an active state.

Next, the relationship between I and the lattice constant is shown in FIG.
3, shown in FIG. As can be seen from the figure, the lattice constants a ₀ and c ₀ both rapidly increase as I increases. As shown in FIG. 12, when the cathode peak current value is 80 mA or more and I is 0.6 or less, the lattice constant is 2.87 <a ₀ <2.89, 14.1.
It was found to be within the range of 5 <c ₀ <14.25, and the electrochemical activity and the crystal parameters agreed with the range described in Example 1. That is, the synthesized composite oxide has a diffraction peak intensity ratio of (006) / (101) <
A sample satisfying 0.6 is electrochemically active and has a lattice constant of 2.87 <a ₀ <2.89, 14.1
Information is obtained that the range is 5 <c ₀ <14.25. As for the lower limit values of the lattice constants a ₀ and c ₀ , a ₀ is 2.
A sample showing 87 or less and c ₀ of 14.15 or less could not be obtained by synthesizing experimentally, and therefore it was determined based on this fact. The y value when I was 0.6 was found to be 1.02 as a result of chemical analysis.

Next, FIG. 15 shows the relationship between the unit cell volume of hexagonal crystals and the I value. The unit lattice volume was calculated based on the lattice constant. As a result, 101-103 (Å
^In the range of ³ ), the I value is 0.6 or less, and it can be expected to be electrochemically active.

The sample with a lattice volume of 101 or less could not be experimentally synthesized. Example 3 A manufacturing method for synthesizing a positive electrode active material having such crystal parameters will be specifically described.
Lithium compounds used as synthetic starting materials are Li ₂ O and Li ₂
O ₂ , Li ₂ CO ₃ , Li ₂ SO ₄ , LiNO ₃ hydrate, Li
I, Li (OH) hydrate, etc., and nickel compounds include NiO, Ni (NO ₃ ) ₂ , NiCO ₃ hydrate, N
i (OH) ₂ , NiSO ₄ , Ni (C ₂ H ₃ O ₃ ) ₂ hydrate, and the like. The manganese compound is MnO ₂ , αMn.
₂ O ₃ , γMnOOH and the like can be mentioned.

However, among the above lithium compounds, Li ₂
When O ₂ , LiI, and Li (OH) hydrate are used as starting materials, the lattice constant a ₀ is 2.89 or more and the I value is 0.6 or more, and a positive electrode active material having a target crystal structure is obtained. It was difficult to get.

Similarly, among the above nickel compounds, Ni
When (NO ₃ ) ₂ and NiSO ₄ are used as starting materials, the lattice constant a ₀ is 2.89 or more, and the I value is 0.6 or more.
After all, it was difficult to obtain a positive electrode active material having a desired crystal structure.

Example 4 Chemical formula Li _y Ni _1-x Mn _x O ₂
A method for synthesizing an active material having x and y of x = 0.01 and y = 1.0 as a basic composition will be described.

Table 1 shows the stoichiometric amount of L indicated by x and y.
It is a synthesis example when a lithium compound having an i atom mole number and a nickel compound having a stoichiometric amount of Ni atom mole number are used. The manganese compound used was manganese dioxide, and manganese dioxide having a stoichiometric amount of Mn atomic moles represented by the x value was used. In the synthesis, a predetermined amount of a lithium compound, manganese dioxide and a nickel compound are mixed and pressure-molded in a total pressure of 3 tons in units of 1 g to obtain tablets. This was treated in a combustion boat at a firing temperature of 850 ° C. for 20 hours in an air atmosphere. This is crushed, washed with water, and then dried at 110 ° C. to obtain particles having an average particle size of 4 μm.

[0044]

[Table 1]

Table 2 shows a synthesis example in which a lithium compound having a Li atom mole number 1.1 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number are used. Is.

[0046]

[Table 2]

Table 3 shows a synthesis example using a lithium compound having a Li atom mole number 1.3 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number. Is.

[0048]

[Table 3]

Table 4 shows a synthesis example using a lithium compound having a Li atom mole number 1.5 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number. Is.

[0050]

[Table 4]

From the above results, when the lithium compound to be added has a stoichiometric ratio, the I value is 0.60 or more, and good characteristics cannot be expected, but when the stoichiometric ratio is added 1.1 to 1.5 times. , I value is 0.6 or less, and good characteristics can be expected.

The details of the reason why Li must be added in a stoichiometric ratio or more are not clear at present, but it is speculated that it is due to the ease of thermal diffusion of Li. In the range of 1.1 times to 1.3 times, it is considered that the crystallinity is in the developing process and Li is dissolved in the solid phase. But,
At 1.3 times or more, almost no change was observed, and it became difficult for Li to form a solid solution in the solid phase. Also,
When 1.3 times or more of the lithium compound is added, a surplus of the lithium compound which is not deposited in the reaction when the electrode plate is formed remains and causes a corrosive effect on the positive electrode current collector, which is a problem. In addition, for example, when Li ₂ O and NiO are used as starting materials, the ratio is equal to the Li stoichiometric ratio, 1.1, 1.3, 1.5
As a result of analyzing the y value when doubled, 0.93,
It becomes 0.99, 1.08, 1.08, and it is necessary to add an excessive Li compound with respect to the stoichiometric amount.

From the viewpoint of such experimental results and quality control during production, it is desirable that the lithium compound to be added be 1.1 to 1.3 times the stoichiometric ratio.

Example 5 Chemical formula Li _y Ni _1-x Mn _x O ₂
A method of synthesizing an active material having x and y of x = 0.4 and y = 1.0 as a basic composition will be described.

Table 5 shows the stoichiometric amount of L indicated by x and y.
It is a synthesis example when a lithium compound having an i atom mole number and a nickel compound having a stoichiometric amount of Ni atom mole number are used. The other synthesis conditions are the same as in Example 4.

[0056]

[Table 5]

Table 6 shows a synthesis example in which a lithium compound having a Li atom mole number 1.1 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number are used. Is.

[0058]

[Table 6]

Table 7 shows a synthesis example in which a lithium compound having a Li atom mole number 1.3 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric Ni atom mole number are used. Is.

[0060]

[Table 7]

Table 8 shows a synthesis example in which a lithium compound having a Li atom mole number 1.5 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number are used. Is.

[0062]

[Table 8]

From the above results, as in Example 4 above, the lithium compound to be added is 1.1 to 1.
3 times is desirable.

Example 6 Chemical formula Li _y Ni _1-x Mn _x O ₂
A method of synthesizing an active material having x and y of x = 0.01 and y = 1.3 as a basic composition will be described.

(Table 9) shows the stoichiometric amount of L indicated by x and y.
It is a synthesis example when a lithium compound having an i atom mole number and a nickel compound having a stoichiometric amount of Ni atom mole number are used. The other synthesis conditions are the same as in Example 5.

[0066]

[Table 9]

Table 10 shows a synthesis example in which a lithium compound having a Li atom mole number 1.1 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric Ni atom mole number are used. Is.

[0068]

[Table 10]

Table 11 shows a synthesis example in which a lithium compound having a Li atom mole number 1.3 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number are used. Is.

[0070]

[Table 11]

Table 12 shows a synthesis example in which a lithium compound having a Li atom mole number 1.5 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number are used. Is.

[0072]

[Table 12]

From the above results, when y = 1.3, the lithium compound to be added has a good stoichiometric ratio, but is preferably 1.1 to 1.3 times.

Example 7 Chemical formula Li _y Ni _1-x Mn _x O ₂
A method of synthesizing an active material having x and y of x = 0.4 and y = 1.3 as a basic composition will be described.

Table 13 shows the stoichiometric amount of Li atom mole number of lithium compound and the stoichiometric amount of Ni.
It is a synthesis example when a nickel compound of atomic mole number is used. The other synthesis conditions are the same as in Example 5.

[0076]

[Table 13]

Table 14 shows a synthesis example in which a lithium compound having a Li atom mole number 1.1 times the stoichiometric amount shown by x and y and a nickel compound having a stoichiometric amount Ni atom mole number are used. Is.

[0078]

[Table 14]

Table 15 shows a synthesis example using a lithium compound having a Li atom mole number 1.3 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number. Is.

[0080]

[Table 15]

Table 16 shows a synthesis example in which a lithium compound having a Li atom mole number 1.5 times the stoichiometric amount represented by x and y and a nickel compound having a stoichiometric amount Ni atom mole number are used. Is.

[0082]

[Table 16]

From the above results, the lithium compound to be added may have the same stoichiometric ratio as in Example 6 above, but preferably 1.1 to 1.3 times.

As described in the above examples, the chemical formula L
In the synthesis of i _y Ni _1-x Mn _x O ₂ , x, y in the formula
The number of moles of 1.0 ≦ y ≦ 1.3, 0.01 ≦ x ≦ 0.4
And at least one selected from manganese dioxide corresponding to the number of atomic moles of Mn represented by x and a nickel compound corresponding to the number of atomic moles of Ni represented by 1-x, NiO, Ni (OH) ₂ , and NiCO _3. And 1.1 to 1.3 times L represented by y
Lithium compound, Li ₂ O, L corresponding to the number of moles of i atom
When at least one of iNO ₃ and Li ₂ CO ₃ is fired in air at 850 ° C. for 20 hours, the lattice constant a ₀ is 2.
87 to 2.89Å, c ₀ becomes 14.15 to 14.25Å, and a crystal parameter with an I value of 0.6 or less is obtained.

Two or three kinds of the above lithium or nickel compounds may be combined and used as a starting material for synthesis. Although not shown in Examples 4 to 7, Li ₂ SO ₄ as a lithium compound and Ni as a nickel compound were used.
(C ₂ H ₃ O ₂₎ the starting material and the same results using a _dihydrate is obtained.

However, in the former case, the generation of sulfur gas is thermally unstable in the latter case, so that it is not always good from the viewpoint of obtaining a positive electrode material having stable production or quality.

Although the firing temperature is 850 ° C. in this embodiment, the crystal half-width of the crystal is large and the crystallinity is low at 700 ° C. or less, so that the crystal structure of the active material is easily deteriorated during charging and discharging. This adversely affects the cycle characteristics of the battery. Moreover, since the diffusion of Li into the solid phase tends to be limited in the low temperature region, the Li doping amount cannot be sufficiently controlled.

On the contrary, at 900 ° C. or higher, there are few problems in the crystal structure, but since the crystal growth stabilizes at around 800 ° C., there is no point in raising the temperature too much. Therefore, it is desirable that the firing temperature be within the range of 700 to 900 ° C.

It is important that the firing is performed in an oxidizing atmosphere. When oxygen is insufficient, the number of Li ion trapping sites is reduced, so that the amount of Li doping into the crystal is reduced.
The value tends to increase. In such a state, it becomes difficult to obtain an electrochemically active active material. Therefore,
It is necessary to perform the firing treatment in an atmosphere in which oxygen deficiency can be avoided, and it is desirable to synthesize in an air or oxygen atmosphere.

Example 8 Next, a cylindrical battery was experimentally manufactured and evaluated in order to evaluate the cycle characteristics when the obtained positive electrode active material was used in a battery.

100 parts by weight of the above positive electrode active material, 4 parts by weight of acetylene black, 4 parts by weight of graphite, and 7 parts by weight of a fluororesin-based binder were mixed to form a positive electrode mixture, which was suspended in an aqueous carboxymethylcellulose solution to paste. Made into a shape. This paste was applied to both sides of an aluminum foil, dried and rolled to obtain an electrode plate.

The negative electrode is a carbon material 100 obtained by baking coke.
10 parts by weight of a fluororesin-based binder was mixed with parts by weight, and the mixture was suspended in an aqueous carboxymethylcellulose solution to form a paste. Then apply this paste to both sides of the copper foil,
After drying, it was rolled to obtain a negative electrode plate.

FIG. 16 is a vertical sectional view of a cylindrical battery constructed by using these electrode plates. The battery was constructed such that a lead was attached to each of the strip-shaped positive and negative electrode plates, spirally wound through a polypropylene separator, and housed in a battery case. As the electrolytic solution, a solution obtained by dissolving lithium perchlorate in a mixed solvent of equal volume of propylene carbonate and ethylene carbonate at a ratio of 1 mol / l was used, and a predetermined amount of this was injected and sealed to obtain a test battery.

In FIG. 16, 1 is a battery case made by processing an organic electrolytic solution resistant stainless steel plate, 2 is a sealing plate provided with a safety valve, and 3 is an insulating packing. Reference numeral 4 denotes an electrode plate group, in which a positive electrode plate and a negative electrode plate are spirally wound via a separator and housed in a case. A positive electrode lead 5 is drawn out from the positive electrode and connected to the sealing plate 2, and a negative electrode lead 6 is drawn out from the negative electrode and connected to the bottom of the battery case 1. Insulating rings 7 are provided on the upper and lower portions of the electrode plate group 4, respectively.

These test batteries were charged and discharged at a current of 100 m.
A constant current charge / discharge test was performed at room temperature up to 50 cycles under the conditions of A, end-of-charge voltage 4.1V, and end-of-discharge voltage 3.0V.

Among the positive electrode active materials, y is 1.0 and x is 0.
FIG. 17 shows the relationship between the discharge capacity per unit weight and the number of cycles when the positive electrode material corresponding to 2 was used. For comparison, a sample (LiNiO ₂ ) corresponding to y = 1.0 and x = 0
The result is shown by the solid line in the figure.

As can be seen from FIG. 17, a part of Ni is converted to T
The positive electrode active material substituted with any of the elements i, V, Mn, and Fe has a better discharge capacity than LiNiO ₂ from the initial cycle regardless of whether it is a hexagonal system or a cubic system. The result was good. Although not shown here, Li _y Ni _1-x Me _x O described above is used.
₂ (Me is any one of Ti, V, Mn, and Fe) and is a hexagonal complex oxide in which the number of moles of x and y is 0.2.
<Y ≦ 1.3, Ti, V, Fe (0 <x <0.
5), in the case of Mn (0 <x <0.6), Li _y N
i _{2 (1-x)} Me _2x O ₄ (Me is any one of Ti, V, Mn, and Fe) and is a cubic complex oxide, where x and y
When the number of moles of 0.2 <y ≤ 1.0 and Ti and V (0.
1 <x <0.5), in the case of Mn and Fe (0.1 <x <
Similar results were obtained using the positive electrode active material limited to 0.6).

[0098]

As is apparent from the above, according to the present invention,
For example, the positive electrode active material is Li_yNi_1-xMe _xO₂(Me is T
i, V, Mn, or Fe), and y is 0.
2 <y ≦ 1.3, x when Me is Ti, V, Fe
(0 <x <0.5), x in the case of Mn is 0 <x <0.6
And preferably y is 1.0 ≦ y ≦ 1.3, 0.01 ≦ x
≤0.4 or Li_yNi_{2 (1-x)}Me_2xO_Four(Me is T
i, V, Mn, or Fe), and y in the formula is 0.2
<Y ≦ 1.0, x is 0.1 <x when Me is Ti or V
<0.5, using 0.1 <x <0.6 for Mn and Fe
The non-aqueous electrolyte secondary battery with excellent cycle characteristics
You can get a pond.

[Brief description of drawings]

FIG. 1 is a diagram showing a lattice constant of a hexagonal system of Li _y Ni _1-x Me _x O _{2 in} which Me is Ti and V (when y = 0.1 and 1.0).

FIG. 2 is a diagram showing a lattice constant of a hexagonal system of Li _y Ni _1-x Me _x O _{2 in} which Me is Ti and V (when y = 1.3 and 1.5).

FIG. 3 is a diagram showing a lattice constant of a hexagonal system of Li _y Ni _1-x Me _x O _{2 in} which Me is Mn and Fe (when y = 0.1 and 1.0).

FIG. 4 is a diagram showing the lattice constant of a hexagonal system of Li _y Ni _1-x Me _x O ₂ where Me is Mn and Fe (when y = 1.3 and 1.5).

FIG. 5 is a diagram showing a lattice constant of a cubic system in which Li _y Ni _{2 (1-x)} Me _2x O ₄ and Me are Ti and V (when y = 0.1 and 1.0).

FIG. 6 is Li _y Ni _{2 (1-x)} Me _2x O ₄ where Me is Mn and Fe.
Showing the cubic lattice constants of (when y = 0.1, 1.0)

FIG. 7 is a diagram showing a cathode current peak value of Li _y Ni _1-x Me _x O ₂ .

FIG. 8 is a diagram showing a cathode current peak value of Li _y Ni _{2 (1-x)} Me _2x O ₄ .

FIG. 9 is a diagram showing a cathode current peak value of Li _y Ni _1-x Me _x O ₂ .

FIG. 10 is a diagram showing the average value of the voltage width of the cathode peak current.

FIG. 11 is a diagram showing an average value of voltage width of cathode peak current.

FIG. 12: Cathode peak current and diffraction peak intensity ratio I
The figure which shows the relationship of ((006) / (101))

FIG. 13 shows the lattice constant c ₀ and the diffraction peak intensity ratio I ((00
Diagram showing the relationship of 6) / (101))

FIG. 14 shows a lattice constant a ₀ and a diffraction peak intensity ratio I ((00
Diagram showing the relationship of 6) / (101))

FIG. 15: Unit cell volume of hexagonal crystal and diffraction peak intensity ratio I
The figure which shows the relationship of ((006) / (101))

FIG. 16 is a vertical sectional view of a cylindrical battery according to an embodiment of the present invention.

FIG. 17 is a diagram showing the relationship between discharge capacity and cycle characteristics.

[Explanation of symbols]

 1 Battery Case 2 Sealing Plate 3 Insulation Packing 4 Electrode Plate Group 5 Positive Electrode Lead 6 Negative Electrode Lead 7 Insulation Ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Okamura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. The active material has a chemical formula of Li _y Ni _1-x Me _x O _2.
(Wherein Me is any one of Ti, V, Mn, and Fe), and the number of moles of x and y is 0.2 <y ≦.
1.3, when Me is Ti, V, or Fe, 0 <x <0.
5, when Me is Mn, 0 <x <0.6, has a hexagonal crystal structure, and has a lattice constant a identified from an X-ray diffraction pattern.
₀ is 2.83 to 2.89Å, c ₀ is 14.15 to 14.3
A non-aqueous electrolyte secondary battery comprising a positive electrode of 1 Å, a negative electrode made of lithium, a lithium alloy or a carbon material in which lithium is intercalated, and a non-aqueous electrolyte. 2. The active material has a chemical formula of Li _y Ni _1-x Me _x O _2.
(However, Me is any one of Ti, V, Mn, and Fe), and the number of moles of x and y in the formula is 0.2 <y <
1.0, and when Me is Ti, V, or Fe, 0 <x <0.
5, when Me is Mn, 0 <x <0.6, has a hexagonal crystal structure, and has a lattice constant a identified from an X-ray diffraction pattern.
₀ is 2.83 to 2.88Å, c ₀ is 14.15 to 14.3
A non-aqueous electrolyte secondary battery comprising a positive electrode of 1 Å, a negative electrode made of lithium, a lithium alloy or a carbon material in which lithium is intercalated, and a non-aqueous electrolyte. 3. The active material has a chemical formula of Li _y Ni _1-x Me _x O _2.
(Wherein Me is any one of Ti, V, Mn, and Fe), and the number of moles of x and y is 1.0 ≦ y ≦
1.3, when Me is Ti, V, or Fe, 0 <x <0.
5, when Me is Mn, 0.01 ≦ x ≦ 0.4, having a hexagonal crystal structure, and having a lattice constant a ₀ identified from an X-ray diffraction pattern of 2.83 to 2.89Å, c ₀ is 14.15 to 1
A non-aqueous electrolyte secondary battery comprising a positive electrode of 4.31Å, a negative electrode made of lithium, a lithium alloy, or a carbon material in which lithium is intercalated, and a non-aqueous electrolyte. 4. The active material material has a chemical formula of Li _y Ni _1-x Me _x O _2.
, Me is Mn, and the lattice constant a ₀ is 2.87.
˜2.89Å, c ₀ is 14.15 to 14.25Å, and the intensity ratio of the diffraction peaks of the (006) plane and the (101) plane indicated by the hexagonal Miller index is (006) / (10
The nonaqueous electrolyte secondary battery according to claim 3, wherein a positive electrode having 1) of 0.60 or less is used. 5. The active material material has the chemical formula Li _y Ni _1-x Me _x O _2.
5. The non-aqueous electrolyte secondary battery according to claim 3, wherein Me is Mn and the positive electrode has a unit cell volume size of 101 to 103 (Å ³ ) indicated by hexagonal crystals. 6. The active material has a chemical formula of Li _y Ni _1-x Me _x O _2.
Where Me is Mn and the number of moles of x and y is 1.0 ≦
y ≦ 1.3, 0.01 ≦ x ≦ 0.4, wherein manganese oxide or hydroxide corresponding to the number of atomic moles of Mn represented by x and Ni represented by 1-x are represented. At least one nickel compound selected from the group consisting of Ni (OH) ₂ , NiCO ₃ hydrate, and NiO corresponding to the atomic mole number, and 1.1 to 1.3 times the Li atomic mole number represented by y Starting material is at least one lithium compound selected from the group consisting of LiNO ₃ hydrate, Li ₂ CO ₃ , and Li ₂ O, and is synthesized in an oxidizing atmosphere at a firing temperature of 700 to 900 ° C. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: 7. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 6, wherein the oxidizing atmosphere used in the synthesis of the positive electrode active material having the chemical formula Li _y Ni _1-x Mn _x O ₂ is air. Active material manufacturing method. 8. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 6, wherein the oxidizing atmosphere used in the synthesis of the positive electrode active material having the chemical formula Li _y Ni _1-x Mn _x O ₂ is oxygen. Active material manufacturing method. 9. The active material has a chemical formula of Li _y Ni _{2 (1-x)} Me.
_2x O ₄ (however, Me is Ti, V, Mn, or Fe)
And the number of moles of x and y is 0.2
<Y ≦ 1.0, when Me is Ti or V, 0.1 <x <
0.5, when Me is Mn and Fe, 0.1 <x <0.6
And has a cubic crystal structure similar to the spinel structure, and X
The lattice constant a ₀ identified from the line diffraction pattern is 8.15 to 8.
A non-aqueous electrolyte secondary battery comprising a positive electrode of 30Å, a negative electrode made of lithium, a lithium alloy or a carbon material in which lithium is intercalated, and a non-aqueous electrolyte.