JPH09134723A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery which has a large discharge capacity to well sustain practical use by eliminating uncontinuousness of voltage over two discharge regions. SOLUTION: A secondary battery concerned uses a positive electrode active material as a substance chiefly containing complex oxide of manganese which contains alkali metal (A) and is expressed by AyMn2-x MxO4 , where A is alkali metal, M is a metal other than A and Mn, and x and y are conditioned as 0.5<x<1.5 and 0<y<2, while the negative electrode active material consists of a conventional substance. Further the battery includes an electrolyte of a substance which permits ions of the used alkali metal to make movement for generating electrochemical reactions with the positive or negative electrode active material. A-compound, Mn compound, and M compound are mixed together and subjected to a heat treatment, and synthetization is made by rapidly cooling the random spinel type or inverted spinel type structure so that a compound according to the above expression is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery, and more particularly to a chargeable / dischargeable non-aqueous electrolyte secondary battery, and particularly to the improvement of the positive electrode active material, aiming to increase the charge / discharge capacity of the battery. Is.

[0002]

2. Description of the Related Art A non-aqueous electrolyte battery using an alkali metal such as lithium or an alloy or compound thereof as a negative electrode active material has a large discharge capacity due to an insertion or intercalation reaction of a negative electrode metal ion into the positive electrode active material. Charge reversibility is compatible. Conventionally, as a secondary battery using lithium as a negative electrode active material, a battery using a layered or tunnel oxide such as vanadium pentoxide or manganese dioxide, which can be an intercalation host for lithium, has been proposed. However, the voltage flatness was poor and the charge / discharge energy density was not sufficient. In recent years, cubic LiMn ₂ having a spinel structure
It has been reported that the battery can be discharged at 4V if it is initially charged to about 4.5V with O ₄ , and then discharged, and it is promising as a high-voltage positive electrode [J. , First
37, No. 3, p. 769 (1990)]. But,
In this 4V region, Li / Mn ₂ O ₄ > 1 due to the progress of discharge.
When the above composition range is reached, the discharge voltage drops sharply to 3 V or less in response to the lithium insertion site shifting from the tetrahedron 8a site to the octahedron 16c site. Li
Mn ₂ O ₄ has a high-voltage region of 4 V, a low-voltage region of 3 V, and a total discharge capacity of 1 V when the two regions are combined, which is about 300 mA.
It has a large discharge capacity close to h / g, but the discharge voltage between the 4V high voltage region and the 3V low voltage region has a large discontinuity of 1V or more, which makes it difficult to cycle in a voltage range that crosses both regions. In addition, it is difficult to use both areas.

[0003]

SUMMARY OF THE INVENTION The present invention is directed to LiMn ₂
The discharge voltage in the 4 V region of O ₄ is intentionally lowered by substitution and addition of a metal element other than Mn to eliminate the voltage discontinuity between the two discharge regions, and a practical large discharge capacity non-aqueous electrolyte secondary battery To provide.

[0004]

The present invention will be outlined. The first invention of the present invention relates to a non-aqueous electrolyte secondary battery, which has a composition formula: A _y Mn _2-x M _x O ₄ ( A is an alkali metal, M is a metal other than A and Mn, 0.5 <x <1.
5, 0 <y <2) containing as a positive electrode active material a substance mainly composed of an alkali metal (A) -containing manganese mixed oxide, an alkali metal, an alkaline earth metal, or an alkali metal or an alkaline earth metal A substance capable of occluding and releasing ions is used as a negative electrode active material, and a substance capable of moving ions of the alkali metal to cause an electrochemical reaction with the positive electrode active material or the negative electrode active material is used as an electrolyte substance. And A second invention of the present invention is the alkali metal (A) -containing manganese mixed oxide according to the first invention,
An invention relates to a method for producing a _{A y Mn 2-x M x} O 4, alkali metal compound, manganese compound, and the compound substituted additive metal (M) onto the mixed, after heat treatment, the random spinel or inverse spinel It is characterized in that the structure is synthesized by quenching.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. Generally, spinel compounds have a composition formula of AB ₂ O ₄ . The difference between the spinel structure and the reverse spinel structure is whether or not the A ion occupies the octahedral site. The positive electrode active material of the present invention, Li _y Mn _2-x M _x O _4, contains about half (25 to 75%) of Mn located at the octahedral site in the manganese spinel oxide, LiMn ₂ O ₄ , as another element M. Is a ternary oxide substituted and added, and more preferably Li _y Mn
_2-x M _x O ₄ is used to form the dopant M is
It is an ion having a smaller octahedral site preference energy than Li ⁺ . Since such ions are more energetically stable in occupying the tetrahedral site than in the octahedral site, this substitution addition changes the occupied site of Li from the tetrahedral site to the octahedral site in exchange for the dopant M. Become. Corresponding to the fact that the occupied site of Li is no longer a tetrahedral site, 4M of LiMn _2-x M _x O ₄
Although the discharge area is reduced, the low voltage area is increased instead, and a highly practical non-aqueous electrolyte battery with a small discharge voltage difference and high practicality can be obtained. As described above, the positive electrode active material in the present invention is expressed as | Li _1-x M _x | [Li _x Mn _2-x ] O ₄ (where || is a tetrahedral site, [ ] Indicates an octahedral site), but examples of such a dopant M include Fe, Ru, Os, Ti, Zr, Hf, and N.
b, Ta, Cr, Mo, W, Co, Rh, Ir, Ni,
One or more of Sb, Si, Ge, Sn, Pb and the like can be mentioned. Further, x is preferably in the range of 0.25 <x <0.75. This is because if the doping amount is small, the substitution of Li on the tetrahedral site is insufficient, and if it is too large, many other phases may be formed. Particularly preferably,
It is around x = 1. The rapid cooling for obtaining the random spinel phase, which is a high temperature metastable phase of the positive electrode active material, was taken out of the furnace immediately after firing and water-cooled from the outside of the platinum crucible so as not to splash water on the sample. Not limited to this method, forced air cooling or spray dry method,
A roll quenching method or the like is also possible. In order to form a positive electrode using this positive electrode active material, a mixture of the compound powder and a binder powder such as polytetrafluoroethylene is pressure-molded on a support such as stainless steel, or the mixture powder is electrically conductive. To provide a conductive powder such as acetylene black, to which is added a binder powder such as polytetrafluoroethylene, if necessary, and this mixture is placed in a metal container, or the above mixture is added. It is formed by means such as press-molding on a support such as stainless steel, or by dispersing the above mixture in a solvent such as an organic solvent to form a slurry and coating it on a metal substrate.

Lithium, which is the negative electrode active material, is formed into a sheet in the same manner as that of a general lithium battery, and the sheet is pressure-bonded to a conductor network of nickel, stainless steel or the like to form a negative electrode. Further, as the negative electrode active material, in addition to lithium, lithium alloys and lithium compounds, other conventionally known alkali metals such as sodium, potassium and magnesium, alkaline earth metals, or alkali metals or alkaline earth metal ions can be occluded and released. Materials such as alloys of the above metals, carbon materials and the like can be used. Examples of the electrolytic solution include dimethoxyethane, 2-methyltetrahydrofuran, ethylene carbonate, methyl formate, dimethylsulfoxide, propylene carbonate, acetonitrile, butyrolactone, dimethylformamide, dimethyl carbonate, diethyl carbonate, sulfolane, ethyl methyl carbonate, and alkali metal. A non-aqueous electrolyte solvent in which a Lewis acid containing ions is dissolved, a solid electrolyte or the like can be used. Furthermore, various conventionally known materials can be used for other elements such as structural materials such as a separator and a battery case, and there is no particular limitation.

[0007]

EXAMPLES The method of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, preparation and measurement of the battery were performed in a dry box under an argon atmosphere.

Example 1 FIG. 1 is a cross-sectional view of a coin type battery which is one specific example of the battery according to the present invention, in which 1 is a sealing plate, 2 is a gasket, and 3 is a gasket.
Is a positive electrode case, 4 is a negative electrode, 5 is a separator, and 6 is a positive electrode material mixture pellet. For the positive electrode active material, unsubstituted LiMn
_As a dopant for substitution addition of Fe with respect to ₂ O ₄ with respect to ₂ O ₄ , the doping amount was set to x = 1, and according to the following reaction formula (Formula 1), after weighing and mixing, at 650 ° C. for about 6 hours, the atmosphere A ternary compound oxide crystal powder obtained by medium heating, calcination at 1100 ° C. for 1 day, and rapid cooling was used.

[0009]

Chemical formula: Li ₂ CO ₃ + Mn ₂ O ₃ + Fe
₂ O ₃ → 2LiMnFeO ₄ + CO ↑

The X-ray diffraction pattern of the obtained powder sample is shown in FIG. That is, FIG. 2 shows the LiM which is an embodiment of the present invention.
is a diagram showing an X-ray diffraction pattern of nFeO _4. In FIG. 2, the vertical axis represents the X-ray diffraction intensity (arbitrary scale), and the horizontal axis represents the X-ray diffraction angle (2θ). The obtained X-ray diffraction pattern is basically the spinel structure of LiMn ₂ O ₄ (JCPDS # 35
-782) and LiMnTiO ₄ (JCPDS # 40-9
75), and it is clear that Mn is replaced by Fe in a solid solution state while maintaining the spinel structure like LiMnTiO ₄ . The (220) peak observed in the vicinity of 2θ = 30 ° shows that Li at the tetrahedral position is F
It shows that the structure is a random or reverse spinel structure partially substituted by e. This sample is designated as a. This sample a is crushed into powder, mixed with a conductive agent (acetylene black) and a binder (polytetrafluoroethylene), and roll-formed, and positive electrode mixture pellets 6 (thickness 0.5 mm, diameter 15 mm). And Next, a metallic lithium negative electrode 4 placed under pressure on a stainless steel sealing plate 1 was inserted into a recess of a polypropylene gasket 2, and a polypropylene microporous separator 5 and a positive electrode mixture were placed on the negative electrode 4. After arranging the pellets 6 in this order and injecting an appropriate amount of 1N solution of LiPF ₆ dissolved in a single solvent of propylene carbonate as an electrolytic solution for impregnation, the positive electrode case 3 made of stainless steel is covered and caulked. Thus, a coin-type lithium battery having a thickness of 2 mm and a diameter of 23 mm was produced.

Comparative Example 1 In order to confirm the effect of the present invention, LiMn ₂ O ₄ as a positive electrode active material was synthesized by a typical conventional method, and this sample was designated as b, and was coin-shaped as in Example 1. A lithium battery was produced.

Example 2 As a positive electrode active material, TiMn ₂ O _{4 was} substituted with Ti
As a dopant for substitution addition with respect to Mn, the doping amount is fixed at x = 1, and according to the following reaction formula (Chemical formula 2), after weighing and mixing, after heating at 650 ° C. for about 6 hours in the atmosphere, quenching is performed. The ternary compound oxide crystal powder obtained in this way was used.

[0013]

Chemical formula: Li ₂ CO ₃ + Mn ₂ O ₃ + 2T
iO ₂ → 2LiMnTiO ₄ + CO ₂ ↑

The X-ray diffraction pattern of the obtained powder sample is shown in FIG. That is, FIG. 3 shows LiM which is an embodiment of the present invention.
is a diagram showing an X-ray diffraction pattern of nTiO _4. 3, the vertical axis and the horizontal axis have the same meaning as in FIG. The obtained X-ray diffraction pattern shows the spinel structure of LiMnTiO ₄ (JC
PDS # 40-975). The (220) peak observed near 2θ = 30 ° is Li at the tetrahedral position.
Shows that it has a random or reverse spinel structure partially substituted by Ti. This sample is designated as c. A coin type lithium battery was produced in the same manner as in Example 1 except that LiMnTiO ₄ produced as described above was used as the positive electrode active material.

Example 3 As the positive electrode active material, CoMn ₂ O ₄ which was not substituted was used.
As a dopant for substitution addition with respect to Mn, the doping amount is fixed at x = 1, and according to the following reaction formula (Formula 3), after weighing and mixing, after heating at 650 ° C. for about 6 hours in the atmosphere, A ternary compound oxide crystal powder obtained by firing at 950 ° C. for 1 day and then rapidly cooling was used.

[0016]

Chemical formula: Li ₂ CO ₃ + Mn ₂ O ₃ + Co
₂ O ₃ → 2LiMnCoO ₄ + CO ↑

An X-ray diffraction pattern of the obtained powder sample is shown in FIG. That is, FIG. 4 shows an example of LiM which is an embodiment of the present invention.
is a diagram showing an X-ray diffraction pattern of nCoO _4. 4, the vertical axis and the horizontal axis have the same meaning as in FIG. The obtained X-ray diffraction pattern is basically LiMn ₂ O having a spinel structure.
₄ (JCPDS # 35-782) and LiMnTiO
₄ (JCPDS # 40-975),
It can be seen that Mn is replaced by Co in a solid solution state while maintaining the spinel structure like LiMnTiO ₄ . The (220) peak observed in the vicinity of 2θ = 30 ° indicates that it has a random spinel structure in which Li in the tetrahedral position is partially replaced by Co although it is weak. This sample is referred to as d. A coin-type lithium battery was produced in the same manner as in Example 1 except that LiMnCoO ₄ produced as described above was used as the positive electrode active material.

Batteries using the samples a (Example 1), b (Comparative Example 1), c (Example 2), and d (Example 3) as the positive electrode active materials prepared as described above were tested as 0. 25 mA / cm
1.0 at the current density of ² after the initial charge of 5.3V termination
5 to 8 show the initial discharge curves when the cycle is performed under the voltage regulation between V and 5.0V. That is, FIG. 5 is a characteristic diagram showing an initial discharge curve of LiMnFeO ₄ which is an example of the present invention after initial charging of 5.3 V, and FIG. 6 shows 5.5 of LiMn ₂ O ₄ which is a comparative example of the present invention. FIG. 8 is a characteristic diagram showing an initial discharge curve after a 3 V initial charge, FIG. 7 is a characteristic diagram showing an initial discharge curve after a 5.3 V initial charge of LiMnTiO ₄ which is one example of the present invention, and FIG. FIG. 5 is a characteristic diagram showing an initial discharge curve after initial charging of 5.3 V of LiMnCoO ₄ which is an example of the invention. 5 to 8, the vertical axis represents the battery voltage (V) and the horizontal axis represents the discharge time (hr). In addition, each positive electrode sample has 4V after the initial charge of 5.0V.
Area capacity (termination of 3.5V), low voltage area capacity (1.5V)
Termination) is shown in Table 1.

[0019]

[Table 1]

As an example, 0.25 mA / of the sample a
FIG. 9 shows a charge / discharge curve during the voltage regulated charge / discharge cycle test between 1.0 V and 5.0 V at a current density of cm ² . That is, FIG. 9 is a characteristic diagram showing a charge / discharge curve during a voltage regulation test between 1.0 V and 5.0 V of LiMnFeO ₄ which is an example of the present invention, and in FIG. 9, the vertical axis represents the battery voltage (V ), The horizontal axis represents charge / discharge cycle time (hr). As is clear from FIGS. 5 to 8 and Table 1, undoped LiM
It can be seen that in the case of the positive electrode active material of the present invention, the low voltage region can be expanded up to 1.8 times at the maximum in exchange for the reduction of the 4 V discharge region of n ₂ O ₄ . Moreover, from FIG.
It can be seen that even with a 5.0 V voltage regulation charge / discharge cycle, it has good cycleability with extremely small capacity deterioration.

[0021]

As described above, according to the present invention,
It is possible to construct a large-capacity non-aqueous electrolyte secondary battery with a small discharge voltage difference and high practicality, and it has an advantage that it can be used in various fields.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a coin-type battery that is an embodiment of the present invention.

FIG. 2 shows X of LiMnFeO ₄ which is an embodiment of the present invention.
It is a figure which shows a line diffraction pattern.

FIG. 3 is an X of LiMnTiO ₄ which is an embodiment of the present invention.
It is a figure which shows a line diffraction pattern.

FIG. 4 is an X of LiMnCoO ₄ which is an example of the present invention.
It is a figure which shows a line diffraction pattern.

FIG. 5 is a characteristic diagram showing an initial discharge curve of LiMnFeO _{4 according to} one example of the present invention after 5.3 V initial charging.

6 is a comparative example of the present invention, 5.3 of LiMn ₂ O ₄
It is a characteristic view which shows the initial discharge curve after V initial charge.

FIG. 7 is a characteristic diagram showing an initial discharge curve after initial charging of 5.3 V of LiMnTiO ₄ , which is an example of the present invention.

FIG. 8 is a characteristic diagram showing an initial discharge curve of LiMnCoO ₄ , which is an example of the present invention, after 5.3 V initial charging.

FIG. 9 is a characteristic diagram showing a charge / discharge curve of LiMnFeO _{4 according to} one example of the present invention during a voltage regulation test between 1.0 V and 5.0 V.

[Explanation of symbols]

1: Sealing plate, 2: Gasket, 3: Positive electrode case, 4: Negative electrode, 5: Separator, 6: Positive electrode mixture pellet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideaki Otsuka 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Instructor Youji Sakurai 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (72) Inventor Junichi Yamaki 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation

Claims (4)

[Claims] 1. A composition formula, A _y Mn _2-x M _x O ₄ (A is an alkali metal, M is a metal other than A and Mn, 0.5 <x <
1.5, 0 <y <2), which contains as a positive electrode active material a substance mainly containing an alkali metal (A) -containing manganese mixed oxide, an alkali metal, an alkaline earth metal, or an alkali metal or an alkaline earth A substance capable of occluding and releasing a metal ion is used as the negative electrode active material, and a substance capable of moving to cause an electrochemical reaction of the alkali metal ions with the positive electrode active material or the negative electrode active material is used as the electrolyte substance. A non-aqueous electrolyte secondary battery characterized by: 2. The alkali metal (A) -containing manganese composite oxide, A _y Mn _2-x M _x O ₄ is used as a metal (M) other than Mn such as Fe, Ru, Os, Ti, Zr, Hf, N.
b, Ta, Cr, Mo, W, Co, Rh, Ir, Ni,
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is a substance containing at least one of Sb, Si, Ge, Sn, and Pb. 3. A random spinel in which the alkali metal (A) -containing manganese complex oxide, A _y Mn _2-x M _x O ₄ , contains a metal (M) other than the alkali metal (A) at the tetrahedral site of oxygen. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery has a negative or spinel structure. 4. An alkali metal compound, a manganese compound,
And a compound of the substitutional addition metal (M) are mixed, heat-treated, and then rapidly cooled to form a random spinel type structure or an inverse spinel type structure.
Alkali metal (A) containing manganese complex oxide according to any one of to 3, the manufacturing method of the _{A y Mn 2-x M x} O 4.