JPH09161799A - Manufacture of positive electrode for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively improve a cycle characteristic in high energy density. SOLUTION: This manufacturing method contains a process of preparing an aqueous solution by dissolving at least one kind of water soluble lithium compound selected from a group composed of chloride, bromide, iodide, chlorate, perchlorate, hydrogen carbonate and oxalate of lithium and at least one kind of water soluble manganese compound selected from a group composed of chloride, bromide, iodide, perchlorate and sulfate of manganese and a process of generating lithium having a spinel structure and and a composite oxide of manganege by baking a obtained solid material by heating the aqueous solution.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to improvement of a positive electrode of a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art Many studies have been carried out because non-aqueous electrolyte secondary batteries using lithium or a lithium compound as a negative electrode have a high electromotive force and are expected to have a higher energy density than conventional nicad or lead acid batteries. ing. Hitherto, as a positive electrode active material for a non-aqueous electrolyte secondary battery, LiCoO ₂ , LiNiO ₂ , L having a layered structure or a tunnel structure and a crystal structure capable of allowing lithium ions to enter and exit.
_{iMn 2 O 4, LiFeO 2,} MnO 2, V 2 O 5, Cr
Oxides of transition metals such as ₂ O ₅ , TiS _{2 and} MoS ₂ and chalcogen compounds have been proposed. Of these, LiCoO ₂ , LiNiO ₂ and LiMn ₂ O ₄ are particularly attracting attention as positive electrode active materials for 4V class non-aqueous electrolyte lithium secondary batteries. LiCoO ₂ has a well-ordered layered structure and can obtain high voltage and high capacity. However, cobalt is an expensive element, and there are concerns about the supply of raw materials such as high cost, supply shortage due to changes in the world situation, and soaring prices. Moreover, LiNiO ₂ having the same crystal structure as LiCoO ₂
Is a material that can obtain a high capacity exceeding LiCoO ₂ at a relatively low cost and has been actively researched and developed for practical use, but there is a problem in terms of crystal structure stability and the like.

On the other hand, LiMn ₂ O ₄ has an advantage that manganese has a very low price compared with nickel as well as cobalt. Also, the crystal structure is LiCo
Unlike O ₂ and LiNiO _2, have the structure of the spinel type having a three-dimensional net-like tunnel structure, easy to handle in a stable, because synthesis is easy, replaces the LiCoO ₂ 4V
Research is being carried out as one of the positive electrode active materials for high-grade non-aqueous electrolyte lithium secondary batteries.

[0004]

However, LiMn ₂ O ₄
Is excellent in terms of cost, but has a small capacity, and
The decrease in the charge / discharge capacity with the charge / discharge cycle was large. The present invention solves the above problems,
An object is to provide a positive electrode for a non-aqueous electrolyte lithium secondary battery that is inexpensive, has a high energy density, and has excellent cycle characteristics.

[0005]

The method for producing a positive electrode for a non-aqueous electrolyte secondary battery according to the present invention comprises a lithium chloride, bromide, iodide, chlorate, perchlorate, hydrogen carbonate and oxalic acid. At least one water-soluble lithium compound selected from the group consisting of salts, and at least one water-soluble manganese compound selected from the group consisting of manganese chloride, bromide, iodide, perchlorate and sulfate. And a step of producing a composite oxide of lithium and manganese having a spinel structure by heating the aqueous solution and baking the obtained solid content.

Further, at least one alcohol-soluble lithium compound selected from the group consisting of lithium chloride, bromide, iodide, chlorate and perchlorate, and manganese chloride, bromide and iodide. , A step of preparing an alcohol solution in which at least one alcohol-soluble manganese compound selected from the group consisting of perchlorates and sulfates is dissolved, and solid content is added by adding oxalic acid to the alcohol solution. The process of generating,
It includes a step of producing a composite oxide of lithium and manganese having a spinel structure by firing the solid content.

As described above, by dissolving the lithium compound and the manganese compound, which are the raw materials, in water or alcohol, the lithium and manganese can be uniformly mixed. By heat treating the lithium compound and the manganese compound, the composition and the structure can be changed depending on the site. It is possible to obtain a composite oxide of lithium and manganese that does not vary. Since the oxide having a spinel structure obtained by this production method has no compositional bias, there is little lithium that is difficult to be desorbed and inserted, and when this is used as the positive electrode active material of a non-aqueous electrolyte secondary battery, a large charge is obtained. The discharge capacity can be obtained. In addition, since the structure is uniform, there is no portion where stress caused by expansion and contraction of the crystal lattice due to charge and discharge is concentrated, collapse of the crystal lattice due to charge and discharge is suppressed, and excellent cycleability can be realized. . The present invention is suitable for producing a complex oxide represented by the formula LiMn ₂ O ₄ . In this case, it is preferable that the compounding ratio of the lithium compound and the manganese compound is approximately 1: 2 in terms of the number of atoms.

Further, at least one water-soluble lithium compound selected from the group consisting of lithium chloride, bromide, iodide, chlorate, perchlorate, hydrogencarbonate and oxalate, and manganese At least one water-soluble manganese compound selected from the group consisting of chloride, bromide, iodide, perchlorate and sulfate, and a metal M ₁ (where M ₁ is a group consisting of Co, Ni and Cr) A step of preparing an aqueous solution in which at least one selected water-soluble compound is dissolved, and heating the aqueous solution and calcining the obtained solid content to obtain an atomic ratio of Mn: M
₁ = 2-y: y (provided that 0.01 ≦ y ≦ 0.3), which includes a step of producing a composite oxide containing lithium and manganese having a spinel structure.

Further, at least one alcohol-soluble lithium compound selected from the group consisting of lithium chloride, bromide, iodide, chlorate and perchlorate, and manganese chloride, bromide and iodide. , At least one alcohol-soluble manganese compound selected from the group consisting of perchlorates and sulfates, and an alcohol-soluble compound of a metal M ₂ (M ₂ is at least one of Co and Ni) are dissolved. The step of preparing the alcohol solution thus prepared, the step of producing a solid content by adding oxalic acid to the alcohol solution, and the solid content being calcined so that the atomic ratio is Mn: M ₂ = 2-y. :
It includes a step of producing a composite oxide containing lithium and manganese having a spinel structure of y (provided that 0.01 ≦ y ≦ 0.3). In addition to lithium and manganese, when adding cobalt, nickel or chromium as a third component for improving the cycle property, also dissolve the soluble compound in water or alcohol to disperse it uniformly. Therefore, the effect of addition can be obtained more effectively than in the case of synthesizing in a solid phase. Further, the firing temperature is 300 ° C to 1000 ° C.
It is something that is. The present invention provides the formula LiMn _{2- y My} O
₄ (provided that M is at least one selected from the group consisting of Co, Ni and Cr) is suitable for producing a composite oxide. In this case, the compounding ratio of the lithium compound, the manganese compound, and the compound of the metal M is preferably approximately Li: (Mn + M) = 1: 2 in terms of the number of atoms.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to Examples. [Example 1] A method for synthesizing a composite oxide of lithium and manganese having a spinel structure using a water-soluble lithium compound and a water-soluble manganese compound as starting materials will be described. The water-soluble lithium compound and the manganese compound were weighed so that the ratio of the numbers of lithium and manganese atoms was 1: 2, and water was added to each and completely dissolved. As a starting material, chloride (LiCl), bromide (LiBr), iodide (LiI), chlorate (Li) as a water-soluble lithium compound is used.
ClO _3), perchlorate _{(LiClO 4 · 3H 2 O)} , bicarbonate (LiHCO ₃₎ and oxalate (Li ₂ (C
Using ₂ O _4)), respectively, chloride as water-soluble manganese compound (MnCl _2), bromide (MnBr _2), iodide (MnI _2), perchlorate _{(Mn (ClO 4) 2 ·} 8H
₂ O) and sulfate (MnSO ₄ ) were used respectively.
An aqueous solution of the lithium compound and an aqueous solution of the manganese compound were mixed, and heated with stirring to evaporate the water to obtain a solid content as a precursor. The solid content was fired at 600 ° C. in an air atmosphere to synthesize a composite oxide of lithium and manganese. This oxide has a substantially uniform spinel structure and its composition is approximately LiMn.
₂ O ₄ . This oxide, which is a positive electrode active material, acetylene black, which is a conductive agent, and polytetrafluoroethylene resin, which is used as a binder, are mixed in a weight ratio of 7: 2: 1 and sufficiently dried to obtain a positive electrode. A mixture was obtained. This positive electrode mixture was pressure-molded into a disk-shaped pellet having a diameter of 17.5 mm at a pressure of 2 ton / cm ² to obtain a positive electrode. Also, as a comparative example, a composite synthesized by mixing lithium carbonate powder and manganese dioxide powder at a ratio of the number of atoms of lithium and manganese of Li: Mn = 1: 2, and calcining in air at 800 ° C. for 48 hours. A positive electrode was similarly prepared using the compound.

The charge and discharge characteristics of the positive electrode were evaluated using the test cell shown in FIG. The manufacturing method of the test cell is shown below. The obtained positive electrode 1 was placed in the case 2, and then the separator 3 made of a microporous polypropylene film was placed on the positive electrode 1. A solution prepared by mixing 1 mol / liter of lithium hexafluorophosphate (LiPF ₆ ) in ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 was used.
The non-aqueous electrolyte was poured into the separator 3. On top of this,
A disk-shaped negative electrode 4 made of metal Li having a diameter of 17.5 mm was attached to the inner side, and a sealing plate 6 having a polypropylene gasket 5 was placed on the outer peripheral portion to seal the cell, and a test cell was prepared.
These test cells were charged and discharged under a constant current of 0.5 mA and voltage regulation of a voltage range of 3.0 V to 4.5 V, and the capacity per weight of the positive electrode active material was evaluated. Table 1 shows the initial discharge capacity and the capacity retention rate after 50 cycles of the positive electrode produced from each combination of the starting materials.

[0012]

[Table 1]

In the test cells of the examples, the initial discharge capacity showed an excellent value of about 135 mAh / g regardless of which combination of raw materials was used. The capacity retention rate after 50 cycles also showed a value of 90% or more. On the other hand, in the test cell using the positive electrode made of the compound synthesized from the solid phase of Comparative Example (hereinafter referred to as the cell of Comparative Example 1), the initial capacity was 125 mAh / g.
The value was slightly lower than that of the test cell of the example. Further, the capacity retention ratio after 50 cycles was 60%, which was a large cycle deterioration.

The difference is considered as follows. When synthesizing from a solid phase as in Comparative Example, since the raw materials are mixed with each other, it is difficult to eliminate the uneven distribution of lithium and manganese in the raw material mixture before firing. This bias is eliminated to some extent by the diffusion of atoms during firing, but it is difficult to make it completely uniform, and the composition and structure of the synthesized compound become uneven. Therefore, lithium is less likely to be inserted and desorbed, and when used for the positive electrode, the initial capacity decreases. In addition, since there are structurally non-uniform portions, the crystal structure is likely to be destroyed due to expansion and contraction of the lattice during charge and discharge, and cycle deterioration is considered to be large.

On the other hand, in the composite oxide of lithium and manganese of this embodiment, since the raw materials are mixed as an aqueous solution, lithium and manganese can be uniformly distributed in the precursor. Therefore, the oxide obtained by firing has a uniform composition and has a uniform spinel structure.
Therefore, there is less lithium that cannot participate in charging and discharging,
The initial capacity approaches the theoretical capacity of 148 mAh / g.
Even when the charge and discharge cycle is repeated, the structure is uniform, so there is no part where the stress of expansion and contraction of the crystal lattice due to charge and discharge concentrates, and the collapse of the crystal lattice due to charge and discharge is suppressed, and excellent cycleability realizable. From the above results, it became clear that a positive electrode for a non-aqueous electrolyte secondary battery excellent in initial capacity and cycleability can be manufactured by the manufacturing method of this example.

In the above embodiment, the step of heating the mixed aqueous solution of the starting materials to obtain the solid content as the precursor and the step of firing the precursor to obtain the composite oxide were performed separately. The same homogeneous spinel structure compound is obtained even when the composite oxide of lithium and manganese is directly synthesized from the mixed aqueous solution by using the above method. By using this, excellent non-aqueous electrolyte electrolyte is obtained. The next battery is obtained.

[Example 2] Next, an example of producing a positive electrode for a non-aqueous electrolyte secondary battery from an alcohol solution of a lithium compound and a manganese compound will be described. An alcohol-soluble lithium compound and an alcohol-soluble manganese compound were used, and the ratio of the number of lithium and manganese atoms was 1: 2.
Were weighed, and ethanol was added to each to completely dissolve them. Here, any one of chloride, bromide, iodide, chlorate and perchlorate is used as the lithium compound, and any one of chloride, bromide, iodide, perchlorate and lead sulfate is used as the manganese compound. Using. An ethanol solution of these lithium compounds and an ethanol solution of manganese compounds were mixed. While stirring the mixed solution, an ethanol solution of oxalic acid was added to generate a precipitate that was a precipitation precursor. The oxalic acid was added until the reaction was completed. The produced precipitate was dried and calcined at 750 ° C. in an air atmosphere to synthesize a composite oxide of lithium and manganese. This oxide has a uniform spinel structure and its composition is approximately LiM.
It was n ₂ O ₄ . This oxide, which is a positive electrode active material, acetylene black, which is a conductive agent, and polytetrafluoroethylene resin, which is a binder, are mixed in a weight ratio of 7: 2: 1, and sufficiently dried to produce a positive electrode. A mixture was obtained. This positive electrode mixture,
A positive electrode was obtained by pressure molding into a disk-shaped pellet having a diameter of 17.5 mm at a pressure of 2 ton / cm ² .

A test cell similar to that of Example 1 was prepared using these positive electrodes, and a charge / discharge test similar to that of Example 1 was conducted. Table 2 shows the initial discharge capacity of the positive electrode and the discharge retention rate after 50 cycles.

[0019]

[Table 2]

The cell of this example has an initial discharge capacity of about 135 mAh / g, whichever combination of compounds is used.
The capacity retention ratio after 50 cycles was also 90% or more, which was compared with the initial capacity of 125 mAh / g and the capacity retention ratio after 50 cycles of 60% in the cell of Comparative Example 1 using the positive electrode synthesized from the solid phase as a comparative example. And showed excellent characteristics. The reason why such a result is obtained is considered as follows.
When oxalic acid is added to a mixed alcohol solution of a lithium compound and a manganese compound, a solid content as a precursor is produced, and this solid content is also produced in a state where lithium and manganese are uniformly mixed. Therefore, the composite oxide obtained by firing with this as a precursor also has a uniform composition and structure, and excellent initial capacity and cycle property can be obtained for the same reason as in Example 1. From this result, it was revealed that the positive electrode for a non-aqueous electrolyte secondary battery excellent in initial capacity and cycleability was obtained by the production method of this example.

[Embodiment 3] As a method of improving the cycle property of LiMn ₂ O ₄ , there is a method of substituting a part of manganese with cobalt, nickel, chromium or the like. In this embodiment, such an active material is used. A case where the used positive electrode is manufactured from a water-soluble raw material will be described. Lithium chloride was used as the water-soluble lithium compound, manganese chloride was used as the manganese compound, and cobalt chloride was used as the water-soluble cobalt compound. These were weighed so that the ratio of the numbers of lithium, manganese, and cobalt atoms was 1: 2-y: y, and water was added to each to completely dissolve them. These aqueous solutions were mixed, and heated with stirring to evaporate water to obtain a solid content as a precursor. This solid content was fired at 550 ° C. in an air atmosphere to synthesize a composite oxide of lithium, manganese and cobalt. The samples to which nickel and chromium were added were also synthesized using the same method. Divalent chloride was used for both the water-soluble nickel compound and the chromium compound. These oxides
It has a uniform spinel structure and its composition is generally LiM.
_{n 2-y M y O 4} ( where, M is Co, is any one of N and Cr.) it was.

This compound, which is a positive electrode active material, acetylene black, which is a conductive agent, and polytetrafluoroethylene resin, which is a binder, are mixed at a weight ratio of 7: 2: 1,
Allowed to dry sufficiently. 2 tons / c of the positive electrode mixture thus obtained
A positive electrode was obtained by pressure molding into a disk-shaped pellet having a diameter of 17.5 mm with a pressure of m ² . Example 1 using these positive electrodes
A test cell similar to the above was prepared. Test cells using a positive electrode in which a part of manganese is replaced with cobalt, nickel, and chromium are referred to as cells of Example 3-1, Example 3-2, and Example 3-3, respectively.

As a comparative example, a positive electrode was prepared by using the active material produced by the same solid phase reaction as in Comparative Example 1 with the same amount of the compound as in Example. Lithium carbonate, manganese dioxide, and cobalt hydroxide powders were used in an atomic ratio of Li: M.
By mixing the solid as it is so that n: Co = 1: 2-y: y and firing in air at 800 ° C. for 48 hours,
A cobalt substitution sample was obtained. The replacement with nickel and chromium was also carried out by the same method using hydroxide. Using these, a positive electrode similar to that in the above-mentioned example was molded. A test cell similar to that of Example 1 was produced using these positive electrodes. The test cells using the positive electrode active material in which manganese was replaced with cobalt, nickel, and chromium are referred to as cells of Comparative Example 3-1, Comparative Example 3-2, and Comparative Example 3-3. The same charging / discharging method as in Example 1 was performed using these cells. Table 3 shows the relationship between the amount of cobalt added and the initial capacity, and the capacity retention rate after 50 cycles.

[0024]

[Table 3]

Example 3 by adding cobalt
-1, the capacity retention rate is improved in both cells of Comparative Example 3-1, but the initial capacity is reduced. The initial capacity decreases with an increase in the amount of addition, and particularly when the amount y of addition exceeds 0.3, the initial capacity rapidly increases.
3 or less is suitable. The change in the capacity retention rate due to the increase in the amount of cobalt added was measured in Example 3-1 and Comparative Example 3-1.
The cell of Comparative Example 3-1 has a difference of y = 0.
The capacity retention rate does not increase unless more than 1 is added,
In the cell of Example 3-1, the capacity retention rate is increased by adding a very small amount such as y = 0.01. Therefore, in the cell of Comparative Example 3-1, when the addition amount is increased until good cycleability is obtained, the initial capacity is greatly reduced, but in the cell of Example 3-1, a small decrease in the initial capacity appears. Cycle performance can be improved by adding cobalt.

When the effect of reducing the initial capacity and improving the cycleability are combined, the cell of Example 3-1 has a cobalt to manganese ratio of 0.01: 1.99 to 0.3: 1.7. In addition, good results were obtained in terms of initial capacity and cycleability. Particularly, when 0.15: 1.85 or a smaller amount of cobalt was added, the decrease in initial capacity was small and cycleability could be effectively improved. This is presumably because, as shown in Example 2, the cell of Example 3-1 had a uniform distribution of elements in the sample, and therefore the effect of cobalt addition was sufficiently exhibited. Tables 4 and 5 show the results for the cells using the positive electrode active materials to which nickel and chromium were added (the cells of Example 3-2 and Example 3-3, respectively).

[0027]

[Table 4]

[0028]

[Table 5]

When nickel and chromium were added respectively, the same tendency as in the case of adding cobalt was exhibited, and in the cells of Examples 3-2 and 3-3, the ratio of nickel or chromium to manganese was 0. 01: 1.99 ~
In the range of 0.3: 1.7, both the initial capacity and the cycle property are good, and especially nickel has a capacity of 0.
When the amount of nickel added is 1: 1.9 or less, or when the amount of chromium added is 0.15: 1.85 or less, the decrease in initial capacity is small and the cycleability can be effectively improved. . From the above results, even when adding cobalt, nickel, or chromium to the composite oxide of lithium and manganese having a spinel structure, by using the manufacturing method of the present example, the initial capacity,
A positive electrode for a non-aqueous electrolyte secondary battery having excellent cycleability can be obtained.

As the water-soluble lithium compound,
Similar effects can be obtained even when chloride, bromide, iodide, chlorate, perchlorate, hydrogen carbonate and oxalate are used. Also, the same effect can be obtained when several of these are used. Similar effects can be obtained even when chloride, bromide, iodide, perchlorate or sulfate is used as the water-soluble manganese compound. As compounds of cobalt, nickel or chromium, in addition to these chlorides, sulfates, nitrates, acetates,
Even when using various water-soluble compounds such as perchlorate,
Similar effects can be obtained. Further, in the above-described example, the step of heating the mixed aqueous solution of the starting materials to obtain the solid content which becomes the precursor and the step of firing the precursor to obtain the composite oxide are separated, but both steps are performed once. The same effect can be obtained even when the composite oxide is produced directly from the mixed aqueous solution by heating.

[Embodiment 4] Next, a case where a positive electrode containing cobalt and nickel is manufactured from a raw material soluble in alcohol will be described. Lithium perchlorate was used as the alcohol-soluble lithium compound. Further, manganese perchlorate was used as a manganese compound soluble in alcohol.
As a cobalt compound or a nickel compound mixed with these, cobalt perchlorate or nickel perchlorate was used. These were weighed so that the atomic ratio of lithium, manganese, and cobalt or nickel was 1: 2-y: y, and ethanol was added to each and completely dissolved.
These ethanol solutions were mixed and, with stirring, an ethanol solution of oxalic acid was added until the precipitation-forming reaction was completed. The solid content produced is dried and dried in an air atmosphere at 80
By firing at 0 ° C., a composite oxide in which cobalt or nickel was added to lithium and manganese was synthesized. These oxides are uniform and have a spinel structure, and their composition is roughly LiMn _2-y MyO ₄ (where M is Co.
And Ni. )Met.

This composite oxide, which is a positive electrode active material, acetylene black, which is a conductive agent, and polytetrafluoroethylene resin, which is a binder, are mixed in a weight ratio of 7: 2: 1 and dried sufficiently. Let 2 tons of the positive electrode mixture thus obtained
A disk-shaped pellet having a diameter of 17.5 mm was pressure-molded with a pressure of cm ² to obtain a positive electrode. Example 1 using these positive electrodes
A test battery similar to the above was manufactured. The cells using the positive electrode active material to which cobalt and nickel were added are referred to as the test cells of Example 4-1 and Example 4-2, respectively. The characteristics of these test cells were evaluated in the same manner as in Example 1.
Table 6 shows the relationship between the initial capacity of the cell and the capacity retention rate after 50 cycles with respect to the amount of cobalt added to the positive electrode.

[0033]

[Table 6]

The initial capacity decreases as the amount of cobalt added increases, and it rapidly decreases when the amount y of addition exceeds 0.3. Therefore, the amount y of addition of 0.3 or less is suitable. This tendency of decrease is the same in the cells of Example 4-1 and Comparative example 3-1. On the other hand, there is a difference in the change in the capacity retention rate due to the increase in the addition amount, and in the cell of Comparative Example 3-1, no increase in the capacity retention rate was observed unless cobalt was added at y = 0.1 or more. In the cell of Example 4-1, y =
Addition of a very small amount such as 0.01 increases the capacity retention rate. Therefore, in the cell of Comparative Example 3-1, when the amount of cobalt added was increased until good cycleability was obtained, the initial capacity decreased significantly, but in the cell of Example 4-1, the initial capacity decreased. The cycleability can be improved by adding a small amount that appears only slightly. When the effect of reducing the initial capacity and improving the cycle property are combined, the ratio of the number of atoms of cobalt and manganese is in the range of 0.01: 1.99 to 0.3: 1.7,
A positive electrode excellent in both initial capacity and cycleability can be obtained. Particularly, when 0.15: 1.85 or a smaller amount of cobalt added, a positive electrode excellent in both initial capacity and cycleability can be obtained. This is because, as shown in Example 2, the cell of Example 4-1 has a uniform distribution of elements in the sample, so that the additive element is also dispersed uniformly in the sample, and the effect of the addition is I think that it is because it is easily demonstrated. Table 7 shows the results for the positive electrode to which nickel was added.

[0035]

[Table 7]

These results also show the same tendency as in the case of adding cobalt, and in the cell of Example 4-2 as well, the ratio of the numbers of nickel and manganese atoms is 0.01: 1.99 to 0.3 :.
In the range of 1.7, good results were obtained in both initial capacity and cycleability. Especially when 0.1: 1.9 or less nickel was added, a positive electrode excellent in both initial capacity and cycleability was obtained. You can see that you can get it. From the above results, when substituting a part of manganese of the composite oxide of lithium and manganese having a spinel structure with cobalt or nickel, by using the manufacturing method of this example, the initial capacity and the cycle property are excellent in non-aqueous. A positive electrode for an electrolyte secondary battery is obtained. Similar effects can be obtained by using lithium chloride, bromide, iodide, chlorate and perchlorate as the alcohol-soluble lithium compound. Similar effects can be obtained by using manganese chloride, bromide, iodide, perchlorate and sulfate as the alcohol-soluble manganese compound. As cobalt or nickel, even when various alcohol-soluble compounds such as halides, nitrates and acetates thereof are used,
Similar effects can be obtained.

Example 5 Next, the temperature during firing was examined. Using lithium chlorate as the lithium compound and manganese sulfate as the manganese compound, a solid content as a precursor containing lithium and manganese was obtained by the same procedure as in Example 1, and the solid content was calcined at various temperatures. When each obtained sample was analyzed by X-ray diffraction, it was 3
It was confirmed that the composite oxide obtained by firing at a temperature of 00 ° C. or higher had a spinel structure and was uniform LiMn ₂ O ₄ , but there were many impurity peaks seen at a temperature lower than that. It was Example 1 using these composite oxides
A test cell similar to the above was prepared, and the same electrode characteristics as in Example 1 were evaluated. The relationship between the firing temperature and the initial capacity is shown in FIG. A large initial capacity was obtained in the cell using the positive electrode fired at a temperature of 300 ° C. or higher. On the other hand, the firing temperature is 1000
When the temperature exceeded ℃, the capacity tended to decrease gradually. From the above results, the heating temperature is 300 ° C to 1000 ° C.
It can be seen that the temperature range of is suitable.

Although the case where the precursor produced from the aqueous solution is fired using lithium chlorate and manganese sulfate as raw materials is shown here, lithium chloride, bromide, iodide or perchlorine may be used in place of lithium chlorate. The same effect can be obtained by using any one of acid salt, hydrogen carbonate and oxalate. The same effect can be obtained by using manganese chloride, bromide, iodide and perchlorate instead of manganese sulfate. Further, as shown in Examples 2 to 4, even when it is produced from an alcohol solution or when a part of manganese is replaced by cobalt, nickel, chromium, etc., good initial temperature is obtained by firing in the same temperature range. Capacity is obtained.

Although a coin battery is used in the above embodiments, the technical idea of the present invention, such as excellent cycleability, is the same. Therefore, the present invention is not limited to this structure. The same effect can be obtained in a secondary battery having a cylindrical shape, a rectangular shape, a flat shape, or the like.
Further, in the above-mentioned examples, metallic lithium was used as the negative electrode active material of the cell, but metallic materials such as aluminum and aluminum alloys which are alloyed with lithium, or lithium such as carbon material reversibly absorbs and releases lithium. The same effect can be obtained by using a material that can be used. further,
As the non-aqueous electrolytic solution, in this example, a mixture of ethylene carbonate in which 1 mol / liter of lithium hexafluorophosphate was dissolved and diethyl carbonate in a volume ratio of 1: 1 was used. It goes without saying that the same effect can be obtained by using the electrolyte salt or solvent. In this example, an aqueous solution or an alcohol solution in which a lithium compound and a manganese compound were previously dissolved was used, but it is also possible to use a solution in which a lithium compound and a manganese compound are simultaneously dissolved. When firing a precursor containing lithium and manganese, lithium is scattered depending on firing conditions, and the ratio of Li to Mn varies before and after firing. Therefore, it may be necessary to add Li in a slightly larger amount next to the composition. Further, even if the composition ratio is slightly changed, it shows good performance as a positive electrode active material.

[0040]

According to the present invention, a composite oxide of lithium and manganese having a spinel structure having a uniform composition and structure can be provided. Further, by using this as a positive electrode of a non-aqueous electrolyte secondary battery, it is possible to provide a non-aqueous electrolyte secondary battery having high energy density and excellent cycle characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a test cell used for evaluation of a positive electrode in an example of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a firing temperature of a precursor of a positive electrode active material and an initial discharge capacity of a cell using the obtained positive electrode active material in Example 5 of the present invention.

[Explanation of symbols]

 1 Positive electrode 2 Case 3 Separator 4 Li negative electrode 5 Gasket 6 Sealing plate

Continuing on the front page (72) Inventor Shuji Ito 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A lithium chloride, bromide, iodide,
At least one water-soluble lithium compound selected from the group consisting of chlorates, perchlorates, hydrogencarbonates and oxalates, and chlorides, bromides, iodides, perchlorates and sulfates of manganese Lithium and manganese having a spinel structure by preparing an aqueous solution in which at least one water-soluble manganese compound selected from the group consisting of is dissolved, and heating the aqueous solution and firing the obtained solid content. A method for producing a positive electrode for a non-aqueous electrolyte secondary battery, the method including the step of producing a composite oxide. 2. A chloride, bromide, iodide of lithium,
At least one alcohol-soluble lithium compound selected from the group consisting of chlorates and perchlorates;
A step of preparing an alcohol solution in which at least one alcohol-soluble manganese compound selected from the group consisting of manganese chloride, bromide, iodide, perchlorate and sulfate is dissolved; Production of a positive electrode for a non-aqueous electrolyte secondary battery including a step of producing a solid content by adding an acid and a step of producing a composite oxide of lithium and manganese having a spinel structure by baking the solid content. Law. 3. Lithium chloride, bromide, iodide,
At least one water-soluble lithium compound selected from the group consisting of chlorates, perchlorates, hydrogencarbonates and oxalates, and chlorides, bromides, iodides, perchlorates and sulfates of manganese At least one water-soluble manganese compound selected from the group consisting of, and a metal M ₁ (provided that
M ₁ is at least one selected from the group consisting of Co, Ni and Cr), a step of preparing an aqueous solution in which a water-soluble compound is dissolved, and the aqueous solution is heated, and the obtained solid content is calcined. As a result, the atomic ratio is Mn: M ₁ =
2-y: Manufacture of a positive electrode for a non-aqueous electrolyte secondary battery, including a step of producing a composite oxide of lithium and manganese having a spinel structure of y (where 0.01 ≦ y ≦ 0.3) Law. 4. Lithium chloride, bromide, iodide,
At least one alcohol-soluble lithium compound selected from the group consisting of chlorates and perchlorates;
At least one alcohol-soluble manganese compound selected from the group consisting of manganese chloride, bromide, iodide, perchlorate and sulfate, and a metal M ₂ (provided that
M ₂ is at least one of Co and Ni), a step of preparing an alcohol solution in which an alcohol-soluble compound of Co and Ni is dissolved, a step of producing a solid content by adding oxalic acid to the alcohol solution, By firing, the atomic ratio is Mn: M ₂ = 2-y: y
(However, 0.01 ≦ y ≦ 0.3.) A method for producing a positive electrode for a non-aqueous electrolyte secondary battery, comprising the step of producing a composite oxide containing lithium and manganese having a spinel structure. 5. The method for producing a positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the firing temperature is 300 ° C. to 1000 ° C.