JP2008050259A - Lithium-manganese composite oxide and lithium secondary battery - Google Patents

Lithium-manganese composite oxide and lithium secondary battery Download PDF

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JP2008050259A
JP2008050259A JP2007247452A JP2007247452A JP2008050259A JP 2008050259 A JP2008050259 A JP 2008050259A JP 2007247452 A JP2007247452 A JP 2007247452A JP 2007247452 A JP2007247452 A JP 2007247452A JP 2008050259 A JP2008050259 A JP 2008050259A
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lithium
composite oxide
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manganese composite
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Masahiro Kikuchi
政博 菊池
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Nippon Chem Ind Co Ltd
日本化学工業株式会社
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage
    • Y02E60/12Battery technologies with an indirect contribution to GHG emissions mitigation
    • Y02E60/122Lithium-ion batteries

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium-manganese composite oxide useful as a cathode active material for a lithium secondary battery, which is excellent in discharge capacity and cycling characteristics and can impart high energy density, and to provide the lithium secondary battery using the above complex oxide as the cathode active material. <P>SOLUTION: The lithium-manganese composite oxide is represented by general formula (1), Li<SB>x</SB>Mn<SB>2-y</SB>Me<SB>y</SB>O<SB>4-z</SB>(wherein Me is a metal element or transition metal element of an atomic number 11 or higher except manganese; 0<x<2.0; 0≤y≤0.6; and 0≤z<2.0). The lithium content at 8a site in Rietveld analysis of X-ray diffraction is 90% or more, and the purity of the composite oxide is 90% or higher. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lithium-manganese composite oxide, particularly a lithium composite oxide useful as a positive electrode active material having excellent energy density for a lithium secondary battery, and a lithium secondary battery using the same.

  In recent years, lithium secondary batteries have begun to be put into practical use as power sources for small electronic devices as consumer electronic devices become more portable and cordless. About this lithium secondary battery, since a report (nonpatent literature 1) that lithium cobalt oxide was useful as a positive electrode active material of a lithium secondary battery by Mizushima etc. in 1980 was made, it is related with lithium type complex oxide. Research and development has been actively carried out, and lithium cobaltate, lithium nickelate, lithium manganate, and the like are known as positive electrode active materials.

  Lithium manganate has been developed in various ways from the viewpoint of production cost because raw materials are cheaper than lithium cobaltate and lithium nickelate.

For example, LiMn 2 O 4 obtained by firing manganese dioxide and lithium carbonate having a (110) plane peak in the vicinity of a diffraction angle 2θ = 36.5 ° by X-ray diffraction at 400 to 600 ° C. is used as a positive electrode active material. (Patent Document 1), using Li 2 MnO 3 as an active material (Patent Document 2), Li x Mn 2 O 4 (1.025 ≦ x ≦ 1.185) as an active material (Patent Document 3) the Cr-containing LiMn 2 O 4 and the positive electrode active material (Patent Document 4), Li x M y Mn 2-y O 4 ( where, M is an element selected from IIIa or IIIb) composite oxide having a composition of Active material (Patent Document 5), acicular LiMn 2 O 4 (Patent Document 6), Li 1-x Mn 2 O 4 (0 ≦ x ≦ 1) and a composite oxide of Li 2 MnO 3 are activated. As a substance (Patent Document 7), lithium nitrate and manganese dioxide are mixed at 250 to 470 ° C., 50 To 800 ° C. in LiMn 2 O 4 obtained by firing two stages include (Patent Document 8), etc., but are also many proposals in other.

JP-A-1-173574 JP-A-1-209663 JP-A-2-270268 Japanese Patent Laid-Open No. 2-60056 JP-A-2-278661 JP-A-4-206354 JP-A-6-1111819 JP 7-245106 A Materials Research Brain "vol.115, pp.783-789 (1980)

However, this LiMn 2 O 4 or the like has a problem in cycle characteristics because the discharge capacity is remarkably lowered when charging and discharging are repeated, and when used in an operating region of 4.5 V to 3.5 V, the discharge capacity is several 10 There is a problem that the cycle is reduced to about half of the initial stage, and a 4V-class lithium secondary battery using lithium manganese oxide as a positive electrode active material is difficult to realize until now.

  Accordingly, an object of the present invention is to provide a lithium manganese composite oxide useful as a positive electrode active material for a lithium secondary battery that can provide a high energy density with excellent discharge capacity and cycle characteristics when used as a positive electrode active material for a lithium secondary battery. And a lithium secondary battery using the lithium manganese composite oxide as a positive electrode active material.

  The present inventors paid attention to the above-mentioned present situation, and as a result, the lithium content in the 8a site by the Rietveld analysis method by X-ray diffraction of the lithium manganese composite oxide is 90% or more, and the lithium manganese When the lithium manganese composite oxide having a composite oxide purity of 90% or more is used as a positive electrode active material of a lithium secondary battery, the present invention has been found to have a strong relationship with battery characteristics such as discharge capacity and cycle characteristics. Was completed.

That is, the present invention provides the following general formula (1)
Li x Mn 2-y Me y O 4-z (1)
(In the formula, Me represents a metal element or transition metal element having an atomic number of 11 or more other than manganese, x is in the range of 0 <x <2.0, and y is in the range of 0 ≦ y ≦ 0.6. Z is in the range of 0 ≦ z <2.0)
In the lithium manganese composite oxide represented by the following formula, the lithium content in the 8a site by the Rietveld analysis method by X-ray diffraction is 90% or more, and the purity of the lithium manganese composite oxide is 90% or more. The lithium-manganese composite oxide is characterized.

  Furthermore, the present invention relates to a positive electrode active material for a lithium secondary battery, comprising the lithium manganese composite oxide as a main component.

  The present invention also relates to a lithium secondary battery using the lithium secondary battery positive electrode active material.

  According to the present invention, a lithium manganese composite oxide having a lithium content in the 8a site of 90% or more and a lithium manganese composite oxide of 90% or more can be obtained. When used as a substance, it is possible to provide a positive electrode active material for a secondary battery that provides a high energy density with excellent discharge capacity and cycle characteristics.

Hereinafter, the present invention will be described in detail.
The lithium manganese composite oxide according to the present invention has the following general formula (1):
Li x Mn 2-y Me y O 4-z (1)
(In the formula, Me represents a metal element or transition metal element having an atomic number of 11 or more other than manganese, x is in the range of 0 <x <2.0, and y is in the range of 0 ≦ y ≦ 0.6. Z is in the range of 0 ≦ z <2.0)
(1) The lithium content in the 8a site according to the Rietveld analysis method by X-ray diffraction is 90% or more, and (2) the purity of the lithium manganese composite oxide is 90%. This is the characteristic of the configuration.

  The Rietveld analysis method by X-ray diffraction is described in the document “Material analysis by powder X-ray diffraction” (pages 108 to 122, June 1, 1993, published by Kodansha Scientific Co., Ltd.). This method refines functions such as lattice constants and structure parameters of all pattern data of powder X-ray diffraction, and performs analysis. The procedure of the Rietveld analysis method is as shown in the evaluation method of Table 1 described later.

  One feature of the lithium composite oxide according to the present invention is that, as described above, (1) the lithium content in the 8a site by the Rietveld analysis by X-ray diffraction is 90% or more, preferably 95 to 100%. There are almost no crystal defects in the lithium manganese composite oxide. When the lithium content in the 8a site is less than 90%, metal ions other than lithium, such as manganese ions, are mixed into the 8a site surface of the lithium manganese composite oxide, and therefore the crystal structure tends to be irregularly arranged. This is not preferable because crystal defects are generated.

  The lithium manganese composite oxide according to the present invention is preferably (2) the purity of the lithium manganese composite oxide is 90% or more, preferably 97 to 100%. This is not preferable because the amount of raw materials increases.

  As described above, the lithium manganese composite oxide according to the present invention has a lithium content of less than 90% in the 8a site, and when the purity of the lithium manganese composite oxide is less than 90%, Since the above defects occur, it is not preferable to apply the lithium manganese composite oxide to the positive electrode active material of the lithium secondary battery because the discharge capacity and the cycle characteristics are lowered.

  The lithium manganese composite oxide according to the present invention has a spinel structure.

  The lithium manganese composite oxide according to the present invention is represented by the above general formula (1) and has the above characteristics. Therefore, the lithium manganese composite oxide of the present invention is not only lithium manganate having the above characteristics, but also a part of manganese (Mn) in the crystal structure of lithium manganate is replaced with atoms other than manganese. Compounds substituted with a metal element or transition metal element of No. 11 or more, for example, sodium (Na), magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), cobalt (Co ), Iron (Fe), copper (Cu), zinc (Zn), yttrium (Y), morbden (Mo), and the like. Lithium ion intercalation and deintercalation reactions can be carried out more smoothly and in a higher potential range.

Next, the manufacturing method of the lithium manganese composite oxide of this invention is demonstrated.
In the method for producing a lithium manganese composite oxide according to the present invention, the atomic ratio of a manganese element or a metal element having a atomic number of 11 or more excluding manganese and manganese (hereinafter referred to as “metal or transition metal”) is excluded. Each of 2-y and y (wherein y is in the range of 0 ≦ y ≦ 0.6), oxides of metal elements or transition metal elements having an atomic number of 11 or more excluding manganese and manganese, water X in terms of atomic ratio with respect to a starting material composed of one or more selected from the group consisting of oxides, carbonates, nitrates and organic acid salts (wherein x is 0 <x <2.0) The lithium-manganese composite oxide represented by the general formula (1) is produced by adding and firing the lithium raw material (within the range of 2) at least twice.

  The lithium raw material, manganese raw material and metal or transition metal raw material used as starting materials may be any industrially available materials, such as oxides, hydroxides, carbonates of the respective metals, Examples thereof include nitrates and organic acid salts.

  In addition, the starting material used in the present invention is not limited to any production history, but it is preferable to select a starting material having as little impurity content as possible.

  When adding the total amount of the lithium raw material used in the reaction system, for example, in two portions, for example, 2/3 of the total amount is first added and fired, and 1/3 is added the second time. Add and bake. In addition, there is a method of adding ½ and ½ equally at the beginning. In addition, when it is divided into three times, it is a method of adding in 4/7, 2/7, 1/7 of the total amount, or a method of dividing equally into 1/3, 1/3, 1/3, etc. It is.

  An example of the method for producing a lithium manganese composite oxide of the present invention is as follows. A predetermined amount of manganese raw material or manganese raw material is mixed with 4/7 parts by weight of a required amount of lithium raw material with respect to the amount of metal or transition metal raw material. And calcining at 400 to 500 ° C. for 5 to 24 hours. At this time, when the mixing is performed in a wet manner, a manganese raw material or a manganese raw material and a metal or a transition metal raw material are mixed in a lithium raw material aqueous solution, and the mixture is stirred to remove moisture and dried.

  After firing, it is cooled, mixed again, ground if necessary, and fired again. At this time, the firing temperature is preferably higher than the previous firing temperature. For example, firing is performed at 500 to 1100 ° C. for 5 to 24 hours. With this operation pattern as one time, if the firing is performed twice, the above-described firing operation is repeated by adding the remaining portion of the raw material, and if the firing is performed three times, the addition of the raw material and the firing operation are repeated two more times.

  In addition, as another firing method, first, a predetermined amount of manganese raw material or manganese raw material and 4/7 parts by weight of a required amount of lithium raw material with respect to the amount of metal or transition metal raw material are mixed in a dry process, and 400 to 500 Bake at 5 ° C. for 5-24 hours. At this time, the mixing may be either dry or wet as described above. After firing, the mixture is cooled, 2/7 parts by weight of the lithium raw material is added and mixed again, and pulverized and mixed as necessary. Then, it is similarly fired at 500 to 1100 ° C. for 5 to 24 hours. At this time, the firing temperature is preferably higher than the first firing temperature. After the completion of firing, the mixture is cooled by a normal method, the remainder of the lithium raw material, that is, 1/7 parts by weight, is added, mixed again, and pulverized and mixed as necessary. Next, it is fired again at 400 to 500 ° C. for about 5 to 24 hours. After firing, the mixture is cooled, mixed, and pulverized and mixed as necessary to obtain a lithium manganese composite oxide.

  In this method, in the case of two-time firing, the above method may be performed under the first and second firing conditions.

  The firing atmosphere in the above production method is in the air or in an oxygen atmosphere, but is preferably in an oxygen atmosphere.

  In addition, when the lithium manganese composite oxide is produced as described above, by adding the lithium raw material in a divided manner, the lithium manganese composite oxide can be obtained more than when the entire amount of the lithium raw material is added and fired at once. Cycle characteristics are improved.

  The compounding ratio of lithium raw material, manganese raw material and metal other than manganese or transition metal raw material is such that the atomic ratio of lithium (Li), manganese (Mn) and metal other than manganese or transition metal (Me) is x (Li), 2 -Y (Mn), y (Me) (where x is in the range 0 <x <2.0 and y is in the range 0≤y≤0.6). The For example, when the blending ratio is set near 2 as the (Mn or Mn + Me) / Li ratio, the blending ratio is allowed to have a width of around 2 depending on the properties of the raw materials and firing conditions.

  The reaction is usually gradually cooled in a furnace, but preferably cooled in air, and may be further quenched in cold water.

  Further, the above manganese raw material and lithium raw material, or manganese raw material, metal or transition metal raw material and lithium raw material are uniformly mixed and pressure-molded to produce a molded body, and this molded body is fired in the same manner as above. Alternatively, a method of cooling after firing may be used.

  The lithium manganese composite oxide of the present invention produced by the above method has a lithium content of 90% or more in the 8a site according to the Rietveld analysis method by X-ray diffraction, and has very few defects in the crystal. The purity of the oxide is 90% or more and there are few impurities. Such compounds have a spinel type.

  Moreover, the lithium manganese composite oxide of the present invention obtained by the above method is useful as a positive electrode active material for a lithium secondary battery.

  Furthermore, a positive electrode plate for a lithium secondary battery can be obtained by coating a conductive substrate with a lithium secondary battery positive electrode active material containing the lithium manganese composite oxide of the present invention as a main component. By using it, a lithium secondary battery can be provided.

Next, an example of a basic configuration of the lithium secondary battery according to the present invention is shown.
The lithium manganese composite compound powder of the present invention produced as described above is used as a main component, and graphite powder, polyvinylidene fluoride, etc. are mixed and processed into a positive electrode agent (lithium secondary battery positive electrode active material), which is used as an organic solvent. Disperse to prepare a kneaded paste. The kneaded paste is applied to a conductive substrate such as an aluminum foil, dried, pressed and cut into an appropriate shape to obtain a positive electrode plate.

  Conventionally, it is difficult to synthesize lithium manganate used as a positive electrode active material for a lithium secondary battery. As a result, the obtained lithium manganate has a small lithium content at the 8a site and a large lithium deficiency, which adversely affects battery performance. Was exerting.

  The lithium manganese composite oxide of the present invention is a very stoichiometric compound with few defects in the crystal. The defects in the crystals in such compounds can be confirmed by Rietveld analysis by X-ray diffraction, which means that the lithium content in the 8a site in the crystal structure is 90% or more and the purity of the lithium manganese composite oxide is high. For example, when used as a positive electrode active material of a lithium secondary battery, it has a high energy density with excellent discharge capacity and excellent cycle characteristics.

Embodiments according to the present invention will be described in detail below.
Production Example 1
8.69 g of electrolytically synthesized manganese dioxide and 1.06 g of lithium carbonate are pulverized and mixed, put in an alumina crucible, heated to 450 ° C. at 100 ° C./hour, then fired in an air atmosphere for 8 hours, at 100 ° C./hour. Cooled to room temperature. Next, after the obtained lithium manganese oxide was pulverized, it was baked at 725 ° C. for 8 hours. The heating rate and cooling rate at this time were 100 ° C./hour.
To the lithium manganese oxide thus obtained, 0.53 g of lithium carbonate was further added and pulverized and mixed, and baked at 450 ° C. for 8 hours in the same manner as described above, and then baked again at 725 ° C. for 8 hours after cooling and pulverization. .
Further, 0.26 g of lithium carbonate was added to the obtained lithium manganese oxide and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization.
The lithium manganese composite oxide thus obtained had a composition of LiMn 2 O 4 . Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this lithium manganese composite oxide. Moreover, the result of the X-ray diffraction of the obtained lithium manganese composite oxide is shown in FIG.

Production Example 2
8.69 g of electrolytically synthesized manganese dioxide and 1.85 g of lithium carbonate were pulverized and mixed, put in an alumina crucible, heated to 450 ° C. at 100 ° C./hour, then baked in an air atmosphere for 12 hours, at 100 ° C./hour. Cooled to room temperature. The obtained lithium manganese oxide was pulverized and then fired again at 725 ° C. for 12 hours. The heating rate and cooling rate at this time were 100 ° C./hour.
Lithium manganese oxide thus obtained was mixed with 0.62 g of lithium carbonate, pulverized and mixed, baked at 450 ° C. for 12 hours in the same manner as described above, and baked again at 725 ° C. for 12 hours after cooling and pulverization. The obtained lithium manganese composite oxide had a composition of LiMn 2 O 4 . Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this compound.

Production Example 3
11.50 g of manganese carbonate and 1.20 g of lithium hydroxide monohydrate were pulverized and mixed, put in an alumina crucible, heated to 450 ° C. at 100 ° C./hour, and then fired in an air atmosphere for 8 hours. / Hour at room temperature. The obtained lithium manganese oxide was pulverized and then fired again at 725 ° C. for 8 hours. The heating rate and cooling rate at this time were 100 ° C./hour.
To the lithium manganese oxide thus obtained, 0.60 g of lithium hydroxide monohydrate was added and ground and mixed, fired at 450 ° C. for 8 hours as before, cooled and ground again, and again at 725 ° C. for 8 hours. Firing was performed.
Further, 0.30 g of lithium hydroxide monohydrate was added to the obtained lithium manganese oxide and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and then baked again at 725 ° C. for 8 hours. went. The obtained lithium manganese composite oxide had a composition of LiMn 2 O 4 . Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this compound.

Production Example 4
8.26 g of electrolytically synthesized manganese dioxide, 3.90 g of aluminum hydroxide and 1.06 g of lithium carbonate are ground and mixed, put in an alumina crucible, heated to 450 ° C. at 100 ° C./hour, and then fired in an air atmosphere for 8 hours. And cooled to room temperature at 100 ° C./hour. The obtained lithium manganese composite oxide was pulverized and then fired again at 725 ° C. for 8 hours. The heating rate and cooling rate at this time were 100 ° C./hour.
0.53 g of lithium carbonate was added to the lithium manganese composite oxide thus obtained and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization. .
Further, 0.26 g of lithium carbonate was added to the obtained lithium manganese composite oxide and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization. The obtained lithium manganese composite oxide had a composition of LiMn 1.9 Al 0.1 O 4 . Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this compound. Moreover, the result of the X-ray diffraction of the obtained lithium manganese composite oxide is shown in FIG.

Production Example 5
8.26 g of electrolytically synthesized manganese dioxide, 4.65 g of cobalt hydroxide and 1.06 g of lithium carbonate are ground and mixed, put in an alumina crucible, heated to 450 ° C. at 100 ° C./hour, and then fired in an air atmosphere for 8 hours. And cooled to room temperature at 100 ° C./hour. The obtained lithium manganese composite oxide was pulverized and then fired again at 725 ° C. for 8 hours. The heating rate and cooling rate at this time were 100 ° C./hour.
0.53 g of lithium carbonate was added to the lithium manganese composite oxide thus obtained and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization. .
Further, 0.26 g of lithium carbonate was added to the obtained lithium manganese composite oxide and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization. The obtained lithium manganese composite oxide had a composition of LiMn 1.9 Co 0.1 O 4 . Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this compound. Moreover, the result of the X-ray diffraction of the obtained lithium manganese composite oxide is shown in FIG.

Production Example 6
8.26 g of electrolytically synthesized manganese dioxide, 4.64 g of nickel hydroxide, and 1.06 g of lithium carbonate are ground and mixed, put in an alumina crucible, heated to 450 ° C. at 100 ° C./hour, and then fired in an air atmosphere for 8 hours. And cooled to room temperature at 100 ° C./hour. The obtained lithium manganese composite oxide was pulverized and then fired again at 725 ° C. for 8 hours. The heating rate and cooling rate at this time were 100 ° C./hour.
0.53 g of lithium carbonate was added to the lithium manganese composite oxide thus obtained and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization. .
Further, 0.26 g of lithium carbonate was added to the obtained lithium manganese composite oxide and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization. The obtained lithium manganese composite oxide had a composition of LiMn 1.9 Ni 0.4 O 4 . Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this compound.

Production Example 7
8.69 g of electrolytically synthesized manganese dioxide and 0.62 g of lithium carbonate were pulverized and mixed, put in an alumina crucible, heated to 450 ° C. at 100 ° C./hour, then fired in an air atmosphere for 8 hours, at 100 ° C./hour. Cooled to room temperature. The obtained lithium manganese oxide is pulverized and then fired again at 725 ° C. for 8 hours. The heating rate and cooling rate at this time were 100 ° C./hour.
0.62 g of lithium carbonate was added to the lithium manganese oxide thus obtained, and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization.
Further, 0.62 g of lithium carbonate was added to the obtained lithium manganese oxide and pulverized and mixed. The mixture was baked at 450 ° C. for 8 hours in the same manner as described above, and baked again at 725 ° C. for 8 hours after cooling and pulverization. The obtained lithium manganese composite oxide had a composition of LiMn 2 O 4 . Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this compound.

Production Example 8
A lithium manganese composite oxide was obtained in the same manner as in Example 1 except that firing in the air atmosphere of Example 1 was performed in an oxygen atmosphere. Table 1 shows the lithium content and purity, initial capacity, and cycle characteristics of the 8a site of this compound.

(1) Production of lithium secondary battery:
70% by weight of the lithium manganese composite oxide produced as described above, 20% by weight of graphite powder, and 10% by weight of polyvinylidene fluoride were mixed to prepare a positive electrode agent, which was dispersed in 2-methylpyrrolidone to prepare a kneaded paste. . The kneaded paste was applied to an aluminum foil, dried, pressed with a pressure of 2 ton / cm 2 , and punched into a 2 cm square to obtain a positive electrode plate.
Using this positive electrode plate, a lithium secondary battery was manufactured using each member such as a separator, a negative electrode, a current collector plate, a mounting bracket, an external terminal, and an electrolytic solution. Among these, carbon having a high crystallinity was used for the negative electrode, and 1 mol of LiClO 4 was dissolved in 1 liter of a 1: 1 mixture of diethyl carbonate and ethylene carbonate as the electrolyte.

(2) Performance evaluation of lithium secondary battery:
The produced lithium secondary battery was operated, and the initial discharge capacity and capacity retention were measured to evaluate the battery performance. The results are shown in Table 1 in comparison with the firing conditions, the lithium content in the 8a site by the Rietveld analysis method by X-ray diffraction, and the purity of the lithium manganese composite oxide.

(3) Evaluation method The procedure of the Rietveld analysis method is as follows.
First, the Li content in the compound was measured by ICP analysis, and the Mn content in the compound was measured by the following B. Next, after obtaining the valence of Mn, the following Rietveld analysis method was performed.
(1) Index the powder X-ray diffraction pattern peaks to narrow down the space group;
(2) Refine the lattice constant by least squares method or Pawley method;
(3) Estimating the approximate atomic arrangement from crystallographic knowledge and chemical composition;
(4) Simulate a powder X-ray diffraction pattern based on the structural model constructed in (3);
(5) Rietveld analysis is performed and the lithium content in the 8a site is measured.

B. Determination of purity of lithium manganese composite oxide The obtained sample is dissolved in mineral acid such as hydrochloric acid, Rossell salt is added, and the pH is adjusted to 8 with NH 3 —NH 4 Cl buffer. Further, ascorbic acid was added, and titration was performed by EDTA with an Eriochrome Black T (BT) indicator to measure the total manganese amount. From this value, the purity of LiMn 2 O 4 was converted. (Direct titration with BT indicator "Chelate titration method, pages 342-344, Ueno, Minamiedo Publishing, first edition on June 15, 1951)

C. Discharge capacity The discharge capacity was measured by repeatedly charging and discharging to 3.0 V after charging to 4.3 V at 1 mA / cm 2 with respect to the positive electrode. It was calculated by the following formula.
Cycle characteristics (%) = (discharge capacity at 10th cycle / discharge capacity at 1st cycle)
× 100

FIG. 4 is a diagram showing the results of X-ray diffraction of the lithium manganese composite oxide obtained in Production Example 1. It is a figure which shows the result of the X-ray diffraction of the lithium manganese complex oxide obtained by manufacture example 4. 6 is a diagram showing the results of X-ray diffraction of the lithium manganese composite oxide obtained in Production Example 5. FIG.

Claims (4)

  1. The following general formula (1)
    Li x Mn 2-y Me y O 4-z (1)
    (In the formula, Me represents a metal element or transition metal element having an atomic number of 11 or more other than manganese, x is in the range of 0 <x <2.0, and y is in the range of 0 ≦ y ≦ 0.6. Z is in the range of 0 ≦ z <2.0)
    In the lithium manganese composite oxide represented by the following formula, the lithium content in the 8a site by the Rietveld analysis method by X-ray diffraction is 90% or more, and the purity of the lithium manganese composite oxide is 90% or more. A featured lithium manganese composite oxide.
  2.   The lithium manganese composite oxide according to claim 1, wherein the lithium manganese composite oxide has a spinel structure.
  3.   A lithium secondary battery positive electrode active material comprising the lithium manganese composite oxide according to claim 1 as a main component.
  4.   The lithium secondary battery using the lithium secondary battery positive electrode active material of Claim 3.
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WO2013157857A1 (en) * 2012-04-20 2013-10-24 주식회사 엘지화학 Electrolyte for secondary battery and lithium secondary battery including same
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Publication number Priority date Publication date Assignee Title
WO2013157883A1 (en) * 2012-04-20 2013-10-24 주식회사 엘지화학 Electrolyte for lithium secondary battery and lithium secondary battery containing same
WO2013157857A1 (en) * 2012-04-20 2013-10-24 주식회사 엘지화학 Electrolyte for secondary battery and lithium secondary battery including same
WO2013157867A1 (en) * 2012-04-20 2013-10-24 주식회사 엘지화학 Lithium secondary battery having improved rate characteristics
US9634356B2 (en) 2012-04-20 2017-04-25 Lg Chem, Ltd. Electrolyte for secondary battery and lithium secondary battery including the same
US9954254B2 (en) 2012-04-20 2018-04-24 Lg Chem, Ltd. Electrolyte for lithium secondary battery and lithium secondary battery including the same
US10170796B2 (en) 2012-04-20 2019-01-01 Lg Chem, Ltd. Lithium secondary battery of improved rate capability with cathode containing nickel manganese complex oxide for high-voltage applications

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