JP2005135861A5 - - Google Patents

Description

Production of 3d transition metal oxides for negative electrode active materials in non-aqueous electrolyte electrochemical cells Method and negative electrode active material

The present invention relates to negative active material for a manufacturing method and a non-aqueous electrolyte electrochemical cell of the oxide of the negative electrode active material for a 3d transition metal of the non-aqueous electrolyte electrochemical cell.

  In recent years, with the development of portable electronic devices such as mobile phones and video cameras, development of high-performance batteries is desired. Lithium batteries using lithium transition metal composite oxide for the positive electrode and graphite and amorphous carbon for the negative electrode are widely put into practical use as non-aqueous electrolyte batteries with high operating voltage and high energy density.

  Research on lithium metals and lithium alloys having a theoretical capacity larger than that of carbon materials has been actively conducted. However, since lithium metal or lithium alloy has a large volume change due to charge and discharge, and has many problems in terms of cycle life and safety, lithium secondary batteries using metal lithium and lithium alloys are not suitable. Not yet commercialized.

On the other hand, although transition metal oxides are used as positive electrode active materials, it has been reported that they can also be used as negative electrode active materials. In Patent Document 1, iron _{oxide, FeO, Fe 2 O 3,} Fe 3 O 4, cobalt oxide, CoO, have published techniques using _Co 2 _{O 3} and _Co 3 _{O 4} in the negative electrode active material. Further, Patent Document 2, technology using an oxide of a transition metal containing no or lithium containing various lithium in the negative electrode active material, for example, _{Li x M q V 1-q} O j ( although, M is a transition Represents a metal, x is in the range of 0.17 to 11.25, q is in the range of 0 to 0.7, and j is in the range of 1.3 to 4.1). containing transition metal oxides and their manufacturing techniques are disclosed. Further, in Patent Document 3, it has published the particle size of the transition metal oxide anode active material, the firing conditions and electrochemically technique of inserting lithium ions.

Non-Patent Document 1 discloses the characteristics and reaction mechanism of transition metal oxides CoO, Co ₃ O ₄ , NiO, FeO, and Cu ₂ O as negative electrode active materials. These oxides show a discharge capacity greater than 700 mAh / g, transition metal generation and Nanosa size of Li 2 _O with the charge was confirmed. Further, the cycle performance of the cobalt oxide was good.

Furthermore, Non-Patent Document 2 describes a technique for producing a lithium-containing transition metal oxide and sulfide by a mechanical milling method. Maximum initial discharge capacity of the resulting mixture is 600 mAh / g or more, but were those cycle performance was inferior.

JP-A-3-291862 Japanese Patent No. 3242751 JP-A-7-14581 Nature 407, P496-499 (2000) Electrochemical and Solid-state Letters, Volume 5, A70-A73 (2002)

Cobalt oxide is showed excellent cycle performance, high discharge potential, and since the cobalt resource problems exist, high energy density, are not ideal candidates as inexpensive negative electrode active material. The charge / discharge behavior of NiO is similar to that of CoO, but the cycle performance is inferior. The charge / discharge characteristics of manganese oxide were not disclosed.

Therefore, that the present invention is to provide a discharge capacity, the production method and the negative electrode active material quality of the oxide of the 3d transition metals as a negative electrode active material for a charge and discharge potential and cycle performance is excellent both nonaqueous electrolytic electrolyte electrochemical cell It is an object.

As a result of intensive studies, we have found that oxides in which various 3d transition metals are dissolved have excellent discharge potential, cycle performance and discharge capacity.

The invention of claim 1 is the manufacturing method of the oxide of the negative electrode active material for a 3d transition metal of the non-aqueous electrolyte electrochemical cell to oxidize the at least one metal hydroxide selected from the 3d transition metals in aqueous solutions The first step and the second step of heat-treating the oxyhydroxide obtained in the first step at a temperature of 350 ° C. or higher and 600 ° C. or lower are characterized.

According to a second aspect of the present invention, in the method for producing a 3d transition metal oxide for a negative electrode active material of the non-aqueous electrolyte electrochemical cell , the 3d transition metal oxide obtained in the second step is contained in an organic electrolyte. characterized in that through the third step of electrochemically reduced.

The invention according to claim 3, the negative electrode active material for a non-aqueous electrolyte electrochemical cell, the general formula _{Li x Ni a Co b Mn 1} -a-b O 2 ( However, a: b: c = 1 : 1: 1~ 3: 1: 1 is the table (molar ratio)), 5 ° in X-ray diffraction using CuKα ray <2θ <25 ° and 40 ° <FWHM of the diffraction peak appearing at 2 [Theta] <50 ° is 5 ° ( 2θ) or more .

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According to the invention of claim 1, a 3d transition metal oxide having a high atomic oxygen content and a low hydrogen content in the compound can be obtained . In the 3d transition metal oxide produced in this way , the active oxygen content is high, and as shown in Equation 1, the discharge capacity of the 3d transition metal oxide is proportional to the active oxygen content. discharge capacity of the 3d transition metal oxides prepared from the high and that Do. And since it heat-processes at medium temperature, since there is little loss of active oxygen and there exists an optimal particle size and crystal state, the outstanding cycling performance can be anticipated.

Me _x O _y + 2yLi + 2ye ⁻ = xMe + yLi ₂ O (formula 1)
However, in Formula 1, Me shall represent a 3d transition metal.

According to the invention of claim 2, an amorphous 3d transition metal oxide is obtained.

According to the invention of claim 3, further to the use of this active material in the negative electrode of the nonaqueous electrolyte electrochemical cell, the improvement of cycle performance of the nonaqueous electrolyte electrochemical cell can be expected.

  (Delete)

Thus, according to the present invention, a negative electrode material for a non-aqueous electrolyte electrochemical cell having a high energy density and a long cycle life can be obtained. By using the 3d transition metal oxide was prepared by the method of the present invention the negative electrode active material, the discharge capacity is high, it is possible to cycle performance and discharge potential obtain both excellent non-aqueous electrolyte electrochemical cell.

The present invention relates to a negative electrode active material for a non-aqueous electrolyte electrochemical cell, a method for producing the same, and a non-aqueous electrolyte electrochemical cell using this active material . The nonaqueous electrolyte electrochemical cell of the present invention refers to a lithium battery, a lithium secondary battery and / or an electrochemical capacitor.

The present inventor has focused on transition metal oxides, the results that have extensive research, at least one metal of the water oxides selected from 3d transition metals in aqueous solution combination and ratio further synthesis conditions of the various elements A first step of oxidizing, and a 3d transition metal oxide obtained by passing through a second step of heat-treating the oxyhydroxide obtained in the first step at a temperature of 350 ° C. or higher and 600 ° C. or lower However, it has been found that it has characteristics such as a large discharge capacity, continuous discharge potential, and excellent cycle performance as a negative electrode active material for non-aqueous electrolyte electrochemical cells.

Here, “3d transition metal” refers to Ni, Co, Mn, Fe, V, Zn, and Cu. As the 3d transition metal oxide, only one type may be selected from these, or for example, a plurality of types such as Ni, Co, and Mn may be selected.

Further, these 3d transition metal oxides may further contain Li. Preferably, a 3d transition metal oxide obtained by heat-treating an oxyhydroxide containing Ni, Co, and Mn at a temperature of 350 ° C. or more and 600 ° C. or less exhibits the performance improvement effect of the active material more remarkably.

In the present invention , a hydroxide in which the average oxidation number of the 3d transition metal is less than 3 is oxidized in the first step, and the 3d transition metal oxyhydroxide obtained in the first step is converted into the average oxidation number of the transition metal. The effect of the invention can be further extracted by oxidizing until the value becomes 3 or more.

In a first step, in order to form a solid solution 3d transition metals of 3d transition metal oxide at an atomic level, coprecipitation is preferred. The starting 3d transition metal hydroxide is dispersed in an alkaline solution, oxidized with an oxidizing agent at a temperature of 50 ° C., and the precipitate is filtered and dried to obtain an oxyhydroxide.

On the other hand, in the first step, the 3d transition metal hydroxide compound is dispersed in aqueous LiOH solution and is oxidized with an oxidizing agent at a temperature of 80 ° C., oxyhydroxide first part of the protons have been exchanged with lithium ion Is obtained. When Mn and Fe are contained in the 3d transition metal, it is desirable to oxidize while protecting nitrogen and argon gas. This not only provides an oxyhydroxide in which each element is in solid solution, but also avoids the formation of “inert” carbonates.

Further, the amount of lithium ions introduced into the 3d transition metal oxide in this way is limited to the equilibrium constant of the ion exchange reaction . For example, Li / Me (Me is not at least one transition metal)> 0.86 der Ru lithium-containing transition metal oxide is obtained.

  The kind of oxidizing agent is not particularly limited. Preferably, a step of using at least one selected from oxygen, ozone or peroxodisulfate, or hypochlorite, permanganate, dichromate, bromine, and chlorine may be included. Further, not only a chemical oxidation method using an oxidizing agent but also an electrochemical method may be used.

As described above, the oxyhydroxide obtained in the first step can be used as it is for the negative electrode active material of the nonaqueous electrolyte electrochemical cell. When the above compound is further heat-treated in the second step , various electrochemical performances can be expected to be improved. Moreover, the heat processing temperature is defined using the measurement result of TG-DTA. That is, the heat treatment temperature range was defined with the initial temperature at which the initial crystal water and structural water were removed as the lower limit, and the oxygen release and crystallization development temperatures as upper limits. Further, air and oxygen are desirable as the heat treatment atmosphere.

Examples of the 3d transition metal oxide used in the present invention include those produced from the above transition metal oxyhydroxides, such as CoO, Co ₂ O ₃ , CoOOH, NiOOH, V ₂ O ₃ , V ₂ O ₄ , Examples thereof include V ₂ O ₅ , MnO, MnO ₂ , Mn ₃ O ₄ , MnOOH, FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , FeOOH, CuO, Cu ₂ O, ZnO and the like.

  Further, a solid solution containing two or more 3d transition metal elements is more desirable. Furthermore, typical non-metallic elements such as N, P, F, Cl, Br, I, and S may be included in the above substance. As the crystal structure, those from crystalline to amorphous can be used, but amorphous is better for high rate discharge. Further, powders, membranes, fibers, and porous bodies can be used.

  These materials can be used by forming a composite with a carbon material. Examples of the composite with the carbon material include those obtained by coating the surface of these materials with a carbon material, those obtained by mixing and granulating the carbon material, and those obtained by coating the surface with the carbon material. As a method of coating with a carbon material, a CVD method in which benzene, toluene, xylene, methane, propane, butane, ethylene, acetylene or the like is decomposed in a gas phase as a carbon source and chemically deposited on the particle surface, pitch, It can be produced by a method using a thermoplastic resin such as tar or furfuryl alcohol and firing afterwards, or a method using a mechanochemical reaction. The CVD method is desirable.

Further, as a method for introducing lithium into the 3d transition metal oxide, there is a method of short-circuiting the electrode and the metal lithium electrode containing a 3d transition metal oxide in the electrolyte. In addition, when an electrode including a 3d transition metal oxide, a lithium alloy powder, and a lithium-containing transition metal nitride (for example, Li _2.5 Co _0.5 N powder) is produced, A battery reaction occurs and a lithium-containing transition metal oxide can be created. Moreover, a lithium-containing transition metal oxide can also be produced by bringing a transition metal oxide into contact with an organic solution of lithium, for example, an organic solution such as butyl lithium. Moreover, the the 3d transition metal oxide electrode, an organic electrolyte, by the potential range of the lithium reference is electrochemically reduced to 0～0.3V, making a lithium-containing transition metal oxide Can do.

As the conductive material of the 3d transition metal oxide negative electrode active material, acetylene black, amorphous carbon, graphite powder, carbon nanotube, carbon nanophone, and the like are desirable. In order to mix the conductive material and the transition metal oxide well, a mechanical milling method is desirable as a mixing method.

  Cu, Ni, Ti, Al, stainless steel, etc. can be used as the current collector material. Examples of the form include a three-dimensional structure such as a sheet, a mesh, and a foam.

As a positive electrode material used in the nonaqueous electrolyte battery of the present invention, LiCoO ₂ , LiNiO ₂ , MnO ₂ , LiMn ₂ O _{4 and} other compositional formulas Li _x MO ₂ or Li _y M ₂ O ₄ (where M is a transition metal) , 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), oxides having tunnel-like holes, metal chalcogenides having a layered structure, and the like can be used.

Further, such LiFePO ₄ as an active material _LiNi 0.5 _Mn 1.5 _{O 4} and olivine material 5V-class can be used. Furthermore, when a lithium-containing 3d transition metal oxide is used as the negative electrode active material, TiS ₂ , MoS ₂ , V ₂ O ₅ , MnO ₂ or the like without a lithium source can be used for the positive electrode.

  The non-aqueous electrolyte used in the non-aqueous electrolyte battery of the present invention may be a non-aqueous electrolyte, a polymer electrolyte, or a solid electrolyte. Solvents used for the non-aqueous electrolyte include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane. And polar solvents such as 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane and methyl acetate, and mixed solvents thereof.

Moreover, as a solute of the nonaqueous electrolytic solution, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiSCN, LiCF ₃ CO ₂ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF _2). Illustrative are salts such as CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ and LiN (COCF ₂ CF ₃ ) ₂ or mixtures thereof.

Hereinafter, the method for synthesizing the negative electrode active material of the present invention and the nonaqueous electrolyte secondary battery equipped with the negative electrode active material of the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples.

[ Comparative Example 1]
[ Comparative Example 1-1]
In a first step, the _{Ni 1/3 Co 1/3 Mn 1/3} (OH) 2 for Ni / Co / Mn molar ratio 1/1/1 was dispersed in aqueous LiOH solution 4M, to a temperature of 80 ° C. 1.2 equivalents of NaClO was added, and the mixture was stirred for 6 hours while maintaining 80 ° C. to be oxidized. Subsequently, the solution was suction filtered and further dried at 65 ° C. The resulting Ni, Co and 3d transition metal oxyhydroxide oxides, including a Mn of _{(Ni 1/3 Co 1/3 Mn 1/3 OOH} ) as a negative electrode active material A11, the negative electrode active substance 86 wt%, acetylene black 5 wt% as a conductive material, polyvinylidene difluoride mold vinylidene 9 wt% and a (n- methyl-2-pyrrolidone solution of polyvinylidene difluoride) were mixed in a dry room as a binder in the paste Then, after applying to the foamed nickel of the current collector, it was vacuum dried at 70 ° C. and pressed to produce a negative electrode plate having a thickness of 260 μm and a size of 10 mm × 20 mm.

Two lithium metal plates having the same size as the counter electrode were used for one negative electrode plate. Similarly, metallic lithium was used as a reference electrode. The negative electrode active material electrode according to the present invention was evaluated using 50 ml of a mixed solvent of ethylene carbonate and diethyl carbonate containing 1 M lithium perchlorate as the electrolytic solution. The charging / discharging conditions were charged at a constant current of 0.25 mA / cm ² up to 0.02 V on a lithium basis, and discharging was performed up to 3.0 V at a similar current density. The charge / discharge electricity amount and the capacity retention ratio after 20 cycles are shown in Table 1.

[ Comparative Example 1-2]
The present invention is similar to Comparative Example 1-1 except that in the first step, Ni _1/2 Co _1/4 Mn _1/4 (OH) ₂ having a Ni / Co / Mn molar ratio of 2/1/1 was used. Negative electrode active material A12 (Ni _1/2 Co _1/4 Mn _1/4 OOH). Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 1-3]
In the first step, the present invention is the same as Comparative Example 1-1 except that Ni _2/5 Co _1/5 Mn _1/5 (OH) ₂ having a Ni / Co / Mn molar ratio of 3/1/1 is used. Negative electrode active material A13 (Ni _2/5 Co _1/5 Mn _1/5 OOH) was prepared. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 2]
The active material obtained in Comparative Example 1 was further heat-treated at 150 ° C.

[ Comparative Example 2-1]
A negative electrode active material A21 of the present invention was produced in the same manner as Comparative Example 1-1 except that the active material A11 of Comparative Example 1-1 was further subjected to vacuum heat treatment at 150 ° C. for 5 hours. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 2-2]
A negative electrode active material A22 of the present invention was produced in the same manner as in Comparative Example 1-2 except that the active material A12 of Comparative Example 1-2 was further subjected to a vacuum heat treatment at 150 ° C. for 5 hours. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 2-3]
A negative electrode active material A23 of the present invention was produced in the same manner as in Comparative Example 1-3, except that the active material A13 of Comparative Example 1-3 was further subjected to a vacuum heat treatment at 150 ° C. for 5 hours. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[Example 1 ]
TG-DTA measurement was performed on the active material obtained in Comparative Example 1. The result is shown in FIG. All samples showed significant weight loss at a temperature of 350 ° C. A small weight loss was observed in a high temperature region, for example, a temperature of 650 ° C. or higher. Therefore, the treatment temperatures at medium and high temperatures were set to 350 ° C., 400 ° C., 600 ° C., and 1000 ° C. The heat treatment atmosphere at 400 ° C. and 600 ° C. used O _{2 in} addition to Ar. All heat treatments were performed for 16 hours in an annular electric furnace (Isuzu Seisakusho, AT-E58).

Example 1 -1]
A negative electrode active material A31 of the present invention was prepared in the same manner as in Comparative Example 1-1 except that the active material A11 of Comparative Example 1-1 was further heat treated for 16 hours while flowing Ar at 350 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[Example 1-2 ]
A negative electrode active material A32 of the present invention was prepared in the same manner as Comparative Example 1-2 except that the active material A12 of Comparative Example 1-2 was further heat-treated for 16 hours while flowing Ar at 350 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[Example 1-3 ]
A negative electrode active material A33 of the present invention was prepared in the same manner as in Comparative Example 1-3, except that the active material A13 of Comparative Example 1-3 was further heat treated for 16 hours while flowing Ar at 350 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[Example 2 ]
The active material obtained in Comparative Example 1 was further heat-treated at a temperature of 400 ° C. in an Ar atmosphere.

Example 2 -1]
A negative electrode active material A41 of the present invention was produced in the same manner as Comparative Example 1-1 except that the active material A11 of Comparative Example 1-1 was further heat treated for 16 hours while flowing Ar at 400 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

Example 2-2]
A negative electrode active material A42 of the present invention was prepared in the same manner as Comparative Example 1-1 except that the active material A12 of Comparative Example 1-2 was further heat treated for 16 hours while flowing Ar at 400 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[Example 2-3 ]
A negative electrode active material A43 of the present invention was produced in the same manner as in Comparative Example 1-1 except that the active material A13 of Comparative Example 1-3 was further heat treated for 16 hours while flowing Ar at 400 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[Example 3 ]
An example in which the heat treatment temperature is 600 ° C. is shown below.

EXAMPLE 3 -1]
A negative electrode active material A51 of the present invention was prepared in the same manner as Comparative Example 1-1 except that the active material A11 of Comparative Example 1-1 was further heat-treated for 16 hours while flowing Ar at 600 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[Example 3-2]
A negative electrode active material A52 of the present invention was prepared in the same manner as Comparative Example 1-1 except that the active material A12 of Comparative Example 1-2 was further heat-treated for 16 hours while flowing Ar at 600 ° C. Furthermore, an electrode was produced in the same manner as in Comparative Example 1-1, and electrochemical measurements were performed.

[Example 3-3]
A negative electrode active material A53 of the present invention was prepared in the same manner as Comparative Example 1-1 except that the active material A13 of Comparative Example 1-3 was further heat treated for 16 hours while flowing Ar at 600 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 3 ]
An example in which the heat treatment temperature is 1000 ° C. is shown below.

[ Comparative Example 3-1]
A negative electrode active material A61 of the present invention was prepared in the same manner as Comparative Example 1-1 except that the active material A11 of Comparative Example 1-1 was further heat-treated for 16 hours while flowing Ar at 1000 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 3-2]
A negative electrode active material A62 of the present invention was prepared in the same manner as Comparative Example 1-1 except that the active material A12 of Comparative Example 1-2 was further heat treated for 16 hours while flowing Ar at 1000 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 3-3]
A negative electrode active material A63 of the present invention was prepared in the same manner as Comparative Example 1-1 except that the active material A13 of Comparative Example 1-3 was further heat treated for 16 hours while flowing Ar at 1000 ° C. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the electrochemical measurement was performed.

[ Comparative Example 4 ]
In the first step, to prepare a 3d transition metal oxyhydroxide containing no lithium was heat-treated in the second step. In the first step, Ni _a Co _b Mn _c (OH) _{2 in} which the molar ratio of Ni / Co / Mn is 1/1/1 , 2/1/1 , 3/1/1 is placed in _a 50 ° C. aqueous solution. While being dispersed, 1.2 equivalent of NaClO was added while stirring at a temperature of 50 ° C., and the mixture was stirred for 6 hours to be oxidized. Subsequently, the mixture was filtered with suction, washed with water, and further dried at 65 ° C. The thus obtained negative electrode active materials, 3d transition metal oxyhydroxides containing Ni, Co, and Mn, are respectively B11 ( Ni _1/3 Co _1/3 Mn _1/3 OOH), B12 ( Ni _{1 / 2 Co 1/4 Mn 1/4 O OH} ), it was _{B13 (Ni 3/5 Co 1/5 Mn 1/5} OOH).

With these negative active material 86 wt%, acetylene black 5 wt% as a conductive material, polyvinylidene difluoride 9 wt% and a (n- methyl-2-pyrrolidone solution of polyvinylidene difluoride) in a dry room as a binder After mixing and forming a paste, it was applied to the foamed nickel of the current collector, then vacuum-dried at 70 ° C., and pressed to produce a negative electrode plate having a thickness of 260 μm and a size of 10 mm × 20 mm.

Two lithium metal plates having the same size as the counter electrode were used for one negative electrode plate. Similarly, metallic lithium was used as a reference electrode. The negative electrode active material electrode according to the present invention was evaluated using 50 ml of a mixed solvent of ethylene carbonate and diethyl carbonate containing 1 M lithium perchlorate as the electrolytic solution. The charging / discharging conditions were charged at a constant current of 0.25 mA / cm ² up to 0.02 V on a lithium basis, and discharging was performed up to 3.0 V at a similar current density. The charge / discharge electricity amount and the capacity retention ratio after 20 cycles are shown in Table 1.

[ Comparative Example 5 ]
The negative electrode active materials B11, B12, and B13 obtained in Comparative Example 4 were subjected to vacuum heat treatment at 150 ° C. for 5 hours as B21, B22, and B23, respectively, and electrodes were prepared and charged / discharged in the same manner as in Comparative Example 4 . The charge / discharge results are also shown in Table 2.

[Example 4 ]
The negative electrode active materials B11, B12, and B13 obtained in Comparative Example 4 were heat-treated in an Ar atmosphere at 350 ° C. for 16 hours as B31, B32, and B33, respectively, and electrodes were produced in the same manner as in Comparative Example 4, and charge and discharge were performed. It was. The charge / discharge results are also shown in Table 2.

[Example 5 ]
The negative electrode active materials B11, B12, and B13 obtained in Comparative Example 4 were heat-treated in an Ar atmosphere at 400 ° C. for 16 hours as B41, B42, and B43, respectively, and electrodes were produced in the same manner as in Comparative Example 4, and charge and discharge were performed. It was. The charge / discharge results are also shown in Table 2.

[Example 6 ]
The negative electrode active materials B11, B12, and B13 obtained in Comparative Example 4 were heat-treated in an Ar atmosphere at 600 ° C. for 16 hours as B51, B52, and B53, respectively, and electrodes were produced in the same manner as in Comparative Example 4, and charge and discharge were performed. It was. The charge / discharge results are also shown in Table 2.

[ Comparative Example 6 ]
The negative electrode active materials B11, B12, and B13 obtained in Comparative Example 4 were heat-treated in an Ar atmosphere at 1000 ° C. for 16 hours as B61, B62, and B63, respectively, and electrodes were prepared and charged / discharged in the same manner as in Comparative Example 4. It was. The charge / discharge results are also shown in Table 2.

[Comparative Example 7 ]
Instead of the active material A11 of Comparative Example 1-1 was a Ni oxide NiO and Comparative Reikatsu material X1, were produced in the same manner as in the electrode in Comparative Example 1-1, Table 2 shows the charge and discharge results.

[Comparative Example 8 ]
Instead of the active material A11 of Comparative Example 1-1 was a Co oxide _Co 3 _{O 4} and Comparative Reikatsu material X2, to produce an electrode in the same manner as in Comparative Example 1-1, Table 2 shows the charge and discharge results .

[Comparative Example 9 ]
Instead of the active material A11 of Comparative Example 1-1 was the Mn oxide _Mn 2 _{O 3} and Comparative Reikatsu material X3, to prepare an electrode in the same manner as in Comparative Example 1-1, Table 2 shows the charge and discharge results .

From the above results, with or without lithium, Ni, Co, Mn solid solution oxyhydroxide oxide, the discharge capacity of the oxide Cal I is greater than the oxide thereof alone. In particular, it can be seen that the solid solution heat-treated in the temperature range of 350 ° C. to 600 ° C. has both a high discharge capacity and excellent cycle performance.

FIG. 2 shows a discharge curve of Li _x Ni _1/3 Co _1/3 Mn _1/3 O ₂ . As can be seen from FIG. 2, 0 to 2.2 V Vs. It can be seen that a continuous potential change is shown in the potential range of Li / Li ⁺ .

[Example 7 ]
In order to investigate the influence of the atmosphere of the heat treatment, the treatment temperature was fixed at 400 ° C., and O ₂ was used instead of Ar. Each of the active materials A11, A12, and A13 was heat-treated for 16 hours. The obtained active materials were designated as C11, C12, and C13. Furthermore, the electrode was produced similarly to the comparative example 1-1, and the charging / discharging result is shown in Table 3.

Comparing the discharge capacities of C11, C12, and C13 with those of A41, A42, and A43, respectively, all the active materials heat-treated in the O ₂ atmosphere did not change much in the cycle performance, but the discharge capacity increased significantly. was that behind that.

<Electrochemical reduction treatment>
When the above oxide is subjected to electrochemical reduction treatment in an organic electrolyte containing lithium ions, lithium can be introduced into the negative electrode, and a cell combined with a compound such as MnO ₂ or V ₂ O ₅ without a lithium source. Can be realized. When the reduced compound is oxidized again, an amorphous compound having a small initial irreversible capacity is obtained. In addition, the method for producing an amorphized or nanosized transition metal oxide exemplified here is an electrochemical method, but it can also be reduced by an organic complex of Li, and a chemical method for extracting lithium with an organic solvent. good.

[Example 8 ]
The 3d transition metal oxyhydroxides A11, A12, and A13 obtained in the first step of Comparative Example 1 were heat-treated in a 400 ° C. oxygen atmosphere, and the 3d transition metal oxide C 11 (Ni _1/3 Co _{1 / 3 Mn 1/3 O 2), C12} (Ni 1/2 Co 1/4 Mn 1/4 O 2), to give the _{C13 (Ni 3/5 Co 1/5} Mn 1/5 O 2). Furthermore, reduction treatment was performed electrochemically. The reduction is performed at a constant current of 0.25 mA / cm ² and 0.2 Vvs. It carried out to Li / Li ⁺ . The active materials subjected to the reduction treatment in this way are designated as D41, D42, and D43.

These compounds contain lithium and become a negative electrode active material in a charged state. The XRD results are shown in FIG. Using these 3d transition metal oxides D41, D42, and D43 , electrodes were produced in the same manner as in Example 1-1, and electrochemical measurements were performed . Table 4 shows the results of electrochemical measurement and the results of XRD analysis. Obviously, the oxide of the 3d transition metals D41, D42, D43 is amorphized, 5 ° in X-ray diffraction using CuKα ray <2θ <25 ° and 40 ° <2θ <FWHM of the diffraction peak appearing at 50 ° Is 5 ° (2θ) or more. The discharge capacities were the same as A41, A42, and A43, respectively.

[Example 9 ]
Comparative Example 4 of 3d transition metals obtained in oxyhydroxide _B11 a _{(Ni 1/3 Co 1/3 Mn 1/3 OOH} ), oxides of 3d transition metals obtained by heat treatment at 400 ° C. B41 (Ni _1/3 Co _1/3 Mn _1/3 O ₂ ) was electrochemically reduced. 0.2 Vvs. At a constant current of 0.25 mA / cm ² . E41 was reduced to Li / Li ^+, and F41 was further oxidized. The XRD patterns of these compounds are shown in FIG. Table 4 shows the results of electrochemical measurement and the results of XRD analysis.

Obviously, the active materials E41 and F41 become amorphous, and the half-value width of the diffraction peak appearing at 5 ° <2θ <25 ° and 40 ° <2θ <50 ° by the X-ray diffraction method using CuKα rays is excluded from the polypropylene peak. For example, it is 5 ° (2θ) or more. Then, a diffraction peak corresponding to Li ₂ O was observed in the vicinity of 33 ° (2θ) from the XRD pattern of E41 in the reduced state, and the peak was not observed from the XRD pattern of F41 in the oxidized state. It was confirmed that the formation of particles and the substitution redox reaction between Li and Li ₂ O (Formula 1) occurred.

[Example 10 ]
The active materials D41, D42 and D43 obtained in Example 9 were electrochemically treated at 3 Vvs. At 0.25 mA / cm ² . The battery was discharged to Li / Li ⁺ and electrochemically charged and discharged. The results are shown in Table 4.

Clearly, electrochemical reduction, active material F41 produced through the oxidation process, G41, G42, G43 initial irreversible capacity is little, it can be seen that a negative electrode active material of an ideal discharge state.

TG-DTA curve of the active material obtained in Comparative Example 1, temperature rising rate 5 ° C./min. The first cycle charge / discharge curve of Li _x Ni _1/3 Co _1/3 Mn _1/3 O ₂ . Charge / discharge current density: 0.2 mA / cm ² . XRD measurement results of samples (D41, D42, D43) after electrochemical reduction of oxides (C11, C12, C13) of 3d transition metals . Use Cukα radiation. XRD measurement results of E41 obtained by electrochemically reducing 3d transition metal oxide B41 and further oxidized F41 .

Claims (3)

A first step of oxidizing at least one metal hydroxide in an aqueous solution selected from 3d transition metals, the oxyhydroxide obtained in the first step 350 ° C. or higher, 600 ° C. at a temperature A method for producing a 3d transition metal oxide for a negative electrode active material of a non-aqueous electrolyte electrochemical cell , wherein the second step of heat treatment is performed. A third method in which the oxide of the 3d transition metal obtained in the second step is electrochemically reduced in an organic electrolyte. The negative electrode active material 3 for a non-aqueous electrolyte electrochemical cell according to claim 1, wherein Method for producing oxide of d transition metal. Formula _{Li x Ni a Co b Mn 1} -a-b O 2 ( However, a: b: c = 1 : 1: 1~3: 1: 1 ( molar ratio)) is represented by, using a CuKα ray 5 ° in X-ray diffractometry <2θ <25 ° and 40 ° <2θ <50 half width 5 ° of the diffraction peaks appearing in ° (2 [Theta]) or the negative electrode for non-aqueous electrolyte electrochemical cell characterized in that Active material .