JP2005135861A - Nonaqueous electrolyte electrochemical cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode activator made of transition metal oxide excellent in discharging capacity, charging and discharging potential, and cycle performance, since cobalt oxide is not always an ideal candidate of a cheap negative electrode activator having high energy density because of high discharge potential and a resource problem in spite of its excellent cycle performance. <P>SOLUTION: On the manufacturing process of the negative electrode activator for the nonaqueous electrolyte electrochemical cell, an oxide of 3d transition metal is manufactured by applying a heat treatment of not lower than 350°C and not higher than 600°C to a kind of oxyhydroxide of the metal chosen from 3d transition metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a negative electrode active material for a 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. Patent Document 1 discloses a technique using iron oxide, FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , cobalt oxide, CoO, Co ₂ O _3, and Co ₃ O ₄ as a negative electrode active material. Patent Document 2 discloses a technique using various lithium-containing or non-lithium-containing transition metal oxides as a negative electrode active material, for example, Li _x M _q V _1-q O _j (where M is a transition metal). And 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). Disclosed are metal oxides and techniques for their production. Further, Patent Document 3 discloses a technology for inserting lithium ions electrochemically, with the particle size of the transition metal oxide negative electrode active material, the firing conditions, and electrochemically.

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 showed a discharge capacity of 700 mAh / g or more, and generation of Li ₂ O and nano-sized transition metals were confirmed with charging. Further, the cycle performance of the cobalt oxide was good.

further,
“Electrochemical and Solid-state Letters”, Vol. 5, pages A70-A73, describes a technique for producing lithium-containing transition metal oxides and sulfides by mechanical milling. The maximum initial discharge capacity of the obtained mixture was 600 mAhg-1 or more, but the 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, Vol. 5, PA70-A73 (2002)

  Although cobalt oxide showed excellent cycle performance, the discharge potential is high and the resource problem of cobalt exists, so it is not an ideal candidate as a high energy density, 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, an object of the present invention is to provide a transition metal oxide negative electrode active material excellent in discharge capacity, charge / discharge potential, and cycle performance.

  As a result of our extensive research, it was found that oxides in which various transition metals are dissolved have excellent discharge potential, cycle performance and discharge capacity.

  According to a first aspect of the present invention, in the method for producing a negative electrode active material for a non-aqueous electrolyte electrochemical cell, an oxyhydroxide of at least one metal selected from 3d transition metals is heat-treated at a temperature of 350 ° C. or higher and 600 ° C. or lower. Thus, an oxide of the 3d transition metal is produced.

  According to a second aspect of the present invention, in the method for producing a negative electrode active material for a non-aqueous electrolyte electrochemical cell, the oxide of the 3d transition metal is an oxide in which three elements of nickel, cobalt, and manganese are dissolved. Features.

  The invention of claim 3 is characterized in that, in the above method for producing a negative electrode active material for a non-aqueous electrolyte electrochemical cell, the oxide of the 3d transition metal contains lithium.

  According to a fourth aspect of the present invention, in the method for producing a negative electrode active material for a nonaqueous electrolyte electrochemical cell according to the third aspect, in an organic electrolyte, the potential range based on lithium is electrochemically reduced to 0 to 0.3 V. The half-width of the diffraction peak produced through the process and appearing at 5 ° <2θ <25 ° and 40 ° <2θ <50 ° by the X-ray diffraction method using CuKα rays is 5 ° (2θ) or more. And

  According to the invention of claim 1, a 3d transition metal oxide having a high atomic oxygen content and a low hydrogen content in a compound is obtained. Since the discharge capacity of the 3d transition metal oxide is proportional to the active oxygen content as shown in Equation 1, the discharge capacity of the 3d transition metal oxide prepared from oxyhydroxide is high. . 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 oxide in which the three elements of nickel, cobalt, and manganese are solid-solved can be produced, and a negative electrode active material having a continuous discharge potential and a low average potential can be obtained.

  According to the invention of claim 3, since a lithium source is present, it can be used in combination with a positive electrode not containing lithium.

  According to the invention of claim 4, the lithium-containing transition metal oxide obtained by electrochemical reduction becomes amorphous, and such a composite oxide is expected to improve the cycle performance.

  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 produced by the production method of the present invention as the negative electrode active material, a nonaqueous electrolyte electrochemical cell having a high discharge capacity and excellent cycle performance and discharge potential can be obtained.

  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 paid attention to transition metal oxides, and as a result of earnest research on combinations and ratios of various elements and synthesis conditions, at least 350 ° C. or more of oxyhydroxides of at least one metal selected from 3d transition metals. The 3d transition metal oxide manufactured by heat treatment at a temperature of 600 ° C. or less 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. I found out.

  Here, “3d transition metal” refers to Ni, Co, Mn, Fe, V, Zn, and Cu. As the metal in the 3d transition metal oxide, only one kind of 3d transition metal such as Ni, Co, Mn, Fe, V, Zn, Cu may be selected. For example, Ni, Co, Mn, etc. Multiple types may be selected.

  Further, these transition metal oxides may further contain Li. Preferably, a composite oxide prepared by producing an oxyhydroxide containing Ni, Co, and Mn at a temperature of 350 ° C. or higher and 600 ° C. or lower exhibits the performance improvement effect of the active material more remarkably.

  The 3d transition metal oxyhydroxide as a starting material of the present invention preferably starts from the hydroxide having an average oxidation number of the 3d transition metal of less than 3, and the average oxidation number of the transition metal is 3 or more. If the present invention is applied to the case where it is oxidized, the effect of the invention can be further extracted.

  A coprecipitation method is preferable for dissolving the 3d transition metal of the oxide at an atomic level. 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, when a 3d transition metal hydroxide compound is dispersed in an LiOH aqueous solution and oxidized with an oxidizing agent at a temperature of 80 ° C., a partially lithium ion-exchanged oxyhydroxide is obtained. When Mn and Fe are contained, 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 oxide is limited to the equilibrium constant of the ion exchange reaction, but more lithium ions such as Li / Me (Me is at least one transition metal)> 0. No lithium-containing transition metal oxide containing 86 has been 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 obtained oxyhydroxide 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, 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.

Materials used in the present invention include those produced from the above transition metal oxyhydroxides, such as CoO, Co ₃ O ₄ , Co ₂ O ₃ , CoOOH, NiO, NiOOH, TiO ₂ , TiO, TiS ₂ , _{V 2 O 3, V 2 O} 4, V 2 O 5, CrO 3, Cr 2 O 3, MnO, MnO 2, Mn 2 O 3, Mn 3 O 4, MnOOH, FeO, Fe 2 O 3, Fe 3 O ₄ , FeOOH, FePO ₄ , CuO, Cu ₂ O, ZnO, MoS ₂ , MoO _{3 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.

Furthermore, as a method of introducing lithium into the transition metal oxide, there is a method of short-circuiting an electrode containing a transition metal oxide and a metal lithium electrode in an electrolytic solution. Further, when an electrode including a 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 prepared and the electrode is brought into contact with an organic electrolyte, a battery is obtained. A 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. Furthermore, a lithium-containing transition metal oxide can be produced by using the metal oxide as an electrode and electrochemically reducing the potential range based on lithium to 0 to 0.3 V in an organic electrolyte.

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

[Example 1]
[Example 1-1]
Ni _1/3 Co _1/3 Mn _1/3 (OH) ₂ having a Ni / Co / Mn molar ratio of 1/1/1 was dispersed in a 4M LiOH aqueous solution, and 1.2 equivalents at a temperature of 80 ° C. 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 obtained final product was used as the positive electrode active material A11, 5% by weight of acetylene black as a conductive material, and n-methyl-2-pyrrolidone solution of polyvinylidene difluoride as a binder (9% by weight as a solid content of polyvinylidene difluoride). ) In a dry room to form a paste, and then applied to the nickel foam foam of the current collector, then vacuum dried at 70 ° C. and pressed to have a thickness of 260 μm and a size of 10 mm × 20 mm. A negative electrode plate was produced.

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.

[Example 1-2]
A negative electrode active material A12 of the present invention was produced in the same manner as in Example 1-1 except that the Ni / Co / Mn molar ratio was 2/1/1 Me (OH) ₂ . Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 1-3]
A negative electrode active material A13 of the present invention was produced in the same manner as Example 1-1 except for Me (OH) ₂ having a Ni / Co / Mn molar ratio of 3/1/1. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 2]
The active material obtained in Example 1 was further subjected to heat treatment at 150 ° C.

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

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

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

[Example 3]
TG-DTA measurement was performed on the active material obtained in 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 3-1]
A negative electrode active material A31 of the present invention was produced in the same manner as in Example 1-1, except that the active material A11 of Example 1-1 was further heat-treated for 16 hours while flowing Ar at 350 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 3-2]
A negative electrode active material A32 of the present invention was produced in the same manner as in Example 1-2, except that the active material A12 of Example 1-2 was further heat-treated for 16 hours while flowing Ar at 350 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

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

[Example 4]
The active material obtained in Example 1 was further heat-treated at a temperature of 400 ° C. in an Ar atmosphere.

[Example 4-1]
A negative electrode active material A41 of the present invention was produced in the same manner as in Example 1-1 except that the active material A11 of Example 1-1 was further heat-treated for 16 hours while flowing Ar at 400 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 4-2]
A negative electrode active material A42 of the present invention was produced in the same manner as in Example 1-1, except that the active material A12 of Example 1-2 was further heat treated for 16 hours while flowing Ar at 400 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 4-3]
A negative electrode active material A43 of the present invention was produced in the same manner as in Example 1-1, except that the active material A13 of Example 1-3 was further heat-treated for 16 hours while flowing Ar at 400 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 5]
An example in which the heat treatment temperature is 600 ° C. is shown below.

[Example 5-1]
A negative electrode active material A51 of the present invention was produced in the same manner as in Example 1-1, except that the active material A11 of Example 1-1 was further heat-treated for 16 hours while flowing Ar at 600 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 5-2]
A negative electrode active material A52 of the present invention was produced in the same manner as in Example 1-1 except that the active material A12 of Example 1-2 was further heat-treated for 16 hours while flowing Ar at 600 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 5-3]
A negative electrode active material A53 of the present invention was produced in the same manner as in Example 1-1, except that the active material A13 of Example 1-3 was further heat-treated for 16 hours while flowing Ar at 600 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 6]
An example in which the heat treatment temperature is 1000 ° C. is shown below.

[Example 6-1]
A negative electrode active material A61 of the present invention was produced in the same manner as in Example 1-1, except that the active material A11 of Example 1-1 was further heat-treated for 16 hours while flowing Ar at 1000 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 6-2]
A negative electrode active material A62 of the present invention was produced in the same manner as in Example 1-1, except that the active material A12 of Example 1-2 was further heat-treated for 16 hours while flowing Ar at 1000 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 6-3]
A negative electrode active material A63 of the present invention was produced in the same manner as in Example 1-1, except that the active material A13 of Example 1-3 was further heat-treated for 16 hours while flowing Ar at 1000 ° C. Furthermore, an electrode was prepared in the same manner as in Example 1-1, and electrochemical measurements were performed.

[Example 7]
A transition metal oxyhydroxide containing no lithium was prepared and heat-treated. Ni / Co / Mn molar ratio of 1/1/1/1 / 1,3 / 1/1 of the _{Ni a Co b Mn c (OH} ) 2 was dispersed in 50 ° C. aqueous solution, stirred at a temperature of 50 ° C. While adding 1.2 equivalents of NaClO, the mixture was stirred for 6 hours to oxidize. Subsequently, the mixture was filtered with suction, washed with water, and further dried at 65 ° C. The final products thus obtained were designated as positive electrode active materials B11, B12, and B13, respectively.

  Dry room containing 86 wt% of these active materials, 5 wt% of acetylene black as a conductive material, and n-methyl-2-pyrrolidone solution of polyvinylidene difluoride (9 wt% as solid content of polyvinylidene difluoride) as a binder After mixing in a paste and applying to the foamed nickel of the current collector, vacuum drying at 70 ° C. and pressing to produce each negative electrode plate with a thickness of 260 μm and a size of 10 mm × 20 mm did.

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.

[Example 8]
The negative electrode active materials B11, B12, and B13 obtained in Example 7 were respectively B21, B22, and B23 under vacuum heat treatment at 150 ° C. for 5 h, and electrodes were prepared and charged / discharged in the same manner as in Example 7. The charge / discharge results are also shown in Table 2.

[Example 9]
The negative electrode active materials B11, B12, and B13 obtained in Example 7 were heat-treated at 350 ° C. in an Ar atmosphere for 16 hours as B31, B32, and B33, respectively, and electrodes were produced in the same manner as in Example 7, and charge and discharge were performed. It was. The charge / discharge results are also shown in Table 2.

[Example 10]
The negative electrode active materials B11, B12, and B13 obtained in Example 7 were heat-treated at 400 ° C. in an Ar atmosphere for 16 hours as B41, B42, and B43, respectively, and electrodes were prepared and charged / discharged in the same manner as in Example 7. It was. The charge / discharge results are also shown in Table 2.

[Example 11]
The negative electrode active materials B11, B12, and B13 obtained in Example 7 were heat-treated at 600 ° C. in an Ar atmosphere for 16 hours as B51, B52, and B53, respectively, and electrodes were produced in the same manner as in Example 7 to charge and discharge. It was. The charge / discharge results are also shown in Table 2.

[Example 12]
The negative electrode active materials B11, B12, and B13 obtained in Example 7 were heat treated in an Ar atmosphere at 1000 ° C. for 16 hours, and B61, B62, and B63 were respectively prepared as in Example 7, and charged and discharged. It was. The charge / discharge results are also shown in Table 2.

[Comparative Example 1]
An electrode was prepared in the same manner as in Example 1-1 using Ni oxide NiO as the comparative active material X1 instead of the active material A11 of Example 1-1, and the charge / discharge results are shown in Table 2.

[Comparative Example 2]
An electrode was prepared in the same manner as in Example 1-1 using Co oxide Co ₃ O ₄ as the comparative active material X2 instead of the active material A11 of Example 1-1, and the charge / discharge results are shown in Table 2. .

[Comparative Example 3]
In place of the active material A11 of Example 1-1, an electrode was prepared in the same manner as in Example 1-1 using Mn oxide Mn ₂ O ₃ as a comparative example active material X3, and the charge / discharge results are shown in Table 2. .

  As can be seen from the above results, it can be seen that the discharge capacities of Ni, Co, Mn solid solution oxyoxides and oxides are larger than those single oxides regardless of the presence or absence of lithium. 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 13]
In order to investigate the influence of the heat treatment atmosphere, 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 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. I understand 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 14]
The lithium-containing nickel oxyhydroxides C11, C12, and C13 heat-treated in an oxygen atmosphere at 400 ° C. were further electrochemically reduced. 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. These compounds were produced on electrodes in the same manner as in Example 1-1. Table 4 shows the results of electrochemical measurement and the results of XRD analysis. Clearly, the active materials D41, D42 and D43 are made 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 5 ° (2θ ) That's it. The discharge capacities were the same as A41, A42, and A43, respectively.

[Example 15]
The nickel oxyhydroxide B41 heat-treated at 400 ° C. 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 pattern of these compounds is 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 16]
The active materials D41, D42 and D43 obtained in Example 15 were electrochemically applied 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.

  Obviously, the active materials F41, G41, G42, and G43 produced through electrochemical reduction and oxidation processes have almost no initial irreversible capacity, and are negative electrode active materials in an ideal discharge state.

TG-DTA curve, heating 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: 0.25 mA / cm. Lithium-containing _{Li x Ni a Co b Mn 1} -a-b O 2 electrochemically reduced after sample XRD measurements at 400 ° C.. Use Cukα radiation. 400 _Ni 1/3 was heat-treated at ° C. _Co 1/3 _Mn 1/3 discharge around the XRD measurement results of OOH.

Claims (4)

Non-aqueous electrolyte electrochemistry characterized in that an oxyhydroxide of at least one metal selected from 3d transition metals is heat-treated at a temperature of 350 ° C. or higher and 600 ° C. or lower to produce the 3d transition metal oxide. A method for producing a negative electrode active material for a cell. The method for producing a negative electrode active material for a non-aqueous electrolyte electrochemical cell according to claim 1, wherein the 3d transition metal oxide is an oxide in which three elements of nickel, cobalt, and manganese are dissolved. The method for producing a negative electrode active material for a non-aqueous electrochemical cell according to claim 1 or 2, wherein the oxide of the 3d transition metal contains lithium. In an organic electrolyte, it is produced through a process of electrochemical reduction to a lithium-based potential range of 0 to 0.3 V, and 5 ° <2θ <25 ° and 40 ° by X-ray diffraction using CuKα rays. 4. The method for producing a negative electrode active material for a non-aqueous electrolyte electrochemical cell according to claim 3, wherein the half width of the diffraction peak appearing at <2θ <50 ° is 5 ° (2θ) or more.

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