JP4851699B2 - Anode active material for non-aqueous electrolyte electrochemical cell and non-aqueous electrolyte electrochemical cell using the same - Google Patents

Description

  The present invention relates to a negative electrode active material for a non-aqueous electrolyte electrochemical cell and a non-aqueous electrolyte electrochemical cell using the same.

  In recent years, with the development of portable electronic devices such as mobile phones and video cameras, development of high-performance batteries is desired. Among the various types of batteries, non-aqueous electrolyte secondary batteries such as lithium ion batteries with high operating voltage and high energy density using lithium transition metal composite oxide for the positive electrode and graphite or amorphous carbon for the negative electrode are used. Widely used.

  In addition, research has been conducted on the use of metallic lithium or lithium alloys having a theoretical capacity larger than that of carbon materials as a negative electrode active material for nonaqueous electrolyte secondary batteries. However, since metal dendrites and lithium alloys generate dendrites as they are charged and discharged, they have many problems in terms of charge / discharge cycle life and safety. Electrolyte secondary batteries have not yet been commercialized.

On the other hand, transition metal oxides have been conventionally used as positive electrode active materials for non-aqueous electrolyte secondary batteries, but recently, it has been reported that they can also be used as negative electrode active materials. For example, Patent Document 1 discloses a technique using iron oxide such as FeO, Fe ₂ O ₃ , and Fe ₃ O ₄ and cobalt oxide such as CoO, Co ₂ O ₃ , and Co ₃ O ₄ as a negative electrode active material. ing. Further, Patent Document 2 discloses various transition metal oxides containing lithium or not containing lithium, such as Li _x M _q V _{1 -q} O _j (non lithium electrolyte secondary battery). M is a transition metal, and a technique using a lithium-containing transition metal oxide represented by 0.17 ≦ x ≦ 11.25, 0 ≦ q ≦ 0.7, 1.3 ≦ j ≦ 4.1) is disclosed. Has been. Furthermore, Patent Document 3 discloses a technique for inserting lithium ions electrochemically when the transition metal oxide is used as the negative electrode active material of the nonaqueous electrolyte secondary battery. .

Non-Patent Document 1 discloses characteristics and reaction mechanisms of transition metal oxides such as CoO, Co ₃ O ₄ , NiO, FeO, and Cu ₂ O as a negative electrode active material of a non-aqueous electrolyte secondary battery. ing. These oxides showed a discharge capacity of 700 mAh / g or more, and it was confirmed that Li ₂ O and nano-sized transition metals were generated with charging. Among these transition metal oxides, cobalt oxide is reported to have good charge / discharge cycle performance.

Non-Patent Document 2 discloses a technique for producing lithium-containing transition metal oxides and sulfides by a mechanical milling method, and the maximum initial discharge capacity of the obtained mixture is 600 mAh / g or more. Inferior performance has been reported. Non-Patent Document 3 reports lithium-containing nickel, cobalt, and manganese ternary transition metal oxides as negative electrode active materials for nonaqueous electrolyte secondary batteries, and these transition metal oxides have a discharge of about 700 mAh / g. Indicates capacity. Non-Patent Document 4 reports a Ni _0.75 Mn _0.25 O _1.36 rock salt-based oxide negative electrode active material fired at 600 ° C., indicating that this oxide exhibits a discharge capacity of about 700 mAh / g. It has been reported.

Japanese Patent Laid-Open No. 03-291862 Japanese Patent No. 3242751 JP-A-7-14581 P. Poizot, S.M. Larneie, S .; Grugeon and J.M. M.M. Tarascon Nature, 407, P496-499 Electrochemical and Solid-state Letters, 5, PA70-A73 Liu, Yasuda, Yamachi 44th Battery Conference Proceedings, 3A18 (2000) X. Liu, H .; Yasuda and M.M. Yamachi 12th International Meeting on Lithium Batteries, Abs. No. 280

According to the above prior art and reports, cobalt oxide (CoO) exhibits excellent charge / discharge cycle performance as a negative electrode active material of a non-aqueous electrolyte secondary battery, but discharge potential (vs. Li ^/ Li ⁺ ). Therefore, it is difficult to obtain a high energy density battery, and since there is a problem of cobalt resources, it cannot be an ideal candidate for an inexpensive negative electrode active material.

  On the other hand, the charge / discharge behavior of nickel oxide (NiO) is similar to that of CoO and is cheaper than cobalt, but there is a problem that the charge / discharge cycle performance is inferior. In addition, the report which uses a manganese oxide for the negative electrode active material of a nonaqueous electrolyte secondary battery is not disclosed.

Therefore, the present invention provides a negative electrode active material for a non-aqueous electrolyte electrochemical cell having a low discharge potential (vs. Li ^/ Li ⁺ ), excellent cost and charge / discharge cycle performance, and non-aqueous electrolyte electrochemical using the same. The purpose is to provide a cell.

The invention according to claim 1 is a general formula Ni _x Mn _y O _z (where 0.45 ≦ x ≦ 0.55, 0.9 ≦ x + y ≦ 1.1, An oxide containing nickel and manganese represented by 1.0 ≦ z ≦ 2.0) is used. (However, the case where x / (x + y) = 0.5 is excluded.)

  According to a second aspect of the present invention, in the negative electrode active material for a non-aqueous electrolyte electrochemical cell, a diffraction peak appearing at 15 ° <2θ <20 ° and 30 ° <2θ <45 ° by X-ray diffraction using CuKα rays. -The half width of the square is 5 ° (2θ) or more.

The invention of claim 4 is characterized in that the negative electrode active material according to any one of claims 1 to 3 is used in a non-aqueous electrolyte electrochemical cell.

The negative electrode active material for a non-aqueous electrolyte electrochemical cell of the present invention is inexpensive and has a low discharge potential (vs. Li ^/ Li ⁺ ) by using a resource-rich and low-toxic oxide containing nickel and manganese. An oxide in which nickel and manganese are mixed at the atomic level can be obtained.

  In addition, by using the oxide containing nickel and manganese of the present invention as the negative electrode active material of a non-aqueous electrolyte electrochemical cell, it is possible to obtain a non-aqueous electrolyte electrochemical cell with high energy density and excellent charge / discharge cycle performance. it can.

  The present invention relates to a negative electrode active material for a non-aqueous electrolyte electrochemical cell and a non-aqueous electrolyte electrochemical cell using the negative electrode active material. In the present invention, the “nonaqueous electrolyte electrochemical cell” means a nonaqueous electrolyte secondary battery, an electrochemical capacitor, or the like.

  The present inventors focused on transition metal oxides as negative electrode active materials for non-aqueous electrolyte electrochemical cells, in which an oxide containing nickel and manganese has a low discharge potential and a continuous discharge potential, It has been found that it has excellent charge / discharge cycle performance.

That is, the negative electrode active material for a non-aqueous electrolyte electrochemical cell of the present invention has a general formula Ni _x Mn _y O _z (where 0.45 ≦ x ≦ 0.55, 0.9 ≦ x + y ≦ 1.1, 1. 0 ≦ z ≦ 2.0), which is an oxide containing nickel and manganese.

  When the value of x is smaller than 0.45, the manganese content increases and the charge / discharge cycle characteristics become inferior. When the value of x is larger than 0.55, the nickel content increases. Thus, the discharge potential becomes noble, and when used in a battery, the discharge voltage becomes low, a high energy density battery cannot be obtained, and the cost increases.

  The value of (x + y) is usually a value close to 1.0, but the characteristics obtained are the same even when the value deviates from 1.0 and becomes a value between 0.9 and 1.1. However, if the value of x + y is out of this range, the crystal structure changes and the desired characteristics cannot be obtained.

  The value of z usually takes a value close to 1.5. However, even if the oxygen content is slightly less than this or slightly more than this, if the range of 1.0 ≦ z ≦ 2.0 is obtained. The properties obtained are the same. When the value of z is out of this range, the crystal structure changes and the charge / discharge cycle characteristics become inferior. The value of z is determined by the heat treatment conditions, but it is difficult to strictly control.

When producing the negative electrode active material for a non-aqueous electrolyte electrochemical cell of the present invention, the nickel source is a compound such as NiO, Ni (OH) ₂ , NiOOH, the manganese source is Mn (OH) ₂ , MnO, MnO ₂ , A compound such as Mn ₂ O ₃ , Mn ₃ O ₄ , or MnOOH can be used.

  In addition to the Ni and Mn, the negative electrode active material for the non-aqueous electrolyte electrochemical cell of the present invention includes 3d transition metals such as Co, Ti, Fe, Zn, V, and Cu, and elements such as Al, Na, and Mg. May be included. Furthermore, typical non-metallic elements such as N, P, F, Cl, Br, I, and S may be included in the above substance. Further, these transition metal oxides may further contain Li.

  As the crystal structure of the negative electrode active material of the present invention, those having a cubic spinel structure to amorphous can be used, but amorphous is preferable for high rate discharge. The negative electrode active material of the present invention having an amorphous crystal structure is a half of the diffraction peak appearing at 15 ° <2θ <20 ° and 30 ° <2θ <45 ° by X-ray diffraction using CuKα rays. The value width is 5 ° (2θ) or more.

  Moreover, as a shape of the negative electrode active material of this invention, the thing of all shapes, such as a powder, a film | membrane, a porous body, can be used.

  As a method for producing a negative electrode active material for a non-aqueous electrolyte electrochemical cell according to the present invention, a method in which a nickel source compound and a manganese source compound are mixed and baked can be adopted. However, nickel and manganese are fixed at an atomic level. The coprecipitation method is preferable for dissolving the solution.

  The manufacturing method by the coprecipitation method of the negative electrode active material of this invention passes through the following processes. First, a nickel compound (for example, nickel hydroxide) having an average oxidation number of less than 3 and a manganese compound (for example, manganese hydroxide) are dissolved and dispersed in an alkaline aqueous solution.

  Next, the aqueous solution is brought to a temperature slightly higher than room temperature (for example, 50 ° C.), oxidized with an oxidizing agent until the average oxidation number of nickel and manganese becomes 3 or more, and then the precipitate is filtered and dried. An oxyhydroxide containing manganese and manganese is obtained. In this case, in order to prevent manganese from being oxidized to tetravalent, it is desirable to oxidize while protecting with an inert gas such as nitrogen or argon gas. This avoids the formation of “inert carbonates”.

  The kind of oxidizing agent is not particularly limited. As the oxidizing agent, preferably, at least one selected from oxygen, ozone or peroxodisulfate, or hypochlorite, permanganate, dichromate, bromine, and chlorine can be used. In addition to the chemical oxidation method using an oxidizing agent, an electrochemical method may be used.

  Next, the negative electrode active material for a non-aqueous electrolyte electrochemical cell of the present invention can be obtained by heat-treating an oxyhydroxide containing nickel and manganese at a temperature of 600 ° C. or higher. Note that the optimum value of the heat treatment temperature is determined using the measurement result of TG-DTA. The lower limit of the heat treatment temperature, 600 ° C., is a temperature at which crystal water and structural water are removed. Further, when an inert gas such as nitrogen or argon is used as the atmosphere for the heat treatment, the same effect as that obtained when heat treatment is performed in air or oxygen can be expected.

  The oxyhydroxide containing nickel and manganese of the present invention can be used by forming a composite with a carbon material. A material obtained by coating the surface of an oxyhydroxide containing nickel and manganese with a carbon material, or a material obtained by mixing and granulating an oxyhydroxide containing nickel and manganese with a carbon material can be used. As a method of coating with a carbon material, benzene, toluene, xylene, methane, propane, butane, ethylene or acetylene is decomposed in the gas phase using a carbon source, and the surface of oxyhydroxide particles containing nickel and manganese is chemically treated. To be produced by a chemical vapor deposition CVD method, a method in which a thermoplastic resin such as pitch, tar, or furfuryl alcohol is mixed with an oxyhydroxide containing nickel and manganese, followed by firing, or a method using a mechanochemical reaction. Can do. Among these manufacturing methods, the CVD method is desirable.

Nickel represented by the general formula Ni _x Mn _y O _{z of the} present invention (where 0.45 ≦ x ≦ 0.55, 0.9 ≦ x + y ≦ 1.1, 1.0 ≦ z ≦ 2.0) The oxide containing manganese can be used as it is for the negative electrode active material of the nonaqueous electrolyte electrochemical cell. However, this oxide has a difference between the initial charge capacity and the subsequent discharge capacity, and this difference is referred to as an irreversible capacity (= initial charge capacity−discharge capacity). Here, the “irreversible capacity” is the capacity of lithium that is occluded in the oxide by charge and is not released in the next discharge.

  By associating lithium corresponding to this irreversible capacity into the negative electrode before assembling the battery, a non-aqueous electrolyte electrochemical cell having a large capacity can be obtained.

The methods include (1) a method of short-circuiting the negative electrode active material of the present invention and metallic lithium in an electrolyte solution, and (2) a negative electrode active material of the present invention, lithium alloy powder, lithium-containing transition metal nitride (for example, Li _2.5 Co _0.5 N powder) and a method for producing a lithium-containing transition metal oxide nanoparticle by causing a battery reaction by contacting an electrode with an organic electrolyte, and (3) a negative electrode active of the present invention A method in which a substance is brought into contact with an organic solution such as an organic complex of lithium, for example, butyl lithium, and (4) an electrode including the negative electrode active material of the present invention is prepared, and 0.5 V or less based on lithium in the organic electrolyte, There is a method of electrochemical reduction to a potential of 0 V or more.

  When the negative electrode active material for a non-aqueous electrolyte electrochemical cell of the present invention is used as an electrode, fine powders such as Cu, Ni, Ti, and Co can be used as a conductive material, but acetylene black, amorphous carbon, graphite powder, Carbon materials such as carbon nanotubes and carbon nanophones are more desirable. The mechanical milling method is desirable for mixing the conductive material and the negative electrode active material of the present invention well.

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

As the cathode material used in the nonaqueous electrolyte battery of the present _invention, LiCoO _2, LiNiO 2, composition formula such as LiMn ₂ O _{4 Li} x MO ₂ or _Li y _M 2 _{O 4} (provided that, M is a transition metal, 0 ≦ A composite oxide represented by x ≦ 1, 0 ≦ y ≦ 1), an oxide having a tunnel-like hole, a metal chalcogenide having a layered structure, or 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 lithium-containing nickel manganese 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 nonaqueous electrolyte used in the nonaqueous electrolyte battery of the present invention may be a nonaqueous electrolyte solution, a polymer electrolyte, a room temperature molten salt or ionic liquid, 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 for a nonaqueous electrolyte electrochemical cell of the present invention and a nonaqueous electrolyte secondary battery as an example of a nonaqueous electrolyte electrochemical cell using the negative electrode active material will be described in detail based on Examples. Explained. However, the present invention is not limited to the following examples.

[Examples 1 and 2 and Comparative Examples 1 and 2]
[Example 1]
A reaction vessel containing 50 ml of ion exchange water at 50 ° C. was prepared, nitrogen was bubbled through the ion exchange water to replace dissolved oxygen, and the reaction vessel was purged with nitrogen. Next, 5.0 g of nickel hydroxide (Ni (OH) ₂ ) and 4.8 g of manganese hydroxide (Mn (OH) ₂ ) are dissolved in this ion-exchanged water (a molar ratio of Ni and Mn is 1: 1). After dispersion, 1.2 equivalent of NaClO was added, and the mixture was stirred for 4 hours while maintaining 50 ° C. to cause an oxidation reaction. Subsequently, it is filtered by suction, washed three times with deoxygenated ion-exchanged water, and further dried at 60 ° C. for 12 hours, whereby an oxyhydroxide containing nickel and manganese (Ni _0.5 Mn _{0 .5} OOH). This oxyhydroxide was subjected to a heat treatment in air at 800 ° C. for 16 hours using a ring electric furnace (manufactured by Isuzu Seisakusho, AT-E58). An oxide containing manganese (Ni _0.5 Mn _0.5 O _1.43 ) was obtained. This is designated as negative electrode active material A1.

  90% by mass of the negative electrode active material A1, 7% by mass of acetylene black as a conductive material and 3% of polyvinylidene difluoride as a binder are mixed, and n-methyl-2-pyrrolidone is added to the inside of the dry room. The mixture is made into a paste and then applied to a foamed copper substrate which is a 350 μm-thick current collector, vacuum-dried at 70 ° C. for 5 hours, and roll-pressed to have a thickness of 330 μm and a size of 15 mm × A 15 mm negative electrode plate was produced.

[Example 2]
The same cyclic electricity as used in Example 1 was prepared by mixing 1.00 g of nickel powder having an average particle diameter of 10 μm and 0.94 g of manganese powder having an average particle diameter of 10 μm (a molar ratio of Ni and Mn of 1: 1) in a mortar. By performing a heat treatment in the air for 10 hours using a furnace, an oxide containing nickel and manganese (Ni _0.5 Mn _0.5 O _1.43) which is the negative electrode active material of Example 2 according to the present invention. ) This is designated as negative electrode active material A2. Using this negative electrode active material A2, a negative electrode plate was produced in the same manner as in Example 1.

[Comparative Example 1]
A negative electrode active material NiO of Comparative Example 1 is obtained by subjecting 1.00 g of nickel powder having an average particle diameter of 10 μm to heat treatment in air for 10 hours using the same annular electric furnace as used in Example 1. It was. This is designated as negative electrode active material B1. Using this negative electrode active material B1, a negative electrode plate was produced in the same manner as in Example 1.

[Comparative Example 2]
In ion-exchanged water, 7.5 g of nickel hydroxide (Ni (OH) ₂ ) and 2.4 g of manganese hydroxide (Mn (OH) ₂ ) (molar ratio of Ni and Mn 3: 1) were dissolved and dispersed. Except for this, the negative electrode active material Ni _0.75 Mn _0.25 O _1.36 of Comparative Example 2 was obtained in the same manner as Example 1. This is designated as a negative electrode active material B2. Using this negative electrode active material B2, a negative electrode plate was produced in the same manner as in Example 1.

  For one negative electrode plate obtained in Examples 1 and 2 and Comparative Examples 1 and 2, two 20 mm × 20 mm metal lithium plates were used as the counter electrode, and the same metal lithium plate as the counter electrode was used as the reference electrode. A test electrochemical cell was prepared using 50 ml of a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 M lithium perchlorate, and the negative electrode active material electrode according to the present invention was evaluated. .

The charge / discharge conditions are based on lithium standard (vs. Li / Li ⁺ ) and charged at a constant current of 0.25 mA / cm ² up to 0.2V, and discharged at the same current density up to 3.0V. I did it. The measurement results are shown in Table 1. In Table 1, “capacity maintenance ratio” is defined as “ratio of discharge capacity at 30th cycle to discharge capacity at 1st cycle”.

From Table 1, the negative electrode active materials of Examples 1 and 2 of the present invention have an average discharge potential of 1.50 V (vs. Li ^/ Li ⁺ ) or less, a capacity retention rate of 85% or more, and an average discharge potential of low. Therefore, it was found that a high energy density battery was obtained and charge / discharge cycle characteristics were excellent.

  On the other hand, the negative electrode active materials of Comparative Examples 1 and 2 had a capacity retention rate of about 90% and excellent charge / discharge cycle characteristics, but the average discharge potential was noble and it was difficult to obtain a high energy density battery. I understood it.

[Examples 3 to 5 and Comparative Examples 3 to 5]
[Example 3]
Oxyhydroxide obtained by coprecipitation _{(Ni 0.5 Mn 0.5} OOH) of Example 1, in the same manner as in Example 1 except that heat treatment was carried out at 600 ° C., to the present invention The negative electrode active material Ni _0.5 Mn _0.5 O _1.43 of Example 3 was obtained. This is designated as negative electrode active material A3.

[Example 4]
The oxyhydroxide (Ni _0.5 Mn _0.5 OOH) obtained by the coprecipitation method of Example 1 is subjected to the present invention in the same manner as Example 1 except that the heat treatment is performed at 1000 ° C. The negative electrode active material Ni _0.5 Mn _0.5 O _1.43 of Example 4 was obtained. This is designated as a negative electrode active material A4.

[Example 5]
Oxyhydroxide obtained by coprecipitation _{(Ni 0.5 Mn 0.5} OOH) of Example 1, except that heat treatment was performed at 1200 ° C. in the same manner as in Example 1, the present invention The negative electrode active material Ni _0.5 Mn _0.5 O _1.43 of Example 5 was obtained. This is designated as negative electrode active material A5.

[Comparative Example 3]
The oxyhydroxide (Ni _0.5 Mn _0.5 OOH) obtained by the coprecipitation method of Example 1 was directly used as a negative electrode active material without heat treatment. This is designated as a negative electrode active material B3.

[Comparative Example 4]
The oxyhydroxide (Ni _0.5 Mn _0.5 OOH) obtained by the coprecipitation method of Example 1 was subjected to heat treatment at 150 ° C. in the same manner as in Example 1, except that Comparative Example 4 A negative electrode active material was obtained. This is designated as a negative electrode active material B4.

[Comparative Example 5]
The oxyhydroxide (Ni _0.5 Mn _0.5 OOH) obtained by the coprecipitation method of Example 1 was subjected to heat treatment at 350 ° C. in the same manner as in Example 1, except that Comparative Example 5 A negative electrode active material was obtained. This is designated as a negative electrode active material B5.

  A negative electrode plate was produced in the same manner as in Example 1 using the negative electrode active materials A3 to A5 of Examples 3 to 5 and the negative electrode active materials B3 to B5 of Comparative Examples 3 to 5. Using this negative electrode plate, 30 cycles of charge and discharge were performed under the same conditions as in Example 1. The measurement results are shown in Table 2. Table 2 also shows the results of Example 1 for comparison.

As can be seen from Table 2, in Comparative Example 3 in which oxyhydroxide (Ni _0.5 Mn _0.5 OOH) was used as the negative electrode active material without any heat treatment, the average discharge potential was more noble than 1.5V. It was found that the capacity retention rate was extremely small and the charge / discharge cycle performance was inferior. This is thought to be due to adsorbed water and crystal water present in the oxyhydroxide.

Further, in Comparative Example 4 in which the oxyhydroxide was heat-treated at 150 ° C. and Comparative Example 5 in which the oxyhydroxide was treated at 350 ° C., the average discharge potential was nobler than 1.6 V, and the capacity retention rate was 49% or 63 % Charge / discharge cycle performance was found to be inferior. In these negative electrode active materials, since the heat treatment temperature is low, hydrogen of oxyhydroxide, adsorbed water, crystal water and the like are not completely removed, and Ni _0.5 Mn _0.5 O _1.43 This is probably due to the fact that

On the other hand, in Examples 3, 1, 4 and 5 in which the heat treatment temperature of the oxyhydroxide was 600 ° C. or higher, the average discharge potential was lower than 1.5 V, and the capacity retention rate was 80 %, Excellent charge / discharge cycle performance was exhibited. Thus, it was found that Ni _0.5 Mn _0.5 O _1.43 free of hydrogen, adsorbed water, crystal water and the like can be obtained by heat-treating the oxyhydroxide at 600 ° C. or higher.

  In addition, when a negative electrode having a relatively base potential and a positive electrode active material are combined as in the negative electrode active materials of Examples 3, 1, 4, and 5, a non-aqueous electrochemical cell having a higher energy density is combined. Is obtained.

[Examples 6 and 7 and Comparative Examples 6 and 7]
[Example 6]
In ion-exchanged water, 4.50 g of nickel hydroxide (Ni (OH) ₂ ) and 5.28 g of manganese hydroxide (Mn (OH) ₂ ) (Ni / Mn molar ratio 0.45: 0.55) were dissolved. - except that dispersed in the same manner as in example 1 to obtain a negative electrode active material _Ni 0.45 _{Mn 0.55} O _1.43 example 7 according to the present invention. This is designated as negative electrode active material A6.

[Example 7]
In ion-exchanged water, 5.50 g of nickel hydroxide (Ni (OH) ₂ ) and 4.32 g of manganese hydroxide (Mn (OH) ₂ ) (Ni / Mn molar ratio 0.55: 0.45) were dissolved. - except that dispersed in the same manner as in example 1 to obtain a negative electrode active material _Ni 0.55 _{Mn 0.45} O _1.43 example 6 according to the present invention. This is designated as negative electrode active material A7.

[Comparative Example 6]
In ion-exchanged water, 4.00 g of nickel hydroxide (Ni (OH) ₂ ) and 5.78 g of manganese hydroxide (Mn (OH) ₂ ) are dissolved (molar ratio of Ni and Mn 0.40: 0.60). - except that dispersed in the same manner as in example 1 to obtain a negative electrode active material _Ni 0.40 _{Mn 0.60} O _1.43 Comparative example 6 according to the present invention. This is designated as a negative electrode active material B6.

[Comparative Example 7]
Dissolve 6.00 g of nickel hydroxide (Ni (OH) ₂ ) and 3.84 g of manganese hydroxide (Mn (OH) ₂ ) in ion-exchanged water (molar ratio of Ni and Mn: 0.60: 0.40) - except that dispersed in the same manner as in example 1 to obtain a negative electrode active material _Ni 0.60 _{Mn 0.40} O _1.43 Comparative example 7 according to the present invention. This is designated as a negative electrode active material B7.

  A negative electrode plate was produced in the same manner as in Example 1 using the negative electrode active materials A3 to A5 of Examples 3 to 5 and the negative electrode active materials B3 to B5 of Comparative Examples 3 to 5. Using this negative electrode plate, 30 cycles of charge and discharge were performed under the same conditions as in Example 1. Table 3 shows the measurement results. Table 3 also shows the results of Example 1 for comparison.

From the results in Table 3, the average discharge potential and capacity retention ratio are related to the composition of nickel and manganese contained in the oxide containing nickel and manganese, which are negative electrode active materials, and the average discharge is reduced as the nickel content decreases. It was found that the potential became lower and the capacity retention ratio increased as the manganese content decreased. In Examples ⁶ , 1 and 7, the average discharge potential was 1.50 V ( ² V vs. Li ^/ Li ⁺ ) or less and the capacity retention rate was 80% or more.

Thus, the general formula Ni _x Mn _y O _z according to the present invention (where 0.45 ≦ x ≦ 0.55, 0.9 ≦ x + y ≦ 1.1, 1.0 ≦ z ≦ 2.0). By using the oxide containing nickel and manganese as a negative electrode active material for a non-aqueous electrolyte electrochemical cell, a non-aqueous electrolyte electrochemical cell having high energy density and excellent charge / discharge cycle performance can be obtained.

[Example 8]
Using the negative electrode active material Ni _0.5 Mn _0.5 O _1.43 used in Example 1, a negative electrode plate was produced in the same manner as in Example 1. Using this negative electrode plate, a test electrochemical cell similar to that of Example 1 was prepared, and the negative electrode active material Ni _0.5 Mn _0.5 O _1.43 was further electrochemically reduced and oxidized. It was. Electrochemical reduction was obtained by reducing to 0.2 V (vs. Li / Li ⁺ ) at a constant current of 0.25 mA / cm ² and then discharging to 3.0 V (vs. Li ^/ Li ⁺ ). The negative electrode active material is A8.

  The electrode containing the negative electrode active material A8 was incorporated into an electrochemical cell for testing similar to that in Example 1, a charge / discharge cycle test was performed under the same conditions as in Example 1, and the characteristics of Example 1 were compared. .

  The initial charge / discharge curve of Example 1 is shown in FIG. 1, and the initial charge / discharge curve of Example 8 is shown in FIG.

  In the case of Example 1 shown in FIG. 1, the irreversible capacity in the first cycle was large, but from the second cycle, the irreversible capacity became almost zero, and it was found that almost reversible charge / discharge was possible. And it turned out that this charging / discharging curve has shown the linear discharge electric potential unlike the discharge curve as a negative electrode active material of the transition metal oxide shown by the conventional literature.

  Thus, the discharge behavior of the negative electrode active material A1 used in Example 1 is similar to that of a capacitive electrode such as activated carbon, and is also a material that can be easily controlled for high rate charge / discharge and discharge depth. It was also found that it is suitable as an electrode for a non-aqueous electrolyte electrochemical cell for high rate discharge. In addition, this discharge behavior is different from the discharge behavior of a single product of nickel oxide and manganese oxide, and it is considered that a synergistic effect due to the solid solution of nickel and manganese was observed.

  On the other hand, in the case of Example 8 shown in FIG. 2, it was found that the active material had almost no irreversible capacity from the first cycle.

  Next, FIG. 3 shows X-ray diffraction patterns of the negative electrode active material A1 used in Example 1 and the negative electrode active material A8 used in Example 8 using CuKα rays. In FIG. 3, a shows the X-ray diffraction pattern of the negative electrode active material A1, and b shows the X-ray diffraction pattern of the negative electrode active material A8.

  As is clear from FIG. 3, the negative electrode active material A1 has a cubic spinel structure, whereas the X-ray diffraction pattern of the negative electrode active material A8 shows 10 ° <2θ < The diffraction peak in the range of 70 ° completely disappeared. Further, in the X-ray diffraction pattern of the negative electrode active material A8, the half width of the diffraction peak appearing at 15 ° <2θ <20 ° and 30 ° <2θ <45 ° is 5 except for the peak due to the current collector Cu and polypropylene. It was at least (2θ). As a result, the negative electrode active material A8 was found to be amorphous.

Thus, it was found that the negative electrode active material A8 produced through an electrochemical reduction and oxidation process has almost no initial irreversible capacity and is an ideal negative electrode active material in a discharged state. That is, lithium can be introduced into the negative electrode by electrochemically reducing the oxide containing nickel and manganese, which is the negative electrode active material of the present invention, in an organic electrolyte containing lithium ions. A non-aqueous electrochemical cell combined with a positive electrode active material such as MnO ₂ or V ₂ O ₅ without a source can be produced. In addition, when a battery is assembled by partially introducing lithium into the negative electrode active material in advance, a large irreversible capacity can be offset.

  Note that here, an electrochemical method is exemplified as a method for manufacturing an amorphous or nanosized oxide containing nickel and manganese, but in addition to the electrochemical method, reduction with an organic complex containing lithium is also possible. It is also possible to use a chemical method in which lithium is occluded by an organic solvent.

Shows a negative electrode active material _{A1 (Ni 0.5 Mn 0.5 O 1.43} ) charge-discharge curve of the first cycle and the second cycle of Example 1. The figure which shows the charging / discharging curve of the 1st cycle of the amorphous | non-crystalline negative electrode active material A8 of Example 8. FIG. The figure which shows the X-ray-diffraction pattern of negative electrode active material A1 of Example 1, and negative electrode active material A8 of Example 8.

Claims (4)

Includes nickel and manganese represented by the general formula Ni _x Mn _y O _z (where 0.45 ≦ x ≦ 0.55, 0.9 ≦ x + y ≦ 1.1, 1.0 ≦ z ≦ 2.0) An anode active material for a non-aqueous electrolyte electrochemical cell, characterized by using an oxide. (However, the case where x / (x + y) = 0.5 is excluded.) 2. The half width of a diffraction peak appearing at 15 ° <2θ <20 ° and 30 ° <2θ <45 ° in an X-ray diffraction method using CuKα rays is 5 ° (2θ) or more. The negative electrode active material for nonaqueous electrolyte electrochemical cells as described. The non-aqueous electrolyte according to claim 1 or 2, wherein the oxide containing nickel and manganese is obtained by heat-treating an oxyhydroxide containing nickel and manganese at a temperature of 600 ° C or higher and 1000 ° C or lower. Negative electrode active material for electrochemical cells. A non-aqueous electrolyte electrochemical cell, characterized by using a negative electrode active material according to any one of claims 1-3.

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