JP3245609B2 - Electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art In a non-aqueous electrolyte battery using an alkali metal such as lithium, an alkaline earth metal such as magnesium, or an alloy or compound thereof as a negative electrode active material, an insertion reaction of a negative electrode metal ion into a positive electrode active material is performed. Alternatively, a large discharge capacity and charge reversibility are ensured by the intercalation reaction.

Conventionally, as a secondary battery using lithium as a negative electrode active material, V ₂ O ₅ , LiCoO ₂ , LiN which can serve as an intercalation host for lithium is used.
A proposal using a layered oxide such as iO ₂ or a tunnel oxide as a positive electrode material has been proposed. However, since these oxides use a rare metal having an extremely small number of Clarks as a central metal, a problem in terms of cost increases with mass production and enlargement.

On the other hand, batteries using an iron-based compound which is abundant in resources and highly economical as a positive electrode material have been proposed. However, this battery has many practical difficulties in terms of cycle life, discharge voltage and its flatness.

In this connection, relatively inexpensive ferric sulfate (F
A method using e ₂ (SO ₄ ) ₃ ) as a positive electrode active material is known. According to the battery using this, a flat discharge voltage of 3.6 V can be obtained.

However, in the above battery, iron trivalent / 2
Discharge capacity is 134 mAh by multivalent redox reaction
/ G, which is low, and there is still room for improvement. In addition, the electron conductivity is also insufficient, and it is necessary to improve in this respect as well.

[0007]

As described above, in the prior art, at present, a technique for providing a non-aqueous electrolyte battery having low cost and excellent charge / discharge characteristics has not yet been established. This is also an obstacle to manufacturing large non-aqueous electrolyte batteries.

Accordingly, an object of the present invention is to provide a non-aqueous electrolyte battery which can exhibit excellent charge / discharge characteristics at low cost.

[0009]

Means for Solving the Problems In view of these problems of the prior art, the present inventors have conducted intensive studies and found that a battery having an electrode using a specific electrode material can achieve the above object. The present invention has been completed.

That is, the present invention relates to the following nonaqueous electrolyte secondary battery electrode and nonaqueous electrolyte secondary battery.

1. Formula _{Li n Cu 2 (XO 4)} 3 ( where,
X is an electrode for a non-aqueous electrolyte secondary battery including, as an electrode active material, a material represented by at least one of Group VIa elements and Group VIb elements (excluding oxygen), 0 <n ≦ 6.

2. A non-aqueous electrolyte secondary battery using the electrode according to claim 1 as a positive electrode.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The non-aqueous electrolyte secondary battery of the present invention have the general formula _{Li n Cu 2 (XO 4)} 3 ( where, X is at least VIa group elements and group VIb elements (excluding oxygen) One,
0 <n ≦ 6) is included as an electrode active material.

X represents at least one of a VIa group element and a VIb group element. That is, Cr as a VIa group element,
There are Mo and W, and there are S, Se, Te and Po as Group VIb elements, and one or more of these can be used. Among them, the present invention preferably contains Mo.

In the general formula, n is usually 0.
<N ≦ 6, preferably 2 ≦ n ≦ 4.
When n exceeds 6, a crystal structure as shown in FIG. 1 described later is not formed, and desired electrode characteristics may not be obtained.

The above materials can be manufactured by a known method. For example, when manufacturing a material in which X = Mo, cupric oxide (CuO) or cuprous oxide (Cu
And ₂ O), after the molybdenum oxide (MoO ₃₎ and lithium carbonate (Li ₂ CO ₃₎ were mixed at a predetermined ratio, it can be obtained by firing in an oxidizing atmosphere or in air. In this case, the value of n can be arbitrarily changed by appropriately changing the amount of lithium carbonate added. As the above materials, commercially available products can be used as they are. The material may be any of a mixture of oxides, a double oxide and the like as long as predetermined electrode characteristics can be obtained.

In the electrode of the present invention, the above materials are used as an electrode active material. In this case, the above-mentioned material may be usually used in the form of powder, and the average particle size may be about 1 to 20 μm. The content of the above-mentioned material in the electrode may be appropriately set according to the type of the material to be used, the amount of the binder and the conductive material used, and the like.

The production of the electrode of the present invention may be carried out according to a known method for producing an electrode, except that the above-mentioned material is used as an electrode active material as described above. For example, a known binder (polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, ethylene propylene diene polymer, or the like) may be used as needed, and a known conductive material (acetylene black, (Carbon, graphite, etc.) and then press-molding the obtained mixed powder on a stainless steel support or filling a metal container. Alternatively, a slurry obtained by mixing the mixed powder with an organic solvent (N-methylpyrrolidone, toluene, cyclohexane, etc.) is mixed with aluminum,
The electrode of the present invention can also be produced by a method such as coating on a metal substrate such as nickel.

The nonaqueous electrolyte secondary battery of the present invention can employ the components of a known nonaqueous electrolyte secondary battery except that the electrode of the present invention is used as a positive electrode.

For the negative electrode, it is preferable to use at least one of an alkali metal material and an alkaline earth metal material as an electrode active material. The alkali metal material according to the present invention,
In addition to alkali metals such as Li, K, and Na, alkali metal compounds, alloys, and the like, materials capable of occluding and releasing alkali metal ions (eg, Li _2.5 Co _0.5 N, Li
₄ Ti ₅ O _12, etc.) are also included. In addition, the alkaline earth metal materials include, in addition to alkaline earth metals such as Mg, Ca, and Sr, compounds and alloys of alkaline earth metals, and materials capable of occluding and releasing alkaline earth metal ions. included. Note that a binder, a conductive material, and the like can be added to the negative electrode as needed.

The preparation of the negative electrode may be in accordance with a known method. For example, a mixed powder of these electrode materials is formed into a sheet,
This is a conductor network (collector) of nickel, stainless steel, etc.
Can be manufactured by crimping.

The solvent of the electrolytic solution is not particularly limited as long as it is a non-aqueous solvent. For example, dimethoxy ethane, 2-methyltetrahydrofuran, ethylene carbonate, methyl formate, dimethyl sulfoxide, propylene carbonate, acetonitrile, butyrolactone, dimethylformamide, dimethyl carbonate , Diethyl carbonate, sulfolane, ethyl methyl carbonate and the like can be used. These can be used alone or in combination of two or more. As an electrolytic solution, LiClO ₄ , L
_{iPF 6, LiBF 4, LiCF 3} SO 3, obtained by dissolving LiAsF known electrolytes such as ₆ (solute) can be used.
In the present invention, a known solid electrolyte or the like can be used.

In the battery of the present invention, conventionally known various materials can be used for the elements such as the separator and the battery case, and there is no particular limitation.

The battery of the present invention may be assembled using these battery elements according to a known method. In this case, the shape of the battery is not particularly limited, and various shapes and sizes such as a cylindrical shape, a square shape, and a coin shape can be appropriately adopted.

[0025]

As shown in FIG. 1, the basic structural unit of Cu ₂ (XO ₄ ) ₃ (portion surrounded by a and b) is composed of two octagons each having an oxygen atom at each corner and Cu (● mark) at the center. Face CuO
₆ and oxygen atoms at each corner and group VI metal element X at the center
It consists of three XO ₄ with (o), one oxygen atom is shared by one octahedral group and one tetrahedral group. In this so-called NASICON-type basic skeleton, there is no face sharing or edge sharing, only vertex sharing, so each Li
One of the characteristics is that the bottleneck of the site diffusion is large and the sites are three-dimensionally connected to each other, whereby high Li diffusivity can be maintained.

No by-products other than carbon dioxide are generated,
Pollution-free, simple and inexpensive production is possible.

[0027]

According to the present invention, since a specific material is used as an electrode active material, a non-aqueous electrolyte secondary battery having particularly excellent charge / discharge characteristics, a large capacity and a long cycle life can be provided at low cost. it can. For this reason, the electrode or battery of the present invention is also suitable as a large-sized battery, which can be expected to further expand applications.

[0028]

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. In the examples, the production and measurement of the battery were performed in a dry box under an argon atmosphere.

Example 1 FIG. 2 is a sectional view of a coin-type battery which is a specific example of the battery according to the present invention. This battery is mainly composed of a sealing plate (1), a gasket (2), a positive electrode case (3), a negative electrode (4), a separator (5) and a positive electrode mixture pellet (6).
It is composed of

The sealing plate and the positive electrode case were made of stainless steel, and the gasket was made of polypropylene.
The separator used was made of polypropylene and was microporous.

The positive electrode material mixture pellets were produced as follows. First, cupric oxide (CuO) and molybdenum oxide (MoO ₃ ) are mixed with lithium carbonate (Li ₂ CO ₃ ) in a stoichiometric ratio of 1: 2: 3 according to the following reaction formula.
After calcining at 650 ° C. for 6 hours in the air, remix,
A sample was prepared by baking in air at 80 ° C. for 2 days.

Li ₂ CO ₃ + 2CuO + 3MoO ₃ → Li ₂
Cu ₂ (MoO ₄ ) ₃ + CO ₂を The obtained sample was subjected to powder X-ray diffraction analysis. The result is shown in FIG.
Shown in As shown in FIG. 3, this sample was monoclinic Li ₂ C
u ₂ (MoO ₄ ) ₃ was confirmed.

Next, this sample was pulverized to a powder (average particle size of about 10 μm) and used as a positive electrode active material. This was used as a conductive material (acetylene black) 25% by weight and a binder (polytetrafluoroethylene). ) 5% by weight, and then roll-formed to form a positive electrode mixture pellet (0.5 m thick).
m, diameter 15 mm).

Next, a metal lithium negative electrode (4) placed under pressure on the sealing plate (1) is inserted into the recess of the gasket (2), and a separator (5) and a positive electrode mixture pellet are placed on the negative electrode. (6) was arranged in this order, and a 1 N solution of LiPF ₆ dissolved in an equal volume mixed solvent of ethylene carbonate and dimethyl carbonate as an electrolytic solution was injected in an appropriate amount and impregnated. Then, the positive electrode case (3) was covered. By caulking, a coin-type lithium battery (battery a) having a thickness of 2 mm and a diameter of 23 mm was produced.

FIG. 4 shows a pseudo open potential curve at a current density of 0.2 mA / cm ² in the battery a. It can be seen that the discharge overvoltage is small except at the end of the first discharge flat portion of 2.5 V. A 6-electron reaction was possible by the end of the 1.5 V discharge.

[0036] The batteries a prepared in the same manner as in Example 1 shows the discharge curve of 1.5V termination at a current density of 0.5 mA / cm ² and 1 mA / cm ² in FIG. Since the discharge overvoltage is small and the flatness of the discharge profile is maintained even at a relatively high current density of 1 mA / cm ² ,
It can be seen that the high discharge capacity for the six-electron reaction is not impaired.

Example 3 A battery a produced in the same manner as in Example 1 was examined for 3.8 V-2 V voltage regulation charge / discharge characteristics at a charge / discharge current density of 0.2 mA / cm ² . The charge / discharge curve is shown in FIG.

From the results shown in FIG. 6, the reversible cycle capacity is about 150 mAh / g, and the theoretical capacity is 134 mAh / g.
It can be seen that the battery exhibited better characteristics than the battery using ferric sulfate as the positive electrode active material.

[Brief description of the drawings]

FIG. 1 shows an embodiment of Li ₂ Cu ₂ (Mo) according to the present invention.
O _{4) 3} of M ₂ (XO _{4) 3} is a schematic diagram illustrating the basic structural unit.

FIG. 2 is a structural sectional view of a coin-type battery as one specific example of the present invention.

FIG. 3 shows a monoclinic Li ₂ Cu ₂ (M
FIG. 2 is an X-ray diffraction diagram of oO ₄ ) ₃ .

FIG. 4 shows an embodiment of the present invention, Li ₂ Cu ₂ (Mo
O ₄₎ is a characteristic diagram showing a _third pseudo open voltage curve.

FIG. 5 is a diagram showing an embodiment of the present invention, Li ₂ Cu ₂ (Mo
FIG. 4 is a characteristic diagram showing a discharge curve at the end of 1.5 V at each current density of O ₄ ) ₃ .

FIG. 6 shows a charge / discharge current density of 0.2 mA /
It is a characteristic diagram showing a 3.8 V-2V Voltage regulating the charge-discharge curves in cm ^2.

[Explanation of symbols]

 1 stainless steel sealing plate 2 polypropylene gasket 3 stainless steel positive electrode case 4 lithium negative electrode 5 polypropylene separator 6 positive electrode mixture pellet

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Kageyama 1-38-31 Midorioka, Ikeda-shi, Osaka Prefecture Inside the Osaka Institute of Technology (72) Inventor Teruo Kodama 1--8-3 Midorioka, Ikeda-shi, Osaka No. 31 Masayuki Miyake, Examiner, Osaka Institute of Technology, Institute of Industrial Science (56) References JP-A-5-290850 (JP, A) JP-A-9-35717 (JP, A) JP-A-9-171828 (JP, A) JP-A-10-223222 (JP, A) "Electrochemistry and Industrial Physical Chemistry", The Chemical Society of Japan, October 5, 1997, Vol. 65, No. 10, pp. 802-808 (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/48-4/58 H01M 4/02-4/04 H01M 10/40 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A general formula _{Li n Cu 2 (XO 4)} 3 ( where, X is
An electrode for a non-aqueous electrolyte secondary battery comprising, as an electrode active material, a material represented by at least one of Group VIa elements and Group VIb elements (excluding oxygen), 0 <n ≦ 6. 2. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein X contains Mo. 3. A non-aqueous electrolyte secondary battery using the electrode according to claim 1 as a positive electrode. 4. The non-aqueous electrolyte secondary battery according to claim 3, wherein an electrode containing at least one of an alkali metal material and an alkaline earth metal material as an electrode active material is used as a negative electrode.