JP3354611B2 - Non-aqueous electrolyte secondary battery and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery using a material capable of inserting and extracting lithium as a negative electrode active material and / or a positive electrode active material and using a lithium ion conductive non-aqueous electrolyte. More particularly, the present invention relates to a novel negative electrode active material and a new positive electrode active material which provide a new secondary battery having high voltage, high energy density, excellent charge / discharge characteristics, and a long cycle life.

[0002]

2. Description of the Related Art A non-aqueous electrolyte battery using lithium as a negative electrode active material has advantages such as high voltage, high energy density, small self-discharge, and excellent long-term reliability. It is already widely used as a power source for cameras and the like.

However, with the remarkable development of portable electronic devices and communication devices in recent years, a variety of devices that require a large current output from a battery as a power supply have appeared, which has led to economical efficiency and reduction in size and weight of the devices. From the viewpoint, there is a strong demand for a secondary battery that can be recharged and discharged and has a high energy density. For this reason, research and development for promoting the conversion of the non-aqueous electrolyte battery having a high energy density into a secondary battery has been actively carried out, and some of them have been put to practical use. However, energy density, charge / discharge cycle life, reliability, etc. Not enough.

Conventionally, as a positive electrode active material constituting a positive electrode of this type of secondary battery, the following three types are used depending on the form of charge / discharge reaction.
Species types have been found. The first type is a metal chalcogenide such as TiS ₂ , MoS ₂ , NbSe ₃ , MnO ₂ , MoO ₃ , V ₂ O ₅ , Li _X CoO ₂ ,
_{Li X NiO 2, Li x Mn} 2 O 4 or the like as a so metal oxides, only crystals of the interlayer and the grating position or the interstitial gap lithium-ion (cation) of intercalation and deintercalation reactions and the like Type that comes in and out.

[0005] The second type is a type in which only anions mainly come in and out by stable doping and undoping reactions, such as conductive polymers such as polyaniline, polypyrrole, and polyparaphenylene. The third type is a type (intercalation, deintercalation or doping, undoping, etc.) in which both lithium cations and anions can enter and exit, such as graphite intercalation compounds and conductive polymers such as polyacene. .

On the other hand, as the negative electrode active material constituting the negative electrode of this type of battery, since the electrode potential is the lowest when metallic lithium is used alone, it is combined with the positive electrode using the above positive electrode active material. Although the battery has the highest output voltage and the highest energy density, it is preferable. However, dendrites and passive compounds are generated on the negative electrode during charging and discharging, and there is a problem that the deterioration due to charging and discharging is large and the cycle life is short. In order to solve this problem, (1) lithium and Al, Zn, Sn, Pb, Bi, Cd
(2) WO ₂ , MoO ₂ , Fe
Inorganic compounds such as ₂ O ₃ , TiS ₂ , graphite, intercalation compounds or insertion compounds in which lithium ions are occluded in the crystal structure of a carbonaceous material obtained by calcining an organic substance, and (3) doping lithium ions It has been proposed to use a material capable of inserting and extracting lithium ions, such as conductive polymers such as polyacene and polyacetylene.

[0007]

However, in general, a negative electrode using a material capable of inserting and extracting lithium ions other than lithium metal as described above and a positive electrode active material as described above are used as the negative electrode active material. When a battery is configured by combining the positive electrode and the positive electrode, the operating voltage of the battery is higher than that of the negative electrode active material because the electrode potential of these negative electrode active materials is more noble than the electrode potential of metallic lithium. There is the disadvantage that it is much lower. For example, lithium and A
l, Zn, Pb, Sn, Bi, 0.2~0.8V in the case of using an alloy of Cd, etc., carbon - 0 to 1 V in a lithium intercalation compound, a lithium ion insertion compound such as MoO ₂ and WO ₂ 0 The operating voltage is reduced by 0.5 to 1.5 V.

In addition, since elements other than lithium also constitute the negative electrode, the capacity and energy density per volume and weight are significantly reduced. Further, when the alloy of lithium and another metal of the above (1) is used, the efficiency of use of lithium during charge and discharge is low, and cracks occur in the electrodes due to repetition of charge and discharge, causing cracks and the like. Therefore, there is a problem that the cycle life is short, and in the case of the lithium intercalation compound or the insertion compound of (2), deterioration such as collapse of a crystal structure or generation of an irreversible substance due to overcharging / discharging occurs, and a high electrode potential ( There is a drawback that the output potential of a battery using the same is low because there are many precious materials. In the case of the conductive polymer of (3), the charge / discharge capacity, particularly, the charge / discharge capacity per volume is small. There's a problem.

Therefore, in order to obtain a secondary battery having a high voltage, a high energy density, excellent charge / discharge characteristics, and a long cycle life, an electrode potential with respect to lithium is low (low) and lithium during charge / discharge is required. It is necessary to use a negative electrode active material which is free from deterioration such as collapse of a crystal structure and generation of an irreversible substance due to occlusion and release of ions, and has a large amount capable of reversibly storing and releasing lithium ions, that is, an effective charge / discharge capacity.

On the other hand, the above-mentioned positive electrode active material of the first type generally has a large energy density, but has a drawback that when overcharged or overdischarged, degradation due to crystal collapse or generation of an irreversible material is large. . On the other hand, the second and third types have a disadvantage that the capacity and the energy density are small.

Therefore, in order to obtain a secondary battery having excellent overcharge characteristics and overdischarge characteristics and a high capacity and a high energy density, there is no collapse of crystals or generation of irreversible substances due to overcharge and overdischarge, and It is necessary to use a positive electrode active material having a large amount capable of reversibly storing and releasing lithium ions.

[0012]

According to the present invention, a divalent oxide can be produced as an active material of at least one of a negative electrode and a positive electrode of a battery of this type in order to solve the above problems. A compositional formula Li obtained by heating a metal or a class of metals M and lithium Li alone or a mixture of these compounds in an atmosphere in which the amount of oxygen or oxygen partial pressure is controlled so that the valence of M is divalent. _2x MO _{1 + x} (where x> 0), or further lithium is occluded in the composite oxide by an electrochemical reaction between the composite oxide and lithium or a lithium-containing material; Or a novel lithium ion occluding and releasing substance comprising a composite oxide represented by a composition formula Li _{2x + y} MO _{1 + x} (2x + y ≧ 0) obtained by releasing lithium from the composite oxide by an electrochemical reaction Using It is intended to raise.

That is, a starting material is a metal or a similar metal M capable of forming a divalent oxide and lithium or a compound of lithium Li, or a starting material thereof, in an atmosphere and at a temperature in which the valence of M is controlled to be divalent. Solid state reaction or melting reaction process by direct heating of the mixture of the above, or a heating reaction process such as a method of heating after a chemical reaction in a solution of the starting material, and the composition formula Li _2x MO _{1 + x} (however, x> 0)
Is synthesized.

After that, lithium is further inserted into the composite oxide by an electrochemical reaction between the obtained composite oxide and lithium or a lithium compound, or lithium is released from the composite oxide by an electrochemical reaction. Oxide L whose lithium content has increased or decreased due to
i _{2x + y} MO _{1 + x} (2x + y ≧ 0) is used as an active material.

The above-mentioned composite oxide Li _2x MO _{1 + x} synthesized in advance by a heating reaction process is formally expressed as MO · x
Li ₂ O, which can form a divalent oxide in the form of a chemical composition.
And lithium oxide Li ₂ O are oxides in the form of a solid-phase reaction at a molar ratio of 1: x, and the valence of the metal or the like metal M is divalent. A composite oxide containing lithium and capable of inserting and extracting lithium ions in a non-aqueous electrolyte by an electrochemical reaction. Metal or similar metal M constituting the composite oxide
Examples include transition metals such as Fe, Mn, Ti, V, Nb, Co, and Ni; other metals such as Zn, Cd, Mg, Ba, Pb, and Sn; and similar metals such as Si, B, Ge, and Sb. Which can generate the divalent oxide or monoxide MO of

As described above, the standard composition ratio of such a metal or a metal M and oxygen O is 1: 1 + x. However, in the synthesis, an indefinite ratio due to the deficiency or excess of the metal or the metal M or oxygen O is often used. Yields a specific compound, whose non-stoichiometric range varies depending on the type of M but extends to ± 25%.

Such nonstoichiometric compositions are also included in the present invention. In particular, when a transition metal or silicon Si is used as M, a compound having a high non-stoichiometric ratio due to deficiency of M or oxygen O is easily generated, and thus lithium ions are formed in the crystal structure or amorphous structure of the product. There are many sites that can occlude,
It is particularly advantageous because it has a high mobility of lithium ions and a high electron conductivity, and has a large charge / discharge capacity and a small polarization. The lithium content x and y of the composite oxide Li _{2x + y} MO _{1 + x}
As long as the composite oxide is in a stable range, the range of 0 <x ≦ 2 and 0 <2x + y ≦ 2x + 2 is particularly preferable because deterioration due to charging and discharging is small.

The composite oxide used as the active material of the negative electrode and / or the positive electrode of the battery of the present invention can be specifically produced as follows. The above-mentioned metal or the like metal M capable of forming a divalent oxide and lithium Li alone or a compound thereof are mixed at a predetermined molar ratio as a starting material, or while the metal or the like metal M is mixed. Is heated in an atmosphere in which the amount of oxygen or the oxygen partial pressure is controlled so that the valence or oxidation number of the compound becomes about 2, and the composition formula Li _2x M
A composite oxide of O _{1 + x} (where x> 0) is used. As the respective compounds of the metal or the class of metals and lithium as starting materials, the respective oxides, hydroxides, salts such as carbonates and nitrates or organic compounds, etc., are placed in an inert atmosphere. Alternatively, a compound which generates each oxide or simple substance by heating in vacuum is preferable.

As a method of mixing these starting materials, in addition to a method of directly dry-mixing the powders of these materials, these materials are dissolved or dispersed in water, alcohol, or other solvents, and then uniformly mixed in the solution. Various methods are possible, such as a method of drying after mixing or reacting these materials, a method of atomizing or ionizing these materials by heating, electromagnetic waves, light, or the like, and simultaneously or alternately depositing or depositing them.

The temperature at which the raw materials are mixed or heated while mixing varies depending on the starting materials and the heating atmosphere, but synthesis can be carried out at 300 ° C. or higher, preferably 600 ° C. or higher. More preferably, the temperature is 700 ° C. or higher. Of these starting material combinations, M
MO, M (OH) ₂ , MCO ₃ , M (NO ₃ ) ₂
M divalent compounds having oxygen such as LiOH and Li
A combination of a lithium compound such as ₂ O, Li ₂ CO _3, or LiNO ₃ which generates lithium oxide by heating with a molar ratio of M: Li of 1: 2 ×, and a simple substance of M and M ₃ O ₄ or M
Higher oxides of M such as ₂ O ₃ and MO ₂ or M (OH) ₃ and M ₂
(CO _{3) 3} or M (NO ₃₎ 3 of M with oxygen, such as _3, etc.
The total molar ratio of M: Li of the compound having a valency of more than ₂ and a lithium compound such as LiOH, Li ₂ O, Li ₂ CO ₃ or LiNO ₃ which generates lithium oxide by heating is 1: 2 ×, and the average atom of M In a combination where the valency is divalent, the composition can be heated and synthesized in an inert atmosphere or an atmosphere in which oxygen is cut off, such as in a vacuum, and it is easy to control the amount of oxygen or the oxygen partial pressure in the heating atmosphere. It is easy to manufacture and particularly preferable.

For example, as the former example, MO and Li ₂ O
A molar ratio of 1: x, a molar ratio of MO and LiOH of 1: x
A combination of 2x, a combination of MCO ₃ and Li ₂ CO _{3 at} a molar ratio of 1: x, etc. Examples of the latter are a combination of M, MO ₂ and Li ₂ O at a molar ratio of 1: 1: 2x, M and M (OH) ₃ and L
a combination of 1: 2: 6x molar ratio with iOH, M and M (NO
₃ ) Combinations of ₃ and LiNO _{3 in} a molar ratio of 1: 2: 6x, and the like.

When M is an oxide which is stable among oxides and its oxidation number is hardly changed by heating, it can be synthesized by heating in air. The composite oxide Li _2x MO _{1 + x} thus obtained
Can be used as an active material of a negative electrode and / or a positive electrode as it is or after being subjected to processing such as pulverization and sizing or granulation as necessary. In addition, as described below, this lithium-containing composite oxide Depending on the electrochemical reaction between the substance Li _2x MO _{1 + x} and the metallic lithium or the substance containing lithium, the composite oxide can further absorb lithium ions or, on the contrary, release lithium ions from the composite oxide Depending on this, a material with an increased or decreased lithium content may be used as an active material.

Examples of the lithium-containing substance to be used in the electrochemical reaction include, for example, insertion and extraction of lithium ions such as those used for the positive electrode active material or the negative electrode active material mentioned in the section of the prior art. Possible materials can be used. Occlusion and release of lithium ions by such an electrochemical reaction can be performed in the battery after the battery is assembled, or inside or outside the battery in the course of the battery manufacturing process. Can be performed in the following manner.

That is, (1) the composite oxide Li _2x MO _{1 + x}
Alternatively, one obtained by molding a mixture thereof with a conductive agent, a binder and the like into a predetermined shape is used as one electrode (working electrode) and a metal containing lithium or a substance containing lithium is used as the other electrode (counter electrode). An electrochemical cell is constructed by contacting both electrodes in contact with an ion-conductive non-aqueous electrolyte, and an appropriate current is applied in the direction in which the working electrode undergoes a cathodic reaction to electrochemically convert lithium ions into the complex oxide. How to make the material occlude. A non-aqueous electrolyte secondary battery is formed by using the obtained working electrode as it is as a negative electrode and / or a positive electrode or as an active material constituting a negative electrode and / or a positive electrode.

(2) The composite oxide Li _2x MO _{1 + x} or a mixture thereof with a conductive agent and a binder is formed into a predetermined shape, and lithium or an alloy of lithium or the like is pressed or contacted thereto. The stacked battery is incorporated into a non-aqueous electrolyte secondary battery as an electrode. A method in which the laminated electrode contacts the electrolyte in the battery to form a kind of local battery, self-discharges, and electrochemically occludes lithium in the composite oxide.

(3) Non-aqueous solution using the composite oxide Li _2x MO _{1 + x} as an active material of one electrode and the other electrode containing a material containing lithium and capable of inserting and extracting lithium ions as an active material. Construct an electrolyte secondary battery. A method in which lithium ions are occluded in the composite oxide by charging or discharging during use as a battery.

When lithium ions are released from the composite oxide Li _2x MO _{1 + x} to reduce the lithium content, the direction of the current is reversed in the above method (1) or (3). do it. The thus obtained composite oxide represented by the composition formula Li _{2x + y} MO _{1 + x} (where 2x + y ≧ 0 and x> 0) is used as the active material of the negative electrode and / or the positive electrode.

The composite oxide Li _{2x + y} MO according to the present invention
An electrode using _{1 + x} as an active material can be used as a positive or negative electrode active material to constitute a secondary battery, or it can be used as one of a positive electrode and a negative electrode, as described above. An electrode using various other negative electrode active materials or positive electrode active materials capable of inserting and extracting lithium or lithium ions can be used in combination as the other electrode.

In particular, the composite oxide Li _{2x + y} MO according to the present invention
An electrode using _{1 + x} as an active material has a large charge / discharge capacity in a base region where the electrode potential with respect to metallic lithium is 1.9 V or less,
In addition, since deterioration due to overcharging and overdischarging is small, this is used as a negative electrode, and the above-mentioned V ₂ O ₅ , Li _x CoO ₂ , and Li _x Ni are used.
A high voltage, high energy density and large current are obtained by combining with a positive electrode using an active material having a high potential of 3 V or 4 V or more for metal lithium such as metal oxides such as O ₂ and Li _x Mn ₂ O _4. It is particularly preferable because a secondary battery having excellent charge / discharge characteristics and little deterioration due to overcharge and overdischarge can be obtained.

On the other hand, γ-butyrolactone, propylene carbonate, ethylene carbonate,
LiClO as a supporting electrolyte in a single or mixed organic solvent such as butylene carbonate, dimethyl carbonate, diethyl carbonate, methylformate, 1,2-dimethoxyethane, tetrahydrofuran, dioxolan, dimethylformamide, etc. _4, LiPF _6, LiB
An organic electrolyte solution in which a lithium ion dissociable salt such as F ₄ or LiCF ₃ SO ₃ is dissolved; a polymer solid electrolyte in which the lithium salt is dissolved in a polymer such as polyethylene oxide or a crosslinked polyphosphazene; or Li ₃ N , LiI, etc., as long as it is a lithium ion conductive non-aqueous electrolyte such as an inorganic solid electrolyte.

[0031]

The composite oxide Li2 _{x + y} MO of a metal or a similar metal M capable of forming the divalent oxide of the present invention and lithium Li.
An electrode using _{1 + x} as an active material stably and repeatedly absorbs and releases lithium (intercalation, deintercalation or doping) in a non-aqueous electrolyte in the range of an electrode potential of at least 0 to 3 V with respect to metallic lithium. , Undoping, etc.), and can be used as a negative electrode and / or a positive electrode of a secondary battery that can be repeatedly charged and discharged by such an electrode reaction. In particular, 0 to 1.
In a low potential region of 9 V, a high-capacity region in which lithium ions can be stably inserted and released and charged and discharged repeatedly can be provided.

Further, as compared with a carbonaceous material such as graphite which has been conventionally used as an electrode of this type of battery, the amount capable of inserting and extracting lithium ions reversibly, that is, the charge / discharge capacity is extremely large, and the charge / discharge polarization is small. Therefore, the battery can be charged and discharged with a large current, and furthermore, deterioration such as decomposition and crystal collapse due to overcharge and overdischarge is hardly observed, so that an extremely stable battery having a long cycle life can be obtained.

The reason why such excellent charge / discharge characteristics are obtained is not necessarily clear, but is presumed as follows. That is, the composite oxide Li which is a novel active material according to the present invention.
_{2x + y} MO _{1 + x} has a composition structure in which a monoxide MO and a lithium oxide Li ₂ O are reacted in a solid phase by heating, and the lithium-containing composite oxide Li _2x MO _{1 + x} is further electrochemically synthesized. Lithium ions are absorbed or lithium ions are electrochemically released from Li _2x MO _{1 + x} , and the mobility of lithium ions in this structure is high, and sites that can store lithium ions It is presumed that the absorption and release of lithium ions are easy due to the large number.

[0034]

The present invention will be described in more detail with reference to the following examples. FIG. 1 is a cross-sectional view of a coin-type battery showing an example of a test cell used in the following examples for evaluating the performance of an electrode active material of a nonaqueous electrolyte secondary battery according to the present invention.

In the drawing, reference numeral 1 denotes a counter electrode case which also serves as a counter electrode terminal, which is formed by drawing a stainless steel plate having one outer side Ni-plated.

Reference numeral 2 denotes a counter electrode current collector made of a stainless steel net, which is spot-welded to the counter electrode case 1.
The counter electrode 3 is obtained by punching an aluminum plate having a predetermined thickness to a diameter of 15 mm, fixing the aluminum plate to the counter electrode current collector 2, and punching a lithium foil having a predetermined thickness to a diameter of 14 mm thereon.

Numeral 7 is a working electrode case made of stainless steel with one outer surface Ni-plated, and also serves as a working electrode terminal.
Reference numeral 5 denotes a working electrode formed by using an active material according to the present invention described later or a comparative active material according to a conventional method, and 6 denotes a stainless steel net, a metal spring, a conductive paint or a conductive adhesive, and the like. The working electrode current collector electrically connects the working electrode 5 and the working electrode case 7 to each other.

Reference numeral 4 denotes a separator made of a porous film of polypropylene, which is impregnated with an electrolytic solution. Reference numeral 8 denotes a gasket mainly composed of polypropylene, which is interposed between the counter electrode case 1 and the working electrode case 7 to maintain the electrical insulation between the counter electrode and the working electrode and to make the opening edge of the working electrode case inward. The battery contents are sealed and sealed by being bent and crimped. The size of the battery was 20 mm in outer diameter and 1.6 mm in thickness.

Example 1 A working electrode 5 was manufactured as follows. Commercially available iron monoxide FeO and lithium hydroxide LiOH
After weighing H ₂ O and Fe: Li so as to have a predetermined molar ratio and sufficiently mixing them using a mortar, the mixture was heated in a nitrogen stream at a temperature of 900 ° C. for 12 hours, and after cooling,
It was pulverized and sized to a particle size of 53 μm or less.

The product thus obtained is used as an active material according to the present invention, and graphite is used as a conductive agent, and a crosslinkable acrylic resin is used as a binder in a weight ratio of 30: 6.
The working electrode mixture was mixed at a ratio of 5: 5 to form a working electrode mixture. Then, the working electrode mixture was mixed with a working electrode current collector 6 composed of a stainless steel net at 2 ton / cm 2 and a diameter of 15 mm and a thickness of 0.5 m.
After pressure molding into pellets of m, the pellets were dried by heating under reduced pressure at 200 ° C. for 10 hours to obtain a working electrode. In this embodiment, F
e: Li molar ratio (active material a1) 1: 1 (LiF
eO _1.5 ) and (active material a2) 1: 2 (Li ₂ FeO)
₂ ) were prepared.

For comparison, instead of the active material a1 or a2 according to the present invention, the same iron monoxide FeO used as the raw material for the above synthesis was crushed and sized to a particle size of 53 μm or less (active Except that the same graphite (active material r2) as used for the substance r1) and the conductive agent was used as the active material, respectively, in the same manner as the working electrode of the present invention described above,
A similar electrode (working electrode for comparison) was prepared.

The electrolyte was propylene carbonate and 1,2
Lithium perchlorate LiClO ₄ dissolved at 1 mol / l in a mixed solvent of 1: 1 by volume of dimethoxyethane was used. The battery thus manufactured was aged at room temperature for one week, and then subjected to a charge / discharge test described later. By this aging, the lithium-aluminum laminated electrode of the counter electrode is sufficiently alloyed by contacting the non-aqueous electrolyte in the battery, and substantially all of the lithium foil is made of Li.
Since the battery was an -Al alloy, the battery voltage was stabilized at a value reduced by about 0.4 V as compared with a case where metallic lithium was used alone as a counter electrode.

The batteries fabricated in this manner are hereinafter referred to as active materials a1, a2, r1, r2 of the working electrodes used.
, And are abbreviated as batteries A1, A2, R1, and R2, respectively. These batteries A1, A2 and R1, R2 are
Battery with a constant current of mA, a final voltage of -0.4 V for charging (a current direction in which lithium ions are absorbed from the electrolyte to the working electrode and causing a battery reaction), and discharging (a lithium ion is released from the working electrode to the electrolyte). FIG. 2 shows the charge characteristics in the third cycle and FIG. 3 shows the discharge characteristics when a charge / discharge cycle was performed under the condition of a cut-off voltage of 2.5 V (current direction in which reaction occurs).
FIG. 4 shows the cycle characteristics.

The charge / discharge cycle was started from charging. As is clear from FIGS. 2 to 4, the battery A according to the present invention
It can be seen that the charge and discharge capacities of A1 and A2 are significantly larger than those of the comparative batteries R1 and R2, and the reversible region of charge and discharge is significantly expanded. Further, a decrease in discharge capacity (cycle deterioration) due to repetition of charge and discharge is extremely small. Furthermore, the difference in operating voltage between charging and discharging is significantly reduced over the entire charging / discharging region, indicating that the polarization (internal resistance) of the battery is extremely small and that large-current charging / discharging is easy.

Example 2 In place of the active material a1 of Example 1, commercially available zinc monoxide ZnO and lithium hydroxide LiO were used.
And _{H · H 2 O Zn: Li} = 1: After thoroughly mixed using a mortar in a molar ratio, the mixture was 24 hours of heat treatment at a temperature of 850 ° C in air, after cooling, particle size 53μm The material pulverized and sized below was used as the active material of the working electrode (active material b according to the present invention). Except for the active material of this working electrode, a battery B similar to that of the battery A1 of Example 1 was produced.

The battery B thus obtained was subjected to the same charge / discharge cycle test as in Example 1. FIG. 5 shows the charge characteristics at the third cycle and FIG. 6 shows the discharge characteristics at this time.
FIG. 7 shows the cycle characteristics. As is clear from the figure, the battery B of the present embodiment is different from the batteries A1 and
It turns out that it has excellent charge / discharge characteristics like A2. That is, lithium ions are released from the Li-Al alloy of the counter electrode into the electrolyte by charging, and the lithium ions move in the electrolyte and react with the active materials a1, a2, or b of the working electrode to form an electrode. , A2 or b electrochemically occludes lithium ions and contains lithium, ie, lithium-containing composite oxides Li _{1 + y} FeO _1.5 , Li _{2 + y} FeO ₂ or Li
_{1 + y} ZnO _1.5 is produced.

Next, at the time of discharging, lithium ions are released from the composite oxide into the electrolyte, move in the electrolyte, and are absorbed in the Li-Al alloy at the counter electrode, so that charging and discharging can be stably repeated. Here, the active materials a1, a2
Alternatively, b is lithium-containing composite oxide Li _{1 + y} FeO _1.5 , Li _{2 + y} FeO ₂ or L
After the production of i _{1 + y} ZnO _1.5 , in the subsequent discharge-charge cycle, the lithium-containing composite oxides Li _{1 + y ′} FeO _1.5 and Li _{2 + y ′} except during the complete discharge. FeO ₂ or Li _{1 + y ′} ZnO _1.5 is formed.

(Embodiment 3) The working electrode 5 of this embodiment was manufactured as follows. Commercially available manganese monoxide MnO and lithium hydroxide LiOH.H ₂ O were weighed so as to have a molar ratio of Mn: Li = 1: 1, and thoroughly mixed using a mortar.
This mixture was heat-treated in a nitrogen stream at a temperature of 750 ° C. for 12 hours. After cooling, the mixture was pulverized to a particle size of 53 μm or less.
The product (LiMnO _1.5 ) thus obtained was used as an active material c according to the present invention, and the same graphite as that used in Example 1 was used as a conductive agent, and a cross-linked acrylic resin or the like was used as a binder. Were mixed at a weight ratio of 65:20:15 to obtain a working electrode mixture. Next, this working electrode mixture was used for 2 tons.
After being formed into a pellet having a diameter of 15 mm and a thickness of 0.3 mm at on / cm 2, the pellet was adhered to the working electrode case 7 by a working electrode current collector 6 made of a conductive adhesive containing carbon as a conductive filler. What was dried by heating under reduced pressure at 10 ° C. for 10 hours was used as a working electrode.

Further, for comparison, the same graphite as used for the conductive agent was used as the active material (active material r3) in place of the active material c according to the present invention, except that A similar electrode (comparative working electrode) was prepared in the same manner as the working electrode. Using the working electrode thus prepared, the volume ratio of propylene carbonate, ethylene carbonate and 1,2-dimethoxyethane was 1:
The same procedure as in Example 1 was carried out except that lithium perchlorate LiClO ₄ was dissolved at 1 mol / l in a 1: 2 mixed solvent, and the amount of lithium at the counter electrode was 1.6 times that of Example 1. Similar batteries C and R3 were produced.

The batteries C and R3 thus obtained were subjected to the same charge / discharge cycle test as in Example 1.
FIG. 8 shows the charge characteristics in the third cycle and FIG. 9 shows the discharge characteristics. As is clear from the figure, the battery C of the present embodiment is
It can be seen that has excellent charge / discharge characteristics similarly to the batteries A1 and A2 according to the present invention of Example 1.

The active materials a1, a2, b and c of the batteries A1, A2, B and C according to the present invention are 1.5 to 2.5 V with respect to the Li-Al alloy electrode (about 1.5 to 2.5 V with respect to lithium metal). 1.9 to 2.9 V).
Or more than that, since the charge / discharge capacity in a low potential region of −0.4 to +1.5 V (corresponding to about 0 to 1.9 V with respect to metallic lithium) is large, the non-aqueous electrolyte secondary battery It turns out that it is not only used as a positive electrode active material, but is particularly excellent as a negative electrode active material. In particular, the active material b of Example 2 and the active material c of Example 3 have a larger charge / discharge capacity in a lower potential region and a lower potential.
It is particularly excellent as a negative electrode active material.

In the examples, only the case of a lithium-aluminum alloy was shown as a counter electrode. However, the present invention is not limited to the examples, and as described above, metallic lithium, lithium and Zn, Sn, Pb, Alloys with other metals such as Bi, carbon and lithium insertion compounds such as MoO ₂ , WO ₂ , Fe ₂ O ₃ , and conductive polymers capable of doping lithium ions such as polyacetylene, polypyrrol, and polyacene; A negative electrode using a material capable of absorbing and releasing lithium as an active material, TiS
Metal chalcogenide such as ₂ , MoS ₂ , NbSe ₃ , Mn
O ₂ , MoO ₃ , V ₂ O ₅ , Li _x CoO ₂ , Li _x NiO ₂ ,
An active material capable of inserting and extracting lithium cations and / or anions, such as metal oxides such as Li _x Mn ₂ O ₄ , conductive polymers such as polyaniline, polypyrrole, polyparaphenylene, and polyacene, and graphite intercalation compounds. Needless to say, the positive electrode described above can be used as a counter electrode in combination with the electrode according to the present invention.

[0053]

As described in detail above, the present invention relates to a metal or a similar metal M capable of forming a divalent oxide as an active material of at least one of a negative electrode and a positive electrode of a nonaqueous electrolyte secondary battery. A composite oxide represented by a composition formula Li _2x MO _{1 + x} (where x> 0) obtained by heating each single substance of lithium Li or a mixture of these compounds, or the composite oxide and lithium or lithium compound Li is further absorbed in the composite oxide by an electrochemical reaction with or a lithium is released from the composite oxide by an electrochemical reaction, and a composition formula Li _{2x + y} MO _{1 + x} (provided that 2x + y
.Gtoreq.0) using a novel lithium-ion occluding and releasing substance composed of a composite oxide. The amount capable of reversibly occluding and releasing lithium ions by charging and discharging, that is, the charge-discharge capacity is extremely large, and the charge-discharge capacity is large. Because of its small polarization, charging and discharging with a large current is possible, and furthermore, deterioration such as decomposition and crystal collapse due to overcharging and overdischarging is hardly observed, and an extremely stable battery having a long cycle life can be obtained.
In particular, when the active material according to the present invention is used as a negative electrode active material, a high voltage and high energy density battery can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of the structure of a battery implemented in the present invention.

FIG. 2 is an explanatory diagram showing a comparison of charging characteristics at the third cycle between a battery according to the present invention and a conventional battery.

FIG. 3 is an explanatory diagram showing a comparison of the discharge characteristics at the third cycle between the battery according to the present invention and the conventional battery.

FIG. 4 is an explanatory diagram showing a comparison of cycle characteristics between a battery according to the present invention and a conventional battery.

FIG. 5 is an explanatory diagram showing a comparison of charging characteristics at the third cycle between a battery according to the present invention and a conventional battery.

FIG. 6 is an explanatory diagram showing a comparison of the discharge characteristics at the third cycle between the battery according to the present invention and the conventional battery.

FIG. 7 is an explanatory diagram showing a comparison of cycle characteristics between a battery according to the present invention and a conventional battery.

FIG. 8 is an explanatory diagram showing a comparison of charging characteristics at the third cycle between a battery according to the present invention and a conventional battery.

FIG. 9 is an explanatory diagram showing a comparison of the discharge characteristics at the third cycle between the battery according to the present invention and the conventional battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Counter electrode case 2 Counter electrode current collector 3 Counter electrode 4 Separator 5 Working electrode 6 Working electrode current collector 7 Working electrode case 8 Gasket

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akifumi Sakata 6-31-1, Kameido, Koto-ku, Tokyo Inside Seiko Electronics Industries Co., Ltd. (72) Inventor Fumiharu Iwasaki 6-31, Kameido, Koto-ku, Tokyo No. Seiko Electronics Co., Ltd. (72) Inventor Seiji Yahagi 6-31-1, Kameido, Koto-ku, Tokyo Seiko Electronics Co., Ltd. (56) References JP-A-60-216452 (JP, A) JP-A-64-24365 (JP, A) JP-A-56-30266 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/58 H01M 10/40

Claims (4)

(57) [Claims] In a non-aqueous electrolyte secondary battery comprising at least a negative electrode, a positive electrode, and a lithium ion conductive non-aqueous electrolyte, a divalent oxide can be generated as an active material of at least one of the negative electrode and the positive electrode. At least one metal M selected from Fe, Mn, and Zn, and each of Li and a mixture of lithium Li or a mixture of these compounds are placed in an atmosphere in which the amount of oxygen or oxygen partial pressure is controlled so that the valence of M is divalent. A nonaqueous electrolyte secondary battery using a composite oxide represented by a composition formula Li _2x MO _{1 + x} (where 0 <x ≦ 1) obtained by heating. 2. A non-aqueous electrolyte secondary battery comprising at least a negative electrode, a positive electrode, and a lithium ion conductive non-aqueous electrolyte, capable of producing a divalent oxide as an active material of at least one of the negative electrode and the positive electrode. At least one metal M selected from Fe, Mn, and Zn, and each of Li and a mixture of lithium Li or a mixture of these compounds are placed in an atmosphere in which the amount of oxygen or oxygen partial pressure is controlled so that the valence of M is divalent. A composite oxide represented by a composition formula Li _2x MO _{1 + x} (where 0 <x ≦ 1) obtained by heating, or the composite oxide formed by an electrochemical reaction between the composite oxide and lithium or a lithium-containing substance. The composition formula Li _{2x + y} MO _{1 + x} (where 0 <x ≦ 1 and −2 x) obtained by further absorbing lithium in the substance or releasing lithium from the composite oxide by an electrochemical reaction.
A nonaqueous electrolyte secondary battery using a composite oxide represented by < y ≦ 2). 3. A method for manufacturing a non-aqueous electrolyte secondary battery comprising at least a negative electrode, a positive electrode, and a lithium ion conductive non-aqueous electrolyte, comprising a method of producing a non-aqueous electrolyte secondary battery comprising at least one metal M selected from Fe, Mn, and Zn. A valence compound and a lithium compound having oxygen are mixed and heated in a non-oxidizing atmosphere to obtain a composite oxide represented by a composition formula Li _2x MO _{1 + x} (where 0 <x ≦ 1). Using this composite oxide as an active material of at least one electrode of the negative electrode and the positive electrode, in a battery after assembling the battery, or in or out of the battery during the battery manufacturing process, this composite oxide Li _2x MO ₁₊ or is contained electrochemical reaction depends on more lithium composite oxide compositional formula Li _2x MO 1 + _x with _x lithium or lithium-containing compound, or especially that to release lithium ions from the complex oxide Non-aqueous method for producing electrolyte secondary battery according to. 4. A method for producing a non-aqueous electrolyte secondary battery comprising at least a negative electrode, a positive electrode, and a lithium-ion conductive non-aqueous electrolyte, the method comprising: A valence compound and a lithium compound having oxygen are mixed and heated in a non-oxidizing atmosphere to obtain a composite oxide represented by a composition formula Li _2x MO _{1 + x} (where 0 <x ≦ 1). Using this composite oxide as an active material of at least one electrode of the negative electrode and the positive electrode, in a battery after assembling the battery, or in or out of the battery during the battery manufacturing process, this composite oxide Li _2x MO ₁₊ either by containing the composite oxide Li _2x MO further lithium 1 + _x depending on the electrochemical reaction between the _x and the lithium or lithium-containing substance or complex depending on the thereby releasing lithium ions from the complex oxide Monster _{Li 2x + y MO 1 + x} ( where 0
<X ≦ 1 and −2x <y ≦ 2). A method for producing a non-aqueous electrolyte secondary battery, comprising: