JP3079344B2 - 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 Nonaqueous electrolyte batteries using lithium as a negative electrode active material have advantages such as high voltage, high energy density, low self-discharge, and excellent long-term reliability. It is already widely used as a power source for applications. However, with the recent remarkable development of portable electronic devices and communication devices,
With the emergence of a wide variety of devices that require a large current output from batteries as power sources, there is a strong demand for rechargeable and high-density secondary batteries that can be recharged and discharged from the viewpoint of economy and reduction in size and weight of the devices. ing. For this reason, research and development to promote 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. are still insufficient. It is 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 and} other metal oxides, etc., only lithium ions (cations) intercalate, deintercalate, etc., between crystal layers or between lattice positions or lattice gaps. Type that goes in and out depending on
The second type is a type such as a conductive polymer such as polyaniline, polypyrrole, and polyparaphenylene, in which only anions mainly stably enter and leave by doping and undoping reactions. 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, when metallic lithium is used alone, the electrode potential is the lowest, so that a positive electrode using the above-described positive electrode active material is used. The output voltage of the combined battery is the highest, and the energy density is high, which is preferable.However, dendrites and passive compounds are generated on the negative electrode due to charge and discharge, and there is a problem that deterioration due to charge and discharge is large and cycle life is short. . In order to solve this problem, (1) lithium and Al, Zn, Sn, Pb, Bi, Cd
Alloys with other metals such as (2) WO ₂ , MoO ₂ , Fe ₂
Inorganic compounds such as O ₃ and TiS ₂ , graphite, intercalation compounds or insertion compounds in which lithium ions are occluded in the crystal structure of a carbonaceous material obtained by baking an organic material, (3) lithium-doped polyacene, It has been proposed to use a substance capable of inserting and extracting lithium ions, such as a conductive polymer such as polyacetylene.

[0005]

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 serve as negative electrode components, the capacity and energy density per volume and weight are significantly reduced.

Further, when an alloy of lithium and another metal of the above (1) is used, the utilization efficiency of lithium at the time of charge and discharge is low, and cracks occur in the electrodes due to repetition of charge and discharge, and cracks occur. Therefore, there is a problem that the cycle life is short due to the generation of the compound. In the case of the lithium intercalation compound or the intercalation compound of (2), deterioration such as collapse of the crystal structure or generation of an irreversible substance due to overcharging and discharging occurs. However, there is a drawback that the output voltage of a battery using this is low because there are many (noble) materials having high (noble). In the case of the conductive polymer of (3),
There is a problem that the charge / discharge capacity, particularly the charge / discharge capacity per volume is small.

For this reason, high voltage, high energy density,
In addition, in order to obtain a secondary battery having excellent charge / discharge characteristics and a long cycle life, the electrode potential with respect to lithium is low (low), and the collapse of the crystal structure due to insertion and extraction of lithium ions during charge / discharge, It is necessary to use a negative electrode active material which has no deterioration such as generation and has a large amount capable of reversibly inserting and extracting lithium ions, that is, a large effective charge and 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, deterioration due to crystal collapse or generation of irreversible material is large. . On the other hand, the second and third types have the disadvantage that the charge / discharge capacity, particularly the charge / discharge capacity per volume and the energy density are small.

For this reason, in order to obtain a secondary battery having excellent overcharge characteristics and overdischarge characteristics, and having 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.

[0011]

In order to solve the above-mentioned problems, the present invention uses a composition formula LixMO as an active material for at least one of a negative electrode and a positive electrode of this type of battery.
The present invention proposes to use a novel lithium ion occluding and releasing substance composed of a composite oxide of a metal M and lithium Li represented by the formula ( 0 ≦ x 2 ). That is, it is an oxide having a composition ratio of a metal M other than an alkali metal and oxygen O of about 1: 1. The oxide contains lithium in its crystal structure or amorphous structure and electrochemical reaction in a non-aqueous electrolyte. A composite oxide capable of occluding and releasing lithium ions is used. The metal M constituting the composite oxide is Mn, Ti, Z
A material that can generate n monoxide is used.

Although the composition ratio of such metal M to oxygen O is 1: 1 as described above, it is often the case that gold is used in the synthesis.
Defects or excesses of genus M or oxygen O result in non-stoichiometric compounds, the extent of which is deficient or excessive, depending on the type of M, but ranging up to ± 25%. In particular, when a transition metal is used as the metal M, it is easy to generate a compound having a high non-stoichiometric ratio due to the deficiency of the metal M or oxygen O. Therefore, lithium ions are contained in the crystal structure or the amorphous structure of the product. This is particularly advantageous because there are many sites that can be occluded, a material having high mobility of lithium ions and a high electron conductivity is obtained, and a material having a large charge / discharge capacity and a small polarization is easily obtained. Further, the content x of lithium may be within a range where the composite oxide is stably present, and a range of 0 ≦ x ≦ 2 is particularly preferable.

The preferred two methods for producing the composite oxide of metal M and lithium used as the active material of the negative electrode and / or the positive electrode of the battery of the present invention include the following two methods, but are not limited thereto. Not done.

The first method is to mix each of the above-mentioned metals and lithium alone or their oxygen-containing compounds at a predetermined molar ratio, and to mix them in a non-oxidizing atmosphere such as an inert atmosphere or a vacuum or a weak reduction. This is a method in which synthesis is performed by heating in an inert gas atmosphere or an atmosphere in which the amount of oxygen is controlled. As the respective compounds of the metal and lithium as starting materials,
Any compound may be used as long as it is heated in an inert atmosphere or in a vacuum such as an oxide, a hydroxide, or a salt such as a carbonate or a nitrate, or an organic compound to form an oxide. The heating temperature depends on the starting material and the heating atmosphere,
Synthesis can be performed at a temperature of 00 ° C. or higher, preferably 600 ° C. or higher, more preferably 700 ° C. or higher.

The composite oxide of the metal and lithium obtained in this manner is used as an active material for a negative electrode and / or a positive electrode after being subjected to processing such as pulverization and sizing or granulation as needed. In addition, as in the second method described below, a lithium ion can be further added to the composite oxide by an electrochemical reaction between the lithium-containing composite oxide and metallic lithium or a substance containing lithium. By increasing or decreasing lithium content by absorbing lithium ions or releasing lithium ions from the composite oxide, an active material may be used as the active material.

The second method is to use MnO, TiO and ZnO.
Lithium ions are occluded in the monoxide MO by an electrochemical reaction between the monoxide MO of the metal M and lithium or a substance containing lithium to obtain a composite oxide of the metal or the similar metal and lithium. Is the way.

As the lithium-containing substance for use in the electrochemical reaction, for example, 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 are inserted and released. Possible materials can be used.

Such occlusion of lithium ions by an electrochemical reaction to the metal monoxide MO is performed in the battery after the battery is assembled or in or outside the battery during the battery manufacturing process. Specifically, it can be performed as follows.

That is, (1) one electrode (working electrode) is formed by molding the metal monoxide or a mixture thereof with a conductive agent, a binder and the like as one electrode (working electrode); The other electrode (counter electrode) is in contact with a lithium ion conductive non-aqueous electrolyte as the other electrode (counter electrode) so that both electrodes are opposed to each other to form an electrochemical cell, and an appropriate current is applied in the direction in which the working electrode performs a cathode reaction. A method in which lithium ions are electrochemically occluded in the monoxide by energizing or discharging.
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) A laminated electrode formed by molding a monoxide of the metal or a mixture thereof with a conductive agent, a binder and the like into a predetermined shape, and pressing or contacting lithium or an alloy of lithium or the like with this. Is incorporated in a nonaqueous electrolyte secondary battery as a negative electrode or a positive 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 monoxide. (3) A non-aqueous electrolyte secondary battery in which the metal monoxide is used as an active material of one electrode and a material containing lithium and capable of inserting and extracting lithium ions in the other electrode is used as an active material. . A method in which lithium ions are occluded in the monoxide by charging or discharging during use as a battery.

[0020] Other than the alkali metal thus obtained,
A composite oxide Li _x MO of metal M and lithium is used as an active material of a negative electrode and / or a positive electrode.

The electrode using the composite oxide Li _x MO as the active material according to the present invention can be used as a positive or negative electrode active material to constitute a secondary battery. And any of the above-mentioned electrodes 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 electrode using the composite oxide Li _x MO according to the present invention as an active material has a large charge / discharge capacity in a base region where the electrode potential with respect to metal lithium is 1.9 V or less, and the deterioration due to overcharge and overdischarge is low. small order, used as a negative electrode, the above-described V ₂
O ₅ and _{Li x CoO 2, Li x NiO} 2, Li x Mn 2 electrode potential with respect to lithium metal, such as metal oxides O ₄ and the like 3V
Alternatively, by combining with a positive electrode using an active material having a high potential of 4 V or more, a secondary battery having high voltage, high energy density, excellent current / discharge characteristics, and little deterioration due to overcharge and overdischarge can be obtained. . Among them, M constituting the composite oxide Li _x MO is Mn, Ti, Zn.
In the case of , the electrode potential for metallic lithium is 1.5 V
The charge / discharge capacity of the following lower regions is particularly large, and the deterioration due to overcharge and overdischarge is small, so that it is particularly excellent as a negative electrode active material.

On the other hand, the composite oxide Li _x M according to the present invention
Along with the negative electrode using O as the negative electrode active material, the composition formula is Li _a T _b L
_c O ₂ , where T is a transition metal element, L is boron B
And silicon is at least one metal element selected from silicon Si, where a, b, and c are respectively 0 <a ≦ 1.15, 0.
85 ≦ b + c ≦ 1.3, 0 ≦ c, and the charge / discharge characteristics are particularly high at high energy density by using a composite oxide containing lithium and having a layered structure in combination with a positive electrode as a positive electrode active material. It is particularly preferable because a secondary battery which is excellent, has little deterioration due to overcharge and overdischarge, and has a long cycle life can be obtained.

[0023] The composite oxide used as a positive electrode active material of the present invention battery Li _a T _b L _c O ₂ can be synthesized as follows. That is, lithium Li, each of the transition metal T and the element L, or their respective oxides, hydroxides, or salts such as carbonates and nitrates are mixed at a predetermined ratio, and the mixture is heated to 600 ° C. or more in air or an atmosphere containing oxygen. It is obtained by heating and calcining at a temperature, preferably 700 to 900 ° C. When an oxide or a compound containing oxygen is used as a supply source of Li, T, L, or the like, heat synthesis can be performed in an inert atmosphere. The heating time of 4 to 50 hours is usually sufficient, but it is effective to repeat the firing, cooling, and pulverizing and mixing processes several times in order to promote the synthesis reaction and improve the uniformity.

In the composition formula Li _{a Tb} L _c O ₂ , the Li amount a is a stoichiometric composition a = 1 as a standard in the above-mentioned heating synthesis, but a non-stoichiometric composition of about ± 15% is also available. 0 <a ≦ 1.15 is possible by electrochemical intercalation and deintercalation. Transition metal T
Are preferably Co, Ni, Fe, Mn, Cr, V, etc., and Co and Ni are particularly preferred because of their excellent charge / discharge characteristics. As the amount c of boron and / or silicon and the amount b of the transition metal T, when 0 <c and 0.85 ≦ b + c ≦ 1.3, the polarization (internal resistance) during charging and discharging is reduced, and the cycle characteristics are improved. The effect is remarkable and preferable. On the other hand, the charge / discharge capacity in each cycle is conversely decreased when the amount c of boron and / or silicon is too large, and becomes maximum when 0 <c ≦ 0.5. Therefore, this range is particularly preferable.

As the electrolyte, γ-butyrolactone, propylene carbonate, ethylene carbonate,
LiClO ₄ , LiPF ₆ , LiBF as a supporting electrolyte in an organic solvent such as butylene carbonate, dimethyl carbonate, diethyl carbonate, methylformate, 1,2-dimethoxyethane, tetrahydrofuran, dioxolan, dimethylformamide, alone or in a mixed solvent
₄ , an organic electrolyte solution in which a lithium ion dissociable salt such as 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, Any non-aqueous electrolyte having lithium ion conductivity such as an inorganic solid electrolyte such as LiI may be used. In particular, when a non-aqueous electrolyte (organic electrolyte) containing ethylene carbonate as an organic solvent is used,
It is particularly preferable because a secondary battery having excellent charge / discharge characteristics and a long cycle life can be obtained.

[0026]

The electrode using the composite oxide Li _x MO of a metal M other than an alkali metal and lithium according to the present invention as an active material has a potential of at least 0 to 3 V with respect to metallic lithium in a non-aqueous electrolyte.
It is possible to stably and repeatedly absorb and release lithium ions within the range of the electrode potential described above, and it 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 addition, 0 to the lithium reference electrode
In a 1.9 V base potential region, a high-capacity region in which lithium ions can be stably inserted and released and repeatedly charged and discharged has a higher capacity, and thus has superior performance when used as a negative electrode. In particular, when M is a metal of Mn, Ti, and Zn, the charge / discharge capacity in a lower region where the electrode potential with respect to metallic lithium is 1.5 V or less is particularly large, and deterioration due to overcharge and overdischarge is small, Particularly, it is excellent as a negative electrode active material.
Further, as compared with carbonaceous materials such as graphite which have been conventionally used as electrodes of this type of battery, the amount of lithium ions that can be inserted and released reversibly, that is, the charge / discharge capacity is extremely large, and the charge / discharge polarization is small. The battery can be charged / discharged with a current, and furthermore, almost no degradation such as decomposition or crystal collapse due to overcharge / overdischarge is observed, and 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 _x MO of lithium and a metal M other than an alkali metal, which is a novel active material according to the present invention, has a high mobility of lithium ions in this structure and a site capable of occluding lithium ions. It is presumed that the absorption and release of lithium ions is easy due to the large number of

On the other hand, the composite oxide Li _a T _b L _c O ₂ used as the positive electrode active material, the electrode potential with respect to metallic lithium has about 4V or more high potential, and at least 0 <a ≦ 1. Reversible charge / discharge by intercalation and deintercalation of Li ions is possible between 15 and 15, deterioration due to overcharge and overdischarge is small, and excellent cycle characteristics are obtained. Especially B and / or S
When the content c of i is 0.05 ≦ c <0.5, the polarization is small and the cycle characteristics are excellent. The reason why such excellent charge / discharge characteristics are obtained is not necessarily clear, but is presumed as follows. That is, the positive electrode active material according to the present invention Li _a T _b L _c O ₂ does not contain B and Si alpha-N
part of the oxide Li _a T _b O ₂ transition metal element T of Acro ₂ type layered structure is substituted with B or Si alpha-NACR
It has a skeletal structure similar to the O ₂ type. However, B atoms and Si atoms can also exist in interstitial spaces of crystals and Li sites (substituted with Li). In any case, since the crystal structure and the electronic structure change due to the presence of B or Si, Li
It is presumed that this is because ion conductivity is increased and lithium ions are easily absorbed and released.

For this reason, a battery using the combination of the negative electrode active material and the positive electrode active material according to the present invention is 4 to 2 times.
It has a high operating voltage of V and has an extremely large amount of reversible insertion and extraction of lithium ions, that is, a remarkably large charge / discharge capacity, and a small charge / discharge polarization. Deterioration of the active material due to overdischarge, deterioration of crystal collapse, and the like are hardly observed, and it is extremely stable and has a long cycle life.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0031]

FIG . 1 is a sectional view of a coin-type battery showing an example of a test cell used for evaluating the performance of an electrode active material of a nonaqueous electrolyte secondary battery according to the present invention. In the figure, reference numeral 1 denotes a counter electrode case also serving as a counter electrode terminal, which is formed by drawing a stainless steel plate having one outer surface 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. Reference numeral 7 denotes 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 to be described later or a comparative active material according to a conventional method. Reference numeral 6 denotes a conductive adhesive using a stainless steel net or carbon as a conductive filler. The working electrode current collector electrically connects the working electrode 5 and the working electrode case 7. 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.

Comparative Example 1 This is a case where Li _x MnO is used as an active material . below
A battery was fabricated using the working electrode and the electrolyte.

The working electrode 5 was manufactured as follows. A commercially available manganese monoxide MnO was pulverized and sized using an automatic mortar to a particle size of 53 μm or less as an active material c according to the present invention, and the same graphite as that used in Example 1 as a conductive agent was bound thereto. A working electrode mixture was prepared by mixing a crosslinkable acrylic resin or the like in a weight ratio of 65:20:15 as an agent.
Next, this working electrode mixture was applied at ² ton / cm ² with a diameter of 15 m.
The working electrode 5 was produced by pressure molding into a 0.3 mm thick pellet. Thereafter, the working electrode 5 thus obtained is bonded and integrated with a working electrode case 7 using a working electrode current collector 6 made of a conductive resin adhesive containing carbon as a conductive filler. And dried under reduced pressure for 10 hours to produce the above-described coin-type battery.

For comparison, the same graphite as that used for the conductive agent was used as the active material (abbreviated as active material r2) in place of the active material c according to the present invention.
A similar electrode (comparative working electrode) was prepared in the same manner as the working electrode of the present invention described above.

The electrolyte was lithium perchlorate LiClO _{4 in a} mixed solvent of propylene carbonate, ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1: 2.
Was dissolved at 1 mol / l.

The battery manufactured in this manner has a capacity of 1 at room temperature.
After aged for a week, a charge / discharge test described later was performed. Due to this aging, the lithium-aluminum laminated electrode of the counter electrode is sufficiently alloyed by touching the non-aqueous electrolyte in the battery, and substantially all of the lithium foil becomes a Li-Al alloy. About 0.4V compared to the case where metallic lithium is used alone
The value decreased and became stable.

The batteries manufactured in this manner are hereinafter abbreviated as batteries C and R2, corresponding to the active materials c and r2 of the working electrodes used.

The final voltage of the batteries C and R2 at a constant current of 1 mA (current direction in which a battery reaction in which lithium ions are occluded from the electrolytic solution to the working electrode) is -0.4.
FIG. 2 shows the discharge characteristics in the third cycle when a charge / discharge cycle was performed under the condition of a final voltage of 2.5 V, and a discharge (current direction in which a lithium ion is released from the working electrode into the electrolytic solution in a battery reaction) . FIG. 3 shows the charging characteristics. FIG. 4 shows the cycle characteristics. The charge / discharge cycle started from charging. As is clear from FIGS. 2 to 4, the battery C according to the present invention has a remarkably large charge / discharge capacity and a reversible charge / discharge region significantly expanded as compared with the comparative battery R2. 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.

(Comparative Example 2) Instead of the active material c of Comparative Example 1, commercially available titanium monoxide T
A material obtained by pulverizing and sizing iO to a particle size of 53 μm or less was used as an active material of the working electrode (active material d according to the present invention). Except for the active material of the working electrode, a battery D similar to all the batteries C of Comparative Example 1 was produced.

The battery D thus obtained and the above-mentioned comparative battery R2 were similarly charged in the same manner as in Comparative Example 1 at a constant current of 1 mA and a cutoff voltage of -0.4 V and a cutoff voltage of 2.5.
A charge / discharge cycle test was performed under the condition of V. FIG. 5 shows the discharge characteristics in the third cycle, FIG. 6 shows the charge characteristics, and FIG . 7 shows the cycle characteristics.

As can be seen from the figure, the battery D is in accordance with the present invention.
It shows that the battery C has excellent charge / discharge characteristics in the same manner as the battery C.

Comparative Example 3 A commercially available zinc monoxide ZnO pulverized and sized to a particle size of 53 μm or less was used as the active material of the working electrode (active material e according to the present invention). All comparative examples except for the active material of this working electrode
Battery E similar to Battery C of Comparative Example 1 was produced. Similarly to Comparative Example 1, the battery E thus obtained and the above-mentioned comparative battery R2 were charged and discharged under the conditions of a constant current of 1 mA, an end voltage of charging of -0.4 V, and an end voltage of discharge of 2.5 V. A cycle test was performed. The discharge characteristics in the first cycle at this time are shown in FIG. 8 , and the charge characteristics are shown in FIG .

As is apparent from the figure, the battery E was obtained in Comparative Examples 1 to
It can be seen that the battery according to No. 2 has excellent charge / discharge characteristics similarly to the battery according to the present invention . That is, the battery E according to the present invention is a comparative battery R
It can be seen that the charge / discharge capacity is remarkably large and the reversible region of charge / discharge is remarkably expanded as compared with No. 2. In addition, the difference between the operating voltages of charging and discharging is extremely small 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.

As described above , the active material of the working electrode of the battery according to the present invention is a composite oxide L containing lithium upon the first charge.
i _x MO (M is Mn, Ti, Zn) to generate. That is,
Lithium ions are released into the electrolyte from the Li-Al alloy of the counter electrode due to the charge, and the lithium ions move in the electrolyte and undergo an electrode reaction with the active material MO of the working electrode, and the active material M
Lithium ions are electrochemically occluded in O, and a lithium-containing composite oxide Li _x MO is generated. Next, at the time of discharge, 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, whereby stable charge and discharge can be performed repeatedly. Here, after the active material (MO) generates the composite oxide Li _x MO containing lithium by the first charge,
Subsequent discharge - Te is at the charging cycle, except during full discharge forms a composite oxide Li _x MO containing lithium.

The active material of the battery according to the present invention is Li-A
As with or above the noble potential region of 1.5 to 2.5 V (corresponding to about 1.9 to 2.9 V for lithium metal) with respect to the alloy electrode, -0.4 to +1 .5V
Since the charge / discharge capacity in a low potential region (corresponding to about 0 to 1.9 V with respect to metallic lithium) is large, it is used not only as a positive electrode active material of a nonaqueous electrolyte secondary battery,
It turns out that it is particularly excellent as a negative electrode active material. Active material L
i _x MO (M is Mn, Ti, Zn) baser potential region of -0.4 to + 1.1V with respect to Li-Al alloy electrode (corresponding to about 0~1.5V the metal lithium) Has a larger charge and discharge capacity, and has a lower potential,
It is particularly excellent as a negative electrode active material.

Example 1 FIG. 10 is a sectional view of a coin-type battery showing an example of a non-aqueous electrolyte secondary battery according to the present invention. In the figure, reference numeral 11 denotes a negative electrode case also serving as a negative electrode terminal, which is formed by drawing a stainless steel plate having one outer surface Ni-plated.
Reference numeral 13 denotes a negative electrode formed by using a negative electrode active material according to the present invention described later, and is bonded to the negative electrode case 11 by a negative electrode current collector 12 made of a conductive adhesive using carbon as a conductive filler. Reference numeral 17 denotes a positive electrode case made of stainless steel with one outer surface Ni-plated, and also serves as a positive electrode terminal.
Reference numeral 15 denotes a positive electrode constituted by using a positive electrode active material according to the present invention described later, and is bonded to a positive electrode case 17 by a positive electrode current collector 16 made of a conductive adhesive using carbon as a conductive filler. Reference numeral 14 denotes a separator made of a porous film of polypropylene, which is impregnated with an electrolytic solution. 1
Reference numeral 8 denotes a gasket mainly composed of polypropylene, which is interposed between the negative electrode case 11 and the positive electrode case 17 to maintain the electrical insulation between the negative electrode and the positive electrode, and at the same time, the opening edge of the positive electrode case is bent inward and caulked. Depending on
The battery contents are sealed and sealed. The electrolyte used was a solution in which lithium perchlorate LiClO ₄ was dissolved at a ratio of 1 mol / l in a mixed solvent of propylene carbonate, ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1: 2.
The size of the battery was 20 mm in outer diameter and 1.6 mm in thickness.

The negative electrode 13 was manufactured as follows. A commercially available manganese monoxide, MnO, having a purity of 99.9% was crushed and sized using an automatic mortar to a particle size of 53 μm or less as a negative electrode active material according to the present invention.
Crosslinkable acrylic resin or the like is used as a binder in a weight ratio of 65: 2.
The mixture was mixed at a ratio of 0:15 to form a negative electrode mixture. Then, the negative electrode mixture was mixed at ² ton / cm ² with a diameter of 15 mm and a thickness of 0.23.
After pressure-molding into a pellet having a diameter of 200 mm, the material was dried under reduced pressure at 200 ° C. for 10 hours to obtain a negative electrode.

The positive electrode 15 was manufactured as follows. Lithium hydroxide LiOH.H ₂ O and cobalt carbonate CoCO ₃ are weighed so that the molar ratio of Li: Co becomes 1: 1 and sufficiently mixed using a mortar, and the mixture is heated to 850 ° C. in the atmosphere. For 12 hours, cooled and then crushed and sized to a particle size of 53 μm or less. This firing and pulverizing and sizing were repeated twice to synthesize the positive electrode active material LiCoO _{2 according} to the present invention.

This product was used as a positive electrode active material, and graphite was mixed as a conductive agent with fluorine resin or the like as a binder in a weight ratio of 80: 15: 5 to form a positive electrode mixture.
Next, this positive electrode mixture was applied at ² ton / cm ² and a diameter of 16.2 m.
m after being pressed into 0.67 mm thick pellets
What was dried by heating under reduced pressure at 0 ° C. for 10 hours was used as a positive electrode.

The battery (battery G) manufactured in this manner was aged at room temperature for one week, and then subjected to a charge / discharge test described later.

Charging / discharging characteristics of the first and second cycles when this battery G was subjected to a charging / discharging cycle at a constant current of 1 mA and a charging end voltage of 4.4 V and a discharging end voltage of 2.0 V. 11 is shown in FIG. 11 , and the cycle characteristics are shown in FIG . The charge / discharge cycle started from charging.

The battery G has a positive electrode active material L
Lithium ions are released from the iCoO ₂ into the electrolyte,
The lithium ions move in the electrolytic solution and undergo an electrode reaction with the negative electrode active material, whereby lithium ions are electrochemically occluded in the negative electrode active material to generate lithium-manganese composite oxide Li _x MnO containing lithium. Next, at the time of discharging, lithium ions are released from the lithium manganese composite oxide of the negative electrode into the electrolytic solution, move in the electrolytic solution and are occluded by the positive electrode active material, and thus can be repeatedly charged and discharged stably. Here, after the negative electrode active material generates the lithium-containing composite oxide Li _x MnO by the first charge, in the subsequent discharge-charge cycle, the negative electrode active material contains lithium except at the time of complete discharge. A composite oxide Li _x MnO is formed.

As is clear from FIGS. 11 to 12 , the battery G according to the present invention has a remarkably large charge / discharge capacity. Further, the decrease in the discharge capacity (charge / discharge efficiency) relative to the charge capacity is extremely small except in the first cycle, and the decrease in the discharge capacity (cycle deterioration) due to repeated charge / discharge is also small. Furthermore, it can be seen that the difference in operating voltage between charging and discharging is extremely small over the entire charging and discharging region, the polarization (internal resistance) of the battery is extremely small, and large-current charging and discharging is easy.

The cause of the large decrease in the first cycle discharge capacity (initial loss) with respect to the first cycle charge capacity is that lithium ions are electrochemically occluded in the negative electrode active material during the first cycle charge. Is mainly caused by a side reaction that occurs between Li and graphite or a binder added as a conductive agent to the negative electrode mixture, and the negative electrode active material M
Li that is occluded by nO and remains without being released during discharge
It is considered that there is also

[0055] Example 2 In this example, except for using negative electrode 23 and positive electrode 25 manufactured in the manner described below instead of the negative electrode 13 and positive electrode 15 of Example 1, the same procedure as in Example 1 To produce a similar battery H.

The negative electrode 23 was manufactured as follows. Example
Using the same negative electrode active material and negative electrode mixture as in 1 , 2ton / c
A negative electrode pellet was obtained by pressure molding into a pellet having a diameter of 15 mm and a thickness of 0.33 mm in m ² . The negative electrode pellet is adhered to the negative electrode case 11 by a negative electrode current collector 12 made of a conductive adhesive containing carbon as a conductive filler, and dried by heating under reduced pressure at 200 ° C. for 10 hours. Was punched out to a diameter of 14 mm and pressed. The thus obtained lithium-negative electrode pellet laminated electrode was used as a negative electrode.

The positive electrode 25 was manufactured as follows. Lithium hydroxide LiOH.H ₂ O, cobalt carbonate CoCO _3, and boron oxide B ₂ O ₃ were prepared at a molar ratio of Li: Co: B of 1: 0.
The mixture was weighed so as to be 9: 0.1, sufficiently mixed using a mortar, and heated and fired in the air at a temperature of 850 ° C. for 12 hours. After cooling, the mixture was pulverized and sized to a particle size of 53 μm or less.
This firing and pulverization and sizing were repeated twice to synthesize the positive electrode active material LiCo _0.9 B _0.1 O _{2 according} to the present invention.

This product was used as a positive electrode active material, and graphite was mixed as a conductive agent with fluororesin as a binder in a weight ratio of 80: 15: 5 to form a positive electrode mixture.
Next, this positive electrode mixture was applied at ² ton / cm ² and a diameter of 16.2 m.
m after being pressed into a 0.47 mm thick pellet.
What was dried by heating under reduced pressure at 0 ° C. for 10 hours was used as a positive electrode.

The battery manufactured in this manner (hereinafter abbreviated as Battery H) was aged at room temperature for one week,
The following charge / discharge test was performed. Due to this aging, the lithium-negative electrode laminated electrode of the negative electrode 23 spontaneously electrochemically reacts by touching the non-aqueous electrolyte in the battery, and substantially all of the lithium foil is electrochemically occluded in the negative electrode mixture. Was.

The battery H thus obtained is also
3. End voltage of charging at a constant current of 1 mA as in Example 1 .
A charge / discharge cycle test was performed under the conditions of 4 V and a discharge end voltage of 2.0 V. The charge and discharge characteristics of the first and second cycles at this time are shown in FIG. 13 , and the cycle characteristics are shown in FIG .

As is clear from the figure, the battery H of this embodiment is
It can be seen that the battery G has significantly better charge / discharge characteristics than the battery G of Example 1 . In particular, there is almost no decrease (initial loss) in the discharge capacity in the first cycle with respect to the charge capacity in the first cycle, and it can be seen that it is significantly improved as compared with the battery G of Example 1 . This is because a side reaction between lithium ions generated during charge and discharge and a conductive agent or a binder, or Mn during charging.
Lithium in an amount equivalent to the amount of lithium occluded in O and remaining without being released at the time of discharge, etc., is previously laminated on the negative electrode mixture to assemble the battery, and after the battery is assembled, the laminated electrode contacts the electrolyte in the battery. This is because the lithium reacts spontaneously with the negative electrode mixture to be occluded, so that no lithium loss occurs in the negative electrode during subsequent charge and discharge.

It is also found that the use of a boron-containing composite oxide as the positive electrode active material increases the charge / discharge capacity and significantly reduces cycle deterioration.

Example 3 In this example, the following positive electrode active material was used in place of the positive electrode active material of Example 2 . All except positive electrode active material
A similar battery was manufactured in the same manner as in Example 2 .

The positive electrode active material of this example was produced as follows. Lithium hydroxide LiOH.H ₂ O, cobalt carbonate CoCO _3, and silicon dioxide SiO ₂ are weighed so that the molar ratio of Li: Co: Si is 1: 0.9: 0.1, and sufficiently mixed using a mortar. After that, the mixture was heated and fired at 850 ° C. for 12 hours in the atmosphere, cooled, and crushed and sized to a particle size of 53 μm or less. This firing and pulverizing and sizing were repeated twice to obtain a layered composite oxide having an approximate composition of LiCo _0.9 Si _0.1 O ₂ . This was used as a positive electrode active material according to the present invention.

The battery (abbreviated as battery I) thus obtained was subjected to the same charge / discharge cycle test as in Example 2. As a result, it was found that the same excellent charge / discharge characteristics and cycle characteristics as battery H were obtained. Indicated.

Example 4 Instead of the electrolytic solution of Example 2 , ethylene carbonate was used.
LiP in a 1: 1 mixed solvent of diethyl carbonate by volume
The F ₆ was prepared by dissolving 1 mol / l. A similar battery J was prepared in the same manner as in Example 2 except for the electrolytic solution.

This battery J was also subjected to the same charge / discharge cycle test as in Example 2 .
Although the charge / discharge capacity at the fourth cycle showed a value smaller by 20 to 3%, a decrease in the discharge capacity (cycle deterioration) due to the repetition of the subsequent charge / discharge cycle was small, and more excellent cycle characteristics were exhibited.

[0068] In the embodiments, lithium as a counter electrode - aluminum alloy, LiCoO ₂ and Li _a T _b L _c O ₂
Although only the case of was shown, the present invention is not limited to the examples,
As described above, metallic lithium, lithium and Zn, Sn, P
alloys with other metals such as b, Bi, carbon, MoO ₂ , WO
_2, Fe ₂ O ₃ such as a lithium insertion compound, and a negative electrode of polyacetylene, polypyrrole, and capable of absorbing and desorbing lithium material like a lithium ion capable doping conductive polymers such as polyacene and the active material, TiS _2, MoS ₂ , N
metal chalcogenides such as bSe ₃ , MnO ₂ , MoO
₃ , V ₂ O ₅ , Li _x CoO ₂ , Li _x NiO ₂ , Li _x M
metal oxides such as n ₂ O ₄ , polyaniline, polypyrrole,
A positive electrode having a material capable of storing and releasing lithium cations and / or anions, such as a conductive polymer such as polyparaphenylene and polyacene, and a graphite intercalation compound, is used as a counter electrode in combination with the electrode according to the present invention. It goes without saying that you can do this.

[0069]

As described above in detail, the present invention provides a composite oxide Li _x MO of metal M and lithium as an active material of at least one of a negative electrode and a positive electrode of a nonaqueous electrolyte secondary battery.
It uses a new active material consisting of: The amount of lithium ions that can be inserted and released reversibly by charge and discharge, that is, the charge and discharge capacity is extremely large, and the charge and discharge polarization is small. It is possible to obtain a battery which is extremely stable and has a long cycle life, with almost no degradation such as decomposition or crystal collapse due to overcharge and overdischarge.
Particularly, the active material according to the present invention is used as a negative electrode active material, and V ₂ O ₅ , MnO ₂ , Li _x CoO ₂ , Li _x NiO ₂
And metal oxides such as Li _x Mn ₂ O ₄ , particularly Li _{a Tb} L _c O
_The electrode potential for metallic lithium such as ₂ is 3 V to 4
By combining with a positive electrode using a (noble) active material having a high potential of V or higher, a secondary battery having higher voltage, higher energy density, superior charge / discharge characteristics and a long cycle life can be obtained, and the like. Has the effect.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of the structure of a battery used for comparative evaluation of an electrode active material in the present invention.

FIG. 2 shows three types of active materials of a battery according to the present invention and a conventional battery.
FIG. 4 is an explanatory diagram showing a comparison of discharge characteristics of a cycle.

FIG. 3 shows three types of active materials of a battery according to the present invention and a conventional battery.
FIG. 9 is an explanatory diagram showing a comparison of charging characteristics of a cycle.

FIG. 4 shows the size of the active material of the battery according to the present invention and the conventional battery.
FIG. 4 is an explanatory diagram showing a comparison of the wheel characteristics.

FIG. 5 shows three active materials of the battery according to the present invention and the conventional battery.
FIG. 4 is an explanatory diagram showing a comparison of discharge characteristics of a cycle.

FIG. 6 shows three types of active materials of the battery according to the present invention and the conventional battery.
FIG. 9 is an explanatory diagram showing a comparison of charging characteristics of a cycle.

FIG. 7 shows the size of the active material of the battery according to the present invention and the conventional battery.
FIG. 4 is an explanatory diagram showing a comparison of the wheel characteristics.

FIG. 8 shows one of active materials of the battery according to the present invention and the conventional battery.
FIG. 4 is an explanatory diagram showing a comparison of discharge characteristics of a cycle.

FIG. 9 shows one of active materials of a battery according to the present invention and a conventional battery.
FIG. 9 is an explanatory diagram showing a comparison of charging characteristics of a cycle.

FIG. 10 shows an example of the structure of a battery implemented in the present invention.
FIG.

FIG. 11 shows the first cycle and the second cycle of the battery according to the present invention.
FIG. 4 is an explanatory diagram showing the charge / discharge characteristics of a cell.

FIG. 12 shows the cycle characteristics of the battery according to the present invention.
FIG.

FIG. 13 shows the first cycle and the second cycle of the battery according to the present invention.
FIG. 4 is an explanatory diagram showing the charge / discharge characteristics of a cell.

FIG. 14 shows the cycle characteristics of the battery according to the present invention.
FIG.

[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 11 Negative case 12 Negative current collector 13 Negative electrode 14 Separator 15 Positive electrode 16 Positive electrode collector 17 Positive case 18 gasket

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideki Ishikawa 5-30-1, Nishitaga, Taihaku-ku, Sendai, Miyagi Prefecture Inside Seiko Electronic Components Co., Ltd. No. 30 No. 1 Seiko Electronic Components Co., Ltd. (72) Inventor Akifumi Sakata 6-1, Kameido, Koto-ku, Tokyo 31-1 Inside Seiko Electronics Industries Co., Ltd. (72) Fumiharu Iwasaki 6, Kameido, Koto-ku, Tokyo 31-1 Inside Seiko Electronic Industries Co., Ltd. (72) Inventor Seiji Yahagi 6-31-1, Kameido, Koto-ku, Tokyo Seiko Electronic Industries Co., Ltd. (56) References JP-A-60-225360 (JP, A) JP-A-3-291862 (JP, A) JP-A-5-54889 (JP, A) JP-A-6-275268 (JP, A) JP-A-6-275266 (JP, A)

Claims (6)

(57) [Claims] 1. A non-aqueous electrolyte secondary battery comprising at least a negative electrode, a positive electrode, and a lithium ion conductive non-aqueous electrolyte, wherein the negative electrode active material has a general formula Li _x MO (where 0 ≦ x).
A non-aqueous electrolyte secondary battery in which M is Mn. 2. The method according to claim 1, wherein the negative electrode active material has a general formula Li _x MO (wherein
And an oxide represented by 0 ≦ x ≦ 2), wherein M is Mn
The non-aqueous electrolyte secondary battery according to claim 1. 3. A negative electrode, a positive electrode and a lithium ion conductive non-conductive material.
A non-aqueous electrolyte secondary battery comprising at least a water electrolyte.
And the negative electrode active material has a general formula Li _x MO (where 0 ≦ x).
Is a non-aqueous electrolyte, wherein M is Ti.
Next battery. 4. The method according to claim 1, wherein the negative electrode active material has a general formula Li _x MO (however
And 0 ≦ x ≦ 2), wherein M is Ti
The non-aqueous electrolyte secondary battery according to claim 3. 5. A negative electrode, a positive electrode and a lithium ion conductive non-conductive material.
A non-aqueous electrolyte secondary battery comprising at least a water electrolyte.
And the negative electrode active material has the general formula Li _x MO (0 ≦ x)
And M is Zn.
Next battery. 6. The negative electrode active material has a general formula Li _x MO (however
And 0 ≦ x ≦ 2), wherein M is Zn
The non-aqueous electrolyte secondary battery according to claim 5.