JP3447187B2 - Non-aqueous electrolyte battery and method for 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 that uses a lithium ion conductive non-aqueous electrolyte as a positive and negative electrode active material that can store and release lithium ions, and more particularly, The present invention relates to a novel secondary battery with a voltage of around 1.5 V, high energy density, excellent charge / discharge characteristics, a long cycle life, and high reliability.

[0002]

2. Description of the Related Art In recent years, with the remarkable development of portable electronic devices, communication devices, etc., a wide variety of devices requiring a large current output from a battery as a power source have appeared, which is economical and reduces the size and weight of the device. From the viewpoint of the above, there is a strong demand for secondary batteries with high energy density. In addition, with the decrease in the voltage of equipment, 1.
A non-aqueous electrolyte secondary battery having a high energy density of about 5 V has also been researched and developed, and partially put into practical use. Conventional 1.
A nickel-cadmium battery or a nickel-hydrogen battery is used as a secondary battery of about 5 V, but its capacity is small and it is difficult to miniaturize it. Recently, 1.5V batteries using titanium oxide are also available.

Batteries using titanium oxide and lithium-containing titanium oxide have been studied in JP-A-57-152669 and JP-B-63-8588. Tokusho Sho 6
In the Japanese Laid-Open Patent Publication No. 3-1708, a negative electrode using titanium oxide,
There is an example of combining with a positive electrode using manganese dioxide,
It seems that it has not been put to practical use due to problems such as the voltage being too low as 1 V and the charge / discharge cycle life being short. Further, JP-A-6-275263 and JP-A-7-320.
No. 784 discloses a battery using an improved lithium-containing titanium oxide for the negative electrode.

[0004]

The conventional nickel-cadmium battery or nickel-hydrogen battery has a small capacity and is difficult to be miniaturized. In addition, a 1.5 V battery using a lithium-containing titanium oxide for the negative electrode has an active material capacity of 100 m.
Since it was around Ah / g, the capacity could not be further increased.

As the negative electrode active material, when metal lithium is used alone, the electrode potential is the lowest, and therefore the output voltage as a battery combined with the positive electrode is the highest and the energy density is high, which is preferable. However, there has been a problem that dendrites and passivation compounds are generated on the lithium negative electrode with charge and discharge, the deterioration due to charge and discharge is large, and the cycle life is short. In order to solve this problem, as a negative electrode active material, (1) lithium and Al, Zn, Sn, Pb, Bi, Cd
Alloys with other metals such as (2) WO ₂ , MoO ₂ , Fe
_In the crystal structure or amorphous structure of inorganic compounds such as ₂ O ₃ , TiS ₂ , Li _x Co _1-y Ni _y O ₂ , and Li _x WO _y, carbonaceous materials obtained by firing graphite, and organic substances It has been proposed to use a substance capable of occluding and releasing lithium ions such as an intercalation compound or insertion compound occluding lithium ions, and (3) a conductive polymer such as polyacene or polyacetylene doped with lithium ions.

However, in general, when a battery is constituted by using a material capable of inserting and extracting lithium ions other than the above-mentioned metallic lithium as the negative electrode active material, the electrode potential of these negative electrode active materials is metallic lithium. Since the electrode potential is higher than the electrode potential of No. 1, there is a drawback that the operating voltage of the battery is considerably lower than that when metal lithium is used alone. For example,
0.2 to 0.8 V when using an alloy of lithium and Al, Zn, Pb, Sn, Bi, Cd, etc., 0 to 1 V for a carbon-lithium intercalation compound, a lithium ion insertion compound such as MoO ₂ or WO ₂ . Then, the operating voltage decreases by 0.5 to 1.5V.

Further, since elements other than lithium also serve as negative electrode constituents, the capacity and energy density per volume and weight are significantly reduced. Furthermore, when the alloy of (1) above with lithium and another metal is used, the utilization efficiency of lithium during charging and discharging is low, and cracks occur in the electrode due to repeated charging and discharging, and the like. Therefore, there is a problem that the cycle life is short. In the case of the lithium intercalation compound or the intercalation compound of (2), there are many deteriorations such as the collapse of the crystal structure and the formation of irreversible substances due to overcharging and discharging, and the electrode potential is high (noble). There is a drawback that the output voltage of the battery used is low. In the case of the conductive polymer (3), there is a problem that the charge / discharge capacity, especially the charge / discharge capacity per volume is small.

Therefore, at high voltage and high energy density,
In addition, in order to obtain a secondary battery with excellent charge / discharge characteristics and a long cycle life, the electrode potential with respect to lithium is low (base), and the collapse of the crystal structure or the irreversible substance due to the absorption / desorption of lithium ions during charge / discharge. There is a need for a negative electrode active material that has a large amount of lithium ions that can be occluded and released reversibly without deterioration such as generation, that is, a large effective charge / discharge capacity.

First, the present inventors have found that the composition formula Li _x SiO _y
(However, the lithium-containing silicon oxide represented by 0 ≦ x, 0 <y <2) is contained in the non-aqueous electrolyte in an electrode potential range of at least 0 to 3 V with respect to the lithium reference electrode (metallic lithium). It is capable of electrochemically stably occluding and releasing lithium ions repeatedly, and by such a charge-discharge reaction, it has a remarkably high charge-discharge capacity particularly in a base potential region of 0 to 1 V, and has an excellent negative electrode activity. He found that it could be a substance and applied for a patent (Japanese Patent Application Nos. 4-265179 and 5-3).
581 and 5-162958).

[0010]

In the present invention, it has been found that the capacity can be remarkably increased by using iron sulfide as a battery active material. In particular, a lithium-containing silicon oxide represented by the composition formula Li _x SiO _y (where 0 ≦ x, 0 <y <2), which the present inventors previously applied, was used as a negative electrode, and an iron sulfide was used. The increase in capacity due to use as a positive electrode is remarkable.

A test cell composed of a working electrode having a lithium-containing silicon oxide Li _x SiO _y used as a negative electrode active material of the present invention, a counter electrode made of lithium metal, and a non-aqueous electrolyte is charged and discharged, and electrochemically Li _x SiO _y absorbs and desorbs lithium ions to obtain a lithium content x of the working electrode.
The relationship between the potential and the potential and polarization was investigated. As a result, capacity can be stably repeatedly charged and discharged, i.e. the oxide Li _x the amount of lithium ions can be electrochemically absorbing and desorbing into SiO _y is limited, Li _x SiO _y and the lithium content x
It was found that the polarization (internal resistance) of the electrodes changed significantly. The oxide Li _x SiO _y varies depending on the amount of oxygen y, but when x> 4, the polarization becomes significantly large, and lithium ions are less likely to be occluded at a practically high current density. Precipitates on top and forms dendrites. It was found that when this dendrite was extremely large, it penetrated the separator and reached the counter electrode, causing an internal short circuit. Also, it was found that even after discharging after charging, when X <1.5, the polarization was still large and the potential was extremely high (noble). That is, lithium-containing silicon oxide Li _x Si
O _y varies depending on the oxygen amount y, but when the lithium content x is in the range of 1.5 ≦ x ≦ 4, the polarization (internal resistance) during charge / discharge is small, the potential is base, and the charge / discharge as the negative electrode is It has excellent characteristics. In particular, when 2 ≦ x ≦ 3.9, the potential is base, the polarization is small, and the efficiency (reversibility) of repeated charging / discharging is high, and the internal resistance of a battery using this as a negative electrode active material is small, and particularly charging / discharging It has excellent characteristics.

The present invention was made on the basis of the above-mentioned findings, and as a negative electrode active material of this type of battery, it is represented by the composition formula Li _x SiO _y , and has a lithium content x and an oxygen content y. A lithium ion occluding and desorbing substance composed of a lithium-containing silicon oxide in which the respective values are 1.5 ≦ x ≦ 4 and 0 <y <2 is used. That is, it is an oxide of silicon containing lithium in its crystal structure or in an amorphous structure and capable of inserting and extracting lithium ions by an electrochemical reaction in a non-aqueous electrolyte. The composite oxide has a composition in which x, which is a ratio of 1.5 to 4.0, and y, which is a ratio of the number of oxygen atoms to the number of silicon atoms, is larger than 0 and smaller than 2. The state of lithium in this composite oxide is preferably mainly ionic, but not limited thereto.

The lithium-containing silicon oxide Li _x SiO _y used as the negative electrode active material of the battery of the present invention (provided that 1.
As a preferable manufacturing method of 5 ≦ x ≦ 4 and 0 <y <2), the following two kinds of methods can be mentioned, but not limited thereto. The first method is to mix or mix each of simple substances of silicon and lithium or a compound thereof at a predetermined molar ratio, and in a non-oxidizing atmosphere such as an inert atmosphere or in a vacuum, or when silicon and lithium have a predetermined content. In this method, a composite oxide of silicon and lithium is formed by heat treatment in an atmosphere in which the amount of oxygen is controlled so that the oxidation number is reached. Each of the starting compounds, silicon and lithium, should be heat-treated in a non-oxidizing atmosphere such as oxides, hydroxides, salts such as carbonates and nitrates, or organic compounds. Compounds that produce the respective oxides are preferred. As a method of mixing these starting materials, other than a method of directly dry mixing powders of the respective materials, these raw materials are dissolved or dispersed in water, alcohol or another solvent,
After uniformly mixing or reacting in a solution, a method of drying,
Various methods such as a method of atomizing or ionizing these raw materials by heating, electromagnetic waves, light or the like and simultaneously or alternately depositing or precipitating are possible. The temperature of the heat treatment carried out after or while mixing the raw materials in this manner varies depending on the starting raw material and the heat treatment atmosphere,
Synthesis is possible at 0 ° C or higher, preferably 600 ° C
The above temperature is good. On the other hand, in an inert atmosphere or in a vacuum, a disproportionation reaction of silicon and tetravalent silicon oxide may occur at a temperature of 800 ° C. or higher. In such a case, the temperature of 600 to 800 ° C. preferable.

Among these combinations of starting materials, as a lithium feed material, oxidation is carried out by heat treatment such as lithium oxide L2O, lithium hydroxide LiOH, salts such as Li ₂ CO ₃ or LiNO ₃ and hydrates thereof. A lithium compound that produces lithium is used, and a simple substance of silicon or a lower oxide of silicon SiO _{y '} (where 0 <
When y '<2) is used, the mixture can be synthesized by heat-treating the mixture in an oxygen-free atmosphere such as an inert atmosphere or in a vacuum, and the amount of oxygen or oxygen in the heat-treatment atmosphere can be used. Partial pressure and the like are easy to control, and the production is easy, which is particularly preferable.

Further, when various silicic acids having hydrogen as a silicon compound are used as a starting material or when lithium hydroxide or the like is used as a lithium compound, hydrogen is not completely desorbed by heat treatment, It is possible that a part of the product remains after the heat treatment and lithium and hydrogen coexist, which is included in the present invention. Further, together with lithium or a compound thereof and silicon or a compound thereof, another alkali metal such as sodium, potassium or rubidium, an alkaline earth metal such as magnesium or calcium and / or iron, nickel, cobalt, manganese, vanadium, titanium or niobium. , Tungsten, molybdenum, copper, zinc, tin,
Lead, aluminum, indium, bismuth, gallium,
Other metals or non-metal elements such as germanium, carbon, boron, nitrogen, phosphorus, etc., or their compounds, etc. are also added and mixed, and the mixture is heat-treated. Can also coexist with, and these cases are also included in the present invention.

The lithium-containing silicon oxide thus obtained can be used as a negative electrode active material as it is or after being optionally subjected to processing such as pulverization and granulation. Further, in the same manner as in the second method described below, the lithium-containing silicon oxide is further occluded with lithium ions by an electrochemical reaction between the lithium-containing silicon oxide and lithium or a substance containing lithium, or On the contrary, the lithium oxide may be released from the composite oxide to increase or decrease the lithium content and be used as the negative electrode active material.

In the second method, a lower silicon oxide SiO _y (2>y> 0) containing no lithium is previously synthesized, and the obtained lower silicon oxide SiO _y is mixed with lithium or lithium. This is a method of obtaining a lower oxide of silicon Li _x SiO _y containing lithium by causing lithium ions to be absorbed in the lower oxide of silicon SiO _y by an electrochemical reaction with a substance contained therein. As such a lower oxide SiOy of silicon, SiO _1.5 (Si ₂ O ₃ ),
SiO _1.33 (Si ₃ O ₄ ), SiO and SiO _0.5 (Si ₂
In addition to stoichiometric compositions such as O), y may be of any composition in which y is greater than 0 and less than 2. Further, these lower oxides of silicon such as SiO _y can be produced by various known methods as described below. That is, (1) a method in which silicon dioxide SiO ₂ and silicon Si are mixed at a predetermined molar ratio and heated in a non-oxidizing atmosphere or in a vacuum, (2) silicon dioxide SiO ₂ is a reducing gas such as hydrogen H _2. A method of heating in a predetermined amount to reduce a predetermined amount, (3) a method of mixing silicon dioxide SiO ₂ with a predetermined amount of carbon C or a metal, and heating to reduce a predetermined amount, (4) an oxygen gas or oxidation of silicon Si A method of heating an object to oxidize it by a predetermined amount, (5) a CVD method or a plasma CVD method in which a mixed gas of a silicon compound gas such as silane SiH ₄ and oxygen O ₂ is heated or plasma-decomposed.

Further, the lower oxide SiO _y of the silicon includes
Along with silicon, hydrogen, sodium, potassium, rubidium, and other alkali metals, magnesium, calcium, and other alkaline earth metals, and / or iron, nickel, cobalt, manganese, vanadium, titanium, niobium, tungsten,
Other metal or non-metal element such as molybdenum, copper, zinc, tin, lead, aluminum, indium, bismuth, gallium, germanium, carbon, boron, nitrogen, phosphorus, etc. may be contained, and in these cases, the present invention is also included. included.

The storage of lithium ions by the electrochemical reaction of the silicon to the lower oxide SiO _y can be carried out in the battery after the battery is assembled, or inside or outside the battery during the battery manufacturing process, Specifically, it can be performed as follows. That is, (1) one of the electrodes (working electrode) is formed by molding the lower oxide of silicon or a mixture of the lower oxide of silicon and a conductive agent, a binder or the like into a predetermined shape, and contains metallic lithium or lithium. The other electrode (counter electrode) is used as the other electrode (counter electrode) to come into contact with the lithium ion conductive non-aqueous electrolyte so that both electrodes face each other to form an electrochemical cell, and the working electrode is energized with an appropriate current in the direction of cathodic reaction. Lithium ions are chemically absorbed in the lower oxide of silicon. A non-aqueous electrolyte secondary battery is constructed by using the obtained working electrode as it is as a negative electrode or as a negative electrode active material constituting the negative electrode. (2) Molding the lower oxide of silicon or a mixture thereof with a conductive agent, a binder and the like into a predetermined shape,
Lithium or an alloy of lithium or the like is pressure-bonded or brought into contact therewith to form a laminated electrode, which is incorporated as a negative electrode in a non-aqueous electrolyte secondary battery. A method of forming a kind of local battery by exposing the laminated electrode to the electrolyte in the battery, and self-discharging to electrochemically occlude lithium in the lower oxide of silicon. (3) A non-aqueous electrolyte secondary battery is constructed using the lower oxide of silicon as a negative electrode active material and a material containing lithium and capable of inserting and extracting lithium ions as a positive electrode active material. A method in which lithium ions released from the positive electrode by being charged when used as a battery are occluded in the lower oxide of silicon. The particle diameter of the silicon oxide or the lithium-containing silicon oxide is preferably 500 μm or less, more preferably 100 μm or less, and particularly 50 to 50 μm.
0.1 μm is good. Specific surface area is 0.05-100 m ³ /
g is preferable, more preferably 0.1 to 50 m ³ / g,
Particularly, 0.1 to ³⁰ m ³ / g is good.

The lithium-containing silicon oxide Li _x SiO _y thus obtained is used as a negative electrode active material. on the other hand,
Iron sulfide is a substance that has been studied as a battery active material, but it has not been put to practical use as a 1.5V secondary battery. It is considered that there is a problem in that the characteristics greatly change depending on the usage.

FIG. 1 is a sectional view showing an example of a test cell used for evaluating the charge / discharge characteristics of the active material of the non-aqueous electrolyte secondary battery according to the present invention. In the figure, reference numeral 1 is a counter electrode case which also serves as a counter electrode terminal, which is obtained by drawing a stainless steel plate having Ni plated on one outer surface. 3 is a counter electrode, which is obtained by punching out a lithium foil having a predetermined thickness to a diameter of 14 mm and crimping it to the inside of the counter electrode case 1. Reference numeral 7 denotes a working electrode case made of stainless steel whose outer surface is plated with Ni, and also serves as a working electrode terminal. Reference numeral 5 is a working electrode constituted by using an active material according to the present invention described later, 6 is a working electrode current collector made of a conductive adhesive containing carbon as a conductive filler, and the working electrode 5 and the working electrode are The case 7 is bonded and electrically connected. 4 is a separator made of a polypropylene porous film, which is impregnated with an electrolytic solution. Numeral 8 is 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 at the same time the working electrode case opening edge is inward. By folding and crimping, the battery contents are hermetically sealed.
The electrolyte is lithium hexafluorophosphate L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 1.
iPF ₆ was used after dissolving 1 mol / l. The size of the test cell was 20 mm in outer diameter and 1.6 mm in thickness.

The working electrode 5 was manufactured as follows. Commercially available FeS was crushed and sized by an automatic mortar and used as the active material of the working electrode. Graphite as a conductive agent and polyvinylidene fluoride as a binder were mixed with this active material at a weight ratio of 45:45:10 to prepare a working electrode mixture. Next, this working electrode mixture was pressure-molded at ² ton / cm ² into a pellet having a diameter of 4.05 mm and a thickness of 0.3 mm to prepare a working electrode 5. Thereafter, the working electrode 5 thus obtained is bonded to the working electrode case 7 by using a working electrode current collector 6 made of a conductive resin adhesive containing carbon as a conductive filler, and integrated at 100 ° C. The above-mentioned test cell was prepared by using the dried product under reduced pressure for 8 hours.

The test cell thus prepared was set to 0.1
FIG. 2 shows the cycle characteristics when a charging / discharging cycle was performed under the conditions of a discharge (D) end voltage of 0 V and a charge (C) end voltage of 2.5 V at a constant current of mA. In the figure, D1 indicates the first discharge, D2 indicates the second discharge, Dn indicates the nth discharge, and Cn indicates the nth charge.

It can be seen from FIG. 2 that the capacity has decreased since the first discharge (D1). It is presumed that the structure change of FeS occurs in the second flat portion of the discharge curve of D1 and the capacity is reduced. That is, Fe
If lithium ions enter S too much, the FeS structure is destroyed and charging / discharging becomes impossible.

Therefore, a similar test cell was subjected to a charge / discharge cycle at a constant current of 0.1 mA under the conditions of an end voltage of discharge (D) of 11.0 V and an end voltage of charge (C) of 2.5 V, and two steps were performed. FIG. 3 shows the cycle characteristics when lithium ions were prevented from entering the flat part of the eyes. It can be seen that the capacity is larger and the deterioration is less than that in FIG. From these results, considering that the amount of lithium that does not lower the potential of FeS to 1 V or less, that is, 1.1 mol or less of lithium per 1 mol of FeS, the characteristics of FeS are killed unless the battery is designed. Become. Further, when comparing 1D and 3D in FIG. 3, there is a difference of about 1 mAh. This is lithium that remains in the FeS crystal and does not participate in charging and discharging. Therefore, 0.25 mol or more of lithium per 1 mol of FeS If not, it cannot be charged and discharged. In addition, since FeS is usually susceptible to Fe deficiency and variations in manufacturing, the amount of S relative to Fe is ± 3.
A fluctuation of about 0% can be used as an active material without any problem. That is, a lithium-containing iron sulfide is represented by the composition formula Li _x FeS _y , and the lithium content x and the sulfur content y are 0.25 ≦ x ≦ 1.1 and 0.7 <y <1.3, respectively. It is important to be. The particle size of iron sulfide or lithium-containing iron sulfide is preferably 500 μm or less, more preferably 100 μm or less, and particularly 50 to 0.1.
μm is good. The specific surface area 0.05~100m ³ / g, more preferably 0.1~50m3 / g, especially 0.1~30m ³ / g is good.

In the present invention, it has been found that the capacity can be remarkably increased by using a lithium-containing iron sulfide having a large capacity as a battery active material of a battery of about 1.5V. In particular, the composition formula Li _x Si that the present inventors have previously applied for
The use of a lithium-containing silicon oxide represented by O _y (where 0 ≦ x, 0 <y <2) as the negative electrode and FeS as the positive electrode significantly increases the capacity.

As the electrolyte, γ-butyrolactone, propylene carbonate, ethylene carbonate,
LiCl as a supporting electrolyte in a single or mixed solvent of organic solvents such as butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, 1,2-dimethoxyethane, tetrahydrofuran, dioxolane, dimethylformamide.
O ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Li
Non-aqueous (organic) electrolytic solution in which a lithium ion dissociable salt such as (CF ₃ SO ₂ ) ₂ N is dissolved, and a polymer solid in which the lithium salt is solid-dissolved in a polymer such as polyethylene oxide or a crosslinked polyphosphazene Any lithium ion conductive non-aqueous electrolyte such as an electrolyte or an inorganic solid electrolyte such as Li ₃ N or LiI may be used. Particularly, in a mixed solvent of cyclic alkyl carbonate such as propylene carbonate, ethylene carbonate and butylene carbonate and chain alkyl carbonate such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, LiPF ₆ , LiCl
It is particularly preferable to use an organic electrolyte solution in which a salt such as O ₄ , LiBF ₄ or LiCF ₃ SO ₃ is dissolved, because a battery having excellent charge / discharge characteristics and a long cycle life can be obtained.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Example 1) In this example, FeS was used as the positive electrode active material and SiO was used as the negative electrode active material. The positive electrode, the negative electrode, and the electrolytic solution produced as described below were used. Also,
The battery had an outer diameter of 6.8 mm and a thickness of 2.1 mm. A cross-sectional view of the battery is shown in FIG.

The positive electrode was manufactured as follows. Commercial F
Graphite as a conductive agent and crosslinked acrylic acid resin and fluororesin as a binder are mixed at a weight ratio of 82: 10: 7: 1 to obtain a positive electrode mixture. Diameter of mixture is ² ton / cm ² and 4.0
5mm thick 0.54mm pellets are pressure molded and weigh 2
It was 1.0 mg. Thereafter, the positive electrode case 101 is obtained by using the positive electrode pellet 101 thus obtained and the electrode current collector 102 made of a conductive resin adhesive having carbon as a conductive filler.
After adhering to 3 and integrating, it was dried under reduced pressure at 150 ° C. for 8 hours.

The negative electrode was manufactured as follows. Commercially available silicon monoxide (SiO) was pulverized and sized to a particle size of 44 μm or less by an automatic mortar and used as the active material of the working electrode.
Graphite as a conductive agent and polyvinylidene fluoride as a binder are added to this active material at a weight ratio of 45: 4, respectively.
The mixture was mixed at a ratio of 5:10 to obtain a negative electrode mixture. Mix 2
Pellets having a diameter of 4.05 mm and a thickness of 0.49 mm at ton / cm ² were pressed and used.

The pellet weight was 11.5 mg. After that, the negative electrode pellets 104 thus obtained are bonded and integrated with the negative electrode case 105 by using the electrode current collector 2 made of a conductive resin adhesive containing carbon as a conductive filler, and then at 100 ° C. It was dried under reduced pressure for an hour. Further, a punched lithium foil 106 having a diameter of 4 mm and a thickness of 0.4 mm was pressure-bonded onto the pellet to obtain a lithium-negative electrode pellet laminated electrode. Li _x out of the stretched lithium
It is known from experiments that lithium of _x 1.5 to 2 of SiO _{y is} a part that does not participate in charge and discharge. When this lithium is calculated as 2, the lithium used for charging and discharging is about 5.57 mAh. This lithium content is FeS 1
Since it is 1.08 mol with respect to mol and is 1.1 mol or less, the structure of FeS is not destroyed.

The electrolytic solution 107 was prepared by mixing LiClO ₄ in a mixed solvent of propylene carbonate, ethylene carbonate and ethylmethyl carbonate at a volume ratio of 1: 1: 2 and 1 mol / mol.
1 The dissolved product was used. The battery thus manufactured was discharged at a constant current of 50 μA and a final voltage of 0.7 V and
A charge / discharge cycle was performed under the conditions of 0 μA constant current and charging up to 2.3V. The charge / discharge characteristics at this time are shown in FIG.

Example 2 In this example, lithium-containing manganese oxide was used as the positive electrode active material, and Fe was used as the negative electrode active material.
This is the case when S is used. The positive electrode, the negative electrode, and the electrolytic solution produced as described below were used. The battery had an outer diameter of 6.8 mm and a thickness of 2.1 mm.

The positive electrode was manufactured as follows. It was obtained by mixing electrolytic manganese dioxide MnO ₂ with lithium hydroxide and lithium nitrate so that the molar ratio of Mn: Li was 1: 0.3, and then heat-treating the mixture at 400 ° C. for 6 hours in the atmosphere. The product was used as the active material. This active material is mixed with graphite as a conductive agent and a cross-linking acrylic resin and a fluororesin as a binder at a weight ratio of 87: 10: 3 to prepare a positive electrode mixture. 2 to
Pellets having a diameter of 4.05 mm and a thickness of 0.96 mm at n / cm ² were pressure-molded and dried under reduced pressure at 150 ° C. for 10 hours to obtain a positive electrode having a weight of 31.2 mg. After that, the positive electrode pellet 101 thus obtained is adhered to and integrated with the positive electrode case 103 by using the electrode current collector 102 made of a conductive resin adhesive containing carbon as a conductive filler, and then at 150 ° C. It was dried under reduced pressure for an hour.

The negative electrode was manufactured as follows. Commercial F
Graphite as a conductive agent is mixed with crushed eS, and cross-linking acrylic resin and fluorine resin as a binder are mixed at a weight ratio of 82: 10: 7: 1 to form a positive electrode mixture. This positive electrode material mixture has a diameter of 4.0 at ² ton / cm ^2.
5mm thick 0.39mm thick pellets are pressed and weighed 1
It was set to 5.0 mg. Then, the negative electrode pellet 104 thus obtained is used as the negative electrode case 10 using the electrode current collector 2 made of a conductive resin adhesive containing carbon as a conductive filler.
After being adhered to and integrated with No. 5, dried under reduced pressure at 100 ° C. for 8 hours. In addition, lithium foil 106 on the pellets
4 mm in diameter and 0.15 mm in thickness (having a capacity of 3.88 mAh), which was punched out, were pressed to obtain a lithium-negative electrode pellet laminated electrode. The lithium used for charging and discharging 3.
At 88 mAh, the amount of lithium is 1.04 mol per 1 mol of FeS, which is less than 1.1 mol.
Does not break the structure of.

The electrolytic solution 107 was prepared by mixing LiClO ₄ in a mixed solvent of propylene carbonate, ethylene carbonate and ethylmethyl carbonate in a volume ratio of 1: 1: 2 and 1 mol / mol.
1 The dissolved product was used. The battery thus manufactured was discharged at a constant current of 50 μA and a final voltage of 0.7 V and
A charge / discharge cycle was performed under the conditions of 0 μA constant current and charging up to 2.3V. The charge / discharge characteristics at this time are shown in FIG.

[0037]

According to the present invention, it has been found that the capacity can be remarkably increased by using iron sulfide as a battery active material. In particular, the composition formula Li _x that the present inventors have previously applied for
SiO _y (provided that 0 ≦ x, 0 <y <2) is used as a negative electrode, and a lithium oxide containing silicon is used as a positive electrode, and an iron sulfide is used as a positive electrode. It is possible to obtain a secondary battery of around 1.5 V with excellent charge / discharge characteristics. Also, the charge and discharge efficiency is high,
It is possible to obtain a secondary battery that is extremely stable and has a long cycle life, without the occurrence of defects such as internal short circuit due to dendrite formation.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a structure of a test cell used for performance evaluation of a negative electrode active material.

FIG. 2 shows a test cell manufactured by a constant current of 0.1 mA,
Discharge (D) end voltage 0V, charge (C) end voltage 2.
It is a cycle characteristic figure when a charging / discharging cycle is performed on conditions of 5V.

FIG. 3 shows a test cell manufactured by a constant current of 0.1 mA,
It is a cycle characteristic view when a charging / discharging cycle is performed under the conditions of an end voltage of discharge (D) of 1.0V and an end voltage of charge (C) of 2.5V.

FIG. 4 is a cross-sectional view of a coin-type lithium secondary battery of the present invention.

FIG. 5 uses FeS as the positive electrode active material and Si as the negative electrode active material.
It is a charge / discharge characteristic figure of the lithium secondary battery of this invention which used O.

FIG. 6 is a charge / discharge characteristic diagram of a lithium secondary battery of the present invention in which a lithium-containing manganese oxide is used as a positive electrode active material and FeS is used as a negative electrode active material.

[Explanation of symbols]

1 counter case 3 opposite poles 4 separator 5 Working pole 6 Working electrode current collector 7 Working pole case 8 gasket 101 Positive electrode pellet 102 electrode collector 103 Positive case 104 negative electrode pellet 105 Negative electrode case 106 lithium foil 107 Electrolyte 108 gasket 109 separator

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kensuke Tahara, 1-8 Nakase, Mihama-ku, Chiba, Chiba Seiko Electronics Co., Ltd. (72) Akifumi Sakata 1-8, Nakase, Mihama-ku, Chiba, Chiba Seiko Electronics Industry Co., Ltd. (72) Inventor Hideharu Onodera 1-8 Nakase, Nakase, Mihama-ku, Chiba, Chiba Seiko Electronics Co., Ltd. (56) Reference JP-A-8-264182 (JP, A) JP-A-6- 342661 (JP, A) JP-A-2-265167 (JP, A) JP-A-61-22577 (JP, A) JP-A-6-325765 (JP, A) JP-A-8-130011 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 4/02 H01M 4/58

Claims (2)

(57) [Claims] 1. A composition formula LixFeSy (0.25 ≦ x ≦
1.1, 0.7 <y <1.3), a positive electrode using an iron sulfide containing lithium as an active material, and a composition formula L
A non-aqueous electrolyte secondary battery comprising a negative electrode using a silicon oxide containing lithium represented by ixSiOy (1.5 ≦ x ≦ 4, 0 <y <2) as an active material. 2. A positive electrode using a manganese oxide containing lithium as an active material, and a composition formula LixFeSy (0.25
A non-aqueous electrolyte secondary battery comprising a negative electrode using an iron sulfide containing lithium represented by ≦ x ≦ 1.1, 0.7 <y <1.3) as an active material.