JP2004356092A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode material capable of improving capacity, charging/discharging efficiency, and charging/dischaging cycle characteristics, and to provide a battery using the same. <P>SOLUTION: A negative electrode 22 is formed so as to precipitate Li metal in the course of charging, and a capacity of the negative electrode 22 contains a capacity component caused by storage and release of Li and a capacity component caused by the precipitation and dissolution of Li, and is expressed by the sum of them. The positive electrode 21 contains Li<SB>x</SB>M1<SB>1-y</SB>M2<SB>y</SB>O<SB>2-z</SB>, or Li<SB>c</SB>Mn<SB>2-d</SB>M2<SB>d</SB>O<SB>4-e</SB>(M1 represents Co or Ni, 1.00<x<1.35, 1.00<c<1.35). By the above, reactivity of the positive electrode 21 is lowered, and ether having resistance to reduction and high reactivity to oxidation reaction can be used, and reduction reaction of active lithium can be restrained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery and a positive electrode used therewith, and in particular, the capacity of the negative electrode includes a capacity component due to occlusion and release of light metal, and a capacity component due to precipitation and dissolution of light metal, and a battery represented by the sum thereof and the battery It relates to the positive electrode used.

  In recent years, portable electronic devices represented by mobile phones, PDAs (Personal Digital Assistants) or notebook computers have been energetically reduced in size and weight. There is a strong demand for an improvement in the energy density of a battery serving as a driving power source, particularly a secondary battery.

  As a secondary battery capable of obtaining a high energy density, for example, a lithium ion secondary battery using a material capable of inserting and extracting lithium (Li) such as a carbon material by an electrochemical reaction for a negative electrode is used. is there. In a lithium ion secondary battery, since the lithium stored in the negative electrode material is designed to be in an ion state, the energy density largely depends on the number of lithium ions that can be stored in the negative electrode material. Therefore, it is considered that the energy density of the lithium ion secondary battery can be further improved by increasing the amount of lithium ions absorbed. However, there is a theoretical limit of 372 mAh in terms of the amount of electricity per gram of graphite, which is currently regarded as a material capable of inserting and extracting lithium ions most efficiently. It is being raised to its limits by development activities.

As a secondary battery capable of obtaining a high energy density, there is a lithium metal secondary battery using lithium metal for a negative electrode and utilizing only precipitation and dissolution of lithium metal for a negative electrode reaction. A lithium metal secondary battery has a theoretical electrochemical equivalent of lithium metal as large as 2054 mAh / cm ³ , which is equivalent to 2.5 times that of graphite used in a lithium ion secondary battery, and is higher than that of a lithium ion secondary battery. It is expected that energy density can be obtained. Until now, many researchers have conducted research and development on the practical use of lithium metal secondary batteries (for example, see Non-Patent Document 1).

  However, the lithium metal secondary battery has a large deterioration in discharge capacity upon repeated charging and discharging, and is difficult to put into practical use. This capacity deterioration is due to the fact that the volume of the negative electrode expands greatly when lithium is deposited, and conversely shrinks when lithium is dissolved. In particular, when lithium is deposited unevenly, the dissolution reaction and the precipitation reaction become more difficult to reversibly proceed. This is because the non-uniformly deposited lithium has a large specific surface area, and is consumed to form a film on the surface of the negative electrode by reacting with the electrolytic solution or to be easily dropped off during dissolution.

Thus, in recent years, secondary batteries have been developed in which the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum of the two components (for example, see Patent Document 1). 1). In this method, a carbon material capable of inserting and extracting lithium is used for a negative electrode, and lithium is deposited on the surface of the carbon material during charging. According to this secondary battery, it is expected that charge / discharge cycle characteristics are improved while achieving high energy density.
Edited by Jean-Paul Gabano, "Lithium Batteries", London, New York, Academic Press, 1983 International Publication No. 01/22519 pamphlet JP-A-9-213368 JP-A-11-26016 JP-A-11-26017 JP 2001-6733 A JP-A-2002-358963 JP-A-7-201359 JP-A-2002-33119

  However, even this secondary battery has a problem that sufficient charge / discharge efficiency and charge / discharge cycle characteristics cannot be obtained. As a cause thereof, it is considered that the reactivity of the deposited lithium is high, and lithium that cannot contribute to the capacity increases mainly in the negative electrode in each cycle, and the amount of active lithium flowing between the positive electrode and the negative electrode decreases. In order to prevent such cycle deterioration, it is considered necessary to use an electrolyte which is not easily reduced to active lithium.

  Heretofore, many lithium ion secondary batteries using ether that is strong in reduction as an electrolyte have been reported (for example, see Patent Documents 2 to 8).

  However, although ether can suppress the reduction reaction at the negative electrode, the oxidation reaction proceeds on the positive electrode side, and thus there is a problem that the battery is deteriorated.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a positive electrode capable of improving capacity, charge / discharge efficiency, and charge / discharge cycle characteristics, and a battery using the same.

The first positive electrode according to the present invention has a capacity including a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is used together with a negative electrode represented by the sum thereof, and has a general formula Li _x M1 _1-y M2 _y O _2-z (wherein, M1 represents at least one of cobalt (Co) and nickel (Ni), and M2 is a member of the group consisting of metal elements other than M1 and having an atomic number of 11 or more. Wherein x, y and z are values in the range of 1.00 <x <1.35, 0 ≦ y <1.0, and −0.1 ≦ z ≦ 0.1. )).

The second positive electrode according to the present invention is used together with the negative electrode whose capacity includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is used together with the negative electrode represented by the general formula Li _c Mn _2-d M3 _d O _4-e (wherein, M3 represents at least one member from the group consisting of metal elements having an atomic number of 11 or more other than manganese (Mn); 00 <c <1.35, 0 ≦ d <0.5, and −0.2 ≦ e ≦ 0.2).

A first battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. a shall, positive electrode, the general formula Li _x M1 in _{1-y M2 y O 2-} z ( wherein, M1 represents at least one of cobalt and nickel, M2 is other than M1 atomic number 11 or more Represents at least one member from the group consisting of metal elements, wherein x, y and z are 1.00 <x <1.35, 0 ≦ y <1.0, and −0.1 ≦ z ≦ 0.1 This is a value within the range.).

A second battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. a shall, positive electrode, in the general formula _{Li c Mn 2-d M3 d} O 4-e ( wherein, M3 represents at least one selected from the group consisting of atomic number 11 or more metal elements other than manganese , C, d, and e are values in the range of 1.00 <c <1.35, 0 ≦ d <0.5, and −0.2 ≦ e ≦ 0.2.) It contains an oxide.

  In the first and second positive electrodes and the first and second batteries according to the present invention, since the mass ratio x or c of lithium in the composite oxide is larger than 1.00, even at a high voltage of 4 V or more, Reaction with the electrolyte is suppressed. Therefore, an ether that is strong in reduction but highly reactive to an oxidation reaction can be used for the electrolyte, and it is possible to suppress a reduction reaction of active light metal deposited on the negative electrode. Further, deterioration is suppressed even in a higher voltage region than the conventional voltage of 4.2 V or more and 4.5 V or less, so that the capacity is further improved.

According to the first positive electrode and the first cell of the present invention, is represented by the general formula _{Li x M1 1-y M2 y} O 2-z, including substance amount ratio x is larger composite oxide than 1.00 Therefore, according to the second positive electrode and the second battery, the composite in which the material amount ratio c represented by the general formula Li _c Mn _2-d M3 _d O _4-e is larger than 1.00. Since the oxide is included, the progress of the oxidation reaction of the electrolyte at a high voltage of 4 V or more can be suppressed. Therefore, an ether which is strong in reduction but highly reactive to an oxidation reaction can be used, and a reduction reaction of an active light metal deposited on the negative electrode can be suppressed. Further, a higher voltage operation of 4.2 V or more and 4.5 V or less can be performed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional structure of a secondary battery according to one embodiment of the present invention. This secondary battery is a so-called cylindrical type, and a band-shaped positive electrode 21 and a band-shaped negative electrode 22 are arranged inside a substantially hollow cylindrical battery can 11 with a separator 23 interposed therebetween, and are wound. The wound electrode body 20. The battery can 11 is made of, for example, nickel-plated iron (Fe), and has one end closed and the other end open. An electrolyte, which is a liquid electrolyte, is injected into the battery can 11 and impregnated in the separator 23. Further, a pair of insulating plates 12 and 13 are arranged perpendicularly to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14, and a positive temperature coefficient (PTC) element 16 are disposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery cover 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the thermal resistance element 16, and when the internal pressure of the battery becomes higher than a certain level due to an internal short circuit or external heating, the disk plate 15A is inverted. Then, the electrical connection between the battery cover 14 and the spirally wound electrode body 20 is cut off. The thermal resistance element 16 limits the current by increasing the resistance value when the temperature rises, and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and its surface is coated with asphalt.

  For example, a center pin 24 is inserted into the center of the spirally wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery cover 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded and electrically connected to the battery can 11.

  FIG. 2 illustrates a part of the spirally wound electrode body 20 illustrated in FIG. 1 in an enlarged manner. The positive electrode 21 has, for example, a structure in which a positive electrode mixture layer 21B is provided on both surfaces or one surface of a positive electrode current collector 21A having a pair of opposing surfaces. The cathode current collector 21A has a thickness of, for example, about 5 μm to 50 μm, and is made of a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode mixture layer 21B contains a positive electrode material capable of inserting and extracting lithium as a positive electrode active material (hereinafter, referred to as a positive electrode material capable of inserting and extracting lithium). A binder may be included. The thickness of the positive electrode mixture layer 21B is, for example, 80 μm to 250 μm. This thickness is the total thickness when the positive electrode mixture layer 21B is provided on both surfaces of the positive electrode current collector 21A.

  The positive electrode material capable of inserting and extracting lithium contains, for example, a composite oxide having the composition shown in Chemical formula 1 or a composite oxide having the composition shown in Chemical formula 2 at the time of complete discharge. The composite oxide shown in Chemical formula 1 and the composite oxide shown in Chemical formula 2 may be used as a mixture.

（式中、Ｍ１はコバルトおよびニッケルのうちの少なくとも一方を表し、Ｍ２はＭ１以外の原子番号１１以上の金属元素からなる群のうちの少なくとも１種を表し、ｘ，ｙおよびｚは、１．００＜ｘ＜１．３５、０≦ｙ＜１．０、−０．１≦ｚ≦０．１の範囲内の値である。）

(In the formula, M1 represents at least one of cobalt and nickel, M2 represents at least one member of the group consisting of metal elements having an atomic number of 11 or more other than M1, and x, y, and z represent 1. 00 <x <1.35, 0 ≦ y <1.0, −0.1 ≦ z ≦ 0.1.)

（式中、Ｍ３はマンガン以外の原子番号１１以上の金属元素からなる群のうちの少なくとも１種を表し、ｃ，ｄおよびｅは、１．００＜ｃ＜１．３５、０≦ｄ＜０．５、−０．２≦ｅ≦０．２の範囲内の値である。）

(Wherein, M3 represents at least one member of the group consisting of metal elements having an atomic number of 11 or more other than manganese, and c, d, and e are 1.00 <c <1.35, 0 ≦ d <0 .5, -0.2≤e≤0.2.)

  In the composite oxide shown in Chemical formula 1 or Chemical formula 2, since the material ratio x and c of lithium are larger than 1.00 and smaller than 1.35, the crystal structure is stabilized and the high voltage of 4 V or more is obtained. However, the reaction with the electrolytic solution is suppressed, and the deterioration is small even in a high voltage region of 4.2 V or more and 4.5 V or less. It is more preferable that the mass ratio x of lithium in Chemical Formula 1 is in the range of 1.05 <x <1.20, and the mass ratio c of lithium in Chemical Formula 2 is 1.05 <c <1.20 Is more preferably within the range. This is because the crystal structure of the composite oxide is further stabilized.

The composite oxide shown in Chemical formula 1 may contain cobalt or nickel alone in M1, but preferably contains both of them. Cobalt is preferable because it can increase the energy of the battery and improve the cycle characteristics, but is problematic in terms of the price and stable supply of the raw material, while nickel has a problem of charge and discharge per weight. This is because the capacity can be increased, but the crystal structure is not stable and the average discharge curve tends to be lower than that of LiCoO ₂ .

  In order to stabilize the crystal structure, M2 of Chemical Formula 1 preferably contains a metal element having an atomic number of 11 or more other than M1, for example, manganese, magnesium (Mg), aluminum, titanium (Ti), and vanadium (V ), Chromium (Cr), copper (Cu), niobium (Nb), molybdenum (Mo), iron (Fe), zinc (Zn), tin (Sn), gallium (Ga), calcium (Ca), and strontium ( It preferably contains at least one member from the group consisting of Sr), and particularly preferably contains manganese. This is because, in addition to stabilizing the crystal structure, the energy density can be increased while ensuring safety.

Specific examples of the composite oxide shown in Chemical formula 1 include Li _x CoO ₂ , Li _x NiO ₂ , Li _x Ni _0.4 Co _0.2 Mn _0.4 O ₂ , Li _x Ni _0.33 Co _0.33 Mn _0.33 O ₂ , Li _x Ni _0.45 Co _0.2 Mn _0.35 O ₂ , Li _x Ni _0.4 Co _0.4 Mn _0.2 O ₂ , Li _x Ni _0.2 Co _0.6 Mn _0.2 O ₂ , Li _x Ni _0.95 Al _0.05 O ₂ , Li _x Ni _0.80 Co _0.15 Al _0.05 O _{2 and the} like.

  M3 in Chemical formula 2 is also for stabilizing the crystal structure, for example, nickel, cobalt, magnesium, aluminum, titanium, vanadium, chromium, copper, niobium, molybdenum, iron, zinc, tin, calcium and strontium. It is desirable to include at least one member of the group consisting of

Specific examples of the composite oxide shown in Chemical Formula ₂ include Li _c Mn ₂ O ₄ and Li _c Mn _1.8 Mg _0.1 Al _0.1 O ₄ .

  The composite oxide shown in Chemical formula 1 or Chemical formula 2 is, for example, lithium, carbonates, nitrates, oxides or hydroxides of M1, and M2, or lithium, manganese, and carbonates, nitrates of M3, respectively. It can be manufactured by mixing and pulverizing an oxide or a hydroxide so as to have a desired composition, and then firing in an oxygen atmosphere, for example, in a range of 600 ° C. to 1000 ° C.

  Examples of the conductive agent include carbon materials such as graphite, carbon black, and Ketjen black, and one or more of them are used in combination. In addition to the carbon material, a metal material or a conductive polymer material may be used as long as the material has conductivity. Examples of the binder include synthetic rubbers such as styrene-butadiene rubber, fluorine rubber and ethylene propylene diene rubber, and polymer materials such as polyvinylidene fluoride, and one or more of them are mixed. Used.

  In order to achieve a high capacity, the positive electrode mixture layer 21B may be charged or discharged in a steady state (for example, after repeating charge and discharge about 5 times) at a charge / discharge of 280 mAh or more per 1 g of a negative electrode active material described later. It preferably contains lithium equivalent to the capacity, more preferably lithium equivalent to the charge / discharge capacity of 350 mAh or more.

  The negative electrode 22 has, for example, a structure in which a negative electrode mixture layer 22B is provided on both surfaces or one surface of a negative electrode current collector 22A having a pair of opposing surfaces, similarly to the positive electrode 21. The anode current collector 22A is made of, for example, a metal foil such as a copper (Cu) foil, a nickel foil, or a stainless steel foil having good electrochemical stability, electrical conductivity, and mechanical strength.

  The negative electrode mixture layer 22B includes, as a negative electrode active material, one or more of negative electrode materials capable of inserting and extracting lithium (hereinafter, referred to as negative electrode materials capable of inserting and extracting lithium). And may include, for example, the same binder as the positive electrode mixture layer 21B as necessary. The thickness of the negative electrode mixture layer 22B is, for example, 60 μm to 250 μm. This thickness is the total thickness when negative electrode mixture layer 22B is provided on both surfaces of negative electrode current collector 22A.

  Note that, in this specification, the term "storage / release of light metal such as lithium" means that light metal ions are electrochemically stored / released without losing their ionicity. This includes not only the case where the occluded light metal exists in a completely ionic state but also the case where the occluded light metal exists in a state that is not completely ionic. Such cases include, for example, occlusion by electrochemical intercalation reaction of light metal ions to graphite. In addition, occlusion of a light metal in an alloy containing an intermetallic compound or occlusion of a light metal by forming an alloy can also be mentioned.

  Examples of the anode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. These carbon materials are preferable because a change in crystal structure that occurs during charge and discharge is very small, a high charge and discharge capacity can be obtained, and good charge and discharge cycle characteristics can be obtained. Particularly, graphite is preferable because it has a large electrochemical equivalent and can obtain a high energy density.

As the graphite, for example, those having a true density of 2.10 g / cm ³ or more are preferable, and those having a true density of 2.18 g / cm ³ or more are more preferable. In order to obtain such a true density, it is necessary that the thickness of the C-axis crystallite in the (002) plane is 14.0 nm or more. The spacing between the (002) planes is preferably less than 0.340 nm, and more preferably in the range of 0.335 nm to 0.337 nm.

The graphite may be natural graphite or artificial graphite. In the case of artificial graphite, for example, it can be obtained by carbonizing an organic material, performing a high-temperature heat treatment, and pulverizing and classifying. The high-temperature heat treatment is performed by, for example, carbonizing at 300 ° C. to 700 ° C. in an inert gas stream such as nitrogen (N ₂ ) as necessary, and raising the temperature to 900 ° C. to 1500 ° C. at a rate of 1 ° C. to 100 ° C. per minute. Then, this temperature is maintained for about 0 to 30 hours and calcined, and at the same time, heated to 2000 ° C. or more, preferably 2500 ° C. or more, and the temperature is maintained for an appropriate time.

  Coal or pitch can be used as an organic material as a starting material. The pitch includes, for example, distillation (vacuum distillation, atmospheric distillation or steam distillation) of tars and asphalt obtained by pyrolyzing coal tar, ethylene bottom oil or crude oil at a high temperature, thermal polycondensation, extraction, Examples include those obtained by chemical polycondensation, those produced at the time of wood reflux, polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate, and 3,5-dimethylphenol resin. These coals or pitches exist as a liquid at a maximum of about 400 ° C. during carbonization, and when held at that temperature, aromatic rings condense and polycyclic, resulting in a laminated orientation state, and then about 500 ° C. or more To form a solid carbon precursor, ie, semi-coke (liquid phase carbonization process).

  Examples of the organic material include condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphen, and pentacene, and derivatives thereof (for example, carboxylic acids, carboxylic anhydrides, and carboxylic acids of the above compounds). Imides), or mixtures thereof. Further, condensed heterocyclic compounds such as acenaphthylene, indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenanthridine, derivatives thereof, and mixtures thereof can also be used.

  The pulverization may be performed before or after carbonization or calcination, or during the heating process before graphitization. In these cases, heat treatment for graphitization is finally performed in a powder state. However, in order to obtain a graphite powder having a high bulk density and a high breaking strength, it is preferable to heat-treat the raw material and then pulverize and classify the obtained graphitized molded body.

  For example, in the case of producing a graphitized molded body, coke as a filler and binder pitch as a molding agent or a sintering agent are mixed and molded, and then the molded body is heat-treated at a low temperature of 1000 ° C. or less. After repeating the firing step and the pitch impregnating step of impregnating the fired body with the melted binder pitch several times, heat treatment is performed at a high temperature. The impregnated binder pitch is carbonized and graphitized in the above heat treatment process. Incidentally, in this case, since the filler (coke) and the binder pitch are used as raw materials, the raw material is graphitized as a polycrystalline material, and sulfur and nitrogen contained in the raw materials are generated as a gas during heat treatment. Fine holes are formed in the path. Therefore, the vacancies facilitate the progress of the insertion and extraction reaction of lithium, and also have the advantage of high industrial processing efficiency. In addition, as a raw material of the molded body, a filler having moldability and sinterability itself may be used. In this case, it is not necessary to use a binder pitch.

The non-graphitizable carbon has a (002) plane spacing of 0.37 nm or more, a true density of less than 1.70 g / cm ³ and a differential thermal analysis (DTA) in air. Those which do not show an exothermic peak at 700 ° C. or higher are preferred.

  Such non-graphitizable carbon can be obtained, for example, by subjecting an organic material to a heat treatment at about 1000 ° C., followed by pulverization and classification. In the heat treatment, for example, carbonization is performed at 300 ° C. to 700 ° C. as needed (solid phase carbonization process), and then the temperature is increased to 900 ° C. to 1300 ° C. at a rate of 1 ° C. to 100 ° C. per minute. This is performed by holding for about 30 hours. The pulverization may be performed before or after carbonization, or during the heating process.

  As the organic material used as a starting material, for example, a furfuryl alcohol or furfural polymer or copolymer, or a furan resin which is a copolymer of these polymers and another resin can be used. Also, phenolic resins, acrylic resins, vinyl halide resins, polyimide resins, polyamideimide resins, polyamide resins, conjugated resins such as polyacetylene or polyparaphenylene, cellulose or derivatives thereof, crustaceans including coffee beans, bamboos, and chitosan Biocelluloses utilizing bacteria can also be used. Further, a functional group containing oxygen (O) is introduced into a petroleum pitch having an atomic ratio H / C of hydrogen atoms (H) to carbon atoms (C) of, for example, 0.6 to 0.8 (so-called oxygen crosslinking). The compound thus obtained can also be used.

  The oxygen content of this compound is preferably at least 3%, more preferably at least 5% (see JP-A-3-25253). This is because the oxygen content affects the crystal structure of the carbon material, and at a higher content, the physical properties of the non-graphitizable carbon can be increased, and the capacity of the negative electrode 22 can be improved. For example, petroleum pitch is used for distillation (vacuum distillation, atmospheric distillation or steam distillation) of tars obtained by pyrolyzing coal tar, ethylene bottom oil or crude oil at a high temperature, or asphalt. It is obtained by condensation, extraction or chemical polycondensation. Examples of the oxidative cross-linking method include a wet method in which an aqueous solution of nitric acid, sulfuric acid, hypochlorous acid, or a mixed acid thereof is reacted with petroleum pitch, and a method in which an oxidizing gas such as air or oxygen is reacted with petroleum pitch. A dry method or a method of reacting a solid reagent such as sulfur, ammonium nitrate, ammonium persulfate, or ferric chloride with petroleum pitch can be used.

  The organic material used as a starting material is not limited to these, and any other organic material may be used as long as it can be converted into non-graphitizable carbon through a solid-phase carbonization process by oxygen cross-linking or the like.

  Examples of the non-graphitizable carbon include those produced using the above-mentioned organic materials as starting materials, and compounds described in JP-A-3-137010, which contain phosphorus (P), oxygen and carbon as main components. It is preferable because the physical property parameters described above are shown.

  Examples of the negative electrode material capable of inserting and extracting lithium include a simple substance, alloy or compound of a metal element capable of forming an alloy with lithium, or a simple substance, alloy or compound of a semimetal element capable of forming an alloy with lithium. . These are preferable because a high energy density can be obtained. In particular, when used together with a carbon material, a high energy density can be obtained and excellent charge / discharge cycle characteristics can be obtained. In this specification, an alloy includes an alloy composed of one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. The structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and a structure in which two or more of them coexist.

Such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc, antimony (Sb), bismuth (Bi), and cadmium (Cd). , Magnesium, boron, gallium, germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf). These alloys or compounds, for example, those represented by the chemical formula Ma _s Mb _t Li _u or a chemical formula Ma _p Mc _q Md _r,. In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, Mb represents at least one of a metal element and a metalloid element other than lithium and Ma, Mc represents at least one kind of non-metallic element, and Md represents at least one kind of metal element and metalloid element other than Ma. The values of s, t, u, p, q, and r are s> 0, t ≧ 0, u ≧ 0, p> 0, q> 0, r ≧ 0, respectively.

  Among them, a simple substance, an alloy or a compound of a metal element or a metalloid element belonging to Group 14 of the long-period periodic table is preferable, and particularly preferable is silicon or tin, or an alloy or compound thereof. These may be crystalline or amorphous.

A specific example of such an alloy or such a compound, LiAl, AlSb, CuMgSb, SiB 4, SiB 6, Mg 2 Si, Mg 2 Sn, Ni 2 Si, TiSi 2, MoSi 2, CoSi 2, NiSi 2 _{, CaSi 2, CrSi 2, Cu} 5 Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 < v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO or LiSnO.

  In the case where the alloy or the compound of silicon or tin is in the form of powder, it can be obtained, for example, by a conventional method used in powder metallurgy. Conventional methods include, for example, a method in which a raw material is melted in a melting furnace such as an arc melting furnace or a high-frequency induction heating furnace, cooled, and then pulverized, or a single-roll quenching method, a twin-roll quenching method, a gas atomizing method, a water atomizing method. Alternatively, a method of rapidly cooling the molten metal of the raw material such as a centrifugal atomizing method, or a method of mechanical alloying after solidifying the molten metal of the raw material by a cooling method such as a single roll quenching method or a twin roll quenching method. A pulverizing method may be used. Particularly, a gas atomizing method or a mechanical alloying method is preferable. The synthesis and the pulverization are preferably performed in an inert gas atmosphere such as argon (Ar), nitrogen, or helium (He) or in a vacuum atmosphere in order to prevent oxidation by oxygen in the air.

Examples of the negative electrode material capable of inserting and extracting lithium include other metal compounds and polymer materials. Examples of other metal compounds include oxides such as iron oxide, ruthenium oxide, and molybdenum oxide, and LiN _3. Examples of the polymer material include polyacetylene, polyaniline, and polypyrrole.

  Among these negative electrode materials capable of storing and releasing lithium, those having an active lithium ion storage reaction are particularly desirable, and those having a charge / discharge potential relatively close to lithium metal are particularly desirable.

  Further, in this secondary battery, for example, by setting the charge capacity of the negative electrode material capable of inserting and extracting lithium to be smaller than the charge capacity of the positive electrode 21, the open circuit voltage (that is, the battery voltage) is excessive during the charging process. At a time point lower than the charging voltage, lithium metal starts to precipitate on the negative electrode 22. That is, when the open circuit voltage is lower than the overcharge voltage, lithium metal is deposited on the negative electrode 22. The capacity of the negative electrode 22 is based on the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium metal. And represented by the sum of Therefore, in this secondary battery, both the negative electrode material capable of inserting and extracting lithium and the lithium metal function as the negative electrode active material, and the negative electrode material capable of inserting and extracting lithium is the base material when lithium metal is deposited. It has become.

  The overcharge voltage refers to an open circuit voltage when the battery is in an overcharged state. For example, one of the guidelines set by the Japan Storage Battery Association (Battery Manufacturers Association) is “lithium metal secondary battery”. Refers to a voltage higher than the open circuit voltage of a "fully charged" battery as defined and defined in "Battery Safety Evaluation Guidelines" (SBA G1101). In other words, it refers to a voltage higher than the open circuit voltage after charging using the charging method, the standard charging method, or the recommended charging method used when obtaining the nominal capacity of each battery. Specifically, this secondary battery is fully charged when the open circuit voltage is 4.2 V, for example, and a negative electrode capable of inserting and extracting lithium in a part of the open circuit voltage in the range of 0 V to 4.2 V. Lithium metal is deposited on the surface of the material.

  As a result, in this secondary battery, a high energy density can be obtained, and the charge / discharge cycle characteristics and the rapid charge characteristics can be improved. This is similar to a conventional lithium metal secondary battery using lithium metal or a lithium alloy for the negative electrode in that lithium metal is deposited on the negative electrode 22, but lithium metal is used as a negative electrode material capable of inserting and extracting lithium. It is considered that the following advantages are brought about by the precipitation.

  First, in the conventional lithium metal secondary battery, it is difficult to deposit lithium metal uniformly, for example, as lithium metal precipitates as dendrites, causing deterioration of charge / discharge cycle characteristics.・ Removable negative electrode material generally has a large surface area and applies pressure to lithium metal that expands during charging and precipitates in voids, so in this secondary battery, pulverization of lithium metal and dendrite deposition are suppressed. That is, as compared with a lithium metal secondary battery, lithium metal is more uniformly deposited. Second, in the conventional lithium metal secondary battery, the volume change accompanying the precipitation and dissolution of lithium metal was large, which also deteriorated the charge / discharge cycle characteristics. Lithium metal precipitates also in the gaps between the particles of the detachable negative electrode material, so that the volume change is small. Third, in a conventional lithium metal secondary battery, the larger the amount of lithium metal deposited and dissolved, the greater the above problem. However, in this secondary battery, lithium is absorbed and stored by a negative electrode material capable of storing and releasing lithium. -Since the detachment also contributes to the charge / discharge capacity, the amount of lithium metal deposited and dissolved is small in spite of the large battery capacity. Fourth, in the conventional lithium metal secondary battery, when rapid charging is performed, the lithium metal is more unevenly deposited, so that the charge / discharge cycle characteristics are further deteriorated. Since lithium is inserted into the negative electrode material capable of inserting and extracting lithium, rapid charging becomes possible.

  In order to obtain these advantages more effectively, for example, the maximum deposition capacity of lithium metal deposited on the negative electrode 22 at the maximum voltage before the open circuit voltage becomes the overcharge voltage is such that lithium can be inserted and extracted. Preferably, the charge capacity is 0.05 times or more and 3.0 times or less of the charge capacity of the negative electrode material. If the amount of lithium metal deposited is too large, the same problem as in a conventional lithium metal secondary battery occurs. If the amount is too small, the charge / discharge capacity cannot be sufficiently increased. Further, for example, the discharge capacity of a negative electrode material capable of inserting and extracting lithium is preferably 150 mAh / g or more. This is because the greater the ability to insert and extract lithium, the smaller the amount of lithium metal deposited. The charge capacity of the negative electrode material is obtained, for example, from the amount of electricity when a negative electrode using lithium metal as a counter electrode and using the negative electrode material as a negative electrode active material is charged to 0 V by a constant current / constant voltage method. The discharge capacity capability of the negative electrode material is determined, for example, from the amount of electricity when the battery is discharged to 2.5 V over 10 hours or more by the constant current method.

  The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of a ceramic, and has a structure in which two or more kinds of these porous films are laminated. It may be. Above all, a porous film made of polyolefin is preferable because it has an excellent short-circuit prevention effect and can improve the safety of the battery by a shutdown effect. In particular, polyethylene is preferable as a material constituting the separator 23 because it can obtain a shutdown effect in a range of 100 ° C. or more and 160 ° C. or less and has excellent electrochemical stability. Polypropylene is also preferable, and any other resin having chemical stability can be used by copolymerizing or blending with polyethylene or polypropylene.

  This polyolefin porous film is, for example, a liquid polyolefin composition in a molten state is kneaded with a liquid low-volatile solvent in a molten state to form a uniform polyolefin composition high-concentration solution, which is then molded with a die. It is obtained by cooling to a gel-like sheet and stretching.

  As the low volatile solvent, for example, a low volatile aliphatic or cyclic hydrocarbon such as nonane, decane, decalin, p-xylene, undecane or liquid paraffin can be used. The blending ratio of the polyolefin composition and the low-volatile solvent may be 10% to 80% by mass, and more preferably 15% to 70% by mass, with the total of both being 100% by mass. preferable. If the amount of the polyolefin composition is too small, swelling or neck-in becomes large at the die exit during molding, and sheet molding becomes difficult. On the other hand, if the polyolefin composition is too large, it is difficult to prepare a uniform solution.

  When a high-concentration solution of the polyolefin composition is molded by a die, in the case of a sheet die, the gap is preferably, for example, 0.1 mm or more and 5 mm or less. Further, it is preferable that the extrusion temperature is 140 ° C. or more and 250 ° C. or less, and the extrusion speed is 2 cm / min or more and 30 cm / min or less.

  Cooling is performed at least to a gelling temperature or lower. As a cooling method, a method of directly contacting with cold air, cooling water, or another cooling medium, a method of contacting with a roll cooled by a refrigerant, or the like can be used. The high-concentration solution of the polyolefin composition extruded from the die may be taken off at a take-up ratio of 1 to 10 and preferably 1 to 5 before or during cooling. If the take-up ratio is too large, neck-in becomes large, and breakage tends to occur during stretching, which is not preferable.

  The stretching of the gel-like sheet is preferably performed by biaxial stretching, for example, by heating the gel-like sheet and using a tenter method, a roll method, a rolling method, or a combination thereof. At that time, either vertical or horizontal simultaneous stretching or sequential stretching may be used, but simultaneous secondary stretching is particularly preferable. The stretching temperature is preferably equal to or lower than the temperature obtained by adding 10 ° C. to the melting point of the polyolefin composition, and more preferably equal to or higher than the crystal dispersion temperature and lower than the melting point. If the stretching temperature is too high, an effective molecular chain orientation due to stretching cannot be performed due to melting of the resin, which is not preferable.If the stretching temperature is too low, the softening of the resin becomes insufficient and the film breaks during stretching. This is because it is easy to perform stretching at a high magnification.

  It is preferable that after stretching the gel-like sheet, the stretched film is washed with a volatile solvent to remove the remaining low-volatile solvent. After washing, the stretched film is dried by heating or blowing, and the washing solvent is volatilized. Examples of the washing solvent include hydrocarbons such as pentane, hexane, and hebutane; chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride; carbon fluorides such as ethane trifluoride; and ethers such as diethyl ether and dioxane. As described above, a volatile material is used. The washing solvent is selected according to the low-volatile solvent used, and used alone or in combination. Washing can be performed by a method of immersing in a volatile solvent for extraction, a method of sprinkling with a volatile solvent, or a method combining these. This washing is performed until the residual low-volatile solvent in the stretched film becomes less than 1 part by mass with respect to 100 parts by mass of the polyolefin composition.

  The electrolytic solution impregnated in the separator 23 contains a liquid solvent, for example, a non-aqueous solvent such as an organic solvent, and a lithium salt which is an electrolyte salt dissolved in the non-aqueous solvent. The liquid non-aqueous solvent is, for example, a non-aqueous compound having an intrinsic viscosity at 25 ° C. of 10.0 mPa · s or less. In addition, the intrinsic viscosity in a state where the electrolyte salt is dissolved may be 10.0 mPa · s or less. When a plurality of types of non-aqueous compounds are mixed to form a solvent, the intrinsic viscosity in the mixed state may be less than 10.0 mPa · s. What is necessary is just 10.0 mPa * s or less.

  The non-aqueous solvent contains, as a main solvent, one or more high dielectric constant solvents having a relatively high dielectric constant, and mixes one or more low viscosity solvents with the high dielectric constant solvent. It is desirable to include it. Examples of the high dielectric constant solvent include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, sulfolane acid, γ-butyrolactone, and valerolactones.

  Examples of the low-viscosity solvent include a chain carbonate having a symmetric structure such as diethyl carbonate or dimethyl carbonate, a chain carbonate having an asymmetric structure such as methyl ethyl carbonate or methyl propyl carbonate, and a carboxylic acid such as methyl propionate or ethyl propionate. An acid ester or a phosphoric acid ester such as trimethyl phosphate or triethyl phosphate is exemplified.

  It is preferable that the non-aqueous solvent contains one or more ethers in combination. This is because ether has high resistance to reduction and thus has low reactivity with lithium metal deposited on the negative electrode 22. Preferred examples of the ether include tetrahydropyran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 1,2-diethoxyethane, 1,3-dimethoxyethane, and derivatives thereof.

  In addition, non-aqueous solvents include vinylene carbonate, trifluoropropylene carbonate, 4-methyl-1,3-dioxolan, sulfolane, methylsulfolane, 2,4-difluoroanisole, A material to which 6-difluoroanisole or the like is added may be used. The content in these non-aqueous solvents is preferably 40% by volume or less, more preferably 20% by volume or less.

As the lithium salt, for example, LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCl or LiBr. As the lithium salt, any one kind may be used alone, or two or more kinds may be used in combination. When two or more kinds are used in combination, it is desirable that LiPF ₆ be the main component. This is because LiPF ₆ has high conductivity and excellent oxidation stability.

  The content (concentration) of these lithium salts is preferably in the range of 0.5 mol / kg to 3.0 mol / kg with respect to the solvent. If the content is out of this range, sufficient battery characteristics may not be obtained due to an extreme decrease in ionic conductivity.

  Note that, instead of the electrolytic solution, a gel electrolyte in which a polymer compound holds the electrolytic solution may be used. The gel electrolyte may be one having an ionic conductivity of 1 mS / cm or more at room temperature, and there is no particular limitation on the composition and the structure of the polymer compound. The polymer compound as described above for the electrolytic solution (that is, the liquid solvent and the electrolyte salt) includes, for example, polyacrylonitrile, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropropylene, and polytetrafluoroethylene. Ethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, Polystyrene or polycarbonate is mentioned. In particular, from the viewpoint of electrochemical stability, it is desirable to use a polymer compound having a structure of polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide.

  The amount of the polymer compound added to the electrolyte varies depending on the compatibility between the two, but it is usually preferable to add a polymer corresponding to 5% by mass to 50% by mass of the electrolyte. The content of the lithium salt is the same as in the case of the electrolytic solution. However, the term “solvent” used herein is not limited to a liquid solvent alone, but is a concept that broadly includes a solvent capable of dissociating an electrolyte salt and having ion conductivity. Therefore, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.

  This secondary battery can be manufactured, for example, as follows.

  First, for example, a positive electrode material is prepared by mixing a positive electrode material containing the composite oxide shown in Chemical formula 1 or the composite oxide shown in Chemical formula 2, a conductive agent, and a binder. Is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A and dried, and then compression molded by a roll press or the like to form the positive electrode mixture layer 21B, and the positive electrode 21 is manufactured.

  Next, for example, a negative electrode mixture is prepared by mixing a negative electrode material capable of inserting and extracting lithium and a binder, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to form a paste. Negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector 22A and dried, and then compression-molded by a roll press or the like to form the negative electrode mixture layer 22B, and the negative electrode 22 is manufactured.

  Next, the cathode lead 25 is attached to the cathode current collector 21A by welding or the like, and the anode lead 26 is attached to the anode current collector 22A by welding or the like. Thereafter, the positive electrode 21 and the negative electrode 22 are arranged opposite to each other with the separator 23 interposed therebetween, and then wound. The distal end of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the distal end of the negative electrode lead 26 is welded to the battery can 11. Then, the wound positive electrode 21 and negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and housed inside the battery can 11. After housing the positive electrode 21 and the negative electrode 22 inside the battery can 11, an electrolyte is injected into the inside of the battery can 11 and impregnated into the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the thermal resistance element 16 are fixed to the open end of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIG. 1 is completed.

  In this secondary battery, when charged, lithium ions are separated from the positive electrode mixture layer 21B, and lithium contained in the negative electrode mixture layer 22B can be inserted and removed first through the electrolyte impregnated in the separator 23. And the potential of the negative electrode 22 decreases. When charging is further continued, in the state where the open circuit voltage is lower than the overcharge voltage, the charge capacity exceeds the charge capacity capability of the negative electrode material capable of inserting and extracting lithium, and the charge capacity is increased on the surface of the negative electrode material capable of inserting and extracting lithium. Lithium metal begins to precipitate. Thereafter, lithium metal continues to be deposited on the negative electrode 22 until charging is completed. At this time, if ether having high resistance to reduction is used as the solvent, the reaction between the lithium metal and the electrolyte is suppressed. However, since ether has low oxidation resistance, in the case of a conventional positive electrode, oxidative decomposition of the electrolyte proceeds catalytically at active sites present on the surface of the positive electrode active material. By containing the composite oxide shown in 2, the structure of the positive electrode 21 is stable even at a high voltage, and the reactivity of active sites existing on the surface of the positive electrode active material is reduced. It operates stably even when used. After charging is completed, the potential of the negative electrode 22 is reduced by about 50 mV, for example, when graphite is used as the negative electrode active material, as compared with a lithium ion secondary battery in which lithium metal is not precipitated, and an alloy with lithium can be formed. When a simple element, alloy, or compound of a simple metal element or metalloid element is used, the voltage drops by about 30 mV. Therefore, as compared with a lithium ion secondary battery having the same battery voltage, the potential of the positive electrode 21 is also reduced, so that the reactivity of the positive electrode 21 is lower.

  Further, when the discharge is performed, first, the lithium metal precipitated on the negative electrode 22 is eluted as ions, and is occluded in the positive electrode mixture layer 21B via the electrolyte impregnated in the separator 23. When the discharge is further continued, lithium ions occluded in the negative electrode material capable of occluding and releasing lithium in the negative electrode mixture layer 22B are released and occluded in the positive electrode mixture layer 21B via the electrolyte. As a result, in this secondary battery, both characteristics of a conventional so-called lithium metal secondary battery and lithium ion secondary battery, that is, high energy density, high initial charge / discharge efficiency, and good charge / discharge cycle characteristics can be expected.

  As described above, in the present embodiment, since the composite oxide shown in Chemical Formula 1 or Chemical Formula 2 is included, the progress of the oxidation reaction of the electrolyte at a high voltage of 4 V or more can be suppressed. In addition, since lithium metal is deposited on the negative electrode 22, the potential of the positive electrode 21 can be lower than that of a lithium ion secondary battery having the same battery voltage, and the reactivity of the positive electrode 21 can be reduced. . Therefore, an ether that is strong in reduction but highly reactive to an oxidation reaction can be used, and an active reduction reaction of lithium can be suppressed. Further, a higher voltage operation of 4.2 V or more and 4.5 V or less can be performed. Therefore, the capacity, charge / discharge efficiency and charge / discharge cycle characteristics can be improved. As a result, it is possible to contribute to miniaturization and weight reduction of a portable electronic device represented by a mobile phone, a PDA or a notebook computer.

  Further, a specific embodiment of the present invention will be described in detail with reference to FIGS.

(Examples 1-1 to 1-8)
First, lithium carbonate (Li ₂ Co ₃ ) and cobalt carbonate (CoCO ₃ ) were mixed, and this mixture was fired in air at 900 ° C. for 5 hours to produce Li _x CoO ₂ . In Examples 1-1 to 1-8, the material amount ratio x of lithium was changed within a range from 1.05 to 1.32 as shown in Table 1. The composition of the obtained composite oxide was confirmed by ICP (Inductively Coupled Plasma) emission analysis.

  Next, this composite oxide was pulverized to obtain a powder having a cumulative 50% particle size of 15 μm obtained by a laser diffraction method. Thereafter, 95% by mass of the composite oxide powder and 5% by mass of lithium carbonate powder are mixed, and 94% by mass of the mixture, 3% by mass of Ketjen black as a conductive agent, and polyvinylidene fluoride as a binder are mixed. 3% by mass and dispersed in N-methyl-2-pyrrolidone to prepare a paste-like positive electrode mixture slurry. Next, a positive electrode current collector 21A made of a 20-μm-thick strip-shaped aluminum foil was prepared, and a positive electrode mixture slurry was uniformly applied to both surfaces of the positive electrode current collector 21A, dried, and then compression-molded to obtain a 113 μm-thick. The positive electrode mixture layer 21B was formed, and the positive electrode 21 was produced.

  Further, 90% by mass of an artificial graphite powder having an electrochemical equivalent of 320 mAh / g in the lithium storage reaction and 10% by mass of polyvinylidene fluoride as a binder are mixed and dispersed in N-methyl-2-pyrrolidone. Thus, a paste-like negative electrode mixture slurry was prepared. The electrochemical equivalent is defined as the maximum lithium storage amount when lithium metal does not precipitate on the graphite surface.

  Next, a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 15 μm was prepared, and a negative electrode mixture slurry was uniformly applied to both surfaces of the negative electrode current collector 22A, dried, and then compression molded to obtain a 120 μm thick negative electrode current collector. The negative electrode mixture layer 22B was formed, and the negative electrode 22 was produced.

  Next, a negative electrode 22, a separator 23, a positive electrode 21, and a separator 23 are laminated in this order via a separator 23 made of a stretched microporous polyethylene film having a thickness of 27 μm, and then wound many times to form a wound electrode body 20 having an outer diameter of 18 mm. Was prepared.

Next, the wound electrode body 20 was housed in a nickel-plated iron battery can 11. At this time, insulating plates 12 and 13 are provided on the upper and lower surfaces of the wound electrode body 20, an aluminum positive electrode lead 25 is led out from the positive electrode current collector 21A and welded to the safety valve mechanism 15, and a nickel negative electrode The lead 26 was led out from the negative electrode current collector 22A and welded to the battery can 11. After that, the electrolytic solution was injected into the battery can 11 by a reduced pressure method. As the electrolytic solution, a solution prepared by dissolving LiPF ₆ at a concentration of 1.5 mol / l in a solvent in which ethylene carbonate and tetrahydropyran or dimethyl carbonate were mixed in an equal volume was used.

  After injecting the electrolytic solution into the inside of the battery can 11, the battery cover 14 is caulked to the battery can 11 via a gasket 17 coated with asphalt on the surface, thereby fixing the safety valve mechanism 15 and the thermal resistance element 16, While maintaining the airtightness in the battery, a cylindrical secondary battery having a diameter of 18 mm and a height of 50 mm was produced.

Further, as Comparative Examples 1-1 to 1-4 with respect to Examples 1-1 to 1-8, LiCoO ₂ or Li _1.35 CoO ₂ was produced, and ethylene carbonate and tetrahydropyran or dimethyl carbonate were mixed in equal volumes. A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-8 except that a solvent was used.

  For the fabricated secondary batteries of Examples 1-1 to 1-8 and Comparative examples 1-1 to 1-4, a charge / discharge test was performed, and an initial charge capacity, an initial discharge capacity, an initial charge / discharge efficiency, and a discharge capacity retention ratio were obtained. I asked. Table 1 shows the obtained results. At that time, the charging was performed at a constant current of 600 mA until the charging voltage reached the value shown in Table 1, and then the charging was performed at the constant voltage until the total charging time reached 4 hours. On the other hand, the discharge was performed at a constant current of 600 mA until the discharge voltage reached 2.75 V. The initial charge / discharge efficiency was calculated as a ratio (%) of the initial discharge capacity to the initial charge capacity, and the discharge capacity retention rate was calculated as a ratio (%) of the initial discharge capacity to the discharge capacity at the 200th cycle.

The secondary batteries of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-4 were charged and discharged for one cycle under the above-described conditions and then completely charged again. And ⁷ Li nuclear magnetic resonance spectroscopy was used to determine whether or not lithium metal was deposited on the negative electrode mixture layer 22B. Furthermore, charge / discharge was performed for two cycles under the above-described conditions, and the battery that had been completely discharged was disassembled. Similarly, it was examined whether or not lithium metal had precipitated on the negative electrode mixture layer 22B.

  As a result, in all of the secondary batteries of Examples 1-1 to 1-8 and Comparative examples 1-1 to 1-4, in the fully charged state, the negative electrode mixture layer 22B contained lithium metal and external standard lithium chloride. A peak at 260 ppm was observed, and the presence of lithium metal was not observed in a completely discharged state. That is, it was confirmed that the capacity of the negative electrode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof.

  Further, as can be seen from Table 1, in Examples 1-1 to 1-8 in which the lithium mass ratio x was in the range of 1.00 <x <1.35, the discharge capacity, the initial charge / discharge efficiency, and the discharge High values were obtained for all of the capacity retention rates, and in particular, in Examples 1-6 and 1-7 in which the charging voltage was 4.5 V or more, the discharge capacity was able to be increased to 1600 mAh or more. Further, as can be seen from a comparison between Example 1-3 and Example 1-8, in Example 1-3 using tetrahydropyran, the discharge capacity and the first time were smaller than those in Example 1-8 not using tetrahydropyran. The charge / discharge efficiency and the discharge capacity retention rate could be increased.

  On the other hand, in Comparative Examples 1-1 to 1-4 in which the material amount ratio x of lithium was 1 or 1.35, both the initial charge / discharge efficiency and the discharge capacity retention ratio were low, and in particular, the charge voltage was 4 In Comparative Example 1-4 at .55 V, the discharge capacity retention ratio was zero at the 50th cycle, that is, the discharge capacity was zero at the 50th cycle, and the first discharge capacity was the same charge voltage as in Example 1. It was lower than -7. Also, as can be seen by comparing Comparative Example 1-1 with Comparative Example 1-2, Comparative Example 1-2 using tetrahydropyran has a higher discharge capacity and initial charge / discharge than Comparative Example 1-1 not using it. Both the efficiency and the discharge capacity retention ratio deteriorated.

That is, in Li _x CoO ₂ , it was found that the discharge capacity, charge / discharge efficiency and charge / discharge cycle characteristics could be improved if the lithium mass ratio x was within the range of 1 <x <1.35. In addition, it was found that operation was possible even at a high voltage, and higher capacity could be obtained.

  Further, as can be seen from Examples 1-1 to 1-5, the discharge capacity, the initial charge / discharge efficiency, and the discharge capacity retention rate increase as the material amount ratio x of lithium increases, and decrease after reaching the maximum value. There was a trend. That is, it was found that the lithium material amount ratio x was preferably in the range of 1.05 <x <1.20.

(Examples 2-1 to 2-4)
A secondary battery was fabricated in the same manner as in Example 1-3, except that the ethers shown in Table 2 were used instead of tetrahydropyran. In addition, as Comparative Examples 2-1 to 2-4 with respect to Examples 2-1 to 2-4, except that a composite oxide represented by the general formula LiCoO ₂ was prepared, the others were the same as in Examples 2-1 to 2-4. In the same manner as in Comparative Example No.-4, secondary batteries were manufactured.

  The secondary batteries of Examples 2-1 to 2-4 and Comparative examples 2-1 to 2-4 were also subjected to a charge / discharge test in the same manner as in Example 1-3, and the initial charge capacity, the initial discharge capacity, and the initial The charge / discharge efficiency was examined. The results are shown in Table 2 together with the results of Example 1-3 and Comparative Example 1-2. In addition, the presence or absence of lithium metal deposition in a fully charged state and a completely discharged state was examined. As a result, in Examples 2-1 to 2-4 and Comparative examples 2-1 to 2-4, the capacity of the negative electrode 22 was such that the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium were different. It was confirmed that it was included and represented by the sum.

  As can be seen from Table 2, according to Examples 2-1 to 2-4, as in Example 1-3, the discharge capacity and the initial charge / discharge efficiency were higher than those of Comparative Examples 2-1 to 2-4. High values were also obtained. That is, as the ether, tetrahydropyran, tetrahydrofuran, 1,3-dioxolan, 1,2-diethoxyethane or 1,3-dimethoxyethane can be used, and it can be confirmed that the properties can be improved by these ethers. Was.

(Examples 3-1 to 3-8)
Except that Li _x Ni _0.95 Al _0.05 O ₂ was prepared and a solvent in which ethylene carbonate and 1,3-dioxolan or dimethyl carbonate were mixed in an equal volume was used, the others were as in Examples 1-1 to 1-8. In the same manner as in the above, a secondary battery was produced. At that time, in Example 3-1 to 3-8, the material amount ratio x of lithium was changed in the range from 1.05 to 1.32 as shown in Table 3. Li _x Ni _0.95 Al _0.05 O ₂ is a mixture of lithium carbonate, nickel hydroxide (Ni (OH) ₂ ), cobalt hydroxide (Co (OH) ₂ ) and aluminum hydroxide (Al (OH) ₃ ). The mixture was fired at 900 ° C. for 5 hours in the air to produce the mixture. The composition of the obtained composite oxide was confirmed by ICP emission analysis in the same manner as in Examples 1-1 to 1-8.

As Comparative Examples 3-1 to 3-4 with respect to Examples 3-1 to 3-8, LiNi _0.95 Al _0.05 O ₂ or Li _1.35 Ni _0.95 Al _0.05 O ₂ was prepared, and ethylene carbonate and 1,3- A secondary battery was fabricated in the same manner as in Examples 3-1 to 3-8, except that a solvent obtained by mixing dioxolane or dimethyl carbonate in an equal volume was used.

  The secondary batteries of Examples 3-1 to 3-8 and Comparative examples 3-1 to 3-4 were also subjected to charge / discharge tests in the same manner as in Examples 1-1 to 1-8. The discharge capacity, the initial charge / discharge efficiency, and the discharge capacity maintenance rate were determined. Table 3 shows the results. At that time, charging was performed until the charging voltage reached the value shown in Table 3. In Comparative Example 3-4, the discharge capacity retention ratio became zero at the 40th cycle. In addition, the presence or absence of lithium metal deposition in a fully charged state and a completely discharged state was examined. As a result, in Examples 3-1 to 3-8 and Comparative examples 3-1 to 3-4, the capacity of the negative electrode 22 was such that the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium. It was confirmed that it was included and represented by the sum.

As can be seen from Table 3, according to Examples 3-1 to 3-8, results similar to those of Examples 1-1 to 1-8 were obtained. That is, in the composite oxide Li _x Ni _0.95 Al _0.05 O ₂ having another composition, if x is in the range of 1.00 <x <1.35, the discharge capacity, the charge / discharge efficiency and the charge / discharge cycle characteristics are obtained. It has been found that the capacitance can be improved, and the device can be operated even at a high voltage, so that a higher capacity can be obtained. In addition, it was found that the lithium content ratio x was preferably in the range of 1.05 <x <1.20.

(Examples 4-1 to 4-8)
Together to produce a _{Li x Ni 0.4 Co 0.2 Mn 0.4} O 2, ethylene carbonate, and dimethyl carbonate relative to mixed solvent mixture with an equal volume, are ether 2-methyltetrahydrofuran 5 wt% mixed solvent or ethylene carbonate A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-8, except that a mixed solvent in which dimethyl carbonate and dimethyl carbonate were mixed in an equal volume was used. At that time, the material ratio x of lithium was changed in the range of 1.05 to 1.32 in Examples 4-1 to 4-8 as shown in Table 4. Li _x Ni _0.4 Co _0.2 Mn _0.4 O ₂ is obtained by mixing lithium carbonate, nickel hydroxide, cobalt hydroxide, and manganese carbonate (MnCO ₃ ), and firing the mixture at 900 ° C. for 5 hours in the air. It was produced by the following. The composition of the obtained composite oxide was confirmed by ICP emission analysis in the same manner as in Examples 1-1 to 1-8.

In addition, as Comparative Examples 4-1 to 4-4 with respect to Examples 4-1 to 4-8, LiNi _0.4 Co _0.2 Mn _0.4 O ₂ or Li _1.35 Ni _0.4 Co _0.2 Mn _0.4 O ₂ were prepared, and ethylene carbonate and Except for using a solvent in which 5% by mass of 2-methyltetrahydrofuran as an ether is mixed or a mixed solvent in which ethylene carbonate and dimethyl carbonate are mixed in an equal volume, with respect to a mixed solvent obtained by mixing dimethyl carbonate in an equal volume. Other than that, the secondary battery was produced like Example 4-1 to 4-8.

  The secondary batteries of Examples 4-1 to 4-8 and Comparative examples 4-1 to 4-4 were also subjected to charge / discharge tests in the same manner as in Examples 1-1 to 1-8. The discharge capacity, the initial charge / discharge efficiency, and the discharge capacity maintenance rate were determined. Table 5 shows the results. At that time, charging was performed until the charging voltage reached the value shown in Table 5. In Comparative Example 4-4, the discharge capacity retention ratio became zero at the 40th cycle. In addition, the presence or absence of lithium metal deposition in a fully charged state and a completely discharged state was examined. As a result, in Examples 4-1 to 4-8 and Comparative examples 4-1 to 4-4, the capacity of the anode 22 was such that the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium were different. It was confirmed that it was included and represented by the sum.

As can be seen from Table 5, according to Examples 4-1 to 4-8, results similar to those of Examples 1-1 to 1-8 were obtained. That is, in the composite oxide Li _x Ni _0.4 Co _0.2 Mn _0.4 O ₂ having another composition, if x is in the range of 1.00 <x <1.35, the discharge capacity, charge / discharge efficiency and charge / discharge cycle It has been found that the characteristics can be improved, the device can be operated even at a high voltage, and a higher capacity can be obtained. In addition, it was found that the lithium content ratio x was preferably in the range of 1.05 <x <1.20.

(Examples 5-1 to 5-4)
A secondary battery was fabricated in the same manner as in Example 4-3, except that a lithium-nickel-cobalt-manganese composite oxide was fabricated. At that time, the mass ratio x of lithium was 1.15, and the mass ratio of nickel, cobalt and manganese was changed as shown in Table 6. The lithium-nickel-cobalt-manganese composite oxide was prepared by mixing lithium carbonate, nickel hydroxide, cobalt hydroxide, and manganese carbonate, and firing the mixture at 900 ° C. for 5 hours in air. . The composition of the obtained composite oxide was confirmed by ICP emission analysis in the same manner as in Examples 1-1 to 1-8.

  As Comparative Examples 5-1 to 5-4 with respect to Examples 5-1 to 5-4, the material ratio of lithium was set to 1.00, and the material ratios of nickel, cobalt, and manganese were as shown in Table 6. A secondary battery was fabricated in the same manner as in Examples 5-1 to 5-4, except that a lithium-nickel-cobalt-manganese composite oxide was prepared.

  The secondary batteries of Examples 5-1 to 5-4 and Comparative examples 5-1 to 5-4 were also subjected to a charge / discharge test in the same manner as in Example 4-3, and the initial charge capacity, the initial discharge capacity, and the initial The charge / discharge efficiency was determined. The results are shown in Table 6 together with the results of Example 4-3 and Comparative Example 4-2. In addition, the presence or absence of lithium metal deposition in a fully charged state and a completely discharged state was examined. As a result, in Examples 5-1 to 5-4 and Comparative examples 5-1 to 5-4, the capacity of the negative electrode 22 was such that the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium were different. It was confirmed that it was included and represented by the sum.

  As can be seen from Table 6, according to Examples 5-1 to 5-4, as in Example 4-3, the compositions other than the material amount ratio x of lithium were the same for the discharge capacity and the initial charge / discharge efficiency. Values higher than certain comparative examples 5-1 to 5-4 were obtained. That is, when the material ratio x of lithium is in the range of 1.00 <x <1.35, the discharge capacity and charge / discharge efficiency can be improved even in the lithium-nickel-cobalt-manganese composite oxide. I understood.

(Example 6-1)
A secondary battery was manufactured in the same manner as in Example 4-1 except that Li _1.15 Mn ₂ O _{4 in} which the value of the mass ratio c of lithium was 1.15 was manufactured. At that time, Li _1.15 Mn ₂ O ₄ was produced by mixing lithium carbonate and manganese carbonate and calcining the mixture at 900 ° C. for 5 hours in the air. The composition of the obtained composite oxide was confirmed by ICP emission analysis in the same manner as in Examples 1-1 to 1-8.

A secondary battery was fabricated in the same manner as in Example 6-1 except that LiMn ₂ O ₄ was fabricated as Comparative Example 6-1 with respect to Example 6-1.

  The secondary batteries of Example 6-1 and Comparative Example 6-1 were also subjected to a charge / discharge test in the same manner as in Examples 1-1 to 1-5, and the initial charge capacity, initial discharge capacity, and initial charge / discharge efficiency were determined. I asked. Table 7 shows the results. In addition, the presence or absence of lithium metal deposition in a fully charged state and a completely discharged state was examined. As a result, in Example 6-1 and Comparative Example 6-1, the capacity of the negative electrode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. Was confirmed.

As can be seen from Table 7, according to Example 6-1, the same results as in Examples 1-1 to 1-5 were obtained for the discharge capacity and the initial charge / discharge efficiency. In other words, it was found that, even in Li _1.15 Mn ₂ O ₄ , the discharge capacity and the charge / discharge efficiency can be improved if the lithium material amount ratio c is in the range of 1.00 <c <1.35. .

(Examples 7-1 to 7-8)
Except for producing Li _c Mn _1.8 Mg _0.1 Al _0.1 O ₄ and using a solvent in which ethylene carbonate and 1,3-dioxolan or dimethyl carbonate were mixed in equal volumes, the others were as described in Examples 1-1 to 1-1. A secondary battery was fabricated in the same manner as in -8. At that time, the material amount ratio c of lithium was changed in the range of 1.05 to 1.32 in Examples 7-1 to 7-8 as shown in Table 8. Li _c Mn _1.8 Mg _0.1 Al _0.1 O ₄ was prepared by mixing lithium carbonate, manganese carbonate, magnesium hydroxide, and aluminum hydroxide, and firing this mixture at 900 ° C. for 5 hours in air. . The composition of the obtained composite oxide was confirmed by ICP emission analysis in the same manner as in Examples 1-1 to 1-8.

As a comparative example 7-1 to 7-4 relative to Examples 7-1 to 7-8, with making LiMn _1.8 Mg _0.1 Al _0.1 O ₄ or _{Li 1.35 Mn 1.8 Mg 0.1 Al 0.1} O 4, and ethylene carbonate A secondary battery was fabricated in the same manner as in Examples 7-1 to 7-8, except that a solvent in which 1,3-dioxolane or dimethyl carbonate was mixed in an equal volume was used.

  The secondary batteries of Examples 7-1 to 7-8 and Comparative examples 7-1 to 7-4 were also subjected to charge / discharge tests in the same manner as in Examples 1-1 to 1-8. The discharge capacity, the initial charge / discharge efficiency, and the discharge capacity maintenance rate were determined. Table 8 shows the results. At that time, charging was performed until the charging voltage reached the value shown in Table 8. In Comparative Example 7-4, the discharge capacity retention ratio became zero at the 50th cycle. In addition, the presence or absence of lithium metal deposition in a fully charged state and a completely discharged state was examined. As a result, in Examples 7-1 to 7-8 and Comparative examples 7-1 to 7-4, the capacity of the negative electrode 22 was such that the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium. It was confirmed that it was included and represented by the sum.

As can be seen from Table 8, according to Examples 7-1 to 7-8, results similar to those of Examples 1-1 to 1-8 were obtained. That is, also in Li _c Mn _1.8 Mg _0.1 Al _0.1 O ₄ , if the mass ratio c of lithium is in the range of 1.00 <c <1.35, the discharge capacity, charge / discharge efficiency, and charge / discharge cycle characteristics are improved. It has been found that it is possible to improve the capacitance and to operate at a high voltage, thereby obtaining a higher capacity. Further, it was found that the lithium material amount ratio c was preferably in the range of 1.05 <c <1.20.

  In the above examples, the composite oxide and ether represented by Chemical Formula 1 or Chemical Formula 2 have been described with specific examples. However, other composite oxides and other ethers represented by Chemical Formula 1 or Chemical Formula 2 may be used. A similar result can be obtained even when used.

  As described above, the present invention has been described with reference to the embodiment and the example. However, the present invention is not limited to the above-described embodiment and example, and can be variously modified. For example, in the above-described embodiments and examples, the positive electrode of the present invention indicates that the capacity of the negative electrode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. Although the description has been given of the case where the present invention is applied to a battery, the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium, or a so-called lithium-ion secondary battery, The present invention can be applied to a so-called lithium metal secondary battery as shown.

  Further, in the above embodiments and examples, the case where a gel electrolyte which is one kind of the electrolytic solution or the solid electrolyte is used is described. However, another electrolyte may be used. As other electrolytes, for example, a polymer solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, an inorganic solid electrolyte made of ion-conductive ceramics, ion-conductive glass or ionic crystal, or the like. Or a mixture of these inorganic solid electrolytes and a gel electrolyte or a polymer solid electrolyte.

  Furthermore, in the above embodiments and examples, a cylindrical secondary battery having a wound structure was described.However, the present invention provides an elliptical or polygonal secondary battery having a wound structure, or a positive electrode and a positive electrode. The same can be applied to a secondary battery having a structure in which the negative electrode is folded or stacked. Further, the present invention can be applied to a so-called coin-type, button-type or square-type secondary battery. Further, the present invention is not limited to a secondary battery, and can be applied to a primary battery.

1 is a cross-sectional view illustrating a configuration of a secondary battery according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating an enlarged part of a wound electrode body in the secondary battery illustrated in FIG. 1.

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulating board, 14 ... Battery lid, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20 ... Wound electrode body, 21 ... Positive electrode, 21A ... Positive electrode current collector, 21B ... Positive electrode mixture layer, 22 ... Negative electrode, 22A ... Negative electrode current collector, 22B ... Negative electrode mixture layer, 23 ... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead

Claims (16)

The capacity includes a capacity component due to insertion and extraction of lithium (Li) and a capacity component due to precipitation and dissolution of lithium, and is used together with a negative electrode represented by the sum of:
Formula Li _x M1 in _{1-y M2 y O 2-} z ( wherein, M1 is at least one of the stands, M2 atomic number 11 or more metal elements other than M1 of cobalt (Co) and nickel (Ni) X, y and z are within the range of 1.00 <x <1.35, 0 ≦ y <1.0, −0.1 ≦ z ≦ 0.1 A composite oxide represented by the following formula:   2. The positive electrode according to claim 1, wherein a mass ratio x of lithium in the composite oxide is 1.05 <x <1.20. 3.   The positive electrode according to claim 1, wherein the composite oxide contains cobalt, nickel, and manganese (Mn). The capacity includes a capacity component due to insertion and extraction of lithium (Li) and a capacity component due to precipitation and dissolution of lithium, and is used together with a negative electrode represented by the sum of:
Formula _{Li c Mn 2-d M3 d} O 4-e ( wherein, M3 represents at least one selected from the group consisting of atomic number 11 or more metal elements other than manganese (Mn), c, d and e Is a value within the range of 1.00 <c <1.35, 0 ≦ d <0.5, and −0.2 ≦ e ≦ 0.2.) Characteristic positive electrode.   5. The positive electrode according to claim 4, wherein a mass ratio c of lithium in the composite oxide satisfies 1.05 <c <1.20. A battery provided with an electrolyte together with a positive electrode and a negative electrode, wherein the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium (Li) and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. ,
The positive electrode, the general formula Li _x M1 in _{1-y M2 y O 2-} z ( wherein, M1 represents at least one of cobalt (Co) and nickel (Ni), M2 is M1 other than atomic number 11 or more X, y and z represent 1.00 <x <1.35, 0 ≦ y <1.0, −0.1 ≦ z ≦ 0.1 A battery comprising a composite oxide represented by the following formula:   The battery according to claim 6, wherein a mass ratio x of lithium in the composite oxide is 1.05 <x <1.20.   The battery according to claim 6, wherein the composite oxide contains cobalt, nickel, and manganese (Mn).   The battery according to claim 6, wherein a charging voltage is in a range of 4.2V or more and 4.5V or less.   The battery according to claim 6, wherein the electrolyte includes an ether.   The electrolyte includes at least one selected from the group consisting of tetrahydropyran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 1,2-diethoxyethane, 1,3-dimethoxyethane, and derivatives thereof. The battery according to claim 6, wherein: A battery provided with an electrolyte together with a positive electrode and a negative electrode, wherein the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium (Li) and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. ,
The positive electrode, the general formula _{Li c Mn 2-d M3 d} O 4-e ( wherein, M3 represents at least one selected from the group consisting of atomic number 11 or more metal elements other than manganese (Mn), c , D and e are values in the range of 1.00 <c <1.35, 0 ≦ d <0.5, and −0.2 ≦ e ≦ 0.2.) A battery comprising:   13. The battery according to claim 12, wherein the material ratio c of lithium in the composite oxide satisfies 1.05 <c <1.20.   13. The battery according to claim 12, wherein a charging voltage is in a range of 4.2 V or more and 4.5 V or less.   The battery according to claim 12, wherein the electrolyte includes an ether. The electrolyte includes at least one selected from the group consisting of tetrahydropyran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 1,2-diethoxyethane, 1,3-dimethoxyethane, and derivatives thereof. The battery according to claim 12, wherein:

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