JP2004363076A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery of which energy density is high and charge and discharge characteristics are excellent. <P>SOLUTION: A positive electrode 21 and a negative electrode 22 are wound via a separator 23 which is impregnated with an electrolyte. Li metal deposits on the negative electrode 22 during the charging, capacity of the negative electrode 22 includes capacitive component by absorption or coming out of Li and capacitive component by the deposition or dissolution of Li, and the capacity of the negative electrode 22 is expressed by sum of them. By solid<SP>7</SP>Li multinuclide nuclear magnetic resonance spectral analysis of the negative electrode 22 using LiCL as the standard substance in completely charged state and completely discharged state, a resonance line Ri which is attributed to Li ions in a region from -10 ppm to 200 ppm in relation to resonance lines Rs of the standard substance is obtained, wherein a ratio of an area of the resonance line Ri attributed to the Li ions to an area of the resonance line Rs of the standard substance in the completely discharged state is 3% or more of a ratio of an area of the resonance line Ri attributed to the Li ions to an area of the resonance line Rs of the standard substance in the completely charged state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to 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 occlusion and desorption of the light metal and a capacity component due to precipitation and dissolution of the light metal, and is represented by the sum thereof.

  In recent years, portable electronic devices represented by mobile phones, PDAs (Personal Digital Assistants), camcorders, and notebook computers have been remarkably developed. There is a strong demand for higher capacity and higher energy density of batteries as driving power supplies, particularly secondary batteries.

  As a secondary battery capable of obtaining a high energy density, for example, there is a lithium ion secondary battery in which a material such as a carbon material capable of inserting and extracting lithium (Li) is used for a negative electrode. 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, the storage amount of graphite, which is currently the most efficient material for storing and releasing lithium ions, is theoretically limited to 372 mAh in terms of electricity per gram. It is reaching the limit.

As a secondary battery capable of obtaining a high energy density, a lithium metal secondary battery using lithium metal for a negative electrode and utilizing precipitation and dissolution of lithium metal for a negative electrode reaction is known. Since lithium metal has a large theoretical electrochemical equivalent of 2054 mAh / cm ³ and an energy density equivalent to 2.5 times that of graphite used in lithium ion secondary batteries, lithium metal secondary batteries use lithium ion secondary batteries. It has the potential to achieve higher energy density than secondary batteries.

  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, a lithium metal secondary battery has a large deterioration in discharge capacity when charging and discharging are repeated, and its practical application is very difficult at present. This capacity deterioration is based on the fact that lithium metal secondary batteries use the deposition and dissolution reaction of lithium metal at the negative electrode.The lithium metal deposited falls off the electrode or reacts with the electrolyte during charging and discharging. This is considered to be caused by deactivation due to this.

Therefore, the present applicant has newly developed a secondary battery 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 metal, and is represented by the sum of the two (for example, And Patent Document 1.). In this technology, a carbon material capable of inserting and extracting lithium ions is used for a negative electrode, and lithium metal 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 Japanese Patent No. 3287376 Japanese Patent No. 3291750 JP-A-8-64207 JP-A-9-7598 Japanese Patent No. 3106129 Japanese Patent No. 3363959 JP-A-10-199527 JP-A-10-208741 JP 2001-6667A JP 2001-6677 A

  However, since this secondary battery also utilizes the precipitation and dissolution reaction of lithium, like the lithium metal secondary battery, it is extremely difficult to completely prevent the lithium metal from dropping from the electrode and the reaction with the electrolyte, There is a problem that the charge / discharge cycle life is short. In addition, in this secondary battery, the initial charge / discharge efficiency of the positive electrode is higher than the initial charge / discharge efficiency of the negative electrode, and the discharge capacity is regulated by the initial charge / discharge efficiency of the negative electrode. However, there is a problem that a sufficient energy density cannot be obtained.

  In other words, the above problem can be solved by making a capacity stock by supplementing the inside of the battery, specifically, the positive electrode, the negative electrode or the electrolyte with more lithium than can contribute to charging and discharging, It is considered that the characteristics can be further improved by optimizing the amount of lithium. The amount of lithium can be determined by nuclear magnetic resonance spectroscopy (NMR). Conventionally, lithium has been supplemented in a lithium ion secondary battery (for example, see Patent Literatures 2 and 3), or an anode material has been defined by NMR (for example, Patent Literatures 4 to 4). 11).

  However, it is difficult to make a capacity stock with a lithium ion secondary battery. This is because charging and discharging are basically performed in a system in which lithium metal does not precipitate, so if excessive lithium is introduced and lithium metal precipitates, the charge / discharge cycle characteristics deteriorate or the safety decreases. is there. Even in Patent Document 4 in which lithium is occluded in the negative electrode, the amount of occluded lithium is sufficient to suppress a decrease in irreversible capacity at the time of initial charging of the negative electrode or to suppress a rise in potential of the negative electrode during overdischarge. As described above, the introduction of lithium, which has been conventionally performed in a lithium ion secondary battery, is not intended to improve charge / discharge cycle characteristics.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a battery capable of obtaining a high energy density and having excellent charge / discharge cycle characteristics.

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 occlusion and desorption of the light metal and a capacity component due to precipitation and dissolution of the light metal, and is represented by the sum thereof. In the fully charged state and the completely discharged state, the negative electrode was determined to be -10 ppm with respect to the resonance line of the reference material by solid-state ⁷ Li multinuclear nuclear magnetic resonance spectroscopy using lithium chloride (LiCl) as the reference material. Another resonance line is obtained in the range of 200 ppm, and the area ratio of the other resonance line to the resonance line of the reference material in the fully discharged state is equal to the area ratio of the other resonance line to the resonance line of the reference material in the fully charged state. 3% or more.

  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 occlusion and desorption of light metal and a capacity component due to deposition and dissolution of light metal, and is represented by the sum thereof. The negative electrode has a light metal in a metal state at the time of assembly.

  A third 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 occlusion and desorption of light metal, and a capacity component due to deposition and dissolution of light metal, and is represented by the sum thereof. In the negative electrode, an ionic light metal is occluded during assembly.

  A fourth 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 occlusion and desorption of light metal, and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof. Wherein the electrolyte contains a light metal salt that is oxidatively decomposed at the positive electrode.

  A fifth 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 detachment of light metal and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof. The battery has a substance that irreversibly releases light metal during assembly in the battery.

  A sixth 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 occlusion and desorption of light metal, and a capacity component due to deposition and dissolution of light metal, and is represented by the sum thereof. In this case, the capacity of the negative electrode at the time of the first full charge is larger than the theoretical capacity of the positive electrode at the time of assembly.

According to the first battery of the present invention, in a fully charged state and a completely discharged state, a solid ⁷ Li multi-nuclide nuclear magnetic resonance spectroscopy using lithium chloride as a reference substance has -10 ppm to the resonance line of the reference substance. Another resonance line is obtained in the range of 200 ppm, and the area ratio of the other resonance line to the resonance line of the reference material in the fully discharged state is 3 times the area ratio of the other resonance line to the resonance line of the reference material in the fully charged state. % Of the negative electrode is used, and according to the second battery of the present invention, the negative electrode has a light metal in a metal state at the time of assembling. For example, since the light metal in the ionic state is stored in the negative electrode during assembly, in addition, according to the fourth battery of the present invention, the electrolyte contains the light metal salt which is oxidatively decomposed at the positive electrode. In addition, according to the fifth battery of the present invention, since the positive electrode has a substance that irreversibly releases a light metal at the time of assembly, furthermore, according to the sixth battery of the present invention, the first complete battery Since the capacity of the negative electrode at the time of charging is made larger than the theoretical capacity of the positive electrode at the time of assembly, the initial charge / discharge efficiency of the negative electrode material capable of inserting and extracting lithium is improved, and the discharge capacity is improved. Can be. Further, even if the light metal precipitated during charging is deactivated by dropping from the negative electrode or reacting with the electrolyte, the loss of capacity due to the deactivation is supplemented, and the charge / discharge cycle characteristics can be improved. Furthermore, even if overdischarge occurs, the increase in the potential of the negative electrode is suppressed, so that the dissolution of the negative electrode current collector can also be suppressed. That is, the overdischarge resistance can be improved.

  In particular, in the first battery of the present invention, the positive electrode has a positive electrode mixture layer capable of inserting and extracting light metal, and the ratio of the thickness A of the positive electrode mixture layer to the thickness B of the negative electrode mixture layer ( When A / B) is set to 0.92 or more, in the second battery of the present invention, the capacity of the light metal that the negative electrode has at the time of assembly is 1 to the capacity of the negative electrode due to the light metal occlusion and release. %, The capacity of the ionic light metal occluded in the negative electrode during assembly in the third battery of the present invention is reduced to the capacity of the negative electrode due to occlusion and desorption of the light metal in the negative electrode. In addition, when the content is in the range of 1% or more and 100% or less, in the fourth battery of the present invention, the material amount of the light metal salt is changed so that the amount of light metal corresponding to the capacity of the negative electrode by absorbing and releasing the light metal. Less than substance amount If so, in the fifth battery of the present invention, the capacity of the light metal that the positive electrode has at the time of assembly is in the range of 1% or more and 100% or less with respect to the capacity of the negative electrode due to occlusion and release of the light metal. By doing so, more excellent charge / discharge cycle characteristics can be obtained.

  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. A wound electrode in which a band-shaped positive electrode 21 and a band-shaped negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. It has a body 20. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), 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 positive electrode current collector 21A having a pair of opposing surfaces, and a positive electrode mixture layer 21B provided on both surfaces or one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode mixture layer 21B includes, for example, one or more positive electrode materials capable of inserting and extracting lithium as a light metal as a positive electrode active material. That is, the positive electrode mixture layer 21B can occlude and release lithium.

The positive electrode mixture layer 21B preferably contains, for example, lithium in an amount equivalent to a charge / discharge capacity of 250 mAh or more per gram of a negative electrode active material described below in a steady state (for example, after repeating charge / discharge about 5 times), and 350 mAh. It is more preferable to include lithium equivalent to the above charge / discharge capacity. Therefore, as the positive electrode material capable of inserting and extracting lithium, for example, a composite oxide containing lithium and a transition metal element, an intercalation compound containing lithium, and the like are preferable. Among them, a composite oxide containing at least one of cobalt (Co), nickel, manganese (Mn), iron, vanadium (V) and titanium (Ti) as the transition metal element is more preferable. Further, a composite oxide in which part of the transition metal element is replaced by another element such as aluminum is also preferable. As such a composite oxide, for example, the chemical formula Li _x1 MIO ₂ (MI represents one or more kinds of transition metals, and the value of x1 varies depending on the charge / discharge state of the battery, and is usually 0.05 ≦ x1 ≦ 1 .10) or Li _x2 MIIPO ₄ (MII represents one or more transition metals, etc., and the value of x2 varies depending on the charge / discharge state of the battery, and is usually 0.05 ≦ x2 ≦ 1 .10). More specifically, there are lithium cobaltate, lithium nickelate, lithium cobalt nickelate, lithium manganate having a spinel type crystal structure, and lithium iron phosphate having an olivine type crystal structure.

  Such a positive electrode material is prepared, for example, by mixing lithium carbonate, nitrate, oxide or hydroxide with a transition metal carbonate, nitrate, oxide or hydroxide so as to have a desired composition. Then, after pulverization, it is prepared by firing in an oxygen atmosphere at a temperature in the range of 600C to 1000C.

  The positive electrode mixture layer 21B also contains, for example, a conductive agent, and may further contain a binder as needed. 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.

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

  The negative electrode mixture layer 22B contains, for example, one or more of negative electrode materials capable of inserting and extracting lithium as a light metal as a negative electrode active material. It may contain the same binder as 21B. That is, the negative electrode mixture layer 22B can occlude and release lithium.

  In the present specification, the terms “occlusion and desorption of light metal” means that light metal ions are electrochemically stored and desorbed 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 negative electrode material capable of inserting and extracting lithium include a carbon material 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 to perform calcination, and at the same time, it is 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 heat-treating an organic material at about 1200 ° C. and pulverizing and classifying. 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, an alloy, and a compound of a metal element or a metalloid 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.

Examples of such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi), and cadmium. (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf). Can be 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, Mg2 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.

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 active materials, it is particularly preferable to use one having an active lithium ion occlusion reaction, and particularly preferable to use one having a charge / discharge potential relatively close to lithium metal.

  In this secondary battery, lithium metal starts to precipitate on the negative electrode 22 at the time when the open circuit voltage (that is, the battery voltage) is lower than the overcharge voltage in the charging process. 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 deposition and dissolution of lithium metal. And represented by the sum of Accordingly, 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 lithium metal. It is a base material for precipitation.

  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 secondary battery”. Refers to a voltage higher than the open circuit voltage of a "fully charged" battery as defined and defined in the "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, for example, this secondary battery is fully charged when the open circuit voltage is 4.2 V, and can occlude and release 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 possible anode materials.

  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 the same as 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 the negative electrode material is capable of inserting and extracting lithium. It is considered that the following advantages are brought about by depositing lithium metal.

  First, in the conventional lithium metal secondary battery, it is difficult to uniformly deposit lithium metal, which causes deterioration of charge / discharge cycle characteristics. However, a negative electrode capable of inserting and extracting lithium is used. Since the material generally has a large surface area, lithium metal can be uniformly deposited in this secondary battery. Second, in the conventional lithium metal secondary battery, the volume change accompanying precipitation and dissolution of lithium metal is large, which also causes deterioration of the charge / discharge cycle characteristics. Lithium metal also precipitates in gaps between the particles of the negative electrode material that can be detached, 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, a negative electrode material capable of inserting and extracting lithium is used. Since the insertion and extraction of lithium also contribute 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 determined by inserting and extracting lithium. It is preferable that the charge capacity is 0.05 times or more and 3.0 times or less of the charge capacity capacity of the negative electrode material capable of performing the above. 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 the 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.

Further, in this secondary battery, lithium ions are occluded in the negative electrode mixture layer 22B before the first charge or before lithium ions are released from the positive electrode material capable of inserting and extracting lithium at the time of the initial charge. Thus, the capacity of the negative electrode 22 at the time of the first complete charge is larger than the theoretical capacity of the positive electrode 21 at the time of assembly. Thus, even in a completely discharged state, lithium ions that cannot be completely absorbed by the positive electrode 21 exist in the negative electrode mixture layer 22B. Thus, in the fully discharged state, the negative electrode 22, with respect to the anode material capable of specifically of inserting and extracting lithium, for example lithium chloride used as a reference substance, a solid ⁷ Li multinuclear NMR spectroscopy Then, a resonance line Ri belonging to lithium ions is obtained in the range of -10 ppm to 200 ppm with respect to the resonance line Rs of the reference substance shown in FIG. 3 as shown in FIG. On the other hand, in the fully charged state, as shown in FIG. 5, the resonance line Ri belonging to lithium ions in the range of −10 ppm to 200 ppm and the lithium metal in the range of 250 ppm to 280 ppm with respect to the resonance line Rs of the reference material. The assigned resonance line Rm is obtained. On the other hand, before the first charge, or when lithium ions are not occluded in the negative electrode mixture layer 22B before lithium ions are released from the positive electrode material capable of inserting and extracting lithium during the initial charge, In the complete discharge state, as shown in FIG. 6, a resonance line Ri belonging to lithium ions and a resonance line Rm belonging to lithium metal are obtained with respect to the resonance line Rs of the reference material, but in the complete discharge state, As shown in FIG. 7, the resonance line Ri attributed to lithium ions is hardly obtained. The completely discharged state is, for example, a state defined and described in “Guide to Transport of Lithium Batteries and Lithium Ion Batteries” issued by the Japan Storage Battery Association (Battery Manufacturers Association), or from the negative electrode 22 to the positive electrode 21. Corresponds to the case where supply of the electrode reactive species (here, lithium ions) is stopped. In this secondary battery, for example, when the closed-circuit voltage reaches 2.75 V, it can be regarded as “completely discharged”.

  As described above, the lithium ions (hereinafter referred to as “stock”) stored in the negative electrode mixture layer 22B before the first charging or before the lithium ions are released from the positive electrode material capable of storing and releasing lithium during the first charging. In this secondary battery, the initial charge / discharge efficiency of the negative electrode material capable of inserting and extracting lithium is improved, and the discharge capacity can be improved. Even if the deposited lithium metal does not contribute to the charge / discharge reaction due to dropping from the negative electrode 22 or reacting with the electrolytic solution, the loss of capacity of the lithium metal that does not contribute to the charge / discharge is replenished by the stock lithium. Until stock lithium is consumed, the discharge capacity is regulated by the charge and discharge efficiency of the positive electrode 21. Therefore, it is possible to improve the charge / discharge cycle characteristics as compared with a conventional secondary battery in which the discharge capacity is regulated by the charge / discharge efficiency of the negative electrode. Furthermore, since the potential rise of the negative electrode 22 is suppressed even if overdischarge occurs, the dissolution of the negative electrode current collector 22A can be suppressed.

  In particular, the area ratio of the resonance line Ri belonging to lithium ions to the resonance line Rs of the reference substance in the completely discharged state is the resonance line Ri belonging to lithium ions to the resonance line Rs of the reference substance in the fully charged state immediately before discharging. If the area ratio is 3% or more, the deterioration of the discharge capacity due to the charge / discharge cycle is significantly suppressed. For example, when lithium chloride is used as the internal standard material, a spectrum as shown in FIG. 8 is obtained in a completely discharged state, and a spectrum as shown in FIG. 9 is obtained in a fully charged state. In this case, , (Area Ai of resonance line Ri belonging to lithium ions in fully discharged state) / (area As of resonance line Rs of reference substance in completely discharged state) ≧ (area of resonance line Ri belonging to lithium ions in fully charged state) Ai) / (Area As of resonance line Rs of reference material in fully charged state) × 0.03 is preferred.

  When assembled, such a battery has, for example, one of the following configurations.

  First, a light metal layer in the metal state made of lithium metal is provided on the surface of the negative electrode mixture layer 22B. In this case, at least a part of the light metal layer is spontaneously dissolved using the potential difference at the contact interface with the negative electrode mixture layer 22B as a driving force to become stock lithium. The light metal layer may be formed, for example, by depositing lithium metal on the surface of the negative electrode mixture layer 22B by a dry film forming method such as a sputtering method, a vacuum evaporation method, a laser ablation method, or an ion plating method. Alternatively, it may be constituted by a lithium metal foil attached to the negative electrode mixture layer 22B by pressure bonding or other means. However, a film formed by a dry film formation method is preferable because thinning and flattening are achieved, lithium ion occlusion can proceed uniformly, and remaining is suppressed. The shape of the light metal layer is not particularly limited, and may be, for example, patterned.

  Second, stock lithium is occluded in the negative electrode mixture layer 22B by electrochemical treatment. For example, by applying a current to the negative electrode 22 having the light metal layer formed therein in an electrolytic bath or by bringing the light metal layer into contact with the negative electrode mixture layer 22B, the stock lithium is occluded in the negative electrode mixture layer 22B.

  Third, the negative electrode mixture layer 22B contains lithium metal or a lithium compound in addition to the negative electrode active material and the binder. In this case, the lithium metal or lithium compound spontaneously dissolves to become stock lithium.

Fourth, stock lithium is occluded in the negative electrode mixture layer 22B by a chemical treatment. For example, the negative electrode mixture layer 22B is reacted with an organic lithium such as n-butyl lithium or a lithium halide such as lithium iodide before assembling the battery, or in a solvent such as Co (C ₂ H ₄ ) (PCH ₃ ). Stock lithium is occluded in the negative electrode mixture layer 22B by, for example, reacting with lithium metal using a cobalt complex salt of the above as a catalyst.

  Fifth, stock lithium is occluded in the anode mixture layer 22B in the form of a complex of an aromatic hydrocarbon such as naphthalene, phenanthrene or anthracene and lithium metal. The complex is dispersed in an organic solvent such as dimethoxyethane, dimethylsulfoxide or hexamethylphosphiramide, tetrahydrofuran, dioxolan, 2,5-dimethyltetrahydrofuran which can be solvated with metal ions, and the negative electrode is dispersed in the organic solvent. The negative electrode mixture layer 22 may be occluded by immersing the mixture layer 22B.

Sixth, the electrolyte contains, for example, a lithium salt that is oxidatively decomposed at the positive electrode 21 (hereinafter, referred to as an oxidatively decomposed lithium salt). In this case, since the oxidation potential of the oxidized lithium salt is lower than the potential at which lithium ions are released from the positive electrode 21, the oxidized lithium salt is prioritized before the lithium ions are released from the positive electrode 21 during the first charge. Oxidized and decomposed by the positive electrode 21 to generate lithium ions and carbon dioxide (CO ₂ ). The generated lithium ions are reduced by the negative electrode 22 and stored as stock lithium in the negative electrode mixture layer 22B. Examples of the oxidatively decomposed lithium salt include lithium oxalate, lithium formate, lithium acetate and lithium propionate.

  Seventh, a material that irreversibly releases lithium (hereinafter, referred to as a lithium releasing material), for example, lithium metal, is provided in a portion of the battery where the electrolyte contacts. For example, the positive electrode 21 may include a lithium releasing substance, the lithium releasing substance may be bonded to the surface of the center pin 24, and the lithium releasing substance may be bonded to a dead space in the battery where the electrolyte contacts. It may be. When the positive electrode 21 contains a lithium releasing substance, the light metal layer may be formed on the surface of the positive electrode mixture layer 21B by the above-mentioned dry film formation method or bonded as a foil to form a light metal layer. In addition to the substance, the binder, and the conductive agent, the positive electrode mixture layer 21B may be contained in a powdery state. In these cases, for example, before lithium ions are detached from the positive electrode 21, the lithium releasing substance is oxidized to release lithium ions. The released lithium ions are reduced by the negative electrode 22 and occluded in the negative electrode mixture layer 22B as stock lithium.

  Eighth, a positive electrode active material containing nickel such as lithium nickel oxide is used for the positive electrode, and the initial charge / discharge efficiency of the positive electrode 21 is smaller than the initial charge / discharge efficiency of the negative electrode 22. In this case, as much as the initial charge / discharge efficiency of the negative electrode 22 is larger than the initial charge / discharge efficiency of the positive electrode 21, lithium ions remain as stock lithium in the negative electrode 22.

  In the first to fifth cases, the capacity of the negative electrode 22 at the time of assembling of the negative electrode 22 is determined by the capacity of inserting and extracting lithium metal, more specifically, the capacity of the negative electrode material capable of inserting and extracting lithium. Is preferably in the range of 1% to 100%, more preferably 10% to 50%. In the sixth case, the amount of the oxidatively decomposed lithium salt is preferably equal to or less than the amount of lithium corresponding to the capacity of the anode 22 due to insertion and extraction of lithium. For example, the capacity of lithium contained in the lithium salt is preferably in the range of 1% or more and 100% or less, more preferably 10% or more and 50% or less, with respect to the capacity due to insertion and extraction of lithium. Further, in the seventh case, the capacity of lithium by the lithium releasing material at the time of assembly is preferably in the range of 1% or more and 100% or less, and more preferably 10% or more and 50% or less of the capacity of the negative electrode 22 due to insertion and extraction of lithium. % Is more preferable. It is considered that the larger the amount of lithium, or the amount of oxidized and decomposed lithium salt, or the amount of lithium releasing substance that the negative electrode 22 has at the time of assembly is more advantageous for suppressing the deterioration of the discharge capacity during charge / discharge cycles, but too large. This is because the amount of lithium metal deposited on the negative electrode 22 at the time of full charge increases, which may adversely affect battery characteristics.

  In this secondary battery, the ratio (A / B) of the thickness A of the positive electrode mixture layer 21B to the thickness B of the negative electrode mixture layer 22B is preferably 0.92 or more. The thickness ratio (A / B) varies depending on the capacities of the positive electrode mixture layer 21B and the negative electrode mixture layer 22B. If the thickness ratio is 0.92 or more, the negative electrode 22B may have a lower open circuit voltage than the overcharge voltage. This is because lithium metal can be deposited stably and high energy density and good charge / discharge cycle characteristics can be obtained. The larger the thickness ratio (A / B) is, the higher the energy density tends to be. However, if the ratio is too large, the charge / discharge cycle characteristics may be reduced. It is preferably 0 or less.

  Here, the thickness A of the positive electrode mixture layer 21B is represented by the sum (Ad1 + Ad2) of the thicknesses Ad1 and Ad2 on both sides of the positive electrode current collector 21A. The thickness B of the negative electrode mixture layer 22B is also represented by the sum (Bd1 + Bd2) of the thicknesses Bd1 and Bd2 on both sides of the negative electrode current collector 22A. In addition, the positive electrode mixture layer 21B or the negative electrode mixture layer 22B is formed on both surfaces of the positive electrode current collector 21A or the negative electrode current collector 22A at the innermost end or the outermost end of the spirally wound electrode body 20. In some cases, it is provided only on one side. Also in this case, the thickness A of the positive electrode mixture layer 21B is represented by Ad1 + Ad2 and the thickness B of the negative electrode mixture layer 22B is represented by Bd1 + Bd2, and the thickness of the thickest portion is the thickness A of the positive electrode mixture layer 21B or the negative electrode mixture layer in the present invention. It is defined as the thickness B of the agent layer 22B. The same applies to the case where the positive electrode mixture layer 21B is provided only on one surface of the positive electrode current collector 21A or the case where the negative electrode mixture layer 22B is provided only on one surface of the negative electrode current collector 22A. Is the thickness on one side.

  The thickness B of the negative electrode mixture layer 22B is a thickness in a state where lithium metal is not deposited on the negative electrode mixture layer 22B, for example, a thickness in a completely discharged state. That is, it does not include the thickness of the deposited lithium metal.

  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. As such a non-aqueous solvent, one or more of high dielectric constant solvents having a relatively high dielectric constant were used as a main solvent, and further, one or more of low viscosity solvents were mixed. It is desirable to use one.

  Examples of the high dielectric constant solvent include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and valerolactones. As the low-viscosity solvent, for example, 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, methyl propionate or ethyl propionate Or a phosphoric acid ester such as trimethyl phosphate or triethyl phosphate.

  The non-aqueous solvent includes vinylene carbonate, trifluoropropylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, It is preferable to include -methyl-1,3-dioxolan, sulfolane, methylsulfolane, 2,4-difluoro-anisole, 2,6-difluoro-anisole and the like. This is because battery characteristics can be improved. 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 outside 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 electrolyte (that is, the liquid solvent and the electrolyte salt) is as described above. As the polymer compound, for example, polyacrylonitrile, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and polyhexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, poly Examples include siloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene and polycarbonate. 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 to be added to the electrolyte varies depending on the compatibility of both, but it is usually preferable to add a polymer corresponding to 5% by mass to 50% by mass of the electrolyte.

  In this secondary battery, when charged, lithium ions are released from the positive electrode mixture layer 21B, and the lithium contained in the negative electrode mixture layer 22B is inserted into the negative electrode material capable of inserting and extracting lithium via the electrolyte. Is done. When charging is continued, the charge capacity exceeds the charge capacity capacity of the negative electrode material capable of inserting and extracting lithium, and the lithium can be inserted and extracted when the open circuit voltage is lower than the overcharge voltage. The lithium metal starts to precipitate on the surface of the negative electrode material. Thereafter, lithium metal continues to be deposited on the negative electrode 22 until charging is completed.

  Next, when discharging is performed, first, lithium metal deposited on the negative electrode 22 is eluted as an ion and occluded in the positive electrode mixture layer 21B via the electrolyte. When the discharge is further continued, lithium ions occluded in the negative electrode material capable of inserting and extracting lithium in the negative electrode mixture layer 22B are released and occluded in the positive electrode mixture layer 21B via the electrolyte. At that time, a film of lithium compound such as lithium carbonate or lithium fluoride is electrochemically formed at the interface between the negative electrode 22 and the electrolyte that are active during charging, or the lithium deposited as lithium metal is broken to cause electrochemical damage. Even if lithium is deactivated, the capacity of the deactivated lithium is supplemented by the stock lithium. Therefore, until the lithium occluded in the negative electrode mixture layer 22 </ b> B is consumed, an amount of lithium acceptable to the positive electrode 21 flows between the positive electrode 21 and the negative electrode 22. As a result, the energy density, charge / discharge cycle characteristics, and initial charge / discharge efficiency are improved.

  In addition, even when the charging / discharging device is in a so-called over-discharge state due to a failure or the like, lithium is occluded in the negative electrode 22, so that the discharge potential of the negative electrode 22 does not become noble and reaches the melting potential of the negative electrode current collector 22A. The rise is suppressed. That is, the overdischarge resistance is improved.

  In the method of manufacturing the secondary battery, the positive electrode 21, the negative electrode 22, or the electrolyte is configured so that the capacity of the negative electrode 22 at the time of the first full charge is larger than the theoretical capacity of the positive electrode 21 at the time of assembly as described above. Except for the above, others are the same as the known methods.

As described above, in the present embodiment, the negative electrode 22 has metallic lithium at the time of assembling, or the negative electrode 22 has occluded ionic lithium at the time of assembling, or the electrolyte is oxidized. The capacity of the negative electrode 22 at the time of the first full charge is larger than the theoretical capacity of the positive electrode 21 at the time of assembling because the positive electrode 21 has a lithium releasing material at the time of assembling because the decomposed lithium salt is included. since the manner made, or, in the solid-state ⁷ Li multinuclear NMR spectroscopy using lithium chloride as a reference substance in the fully charged state and a completely discharged state, -10Ppm～200ppm against resonance line Rs of the reference substance A resonance line Ri belonging to lithium ions is obtained in the range, and the resonance line Rs of the reference substance in a completely discharged state is obtained. Since the area ratio of the resonance line Ri belonging to the lithium ion to the negative electrode 22 is 3% or more of the area ratio of the resonance line Ri belonging to the lithium ion to the resonance line Rs of the reference substance in the fully charged state, The initial charge / discharge efficiency of the negative electrode material capable of inserting and extracting lithium can be improved, and the discharge capacity can be improved. Further, even if lithium metal precipitated during charging falls off from the negative electrode 22 or reacts with the electrolyte to be deactivated, the amount of capacity lost due to the deactivation is replenished by the stock lithium until the stock lithium is consumed. Since the discharge capacity is regulated by the charge and discharge efficiency of the positive electrode, the charge and discharge cycle characteristics can be improved as compared with a conventional secondary battery in which the discharge capacity is regulated by the charge and discharge efficiency of the negative electrode. Furthermore, even if overdischarge occurs, the potential rise of the negative electrode 22 is suppressed, so that the dissolution of the negative electrode current collector 22A can also be suppressed. That is, the overdischarge resistance can be improved.

  In particular, when the anode 22 has lithium in a metal state at the time of assembly, or when the anode 22 has absorbed lithium in an ion state at the time of assembly, or when the cathode 21 has lithium at the time of assembly, If the capacity of lithium is in the range of 1% or more and 100% or less with respect to the capacity of the anode 22 due to insertion and extraction of lithium, and when the electrolyte contains an oxidized lithium salt, If the amount of the material is set to be equal to or less than the amount of lithium corresponding to the capacity of the anode 22 due to insertion and extraction of lithium, more excellent charge / discharge cycle characteristics can be obtained.

  Even when the ratio (A / B) of the thickness A of the positive electrode mixture layer 21B to the thickness B of the negative electrode mixture layer 22B is set to 0.92 or more, more excellent charge / discharge cycle characteristics can be obtained. it can.

  Therefore, the battery according to the present embodiment can contribute to a reduction in the size and weight of a portable electronic device represented by a mobile phone, a PDA, or a notebook computer.

  Further, specific examples of the present invention will be described in detail.

(Examples 1-1 to 1-7)
A secondary battery having the light metal layer on the negative electrode 22 was assembled. First, 95% by mass of a lithium-cobalt composite oxide (LiCoO ₂ ) powder and 5% by mass of a lithium carbonate powder were mixed, and the mixture was 94% by mass, and Ketjen black as a conductive agent was 3% by mass. Then, 3% by mass of polyvinylidene fluoride as a binder was mixed to prepare a positive electrode mixture. Next, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a paste-like positive electrode mixture slurry, and then uniformly spread on both surfaces of a positive electrode current collector 21A made of a 20 μm-thick strip-shaped aluminum foil. The positive electrode mixture layer 21B was formed by applying, drying and compression-molding with a roll press machine, and the positive electrode 21 with a total thickness of 150 μm was produced.

  A negative electrode mixture was prepared by mixing 90% by mass of a granular graphite powder having an average particle diameter of 25 μm as a negative electrode active material and 10% by mass of polyvinylidene fluoride as a binder. Next, this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a paste-like negative electrode mixture slurry, and then uniformly spread on both surfaces of a 15 μm-thick negative electrode current collector 22A made of a strip-shaped copper foil. The negative electrode mixture layer 22B was formed by coating, drying and compression molding, and the total thickness was 160 μm. Further, a light metal layer was formed by laminating a lithium metal foil on the surface of the negative electrode mixture layer 22B, and the negative electrode 22 was produced. The capacity of the light metal layer was set to the value shown in Table 1 with respect to the capacity of graphite. The capacity ratio of the cathode 21 to the anode 22 on the facing surface is represented by the sum of the capacity of the anode 22 including the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium. Thus, the capacity of the lithium-cobalt composite oxide: the capacity of the graphite = 130: 100.

After producing the positive electrode 21 and the negative electrode 22, the positive electrode 21 and the negative electrode 22 are laminated via a separator 23 made of a microporous polyethylene stretched film having a thickness of 25 μm, and then wound many times, and the outer diameter is 14 mm and the height is 650 mm. The jelly roll type wound electrode body 20 was produced. At this time, the positive electrode 21 and the negative electrode 22 were laminated such that the light metal layer faced the positive electrode mixture layer 21B. Next, insulating plates 12 and 13 are respectively arranged on the upper and lower surfaces of the wound electrode body 20, and 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 the negative electrode lead 26 is connected to the negative electrode lead. It was led out from the current collector 22A and welded to the battery can 11, and the wound electrode body 20 was housed inside the iron battery can 11. Next, an electrolytic solution was injected into the battery can 11 by a reduced pressure method. As the electrolytic solution, one obtained by dissolving LiPF ₆ at a content of 1.5 mol / dm ³ in a solvent in which ethylene carbonate and dimethyl carbonate were mixed in equal volumes was used.

  After injecting the electrolytic solution into the inside of the battery can 11, the battery lid 14 is closed by caulking the battery can 11 through the gasket 17, and the capacities of the negative electrodes 22 in Examples 1-1 to 1-7 are as follows. A secondary battery including a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium and represented by the sum thereof was obtained.

  Further, as Comparative Example 1-1 with respect to Examples 1-1 to 1-7, a secondary battery was assembled in the same manner as in Examples 1-1 to 1-7 except that no light metal layer was formed.

  A charge / discharge test was performed on the fabricated secondary batteries of Examples 1-1 to 1-7 and Comparative example 1-1, and an initial discharge capacity and a discharge capacity retention ratio were obtained. At that time, charging was performed at a constant current of 1200 mA until the battery voltage reached 4.2 V, and then at a constant voltage of 4.2 V until the total charging time reached 4 hours. Discharging was performed at a constant current of 1200 mA until the battery voltage reached 2.75 V. The discharge capacity retention ratio was calculated as the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle, that is, (discharge capacity at the 100th cycle) / (discharge capacity at the first cycle) × 100. Table 1 shows the obtained results.

  As can be seen from Table 1, according to Examples 1-1 to 1-7, the initial discharge capacity could be increased as compared with Comparative Example 1-1. This is because, when the light metal layer and graphite come into contact with the negative electrode mixture layer 22B in the electrolytic solution, the light metal layer dissolves and becomes stock lithium, which is occluded by the graphite. It is considered that the capacity component was supplemented and the discharge capacity increased.

  That is, it was found that when the negative electrode 22 had lithium metal in a metal state at the time of assembly, the discharge capacity could be improved and a high energy density could be obtained.

  Further, as can be seen from Table 1, according to Examples 1-1 to 1-6, the discharge capacity retention ratio can be increased as compared with Comparative Example 1-1, and particularly, Examples 1-2 to 1-6. According to -4, the discharge capacity maintenance ratio was able to be 85% or more. This is presumed to be because the decrease in the capacity of the negative electrode 22 due to the loss or inactivation of lithium metal due to the charge / discharge cycle was compensated for by the stock lithium. In contrast, Example 1-7 had a smaller discharge capacity retention ratio than Comparative Example 1-1. This is advantageous in that the amount of lithium metal included in the anode 22 during assembly is larger in terms of compensating for the decrease in capacity of the anode 22, but when the amount of lithium metal is too large, the thickness of the anode 22 increases, and conversely. This is considered to be because the battery characteristics are adversely affected.

  That is, the capacity of the lithium metal that the negative electrode 22 has at the time of assembly is preferably in the range of 1% or more and 100% or less, and more preferably in the range of 10% or more and 50% or less with respect to the capacity of the negative electrode 22 due to insertion and extraction of lithium. It turned out that it was more preferable.

(Examples 2-1 to 2-7)
A secondary battery in which lithium ions were inserted into the negative electrode 22 by electrochemical treatment was assembled. Specifically, after forming the negative electrode mixture layer 22B on the negative electrode current collector 22A in the same manner as in Example 1-1, this was impregnated with an electrolytic solution, and electrolytic treatment was performed using lithium metal as a counter electrode to form a negative electrode mixture. A secondary battery was fabricated in the same manner as in Example 1-1, except that lithium was occluded in the agent layer 22 </ b> B in an ion state to produce the negative electrode 22. The amount of electrolytic treatment was changed as shown in Table 2 in Examples 2-1 to 2-7. As an electrolyte for absorbing lithium ions, a solution prepared by dissolving LiPF ₆ at a content of 1.5 mol / dm ³ in a solvent in which ethylene carbonate and dimethyl carbonate were mixed in equal volumes was used.

  Further, as Comparative Example 2-1 with respect to Examples 2-1 to 2-7, a secondary battery was assembled in the same manner as in Examples 2-1 to 2-7, except that the electrolytic treatment was not performed. .

  For the fabricated secondary batteries of Examples 2-1 to 2-7 and Comparative example 2-1, a charge / discharge test was performed in the same manner as in Example 1-1, and an initial discharge capacity and a discharge capacity retention ratio were obtained. Table 2 shows the results.

  As can be seen from Table 2, according to Examples 2-1 to 2-7, the initial discharge capacity could be increased as compared with Comparative Example 2-1. This is considered to be because the irreversible capacity of the negative electrode 22 at the time of the first charge / discharge was compensated for by the lithium occluded in the graphite in the ion state by the electrolytic treatment, and the discharge capacity increased.

  That is, it was found that when the negative electrode 22 absorbed lithium in an ionic state at the time of assembly, the discharge capacity could be improved and a high energy density could be obtained.

  Further, as can be seen from Table 2, according to Examples 2-1 to 2-6, the discharge capacity retention ratio can be increased as compared with Comparative Example 2-1. According to -4, the discharge capacity maintenance ratio was able to be 85% or more. This is presumably because the decrease in the capacity of the negative electrode 22 due to the detachment or inactivation of lithium metal due to the charge / discharge cycle was compensated for by the ionic lithium absorbed in the negative electrode 22 by the electrolytic treatment. In contrast, Example 2-7 had a smaller discharge capacity retention ratio than Comparative Example 2-1. In terms of compensating for the decrease in the capacity of the negative electrode 22, the larger the amount of electrolytic treatment, the more advantageous. However, if the amount of electrolytic treatment is too large, the amount of lithium metal deposited on the surface of the negative electrode 22 during full charge increases. On the contrary, it is considered that this is because the battery characteristics are adversely affected.

  That is, the capacity of the ionic lithium stored in the negative electrode 22 by the electrochemical treatment is preferably in the range of 1% to 100% with respect to the capacity of the negative electrode 22 due to the storage and release of lithium. It was found that the range of more than 50% was more preferable.

(Examples 3-1 to 3-7)
An oxidatively decomposed lithium salt was added to the electrolyte to assemble a secondary battery. Specifically, a light metal layer is not formed on the negative electrode 22, and LiPF ₆ is dissolved at a content of 1.5 mol / dm ³ in a solvent in which ethylene carbonate and dimethyl carbonate are mixed in an equal volume, as an electrolytic solution. Using 3.5 g of lithium oxalate (Li ₂ C ₂ O ₄ ) added and dispersed therein, the battery was charged with a constant current of 120 mA until the battery voltage reached 4.2 V before sealing the battery. The secondary battery was discharged in the same manner as in Example 1-1 except that the battery was discharged at a constant current of 120 mA until the battery voltage reached 2.75 V, and the reaction product gas generated at that time was removed from the inside of the battery. Was prepared. The concentration of lithium oxalate in the electrolyte was the value shown in Table 3 in Examples 3-1 to 3-7, and the capacity of lithium in lithium oxalate was shown in Table 3 with respect to the graphite in negative electrode 22. Value.

  In addition, as Comparative Example 3-1 with respect to Examples 3-1 to 3-7, except that lithium oxalate was not added to the electrolytic solution, the other steps were the same as in Examples 3-1 to 3-7. The next battery was assembled.

  For the fabricated secondary batteries of Examples 3-1 to 3-7 and Comparative example 3-1, a charge / discharge test was performed in the same manner as in Example 1-1, and an initial discharge capacity and a discharge capacity retention ratio were obtained. Table 3 shows the results.

  As can be seen from Table 3, according to Examples 3-1 to 3-7, the initial discharge capacity could be increased as compared with Comparative Example 3-1. This is because the oxidation potential of lithium oxalate is lower than the potential at which lithium ions in the positive electrode 21 are released, so that at the time of the first charge, lithium oxalate is released before lithium ions are released from the positive electrode active material. It is preferentially oxidized to generate carbon dioxide and lithium ions, and the generated lithium ions are reduced and occluded at the anode 22 to compensate for the irreversible capacity of the anode 22 and to release lithium from the cathode 21. It is considered that the amount of ion loss decreased and the discharge capacity increased.

  That is, it was found that when the electrolytic solution contained the oxidized lithium salt, the discharge capacity could be improved and a high energy density could be obtained.

  Also, as can be seen from Table 3, according to Examples 3-1 to 3-6, the discharge capacity retention ratio can be increased as compared with Comparative Example 3-1. According to -4, the discharge capacity maintenance ratio was able to be 85% or more. This is presumed to be because the decrease in the capacity of the negative electrode 22 due to the loss or inactivation of lithium metal due to the charge / discharge cycle was compensated for by the lithium occluded in the negative electrode 22 due to the reaction of lithium oxalate during the first charge. You. In contrast, Example 3-7 had a smaller discharge capacity retention ratio than Comparative Example 3-1. This is more advantageous as the amount of lithium oxalate is larger in terms of compensating for the decrease in the capacity of the anode 22, but if the amount of lithium oxalate is too large, the amount of lithium metal deposited on the surface of the anode 22 at the time of full charge is reduced. This is thought to be due to an increase in the number of cells, which adversely affects battery characteristics.

  That is, the capacity of lithium in the oxidatively decomposed lithium salt is preferably in the range of 1% or more and 100% or less, and more preferably in the range of 10% or more and 50% or less, with respect to the capacity of the anode 22 due to insertion and extraction of lithium. It turned out to be more preferable.

(Examples 4-1 to 4-7)
The secondary battery was assembled by holding the lithium releasing material on the positive electrode 21. Specifically, the positive electrode 21 was prepared by laminating a lithium metal foil on the positive electrode mixture layer 21B, and the other steps were the same as in Example 1-1 except that the light metal layer was not formed on the negative electrode 22. A secondary battery was manufactured. A lithium metal foil having a capacity corresponding to the capacity of graphite in the anode 22 corresponding to the capacity shown in Table 4 was used. The positive electrode 21 and the negative electrode 22 were laminated and wound such that the lithium metal foil superimposed on the positive electrode 21 was opposed to the negative electrode mixture layer 22B.

  In addition, as Comparative Example 4-1 with respect to Examples 4-1 to 4-7, except that the lithium metal foil was not overlaid on the positive electrode mixture layer 21B, the others were the same as in Examples 4-1 to 4-7. Thus, a secondary battery was manufactured.

  For the fabricated secondary batteries of Examples 4-1 to 4-7 and Comparative example 4-1, a charge / discharge test was performed in the same manner as in Example 1-1, and an initial discharge capacity and a discharge capacity retention ratio were obtained. Table 4 shows the results.

  As can be seen from Table 4, according to Examples 4-1 to 4-7, the initial discharge capacity could be increased as compared with Comparative Example 4-1. This is because at the time of the first charge, the lithium metal superimposed on the positive electrode 21 is oxidized to release lithium ions, and the lithium ions are reduced by the negative electrode 22 and occluded in graphite, so that the irreversible capacity of the negative electrode 22 is reduced. This is probably because the discharge capacity was increased. That is, the lithium metal of the positive electrode 21 is completely dissolved at the time of the first charge, and the lithium metal is not deposited on the positive electrode 21 in the subsequent charging and discharging. This is because the loss of the positive electrode active material capacity due to the irreversible capacity of the negative electrode 22 at the time of the first charge is reduced.

  That is, it was found that when the positive electrode 21 had a lithium releasing substance at the time of assembly, the discharge capacity could be improved and a high energy density could be obtained.

  Further, as can be seen from Table 4, according to Examples 4-1 to 4-6, the discharge capacity retention ratio can be increased as compared with Comparative Example 4-1. According to -4, the discharge capacity maintenance ratio was able to be 85% or more. This is because the decrease in the capacity of the negative electrode 22 due to the detachment or inactivation of lithium metal due to the charge / discharge cycle was compensated by the lithium occluded in the negative electrode 22 from the lithium metal foil superimposed on the positive electrode mixture layer 21B. It is inferred. In contrast, Example 4-7 had a smaller discharge capacity retention ratio than Comparative Example 4-1. In terms of compensating for the decrease in capacity of the negative electrode 22, the larger the amount of lithium metal included in the positive electrode 21 at the time of assembly is more advantageous, but if the amount of lithium metal included in the positive electrode 21 is too large, the negative electrode 22 may fail during full charging. This is considered to be because the amount of lithium metal deposited on the surface of No. 22 increases and adversely affects battery characteristics.

  That is, the capacity of the positive electrode 21 at the time of assembly is preferably 1% or more and 100% or less, and more preferably 10% or more and 50% or less, with respect to the capacity of the negative electrode 22 due to insertion and extraction of lithium. It turned out to be more preferable.

(Examples 5-1 to 5-3)
In the same manner as in Examples 2-1 to 2-7, lithium ions were inserted into the negative electrode mixture layer 22B by electrochemical treatment to assemble a secondary battery. The conditions at that time were the same as those of Examples 2-1 to 2-7, except for the following. The thickness A of the positive electrode mixture layer 21B was changed as shown in Table 5 in Examples 5-1 to 5-3. As the negative electrode active material, artificial graphite having an electrochemical equivalent of 320 mAh / g in a lithium storage reaction was used. The electrochemical equivalent is defined as the maximum amount of lithium absorbed when lithium metal does not precipitate on the surface of artificial graphite. The thickness B of the negative electrode mixture layer 22B was changed as shown in Table 5 in Examples 5-1 to 5-3. The amount of the positive electrode active material and the amount of the negative electrode active material were adjusted so that the negative electrode utilization rate specified in Expression 1 in Examples 5-1 to 5-3 was a value shown in Table 5. The composition of the electrolyte when the lithium ions are occluded in the negative electrode mixture layer 22B is the same as in Examples 2-1 to 2-7, and the lithium metal foil is opposed to the negative electrode mixture layer 22B to convert the negative electrode 22 into the electrolyte. After immersion, the negative electrode 22 is brought into contact with the lithium metal foil, and lithium ions having a lithium ion amount of 30% of the amount of lithium ions that can be absorbed by the negative electrode 22 are applied to the negative electrode mixture layer 22B using a galvanostat at a current of 3 mA / cm ² . Occluded. The outer diameter of the wound electrode body 29 was 18 mm, and the height was 500 mm.

  Table 5 shows the thickness A of the positive electrode mixture layer 21B, the thickness B of the negative electrode mixture layer 22B, and the negative electrode utilization rate as Comparative Examples 5-1 and 5-2 with respect to Examples 5-1 to 5-3. A secondary battery was assembled in the same manner as in Examples 5-2 and 5-3, except that lithium ions were not occluded in the negative electrode mixture layer 22B by electrochemical treatment. Further, as Comparative Example 5-3 with respect to Examples 5-1 to 5-3, except that the utilization rate of the negative electrode was changed as shown in Table 5, the others were the same as in Examples 5-2 and 5-3. To assemble the secondary battery.

Charge / discharge tests were performed on the fabricated secondary batteries of Examples 5-1 to 5-3 and Comparative examples 5-1 to 5-3, and the initial charge capacity, the initial discharge capacity, the initial charge / discharge efficiency, and the discharge capacity retention rate were measured. I asked. At this time, charging was performed at a constant current of 600 mA until the battery voltage reached 4.20 V, and then at a constant voltage of 4.20 V until the total charging time reached 4 hours. On the other hand, discharging was performed at a constant current of 600 mA until the battery voltage reached 2.75 V. The initial charge / discharge efficiency is calculated as the ratio (%) of the initial discharge capacity to the initial charge capacity, that is, (initial discharge capacity) / (initial charge capacity) × 100. It was calculated as the ratio (%) of the discharge capacity at the cycle, that is, (discharge capacity at the 200th cycle) / (initial discharge capacity) × 100. Table 5 shows initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and discharge capacity retention rate of Examples 5-1 to 5-3 and Comparative Examples 5-1 to 5-3.

Further, the secondary batteries of Examples 5-1 to 5-3 and Comparative examples 5-1 to 5-3 were charged and discharged for one cycle under the above-described conditions and then completely charged again. lithium chloride used as a reference substance was analyzed by solid ⁷ Li multinuclear NMR spectroscopy. Furthermore, the secondary batteries of Examples 5-1 to 5-3 and Comparative examples 5-1 to 5-3 were charged and discharged for two cycles under the above-described conditions, and after the third cycle of complete charge, the batteries were changed to 0. battery voltage at a constant current of .1C is dismantled what was completely discharged until reaching 2.75 V, was analyzed by similarly solid ⁷ Li multinuclear NMR spectroscopy. That is, analysis was performed on batteries within three cycles from the first charge. Note that 0.1 C is a current value at which the rated capacity (first discharge capacity in this case) of the battery can be discharged in 10 hours. At the time of analysis, 60 mg of the negative electrode mixture layer 22B was weighed, and 10 mg of lithium chloride as an internal reference substance was weighed and mixed, followed by measurement.

  As a result, in the secondary batteries of Examples 5-1 to 5-3, in the fully charged state, a resonance line Rm belonging to lithium metal was obtained at 265 ppm with respect to the resonance line Rs of lithium chloride as the internal standard substance. Was. That is, deposition of lithium metal was observed. In addition, a resonance line Ri belonging to lithium ions was obtained at 44 ppm with respect to the resonance line Rs of lithium chloride as the internal standard substance. On the other hand, in the fully discharged state, the resonance line Rm is not obtained at 265 ppm, the resonance line Ri is obtained at 44 ppm, and the area ratio of the resonance line Ri of 44 ppm to the resonance line Rs of lithium chloride is the same as that of lithium chloride in the fully charged state. Was 3% or more of the area ratio of the resonance line Ri of 44 ppm to the resonance line Rs. That is, in the secondary batteries of Examples 5-1 to 5-3, 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. I found out. Further, it was found that more lithium was stored in the negative electrode 22 than lithium flowing between the positive electrode 21 and the negative electrode 22.

  In contrast, in the secondary battery of Comparative Example 5-1, in the fully charged state, resonance lines Rm and Ri were obtained at 265 ppm and 44 ppm with respect to the resonance line Rs of lithium chloride. Further, even in the completely discharged state, a slight resonance line Ri was obtained at 44 ppm with respect to the resonance line Rs of lithium chloride. The area ratio of the resonance line Ri of 44 ppm to the resonance line Rs of lithium chloride in the state was 3% or less. Therefore, "none" is described in Table 5. That is, in the secondary battery of Comparative Example 5-1, 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. It was found that more lithium was not stored than lithium flowing between the positive electrode and the negative electrode.

  In the secondary battery of Comparative Example 5-2, in the fully charged state, only the resonance line Ri was obtained at 44 ppm with respect to the resonance line Rs of lithium chloride. Further, even in the completely discharged state, a slight resonance line Ri was obtained at 44 ppm with respect to the resonance line Rs of lithium chloride. The area ratio of the resonance line Ri of 44 ppm to the resonance line Rs of lithium chloride in the state was 3% or less. Therefore, "none" is described in Table 5. That is, it was found that the secondary battery of Comparative Example 5-2 was a lithium ion secondary battery in which the capacity of the negative electrode was represented by a capacity component due to insertion and extraction of lithium. In addition, it was found that the negative electrode did not store more lithium than lithium flowing between the positive electrode and the negative electrode.

  Further, in the secondary battery of Comparative Example 5-3, in the fully charged state, only the resonance line Ri was obtained at 44 ppm with respect to the resonance line Rs of lithium chloride. On the other hand, in the fully discharged state, a resonance line Ri is obtained at 44 ppm with respect to lithium chloride, and the area ratio of the resonance line Ri of 44 ppm with respect to the resonance line Rs of lithium chloride is the resonance line Rs of lithium chloride in the fully charged state. 3% or more of the area ratio of the resonance line Ri of 44 ppm to the That is, the secondary battery of Comparative Example 5-2 is a lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium. It turns out that more lithium is stored.

  Further, as can be seen from Table 5, according to Example 5-1, the initial charge / discharge efficiency and the discharge capacity retention rate were significantly improved as compared with Comparative Example 5-1. On the other hand, in Comparative Examples 5-2 and 5-3, which are lithium ion secondary batteries, the initial charge / discharge efficiency was higher in Comparative Example 5-3 than in Comparative Example 5-2, but the discharge capacity was higher. As for the retention ratio, Comparative Example 5-2 was higher than Comparative Example 5-3. That is, the capacity of the anode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and in a battery represented by the sum thereof, the resonance line Rs of the reference substance in a completely discharged state is obtained. The negative electrode 22 having an area ratio of the resonance line Ri belonging to the lithium ion to the resonance line Rs of the reference material in the fully charged state immediately before discharging is 3% or more of the area ratio of the resonance line Ri belonging to the lithium ion to the fully charged state immediately before discharging. It has been found that the discharge capacity and the charge / discharge cycle characteristics can be improved if used.

  Further, according to Example 5-1, the discharge capacity retention ratio can be improved as compared with Examples 5-2 and 5-3, and Comparative Examples 5-2 and 5-5 are lithium ion secondary batteries. The discharge capacity retention ratio was able to be improved as compared with No. 3. That is, it was found that if the ratio (A / B) of the thickness A of the positive electrode mixture layer to the thickness B of the negative electrode mixture layer was increased, the charge / discharge cycle characteristics could be significantly improved.

  As described above, the present invention has been described with reference to the embodiments and the examples. However, the present invention is not limited to the embodiments and the examples, and various modifications are possible. For example, in the above embodiments and examples, the case where lithium is used as the light metal has been described. However, another alkali metal such as sodium (Na) or potassium (K), or an alkaline earth such as magnesium or calcium (Ca) is used. The present invention can be applied to a case where a metal, another light metal such as aluminum, or lithium or an alloy thereof is used, and a similar effect can be obtained. At that time, a negative electrode material, a positive electrode active material, a non-aqueous solvent, an electrolyte salt, or the like capable of inserting and extracting a light metal is selected according to the light metal. However, it is preferable to use lithium or an alloy containing lithium as the light metal because voltage compatibility with a lithium ion secondary battery currently in practical use is high. When an alloy containing lithium is used as a light metal, a substance capable of forming an alloy with lithium is present in the electrolyte, and an alloy may be formed at the time of deposition. Possible substances are present and may form an alloy upon precipitation.

  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. Examples of other electrolytes include, for example, a polymer solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, an ion-conductive ceramic, an inorganic solid electrolyte made of an ion-conductive glass or an 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. In addition, the present invention can be applied to a so-called coin type, button type or card type secondary 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. It is a characteristic diagram showing a solid ⁷ Li multinuclear NMR spectrum of lithium chloride. FIG. 3 is a characteristic diagram showing a solid-state ⁷ Li multi-nuclide nuclear magnetic resonance spectroscopy spectrum of the negative electrode shown in FIG. 2 in a completely discharged state. FIG. 3 is a characteristic diagram showing a solid-state ⁷ Li multi-nuclide nuclear magnetic resonance spectroscopy spectrum of the negative electrode shown in FIG. 2 in a fully charged state. FIG. 9 is a characteristic diagram showing a solid-state ⁷ Li multi-nuclide nuclear magnetic resonance spectroscopy spectrum of a conventional negative electrode in a fully charged state. FIG. ⁷ is a characteristic diagram showing a solid-state ⁷ Li multi-nuclide nuclear magnetic resonance spectroscopy spectrum in a completely discharged state of a conventional negative electrode. FIG. 3 is a characteristic diagram illustrating another solid-state ⁷ Li multi-nuclide nuclear magnetic resonance spectroscopy spectrum in a completely discharged state of the negative electrode illustrated in FIG. 2. FIG. 3 is a characteristic diagram illustrating another solid-state ⁷ Li multi-nuclide nuclear magnetic resonance spectroscopy spectrum of the negative electrode illustrated in FIG. 2 in a fully charged state.

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, Ri, Rm, Rs: resonance line, Ai, As: area.

Claims (24)

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 occlusion and release of light metal, and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof,
The negative electrode, the fully charged and fully discharged state Solid ⁷ Li multinuclear NMR spectroscopy using lithium chloride (LiCl) as a reference substance in the range of -10ppm~200ppm respect resonance line of the reference substance To obtain another resonance line,
The battery wherein the area ratio of another resonance line to the resonance line of the reference substance in the fully discharged state is 3% or more of the area ratio of the other resonance line to the resonance line of the reference substance in the fully charged state. .   The battery according to claim 1, wherein the electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.   The battery according to claim 1, wherein the positive electrode includes a composite oxide of a light metal and a transition metal. The positive electrode has a positive electrode mixture layer capable of inserting and extracting light metal,
The negative electrode has a negative electrode mixture layer capable of inserting and extracting light metal,
The battery according to claim 1, wherein a ratio (A / B) of a thickness A of the positive electrode mixture layer to a thickness B of the negative electrode mixture layer is 0.92 or more. 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 occlusion and release of light metal, and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof,
The battery according to claim 1, wherein the negative electrode includes a light metal in a metal state when assembled.   The negative electrode includes a negative electrode mixture layer capable of inserting and extracting light metal during assembly, and a light metal layer in a metal state provided on a surface of the negative electrode mixture layer. Batteries.   6. The battery according to claim 5, wherein the capacity of the light metal in the metallic state is in a range of 1% or more and 100% or less with respect to the capacity due to occlusion and release of the light metal.   The battery according to claim 5, wherein the negative electrode includes a carbon material.   9. The battery according to claim 8, wherein the negative electrode includes at least one selected from the group consisting of graphite, graphitizable carbon, and non-graphitizable carbon. 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 occlusion and release of light metal, and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof,
A battery characterized in that the negative electrode has an ionized light metal inserted therein during assembly.   11. The battery according to claim 10, wherein the capacity of the light metal in the ionic state is in a range of 1% or more and 100% or less with respect to the capacity due to occlusion and desorption of the light metal.   The battery according to claim 10, wherein the negative electrode includes a carbon material.   13. The battery according to claim 12, wherein the negative electrode includes at least one selected from the group consisting of graphite, graphitizable carbon, and non-graphitizable carbon. 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 occlusion and release of light metal, and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof,
The battery according to claim 1, wherein the electrolyte includes a light metal salt that is oxidatively decomposed at the positive electrode.   15. The battery according to claim 14, wherein a substance amount of the light metal salt is equal to or less than a substance amount of the light metal corresponding to a capacity due to occlusion and desorption of the light metal.   The battery according to claim 14, wherein the electrolyte includes lithium oxalate as the light metal salt.   The battery according to claim 14, wherein the negative electrode includes a carbon material.   18. The battery according to claim 17, wherein the negative electrode includes at least one selected from the group consisting of graphite, graphitizable carbon, and non-graphitizable carbon. 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 occlusion and release of light metal, and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof,
A battery comprising a substance which irreversibly emits light metal during assembly in the battery. As before Symbol irreversibly substances that emit light metal, batteries of claim 19, wherein further comprising a light metal.   20. The battery according to claim 19, wherein the capacity of the light metal which the positive electrode has at the time of assembly is in a range of 1% or more and 100% or less with respect to the capacity of the negative electrode due to insertion and extraction of the light metal.   The battery according to claim 19, wherein the negative electrode includes a carbon material.   23. The battery according to claim 22, wherein the negative electrode includes at least one selected from the group consisting of graphite, graphitizable carbon, and non-graphitizable carbon. 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 occlusion and release of light metal, and a capacity component due to precipitation and dissolution of light metal, and is represented by the sum thereof,
A battery wherein the capacity of the negative electrode at the time of the first full charge is larger than the theoretical capacity of the positive electrode at the time of assembly.

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