JP2004288644A - Manufacturing method of cathode active material, manufacturing method of anode active material, and manufacturing method of secondary battery utilizing lithium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery that utilizes lithium using the insertion/desorption reaction of lithium ion of which electric capacity is large, charge and discharge efficiency is high, energy density is high, and cycle life is long. <P>SOLUTION: A manufacturing method of a cathode active material or an anode active material is provided with a process in which a nonionic surface active agent is dissolved into an organic solvent sparingly soluble or insoluble into water, and after an emulsion is prepared by mixing transition metal salt aqueous solution, Li salt or LiOH aqueous solution is made to react, and the mixture is dried and calcined, thereby a porous hollow-structure lithium-transition metal oxide is obtained, as well as a manufacturing method of the secondary battery which utilizes lithium is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a secondary battery using lithium. More specifically, the present invention relates to a method of manufacturing a lithium secondary battery capable of suppressing lithium dendrite generated by repeated charge and discharge.

Recently, the amount of CO ₂ gas contained in the atmosphere is increasing, and it is predicted that global warming will occur due to the greenhouse effect of CO ₂ gas. For this reason, a thermal power plant that emits a large amount of CO ₂ gas, which burns fossil fuels such as oil and coal and converts its energy into electric energy, is newly constructed. Things are getting harder.

  In addition, in order to perform power generation by thermal power generation most efficiently, it is preferable to operate under certain conditions. There is also a reason that it is difficult to rapidly change the amount of power generation, and the amount of power generation is adjusted during the daytime when power consumption is high, where factories and the like generally operate. Therefore, in the nighttime when the power consumption decreases, the generated power is wasted at present. Therefore, as an effective use of the power generated by generators such as thermal power plants, nighttime power is stored in a secondary battery installed in ordinary households, etc., and this is used during the daytime when power consumption is high, to reduce the load. Leveling, so-called load leveling, has been proposed and a secondary battery that can be used for it has been eagerly desired.

In addition, in electric vehicle applications that do not emit substances that pollute the atmosphere, such as carbon oxides (CO _x ), nitrogen oxides (NO _x ), hydrocarbons (CH), and particles, during operation, they are practically useful. The development of a secondary battery having a higher energy density is also expected from the viewpoint of securing the battery.

  Further, for power supply applications for portable devices such as book-type personal computers, word processors, video cameras, and mobile phones, there is an urgent need to develop even smaller, lighter, and higher-performance secondary batteries.

  As the small, lightweight and high-performance secondary battery, since an example in which a lithium-graphite intercalation compound is applied to a negative electrode of a secondary battery was reported in Non-Patent Document 1, for example, carbon was used as a negative electrode material, and lithium ion was used. A rocking chair type secondary battery, which uses a compound introduced into the intercalation compound as the positive electrode active material and inserts and stores lithium between the carbon layers by a charging reaction, so-called "lithium-ion battery" has been developed and partially commercialized. is there. In this lithium ion battery, carbon is used as a negative electrode, which is a host material that uses lithium as a guest and intercalates between layers, to suppress dendrite growth of lithium during charging and achieve long life in a charge / discharge cycle.

Since a long-life secondary battery can be achieved in this way, proposals and studies for applying various carbons to the negative electrode have been actively made. In Patent Document 1, a carbon material in which the atomic ratio of hydrogen / carbon is less than 0.15, the spacing between (002) planes is 0.33 nm or more, and the size of c-axis crystallites is 15 nm or less. There has been proposed a secondary battery using an alkali metal ion such as a lithium ion using lithium as a negative electrode. In Patent Document 2, the (002) plane spacing is not less than 0.370 nanometers, the true density is less than 1.70 g / cm ³ , and there is no exothermic peak at 700 ° C. or more in differential thermal analysis in an air stream. A secondary battery using a carbon material for a negative electrode has been proposed.

  In addition, as examples of research applying various types of carbon to battery negative electrodes, non-patent document 2 describes carbon fibers, non-patent document 3 mesoface microspheres, non-patent document 4 natural graphite, non-patent document 5 graphite whiskers, Patent Document 6 reports a study using a fired body of furfuryl alcohol resin as a negative electrode.

  However, in a lithium ion battery that uses carbon as a negative electrode active material for storing lithium, the discharge capacity that can be taken out stably even when charging and discharging is repeated is the theoretical capacity of a graphite intercalation compound that stores one lithium atom for every six carbon atoms. What exceeds is not yet obtained. Therefore, a lithium ion battery using carbon as a negative electrode active material has a long cycle life, but does not reach the energy density of a lithium battery using lithium metal itself as a negative electrode active material.

  The reason why it is difficult to commercialize a high-capacity lithium storage battery using lithium metal for the negative electrode is that it is difficult to suppress the generation of lithium dendrite, which is generated by repeated charge and discharge and is a main cause of short circuit. When lithium dendrite grows and the negative electrode and the positive electrode are short-circuited, the energy of the battery is consumed in a short time at the short-circuited portion, generating heat, decomposing the solvent of the electrolyte and generating gas. As a result, the internal pressure is increased, and the battery is damaged. As a countermeasure, a method of using a lithium alloy such as lithium-aluminum for the negative electrode has been proposed in order to suppress the reactivity of lithium, but the cycle life is not sufficiently satisfied, and it has not been put to practical use in a wide range.

  On the other hand, Non-Patent Document 7 discloses a high energy density lithium secondary battery using an aluminum foil having an etched surface as a negative electrode, although the energy density is lower than that of a lithium primary battery. However, when the charge and discharge cycle is repeated to the practical range, the aluminum foil repeatedly expands and contracts, cracks are generated, the current collecting property is reduced, and dendrite growth occurs, and the cycle life can be used at a practical level. A secondary battery cannot be obtained.

  Therefore, development of a negative electrode material having a long life and a higher energy density than a carbon negative electrode currently in practical use has been eagerly desired.

  Furthermore, in order to realize a secondary battery with a high energy density, development of a positive electrode material is indispensable. At present, as a positive electrode active material, a lithium-transition metal oxide in which lithium ions are inserted (intercalated) into an interlayer compound is mainly used, but only a discharge capacity of 40 to 60% of a theoretical capacity has been achieved. .

Lithium secondary batteries, including "lithium ion batteries," which use lithium ions as guests for charge / discharge reactions, have a cycle life in the practical range and are even more advanced than the carbon anodes and transition metal oxide cathodes currently in practical use. There is a strong demand for the development of high capacity negative and positive electrodes.
U.S. Pat. No. 4,702,977 (JP-A-62-220666) U.S. Pat. No. 4,959,281 (JP-A-2-66656) JOURNAL OF THE ELECTROCHEMICAL SOCIETY 117, 222 (1970) Electrochemistry, Vol. 57, p614 (1989) Proceedings of the 34th Battery Symposium, p77 (1993) Proceedings of the 33rd Battery Symposium, p217 (1992) Proceedings of the 34th Battery Symposium, p79 (1993) Proceedings of the 58th Annual Meeting of the Electrochemical Association, p15 (1991) JOURNAL OF APPLIED ELECTROCHEMISTRY 22 (1992) 620-627

  An object of the present invention is to provide a method for manufacturing a positive electrode active material, a method for manufacturing a negative electrode active material, and a method for manufacturing a secondary battery using lithium, which can provide a secondary battery using lithium as described below. And

  That is, an object of the present invention is to provide a lithium secondary battery using lithium ions as a guest for a charge / discharge reaction and having a high energy density and a long cycle life. And

  Another object of the present invention is to provide a secondary battery using lithium having high charge / discharge efficiency and high energy density.

  A further object of the present invention is to provide a secondary battery using lithium which can be smoothly performed at a current density lower than an electrochemical reaction caused by charge and discharge.

  In addition, an object of the present invention is to provide a secondary battery using lithium which has little or no generation of dendrite, has a long life, and has high performance stability.

  Further, the present invention is a secondary battery using lithium having at least a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte, wherein at least one of the negative electrode and the positive electrode is porous. It is an object of the present invention to provide a secondary battery using lithium having an active material having a hollow structure.

  The above object is achieved by the following means.

  (1) A nonionic surfactant is dissolved in an organic solvent that is hardly soluble or insoluble in water, a transition metal salt aqueous solution is mixed to prepare an emulsion, and then an Li salt or LiOH aqueous solution is reacted and dried and calcined. A method for producing a positive electrode active material, comprising a step of obtaining a lithium-transition metal oxide having a porous hollow structure.

  (2) A method for producing a secondary battery using lithium having at least a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte. After dissolving a nonionic surfactant and mixing an aqueous solution of a transition metal salt to prepare an emulsion, a Li salt or an aqueous solution of LiOH is reacted and dried and fired to obtain a lithium-transition metal oxide having a porous hollow structure. A method for producing a positive electrode active material by using the lithium secondary battery.

  (3) Air or a liquid having no affinity for the polymer is passed through the center of the double cylindrical nozzle, and the polymer or the melted polymer is passed through the outer cylindrical nozzle to be spun and spun. The method for producing a negative electrode active material, comprising the steps of: obtaining a carbon having a porous hollow structure by firing and pulverizing after preparing the carbon black.

  (4) A method for producing a negative electrode active material, comprising a step of obtaining carbon having a porous hollow structure by carbonizing a plant, performing an oxidation treatment and an alkali etching treatment, and firing and pulverizing the plant.

  (5) A nonionic surfactant is dissolved in an organic solvent that is hardly soluble or insoluble in water, and an aqueous solution of a transition metal salt is mixed to prepare an emulsion. A method for producing a negative electrode active material, comprising a step of obtaining a lithium-transition metal oxide having a porous hollow structure.

  (6) A nonionic surfactant is dissolved in an organic solvent that is hardly soluble or insoluble in water, an aqueous solution of a transition metal salt is mixed to prepare an emulsion, and then a Li salt or an aqueous solution of LiOH is reacted and dried and calcined. A step of obtaining a lithium-transition metal oxide having a porous hollow structure, and subjecting the lithium-transition metal oxide having a porous hollow structure obtained in the step to heat treatment in a reducing atmosphere of hydrogen gas or exposure to hydrogen plasma, Obtaining a metal particle having a porous hollow structure by reduction.

  (7) The method for producing a negative electrode active material according to (6), further including a step of performing any one of an oxidation treatment, a halogenation treatment, and a nitridation treatment on the surface of the metal particles.

  (8) Fine particles of an organic polymer are dispersed in an electroless plating solution, a metal film is formed on the surface of the fine particles of the organic polymer by a reduction reaction, and then the organic polymer particles coated with the obtained metal film are removed. A method for producing a negative electrode active material, comprising a step of obtaining metal particles having a porous hollow structure by dispersing and dissolving an organic polymer in a solvent to remove the organic polymer.

  (9) A method for manufacturing a secondary battery using lithium having at least a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte, wherein any of the above (3) to (8) A method for manufacturing a secondary battery using lithium, comprising a step of manufacturing a negative electrode active material by the method according to any one of the preceding claims.

  According to the present invention, in a secondary battery utilizing lithium utilizing an insertion / desorption reaction of lithium ions, a positive electrode or a negative electrode having a substantially increased specific surface area can be produced, so that the electrochemical chemistry accompanying charging / discharging can be further improved. It can be performed smoothly at a low current density. As a result, it is possible to provide a lithium-based secondary battery having a long cycle life, a high charge / discharge rate, and a high energy density.

  Further, it is possible to provide a secondary battery using lithium having a long life and excellent in performance stability with little or no generation of dendrite.

  Hereinafter, the present invention will be described in more detail.

  According to the present invention, at least an electrode (negative electrode or positive electrode) of a lithium secondary battery having a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte has a porous hollow structure.

  As described above, in the present invention, since the positive electrode or the negative electrode of the lithium secondary battery is formed of the active material having the porous hollow structure, the contact area with the electrolytic solution is increased, and the movement accompanying the lithium ion electrochemical reaction is performed. And the distortion caused by the volume expansion of the active material when lithium is inserted can be suppressed. As a result, the electrochemical reaction due to charge / discharge proceeds efficiently, a large current can easily flow, the battery capacity can be increased, and destruction of the electrode due to repeated charge / discharge can be suppressed. Therefore, a high-capacity, long-life lithium battery that can be rapidly charged can be realized.

  Further, in the present invention, when a conductor is provided in the hollow portion of the active material having the porous hollow structure of the positive electrode or the negative electrode, the current collecting ability can be further increased. As a result, a larger current can flow and the charging / discharging efficiency can be improved. Therefore, a high-capacity secondary battery that can be rapidly charged can be realized.

  Furthermore, in the present invention, when the active material having a porous hollow structure of the negative electrode is at least composed of carbon or metal oxide, lithium deposited during charging does not directly contact the electrolytic solution, thereby suppressing lithium dendrite growth. The cycle life can be extended. In the present invention, when the active material having a porous hollow structure of the negative electrode is composed of at least a metal, lithium is deposited on the metal surface during lithium deposition or is alloyed with the metal, so a large amount per unit volume of the negative electrode. Since lithium can be stored, high capacity can be achieved.

  Further, in the present invention, the active material having a porous hollow structure of the negative electrode is provided with a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, and a Group 17 element of the periodic table of elements according to the IUPAC inorganic chemical nomenclature. When carbon containing an element selected from the group consisting of carbon and lithium is used, a large amount of lithium can be inserted and, in addition, reactivity with impurities can be reduced, so that the life can be extended. In particular, the replacement of carbon with boron, which is a Group 13 element, silicon which is a Group 14 element, and nitrogen or phosphorus which is a Group 15 element in the periodic table of elements extends the crystal lattice of carbon and expands the storage space for lithium. This is preferable because the volumetric expansion at the time of lithium insertion is reduced, so that fatigue deterioration due to expansion and contraction can be suppressed. Reactivity with impurities in the electrolytic solution can be reduced by bonding to oxygen, which is a Group 16 element in the periodic table, and part of carbon in the negative electrode of fluorine or chlorine, which is a Group 17 element. preferable. Thereby, a negative electrode with higher capacity and longer life can be realized.

  As described above, a lithium secondary battery using a porous hollow structure active material, which is a host material capable of inserting and removing lithium ions, for a positive electrode or a negative electrode can achieve high electric capacity and high energy density.

  In the present invention, a substance from which lithium is desorbed or inserted and which can reversibly desorb and insert lithium by an electrochemical reaction is referred to as an active material of a lithium secondary battery.

  Hereinafter, the present invention will be described in more detail with reference to the drawings as necessary.

  FIGS. 1A, 1B, and 1C are conceptual views of a porous hollow active material serving as a positive electrode active material or a negative electrode active material serving as a lithium ion host material, respectively, using the secondary battery of the present invention. It is a schematic sectional drawing which shows a cross section.

  FIG. 2 is a conceptual perspective view of the active material having a spherical structure shown in FIGS. 1A to 1C, and FIG. 7 is a conceptual perspective view of an active material having a tubular structure.

  1A to 1C In FIGS. 2 and 7, reference numeral 100 denotes an active material constituent material, 101 denotes pores, 102 denotes a hollow portion, 103 denotes a skin layer, and 104 denotes a conductor provided in the hollow portion.

  The active material shown in FIGS. 1A and 2 has a structure in which a hollow portion 102 is formed by an active material forming material 100 having pores 101. In FIG. 7, the hollow portion 102 has a cylindrical shape.

  The active material shown in FIG. 1B is an example in which a skin layer 103 is provided on the outer surface of the active material constituent material 100 in FIG. The skin layer 103 may be a surface oxide layer for improving the oxidation stability of the active material constituent material 100 in the air or a halide layer for suppressing the reactivity of the active material constituent material 100 with the electrolyte. A reaction suppression layer can be mentioned.

  The active material shown in FIG. 1C shows an example in which a conductor 104 is provided in the hollow portion 102 in FIG. 1A.

  The diameter of the active material having the hollow structure varies depending on the preparation method and the pulverization step. However, in order to increase the capacity of the battery, it is preferable that the particle diameter is small because the packing density can be increased.

  However, if the particle size is too small, it becomes difficult to handle the hollow active material. Therefore, the diameter of the particles of the hollow active material is preferably 0.01 to 100 microns, more preferably 0.1 to 10 microns. More preferred. The size of the pores is preferably about 1/10 or less of the diameter of the active material particles.

  FIG. 3 is a conceptual diagram for explaining an example of the structure of the positive electrode or the negative electrode used in the secondary battery of the present invention, and is a schematic cross-sectional view of one surface side of the positive electrode or the negative electrode. Therefore, the active material layers 203 can be provided on both sides of the current collector 200. The positive electrode or the negative electrode 204 is formed by forming a porous hollow active material 201 having a cross-sectional shape as described with reference to FIGS. The structure is such that an active material layer 203 formed by binding is provided. Although not shown in FIG. 3, in an actual battery, the electrolyte is in contact with the active material layer 203 of the positive electrode or the negative electrode. Although not shown in FIG. 3, when the conductivity of the porous hollow active material 201 is low, it is preferable to form an active material layer 203 by further adding a conductive auxiliary to the binder. Further, the proportion of the active material in the active material layer is preferably 50 wt% or more, and more preferably 70 wt% or more, from the viewpoint of maintaining a high battery capacity.

  As an example of a method for adjusting the positive electrode active material particles having a porous hollow structure when a lithium-transition metal oxide is used as the positive electrode active material agent, a method utilizing an interfacial reaction is exemplified.

  More specifically, according to one of the production methods of the present invention, a nonionic surfactant is dissolved in a water-insoluble or insoluble organic solvent, and a transition metal salt aqueous solution is mixed to form an emulsion. After the preparation, a Li salt or an aqueous solution of LiOH is reacted and dried and fired, whereby a lithium-transition metal oxide having a porous hollow structure can be obtained. Further, as a method of preparing the positive electrode active material particles of a porous hollow structure having a conductor provided in the hollow portion, by using a transition metal salt aqueous solution in which conductor powder such as metal fine powder is dispersed at the time of preparing the emulsion. Can be easily obtained.

  The negative electrode active material particles can be prepared in the same manner as the positive electrode active material particles.

  Next, a preferred example of a method for preparing metal particles having a porous hollow structure will be described.

  As a preferable preparation method of the metal particles having a porous hollow structure, according to one of the production methods of the present invention, metal oxide particles prepared by the same method as the constitution method of the positive electrode active material particles, Alternatively, a method of performing heat treatment in a reducing atmosphere of hydrogen gas or exposing it to hydrogen plasma to reduce and prepare it can be adopted. Since the metal particles prepared in this way have a large specific surface area and easily react with oxygen in air, they may affect the stability and characteristics of the manufactured battery depending on the handling. The metal surface reacts with oxygen in a liquid or under reduced pressure, and slowly oxidizes to form an oxide film on the surface.Hydrofluoric acid and the like are allowed to act to form a surface halide film, thereby increasing the resistance to the reaction. It is preferred to increase. Plasma treatment with halogenated hydrocarbons or nitrogen gas is also effective as oxidation-resistant treatment. The oxidation treatment, halogenation treatment, and nitridation treatment also have an effect of suppressing a side reaction with an organic solvent or impurities in the electrolyte during charge and discharge.

  As another preferred method for preparing the metal particles having a porous hollow structure, fine particles of an organic polymer are dispersed in an electroless plating (chemical plating) solution according to one of the production methods of the present invention. A method in which a metal film is formed on the surface of fine particles of an organic polymer by a reduction reaction, and then the organic polymer particles coated with the obtained metal film are dispersed in a solvent to dissolve and remove the organic polymer. Is mentioned.

  Anode active material particles of metal particles can also be prepared by a similar method.

  Next, a preferred example of a method for forming a porous hollow structure when carbon is used as the negative electrode active material will be described.

  As a method for preparing carbon having a porous hollow structure, according to one of the production methods of the present invention, air or a liquid having no affinity for a polymer is passed through the center of the double cylindrical nozzle, and the outer cylinder is formed. A preferred method is a method in which a molten polymer material or a dissolved polymer material is passed through a nozzle and spun to produce a polymer hollow fiber, which is then fired and pulverized to prepare.

  Another suitable method for preparing carbon having a porous hollow structure includes a method of carbonizing a plant conduit / temporary conduit according to one of the production methods of the present invention. In this method, for example, after carbonizing a plant, it is preferably prepared by oxidizing treatment and alkali etching treatment, followed by firing and pulverization. Note that carbonization is preferably performed at 600 to 1000 ° C. in an atmosphere of a negative active gas or a nitrogen gas. When performing the oxidation treatment, it is preferable to perform the treatment at 250 to 400 ° C. in the air.

  As still another preferred method of preparing carbon having a porous hollow structure, a solvent in which a nonionic surfactant and an organic polymer material are dissolved in a water-insoluble or insoluble organic solvent, and the organic polymer material is not dissolved, A method of preparing an emulsion by mixing water or an aqueous solution in which an inorganic compound is dissolved, and then dropping the solvent into a solvent in which the organic polymer material is not dissolved to precipitate the organic polymer material, followed by drying and firing. No.

  Examples of materials suitable for the organic polymer material serving as the carbon raw material include polyvinyl alcohol, polyfurfuryl alcohol, polyvinyl acetate, polyacrylonitrile, polyparaphenylene, polyparaphenylene sulfide, polyparaphenylene vinylene, polythienylene, and polydithienyl. Examples thereof include polyene, polyvinyl naphthalene, polyvinyl chloride, polyaniline, polypyrrole, furan resin, and silicone resin.

  The firing for obtaining the carbon material is preferably performed at 600 to 3000 ° C. in an inert gas or nitrogen gas atmosphere. If the firing temperature is high, graphite crystals are more likely to grow.

  By replacing at least part of the carbon atoms of the carbon with at least one element selected from Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, and Group 17 elements of the periodic table, the crystal axis is It is possible to increase the amount of lithium inserted during spreading charging, reduce distortion during insertion, and reduce the reaction with the electrolyte. Thereby, a higher capacity and longer life negative electrode for a lithium secondary battery can be formed.

  As a preferable method for preparing the porous hollow carbon containing the above elements, a polymer which is a raw material of carbon is prepared from a group 13 element, a group 14 element, a group 15 element, a group 16 element, or a group 17 element of the periodic table of elements. A method of preparing using a polymer containing at least one selected element is exemplified.

  Another suitable preparation method is a method in which a raw material polymer material is mixed with a substance containing the above-mentioned element which is easily decomposed at the time of firing, followed by firing.

  The amount of the element to be added for obtaining a negative electrode having an increased electric capacity is preferably 1 to 20 atomic% of the porous hollow carbon material obtained by firing. As the element to be added, boron is suitable for the group 13 element, silicon is suitable for the group 14 element, nitrogen or phosphorus is suitable for the group 15 element, sulfur is suitable for the group 16 element, and fluorine or chlorine is suitable for the group 17 element. Particularly, addition of a boron element is preferable. Preferable examples of the boron compound to be confused with the polymer material as the raw material before firing include triarylboron such as triphenylboron and tri-p-tolylboron, borane-4-methylmorpholine complex, and borane. -4-phenylmorpholine complex, borane-biperazine complex, borane-biperidine complex, borane-polyvinylpyridine complex, borane-pyridine complex, borane-tetrahydrofuran complex, borane-triethylamine complex, borane-trimethylamine complex, borane-methylsulfide complex, borane A borane complex such as -methyl 1,4-oxathiane complex and a tetraphenyl borate such as sodium tetraphenyl borate are preferred.

  Next, a conceptual configuration of the secondary battery of the present invention will be described with reference to FIG.

  4, reference numeral 301 denotes a negative electrode (electrode), 302 denotes a positive electrode (electrode), 303 denotes an electrolyte, 304 denotes a separator, 305 denotes a negative terminal, 306 denotes a positive terminal, and 307 denotes a housing.

  As shown in FIG. 4, the negative electrode 301 and the positive electrode 302 face each other with a separator 304 interposed therebetween, and are disposed in an electrolyte 303 held in the housings 3 and 7. The separator 304 is provided to prevent a short circuit between the negative electrode 301 and the positive electrode 302 due to contact.

  The negative electrode 301 and the positive electrode 302 have a structure as shown in FIG. 3, and the positive terminal 306 and the negative terminal 305 are electrically connected to the current collecting electrodes of the respective electrodes. However, the positive electrode terminal 306 or the negative electrode terminal 305 may be a current collecting electrode of each electrode, or the positive electrode terminal 306, the negative electrode terminal 305, or at least a part of the current collecting electrode may constitute at least a part of the housing. Good.

  Next, each component of the battery will be described in detail.

  As the material of the positive electrode material, a transition metal oxide, a transition metal sulfide, a lithium-transition metal oxide, or a lithium-transition metal sulfide is preferably used. Examples of the transition metal element that is a constituent element of the transition metal oxide or the transition metal sulfide include Sc, Y, lanthanoids, actinoids, Ti, Zr, and the like, which are elements having a partially d- or f-shell. Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au At least one kind is mentioned as a preferable element. In particular, at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, which are the first transition series metals, is preferably used.

  As the material of the negative electrode active material, carbon, metal, and metal oxide are suitable. As the carbon material, a material having a graphite layer capable of taking lithium between layers is preferable. Preferred examples of the metal material include at least one element selected from the group consisting of Cu, Ni, Al, Ti, Sn, Pb, Zn, Cr, Fe, Pt, and Pd as a preferable element. Preferable examples of the metal oxide include oxides of at least one element selected from the group consisting of tungsten, molybdenum, titanium, panadium, niobium, zirconium, tantalum, and chromium.

  In particular, as the active material particles having a porous hollow structure, metal oxide particles, metal particles, carbon, and the like are preferably exemplified.

  A preferred example of a method for preparing metal oxide particles as active material particles having a porous hollow structure will be described using positive electrode active material particles as an example.

<Positive electrode>
As described above, examples of the positive electrode in the present invention include those composed of at least the above-described porous hollow positive electrode active material, a binder, a current collector, and if necessary, a conductive auxiliary material.

  Hereinafter, a preferred example of a method for manufacturing a positive electrode will be described.

  First, a paste is prepared by mixing a porous hollow positive electrode active material, a binder and, if necessary, a conductive auxiliary material, adjusting the viscosity by adding a solvent.

  Next, the paste is applied on a current collector and dried to form a positive electrode.

  As the above coating method, for example, a coater coating method and a screen printing method can be suitably applied.

  As a conductive auxiliary material usable for the positive electrode, powdery or fibrous amorphous carbon represented by carbon black such as acetylene black and Ketjen black, graphite, and a metal inert to a battery reaction are preferable. No.

  As the binder usable for the positive electrode, for example, when the electrolytic solution is a non-aqueous solvent system, a polyolefin such as polyethylene or polypropylene, or a fluororesin such as polyvinylidene fluoride or tetrafluoroethylene polymer is preferable. Can be

  The current collector of the positive electrode in the present invention has a role of efficiently supplying a current consumed by an electrode reaction during charging or efficiently collecting a current generated during discharging. Therefore, as a material for forming the current collector of the positive electrode, a material having high conductivity and inert to a battery reaction is desirable. Preferred materials include nickel, titanium, copper, aluminum, stainless steel, platinum, palladium, gold, zinc, various alloys, and two or more composite metals of the above materials. In the case of using copper or zinc, it is preferable to use copper or zinc after coating with nickel or titanium, which is a more inert metal, in consideration of the fact that copper and zinc are easily dissolved and precipitated by charge and discharge. As the shape of the current collector, for example, a shape such as a plate shape, a foil shape, a mesh shape, a sponge shape, a fiber shape, a punching metal, and an ex-band metal can be adopted.

<Negative electrode>
Preferable examples of the negative electrode of the present invention include, for example, those composed of at least the above-mentioned porous hollow negative electrode active material, a binder, a current collector and, if necessary, a conductive auxiliary.

  Hereinafter, a preferred example of a method for manufacturing a negative electrode will be described.

  First, a porous hollow negative electrode active material and a binder are mixed, and a solvent is added to adjust the viscosity to prepare a paste.

  Next, the paste is applied on a current collector and dried to form a negative electrode.

  When the conductivity of the negative electrode active material is low, it is preferable to add the same conductive auxiliary as that used for the preparation of the positive electrode when preparing the paste, thereby enhancing the current collecting ability. As the above-mentioned binder, the same binders as those used for producing the positive electrode can be used. The material and shape of the current collector may be the same as those of the current collector described for the positive electrode.

  As a method of applying the paste, for example, a coater application method and a screen printing method can be applied.

<Separator>
The separator in the present invention has a role of preventing a short circuit between the negative electrode and the positive electrode. In some cases, it has a role of holding an electrolytic solution.

  The separator must have at least pores through which lithium ions can move, and must be insoluble and stable in the electrolytic solution. Therefore, as the separator, for example, a nonwoven fabric or a material having a microbore structure using a material such as glass, polyolefin such as polypropylene, polyethylene, or a fluororesin is preferably used. Further, a metal oxide film having fine pores or a resin film in which a metal oxide is compounded can be used. In particular, when a metal oxide film having a multilayer structure is used, the dendrite does not easily penetrate, which is effective in preventing short circuit. When a fluororesin film which is a flame retardant material, or a glass or a metal oxide film which is a nonflammable material is used, safety can be further improved.

<Electrolyte>
The use of the electrolyte in the present invention includes the following three methods.
(1) A method used as it is.
(2) A method of using as a solution dissolved in a solvent.
(3) A method in which a gelling agent such as a polymer is added to a solution to be used as an immobilized one.

  Generally, an electrolytic solution obtained by dissolving an electrolyte in a solvent is used by being retained in a porous separator.

It is necessary that the conductivity of the electrolyte at 25 ° C. is preferably 1 × 10 ⁻³ s / cm or more, more preferably 5 × 10 ⁻³ s / cm or more.

  In lithium batteries, the following electrolytes and their solvents are preferably used.

Examples of the electrolyte include acids such as H ₂ SO ₄ , HCl, and HNO ₃ , lithium ions (Li ⁺ ) and Lewis acid ions (BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , AsF ₆ ⁻ , CF ₃ SO _3). ^-, BPh ₄ ^-.: salt consisting (Ph phenyl group) and, and, a mixed salt, is preferably exemplified Moreover, sodium ion, potassium ion, cations and Lewis acid ions tetraalkylammonium ions, etc. It is desirable that the salt is sufficiently dehydrated and deoxygenated by heating under reduced pressure or the like.

  Examples of the solvent for the electrolyte include acetonitrile, benzonitrile, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethylformamide, tetrahydrofuran, nitrobenzene, dichloroethane, diethoxyethane, 1,2-dimethoxyethane, chlorobenzene, and γ. -Butyrolactone, dioxolane, sulfolane, nitromethane, dimethylsulfide, dimethylsulfoxide, methyl formate, 3-methyl-2-oxazolidinone, 2-methyltetrahydrofuran, 3-propylsidone, sulfur dioxide, phosphoryl chloride, thionyl chloride, sulfuryl chloride, Alternatively, a mixture of these can be suitably used.

  The solvent is, for example, dehydrated with activated alumina, molecular sheep, phosphorus pentoxide, potassium chloride, or the like, or, depending on the solvent, is subjected to distillation in the presence of an alkali metal in an inert gas to remove impurities and also to dehydrate. preferable.

  In order to prevent leakage of the electrolytic solution, it is preferable to gel. As the gelling agent, it is desirable to use a polymer that swells by absorbing the solvent of the electrolytic solution. As such a polymer, polyethylene oxide, polyvinyl alcohol, polyacrylamide and the like are suitably used.

<Battery shape and structure>
Examples of the shape of the battery in the present invention include a flat shape, a cylindrical shape, a rectangular parallelepiped shape, and a sheet shape. The structure of the battery includes, for example, a single-layer type, a multilayer type, a spiral type, and the like. Among them, a spiral cylindrical battery is preferable because it has a feature that the electrode area can be increased by winding a separator between the negative electrode and the positive electrode, and a large current can flow during charging and discharging. . Further, a rectangular parallelepiped battery is preferable because it has a feature that a storage space of a device for storing a secondary battery can be effectively used.

  Hereinafter, an example of the shape and structure of the battery will be described in more detail with reference to FIGS. 5 and 6. FIG. 5 is a schematic sectional view of a single-layer flat battery, and FIG. 6 is a schematic sectional view of a spiral cylindrical battery.

  5 and 6, 400 is a negative electrode current collector, 401 is a negative electrode active material layer, 402 is a negative electrode, 403 is a positive electrode active material layer, 404 is a positive electrode current collector, 405 is a negative electrode terminal (negative electrode cap), and 406 is A positive electrode can, 407 is a separator, 408 is a positive electrode, 410 is an insulating packing, and 411 is an insulating plate.

  An example of a method of assembling the configuration of the battery shown in FIGS. 5 and 6 will be described.

  First, a separator 407 is interposed between the negative electrode active material layer 401 and the formed positive electrode active material layer 403, and the resultant is assembled into the positive electrode can 406. At this time, in the battery shown in FIG. 6, the active material layer 401 and the positive electrode active material layer 403 are wound around the negative electrode with the separator 407 interposed therebetween.

  Next, after the electrolyte is injected into the positive electrode can, the negative electrode cap 405 is disposed on the positive electrode can via the insulating packing 410.

  Subsequently, the battery is completed by caulking at least a part of the positive electrode can and / or the negative electrode cap.

  The above-described preparation of the lithium battery material and assembly of the battery are desirably performed in dry air from which moisture has been sufficiently removed or in a dry inert gas.

<Insulation packing>
As the material of the insulating packing 410 in the present invention, for example, polyolefin, fluorine resin, polyamide resin, polysulfone resin, and various rubbers can be used. As a method for sealing the battery, a method such as a glass tube, an adhesive, welding, or soldering can be used other than “caulking” using a gasket such as an insulating packing as illustrated.

  As the material of the insulating plate 411 shown in FIG. 6, various organic resin materials and ceramics which are chemically stable with respect to an electrolyte or a use environment (for example, temperature) of the battery are preferably used.

  The outer can (housing) in FIGS. 5 and 6 corresponds to the positive electrode can 406 and the negative electrode cap 405 of the battery. As a material for the outer can, stainless steel is preferably used. Among them, a titanium-clad stainless steel plate, a copper-clad stainless steel plate, a nickel-plated steel plate and the like are particularly preferable.

  In FIGS. 5 and 6, since the positive electrode can 406 and the negative electrode cap 405 also serve as the battery case (housing), the above-described stainless steel is preferable from the viewpoint of having sufficient strength. However, when the positive electrode can and the negative electrode cap do not double as the battery case, that is, when the strength is not so required, the material of the battery case is not only stainless steel but also various metals or alloys such as zinc, plastic such as polypropylene, or A composite material of metal or glass fiber and plastic is exemplified.

  The battery is usually provided with a safety valve as a safety measure when the internal pressure of the battery increases. As the safety valve, for example, rubber, a spring, a metal ball, a burst foil, or the like can be used. Alternatively, the strength of a part of the battery may be reduced so that when the internal pressure becomes abnormally high, the internal pressure which is damaged first may be released.

  Hereinafter, the present invention will be described in detail based on examples. Note that the present invention is not limited to these examples.

Example 1
In the present invention, a lithium secondary battery having the structure shown in FIG. 5 was manufactured. An aluminum foil was used for the negative electrode, and a porous hollow positive electrode active material was used for the positive electrode.

  Hereinafter, with reference to FIG. 5, a description will be given of a procedure for manufacturing each component of the battery and an assembly of the battery.

(1) Production procedure of negative electrode After removing the natural oxide film on the surface of the aluminum foil by etching with a 4 wt% aqueous sodium hydroxide solution, neutralizing with a 20 wt% aqueous nitric acid solution, washing with water, and drying at 150 ° C. under reduced pressure to produce a negative electrode. did.

(2) Preparation of Positive Electrode First, a manganese acetate 2M (mol / 1) aqueous solution and a 20 g / l hexane solution of a nonionic surfactant (polyoxyethylene sorbitan triolate) were mixed at a volume ratio of 1: 2, and an emulsifier was prepared. The mixture was emulsified at 4,000 rpm for 1 minute to prepare an emulsion, and a 1M aqueous solution of lithium citrate was added dropwise to the emulsion over 30 minutes.

  Next, after the oil layer was separated and removed from the solution prepared above by a centrifugal separator, the oil layer was dried with a spray dryer, and then calcined at 400 ° C. in air to prepare a porous lithium-manganese oxide powder.

  Subsequently, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder are mixed with the porous lithium-manganese oxide powder obtained above, and N-methylpyrrolidone is added to prepare a paste. did.

  Further, the paste obtained above was applied to an aluminum foil and dried, and then dried under reduced pressure at 150 ° C. to produce a positive electrode.

  Observation from a scanning electron microscope showed that the lithium-manganese oxide powder obtained above had many pores and a hollow structure.

(3) Preparation Procedure of Electrolyte First, a solvent was prepared by mixing equal amounts of ethylene carbonate (EC) and dimethyl carbonate (DMC) from which water had been sufficiently removed.

  Next, a solution obtained by dissolving lithium tetrafluoroborate 1M (mol / l) in the solvent obtained above was used as an electrolytic solution.

(4) Separator A microporous film of polyethylene was used for the separator.

(5) Assembly of Battery First, a separator holding an electrolyte was sandwiched between a negative electrode and a positive electrode, and a titanium clad stainless steel material was inserted into a positive electrode can.

  Subsequently, an insulating packing made of polypropylene was placed, and a negative electrode cap made of a titanium clad stainless steel material was put thereon, and then the positive electrode can and the negative electrode cap were crimped to produce a lithium secondary battery. Note that the manufactured battery can be used by charging.

  Hereinafter, performance evaluation of the manufactured battery will be described. The performance evaluation was performed on the energy density per unit volume of the battery and the cycle life obtained in the charge / discharge cycle test.

  The cycle test conditions were based on the electric capacity calculated from the positive electrode active material as a reference, and a cycle consisting of charging and discharging of 1 C (current of one time of capacity / time) and a 30-minute rest time was defined as one cycle. The charge / discharge test of the battery used HJ-106M manufactured by Hokuto Denko. The charge / discharge test was started from charging, the battery capacity was the discharge amount in the third cycle, and the cycle life was the number of cycles that was less than 60% of the battery capacity. Further, the cut-off voltage for charging was set to 4.5 V, and the cut-off voltage for discharging was set to 2.5 V.

Comparative Example 1
In this example, a secondary battery was manufactured in the same manner as in Example 1 except that the cathode material was prepared by a method different from that in Example 1 as described below.

First, a 1M aqueous solution of lithium citrate was dropped and reacted with a 2M (mol / l) aqueous solution of manganese acetate over 30 minutes.

  Next, the solution prepared in the above step was dried with a spray drier, and then calcined at 400 ° C. in the air to prepare a lithium-manganese oxide powder.

  Further, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder were mixed with the lithium-manganese oxide powder obtained in the above step, and N-methylpyrrolidone was added to prepare a paste.

  Subsequently, the paste obtained in the above step was dried under reduced pressure at 150 ° C. after drying the aluminum foil to prepare a positive electrode.

  In the observation from the scanning electron microscope, no hollow structure was observed in the obtained lithium-manganese oxide powder.

  The other points were the same as in Example 1.

  Table 1 summarizes the performance evaluations of the lithium secondary batteries produced in Example 1 and Comparative Example 1. However, the evaluation results of the cycle life, the charge / discharge efficiency, which is the ratio of the amount of discharge electricity to the amount of charge electricity, and the energy density per unit volume of the battery (discharge capacity) are the values of Example 1 and the values of Comparative Example 1. Normalized and described as 1.0.

  As can be seen from Table 1, by employing the positive electrode active material utilizing the porous hollow structure in the secondary battery as shown in Example 1, the cycle life is increased, the charge / discharge efficiency is increased, and the energy is increased. It was found that a lithium secondary battery having a high density was obtained.

Example 2
In this example, a lithium secondary battery having the structure shown in FIG. 5 was similarly manufactured. Example 2 is different from Example 1 in that a positive electrode manufactured using a porous active material in which a conductor is provided in a hollow portion of a hollow porous active material is used.

  Hereinafter, a procedure for manufacturing the positive electrode will be described.

Preparation procedure of positive electrode First, nickel fine powder was dispersed and mixed with a 2M (mol / 1) aqueous solution of manganese acetate and a 20 g / l hexane solution of a nonionic surfactant (polyoxyethylene sorbitan triolate) at a volume ratio of 1: 2. Then, the mixture was emulsified for 1 minute at 4000 rotations using an emulsifier to prepare an emulsion, and a 1 M aqueous solution of lithium hydroxide was dropwise added to the emulsion over 30 minutes.

  Next, after separating and removing the oil layer of the solution prepared in the above step by a centrifugal separator, the aqueous layer and the precipitated layer are dried together with a spray drier, and then calcined at 400 ° C. in air to form a porous lithium-manganese oxide. A flour was prepared.

  Subsequently, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder are mixed with the porous lithium-manganese oxide powder obtained in the above step, and N-methylpyrrolodone is added to paste. Was prepared.

  Further, the paste obtained in the above step was applied to an aluminum foil and dried, and then dried at 150 ° C. under reduced pressure to produce a positive electrode.

  In other respects, a secondary battery was manufactured in the same manner as in Example 1.

Comparative Example 2
In this comparative example, only the method for preparing the positive electrode material was different from that in Example 2 as follows.

  First, a 1M aqueous solution of lithium hydroxide was dropped and reacted with a 2M (mol / l) aqueous solution of manganese acetate from which nickel fine powder had been separated over 30 minutes.

  Next, the solution prepared in the above step was dried with a spray drier and then calcined at 400 ° C. in air to prepare a lithium-manganese oxide powder.

  Subsequently, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder were mixed with the lithium-manganese oxide obtained in the above step, and N-methylpyrrolidone was added to prepare a paste.

  Further, the paste obtained in the above step was applied to an aluminum foil and dried, and then dried at 150 ° C. under reduced pressure to produce a positive electrode.

  In other respects, a secondary battery was manufactured in the same manner as in Example 2.

  Table 2 summarizes the performance evaluations of the lithium secondary batteries produced in Example 2 and Comparative Example 2. However, the evaluation results regarding cycle life, charge / discharge efficiency, and energy density (discharge capacity) per unit volume of the battery were described by standardizing the value of Example 1 and the value of Comparative Example 2 as 1.0. The test method followed that of Example 1.

  As described above, by employing the positive electrode active material utilizing the porous hollow structure in the secondary battery as shown in Example 2, the cycle life is increased, the charge / discharge efficiency is increased, and the high energy density is improved. It was found that a lithium secondary battery having the above was obtained.

Reference Example 1
Also in this reference example, a lithium secondary battery having the structure shown in FIG. 5 was manufactured. The point that the porous hollow carbon is used as the negative electrode active material is significantly different from the first and second embodiments. Except for the negative electrode and the positive electrode, the procedure was the same as in Example 1.

  Hereinafter, only the procedure for producing the negative electrode and the positive electrode of the battery will be described.

(1) Preparation procedure of negative electrode First, 30 g / l of sorbitan monourate is added to a solution of polyfurfuryl alcohol in tetrahydrofuran, and water and 20 atomic% of sodium tetraphenylborate with respect to carbon atoms of polyfurfuryl alcohol are further mixed. The mixture was emulsified at 3000 rpm for 1 minute using an emulsifier to prepare an emulsion.

  Next, the emulsion obtained in the above step was dropped into ethanol, and the precipitate was dried and then calcined at 800 ° C. under argon gas to prepare a carbon powder.

  Subsequently, 5 wt% of polyvinylidene fluoride powder was mixed with the carbon powder obtained in the above step, and N-methylpyrrolidone was added to prepare a paste.

  Further, the paste obtained in the above step was applied to a copper foil and dried, and then dried at 150 ° C. under reduced pressure to produce a negative electrode.

  Observation from a scanning electron microscope revealed that the carbon powder obtained in the above step had many pores and a hollow structure. Further, as a result of elemental analysis, it was found that the carbon powder obtained in the above step contained boron.

(2) Preparation of positive electrode First, electrolytic manganese dioxide and lithium carbonate were mixed at a molar ratio of 1: 0.4, and then heat-treated at 800 ° C. to prepare a lithium-manganese oxide.

  Next, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder were mixed with the lithium-manganese oxide prepared in the above step, and N-methylpyrrolidone was added to prepare a paste.

  Subsequently, the paste obtained in the above step was applied to an aluminum foil and dried, and then dried at 150 ° C. under reduced pressure to produce a positive electrode.

  In other respects, a secondary battery was manufactured in the same manner as in Example 1.

Comparative Example 3
In this example, a secondary battery was manufactured by differentiating only the method of preparing the negative electrode active material from Reference Example 1.

  First, 5 wt% of polyvinylidene fluoride powder was mixed with natural graphite fine powder, and N-methylpyrrolidone was added to prepare a paste.

  Next, the paste obtained in the above step was applied to a copper foil and dried, and then dried at 150 ° C. under reduced pressure to produce a negative electrode.

  In the observation from the scanning electron microscope, no hollow structure was observed in the natural graphite powder.

  Other points were the same as in Reference Example 1.

  Table 3 summarizes the performance evaluations of the lithium secondary batteries produced in Reference Example 1 and Comparative Example 3. However, the evaluation results regarding the cycle life, charge / discharge efficiency, and energy density (discharge capacity) per unit volume of the battery were described by standardizing the value of Reference Example 1 and the value of Comparative Example 3 as 1.0.

  As described above, by adopting the negative electrode active material using the porous hollow structure in the secondary battery as shown in Reference Example 1, the cycle life is long, the charge / discharge efficiency is increased, and the high energy density is improved. It was found that a lithium secondary battery having the above was obtained.

Example 3
Also in this example, a lithium secondary battery having the structure shown in FIG. 5 was manufactured. Reference Example 1 differs from Reference Example 1 in that a negative electrode manufactured using porous hollow carbon prepared by a different preparation method from Reference Example 1 was used.

  Hereinafter, a procedure for manufacturing the negative electrode will be described.

(1) Production procedure of negative electrode First, charcoal was oxidized in air at 300 ° C., then immersed in an aqueous solution of potassium hydroxide, etched, and dried under reduced pressure. After firing at 2000 ° C. in a nitrogen gas atmosphere, the powder was pulverized to prepare a carbon powder.

  Next, 5 wt% of polyvinylidene fluoride was mixed with the carbon powder obtained in the above step, and N-methylpyrrolidone was added to prepare a paste.

  Subsequently, the paste obtained in the above process was applied to a copper foil and dried, and then dried at 150 ° C. under reduced pressure to produce a negative electrode.

  Observation from a scanning electron microscope showed that the carbon powder obtained in the above step had many pores and a hollow tubular structure.

  In other respects, a secondary battery was manufactured in the same manner as in Reference Example 1.

  Table 4 summarizes the performance evaluations of the lithium secondary batteries produced in Example 3 and Comparative Example 3. However, the evaluation results regarding the cycle life, the charge / discharge efficiency, and the energy density (discharge capacity) per unit volume of the battery were described by standardizing the value of Example 3 with the value of Comparative Example 3 being 1.0.

  As described above, by employing the negative electrode active material using the porous hollow structure in the secondary battery as shown in Example 3, the cycle life is increased, the charge / discharge efficiency is increased, and the high energy density is improved. It was found that a lithium secondary battery having the above was obtained.

Example 4
Also in this example, a lithium secondary battery having the structure shown in FIG. 5 was manufactured. In this example, a positive electrode manufactured using a porous hollow positive electrode active material and a negative electrode manufactured using porous hollow carbon were used.

  Hereinafter, a procedure for manufacturing the negative electrode and the positive electrode will be described.

(1) Production procedure of negative electrode First, 30 g / 1 of sorbitan monourate and water were added to a solution of polyfurfuryl alcohol in tetrahydrofuran and emulsified at 3000 rpm for 1 minute using an emulsifier to prepare an emulsion.

  Next, the emulsion obtained in the above step was dropped into ethanol, and the precipitate was dried and calcined at 700 ° C. under argon gas to prepare a carbon powder.

  Subsequently, 5 wt% of polyvinylidene fluoride powder was mixed with the carbon powder obtained in the above step, and N-methylpyrrolidone was added to prepare a paste.

  Further, the paste obtained in the above step was applied to a copper foil and dried, and then dried at 150 ° C. under reduced pressure to produce a negative electrode.

  Observation from a scanning electron microscope revealed that the carbon powder obtained in the above step had many pores and a hollow structure.

(2) Preparation of Positive Electrode First, a 2 M (mol / l) aqueous solution of nickel acetate was mixed with a 20 g / l hexane solution of a nonionic surfactant (polyoxyethylene sorbitan triolate) at a volume ratio of 1: 1. The mixture was emulsified at 4,000 rpm for 1 minute to prepare an emulsion, and a 1M aqueous solution of lithium citrate was added dropwise to the emulsion over 30 minutes.

  Next, the solution prepared in the above step was separated and removed from the oil layer by a centrifugal separator, dried with a spray dryer, and then calcined at 650 ° C. in air to prepare a porous lithium-nickel oxide powder.

  Subsequently, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder were mixed with the porous lithium-nickel oxide powder obtained in the above step, and N-methylpyrrolidone was added to paste the paste. Prepared.

  Further, the paste obtained in the above step was applied to an aluminum foil and dried, and then dried at 150 ° C. under reduced pressure to produce a positive electrode.

  Observation from a scanning electron microscope revealed that the lithium-nickel oxide powder obtained in the above step had many pores and a hollow structure.

  In other respects, a secondary battery was manufactured in the same manner as in Example 1.

Comparative Example 4
In this example, a positive electrode was prepared by preparing a positive electrode active material by a method different from that in Example 4. The same negative electrode as in Comparative Example 3 was used as the negative electrode.

First, nickel carbonate and lithium nitrate were mixed at a molar ratio of 1: 1 and then heat-treated at 650 ° C. to prepare a lithium-nickel oxide.

  Next, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder were mixed with the lithium-nickel oxide prepared in the above step, and then N-methylpyrrolidone was added.

  Subsequently, the paste obtained in the above step was applied to an aluminum foil and dried, and then dried at 150 ° C. under reduced pressure to produce a positive electrode.

  According to observation by a scanning electron microscope, no hollow structure was observed in the lithium-nickel oxide powder obtained in the above step.

  In other respects, a secondary battery was manufactured in the same manner as in Example 1.

  Table 5 summarizes the performance evaluations of the lithium secondary batteries produced in Example 5 and Comparative Example 4. However, the evaluation results regarding the cycle life, charge / discharge efficiency, and energy density (discharge capacity) per unit volume of the battery were described by standardizing the value of Example 4 and the value of Comparative Example 4 as 1.0.

  As described above, by employing the positive electrode active material using the porous hollow structure and the negative electrode active material using the porous hollow structure in the secondary battery as shown in Example 4, the cycle life is long and the It was found that the discharge efficiency was improved and a lithium secondary battery having a high energy density was obtained.

Reference Example 2
Also in this reference example, a lithium secondary battery having the structure shown in FIG. 5 was manufactured. As the negative electrode, a negative electrode manufactured using a porous hollow metal powder was used. The same positive electrode as described in Comparative Example 4 was used as the positive electrode.

Preparation procedure of negative electrode First, a 3 M (mol / l) aqueous solution of copper nitrate was mixed with a 30 g / 1 hexane solution of a nonionic surfactant (polyoxyethylene sorbitan triolate) at a volume ratio of 1: 2, and an emulsifier was used. The mixture was emulsified at 4000 rotations for 1 minute to prepare an emulsion, and a 1M aqueous solution of sodium hydroxide was added dropwise to the emulsion over 30 minutes.

  Next, the solution prepared in the above step is separated and removed from the oil layer by a centrifugal separator, washed with water by decantation, dried by a spray dryer together with the water layer and the precipitated layer, and then calcined at 350 ° C. An oxide powder was prepared.

  Subsequently, the porous copper oxide powder obtained in the above step is reduced at 400 ° C. in a hydrogen gas atmosphere to prepare a porous hollow copper powder, and then a slight amount of oxygen is introduced to slightly oxidize the surface and the surface is slightly oxidized. A film was formed.

  Further, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polyvinylidene fluoride powder were mixed with the porous hollow copper powder obtained in the above step, and N-methylpyrrolidone was added to prepare a paste.

  Next, the paste obtained in the above step was applied to a copper foil and dried, and then dried at 150 ° C. under reduced pressure to produce a negative electrode.

  Observation from a scanning electron microscope revealed that the copper powder obtained in the above step had many pores and a hollow structure.

  In other respects, a secondary battery was manufactured in the same manner as in Example 1.

Comparative Example 5
In this example, a negative electrode was manufactured by a method different from that of Reference Example 2. The same positive electrode as that used in Comparative Example 4 was used as the positive electrode.

Production procedure of negative electrode First, 3 wt% (weight) of carbon powder of acetylene black and 5 wt% of polypyridinene fluoride powder were mixed with copper powder, and N-methylpyrrolidone was added to prepare a paste.

  Next, the paste obtained in the above step was applied to a copper foil and dried, and then dried at 150 ° C. under reduced pressure to produce a negative electrode. In other respects, a secondary battery was manufactured in the same manner as in Reference Example 2.

  Table 6 summarizes the performance evaluations of the lithium secondary batteries produced in Reference Example 2 and Comparative Example 5. However, the evaluation results regarding the cycle life, charge / discharge efficiency and energy density (discharge capacity) per unit volume of the battery were described by standardizing the value of Reference Example 2 and the value of Comparative Example 5 as 1.0.

  As described above, by adopting the negative electrode active material using the porous hollow structure in the secondary battery as shown in Reference Example 2, the cycle life is long, the charge / discharge efficiency is increased, and the high energy density is improved. It was found that a lithium secondary battery having the above was obtained.

  In Examples 1 to 4, a lithium-manganese oxide or a lithium-nickel oxide was used as the positive electrode active material in order to evaluate the performance of the negative electrode. However, the present invention is not limited to this, and various kinds of positive electrode active materials described above such as lithium-cobalt oxide and lithium-vanadium oxide can be adopted.

  In addition, as for the electrolytic solution, one type was used in Examples 1 to 4, but the present invention is not limited to this.

  Further, the present invention is not limited to the above-described battery shape and the like.

  That is, the present invention can be appropriately modified and combined within the scope of the present invention.

FIGS. 1A to 1C are conceptual schematic cross-sectional views of an active material having a porous hollow structure. It is a conceptual perspective view of the active material of a spherical-shaped structure shown to FIG. 1 (a)-(c). FIG. 2 is a schematic cross-sectional view for explaining a preferred example of an electrode configuration using an active material having a porous hollow structure. FIG. 4 is a schematic configuration diagram for explaining a basic configuration of a battery using the electrodes shown in FIG. 3. FIG. 2 is a schematic partial cross-sectional view for explaining an example of a single-layer flat battery. FIG. 2 is a schematic partial cross-sectional view illustrating an example of a spiral cylindrical battery. It is a conceptual perspective view of the active material of a tubular structure.

Explanation of reference numerals

Reference Signs List 100 active material constituent material 101 pore 102 hollow portion 103 skin layer 104 conductor provided in hollow portion 200 current collector 201 porous hollow active material 202 binder 203 active material layer 204 positive electrode or negative electrode 301, 402 negative electrode 302, 408 Positive electrode 303 Electrolyte 304 Separator 305 Negative terminal 306 Positive terminal 307 Battery case 401 Negative active material 402 Negative electrode 403 Positive active material 404 Positive current collector 405 Negative cap (negative terminal)
406 Positive electrode can (positive electrode terminal)
407 Separator holding electrolyte 408 Positive electrode 410 Insulating packing 411 Insulating plate

Claims (9)

  A non-ionic surfactant is dissolved in an organic solvent that is hardly soluble or insoluble in water, and an aqueous solution of a transition metal salt is mixed to prepare an emulsion. A method for producing a positive electrode active material, comprising a step of obtaining a lithium-transition metal oxide having a structure.   A method for manufacturing a secondary battery using lithium having at least a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte, comprising a non-ionic interface in a water-insoluble or insoluble organic solvent. After dissolving the activator and mixing an aqueous transition metal salt solution to prepare an emulsion, a Li salt or LiOH aqueous solution is reacted, and dried and fired to obtain a porous hollow structure lithium-transition metal oxide, thereby obtaining a positive electrode A method for manufacturing a secondary battery using lithium, comprising a step of manufacturing an active material.   Air or a liquid with no affinity for polymer was passed through the center of the double cylindrical nozzle, and a molten polymer material or a dissolved polymer material was passed through the outer cylindrical nozzle and spun to produce a polymer hollow fiber And baking and pulverizing to obtain carbon having a porous hollow structure.   A method for producing a negative electrode active material, comprising a step of obtaining a carbon having a porous hollow structure by carbonizing a plant, performing an oxidation treatment and an alkali etching treatment, and firing and pulverizing the plant.   A non-ionic surfactant is dissolved in an organic solvent that is hardly soluble or insoluble in water, and an aqueous solution of a transition metal salt is mixed to prepare an emulsion. A method for producing a negative electrode active material, comprising a step of obtaining a lithium-transition metal oxide having a structure.   A non-ionic surfactant is dissolved in an organic solvent that is hardly soluble or insoluble in water, and an aqueous solution of a transition metal salt is mixed to prepare an emulsion. Obtaining a lithium-transition metal oxide having a structure, and subjecting the lithium-transition metal oxide having a porous hollow structure obtained in the step to heat treatment in a reducing atmosphere of hydrogen gas or exposure to hydrogen plasma for reduction. Obtaining a metal particle having a porous hollow structure by the above method.   The method for producing a negative electrode active material according to claim 6, further comprising a step of subjecting the surface of the metal particles to any one of an oxidation treatment, a halogenation treatment, and a nitridation treatment.   After dispersing the organic polymer particles in the electroless plating solution and forming a metal film on the surface of the organic polymer particles by a reduction reaction, the organic polymer particles coated with the obtained metal film are dissolved in a solvent. A method for producing a negative electrode active material, comprising a step of dispersing and dissolving and removing an organic polymer to obtain metal particles having a porous hollow structure.   A method for manufacturing a secondary battery using lithium having at least a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and an electrolyte, the method according to any one of claims 3 to 8. A method for producing a secondary battery using lithium, comprising a step of producing a negative electrode active material by a method.

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