JP5239209B2 - Method for producing positive electrode for lithium battery - Google Patents

Description

The present invention relates to a lithium battery, a positive electrode for a lithium battery, and a method for producing the same, and more specifically, production of a positive electrode for a lithium battery that can be easily and inexpensively provided using a raw material having low chemical reactivity. It is about the method.

In the era when a variety of batteries are mounted on portable electronic devices, the batteries are always required to be lighter, smaller or have higher energy density. For example, secondary batteries for power supplies such as IC cards and tags Is required. Secondary batteries used in the above IC cards and the like are pursued to the utmost in miniaturization and thinning, and are being developed by integrating thin film technology and battery material technology. For example, a method is disclosed in which the positive electrode of an all solid electrolyte lithium secondary battery is composed of a lithium composite oxide, and the negative electrode is composed of a carbon material and metallic lithium (Patent Document 1). As a film forming method of lithium manganate (LiMn ₂ O ₄ ) as an example of the positive electrode, the following method is exemplified in the examples of the above-mentioned document.

Evaporation source is lithium and manganese in graphite or alumina crucible, respectively. Lithium is resistance heating vacuum deposition method (current 100A) and manganese is electron beam vacuum deposition method (electron acceleration voltage 30kV, emission current 600mA). ) In a mixed gas atmosphere of Ar 50% + oxygen 50% of 1 × 10 ⁻⁴ Torr. According to this method, a thin film positive electrode of a lithium secondary battery can be obtained by a vapor phase method.
JP 2004-127743 A

According to the film forming method described above, however, metallic manganate is formed in an oxygen atmosphere using metallic manganese as the manganese vapor deposition material and metallic lithium as the lithium evaporation material. In the film formation method described above, care must be taken in handling powdered metal manganese, etc., but in other cases, metal lithium is particularly chemically reactive, requires care in handling, and is expensive. There is a problem of raising costs. An object of this invention is to provide the manufacturing method of the positive electrode for lithium batteries which can be easily manufactured using the raw material which is cheap and has low chemical activity.

  The manufacturing method of the positive electrode for lithium batteries of this invention is a manufacturing method of the positive electrode for lithium batteries which forms the positive electrode which consists of a lithium manganate or the partial substitution type compound of lithium manganate by a gaseous-phase method. In this production method, in order to form lithium manganate or a partially substituted compound of lithium manganate on a substrate, manganese oxide is placed in a vapor deposition source container and energy for evaporation is introduced in an oxygen-containing atmosphere. Before or after supplying the energy for evaporation, the manganese oxide is heated to a temperature of 350 ° C. or more and 500 ° C. or less immediately after the manganese oxide is put into the deposition source vessel or immediately before the manganese oxide is put into the deposition source vessel. The manganese oxide is heated to a temperature of 350 ° C. or higher and 500 ° C. or lower and kept in a dry atmosphere with a dew point of 0 ° C. or lower before entering the evaporation source.

According to the above method, since manganese oxide is used as the manganese raw material, it is chemically stable without being ignited in a powder state, and is inexpensive. Note that manganese oxide is mainly MnO ₂ is (manganese dioxide) is subject, MnO (manganese monoxide), _Mn 2 _{O 3} (manganese sesquioxide), MnO ₂ (manganese _dioxide), Mn _{2 O} 7 ( Dimanganese heptaoxide), Mn ₃ O ₄ (trimanganese tetroxide) may be used. The lithium manganate may be Li _{1 + x} Mn _2−x O ₄ (x = 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ including LiMn ₂ O ₄ or the like. The partially substituted compound of lithium manganate is Li _{1 + x} Mn _2−xy M _y O ₄ (M is at least one element selected from Ni, Co, Cr, Cu, Fe, Al, and Mg. _X = 0~0.33, y = 0~0.33,2-x- y> 0), at least the _{LiMn 2-x M x O 2} (M chosen Co, Ni, Fe, Cr, Zn, than Ta One element, x = 0.01 to 0.1), LiMn ₃ MO ₃ (M is at least one element selected from Co, Ni, Fe, Cu, Zn), and the like. Further, the oxygen-containing atmosphere may be an atmosphere containing only oxygen.

The manganese oxide is heated to a temperature of 350 ° C. or more and 500 ° C. or less immediately after the manganese oxide is put into the deposition source container or immediately before the manganese oxide is put into the deposition source container, or before the manganese oxide is put into the deposition source. Manganese oxide must be heated to a temperature of 350 ° C. or higher and 500 ° C. or lower and kept in a dry atmosphere with a dew point of 0 ° C. or lower. When manganese oxide is left in the air, since the _MnO 2 · _H 2 O (manganese oxide monohydrate or manganite) or manganese Mn _{(OH) 2,} etc. hydroxide is easily formed, contains _{H 2} O or OH If evaporating energy such as an electron beam is input with the raw material, problems such as bumping occur. According to this method, H ₂ O of the hydrate can be removed by heating, and problems such as bumping can be avoided. When the heat treatment temperature is less than 350 ° C., moisture is not sufficiently removed, and when it exceeds 500 ° C., oxygen is released and the manganese dioxide raw material is altered.

Furthermore, at least one of lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), and lithium nitrate (LiNO ₃ ) is put in the vapor deposition source container for the lithium compound, and the manganese oxide vapor deposition source container The evaporation energy can be input into the vapor deposition source container for the lithium compound in accordance with the timing when the evaporation energy is input. According to this method, a chemically stable and inexpensive material can be used for the lithium raw material of lithium manganate as the positive electrode active material. The lithium raw material does not need to be handled in a dry atmosphere, and can facilitate the production of the positive electrode.

  The transition metal or at least one of the transition metal compounds as a substitution element in the above partially substituted compound of lithium manganate is placed in a vapor deposition source container for the transition metal, and evaporated in the vapor deposition source container for manganese oxide. In accordance with the time when energy is input, the energy for evaporation can be input into the vapor deposition source container for the transition metal. According to this method, the transition metal, which is a substitution element of the partially substituted compound of lithium manganate constituting the positive electrode active material, can be made an inexpensive material.

  Evaporation energy input into the above-described vapor deposition source container for lithium compounds and / or transition metal deposition source containers should be the same type of energy as the evaporation energy input into the manganese oxide vapor deposition source container. Can do. According to this method, the number of evaporation energy emission sources can be suppressed, and the structure of the film forming apparatus for forming lithium manganate can be simplified.

  The manganese oxide deposition source container also serves as a lithium compound deposition source container and / or transition metal deposition source container, and the manganese oxide deposition source container includes lithium oxide, lithium carbonate, and lithium nitrate. And / or at least one of a transition metal and a compound of the transition metal. According to this method, using one crucible, the energy for evaporation can be input to the one crucible. For this reason, the complicated mechanism which prepares two crucibles and throws in the energy for vaporization becomes unnecessary.

  An electron beam or a laser beam can be used for the evaporation energy. According to this method, the evaporation energy can be obtained by using an electron beam gun or a laser oscillation device that has been well known.

The positive electrode for a lithium battery is manufactured by any one of the manufacturing methods described above, and has the above-described effects.

The lithium battery includes any one of (solid electrolyte, liquid electrolyte, ion conductive polymer and ionic liquid including a lithium ion salt), a negative electrode, and any one of the above positive electrodes for a lithium battery. And a positive electrode manufactured by the manufacturing method.

  Since the above lithium battery can manufacture the positive electrode easily and inexpensively, an inexpensive lithium battery can be assembled. The lithium battery is mainly a secondary battery, but may be a primary battery.

  According to the method for producing a positive electrode for a lithium secondary battery of the present invention, it is possible to easily produce a positive electrode for a lithium secondary battery using an inexpensive raw material having low chemical activity.

  FIG. 1 is a diagram showing a method for producing a positive electrode for a lithium battery in an embodiment of the present invention. FIG. 2 is a view showing a positive electrode body 10 including a base material 1 and a positive electrode 2 for a lithium battery, and FIG. 3 is a view showing a lithium battery 50 including the positive electrode body 10. First, it demonstrates limiting to the manufacturing method of the positive electrode 2 for lithium batteries. The positive electrode 2 for a lithium battery is formed on a conductive substrate 1. For the conductive substrate 1, a conductive material such as aluminum, aluminum alloy, copper, copper alloy, and stainless steel can be used.

  Manganese oxide has a risk of bumping due to the moisture contained when evaporation energy is input in the crucible, so that manganese oxide is in the range of 350 ° C to 500 ° C in air to prevent bumping. Then, heat treatment is performed for 3 to 10 hours (step S1 in FIG. 1). Thereafter, in order to prevent moisture adsorption, the heat-treated manganese oxide is stored in a dry atmosphere (dew point range: 0 ° C. or lower) (step S2). This step S2 can be omitted if the period after the above heat treatment is put into the crucible and the energy for evaporation is short (in the case of heat treatment in the crucible or left in the crucible for a short time).

Next, the positive electrode 2 made of lithium manganate is formed on the substrate 1 by vapor deposition in the film forming chamber 15 shown in FIG. The above manganese oxide is put in the crucible 61, and at least one raw material of lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ) and lithium nitrate (LiNO ₃ ) prepared in advance is put in the crucible 62. 4 is disposed in the film forming chamber 15 shown in FIG. 4 (step S3). An electron beam is used as the energy for evaporation, and the electron beam is irradiated into the crucibles 61 and 62 in an oxygen atmosphere by an electron beam vacuum deposition method (step S4). The range of electron beam vacuum deposition conditions is preferably an electron acceleration voltage range of 8 to 30 V and an electron current range of 40 mA to 2 A. When the evaporation from the crucibles 61 and 62 is stabilized, the shutter 52 is opened, and lithium manganate is deposited on the base material 1 (step S5).

  In step S3, the lithium compound and manganese oxide may be put in separate crucibles or mixed and put in one crucible. In the case of using one crucible, it is only necessary to input energy such as an electron beam into the one crucible, so that the apparatus configuration can be simplified and the energy efficiency can be increased. The crucible is preferably made of water-cooled copper, alumina, or graphite. The atmosphere is preferably an oxygen atmosphere (1 sccm) regardless of the number of crucibles used.

The positive electrode body 10 shown in FIG. 2 can be manufactured by the above process. According to the above process, the raw material manganese oxide enters the crucibles 61 and 62 in a state where moisture has been removed through heat treatment, so there is no risk of bumping, easy handling, and the raw material manganese oxide itself, It is cheaper than manganese. In addition, lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ) and lithium nitrate (LiNO ₃ ) are chemically stable, easy to handle, and have no hygroscopicity, and therefore are heat-treated. There is no need. Further, the lithium compound is less expensive than lithium alone. As a result, it is possible to obtain both economical costs for the raw materials and economical costs for the manufacturing process.

With respect to the deposited thin film of lithium manganate, the crystal structure can be analyzed by X-ray diffraction (XRD), and the composition analysis can be performed by inductively coupled plasma (ICP). The lithium manganate corresponds to LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ or the like. Lithium manganate has a wide composition, and all of them have the same effect as the positive electrode of a lithium battery. For this reason, as described above, it is possible to obtain a practically satisfactory positive electrode even by a method in which manganese oxide and the lithium compound are mixed in one crucible and one evaporation energy is input. .

  It was confirmed that the positive electrode 2 for a lithium battery can be produced inexpensively and easily using a chemically stable material by the above-described steps. Next, a method for manufacturing the lithium battery 50 shown in FIG. 3 using the positive electrode body 10 will be described.

(All-solid-state thin film lithium battery)
First, the case where the lithium battery 50 of FIG. 3 is an all-solid-state thin film lithium battery will be described. A solid electrolyte 3 is located on the positive electrode 2, and a negative electrode 4 is located on the electrolyte 3. The solid electrolyte 3 can be formed of, for example, a thin film sulfide electrolyte, and the negative electrode 4 can be formed of lithium. P ₂ S ₅ —Li ₂ S or the like is preferably used as the sulfide electrolyte 3. The sulfide electrolyte 3 is preferably formed by a laser ablation method, that is, a PLD method, or a vacuum deposition method. The carbon boat carrying the carbon boat and _P 2 _{S 5} carrying the Li ₂ S, evaporate the Li ₂ S and _P 2 _{S 5} by passing a current. A crystal resonator is disposed in the vicinity of these evaporation sources. By monitoring the evaporation rate by changing the frequency and feedback controlling the current, the molar concentration ratio of Li ₂ S and P ₂ S ₅ (Li ₂ S / P ₂ S ₅ ) should be 3. The sulfide-based solid electrolyte may contain oxygen. Moreover, you may comprise not a sulfide type solid electrolyte but a Li-P-O-N type.

  Thereafter, lithium of the negative electrode 4 is vacuum deposited. Next, a metal is brought into contact with the conductive base material (positive electrode current collector) 1 and negative electrode lithium 4 to form a current collecting tab. The negative electrode 4 may be lithium alloy Li—Al, Li—Mn—Al, or the like instead of lithium. The tab is partially coated with an insulating resin, and is thermocompression bonded when the resin portion is laminated with aluminum so that the battery is sealed from the atmosphere and moisture and electricity is taken out.

(Liquid electrolyte lithium battery)
The structure of the lithium battery 50 using the electrolytic solution is different from the all-solid lithium battery in that the electrolyte 3 is liquid and a separator (not shown) is required, but the basic configuration is the same as in FIG. This will be described with reference to FIG. As the electrolytic solution constituting the electrolyte 3, an electrolyte dissolved in an organic solvent (non-aqueous solvent) is used. Nonaqueous solvents that can be used for the electrolyte include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, 1, Known organic solvents such as 3-dioxolane can be used singly or in combination of two or more. A known electrolyte such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ or the like of about 0.5 to 2 M can be dissolved in this to form an electrolytic solution. In addition, an ionic liquid (normal temperature molten salt or low temperature molten salt) may be used in place of the above electrolytic solution, and any electrolyte that falls within this category, such as an onium salt such as a pyridinium salt, may be used.

  The above electrolytic solution or ionic liquid is mounted between the positive electrode 2 and the negative electrode 4 that are positioned at an interval using an insulation-coated can or the like so that no leakage occurs, while the separator is disposed. The positive electrode 2 may be made of the above lithium manganate, and the negative electrode 4 may be made of a known material such as lithium or a carbon material. For the separator, for example, a nonwoven fabric of polyolefin resin or a porous film can be used.

(Solid-type lithium ion battery)
In the solid lithium ion battery, a solid electrolyte type ion conductor is used for the electrolyte 3 shown in FIG. As such a polymer having ion conductivity, a polymer obtained by dissolving or dispersing a lithium ion salt in a polymer such as polyethylene oxide (polyethylene glycol) and a derivative thereof, or a copolymer thereof can be used. In other words, polyether-based polymer compounds such as polyethylene oxide and polypropylene oxide, cross-linked polymers of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile and the like, A system in which a lithium salt or an alkali metal salt mainly composed of lithium is combined, or a system in which an organic compound having a high dielectric constant such as propylene carbonate, ethylene carbonate, or γ-butyrolactone is blended can be used. This type of lithium battery does not require a separator.

Example 1
A stainless steel plate was used as the substrate. Manganese oxide was heat-treated at 400 ° C. for 3 hours and then stored in a dry atmosphere. Lithium oxide is placed in a separate crucible from the above-mentioned stored manganese oxide, and each crucible is irradiated with an electron beam in an oxygen atmosphere (oxygen 1 sccm), on the substrate (substrate temperature 500 ° C.). Then, lithium manganate was deposited. The electron beam irradiation conditions were an electron acceleration voltage of 10 V and an electron current of 120 mA.

  When the thickness of the obtained lithium manganate thin film was measured by the step method, the thickness was 1 μm. Moreover, the X-ray-diffraction image about this lithium manganate is shown in FIG. From this X-ray diffraction image, it was confirmed that a spinel structure of lithium manganate was obtained.

(Example 2)
The base material was the same stainless steel plate as in Example 1. Manganese oxide was heat treated at 400 ° C. for 3 hours, and immediately mixed with lithium oxide and placed in one crucible. In an oxygen atmosphere of 1 sccm of oxygen, the crucible was irradiated with an electron beam to deposit lithium manganate on the substrate. The conditions for electron beam irradiation were the same as in Example 1, with an electron acceleration voltage of 10 V and an electron current of 120 mA.

  The thickness of the lithium manganate by the step method was 1 μm. Moreover, it was confirmed from the X-ray diffraction image about this lithium manganate that the spinel structure of lithium manganate was obtained.

With regard to the above-described method for manufacturing a positive electrode for a lithium battery and a positive electrode for a lithium battery according to an embodiment of the present invention, attention should be paid to the following effects and other examples of the manufacturing method.
(1) In the above embodiments, as the positive electrode, it is shown an example manganate lithium, there is also a partial replacement type compound according to the transition metal element of the lithium manganate.
(2) The lithium battery includes a lithium secondary battery and a lithium primary battery.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples of the present invention disclosed above are merely examples, and the scope of the present invention is the implementation of these inventions. It is not limited to the form. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  According to the lithium battery of the present invention, the positive electrode for a lithium battery and the method for producing the same, it is easy to handle because it uses an inexpensive raw material that is chemically stable and does not contain moisture when producing a thin film positive electrode. It can supply products with excellent economic efficiency.

It is a figure which shows the manufacturing method of the positive electrode for lithium batteries in embodiment of this invention. It is a figure which shows the positive electrode for lithium batteries in embodiment of this invention. It is a figure which shows the lithium battery using the positive electrode for lithium batteries of FIG. It is a figure which shows the film-forming apparatus used for the positive electrode for lithium batteries of this invention. It is a figure which shows angle distribution of the X-ray diffraction intensity of the positive electrode manufactured with the manufacturing method of the positive electrode for lithium batteries of embodiment of this invention.

1 base material (positive electrode current collector), 2 positive electrode, 3 electrolyte, 4 negative electrode, 10 positive electrode body, 15 film forming chamber, 50 lithium battery, 52 shutter, 61, 62 crucible.

Claims (6)

A method for producing a positive electrode for a lithium battery, wherein a positive electrode comprising a lithium manganate or a partially substituted compound of lithium manganate is formed by a vapor phase method,
In order to form the lithium manganate or the partially substituted compound of lithium manganate on the substrate, manganese oxide is put into a vapor deposition source container, and the step of supplying energy for evaporation in an oxygen-containing atmosphere is provided.
Before supplying the energy for evaporation, the manganese oxide is heated to a temperature of 350 ° C. or more and 500 ° C. or less immediately after the manganese oxide is placed in the deposition source vessel or immediately before being put into the deposition source vessel, or the oxidation Manufacture of a positive electrode for a lithium battery, wherein the manganese oxide is heated to a temperature of 350 ° C. or higher and 500 ° C. or lower and kept in a dry atmosphere with a dew point of 0 ° C. or lower before the manganese is put into a vapor deposition source. Method.   Furthermore, at least one of lithium oxide, lithium carbonate, and lithium nitrate is put in a vapor deposition source container for a lithium compound, and the lithium lithium is deposited in accordance with a timing when the evaporation energy is put into the manganese oxide vapor deposition source container. 2. The method for producing a positive electrode for a lithium battery according to claim 1, wherein evaporation energy is introduced into a vapor deposition source container for the compound. 3.   The transition metal or at least one of the transition metal compounds as a substitution element in the partially substituted compound of lithium manganate is placed in a vapor deposition source container for the transition metal, and is evaporated in the vapor deposition source container for the manganese oxide. The method for producing a positive electrode for a lithium battery according to claim 1, wherein the energy for evaporation is input into the vapor deposition source container for the transition metal in accordance with the time when the energy is input.   The evaporation energy charged in the vapor deposition source container for the lithium compound and / or the vapor deposition source container for the transition metal is the same type of energy as the vaporization energy charged in the manganese oxide vapor deposition source container. The manufacturing method of the positive electrode for lithium batteries of Claim 3 characterized by the above-mentioned.   The manganese oxide deposition source container also serves as the lithium compound deposition source container and / or the transition metal deposition source container, and the manganese oxide deposition source container contains the lithium oxide, lithium carbonate, and lithium nitrate. 5. The method for producing a positive electrode for a lithium battery according to claim 3, wherein at least one of them and / or at least one of the transition metal and a compound of the transition metal is added.   The method for producing a positive electrode for a lithium battery according to claim 1, wherein an electron beam or a laser beam is used for the evaporation energy.

Images