JPH10106544A - Manufacture of electrode of lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture electrodes for a lithium battery at a low cost whereby a positive electrode active material having a high energy density can be easily fabricated by a simple procedure. SOLUTION: A positive electrode active material of a lithium battery is formed from oxides of transition metals belonging to Group 7A or 8A (Co, Ni, Mn, Fe, etc.), and at least part of the transition metal oxide(s) has amorphous structure. The transition metal oxide is subjected to a melting and solidifying process by the mechanical ironing method, electron beam irradiation method, laser beam irradiation method, or plasma flame irradiation method so that part thereof is turned amorphous, and the obtained transition metal oxide is molded into the specified shape. Thus the intended electrode for lithium battery is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode of a lithium battery, and more particularly to a lithium battery having a high energy density obtained by forming a positive electrode active material from a partially or entirely amorphous transition metal oxide. And a method of manufacturing the electrode.

[0002]

2. Description of the Related Art FIG. 1 is a sectional view showing a spiral lithium battery. In this lithium battery, a sheet-like positive electrode (positive electrode active material) 3 and a negative electrode 4 are opposed to each other with a separator 5 interposed therebetween, and these are spirally wound and placed in a battery case 7. A jacket 6 is provided outside the battery case 7. A negative terminal 2 is provided at the bottom of the battery case 7, and a vent diagram 8, a vent spike 9 and the positive electrode cap 1 are provided at the top.

As a positive electrode active material for a lithium battery having such a structure, the present applicant has already disclosed LiCoO ₂ and L
is constituted by a Group 7A or 8A Group oxide of a transition metal such as iNiO _2, at least some have proposed one having an amorphous structure (JP-A of the oxide 8-7800
No. 2). As a method for amorphizing the oxide of a transition metal of Group 7A or Group 8A, the following method was proposed in the above-mentioned prior application. That is, for example, an oxide of a transition metal of Group 7A or 8A and an oxide of a transition metal of Group 5A or 6A (for example, V ₂ O ₅ and Cr ₃ O ₈ ) are mixed and melted by heating. Then, there is a method of quenching (melting quenching method). In addition, a composite oxide of Li and a transition metal or a mixture of a Li oxide and a transition metal oxide is heated and melted, and then rapidly cooled to be amorphous. Further, a transition metal or a transition metal oxide can be used as a raw material to form an amorphous state by forming a thin film by sputtering, vapor deposition, ion plating or the like in an oxygen atmosphere (thin film forming method). Furthermore, it is also possible to use a Li organic material and a transition metal organic material as raw materials, to form a sol or a gel, and then to make the material amorphous by a sol-gel method of firing (sol-gel method).

[0004]

However, this conventional method for manufacturing an electrode of a lithium battery has the following disadvantages.

[0005] First, the melt quenching method, specifically, 50 m
% of V ₂ O ₃ powder and 50 mol% of CoO powder were mixed in an agate mortar, and the mixed powder was vacuum-sealed in a quartz tube. The quartz tube was heated to 900 ° C. in a heating furnace. Then, the powder is melted to obtain a base composite oxide. Next, the composite oxide was charged into a quartz nozzle of a liquid quenching device, heated and melted by a high-frequency melting device, and then the melt was jetted onto a water-cooled copper roll using Ar gas as a carrier gas, and the melt was discharged. Is rapidly quenched and solidified with a water-cooled copper roll to obtain an amorphous quenched ribbon. Since the melt quenching method obtains the transition metal oxide which has been made amorphous in this way and shapes it into a predetermined electrode shape to be used as a positive electrode active material, there is a problem that the step of making amorphous is complicated.

[0006] The thin film forming method is a method of forming a thin film by sputtering, vapor deposition, ion plating or the like in an oxygen atmosphere using a transition metal or a transition metal oxide as a raw material.
Since the manufacturing apparatus is special and expensive, there is a problem that the manufacturing cost is high.

Furthermore, the sol-gel method has the disadvantage that not only is the raw material expensive, but the production process is complicated, for example, it is necessary to control the water in each step such as the hydrolysis step.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a method of manufacturing a lithium battery electrode which can manufacture a positive electrode active material having a high energy density in a simple process and reduce the manufacturing cost. With the goal.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing an electrode for a lithium battery, comprising using a composite oxide of a transition metal belonging to Group 7A or 8A in the periodic table and Li as a raw material, The method is characterized by comprising a step of obtaining a transition metal oxide at least partially amorphous by an alloying method, and a step of forming an electrode having a predetermined shape from the transition metal oxide.

According to a second aspect of the present invention, there is provided a method of manufacturing an electrode for a lithium battery, comprising the steps of: using a mixture of an oxide of a transition metal belonging to Group 7A or 8A of the periodic table and a Li oxide as a raw material; And a step of forming an electrode having a predetermined shape from the transition metal oxide.

The method for producing an electrode of a lithium battery according to the invention of claim 3 or 4 of the present invention is a method for producing a mixture of a transition metal of Group 7A or 8A of the periodic table and a Li oxide or metal Li as a raw material. Or a step of obtaining a transition metal oxide at least partially amorphized by a mechanical alloying method in an oxidizing atmosphere, and a step of forming an electrode of a predetermined shape from the transition metal oxide. I do. The stirring time is required to be 10 hours or more, and is preferably 100 to 480 hours.

According to a fifth aspect of the present invention, there is provided a method of manufacturing an electrode for a lithium battery, wherein a raw material is a crystalline composite oxide of Li and a transition metal of Group 7A or 8A in the periodic table and Li is used as an electron beam. Irradiating a laser beam or a plasma flame to obtain a transition metal oxide which is melt-solidified and at least partially amorphized; and forming an electrode of a predetermined shape from the transition metal oxide. It is characterized by.

According to a sixth aspect of the present invention, there is provided a method of manufacturing an electrode for a lithium battery, comprising the steps of using a crystalline transition metal oxide containing a transition metal of Group 7A or 8A of the periodic table as a raw material, and using an electron beam, It is characterized by comprising a step of obtaining a transition metal oxide that is at least partially amorphized by irradiating a laser beam or a plasma flame and solidifying it, and a step of forming an electrode of a predetermined shape from the transition metal oxide. And

In the invention according to claims 1 to 4 of the present application, a composite oxide of a transition metal and Li, a mixture of a transition metal oxide and a Li oxide, a mixture of a transition metal and a Li oxide, or A mixture with metal Li is used as a raw material, and this raw material is stirred with high energy by a mechanical alloying method. When a mixture of a transition metal and a Li oxide or a mixture of a transition metal and a metal Li is used as a raw material, a mechanical alloying treatment is performed in the air or an oxidizing atmosphere.
As a result, a transition metal oxide that is at least partially amorphous is obtained. According to the present invention, an amorphous transition metal oxide can be obtained by an extremely simple process of the mechanical alloying process.

Further, as in the invention according to claim 5 of the present application,
By using a crystalline composite oxide of a transition metal and Li as a raw material and irradiating it with an electron beam, a laser beam or a plasma flame, the transition metal oxide that has become amorphous can be produced with high working efficiency in a short time. Obtainable.

Furthermore, as in the invention according to claim 6 of the present application,
By irradiating the crystalline transition metal oxide with an electron beam, a laser beam, or a plasma flame, an amorphous transition metal oxide can be easily obtained in a short time.

According to the present invention, a lithium battery having an extremely high energy density can be manufactured at low cost by using the thus obtained amorphous transition metal oxide.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be specifically described. As a positive electrode active material used for an electrode of a lithium battery, a 7A or 8A group transition metal oxide having high oxidizing power is used. Conventionally, a positive electrode active material composed of a 7A or 8A transition metal has been crystallized and has a layered structure. In the present invention, the use of an amorphous transition metal oxide of a Group 7A or Group 8A realizes higher energy of a lithium battery.

The reason why the energy density is improved by amorphization when LiCoO ₂ is used as the positive electrode active material will be described.

When LiCoO ₂ is used as a positive electrode active material, a reaction represented by the following chemical formula 1 occurs.

[0021]

[Image Omitted] CoO ₂ + Li ⁺ + e ⁻ ← → LiCoO ₂ This reaction, when focusing only on Co, has the following chemical formula 2.
Can be expressed as

[0022]

[ ^Formula 2] Co ⁴⁺ ← → Co ³⁺

[0023] In theory, CoO ₂ ^- L with respect to one molecule of
One ion of i ⁺ binds. However, if the positive electrode active material is crystalline LiCoO ₂ , Li ⁺
Ions can only move two-dimensionally. Crystalline LiCo
In O ₂ , diffusion of Li ⁺ ions is rate-limited by the interlayer distance and directionality of the layered structure. Also, when taking out a certain amount (about 50%) or more of Li ⁺ ions, the layered structure is impossible is output in of destroyed Li ⁺ ions. For this reason, it was conventionally difficult to improve the energy density of the lithium battery.

Therefore, in the present invention, by making the positive electrode active material amorphous, LiCo
A network structure is formed while maintaining the bonding of O ₂ molecules. As a result, the following effects can be obtained. Since the distance between CoO ₂ molecules is increased and the crystal lattice is disturbed to form a sparse structure, the number of sites into which Li ⁺ ions enter is greatly increased. The isotropy of the Li ⁺ ion movement path can be ensured. Since the structure is homogeneous and there are no grain boundaries, there is nothing that hinders the movement of Li ⁺ ions.

With these effects, the energy density of the lithium battery is improved. Further, the present invention has the following effects. When the positive electrode active material has an amorphous structure, the moldability is improved and the thinning is facilitated. The range of choice of chemical composition is widened, and it is possible to further increase the energy density by adding Li in excess.

The above-mentioned effects can be obtained also in the case of an oxide of a transition metal of Group 7A or Group 8A other than Co, by adopting an amorphous structure.

In the present embodiment, the composite oxide of the transition metal and Li or the mixture of the transition metal oxide and the Li oxide is mixed and stirred with high energy by a mechanical alloying method. To obtain a transition metal oxide. Further, a transition metal oxide which is made amorphous by subjecting a mixture of a transition metal and a Li oxide to mechanical alloying treatment in the air or an oxidizing atmosphere is obtained. Alternatively, an amorphous transition metal oxide can be obtained by baking a crystalline composite oxide of a transition metal and Li and irradiating it with an electron beam, a laser beam, or a plasma flame. Further, even when the crystalline transition metal oxide is fired and irradiated with an electron beam, an amorphous transition metal oxide can be obtained. In each of these methods, the steps are simple, and irradiation with an electron beam, a laser beam, or a plasma flame is sufficient in a short time, so that the processing can be performed quickly.

The amorphous 7A thus obtained
By molding an oxide of a Group 5A or Group 8A transition metal into a predetermined electrode shape and using it as a positive electrode active material, a lithium battery with significantly improved energy density can be manufactured.

[0029]

Next, the results of the manufacture of the lithium battery electrode according to the present invention and the examination of its characteristics will be described.

Example 1 LiCoO ₂ was charged into an SiO ₂ container for a ball mill, and Si
An O ₂ ball was placed and capped. LiCoO ₂ was stirred with high energy in a SiO ₂ container and mechanically alloyed to prepare a powder sample. The stirring time is 1
50 hours. When the prepared sample was examined by an X-ray diffraction method, it was confirmed that the sample was amorphous.

Next, CB (carbon black) and a fluororesin powder were mixed with the powder, and molded into a predetermined shape to obtain a positive electrode. A spiral lithium battery shown in FIG. 1 was assembled using carbon as the negative electrode and PC (polypyrene carbonate) + LiClO ₄ (1 mol / liter) as the electrolyte.

In place of LiCoO ₂ , LiN
iO using _2, LiMnO _2, LiFeO ₂ and LiMn ₂ O _4, was assembled in the same manner as a spiral type lithium battery. The size of this battery is 18mm in diameter and 65m in length
m and the weight is 40 g.

The results of examining the charge / discharge characteristics of these batteries are summarized in Table 1 below.

[0034]

[Table 1]

As is clear from Table 1, the battery of this embodiment has an energy density of 300 to 318 Wh / liter, and has a high energy density similarly to the lithium battery disclosed in JP-A-8-78002. Met.

Example 2 Li ₂ O and CoO were each weighed so that the molar ratio of Li / Co = 1, and charged into a SiO ₂ container for a ball mill.
High energy was given by a ball made of SiO ₂ and mixed and stirred. When the mechanically alloyed mixture was examined by an X-ray diffraction method, it was confirmed that the mixture had become amorphous. A spiral type lithium battery was assembled in the same manner as in Example 1.

A spiral type lithium battery was similarly assembled using Ni oxide, Mn oxide and Fe oxide instead of the Co oxide. The results of examining the charge / discharge characteristics of these batteries are summarized in Table 2 below.

[0038]

[Table 2]

As is clear from Table 2, the battery of this embodiment has an energy density of 310 to 325 Wh / liter, and has a high energy density like the lithium battery disclosed in JP-A-8-78002. Met.

Example 3 Li ₂ O and metal Co were weighed so that the molar ratio of Li / Co = 1, and charged into a ball mill SiO ₂ container. The mixture was stirred with high energy in the air using a ball made of SiO ₂ . When the mechanically alloyed mixture was examined by an X-ray diffraction method, it was confirmed that the mixture had become amorphous. The mechanically alloyed mixture was assembled into a spiral lithium battery in the same manner as in Example 1.

Further, the inside of the container was changed from the atmosphere to an oxygen atmosphere, and high energy stirring was performed. Using this mixture, a spiral lithium battery was assembled.

Further, instead of the metal Co, Ni, Mn
Similarly, a spiral type lithium battery was assembled using Fe and Fe as the positive electrode material. The results of examining the charge / discharge characteristics of these batteries are summarized in Table 3 below.

[0043]

[Table 3]

As is apparent from Table 3, the battery of this embodiment has an energy density of 303 to 335 Wh / liter, and has a high energy density like the lithium battery disclosed in Japanese Patent Application Laid-Open No. 8-78002. Met.

Example 4 Metal Li and metal Co were weighed so that the molar ratio of Li / Co = 1, and then charged into an SiO ₂ container for a ball mill. The mixture was stirred with high energy in the air using a ball made of SiO ₂ . When the mechanically alloyed mixture was examined by an X-ray diffraction method, it was confirmed that the mixture had become amorphous. The mechanically alloyed mixture was assembled into a spiral lithium battery in the same manner as in Example 1.

Further, the inside of the vessel was changed from the atmosphere to an oxygen atmosphere, and high-energy stirring was performed. Using this mixture, a spiral lithium battery was assembled.

Further, in place of the metal Co, Ni, Mn
Similarly, a spiral type lithium battery was assembled using Fe and Fe as the positive electrode material. The results of examining the charge / discharge characteristics of these batteries are summarized in Table 4 below.

[0048]

[Table 4]

As is apparent from Table 4, the battery of this embodiment has an energy density of 310 to 336 Wh / liter, and has a high energy density like the lithium battery disclosed in JP-A-8-78002. Met.

Example 5 A thin fired solidified product of LiCoO ₂ having a thickness of 0.1 mm to ₂ mm was placed on a copper plate. The fired and solidified product was irradiated with an electron beam, a laser beam or a plasma flame for a short time to be melt-solidified. When this coagulated product was examined by an X-ray diffraction method, it was confirmed that the sample was broad except that some peaks remained in the analysis value, and it was confirmed that a part of the sample was amorphous.

Next, the solidified product was pulverized, and a spiral lithium battery was assembled in the same manner as in Example 1.

In place of the above LiCoO ₂ , LiN
_{iO 2, LiMnO 2, LiFeO 2} , Co oxides, Ni
A spiral lithium battery was assembled in the same manner using an oxide, a Mn oxide, and an Fe oxide. The results of examining the charge / discharge characteristics of these batteries are summarized in Table 5 below. It should be noted that those having the same central element such as LiCoO ₂ and Co oxide have the same characteristics, and thus are shown as including Co.

[0053]

[Table 5]

As is clear from Table 5, the energy density of the battery of this embodiment is 310 to 32 in the case of the electron beam.
0 Wh / liter, 305-320 Wh for laser beam
/ Liter and 300 to 312 Wh / liter in the case of a plasma flame, and had a high energy density as in the lithium battery disclosed in Japanese Patent Application Laid-Open No. 8-78002.

Example 6 A solid obtained by sintering LiCoO ₂ into a plate was placed on a platen provided with slits. A water tank for cooling was mounted directly below the surface plate. Next, this plate-shaped sintered body was cut by a laser beam or a plasma flame. At this time, oxygen was used as the assist gas, and conditions were set so that dross generated during cutting was dropped into the water tank and cooled. Thereafter, the dross collected in the water tank was collected, dried in a vacuum, and further pulverized, and a spiral lithium battery was assembled in the same manner as in Example 1.

In place of the above LiCoO ₂ , LiN
_{iO 2, LiMnO 2, LiFeO 2} , Co oxides, Ni
A spiral lithium battery was assembled in the same manner using an oxide, a Mn oxide, and an Fe oxide. The results of examining the charge / discharge characteristics of these batteries are summarized in Table 7 below. It should be noted that those having the same central element such as LiCoO ₂ and Co oxide have the same characteristics, and thus are shown as including Co.

[0057]

[Table 6]

As is clear from Table 6, the energy density of the battery of this embodiment was 310 when the laser beam was cut.
~ 330Wh / liter, plasma flame cutting 303 ~ 3
The energy density was 25 Wh / liter, and the energy density was high as in the lithium battery disclosed in JP-A-8-78002.

According to the method of this embodiment, the transition metal and Li
, A mixture of a transition metal oxide and a Li oxide, a mixture of a transition metal and a Li oxide in an oxidizing atmosphere, or a mixture of a transition metal and a metal Li in an oxidizing atmosphere. By using the mixture as a raw material and mechanically agitating with high energy stirring, it was possible to form amorphous by an extremely simple process. In addition, a crystalline composite oxide or a crystalline transition metal oxide of transition metal and Li was calcined, and this was irradiated with an electron beam, a laser beam, or a plasma flame for a short time, thereby being able to be made amorphous. . For this reason, the process is significantly simplified.

[0060]

As described above, the method of manufacturing an electrode of a lithium battery according to the present invention is made amorphous by a mechanical alloying method, an electron beam irradiation method, a laser beam irradiation method, or a plasma flame irradiation method. A positive electrode active material composed of a transition metal oxide that has been highly efficiently amorphousized can be obtained in a short time in a simple process, and the manufacturing cost of a lithium battery having a high energy density can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a lithium battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode cap, 2 ... Negative electrode terminal, 3 ... Positive electrode, 4 ... Negative electrode, 5 ... Separator, 6 ... Jacket, 7 ... Battery case, 8 ... Vent Diagram, 9 ... vent spike

Claims (6)

[Claims] 1. A transition metal oxide obtained by using a composite oxide of at least one transition metal selected from Group 7A and 8A of the periodic table and Li as a raw material and at least partially amorphizing by a mechanical alloying method. Obtaining a thing;
Forming an electrode of a predetermined shape from the transition metal oxide. 2. A mixture of an oxide of at least one transition metal selected from Groups 7A and 8A of the Periodic Table and a Li oxide as a raw material, at least a portion of which is made amorphous by a mechanical alloying method. A method for manufacturing an electrode for a lithium battery, comprising: a step of obtaining a transition metal oxide; and a step of forming an electrode having a predetermined shape from the transition metal oxide. 3. A mixture of at least one transition metal selected from Group 7A and Group 8A of the periodic table and a Li oxide as a raw material, which is obtained by a mechanical alloying method in the air or an oxidizing atmosphere. A method for producing an electrode for a lithium battery, comprising: a step of obtaining a transition metal oxide partially amorphousized; and a step of forming an electrode having a predetermined shape from the transition metal oxide. 4. A mixture of at least one transition metal selected from Groups 7A and 8A of the periodic table and metal Li as a raw material, and at least one metal alloy is formed by mechanical alloying in air or an oxidizing atmosphere. A method for producing an electrode for a lithium battery, comprising: a step of obtaining a transition metal oxide in which a portion is made amorphous; and a step of forming an electrode having a predetermined shape from the transition metal oxide. 5. A crystalline composite oxide of Li and at least one transition metal selected from Group 7A and Group 8A of the periodic table as a raw material, and the raw material is irradiated with an electron beam, a laser beam, or a plasma flame. Electrode of a lithium battery, comprising: a step of obtaining a transition metal oxide at least partially amorphous by being melted and solidified by performing the method; and a step of forming an electrode having a predetermined shape from the transition metal oxide. Manufacturing method. 6. A crystalline transition metal oxide containing at least one transition metal selected from Groups 7A and 8A of the periodic table is used as a raw material, and the raw material is irradiated with an electron beam, a laser beam, or a plasma flame. A step of obtaining a transition metal oxide at least partially amorphized by melt-solidification, and a step of forming an electrode of a predetermined shape from the transition metal oxide. Production method.