JPH10312792A - Positive electrode for lithium secondary battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery with a positive electrode containing a positive electrode active material containing a compounded oxide of lithium and manganese as a main component and having high charging and discharging rate and good cycle property and to provide a method for easily and quickly producing such a positive electrode at high production yield. SOLUTION: This positive electrode for a lithium secondary battery contains a positive electrode active material containing a compounded oxide of lithium and manganese as a main component which has a spinel structure and of which 90% or more is crystal particle having 0.3-5.0 μm particle size and 1-10 m<2> /g specific surface area. The positive electrode further contains a conductive material of conductive carbon treated for alkoxilation and the positive electrode active material and the conductive material are evenly and uniformly dispersed. The method for producing the positive electrode for a lithium secondary battery comprises a mixing process, a positive electrode paste producing process, and a positive electrode forming process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode used for a positive electrode of a lithium secondary battery.

[0002]

2. Description of the Related Art A lithium secondary battery is superior to a conventional secondary battery in that it has a high energy density, and is widely used as a power source for small electric appliances such as a mobile phone and a personal computer. Furthermore, recently, the use of the battery in a large power engine such as an electric vehicle or an electric power storage system has been considered, and a large demand for a large secondary battery is expected. Thus, the demand for lithium secondary batteries is increasing year by year.

[0003] As the positive electrode of such a lithium secondary battery, an electrode using a composite oxide of lithium and a transition metal such as cobalt, nickel, manganese and vanadium as an active material is used. Among them, an electrode using a composite oxide of lithium and manganese as an active material is considered to be promising because it has abundant manganese resources and can be reduced in cost.

However, a positive electrode active material mainly composed of a composite oxide of lithium and manganese is inferior in diffusion performance of electrons and lithium ions as compared with a positive electrode active material mainly composed of cobalt or nickel. Therefore, a positive electrode using a positive electrode active material containing a composite oxide of lithium and manganese as a main component and having a high charge / discharge rate and good cycle characteristics has not yet been obtained.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a positive electrode for a lithium secondary battery using a positive electrode active material mainly containing a composite oxide of lithium and manganese. It is another object of the present invention to provide a battery having a high charge / discharge rate and good cycle characteristics.

Further, the present invention also provides a method for easily and quickly manufacturing such a positive electrode for a lithium secondary battery with high yield.

[0007]

Means for Solving the Problems Even with a lithium manganese composite oxide having a spinel structure, electrons and lithium ions can be exchanged relatively efficiently, so that a secondary battery having a high discharge voltage can be obtained. However, even in the lithium manganese composite oxide having the spinel structure, the diffusion coefficient of electrons and lithium ions is about two orders of magnitude smaller than that of the positive electrode active material containing cobalt or nickel as a main component. Therefore, even if the electrode is formed using the positive electrode active material as it is, a high effective utilization rate of the active material cannot be obtained, and a high charge / discharge rate and good cycle characteristics cannot be obtained in the secondary battery.

Therefore, the present inventors have considered that it is necessary to mix a conductive material for imparting electron conductivity, and have attempted to mix conventionally known conductive carbon. As a result, although the charge and discharge rate and the cycle characteristics of the secondary battery were improved, they were not so large. The present inventors believe that simply mixing conductive carbon does not provide a significant improvement in charge / discharge rate and cycle characteristics, and that the conductive particles used while changing the particle size distribution and specific surface area of the positive electrode active material in various ways are also considered. An attempt was made to form an electrode by devising a conductive carbon. As a result, a positive electrode having a relatively small particle size distribution in the positive electrode active material and a small distribution width and a small specific surface area, and a positive electrode configured by combining an alkoxylated conductive carbon, A test result was obtained that the charge / discharge rate and cycle characteristics of the secondary battery were improved.

From the test results, the present inventors have found that a high effective utilization rate of the active material can be remarkably improved by forming an electrode in an optimum combination of the positive electrode active material and the conductive material. I thought and repeated trial and error. As a result, 90% or more of the total number of particles has a particle size of 0.3 to 5.0 μm and a specific surface area of crystal particles having a specific surface area of 1 to 10 m ² / g. It has been found that a high charge / discharge rate and good cycle characteristics can be obtained in a secondary battery by combining a conductive material made of conductive carbon and uniformly dispersing them to form an electrode.

[0010] The positive electrode for a lithium secondary battery of the present invention comprises:
The present invention has been made based on the above findings, and has a spinel structure mainly composed of a composite oxide of lithium and manganese, and 90% or more of the total number of particles is 0.3 to 5.0.
A positive electrode active material composed of crystal particles having a particle size of 0 μm and a specific surface area of 1 to 10 m ² / g, and a conductive material composed of alkoxylated conductive carbon; The conductive material is uniformly dispersed.

Further, to manufacture such an electrode,
It becomes possible by preparing a positive electrode paste by making the raw material powder of the active material and the conductive material into a paste, applying this to a current collector or the like to form an electrode. At this time, if the coating property and the filling property of the positive electrode paste are not good, a secondary battery having a high charge / discharge rate and good cycle characteristics cannot be manufactured.

According to Japanese Unexamined Patent Publications Nos. 5-151998, 6-243897, 6-325791 and 7-326356, the active material and the conductive material are several to several tens of microns. It is said that when a material having a relatively large particle size is used, the coatability and the filling property are excellent, but the effective utilization rate of the active material is low. Conversely, when a material having a small particle size is used, high-efficiency utilization of the active material is obtained, but application properties and filling properties are inferior.

Therefore, the present inventors have determined whether or not this is true even when a lithium manganese composite oxide having a spinel structure is used as an active material.
Electrodes were formed by changing the particle size of the active material in various ways, and their performance tests were performed. As a result, it was found that, even when this oxide was used, the effective utilization rate was significantly reduced when the particle size was increased. Conversely, it has also been found that when the particle size is reduced, the properties of the coating properties and the filling properties are reduced.

From the results of these tests, the present inventors have found that it is difficult to produce a secondary battery having both a high charge / discharge rate and good cycle characteristics simply by reducing the particle size of the positive electrode active material. Therefore, this was realized by improving the wettability of the active material and the conductive material in the paste, and the coating property and the filling property were improved while using fine powder.

In order to improve such applicability and filling property, it is necessary to prepare a uniform and low-viscosity positive electrode paste having a high solid content. This can be achieved by dispersing the active material and the conductive material together with the binder in a predetermined solvent when preparing the positive electrode paste. It is considered that an amide-based organic solvent such as n-methylpyrrolidone (NMP) is preferable as the solvent used at this time from the viewpoint of paste stability and the like. However, since the amide-based organic solvent is polar, no affinity is obtained in combination with non-polar conductive carbon, and it becomes difficult to uniformly disperse the conductive material in the solvent.

Accordingly, the present inventors have reported a case in which the dispersibility of a conductive material in water was improved by subjecting a conductive material made of carbon to an alkoxylation treatment in a higher alcohol (literature; (Surface chemistry: Koishi, Kakuda) based on the study of alkoxylating conductive carbon in alcohol. As a result, it has been found that in the production of a positive electrode capable of giving a secondary battery a high charge / discharge rate and good cycle characteristics, the alkoxylation treatment of the conductive material is extremely easy.

The method for producing a positive electrode for a lithium secondary battery according to the present invention has been invented on the basis of the above findings and has a spinel structure mainly composed of a composite oxide of lithium and manganese. 90% or more of all particles have a particle size of 0.3 to 5.0 μm and a specific surface area of 1 to 1
A mixing step of evaporating the alcohol while wet mixing 0 m ² / g of crystal particles and conductive carbon in an alcohol to obtain a mixture of the positive electrode active material and the alkoxylated conductive carbon; A positive electrode paste preparing step of kneading the mixture and the binder with an amide-based organic solvent to prepare a positive electrode paste, and applying the positive electrode paste to the surface of a current collector to form a positive electrode having a predetermined shape. And a positive electrode forming step.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a positive electrode for a lithium secondary battery and a method of manufacturing the same according to the present invention will be described below. (Positive Electrode for Lithium Secondary Battery) The positive electrode active material constituting the present invention is mainly composed of a composite oxide of lithium and manganese, but may be composed of a pure spinel type lithium manganese oxide, Alternatively, a small amount of another transition metal or the like may be added as long as the spinel structure is not changed in order to improve various functions.

In the positive electrode active material, 90% or more of the total number of the crystal particles is composed of crystal particles having a particle size of 0.3 to 5.0 μm. It may be a single primary particle or a secondary particle formed by agglomeration of primary particles smaller than the particle size. However, the latter is easier to implement than the former. The latter secondary aggregation structure of the crystal particles can be evaluated from the following measurement results.

First, the specific surface area is measured by the BET one-point method for particles whose distribution width has been confirmed to be narrow in the particle size distribution measured by the laser diffraction method, and the degree of agglomeration is determined according to the equation 1.

[0021]

[Formula 1] Agglomeration degree = converted average particle diameter calculated from particle size distribution / median particle diameter / specific surface area For example, if an ideal particle has no aggregation structure at all, the aggregation degree is 1. It is defined that the smaller the degree of agglomeration is, the less the secondary aggregated structure is. If the degree of agglomeration is usually 80 or less, it is considered that the secondary aggregated structure is less.

According to the present invention, 90% or more of the crystal particles constituting the positive electrode active material have a particle size of 0.3 to 5.0 μm and a specific surface area of 1 to 10 m ² / g. For,
The degree of aggregation is 80 or less. Therefore, it can be said that the particles are composed of crystal particles having a narrow particle size distribution width and a small secondary aggregation structure. By the way, this positive electrode active material having a narrow particle size distribution width and a small secondary aggregation structure can be obtained by using a known preparation means. That is, a solid phase reaction method using a raw material powder whose particle size distribution is regulated in advance, or a liquid phase method in which raw materials are once mixed as an aqueous solution and then nucleation and grain growth are performed by appropriate heat treatment. If necessary, these methods may be combined with pulverization and classification steps.

Next, conductive carbon is used as the conductive material. Furnace black, acetylene black, or the like can be used as the conductive carbon, and those that have been previously alkoxylated are used. The positive electrode for a lithium secondary battery of the present invention is obtained by uniformly dispersing the positive electrode active material and the conductive material as described above. In particular, in the present invention, their dispersibility is extremely excellent. This is because the present invention is composed of a cathode active material having a narrow particle size distribution and a small secondary aggregation structure, and a conductive material made of conductive carbon that has been subjected to alkoxylation treatment. We think that we could have dispersibility.

Next, a method for forming the positive electrode will be described. The formation method is not particularly limited, but for example, it can be formed as follows. First, a positive electrode active material and a conductive material are combined with a binder and kneaded using an organic solvent to prepare a paste-like kneaded material.
As the binder, polyvinylidene fluoride (PVDF) or the like can be used. In addition, an amide-based organic solvent can be used as the organic solvent. This positive electrode paste is applied to a current collector or the like to form a positive electrode. This can be accomplished through the steps of coating, drying, pressing and cutting in a conventional manner.

The shape of the positive electrode can be appropriately selected according to the shape of the lithium secondary battery such as a coin type, a cylindrical type, and a square type. Using the positive electrode thus obtained, the existing negative electrode,
By combining with a separator, an electrolytic solution, and the like, a lithium secondary battery can be manufactured. (Method for producing positive electrode for lithium secondary battery)
As described above, the mixing step, the positive electrode paste preparing step, and the positive electrode forming step are included.

First, in the mixing step, a spinel structure mainly composed of a composite oxide of lithium and manganese is used, 90% or more of all particles have a particle size of 0.3 to 5.0 μm and a specific surface area of Crystal grains of 1 to 10 m ² / g are prepared in advance. The procurement means is not particularly limited, and can be prepared by using a solid phase reaction method or a liquid phase method as described above. For example, if a liquid phase method is used, it can be performed in the following procedure.

First, a mixed solution in which a lithium salt and a manganese salt are dissolved is prepared in advance, and the mixed solution is heated to an appropriate temperature to recrystallize the lithium salt and the manganese salt to precipitate in the solution. Subsequently, the solution is dehydrated to collect only the precipitate. Finally, by firing this precipitate under appropriate heating conditions, a positive electrode active material can be obtained.

In this procedure, the lithium salt and the manganese salt are not particularly limited by the kind of the salt, and any salt can be used. However, in consideration of the following precipitation, those which are easily ionized in the solution are preferable, and for example, lithium acetate or manganese acetate can be used. The concentrations of these salts are not particularly limited, and are appropriately selected according to the type of the salt.

Further, the mixed solution preferably contains a citric acid complex. Thereby, lithium and manganese can be uniformly mixed at the atomic level. The concentration is appropriately selected according to the concentration of the lithium salt or manganese salt. Subsequently, conductive carbon such as furnace black or acetylene black is prepared, and wet-mixed with the positive electrode active material obtained above in alcohol. The alcohol used here is desirably methanol, ethanol, propanol, or the like. By using such a lower alcohol having 1 to 3 carbon atoms, depolarization of the conductive material is effectively suppressed.

By this wet mixing, the conductive carbon is alkoxylated. By evaporating and drying the alcohol,
A mixture of the positive electrode active material and the alkoxylated conductive carbon can be obtained. In the next positive electrode paste preparation step, the mixture obtained in the previous mixing step was mixed with PVD.
A binder such as F is kneaded with an amide-based organic solvent such as NMP to obtain a paste-like kneaded product. The mixing ratio of the mixture and the binder is appropriately selected, and the amount of the amide-based organic solvent is also appropriately selected so that the paste has an appropriate viscosity.

In the preparation of the positive electrode paste, since the conductive material is subjected to an alkoxylation treatment, the conductive material can be satisfactorily dispersed together with the active material in a polar amide organic solvent such as NMP. Therefore, even if the active material and the conductive material are fine powder, a positive electrode paste having excellent applicability can be obtained. In particular, when the conductive material is alkoxylated using a lower alcohol having 1 to 3 carbon atoms, the dispersibility of the conductive material is extremely excellent, so that excellent coating properties can be obtained.

Finally, in the positive electrode forming step, the positive electrode paste obtained above is applied to the surface of the current collector to form a positive electrode having a predetermined electrode shape. As this coating method, a known method can be used. The shape of the coated body is adjusted by a method such as compression molding to form a positive electrode having a predetermined size. This shape is selected according to the shape of the lithium secondary battery such as a coin type, a cylindrical type and a square type.

[0033]

The positive electrode for a lithium secondary battery according to the present invention comprises a positive electrode active material having a narrow particle size distribution width and a small secondary aggregate structure;
And a conductive material made of conductive carbon subjected to alkoxylation treatment, each of which has excellent dispersibility, so that the cathode active material is made of a lithium manganese composite oxide having a spinel structure as a main component, but has sufficiently large electrons. The conductivity is obtained, and a high effective utilization rate of the positive electrode active material is obtained. Therefore, a large amount of materials can be procured at low cost, and the secondary battery has a high charge / discharge rate and good cycle characteristics.

Next, in the method for producing a positive electrode for a lithium secondary battery according to the present invention, in the mixing step, the positive electrode active material and the conductive material are mixed at the same time as the alkoxylation of the conductive material is performed. This step is rational in that the number of steps can be reduced as compared with a method of mixing the positive electrode active material and the alkoxylated conductive material after performing the alkoxylation treatment of the conductive material. Therefore, the positive electrode for a lithium secondary battery having the above function can be easily and quickly manufactured.

The positive electrode active material and the conductive material, each of which has been dispersed very uniformly in the mixing step, are very uniformly dispersed in the binder in the next step of preparing a positive electrode paste. Therefore, the performance of imparting a high charge / discharge rate and good cycle characteristics to the secondary battery can be reliably provided to the positive electrode. Therefore, it is possible to manufacture the positive electrode for a lithium secondary battery having the above-mentioned action with a high yield.

[0036]

The present invention will be described below in more detail with reference to examples. (Example 1) 1) Mixing step A 2.6 M aqueous lithium acetate solution, a 1.3 M aqueous manganese acetate solution, and a 1.6 M aqueous citric acid solution were prepared, and the molar ratio of lithium ion, manganese ion, and citrate ion was prepared. Were mixed at a ratio of 1.03: 1.97: 1.83. This mixed solution is placed in a rotary evaporator.
Under a reduced pressure atmosphere, the mixture was heated to 200 ° C. and dehydrated to obtain a remaining precursor.

This precursor was placed in an alumina crucible and calcined in an air atmosphere at 400 ° C. for 4 hours. The heating rate was 100 ° C./hour, and the cooling rate was 100 ° C./hour. After crushing, press molding is performed at 800 ° C. for 1 hour in an oxygen atmosphere.
The mixture was fired for 2 hours and then crushed again to obtain a positive electrode active material. When the particle size distribution of the positive electrode active material was measured by a laser diffraction method, it was confirmed that the powder had a narrow particle size distribution with a minimum particle size of 0.3 μm, a maximum particle size of 5 μm, and a median diameter of 1 μm. The specific surface area measured by the BET one-point method was 4 m ² / g. Further, from observation by a scanning electron microscope (SEM), it was confirmed that the aggregation of the primary particles was small and the particles did not exhibit secondary particles. 2) Positive electrode paste preparation step The active material prepared as described above and furnace black as a conductive material were immersed in alcohol and mixed.
The compounding amount is 11.2 g of the conductive material with respect to 148.9 g of the active material.
2650 g of Sialon balls having a diameter of m and 1760 g of Sialon balls having a diameter of 5 mm. The pot was sealed, rotated at 100 rpm and mixed for 4 hours, and then the balls were selected and the residue obtained by evaporating the ethanol was lightly pulverized with a mixer to remove the mixture of the active material and carbon into one.
57.3 g were obtained.

It was confirmed by SEM that the active material itself was hardly pulverized during the immersion and mixing processes. On the other hand, from the measurement of the infrared absorption of the mixture, a change was confirmed in a wave number band considered to be due to the hydroxyl group. From these results, it is presumed that the alkoxylation treatment of the conductive material with alcohol was performed in this step. Next, 14.2 g of PVDF was added to the mixture in terms of the amount of PVDF, and the mixture was kneaded in vacuum while adding NMP to an appropriate viscosity to prepare a positive electrode paste.

The viscosity of the final paste was 18000 mPa · s (0.5 rpm) as measured by an E-type viscometer, and the solid content was 57%. 3) Positive electrode forming step The paste prepared in 2) was applied to both sides of an aluminum foil having a thickness of 20 microns, dried, and pressed by a roll press to obtain a positive electrode. FIG. 1 shows the result of SEM observation of the electrode surface. It can be seen that fine primary particles of about 1 micron are uniformly distributed without agglomeration, and the conductive material is also uniformly distributed. The amount of the active material in the electrode was 2.4 g / cm ² , which was 56% in terms of the filling rate (ratio to the true density of the active material 4.28 g / cm ² ). In addition, no falling off of the active material was observed. (Example 2) A positive electrode was produced in the same manner as in Example 1 except that in the preparation of the positive electrode paste, the conductive material was alkoxylated using methanol instead of ethanol.

In this example, it was confirmed by SEM that the active material itself was hardly pulverized in the process of dipping and mixing, as in Example 1. In addition, from the measurement of the infrared absorption of the mixture, a change in a wavenumber band considered to be caused by a hydroxyl group was also confirmed. From these results, it is presumed that the alkoxylation treatment of the conductive material was effectively performed. (Example 3) A positive electrode was prepared in the same manner as in Example 1, except that the conductive material was alkoxylated using propanol instead of ethanol in the preparation of the positive electrode paste.

In this example, it was confirmed by SEM that the active material itself was hardly pulverized in the process of immersion and mixing as in Example 1. In addition, from the measurement of the infrared absorption of the mixture, a change in a wavenumber band considered to be caused by a hydroxyl group was also confirmed. From these results, it is presumed that the alkoxylation treatment of the conductive material was effectively performed. (Example 4) A positive electrode was prepared in the same manner as in Example 1 except that in the preparation of the positive electrode paste, the conductive material was alkoxylated using butanol instead of ethanol.

In this example, it was confirmed by SEM that the active material itself was hardly pulverized in the process of immersion and mixing as in Example 1. In addition, from the measurement of the infrared absorption of the mixture, the change in the wave number band, which is considered to be caused by the hydroxyl group, was also confirmed, although slightly smaller than that in Example 1. From this result, it is presumed that the conductive material has been alkoxylated. Comparative Example 1 A positive electrode active material was prepared by controlling the particle size by changing the synthesis conditions, a positive electrode paste was prepared in the same manner as in Example 1, and a positive electrode was formed. Table 1 shows the properties of each of the positive electrode active materials (A to D) prepared in this comparative example, and the applicability and filling properties of the positive electrode paste. Table 1 also shows those prepared in Example 1 above.

[0043]

[Table 1] From Table 1, B, C and D of this comparative example and Example 1
It can be seen that the positive electrode paste of (1) is superior in applicability to that of (A). (Preparation of Secondary Battery) Each positive electrode prepared in Examples 1 to 3 and positive electrode (C and D) prepared in Comparative Example 1
Were used to produce lithium secondary batteries, respectively. Here, a negative electrode formed of lithium metal was used. In addition, a solution in which 1 M LiPF ₆ was contained as an electrolyte in a mixed solvent prepared by mixing ethylene carbonate and diethylene carbonate at a volume ratio of 1: 1 was used as the electrolytic solution.

A battery using these positive electrodes was subjected to a charge / discharge test as follows. First, the battery was charged at a constant current of 1 mA / cm ² , then charged at a constant voltage of 4.3 V for a total of 4 hours, and then charged at a constant current of 0.25 to 4 mA / cm ² . Table 2 shows the battery characteristics of these secondary batteries.

[0045]

[Table 2] From Table 2, it can be seen that Example 1 has an excellent filling rate, though slightly lower in filling rate than C and D of Comparative Example 1, and also has excellent high-rate characteristics. The difference in the high rate characteristics between Example 1 and Comparative Example 1 is due to the difference in the degree of aggregation described above. As also shown in Table 1 above, the degree of aggregation in the positive electrode active material of Example 1 was extremely small. This suggests that the conductive material is uniformly dispersed, which means that the electron conductivity is excellent. As a result, it is considered that the high-rate characteristic was significantly improved in the first embodiment.

The charging current at the time of constant voltage charging quickly became zero. This indicates that the active materials in the electrodes are reacting uniformly. In addition, even when the battery was discharged at a high rate of 4 mA / cm ² , the discharge capacity was 80% that of a battery discharged at a rate of 0.25 mA / cm ² , indicating that the battery was excellent in high-rate characteristics. Further, as shown in FIG. 2, in Example 1, the cycle characteristics were also good. Although the test results in Example 2 and Example 3 are not shown here, the same results as in Example 1 were obtained. Comparative Example 2 A positive electrode active material was prepared in the same manner as in Example 1, but as shown in Table 1, the conditions of the immersion treatment were changed to prepare a positive electrode paste, and a positive electrode was formed. Table 3 shows the properties of the pastes (a and b) obtained in this comparative example. Table 3 also shows the positive electrode pastes obtained in Examples 1 to 4.

[0047]

[Table 3] In a and b, the conductive material did not disperse and a high-viscosity and non-uniform paste was obtained. In Examples 1 to 3, low-viscosity and uniform pastes were obtained. In Example 4, the paste was slightly inferior to Examples 1 to 3, but had low viscosity and was almost uniform. From these results, it is understood that the alkoxylation treatment of the conductive material with alcohol is effective for the present invention. In particular, it can be seen that treatment with a lower alcohol having 1 to 3 carbon atoms is extremely effective.

[0048]

According to the positive electrode for a lithium secondary battery of the present invention, a lithium secondary battery having a high energy density and maintaining a high energy density even after repeated charging and discharging can be obtained. In addition, an electrode having such performance can be produced at low material cost, and a large-sized electrode can be mass-produced. Therefore, the present invention can be used not only for batteries used for small electric appliances such as conventional mobile phones and personal computers, but also for large batteries used for electric vehicles and electric storage systems.

Further, according to the method for producing a positive electrode for a lithium secondary battery of the present invention, the positive electrode for a lithium secondary battery having the above-mentioned effects can be mass-produced in a short time at low cost.

[Brief description of the drawings]

FIG. 1 is an SEM observation image showing the appearance of the electrode surface of a positive electrode obtained in Example 1.

FIG. 2 is a graph showing the results of a charge / discharge test for the positive electrode obtained in Example 1.

[Procedure amendment]

[Submission date] August 28, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuaki Kawai 41-cho, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. (71) Inventor Yoshio Ukyo Yoshito Ukyo 41, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture

Claims (2)

[Claims] 1. A spinel structure mainly composed of a composite oxide of lithium and manganese, wherein 90% or more of all particles have a particle size of 0.3 to 5.0 μm and a specific surface area of 1 to 5.0 μm.
A positive electrode active material comprising 10 m ² / g crystal particles; and a conductive material comprising alkoxylated conductive carbon, wherein the positive electrode active material and the conductive material are each uniformly dispersed. A positive electrode for a lithium secondary battery, comprising: 2. It has a spinel structure mainly composed of a composite oxide of lithium and manganese, 90% or more of all particles have a particle size of 0.3 to 5.0 μm and a specific surface area of 1 to 5.0 μm.
10 m ² / g of crystal particles and conductive carbon
The alcohol is evaporated while wet mixing in a
A mixing step of obtaining a mixture of the positive electrode active material and the alkoxylated conductive carbon, a positive electrode paste preparation step of kneading the mixture and a binder using an amide-based organic solvent to prepare a positive electrode paste, A method for forming a positive electrode having a predetermined shape by applying the positive electrode paste to the surface of a current collector, and a method for manufacturing a positive electrode for a lithium secondary battery.