JP2014118329A - Method for manufacturing an olivine-type silicate compound including a transition metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in a high purity and a high yield based on an inexpensive and simple means, an olivine-type silicate compound having finer and homogeneous particle diameters and a homogeneous composition.SOLUTION: In the provided method for manufacturing an olivine-type silicate compound other than lithium iron silicate including a transition metal (M), an admixture slurry including (A) a transition metal (M) compound (M expresses Fe, Ni, Co, Al, Zn, V, Zr, or Mn), (B) a silicate compound, (C) a lithium compound, and (D) water is hydrothermally reacted within a steam-type autoclave using, as a heat source, a saturated steam manufactured by heating water having a dissolved oxygen concentration of 1.0 mg/L or below.

Description

  The present invention relates to a method for producing an olivine-type silicate compound other than lithium iron silicate containing a transition metal, which is useful as a positive electrode material for a lithium ion secondary battery.

Secondary batteries used for portable electronic devices, hybrid cars, electric cars, and the like have been developed, and lithium ion secondary batteries are particularly widely known. The lithium ion battery basically includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator. LiCoO ₂ is widely used as a positive electrode material, and LiNiO ₂ , LiMn ₂ O _{4 and the} like have been developed. However, these lithium-based metal oxides have a problem that a certain capacity is low at a high voltage.

  On the other hand, recently, it has been proposed to use an olivine-type silicate compound such as lithium iron phosphate or lithium iron silicate having an olivine structure for the positive electrode. However, this method of synthesizing lithium iron phosphate and lithium iron silicate is a solid phase method, and it is necessary to perform firing and pulverization in an inert gas atmosphere, and the operation is complicated.

  Therefore, attempts have been made to produce lithium iron phosphate and lithium iron silicate by a hydrothermal reaction (Patent Documents 1 and 2, Non-Patent Document 1). In these methods, a lithium compound, an iron compound, and a phosphoric acid compound are hydrothermally reacted in a pressure resistant vessel.

JP 2002-151082 A JP 2004-95385 A

Electrochemistry Communications 3 (2001) 505-508

According to these conventional methods for producing an olivine-type silicate compound by hydrothermal reaction, although a uniform particle size can be obtained as compared with the solid phase method, iron is oxidized during the hydrothermal reaction, and the resulting positive electrode There is a problem that the battery performance of the material is lowered. In order to solve such a problem, in Patent Document 1, an inert gas such as nitrogen or argon is sealed in a pressure vessel to carry out the reaction. However, it takes time to enclose the inert gas, and a large amount of inert gas is required, so that there is a problem that the price of the obtained positive electrode material increases.
Accordingly, there has been a demand for a method for producing an olivine-type silicate compound having a finer and uniform particle size with high purity and high yield by an inexpensive and simple means.

  Therefore, as a result of various studies on the hydrothermal reaction conditions of the transition metal compound, the present inventor has found that the heat source is water in a steam type autoclave that is saturated steam produced by heating water having a dissolved oxygen concentration of 1.0 mg / L or less. If the thermal reaction is carried out, it is not necessary to fill the autoclave with an inert gas, iron oxidation can be prevented, and an olivine-type silicate compound containing a transition metal with a small and uniform particle size can be obtained at a lower cost and with ease. Furthermore, it was found that a lithium-ion secondary battery having a high capacity and excellent charge / discharge characteristics can be obtained by using the obtained product as a positive electrode material, and the present invention was completed.

That is, the present invention provides (A) a transition metal (M) compound (M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn), (B) a silicate compound, and (C) a lithium compound. And (D) the mixture slurry containing water is hydrothermally reacted in a steam autoclave which is a saturated steam produced by heating water having a dissolved oxygen concentration of 1.0 mg / L or less. The present invention provides a method for producing an olivine-type silicate compound other than lithium iron silicate containing a transition metal (M).
Moreover, this invention provides the lithium ion secondary battery which contains olivine type silicate compounds other than lithium iron silicate containing the transition metal (M) obtained by said manufacturing method as positive electrode material.

According to the production method of the present invention, an olivine-type silicate compound having a small particle size and containing a uniform transition metal (M) can be obtained by a simple hydrothermal synthesis reaction without using a large amount of inert gas. Moreover, the lithium ion secondary battery containing the obtained olivine type silicate compound as a positive electrode material has a high capacity and excellent charge / discharge characteristics.
The olivine-type silicate compound containing the transition metal (M) obtained by the production method of the present invention does not contain lithium iron silicate.

The schematic of the vapor | steam autoclave used for this invention method is shown. The SEM image of the olivine type | mold silicate compound powder obtained in Example 1 and Comparative Example 1 is shown. The XRD chart of the olivine type | mold silicate compound powder obtained in Example 1 and Comparative Example 1 is shown. The SEM image of the olivine type silicate compound powder obtained in Example 2 and Comparative Example 2 is shown. The XRD chart of the olivine type | mold silicate compound powder obtained in Example 2 and Comparative Example 2 is shown. The SEM image of the olivine type | mold silicate compound powder obtained in Example 3 and Comparative Example 3 is shown. The XRD chart of the olivine type | mold silicate compound powder obtained in Example 3 and Comparative Example 3 is shown. The charge / discharge capacity curve of the battery obtained in Example 4 and Comparative Example 4 is shown. The charging / discharging capacity curve of the battery obtained in Example 5 and Comparative Example 5 is shown. The charging / discharging capacity curve of the battery obtained in Example 6 and Comparative Example 6 is shown.

  The manufacturing method of the olivine type silicate compound containing the transition metal (M) of the present invention is as follows: (A) Transition metal (M) compound (M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn) , (B) Silica compound, (C) Lithium compound, and (D) Autoclave which is a saturated steam produced by heating water having a dissolved oxygen concentration of 1.0 mg / L or less to a mixture slurry containing water This is a method of hydrothermal reaction.

  (A) As a transition metal (M) compound, an iron compound, a nickel compound, a cobalt compound, an aluminum compound, a zinc compound, a vanadium compound, a zirconium compound, or a manganese compound may be used.

  The iron compound, nickel compound, cobalt compound, manganese compound, and zinc compound may be any divalent iron compound, divalent nickel compound, divalent cobalt compound, divalent manganese compound, or divalent zinc compound. , For example, halides such as iron halide, nickel halide, cobalt halide, manganese halide, zinc halide, iron sulfate, nickel sulfate, cobalt sulfate, manganese sulfate, zinc sulfate and other sulfates, iron oxalate, Examples thereof include organic acid salts such as iron acetate, nickel acetate, cobalt acetate, manganese acetate, and zinc acetate.

  The aluminum compound may be a trivalent compound, and examples thereof include halides such as aluminum halide, metal sulfates such as aluminum sulfate, and metal organic acid salts such as aluminum acetate and aluminum lactate.

  The zirconium compound may be a tetravalent compound, and examples thereof include organic acid salts such as zirconium halide, zirconium sulfate, zirconium diacetate oxide, zirconium octoate, and zirconium laurate oxide.

(B) The silicic acid compound is not particularly limited as long as it is a reactive silica compound, and amorphous silica, Na ₄ SiO ₄ (for example, Na ₄ SiO ₄ .H ₂ O) or the like is used.

  (C) Examples of the lithium compound include lithium metal salts such as lithium fluoride, lithium chloride, lithium bromide and lithium iodide, lithium hydroxide, lithium carbonate, etc., but it is inexpensive to use lithium carbonate. This is preferable.

  In using (A) transition metal (M) compound, (B) silicic acid compound, and (C) lithium compound, the molar ratio of (A) transition metal (M) compound and (C) lithium compound used is 1: 2 to 1: 3 are preferable in terms of the transition metal (M) compound and lithium ion, and more preferably 1: 2 to 1: 2.5. The molar ratio of (C) lithium compound and (B) silicate compound used is preferably 2: 1 to 3: 1 in terms of lithium ion and silicate ion, and is preferably 2: 1 to 2.5: 1. Is more preferable.

  The amount of water used is preferably from 10 to 50 mol, more preferably from 13 to 30 mol, based on 1 mol of silicate ion of the silicate compound, from the viewpoints of solubility of the raw material compound, ease of stirring, synthesis efficiency, and the like. Particularly preferred is 15 to 20 mol.

The order of adding the respective raw materials is not particularly limited. In addition, an antioxidant may be added to the mixture slurry as necessary, and as the antioxidant, hydrosulfite sodium (Na ₂ S ₂ O ₄ ), aqueous ammonia, sodium sulfite and the like can be used. The content of the antioxidant in the aqueous dispersion is preferably equal to or less than the equimolar amount with respect to the transition metal because it suppresses the formation of the olivine-type silicate compound containing the transition metal (M) when added in a large amount. The molar ratio with respect to ions is more preferably 0.5 or less.

It is preferable that the mixture slurry of these components is basic in order to prevent side reactions and dissolve the silicate compound. The pH of the mixture slurry may be basic, but it is 12.0 to 13.5 to prevent side reactions (generation of transition metal oxides, etc.), solubility of silicate compounds, and progress of the reaction. Particularly preferred in terms. The pH of the mixture slurry may be adjusted by adding a base such as sodium hydroxide, but it is particularly preferable to use Na ₄ SiO ₄ as the silicate compound.

  In the method of the present invention, the mixture slurry is hydrothermally reacted in an autoclave, which is a saturated steam produced by heating water having a dissolved oxygen concentration of 1.0 mg / L or less. That is, for example, as shown in FIG. 1, a hydrothermal reaction is performed using a steam autoclave. Since the steam autoclave receives saturated steam and pressurizes and heats, the steam autoclave is filled with saturated steam. Saturated steam is produced by heating water, but it is preferable to deoxidize the water used in the boiler for heating the water. The water for producing the steam preferably has a dissolved oxygen concentration of 1.0 mg / L or less, and particularly preferably has a dissolved oxygen concentration of 0.5 mg / L or less. Such deoxidized water can be easily produced by, for example, bubbling nitrogen gas in water or using a membrane separation device.

  Since water used for the production of saturated steam does not contain oxygen, oxidation of the transition metal can be prevented in the autoclave during hydrothermal synthesis. Further, even if the saturated steam is cooled, no water (drain water) is generated, so that iron is not oxidized in the process. When the saturated steam is introduced into the autoclave and heating is started, it is preferable to further reduce the oxygen remaining in the autoclave by performing an operation to push out (replace) the air in the autoclave with the saturated steam.

  The hydrothermal reaction may be sealed in a steam autoclave and heated to 130 ° C. or higher. A more preferable reaction temperature is 130 to 220 ° C, and further preferably 140 to 200 ° C. The pressure only needs to be sealed in an autoclave and heated with steam, and is theoretically about 1.0 to 1.6 MPa. The heating time is preferably 1 to 24 hours, more preferably 2 to 12 hours.

  After completion of the hydrothermal reaction, the produced olivine-type silicate compound is preferably collected by filtration and washed. Washing is preferably performed with water using a filtration device having a cake washing function. The obtained crystals are dried if necessary. Examples of the drying means include spray drying, vacuum drying, freeze drying and the like.

The olivine-type silicate compound containing the obtained transition metal (M) is specifically represented by any of the following formulas (1) to (5). In addition, Li ₂ FeSiO ₄ is not included in the olivine type silicate compound.
Li ₂ M'SiO ₄ (1)
(In the formula, M ′ represents one or more selected from Ni, Co and Mn.)
_{Li a 'Fe x Mn y Al} z SiO 4 ··· (2)
(Where, a ′, x, y and z are 1 <a ′ ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <2/3, a ′ + 2x + 2y + 3z = 4, and x + y ≠ Indicates a number satisfying 0.)
_{Li a "Fe x Mn y V} z 'SiO 4 ··· (3)
(Where a ^" , x, y and z 'are 1 <a ^" ≤2, 0≤x <1, 0≤y <1, 0 <z'<1, a ^" + 2x + 2y + (2-5) z '= 4 and a number satisfying x + y ≠ 0.)
_{Li a "Fe x Mn y Zr} z" SiO 4 ··· (4)
(Where a ^" , x, y and z ^" are 1 <a ^" ≤2, 0≤x <1, 0≤y <1, 0 <z ^" <0.5, a ^" + 2x + 2y + 4z ^" = 4, And a number satisfying x + y ≠ 0.)
_{Li 2 Fe x Mn y Zn q} SiO 4 ··· (5)
(In the formula, x, y, and q represent numbers satisfying 0 ≦ x <1, 0 ≦ y <1, 0 <q <1, x + y + q = 1, and x + y ≠ 0.)

The obtained olivine-type silicate compound containing a transition metal (M) can be used as a positive electrode material for a lithium ion battery by supporting carbon and then firing it. For carbon support, a carbon source such as glucose, fructose, polyethylene glycol, polyvinyl alcohol, carboxymethylcellulose, saccharose, starch, dextrin, citric acid, and the like may be added to an olivine-type silicate compound and then calcined. The firing conditions are 400 ° C. or higher, preferably 400 to 800 ° C. for 10 minutes to 3 hours, preferably 0.5 to 1.5 hours under an inert gas atmosphere or reducing conditions. By this treatment, a positive electrode material in which carbon is supported on the olivine type silicate compound surface can be obtained. The amount of the carbon source used is preferably 3 to 15 parts by mass as carbon contained in the carbon source and more preferably 5 to 10 parts by mass as carbon contained in the carbon source with respect to 100 parts by mass of Li ₂ FeSiO ₄ .

  The olivine-type silicate compound containing the transition metal (M) obtained by the method of the present invention is useful as a positive electrode material for a lithium ion secondary battery because the particle size is fine and uniform. Next, a lithium ion secondary battery containing the olivine type silicate compound obtained by the method of the present invention as a positive electrode material will be described.

  The lithium ion secondary battery to which the positive electrode material of the present invention can be applied is not particularly limited as long as it has a positive electrode, a negative electrode, an electrolytic solution, and a separator as essential components.

  Here, as long as lithium ions can be occluded at the time of charging and released at the time of discharging, the material structure is not particularly limited, and a known material structure can be used. For example, a carbon material such as lithium metal, graphite, or amorphous carbon. It is preferable to use an electrode formed of an intercalating material capable of electrochemically inserting and extracting lithium, particularly a carbon material.

  The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones An oxolane compound or the like can be used.

The type of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , LiC (SO ₃ CF ₃ ) ₂ and LiN (SO ₃ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ and LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and organic salt derivatives It is preferable that it is at least 1 type of these.

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to this.

[Example 1]
_{LiOH · H 2 O 420g (10mol} ), Na 4 SiO 4 · nH 2 O 140g (5mol) of ion-exchanged water 7500Cm ³ was added to, and stirred for 12 hours to obtain dispersion (A). Also, 7500 cm ³ of ion exchange water was added to 300 g (5 mol) of 28% ammonia water, and after bubbling nitrogen gas, 626 g (2.25 mol) of FeSO ₄ .7H ₂ O, 542 g (2.25 mol) of MnSO ₄ .5H ₂ O And 71 g (0.25 mol) of Zr (SO ₄ ) ₂ .4H ₂ O were added and stirred for 0.5 hour to obtain a dispersion (B). Next, the dispersion (A) and the dispersion (B) were mixed and stirred for 10 minutes while bubbling nitrogen gas. The obtained liquid mixture was thrown into the synthesis container installed in the steam heating type autoclave of FIG. The inside of the autoclave was heated at 150 ° C. for 12 hours using saturated steam obtained by heating water with a dissolved oxygen concentration of less than 0.5 mg / L by a membrane separator. The stirring of the slurry in the container was continued during the heating. The pressure in the autoclave was 0.48 MPa. The formed crystals were filtered and then washed with water. The washed crystal was vacuum dried at 60 ° C. and 1 Torr. 8.4 g of the obtained powder was taken, glucose (10% as carbon concentration) and 10 cm ³ of ultrapure water were added thereto, and calcined at 600 ° C. for 1 hr in a reducing atmosphere. FIG. 2 shows an SEM image of the obtained powder (Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ ), and FIG. 3 shows an XRD chart. The primary particle size of the obtained olivine type silicate compound was in the range of 40 to 70 nm, and the particle size was uniform. Moreover, the obtained crystal was a single phase of Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ .

[Comparative Example 1]
A raw material slurry was prepared in the same procedure as in Example 1, and charged into a synthesis container installed in a steam heating autoclave. Next, saturated steam generated using water not subjected to a dissolved oxygen reduction treatment (dissolved oxygen concentration of 8 to 10 mg / L) was introduced into an autoclave and heated at 150 ° C. for 12 hours. The produced crystal was treated in the same procedure as in Example 1 to obtain an olivine-type silicate compound powder. FIG. 2 shows an SEM image of the obtained powder (Li ₂ Fe _0.45 Mn _0.45 Zr _0.05 SiO ₄ ), and FIG. 3 shows an XRD chart. The obtained olivine-type silicate compound had a non-uniform particle shape, and the obtained olivine-type silicate compound contained an impurity phase, and a single-phase composition was not obtained.

[Example 2]
_{LiOH · H 2 O 420g (10mol} ), Na 4 SiO 4 · nH 2 O 140g (5mol) of ion-exchanged water 7500Cm ³ was added to, and stirred for 12 hours to obtain dispersion (A). Also, 7500 cm ³ of ion exchange water was added to 300 g (5 mol) of 28% ammonia water, and after bubbling nitrogen gas, 626 g (2.25 mol) of FeSO ₄ .7H ₂ O, 542 g (2.25 mol) of MnSO ₄ .5H ₂ O And 131 g (0.5 mol) of ZnSO ₄ .7H ₂ O was added and stirred for 0.5 hour to obtain a dispersion (B). Next, the dispersion (A) and the dispersion (B) were mixed and stirred for 10 minutes while bubbling nitrogen gas. The obtained liquid mixture was thrown into the synthesis container installed in the steam heating type autoclave of FIG. The inside of the autoclave was heated at 150 ° C. for 12 hours using saturated steam obtained by heating water with a dissolved oxygen concentration of less than 0.5 mg / L by a membrane separator. The stirring of the slurry in the container was continued during the heating. The pressure in the autoclave was 0.48 MPa. The formed crystals were filtered and then washed with water. The washed crystal was vacuum dried at 60 ° C. and 1 Torr. 8.4 g of the obtained powder was taken, glucose (10% as carbon concentration) and 10 cm ³ of ultrapure water were added thereto, and calcined at 600 ° C. for 1 hr in a reducing atmosphere. FIG. 4 shows an SEM image of the obtained powder (Li ₂ Fe _0.45 Mn _0.45 Zn _0.05 SiO ₄ ), and FIG. 5 shows an XRD chart. The obtained olivine-type silicate compound had a particle size in the range of 60 to 90 nm and a uniform particle size. The obtained crystal was a single phase of Li ₂ Fe _0.45 Mn _0.45 Zn _0.05 SiO ₄ .

[Comparative Example 2]
A raw material slurry was prepared in the same procedure as in Example 2, and charged into a synthesis container installed in a steam heating autoclave. Next, saturated steam generated using water not subjected to a dissolved oxygen reduction treatment (dissolved oxygen concentration of 8 to 10 mg / L) was introduced into an autoclave and heated at 150 ° C. for 12 hours. The produced crystal was treated in the same procedure as in Example 2 to obtain an olivine-type silicate compound powder. FIG. 4 shows an SEM image of the obtained powder (Li ₂ Fe _0.45 Mn _0.45 Zn _0.05 SiO ₄ ), and FIG. 5 shows an XRD chart. The obtained olivine-type silicate compound had a non-uniform particle shape, and the obtained olivine-type silicate compound contained an impurity phase, and a single-phase composition was not obtained.

[Example 3]
_{LiOH · H 2 O 420g (10mol} ), Na 4 SiO 4 · nH 2 O 140g (5mol), and Al (OH) ₃ of ion-exchanged water 7500Cm ³ was added to 25.7 g (0.33 mol), and stirred for 12 hours A dispersion (A) was obtained. Also, 7500 cm ³ of ion exchange water was added to 300 g (5 mol) of 28% ammonia water, and after bubbling nitrogen gas, 1390 g (5 mol) of FeSO ₄ .7H ₂ O and 844 g (3.5 mol) of MnSO ₄ .5H ₂ O were added. The mixture was added and stirred for 0.5 hour to obtain a dispersion (B). Next, the dispersion (A) and the dispersion (B) were mixed and stirred for 10 minutes while bubbling nitrogen gas. The obtained liquid mixture was thrown into the synthesis container installed in the steam heating type autoclave of FIG. The inside of the autoclave was heated at 170 ° C. for 9 hours using saturated steam obtained by heating water having a dissolved oxygen concentration of less than 0.5 mg / L using a membrane separator. The stirring of the slurry in the container was continued during the heating. The internal pressure of the autoclave was 0.8 MPa. The formed crystals were filtered and then washed with water. The washed crystal was vacuum dried at 60 ° C. and 1 Torr. 8.4 g of the obtained powder was taken, glucose (10% as carbon concentration) and 10 cm ³ of ultrapure water were added thereto, and calcined at 600 ° C. for 1 hr in a reducing atmosphere. FIG. 6 shows an SEM image of the obtained powder (Li ₂ Fe _0.3 Mn _0.7 Al _0.066 SiO ₄ ), and FIG. 7 shows an XRD chart. The obtained olivine-type silicate compound had a particle size in the range of 50 to 80 nm and a uniform particle size. The obtained crystal was a single phase of Li ₂ Fe _0.3 Mn _0.7 Al _0.066 SiO ₄ .

[Comparative Example 3]
A raw material slurry was prepared in the same procedure as in Example 1, and charged into a synthesis container installed in a steam heating autoclave. Next, saturated steam generated using water not subjected to the dissolved oxygen reduction treatment (dissolved oxygen concentration of 8 to 10 mg / L) was introduced into the autoclave and heated at 170 ° C. for 9 hours. The produced crystal was treated in the same procedure as in Example 3 to obtain an olivine-type silicate compound powder. FIG. 6 shows an SEM image of the obtained powder (Li ₂ Fe _0.3 Mn _0.7 Al _0.066 SiO ₄ ), and FIG. 7 shows an XRD chart. The obtained olivine-type silicate compound had a non-uniform particle shape, and the obtained olivine-type silicate compound contained an impurity phase, and a single-phase composition was not obtained.

[Example 4, Comparative Example 4]
Using the materials obtained in Example 1 and Comparative Example 1 as positive electrode materials, the batteries of Example 4 and Comparative Example 4 were produced.
The fired product obtained in Example 1 and Comparative Example 1, ketjen black (conductive agent), and polyvinylidene fluoride (binding agent) were mixed at a mixing ratio of 75:15:10, and this was mixed with N-methyl. -2-Pyrrolidone was added and sufficiently kneaded to prepare a positive electrode slurry. The positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours. Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.
Next, a coin-type lithium ion secondary battery was constructed using the positive electrode. A lithium foil punched to φ15 mm was used for the negative electrode. As the electrolytic solution, a solution obtained by dissolving LIPF ₆ at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 1 was used. As the separator, a known one such as a polymer porous film such as polypropylene was used. These battery components were assembled and housed in a conventional manner in an atmosphere with a dew point of −50 ° C. or lower to produce a coin-type lithium secondary battery (CR-2032).
A charge / discharge test at a constant current density was performed using the manufactured lithium ion secondary battery. The charging conditions at this time were constant current charging with a current of 0.1 CA (33 mAg) and a voltage of 4.5 V, and the discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 1.5 V. All temperatures were 30 ° C.
The discharge characteristics are shown in FIG. 8 from the results of the charge / discharge test. As a result, the battery of Example 4 using the positive electrode material of Example 1 showed excellent charge / discharge capacity, but the charge / discharge capacity of the battery of Comparative Example 4 using the material of Comparative Example 1 was not sufficient. .

[Example 5, Comparative Example 5]
The batteries obtained in Example 5 and Comparative Example 5 were fabricated in the same manner as in Example 4 using the materials obtained in Example 2 and Comparative Example 2 as the positive electrode material. The charging conditions were constant current charging with a current of 0.1 CA (33 mAg) and a voltage of 4.5 V, and the discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 1.5 V. All temperatures were 30 ° C.
FIG. 9 shows the discharge characteristics from the results of the charge / discharge test. As a result, the battery of Example 5 using the positive electrode material of Example 2 showed excellent charge / discharge capacity, but the charge / discharge capacity of the battery of Comparative Example 5 using the material of Comparative Example 2 was not sufficient. .

[Example 6, Comparative Example 6]
The batteries obtained in Example 5 and Comparative Example 5 were fabricated in the same manner as in Example 4 using the materials obtained in Example 3 and Comparative Example 3 as the positive electrode material. The charging conditions were constant current charging with a current of 0.1 CA (33 mAg) and a voltage of 4.5 V, and the discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 1.5 V. All temperatures were 30 ° C.
The discharge characteristics are shown in FIG. 10 from the results of the charge / discharge test. As a result, the battery of Example 5 using the positive electrode material of Example 2 showed excellent charge / discharge capacity, but the charge / discharge capacity of the battery of Comparative Example 5 using the material of Comparative Example 2 was not sufficient. .

Claims (4)

  (A) transition metal (M) compound (M represents Fe, Ni, Co, Al, Zn, V, Zr or Mn), (B) silicate compound, (C) lithium compound, and (D) water A transition metal (M), characterized in that a mixture slurry containing a hydrothermal reaction in a steam autoclave which is a saturated steam produced by heating water having a dissolved oxygen concentration of 1.0 mg / L or less as a heat source. ) Containing olivine-type silicate compounds other than lithium iron silicate.   The manufacturing method according to claim 1 whose dissolved oxygen concentration in said mixed slurry is 1.0 mg / L or less.   The method according to claim 1 or 2, wherein the hydrothermal reaction is performed under conditions of 130 to 220 ° C.   A lithium ion secondary battery containing, as a positive electrode material, an olivine-type silicate compound other than lithium iron silicate containing the transition metal (M) obtained by the production method according to claim 1.