JP2012204307A - Positive electrode active material, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing technology for inexpensively manufacturing a positive electrode active material having sufficient charging and discharging capacity.SOLUTION: A method for manufacturing a positive electrode active material is a method for manufacturing an active material that contains lithium and fluorine as constituent elements and becomes a positive electrode of a nonaqueous electrolyte secondary battery. The method comprises the step of obtaining the positive electrode active material by dipping a solid object that contains sodium and fluorine as the constituent elements and becomes a precursor of the positive electrode active material into an organic solvent containing an electrolyte which contains lithium. The electrolyte containing lithium, and the organic solvent are used as an electrolytic solution of a nonaqueous electrolyte lithium ion secondary battery.

Description

  The present invention belongs to the technical field of non-aqueous electrolyte secondary batteries, and particularly relates to a novel production method for efficiently producing a positive electrode active material containing lithium element at low cost and the positive electrode active material.

  A lithium ion secondary battery using a non-aqueous electrolyte mainly uses a positive electrode active material containing a lithium element as a positive electrode, and has been actively researched and developed as a battery capable of achieving a high energy density at a high voltage.

However, a positive electrode active material (lithium salt) containing a lithium element generally has a problem that synthesis is more difficult than a positive electrode active material (sodium salt) containing a sodium element. For example, as a cathode active material, NaFeF ₃ (theoretical capacity 197 mAh / g) but is synthesized, LiFeF ₃ (theoretical capacity 224mAh / g) is not directly synthesized so far. This is presumably because the atomic size of the sodium element is larger than the lithium element.

Further, in recent years, application to a power source for a hybrid vehicle or an electric vehicle has been studied, and development of a large capacity and economical large lithium ion secondary battery is required. As a positive electrode of a large lithium ion secondary battery, a positive electrode having a rare metal-free olivine type crystal structure typified by LiFePO ₄ is attracting attention, but due to the large molecular weight of polyanion, its theoretical capacity is about 170 mAh / g At rest. If a positive electrode active material containing 2Li in one molecule can be produced, it is considered that this capacity limitation can be eliminated and the theoretical capacity can be increased.

As a positive electrode active material containing 2Li in one molecule, for example, a fluorinated polyanion Li ₂ FePO ₄ F having a theoretical capacity of 300 mAh / g can be mentioned, but its synthesis is difficult and so far not sufficiently synthesized. . For example, an attempt has been made to produce Li ₂ FePO ₄ F by partially replacing the sodium element of Na ₂ FePO ₄ F with lithium element, but the substantial lithium content is only about 90%. (Refer nonpatent literature 1).

B. L. Ellis, W. R. M. Makahnouk, Y. Makimura, K. Toghill & L. F. Nazar, Nature Materials 6, 749-753 (2007)

As described above, in the conventional technique, there is a problem that synthesis of a positive electrode active material containing a lithium element is difficult as compared with a positive electrode active material containing a sodium element. Furthermore, in the prior art, means for obtaining a lithium salt containing as much lithium element as possible as the positive electrode active material (for example, containing 2Li in one molecule like Li ₂ FePO ₄ F) has been established. However, there is a problem that the theoretical capacity of the positive electrode active material has not been increased.

  The present invention has been proposed to solve the above problems, and by using a sodium salt that is easy to synthesize, a positive electrode active material containing lithium element, which has been difficult to synthesize in the past, can be easily produced. In particular, an object is to provide a technique for increasing the theoretical capacity by selecting a positive electrode active material.

  As a result of intensive studies, the present inventors have made use of ion exchange to produce a positive electrode active material containing a lithium element suitable for a secondary battery using a non-aqueous electrolyte from a sodium salt that is easy to synthesize. Newly found. Furthermore, it has been found that a non-aqueous electrolyte secondary battery with high operational stability can be constructed by selecting and combining negative electrode active materials using this positive electrode active material.

  Thus, according to the present invention, there is provided a method for producing an active material containing lithium and fluorine as constituent elements and serving as a positive electrode of a non-aqueous electrolyte secondary battery, comprising sodium and fluorine as constituent elements, the precursor of the positive electrode active material. A solid body is immersed in an organic solvent containing an electrolyte containing lithium element to obtain the positive electrode active material, and the electrolyte containing lithium element and the organic solvent are non-aqueous electrolyte lithium ion secondary Provided is a method for producing a positive electrode active material, which is used as an electrolytic solution for a battery.

  Moreover, according to this invention, the positive electrode active material for nonaqueous electrolyte secondary batteries manufactured by said method is also provided. Furthermore, according to this invention, the nonaqueous electrolyte secondary battery using said positive electrode active material is also provided.

The schematic of the pellet electrode and coating electrode which concern on this invention is shown. XRD patterns result of the positive electrode active material Li ₂ FePO ₄ F produced by the present invention, showing the atomic absorption and the charge-discharge test results. XRD patterns result of the positive electrode active material LiFeF ₃ produced by the present invention, showing the relationship diagram of atomic absorption results and exchange processing time and the ion exchange reaction. It shows a charge-discharge test results of the positive electrode active material LiFeF ₃ produced by the present invention.

  According to the present invention, a solid (precursor solid) that contains sodium and fluorine as constituent elements (for non-aqueous electrolyte secondary batteries and contains lithium and fluorine as constituent elements) as a precursor of the positive electrode active material, The positive electrode active material can be manufactured by immersing in an organic solvent containing an electrolyte containing lithium element (used as an electrolyte for a non-aqueous electrolyte secondary battery). That is, by immersing the precursor solid as a raw material in an organic solvent containing an electrolyte containing lithium element, the sodium element contained in the precursor solid is ion-exchanged to lithium element as much as possible, and this is the purpose. A crystalline or amorphous positive electrode active material containing lithium element and fluorine element is obtained.

  In order to increase the efficiency of ion exchange, it is generally preferable to stir for several days in an inert gas atmosphere such as nitrogen gas or argon gas. The stirring period is preferably about 5 to 15 days. The temperature at the time of stirring is preferably from room temperature to 100 ° C., but from the viewpoint of increasing the reactivity, it is more preferably higher than normal temperature, for example, 80 ° C. As the inert gas, it is preferable to use argon gas because of easy handling.

  As described above, the feature of the present invention is an object by using a very simple method of performing ion exchange at a relatively low temperature by using a normal electrolyte solution for a non-aqueous electrolyte lithium ion secondary battery as it is. The object is to obtain a positive electrode active material containing lithium element and fluorine element. Furthermore, in the case of a precursor solid in which the total number of sodium and lithium elements is 2 or more in one molecule, the sodium element contained in the precursor solid is ion-exchanged to the lithium element as much as possible. A positive electrode active material containing one or more lithium elements (1Li) in one molecule can be produced, and the theoretical capacity of the positive electrode active material can be increased.

Further, the precursor solid is a so-called sodium salt, and its atomic size is larger than that of the lithium salt. Therefore, in general, the precursor solid is generally more easily synthesized than the lithium salt (that is, the positive electrode active material produced according to the present invention). For these reasons, the present invention can be applied to a wide range of subjects as exemplified below, and it has been difficult to synthesize using sodium salts (precursor solids) that are relatively easy to synthesize. Various positive electrode active materials containing lithium element can be simply produced.

The precursor solid and the positive electrode active material precursor solid are not limited as long as they are solids containing sodium element and fluorine element. For example, Na ₂ FePO ₄ F, LiNaFePO ₄ F, NaFeF ₃ , NaMnF ₃ , Na ₂ CoPO ₄ Mention may be made of F, Na ₂ NiPO ₄ F, Na ₂ TiF ₆ , Na ₃ FeF ₆ , NaVPO ₄ F and LiNaMnPO ₄ F. According to the present invention, these precursor solid sodium elements are ion-exchanged with lithium elements, and the positive electrode active materials are Li ₂ FePO ₄ F, Li ₂ FePO ₄ F, LiFeF ₃ , LiMnF ₃ , and Li ₂ CoPO, respectively. ₄ F, Li ₂ NiPO ₄ F, Li ₂ TiF ₆ , Li ₃ FeF ₆ , LiVPO ₄ F and Li ₂ MnPO ₄ F can be obtained.

Among them, those suitable for use in large batteries such as in-vehicle use are those containing manganese element or iron element, and for example, precursor solid Na ₂ FePO ₄ F, LiNaFePO ₄ F, NaFeF ₃ , NaMnF ₃ are preferable. As the positive electrode active material, Li ₂ FePO ₄ F, Li ₂ FePO ₄ F, LiFeF ₃ , and LiMnF ₃ can be obtained, respectively. Furthermore, from the viewpoint of increasing the theoretical capacity of the positive electrode active material, a precursor solid Na ₂ FePO ₄ F or LiNaFePO ₄ F in which the total number of sodium elements and lithium elements in one molecule is two atoms is preferable, and the positive electrode active material Li ₂ FePO ₄ F can be obtained as

Organic solvent Non-aqueous solvent type electrolyte The organic solvent (non-aqueous solvent) used as the electrolyte of the lithium ion secondary battery is used as it is, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), A carbonate ester solvent such as propylene carbonate (PC) can be used. As a particularly preferable one, for example, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) can be used. Even if it is an organic solvent which melt | dissolves lithium salt, what is not used as electrolyte solution of a lithium ion secondary battery (for example, acetonitrile) is unsuitable. For example, a nitrile system having a cyano group such as acetonitrile generates cyan gas at the time of combustion, and is not suitable as an electrolyte from the viewpoint of toxicity.

Electrolyte containing lithium element The electrolyte containing lithium element is not limited as long as the lithium ion can move between the electrodes in the above organic solvent and is used in a lithium ion secondary battery. For example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ³ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) ₂ , LiN (SO _{2 C 2 F 5) 2, LiC} (SO 2 CF 3) 3, LiN (SO 3 CF 3) 2 can be cited. By using the electrolyte as it is in the secondary battery to be constructed, it is preferable that an extra solvent drying and removing operation step such as washing and heating can be omitted. Examples of such an electrolyte include LiPF ₆ and LiBF _4. , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) ₂ it can. Particularly preferred is lithium hexafluorophosphate (LiPF ₆ ), which does not easily undergo oxidative decomposition, has high conductivity in a non-aqueous electrolyte, and is widely used in actual lithium ion secondary batteries.

LiBr and LiCl are lithium salts, but are not suitable as the solute of the electrolyte. This is because Br and Cl have an anion radius that is too small, so that ion dissociation is suppressed due to electrostatic attraction with Li, and many solutes cannot be completely dissolved in the electrolyte solvent.

According to the present invention, as an example, when the raw material precursor solid is LiNaFePO ₄ , NaFeF ₃ , or NaMnF ₃ , a positive electrode active material Li ₂ for a nonaqueous electrolyte secondary battery is obtained by the following ion exchange reaction. It is thought that FePO ₄ F, LiFeF ₃ , and LiMnF ₃ are generated. Li ₂ FePO ₄ F can be produced from the following precursor solid LiNaFePO ₄ F, but can also be produced from the precursor solid Na ₂ FePO ₄ F in the same manner.

[Chemical formula 1]
LiNaFePO ₄ F + Li ⁺ → Li ₂ FePO ₄ F + Na ⁺
[Chemical 2]
NaFeF ₃ + Li ⁺ → LiFeF ₃ + Na ⁺
[Chemical formula 3]
NaMnF ₃ + Li ⁺ → LiMnF ₃ + Na ⁺
As the positive electrode of the non-aqueous electrolyte secondary battery, the above positive electrode active material may be used as it is, but in order to improve the rate characteristics of the electrode, a composite with a known conductive material may be formed.

  That is, according to the present invention, from the viewpoint of improving rate characteristics, the positive electrode active material obtained by the above ion exchange can be carbon coated by pulverizing and mixing together with carbon fine particles in an inert gas atmosphere. it can. As the carbon fine particles, furnace black, channel black, acetylene black, thermal black, and the like can be used, but acetylene black is preferred because of its high conductivity when used as an electrode. As the inert gas, nitrogen gas, argon gas, or the like can be used. For example, argon gas can be used.

  Specific means applied to the pulverization / mixing at the time of carbon coating are not particularly limited, and various means conventionally used for the purpose of pulverization / mixing of solid substances can be applied, A ball mill is preferable, and among these, a planetary ball milling is preferably used because the raw materials can be sufficiently pulverized and mixed.

  According to this invention, the secondary battery positive electrode containing the positive electrode active material obtained as mentioned above and the secondary battery which combined the negative electrode with this positive electrode are provided.

  When the positive electrode according to the present invention is manufactured, a known electrode manufacturing method may be followed except that the positive electrode active material described above is used. For example, the active material powder is mixed with a known binder such as polyethylene, if necessary, and a known conductive material such as acetylene black, if necessary, and the resulting mixed powder is made of stainless steel or the like. It can be pressure-molded on the support or filled into a metal container. An example of such a positive electrode is a pellet electrode. As a pellet electrode, as shown to Fig.1 (a), it can comprise from the pellet electrode 10a, the spacer 11a, the coin cell container (lower lid) 12, and the titanium mesh 13 made from titanium, for example. The pellet electrode 10a can have a thickness of 10 mm, for example. The spacer 11 a mounts the titanium mesh 13 and mounts the pellet electrode 10 a on the titanium mesh 13.

In addition, for example, the positive electrode of the present invention can also be produced by a method such as applying a slurry obtained by mixing the mixed powder with an organic solvent such as toluene onto a metal substrate such as aluminum, nickel, stainless steel, or copper. Can do. An example of such a positive electrode is a coated electrode. As the application electrode, for example, as shown in FIG. 1B, the application electrode 10b and the spacer 11b are used.
And a coin cell container (lower lid) 12. The coating electrode 10b can have an electrode diameter of 10 mm, for example. As for the spacer 11b, the coating electrode 10b is spot-welded in the center part of the upper surface.

  As the negative electrode (negative electrode active material) used in combination with the above positive electrode, sodium or lithium, a compound or alloy of an alkali metal thereof, or the like can be used, and a carbonaceous material can also be used. As the carbonaceous material used for the negative electrode according to the present invention, a graphite (graphite-based) carbon body is preferable. In addition, hard carbon obtained by firing various polymers is also used, but is not limited thereto. It is not a thing. Furthermore, these carbonaceous materials may be used in combination of two or more.

The negative electrode may be manufactured by a known method. For example, the negative electrode can be manufactured in the same manner as described above in relation to the positive electrode. That is, for example, if necessary, the negative electrode active material powder is mixed with the known binder described above and, if necessary, the known conductive material described above, and then the mixed powder is formed into a sheet shape. Then, this may be pressure-bonded to a conductor network (current collector) such as stainless steel or copper. Moreover, for example, it can also be produced by applying a slurry obtained by mixing the above mixed powder with the above-mentioned known organic solvent on a metal substrate such as copper.
As another component, what is used for a well-known nonaqueous electrolyte secondary battery can be used as a component. For example, the following can be illustrated.

  The electrolytic solution usually includes an electrolyte and a solvent. The solvent of the electrolytic solution is not particularly limited as long as it is non-aqueous, for example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, ethers, amines, Esters, amides, phosphate ester compounds and the like can be used. Examples of these are 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene carbonate, vinylene carbonate, methyl formate, dimethyl sulfoxide, propylene carbonate, γ-butyrolactone, dimethylformamide. Dimethyl carbonate, diethyl carbonate, sulfolane, ethyl methyl carbonate, 1,4-dioxane, 4-methyl-2-pentanone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane , Propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, trimethyl phosphate, triethyl phosphate and the like. These can be used by 1 type (s) or 2 or more types, for example, can use dimethyl carbonate and ethylene carbonate.

As an electrolyte contained in the electrolytic solution, an electrolyte capable of performing migration for causing an alkali metal ion in the negative electrode active material to electrochemically react with the positive electrode active material and the negative electrode active material, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ³ Li, CF ₃ SO ₃ Li, LiN (SO ₂ CF ₃ ) ₂ , LiN (SO _{2 C 2 F 5) 2,} LiC (SO 2 CF 3) 3, LiN (SO 3 CF 3) 2, NaClO 4, NaPF 6, NaBF 4, NaCF 3 SO 3, NaAsF 6, NaB (C 6 H 5) ₄ , NaCl, NaBr, CH ₃ SO ³ Na, CF ₃ SO ₃ Na, NaN (SO ₂ CF ₃ ) ₂ , NaN (SO ₂ C ₂ F ₅ ) ₂ , NaC (SO ₂ CF ₃ ) ₃ , NaN (SO ₃ CF ₃₎ using the _2, etc. It can be. From the viewpoint of reducing the manufacturing cost, it is preferable to use the same electrolyte as that used for manufacturing the battery. In particular, lithium hexafluorophosphate (LiPF ₆ ) widely used as the battery electrolyte is used. Is preferred.

In the nonaqueous electrolyte secondary battery according to the present invention, various conventionally known materials can be used for elements such as a separator, a battery case, and other structural materials, and there is no particular limitation. What is necessary is just to assemble the non-aqueous electrolyte secondary battery which concerns on this invention according to a well-known method using said battery element. In this case, the shape of the battery is not particularly limited, and various shapes and sizes such as a cylindrical shape, a square shape, and a coin shape can be appropriately employed.

EXAMPLES Examples will be described below to more specifically illustrate the features of the present invention, but the present invention is not limited to the following examples.
Example 1
Production of Li ₂ FePO ₄ F First, as a starting material, sodium fluoride (NaF, manufactured by Nacalai Tesque 99.1%) as a fluorine source and LiFePO ₄ separately solid-phase synthesized were mixed and ground for 10 minutes in a mortar. The powder was heated and melted at 1300 ° C. in an argon atmosphere using a single roll melting and quenching apparatus and then quenched to obtain an amorphous body. An annealing treatment was performed at 500 ° C. for 3 hours under an argon atmosphere to obtain a LiNaFePO ₄ F crystal sample as a precursor solid.

Using 1 mol / dm ³ LiPF ₆ / EC: DMC (volume ratio 1: 1) as a lithium source (manufactured by Toyama Pharmaceutical Co., Ltd.), in a glove box (manufactured by Takasugi Seisakusho Co., Ltd.) under an argon atmosphere, LiNaFePO ₄ F: (LiPF ₆ / EC: DMC) = 1: 40 was weighed at a molar ratio and stirred at 80 ^° C. for 5 days to synthesize Li ₂ FePO ₄ F. A hot stirrer (manufactured by ASONE, DP-1M) was used for heating and stirring. Centrifugation for 10 minutes was performed 3 times using a centrifuge. The resulting precipitate was dried overnight at 80 ° C. to obtain a composite.

(Production of coin cell)
The LiFeF ₃ crystal sample and acetylene black (AB) were each composited at a weight ratio of 70:25, and the LiFeF ₃ / C composite and the binder (PTFE) were mixed at a weight ratio of 95: 5. The positive electrode was molded into a pellet. A coin cell was produced in a dry box under an argon atmosphere using lithium metal as a negative electrode and 1 mol / dm ³ LiPF ₆ EC + DMC (volume ratio 1: 1) as an electrolyte.

(XRD measurement)
FIG. 2 (a) shows the XRD pattern results of LiNaFePO ₄ F as a starting material and the obtained sample. 5 mg of the powder before and after ion exchange was dissolved in hydrochloric acid and diluted with water to obtain a sample solution. After the AB / LiFeF3 composite was washed, XRD measurement was performed in a glove box under an argon atmosphere. XRD measurement uses an XRD diffractometer (RINT-TTRIII, manufactured by Rigaku), scanning range 20 ° -50 °, scanning speed 0.06 ° / min, X-ray 50kV / 300mA, scanning mode 2θ / θ, sampling width 0.01 It was performed under the condition of °.

The XRD measurement results showed good agreement with the XRD pattern of Li ₂ NiPO ₄ F having an orthorhombic structure (space group Pnma). Furthermore, the results of atomic absorption measurement of Li, Na, and Fe using the polarized Zeeman atomic absorption spectrophotometer [Z-5310, manufactured by Hitachi High-Technologies Corporation] for the obtained sample are shown in FIG. Shown in (b). From FIG. 5B, it was found that all sodium elements were ion-exchanged to lithium elements by ion exchange. From the above results, it was found that Li ₂ FePO ₄ F having an orthorhombic structure was synthesized by an ion exchange method using 1 mol / dm ³ LiPF ₆ / EC: DMC (volume ratio 1: 1).

(Charge / discharge test)
Using the manufactured coin cell, CCV was charged and discharged using sodium metal as the negative electrode and 1 mol / dm ³ sodium perchlorate / ethylene carbonate + dimethyl carbonate [LiPF ₆ / EC + DMC (volume ratio 1: 1)] as the electrolyte. Went in mode. The current density was 0.068 mA / cm ² and the voltage range was 2.0-4.5V. The charge / discharge curves for the first and second cycles are shown in FIG. From the obtained charge / discharge curve, it was shown that the initial discharge capacity was 160 mAh / g, and the overvoltage was small due to the reaction of one electron or more.

(Example 2)
And NaFeF ₃ 0.33 mmol (45.3mg) which was prepared in Preparative liquid phase of LiFeF ₃ (solvent ratio OA / OAm = 10/10) , 1M LiPF6 / EC + DMC ( volume ratio 1: 1) 40 mmol of (40 mL) It sealed in the glove box (made by Miwa Seisakusho) under argon atmosphere, and stirred at 300 rpm and 80 degreeC for 15 days. A hot stirrer (manufactured by ASONE, DP-1M) was used for heating and stirring. Centrifugation was performed 3 times for 10 minutes using a centrifuge. The resulting precipitate was dried overnight at 80 ° C. to obtain a composite. The resulting precipitate was dried overnight at 80 ° C. to obtain a composite.

(XRD measurement)
A coin cell was produced by the same method as in Example 1 above, and XRD measurement was performed. The result of XRD measurement is shown in FIG. From the diffraction peak, since the electrode immersed in the electrolyte was shifted to a higher angle side, it was found that the structure was changed by ion exchange only by immersing the NaFeF ₃ powder in the electrolyte. The atomic absorption results of the powder obtained by ion exchange are shown in FIG. The relationship between the exchange treatment time and the ion exchange reaction is shown in FIG. About 79% of Na and Li ion exchange was confirmed by stirring for 5 days. About 95% ion exchange was confirmed by stirring for 10 days. About 15% ion exchange was confirmed after 15 days of stirring. From the above results, it was found that LiFeF ₃ was synthesized by an ion exchange method using 1 mol / dm ³ LiPF ₆ / EC: DMC (volume ratio 1: 1).

(Charge / discharge test)
In the produced coin cell, sodium metal for the negative electrode and 1 mol / dm ³ sodium perchlorate / ethylene carbonate + dimethyl carbonate for the electrolyte [ Using LiPF ₆ / EC + DMC (volume ratio 1: 1)], a charge / discharge test was conducted in a CCV mode in a constant temperature bath at 25 ° C. Measurement conditions were such that the charge / discharge current value was a constant current 1/10 C (22.4 mA / g), 1 C (224 mA / g) rate, the voltage range was 2.0-4.5 V, and the rest time was 1 hour. The measurement results are shown in FIG. From this result, the AB / LiFeF3 composite produced according to the present invention has an excellent initial charge capacity of 196 mAh / g and an initial charge capacity of 199 mAh / g, which is almost the same as the discharge. The positive electrode material was obtained by ion exchange. In addition, the discharge capacity improved before ion exchange under all measurement conditions. This is presumed to be because the sodium element contained in the positive electrode active material was reduced by ion exchange, so that interference of the ion insertion and desorption reaction by the sodium element was suppressed.

(Example 3)
Replacing NaFeF ₃ manufacturing the second embodiment of LiMnF ₃ to NaMnF _3, by the same procedure as in Example 2, was synthesized LiMnF ₃ from NaMnF ₃ synthesized by mechanochemical method. A coin cell was produced by the same method as in Example 1 described above. The obtained sample was subjected to atomic absorption measurement for Li, Na, and Fe using a polarized Zeeman atomic absorption photometer (Z-5310, manufactured by Hitachi High-Technologies Corporation), and about 75% by ion exchange. It was found that the sodium element and the lithium element were ion exchanged. From the above results, it was found that LiMnF ₃ was synthesized by an ion exchange method using 1 mol / dm ³ LiPF ₆ / EC: DMC (volume ratio 1: 1).

10a pellet electrode 10b coating electrode 11a spacer 11b spacer 12 coin cell container (lower lid)
13 Titanium mesh

Claims (8)

  A method for producing an active material containing lithium and fluorine as constituent elements and serving as a positive electrode of a non-aqueous electrolyte secondary battery, wherein a solid containing sodium and fluorine as constituent elements and serving as a precursor of the positive electrode active material A step of obtaining the positive electrode active material by immersing in an organic solvent containing an electrolyte containing, wherein the electrolyte containing the lithium element and the organic solvent are used as an electrolyte of a non-aqueous electrolyte lithium ion secondary battery. A method for producing a positive electrode active material, comprising:   The method for producing a positive electrode active material according to claim 1, wherein the electrolyte contains a fluorine element. The method for producing a positive electrode active material according to claim 2, wherein the electrolyte is LiPF ₆ and the organic solvent is composed of ethylene carbonate and dimethyl carbonite. The precursor solid is Na ₂ FePO ₄ F or LiNaFePO ₄ F, and the obtained positive electrode active material is Li ₂ NaFePO ₄ F, The production of the positive electrode active material according to claim 1, Method. The method for producing a positive electrode active material according to claim 1, wherein the precursor solid is NaFeF ₃ , and the obtained positive electrode active material is LiFeF ₃ . The method for producing a positive electrode active material according to claim 1, wherein the precursor solid is NaMnF ₃ , and the obtained positive electrode active material is LiMnF ₃ .   The positive electrode active material for nonaqueous electrolyte secondary batteries manufactured by the method in any one of Claims 1-6.   A nonaqueous electrolyte secondary battery using the positive electrode active material according to claim 7.

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