JP2010170867A - Positive electrode active material for nonaqueous secondary battery, and charge and discharge method of nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a non-aqueous secondary battery which consists of FeF<SB>3</SB>and shows stable charge and discharge characteristics even if FeF<SB>3</SB>is decomposed, and provide a charge and discharge method which is suitable for the non-aqueous secondary battery using the positive electrode active material. <P>SOLUTION: The positive electrode active material consists of FeF<SB>3</SB>powder that is capable of intercalation and desorption of alkali metal ions. The FeF<SB>3</SB>powder is impalpable powder of half-width of 0.2 rad or more of diffraction peak in (012) plane by X-ray diffraction. In the non-aqueous secondary battery having the positive electrode containing this positive electrode active material, charge and discharge is carried out in a voltage range in which reversible redox to generate Fe from FeF<SB>3</SB>by discharge and to regenerate FeF<SB>3</SB>from Fe by charge is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery such as a lithium ion secondary battery, and more particularly to a positive electrode active material for a non-aqueous secondary battery.

  Secondary batteries such as lithium ion secondary batteries are small and have a large capacity, and are therefore used in a wide range of fields such as mobile phones and notebook computers. A lithium ion secondary battery has an active material capable of inserting and removing lithium (Li) in each of a positive electrode and a negative electrode. And it operate | moves because Li ion moves in the electrolyte solution provided between both electrodes.

The performance of the secondary battery depends on the materials of the positive electrode, the negative electrode, and the electrolyte constituting the secondary battery. In particular, research and development of active material materials that form active materials are being actively conducted. As the positive electrode active material, an oxide or composite oxide of a transition metal is often used. For example, Patent Document 1 discloses a positive electrode active material represented by Li _a M ₂ O _{4 -b} F _b containing _a transition metal (M). As specific examples of M, Fe, which is low in toxicity and abundant in resources and inexpensive, is used in addition to general transition metals such as Co, Ni, and Mn. Recently, as disclosed in Patent Document 2 and Patent Document 3, a secondary battery using a transition metal halide as a positive electrode active material has attracted attention. In particular, iron fluoride (FeF ₃ ) has a larger discharge capacity than FeCl ₃ , which is the same transition metal halide. This is because, as described in paragraph [0007] of Patent Document 2, since FeF ₃ has a strong bond between iron and fluorine, the positive electrode active material is difficult to dissolve in the electrolytic solution, and Li ions and the like are inserted. This is because the positive electrode active material is hardly decomposed even if it is used.

JP 2006-190556 A Japanese Patent Laid-Open No. 9-22698 Japanese Patent Laid-Open No. 9-55201

When Li ions are inserted into the positive electrode active material FeF ₃ , it is considered that the reaction proceeds through LiFeF ₃ to a conversion region where it is decomposed into Fe and LiF by further insertion of Li. However, as described above, since FeF ₃ has a strong bond between Fe and F, reaction to the conversion region hardly occurs. In addition, it is difficult to regenerate the original FeF ₃ from the conversion region, which has been considered to cause a decrease in battery performance. Therefore, in Patent Document 2 and Patent Document 3, the voltage range of charge / discharge is a voltage range only in an intercalation region that does not advance the reaction to the conversion region (from 4.5 V to 2 V in the case of a lithium ion secondary battery). ) Was only charged and discharged. In charging / discharging within this voltage range, FeF ₃ inserts and desorbs Li, and only the reaction of FeF ₃ + xLi → Li _x FeF ₃ is performed reversibly, and the bond between Fe and F is maintained. That is, reduction from Fe ³⁺ to Fe ²⁺ is performed during discharging, and oxidation from Fe ²⁺ to Fe ³⁺ is performed during charging.

On the other hand, when the reaction is performed up to the conversion region, FeF ₃ is decomposed and electrolytically reduced from Fe ³⁺ to Fe ⁰ , so that a large increase in capacity of the secondary battery as described in detail later is expected. However, up to now, there has been no idea that FeF ₃ is easily decomposed and that the decomposed FeF ₃ is reversibly regenerated, and the reaction up to the conversion region is rather avoided from the viewpoint of battery performance.

In view of the above problems, it consists FeF _3, and to provide a positive electrode active material for a nonaqueous secondary battery showing charge-discharge characteristics FeF ₃ is stabilized be decomposed. Furthermore, it aims at providing the charging / discharging method desirable for the non-aqueous secondary battery using this positive electrode active material.

In general, “intercalation” refers to a phenomenon in which an electron donor or electron acceptor is inserted between layers of a layered substance by a charge transfer force. “Conversion” has a meaning such as substance conversion. In the above-described FeF ₃ , the region where Li is inserted into the vacancies in the structure and the region where the inserted Li is desorbed are defined as intercalation regions. A region where Li _x FeF ₃ into which Li is inserted is further decomposed into LiF and Fe and a region where Li _x FeF ₃ is regenerated from LiF and Fe are defined as a conversion region.

The positive electrode active material for a non-aqueous secondary battery of the present invention is a positive electrode active material for a non-aqueous secondary battery made of FeF ₃ powder capable of inserting and removing alkali metal ions,
The FeF ₃ powder is a fine powder in which the half-width of the diffraction peak of the (012) plane by X-ray diffraction is 0.2 rad or more, and Fe is generated from FeF ₃ by discharge, and FeF ₃ is regenerated by charging. Reversible oxidation-reduction is performed.

Further, the non-aqueous secondary battery charging / discharging method of the present invention is a non-aqueous secondary battery comprising a positive electrode containing FeF ₃ powder capable of inserting and removing alkali metal ions as a positive electrode active material.
The FeF ₃ powder is a fine powder in which the half-width of the diffraction peak of the (012) plane by X-ray diffraction is 0.2 rad or more, and Fe is generated from FeF ₃ by discharge, and FeF ₃ is regenerated by charging. Charging / discharging is performed in a voltage range in which reversible oxidation-reduction is performed.

FIG. 1 shows the crystal structure of FeF ₃ into which alkali metal ions can be inserted and removed. FeF ₃ is a perovskite type fluoride and has a cation vacancy in the structure. A maximum of 1 mol of alkali metal ions (for example, Li ⁺ ) can be inserted into 1 mol of FeF _{3 in the} cation vacancies, resulting in LiFeF ₃ . At this time, the theoretical capacity exceeds 230 mAh / g. Furthermore, LiFeF ₃ reacts with Li ions and is finally decomposed into LiF and Fe. That is, the reaction proceeds to the conversion region, and at this time, theoretically, the capacity is 700 mAh / g or more.

The inventors of the present invention have focused on the fact that the secondary battery capacity can be increased by discharging to a conversion region that has been conventionally avoided when using FeF ₃ powder as a positive electrode active material. Then, even if the reaction to conversion region, in order to charge and discharge is performed stably have found that it is necessary to use a fine FeF _3. The FeF ₃ powder in which the half-value width of the diffraction peak of the (012) plane by X-ray diffraction is 0.2 rad or more has fine FeF ₃ crystal grains. Therefore, by sweeping the discharge end voltage to a lower level than before, FeF ₃ is easily decomposed by discharge and Fe is generated. Furthermore, FeF ₃ is regenerated from Fe produced by the decomposition. That is, Fe is generated from FeF ₃ by discharge, and FeF ₃ is regenerated from Fe by charging, so that reversible oxidation-reduction is stably performed.

The crystal structure of perovskite fluoride FeF ₃ is shown. 2 is an X-ray diffraction pattern of FeF ₃ powder. 2 is an X-ray diffraction pattern of a mixed powder obtained by milling FeF ₃ powder together with acetylene black. 2 is an X-ray diffraction pattern of a mixed powder obtained by milling FeF ₃ powder together with ketjen black. The FeF ₃ powder with Ketjen black is a X-ray diffraction pattern of the mixed powder obtained by hand stirring. The charging / discharging curve when charging / discharging the non-aqueous secondary battery of this invention by 4.5V-1.5V and 0.03mA is shown. The discharge wire when a conventional non-aqueous secondary battery is charged and discharged at 4.5 V to 1.5 V and 0.03 mA is shown. The discharge curve when charging / discharging the non-aqueous secondary battery of this invention by 4.5V-2.0V and 0.03mA is shown. The discharge wire when a conventional non-aqueous secondary battery is charged and discharged at 4.5 V to 2.0 V and 0.03 mA is shown. The discharge curve when charging / discharging the non-aqueous secondary battery of this invention by 4.5V-2.0V and 0.1 mA is shown.

  Hereinafter, the best mode for carrying out the positive electrode active material for a non-aqueous secondary battery and the method for charging the non-aqueous secondary battery of the present invention will be described.

[Positive electrode active material for non-aqueous secondary batteries]
The positive electrode active material for non-aqueous secondary batteries of the present invention (hereinafter abbreviated as “positive electrode active material”) is made of FeF ₃ powder capable of inserting and removing alkali metal ions. In the FeF ₃ powder, the half width of the diffraction peak of the (012) plane by X-ray diffraction is 0.2 rad or more, preferably 0.3 rad or more, more preferably 0.4 rad or more. The full width at half maximum is measured at the intensity calculated by I _max / 2, where I _max is the maximum intensity of (012) seen at a diffraction angle (2θ, CuKα line) near 23.7 °. Value. If the half-value width of the diffraction peak is less than 0.2 rad, the FeF ₃ crystal grains are too large, and the reaction in the conversion region is not performed well. The upper limit of the half-value width is not particularly limited because the larger the value, the smaller the particle diameter, but it is preferably 1 rad or less if deliberately defined.

Also, if you define an average particle size of FeF ₃ powder, 200 nm or less, more preferably not more than 10 nm 100 nm. An average particle size of 200 nm or less is preferable because the decomposition reaction into the conversion region and the generation of FeF ₃ from the conversion region are likely to occur reversibly. This reversible reaction is more likely to occur as the average particle size is smaller. However, FeF ₃ powder having an average particle size of less than 3 μm is difficult to produce and is not readily available. The average particle diameter of the FeF ₃ powder is the maximum diameter of about 10 FeF ₃ particles (maximum value of the interval between parallel lines when the particles are sandwiched between two parallel lines) from a scanning electron microscope (SEM) photograph. Measure and take the arithmetic average of them.

FeF ₃ powder with fine crystal grains can be obtained by milling FeF ₃ of a certain size or converting the precursor by heating a solution containing the FeF ₃ precursor. It is. In the case of obtaining FeF ₃ powder by milling, the milling speed may be 200 rpm to 600 rpm, further 550 rpm to 650 rpm. This is because if it is less than 200 rpm, FeF ₃ is difficult to be miniaturized even if milling is performed for a long time. The milling time is preferably 1 to 24 hours, more preferably 5 to 24 hours. This is because if the time is less than 1 hour, the effect of miniaturization is poor, and even if milling is performed for more than 24 hours, the effect of miniaturization is not greatly improved.

  In addition, although it explains in full detail in the column of [Charging / discharging method], the positive electrode active material of this invention shows a discharge voltage characteristic between 4.5V-1.5V with respect to lithium. That is, when the discharge end voltage is less than 2.0 V, the decomposition reaction into the conversion region occurs. As a result, the discharge capacity is greatly increased.

[Configuration and production method of electrode (positive electrode)]
The positive electrode active material of the present invention can be used as a positive electrode active material for non-aqueous secondary batteries. A positive electrode is comprised including the positive electrode active material of the said invention, the conductive support material, and the binder which binds a positive electrode active material and a conductive support material.

The positive electrode active material is the above-mentioned FeF ₃ powder. In addition, after using FeF ₃ powder as the main active material, a known positive electrode active material may be added and used. Specifically, lithium cobaltate or the like. Among these, one kind or a mixture of two or more kinds can be used.

As a conductive support material, a material generally used for an electrode of a non-aqueous secondary battery may be used. For example, it is preferable to use a conductive carbon material such as carbon black, acetylene black, or carbon fiber. In addition to these carbon materials, a known conductive aid such as a conductive organic compound may be used. One of these may be used alone or in combination of two or more. The conductive aid is desirable because it is further milled together with the above-mentioned FeF ₃ powder to further improve the conductivity. The blending ratio of the conductive additive is preferably a mass ratio of positive electrode active material: conductive additive = 1: 0.05 to 1: 2. This is because if the amount of the conductive aid is too small, an efficient conductive network cannot be formed, and if the amount of the conductive aid is too large, the moldability of the electrode is deteriorated and the energy density of the electrode is lowered.

  The binder is not particularly limited, and a known one may be used. For example, a resin that does not decompose even at a high potential, such as a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride, can be used. The blending ratio of the binder is preferably a mass ratio of active material: binder = 1: 0.05 to 1: 0.5. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  The positive electrode active material of the present invention is generally used in a state in which it is pressed against a current collector as an active material layer in the positive electrode. A metal mesh or metal foil can be used for the current collector. For example, a current collector made of a metal that does not melt even at a high potential, such as aluminum or an aluminum alloy, may be used.

  There is no limitation in the manufacturing method of an electrode, What is necessary is just to follow the manufacturing method of the electrode for non-aqueous secondary batteries currently generally implemented. For example, the conductive additive and the binder are mixed with the positive electrode active material, and an appropriate amount of an organic solvent is added as necessary to obtain a paste-like electrode mixture. The electrode mixture is applied to the surface of the current collector, dried, and then pressed and pressed as necessary. According to this manufacturing method, the produced electrode becomes a sheet-like electrode. This sheet-like electrode may be cut into dimensions according to the specifications of the non-aqueous secondary battery to be produced.

[Non-aqueous secondary battery]
The non-aqueous secondary battery of this invention is equipped with the positive electrode containing the positive electrode active material of the said invention. The configuration and manufacturing method of the positive electrode are as described above. The negative electrode includes a negative electrode active material made of a material capable of inserting and removing alkali metals. The negative electrode is made of, for example, an alkali metal such as Li or Na, an alloy of an alkali metal, an ion that enters between layers such as carbon, or an alloy that forms an alloy with ions of a single conductive element such as a metal. preferable. What is necessary is just to produce a negative electrode with the general manufacturing method according to said positive electrode manufacturing method.

The non-aqueous secondary battery of the present invention includes a separator and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode in addition to the positive electrode and the negative electrode, as in the case of a general secondary battery. The separator separates the positive electrode and the negative electrode and holds the electrolytic solution, and a thin microporous film such as polyethylene or polypropylene can be used. The non-aqueous electrolyte is obtained by dissolving an alkali metal salt that is an electrolyte in an organic solvent. As the organic solvent, an aprotic organic solvent, for example, capable of withstanding a high potential difference or by forming a film or the like is used. One type of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, or the like that can withstand a potential difference, or a mixture of two or more types thereof can be used. As the electrolyte to be dissolved, existing supporting salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiI, LiClO ₄ , NaPF ₆ , NaBF ₄ , NaAsF ₆ can be used. Further, instead of the non-aqueous electrolyte, a solid electrolyte such as an inorganic compound having lithium ion conductivity and glass containing Li ₂ S and glass can also be used.

  The shape of the non-aqueous secondary battery is not particularly limited, and various shapes such as a cylindrical shape, a stacked shape, and a coin shape can be employed. Regardless of the shape, a separator is sandwiched between the positive electrode and the negative electrode to form an electrode body, and the space between the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal is used for current collection. After connecting using a lead or the like, the electrode body is sealed in a battery case together with a non-aqueous electrolyte to form a battery.

The non-aqueous secondary battery of the present invention described above performs reversible oxidation-reduction in which Fe is generated from FeF ₃ by discharging and FeF ₃ is regenerated from Fe by charging. For example, if the electrolyte ion is Li ⁺ , Li ⁺ is inserted by discharge to generate LiF and Fe from FeF ₃ through Li _y FeF ₃ (0 <y ≦ 1), and from LiF and Fe by charging. Reversible oxidation-reduction is performed by regenerating FeF ₃ via Li _y FeF ₃ (0 <y ≦ 1). The non-aqueous secondary battery of the present invention that performs such reversible oxidation-reduction is preferably a discharge capacity of 400 mAh / g or more, more preferably 500 mAh / g or more, and more preferably 700 mAh / g or more in the first charge / discharge cycle. Indicates. The charge / discharge method of the non-aqueous secondary battery of the present invention will be described below.

[Charging / discharging method]
In the non-aqueous secondary battery of the present invention, charge and discharge are performed in a voltage range in which Fe is generated from FeF ₃ by discharge and reversible oxidation-reduction is performed to regenerate FeF ₃ from Fe. As described above, the positive electrode active material of the present invention is desirably swept down to a discharge end voltage lower than before because FeF ₃ is decomposed by discharge to generate Fe. For example, in a lithium ion secondary battery including a negative electrode containing a negative electrode active material containing lithium, charging / discharging is usually performed with a voltage range of 4.5 V to 2.0 V, but lithium ion using the positive electrode active material of the present invention In the secondary battery, it is desirable that the end-of-discharge voltage is less than 2.0V, more preferably 1.0V to 1.5V. For example, it is preferable to discharge at a constant current in the voltage range between 4.5V and 1.5V.

  As mentioned above, although embodiment of the positive electrode active material for non-aqueous secondary batteries of this invention and the charging method of a non-aqueous secondary battery was described, this invention is not limited to the said embodiment. Without departing from the scope of the present invention, the present invention can be implemented in various forms with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be specifically described with reference to examples of the positive electrode active material for a non-aqueous secondary battery and the method for charging a non-aqueous secondary battery according to the present invention.

[Preparation of active material]
A commercially available FeF ₃ powder (referred to as powder # 00) was prepared. FIG. 2 shows the X-ray diffraction (XRD) analysis result (using CuKα) of powder # 00. This FeF ₃ powder was mixed with a conductive additive as follows to obtain powders # 01, 02, C1 and C2. Acetylene black (AB) and ketjen black (KB) were used as conductive aids.

  4.03 g of powder # 00 and 4.07 g of acetylene black were mixed by a ball mill to obtain powder # 01. The mixing was performed at a milling speed of 600 rpm and a milling time of 5 hours. The XRD analysis result of powder # 01 is shown in FIG. For comparison, the powder mixed at the same blending ratio was manually stirred for 1 hour to obtain # C1 powder.

  0.74 g of powder # 00 and 0.73 g of ketjen black were mixed by a ball mill to obtain powder # 02. The mixing was performed at a milling speed of 600 rpm and a milling time of 5 hours. The XRD analysis result of powder # 02 is shown in FIG. For comparison, the powder mixed at the same blending ratio was manually stirred for 1 hour to obtain # C2 powder. The XRD analysis result of powder # C2 is shown in FIG.

  Since the diffraction peaks of the powders # 01 and # 02 are broader than those of the powder # 00, it was found that the crystal grains became fine by milling. The # C2 powder that was only stirred by hand did not show a large difference from the diffraction peak of the powder # 00. Although the XRD analysis result was omitted for powder # C1, it can be estimated that the same result as that of powder # C2 was obtained. From the XRD analysis results of FIGS. 2 to 5, the half width of the (012) plane was obtained, and the particle size of each powder was estimated. The half width was calculated as the peak width (full width at half maximum) at a position half the length of the vertical line by subtracting the background from the measured data and dropping the vertical line from the peak top. The particle size was calculated using Scherrer's equation. Scherrer's equation is expressed by t = (0.9λ) / (βcos θ), where λ is the wavelength of CuKα (1.542 cm), β is the half-value width, and θ is the peak position (rad) of (012). . Table 1 shows the obtained half width and particle diameter.

Moreover, each powder was observed with the scanning electron microscope (SEM), and the average particle diameter was calculated | required from the SEM image. The average particle diameter was determined by measuring the maximum diameter of about 10 FeF ₃ particles (maximum value of the interval between parallel lines when the particles were sandwiched between two parallel lines) from the SEM image, and calculating the arithmetic average value thereof. . Table 1 shows the obtained average particle diameter.

[Production of electrodes for lithium ion secondary batteries]
An electrode (positive electrode) was prepared using the above powder # 01. A predetermined amount of a conductive binder (a mixture of AB and polytetrafluoroethylene (PTFE), abbreviated as “TAB”) is mixed with Powder # 01, and an appropriate amount of solvent (ethanol) is added and kneaded thoroughly. A paste-like electrode mixture was prepared. The compounding ratio of the positive electrode active material (FeF ₃ powder), AB, and PTFE was 42.9: 52.4: 4.9 in terms of mass ratio. Next, this electrode mixture was pressure-bonded to both surfaces of a current collector (100 mesh, manufactured by Niraco Co., Ltd., thickness: 100 μm), and a sheet-like electrode was obtained after drying.

  As a comparative example, a sheet-like electrode was produced in the same manner as described above using powder # C1 instead of powder # 01.

[Production of lithium ion secondary battery]
A lithium ion secondary battery using the electrode containing powder # 01 as the positive electrode was produced. The negative electrode facing the positive electrode was metallic lithium (thickness: 500 μm). The positive electrode was cut to φ13 mm and the negative electrode was cut to φ15 mm, and a separator (Hoechst Celanese glass filter, celgard 2400) was sandwiched between them to form an electrode body. After attaching a lead to this electrode body, it was housed and held in an aluminum battery case. In addition, a non-aqueous electrolyte in which LiPF ₆ was dissolved at a concentration of 1 M was injected into the battery case in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio of 1: 1 (volume ratio). The battery case was sealed to obtain a lithium ion secondary battery # 11 (abbreviated as “battery # 11”).

  Further, as a comparative example, a lithium ion secondary battery # 11c (abbreviated as “battery # 11c”) was produced in the same manner as described above using a positive electrode containing powder # C1.

[Evaluation]
A charge / discharge test was performed on battery # 11 to evaluate charge / discharge characteristics. In the test, after charging at a constant current of 0.03 mA to a charge end voltage of 4.5 V under a temperature environment of 30 ° C., discharge was performed at a constant current of 0.03 mA to a discharge end voltage of 1.5 V. . Charging / discharging was repeated and the capacity per unit weight of the positive electrode active material with respect to voltage was measured. The charge / discharge characteristics of the first cycle are shown in FIG. Moreover, the same charge / discharge test was done also about battery # 11c. FIG. 7 shows the discharge characteristics at the 1st to 5th cycles, the 10th cycle and the 20th cycle.

From FIG. 6, it was found that the battery # 11 exhibits a high capacity by charging and discharging at a voltage range of 4.5V to 1.5V. That is, in the battery # 11, a reaction in the conversion region, that is, decomposition and regeneration of FeF ₃ occurred reversibly by charging and discharging, and a high capacity was obtained. In addition, according to the discharge curve of FIG. 6, the inclination of the graph changed greatly with the voltage near 2.0V. This indicates that LiFeF ₃ started to be decomposed into LiF and Fe at around 2.0V.

On the other hand, also in the discharge curve of the battery # 11c shown in FIG. 7, the slope of the graph changed greatly with the voltage near 2.0V. However, the discharge capacity was small and the cycle characteristics were low. This is presumably because the milling was not performed and the FeF ₃ powder was not sufficiently refined and the reaction in the conversion region was difficult to occur reversibly.

  Next, the battery # 11 was charged with a constant current of 0.03 mA to a charge end voltage of 4.5 V under a temperature environment of 30 ° C., and then 0.03 mA to a discharge end voltage of 2.0 V. Discharge was performed at a constant current. Charging / discharging was repeated and the capacity per unit weight of the positive electrode active material with respect to voltage was measured. FIG. 8 shows the discharge characteristics at the 1st to 5th cycles, the 10th cycle and the 20th cycle. Moreover, the same charge / discharge test was done also about battery # 11c. FIG. 9 shows the discharge characteristics at the 1st to 5th cycles, the 10th cycle and the 20th cycle.

  Even when the batteries # 11 and # 11c were charged / discharged in the voltage range of 4.5V to 2.0V, the discharge capacity was low compared to the case where the batteries were charged / discharged in the range of 4.5V to 1.5V. Battery # 11 used the milled powder to improve the cycle characteristics over battery # 11c. However, in all cases, the reaction in the conversion area did not occur, so the capacity remained low.

  Further, the battery # 11 was charged at a constant current of 0.1 mA to a charge end voltage of 4.5 V under a temperature environment of 30 ° C., and then the constant of 0.1 mA to a discharge end voltage of 2.0 V was charged. Discharge was performed with current. Charging / discharging was repeated and the capacity per unit weight of the positive electrode active material with respect to voltage was measured. FIG. 10 shows the discharge characteristics at the 1st to 5th cycles, the 10th cycle and the 20th cycle.

  Even when the current value was 0.1 mA and the charge / discharge speed of the battery # 11 was increased, a reversible reaction in the conversion region was satisfactorily performed, and a high capacity could be stably obtained.

Claims (11)

A positive electrode active material for a non-aqueous secondary battery made of FeF ₃ powder capable of inserting and removing alkali metal ions,
The FeF ₃ powder is a fine powder in which the half-width of the diffraction peak of the (012) plane by X-ray diffraction is 0.2 rad or more, and Fe is generated from FeF ₃ by discharge, and FeF ₃ is regenerated by charging. A positive electrode active material for a non-aqueous secondary battery, characterized by performing reversible oxidation-reduction.   The positive electrode active material for nonaqueous secondary batteries according to claim 1, wherein the positive electrode active material exhibits discharge voltage characteristics between 4.5 V and 1.5 V with respect to lithium. The positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein the FeF ₃ powder has an average particle size of 100 nm or less. The positive electrode active material for a non-aqueous secondary battery according to claim 3, wherein the FeF ₃ powder has an average particle size of 10 nm or less. The positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein the FeF ₃ powder is formed by milling.   The positive electrode active material for a non-aqueous secondary battery according to claim 5, wherein the milling speed is 200 to 600 rpm, and the milling time is 1 to 24 hours.   A non-aqueous secondary battery comprising a positive electrode comprising the positive electrode active material for a non-aqueous secondary battery according to claim 1.   The non-aqueous secondary battery according to claim 7, comprising a negative electrode containing a negative electrode active material containing lithium and having a discharge end voltage of less than 2.0V. In a non-aqueous secondary battery comprising a positive electrode containing FeF ₃ powder capable of inserting and removing alkali metal ions as a positive electrode active material,
The FeF ₃ powder is a fine powder in which the half-width of the diffraction peak of the (012) plane by X-ray diffraction is 0.2 rad or more, and Fe is generated from FeF ₃ by discharge, and FeF ₃ is regenerated by charging. A charge / discharge method for a non-aqueous secondary battery, wherein charge / discharge is performed in a voltage range in which reversible oxidation-reduction is performed.   The charging / discharging method of the non-aqueous secondary battery according to claim 9, comprising a negative electrode containing a negative electrode active material containing lithium and having a final discharge voltage of less than 2.0V.   The charging / discharging method of the non-aqueous secondary battery according to claim 10, wherein the voltage range is 4.5V to 1.5V.

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