KR101810259B1 - Method for producing lithium manganese iron phosphate particulate powder, lithium manganese iron phosphate particulate powder and non-aqueous electrolyte secondary battery using that particulate powder - Google Patents

Abstract

The present invention relates to a method for producing an olivine-type structure of lithium iron phosphate LiMn _{1 - x} Fe _x PO ₄ (0.05 ≦ _x ≦ 0.5) powder, which comprises a first step of obtaining an aqueous slurry by neutralization reaction of a mixed solution of raw materials And the slurry obtained in the first step is subjected to a hydrothermal treatment so that the yield of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) of the obtained compound is 75 wt% or more and the crystallite size is 10 to 250 nm A third step of adding an organic compound to the compound obtained in the second step to obtain a precursor powder having a carbon content of 3 to 40% by weight, and a fourth step of calcining the precursor powder obtained in the third step The process comprising the steps of: It is possible to provide a secondary battery using a manufacturing method of a lithium manganese iron lithium particle powder which can be easily manufactured at a low cost and has a large charge / discharge capacity as a secondary battery and excellent in chargeability and repetitive charging / discharging characteristics.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for producing a lithium manganese iron lithium particle powder, a lithium manganese iron lithium particle powder, and a non-aqueous electrolyte secondary battery using the particle powder. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] BATTERY USING THAT PARTICULATE POWDER}

The present invention relates to a process for producing lithium manganese iron lithium particle powder having an olivine structure which can be easily manufactured at low cost and also has an olivine-type structure of lithium iron phosphate lithium particles having a high energy density when used as a high output secondary battery, And a secondary battery using the same is provided.

2. Description of the Related Art Recently, power tools such as AV devices, personal computers and other electronic devices and power tools have been rapidly made portable and wireless, and there is a demand for a secondary battery that is small, lightweight and has a high energy density as a driving power source thereof. It is getting higher. In addition, from the consideration of the global environment, development and commercialization of hybrid vehicles and electric vehicles have been made, and the demand for secondary batteries having excellent output characteristics is increasing. Under such circumstances, a lithium ion secondary battery having the advantage of high charge / discharge capacity and high safety has been attracting attention.

Recently, as a positive electrode active material useful in a lithium ion secondary battery of high energy density type, a copper-based LiMnPO ₄ of 4.1 V class is also attracting attention from olivine type LiFePO _{4 of} 3.5 V class structure. However, since LiMnPO ₄ is more difficult to enter and exit than LiFePO ₄ , it is required to improve the charge-discharge characteristics.

In other words, LiMnPO ₄ of the olivine structure is composed of a strong tetrahedral phosphate structure and an octahedron of oxygen centered on manganese ion which contributes to redox and lithium ion, which is a current collector. In addition, there is a tendency to coat carbon on the particle surface to compensate for the electronic conductivity. It is believed that the two-phase reaction of the following reaction formula results from the presence of the plateau region in the charge-discharge characteristics, which is represented by the capacity and the voltage at the time of charging and discharging with Li as the negative electrode, as an electrode of the secondary battery.

Charge: LiMnPO ₄ ? MnPO ₄ + Li ⁺ + e ^-

Discharge: MnPO ₄ + Li ⁺ + e ^- → LiMnPO ₄

However, there are various theories about the easiness of Li out of LiMnPO ₄ positive electrode and the stability of MnPO ₄ in which Li is eliminated. For this reason, it is thought that it is necessary to reduce the change in the particle size before and after charging / discharging while the crystal structure of the Li-eliminated material by the charging reaction is stable. As one of them, there is a method in which Fe is dissolved in the Mn moiety (Non-Patent Documents 1 to 6).

The more the LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) is coated with carbon on the surface of the particles, the better the charge / discharge characteristics at low current. Further, particles having a smaller crystallite size while satisfying the above conditions tend to have better charge / discharge characteristics at a high current load. Further, in order to obtain a high molded body density as an electrode, it is necessary to control the respective aggregate states so as to form a network with a conductive auxiliary agent such as carbon having a high degree of graphitization as well as appropriately agglomerated secondary particles. On the other hand, the positive electrode complexed with a large amount of carbon is bulky and has a defect that the substantial lithium ion density which can be charged per unit volume is low. Therefore, in order to secure the charge / discharge capacity per unit volume, it is required to obtain olivine-type lithium iron phosphate of manganese phosphate coated with carbon finely and appropriately and to form an aggregate having high density through a small amount of conductive auxiliary agent .

That is, as the positive electrode active material powder for a nonaqueous electrolyte secondary battery, lithium iron phosphate powder having an olivine structure having a small change in particle size due to charging and discharging, a small electric resistance, It is required to produce by the method.

Conventionally, various improvements have been made to improve various characteristics of olivine-type lithium manganese iron lithium particle powder. For example, a technique of reducing deterioration after a charge-discharge cycle test (Patent Document 1), a technique of reducing electrical resistance by adding a dissimilar metal element (Patent Document 2), a technique of reducing the electrical resistance by adding a dissimilar metal element and carbon coating (Patent Document 3), and a technique of synthesizing by the hydrothermal method (Patent Documents 4 to 6).

Japanese Patent Application Laid-Open No. 2003-257429 Japanese Patent Laid-Open No. 2004-063270 Japanese Patent Publication No. 2008-130525 Japanese Patent Application Laid-Open No. 2007-035358 Japanese Patent Laid-Open No. 2007-119304 Japanese Patent Application Laid-Open No. 2008-066019

 A. K. Padhi et al., J. Electrochem. Soc., 1997, Vol. 144, p.  A. Yamada et al., J. Electrochem. Soc., 2001, Vol.148, p.A960-967.  G. Li et al., J. Electrochem. Soc., 2002, Vol.149, p.A743-747.  C. Delacourt et al., J. Electrochem. Soc., 2005, Vol. 152, p. 913-921.  N. -H. -Kwon et al., Electrochem. and Solid-State Let., 2006, Vol.9, A277-280.  S. K. Martha et al., J. Electrochem. Soc., 2009, Vol.156, p.A541-552.

At present, it is the most demanded for a low-cost and efficient production method of an olivine-type lithium manganese iron lithium particle powder satisfying the above-mentioned various properties as a positive electrode active material for a nonaqueous electrolyte secondary battery, but it has not yet been established.

That is, the techniques described in the above Non-Patent Documents 1 to 6 can be applied to LiMn _{1- x} Fe _x PO ₄ (0.05? X Lt; = 0.5) can not be industrially obtained.

Further, the technique described in Patent Document 1 is a technique for improving charge / discharge repetition characteristics when an olivine-type LiMn _{1 - x} Fe _x PO ₄ particle powder is used as a positive electrode, Controls are not mentioned.

Further, the technique described in Patent Document 2 is not a technique related to the composite of LiMnPO ₄ particle powder of olivine structure and carbon.

Further, the technique described in Patent Document 3 is a manufacturing method using a solid-phase reaction method, and since it has two heat treatments, it is difficult to say that it is low cost.

The hydrothermal method described in Patent Documents 4 to 6 is a method in which 1) lithium hydroxide is excessively introduced to neutralize phosphoric acid or sulfate as a raw material, 2) a precipitate is produced from phosphoric acid as a raw material or a sulfate containing a transition metal, And a method of mixing Li: Mn + Fe: P = 1: 1: 1 molar ratio by mixing with the raw material. 1), recovery of Li is required from the viewpoint of manufacturing cost, but it is considered to be a relatively difficult technique. 2), there is almost no report of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5), and there is almost no mention of a precursor for hydrothermal treatment, and no technique relating to control of the aggregate particle diameter has been found .

Accordingly, it is an object of the present invention to establish an industrial technique of lithium manganese iron lithium particle powder having an olivine structure with a small change in particle size due to charge and discharge, a small electric resistance and a high filling ability, A nonaqueous electrolyte secondary battery containing an active material, which has a technical problem of obtaining a high capacity in terms of current load characteristics.

The above technical object can be achieved by the following invention.

That is, the present invention relates to a method for producing an olivine-type structure of lithium iron phosphate LiMn _{1 - x} Fe _x PO ₄ (0.05 ≦ _x ≦ 0.5) powder, which comprises a Li compound, a Mn compound, an Fe compound, Or an organic acid is used and the raw material charging ratio is in the range of 0.95? Li / (Mn + Fe)? 2.0, 0.95? P / (Mn + Fe)? 1.3 and 1 to 20 mole% Or an organic acid to obtain an aqueous slurry having a pH of 5.5 to 12.5; and a step of subjecting the slurry obtained in the first step to hydrothermal treatment at a reaction temperature of 120 to 220 占 폚 to obtain LiMn _{1 - x} Fe _x PO ₄ (0.05? _x ? 0.5) of not less than 75% by weight and a crystallite size of 10 to 250 nm and then cleaning the compound; To 3% by weight to 40% by weight of the precursor powder to obtain a precursor powder; Under the oxygen concentration of the inert gas or a reducing gas atmosphere at not more than 0.1%, a fourth step olivine-type method for producing a lithium iron manganese phosphate powder particles of the structure that contains the firing at a temperature of 250 to 850 ℃ (invention 1).

The present invention, in the first step, the median diameter of the aggregated particles in the slurry is from 0.1 to 10 μm, the crystalline _{(NH 4) Mn 1 -α Fe} α PO 4 (0≤α <1) or HMn _{1 -β} Fe _β PO ₄ (0 ≦ _β <1) (Inventive Invention 2).

Further, the present invention is the production method according to the first or second aspect of the present invention, wherein the sugar or organic acid used in the first step is at least one of sucrose, ascorbic acid, and citric acid (invention 3).

Further, the present invention is the method according to any one of the first to third aspects of the present invention for cleaning so that the sulfur content in the compound is 0.1 wt% or less in the second step (Invention 4).

Further, the present invention is the production method according to any one of the inventions 1 to 4, wherein the organic substance to be added in the third step is at least one of carbon black, a fat compound, a sugar compound, and a synthetic resin (invention 5) .

The present invention also provides a lithium iron phosphate lithium manganese iron LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) particle powder having an olivine structure, wherein the molar ratio of lithium to phosphorus is 0.9? Li / (Mn + Fe)? 1.2 , 0.9? P / (Mn + Fe)? 1.2, a BET specific surface area of 6 to 70 m ² / g, a carbon content of 0.5 to 8 wt% and a sulfur content of 0.08 wt% Wherein the amount of the crystalline phase LiMn _{1- x} Fe _x PO ₄ (0.05? _X ? 0.5) is 95 wt% or more, the crystallite size is 25 to 300 nm, the median diameter of the aggregated particles is 0.3 to 20 μm, 1 to 1.0 x 10 ⁶ ? 占 cm m.

Further, the present invention is a lithium manganese iron phosphate powder having an olivine structure according to the sixth aspect of the invention, wherein the content of lithium and phosphorus satisfies Li? P (invention 7).

Further, the present invention is a lithium manganese iron phosphate powder having an olivine structure according to the sixth or seventh aspect of the present invention in which the unit cell volume V _{UC satisfies} the following formula (I).

Further, the present invention is a nonaqueous electrolyte secondary battery produced by using the olivine-type lithium manganese iron lithium particle powder according to any one of the inventions 6 to 8 (invention 9).

The method for producing lithium manganese iron lithium phosphate particles having an olivine structure according to the present invention is preferable as a method for producing lithium manganese iron lithium phosphate particles having an olivine structure because it can be efficiently produced from almost the same amount of raw materials at low cost.

Further, the olivine-type lithium manganese iron phosphate powder of olivine structure according to the present invention is preferable as a positive electrode active material for a non-aqueous electrolyte secondary battery because of small change in particle size due to charging and discharging, small electric resistance and high packing property .

Further, the secondary battery using the olivine-type lithium iron phosphate manganese iron particle powder according to the present invention as a positive electrode active material has a high capacity in terms of current load characteristics and can withstand repeated charging and discharging sufficiently.

Fig. 1 is a secondary electron image of a lithium manganese iron lithium particle powder of olivine structure obtained in Example 1 by a scanning electron microscope. Fig.
Fig. 2 is a discharge characteristic obtained by positive electrode lithium manganese iron phosphate powder having an olivine structure obtained in Example 1 and evaluated with a coin cell. Fig.
Fig. 3 is a secondary electron image obtained by a scanning electron microscope of the olivine-type lithium manganese phosphate powder obtained in Comparative Example 4. Fig.
4 is a scanning electron microscope secondary electron image of a particle powder obtained by chemical oxidation of an olivine-type lithium manganese phosphate particle powder obtained in Comparative Example 4. Fig.
5 is a Rietveld analysis result of an X-ray diffraction pattern of a particle powder obtained by chemical oxidation of an olivine-type lithium manganese phosphate particle powder obtained in Comparative Example 4. Fig.

The construction of the present invention will be described in more detail as follows.

First, a process for producing olivine-type lithium iron phosphate manganese phosphate according to the present invention will be described.

The process for producing an olivine-type iron oxide lithium iron phosphate LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) particle powder according to the present invention is characterized in that a Li compound, a Mn compound, an Fe compound, a P compound, And the raw material charging ratio is 0.95? Li / (Mn + Fe)? 2.0, 0.95? P / (Mn + Fe)? 1.3 and the amount of the sugar or organic acid To obtain an aqueous slurry having a pH of 5.5 to 12.5 by a neutralization reaction of a mixed solution containing LiMn _{1 - x} of the obtained compound, and a step of hydrothermally treating the slurry obtained in the first step at a reaction temperature of 120 to 220 ° C, A second step of cleaning the compound after crystallization of Fe _x PO ₄ (0.05? _X ? 0.5) of 75 wt% or more and a crystallite size of 10 to 250 nm; By weight to 40% by weight to obtain a precursor powder, a precursor powder obtained in the third step At a temperature of 250 to 850 占 폚 in an atmosphere of an inert gas having an oxygen concentration of 0.1% or less or a reducing gas atmosphere.

The raw materials used in the first step are preferably LiOH and Li ₃ PO _{4 as} Li compounds, MnSO ₄ and MnCO ₃ are preferable as Mn compounds, FeSO ₄ and FeCO ₃ are preferable as Fe compounds, and H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NaH ₂ PO ₄ , Na ₂ HPO ₄ and Na ₃ PO ₄ are preferable.

The Li compound, the Mn compound, the Fe compound and the P compound in the first step are mixed so that the raw material charge ratio is 0.95? Li / (Mn + Fe)? 2.0 and 0.95? P / (Mn + Fe)? When the feed ratio of the raw material is outside the above range, desired lithium iron phosphate manganese phosphate can not be obtained. More preferably, the molar ratio is 0.98? Li / (Mn + Fe)? 1.8 and 0.98? P / (Mn + Fe)? 1.2.

In addition, the sugar or organic acid used in the first step is preferably sucrose, ascorbic acid, or citric acid. The amount of the saccharide or organic acid to be added is 1 to 20 mol%, more preferably 1.5 to 18 mol% based on (Mn + Fe), and the added saccharide or organic acid functions as a transition metal reducing agent to form LiMn _{1 - x} The primary particle diameter of the product is made finer while the production rate of Fe _x PO ₄ (0.05? _X ? 0.5) is increased.

Alkali source to be used in the first step is such as LiOH, NaOH, Na ₂ CO _3, NH _3, urea, ethanol amine is used.

The aqueous slurry in the first step needs to have a pH of 5.5 to 12.5 in order to increase the production rate of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) of the compound obtained by hydrothermal treatment in the second step.

The median diameter of the aggregated particles in the slurry in the first step is preferably 0.1 to 10 mu m.

The slurry in the first step is a slurry in which the crystal phase of the aggregated particles in the slurry is (NH ₄ ) Mn _{1 -α} Fe _α PO ₄ (0 ≦ _α <1) or HMn _{1 -β} Fe _β PO ₄ (0 ≦ _β <1) It is preferable to include aggregated particles. When any one of the above two phases is not included, desired lithium iron phosphate manganese phosphate can not be obtained.

The agglomerated particles having the median diameter and the crystal phase can be obtained by raw material mixing (generation of a plurality of crystal nuclei) or crushing of the product under the condition that crystal nuclei are generated and grown. Examples of apparatuses used for milling include a ball mill and a medium agitated mill.

The hydrothermal treatment in the second step is preferably performed at 120 to 220 캜. In addition, the duration of the hydrothermal treatment is preferably 1 to 10 hours.

The compound obtained by hydrothermal treatment in the second step has a formation rate of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) of 75 wt% or more. If the production rate is less than 75 wt%, the production rate of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) is low even if the subsequent steps are carried out. A more preferable production rate is 80% by weight or more. The crystallite size of the obtained compound based on LiMn _{1 -x} Fe _x PO ₄ (0.05? _X ? 0.5) is 10 to 250 nm. A compound having a crystallite size of less than 10 nm is industrially difficult to produce, and when the crystallite size exceeds 250 nm, good cell characteristics can not be obtained. A more preferred crystallite size is 30 to 150 nm. The hydrothermal treatment in the second step needs to be performed by appropriately selecting the treatment temperature and the treatment time so as to satisfy the generation rate and the crystallite size. If the treatment temperature is low and the treatment time is short, the generation rate may not be reached or the crystallite size may not be reached. In the case where the treatment temperature of the hydrothermal treatment is high and the treatment time is long, .

The compound obtained by the hydrothermal treatment in the second step is subjected to filtration washing or inclined washing in order to remove the impurity sulfate ion and control the composition ratio. As a device used for washing, a press filter and a filter shaker can be given.

The cleaning of the compound obtained by hydrothermal treatment in the second step is preferably carried out so that the sulfur content in the compound is 0.1 wt% or less. Washing is sufficient as long as sulfur in the compound can be sufficiently removed, and usually, washing with water may be performed.

In order to form the lithium manganese iron-phosphate solid solution, it is preferable to adjust the main component element ratio in the third step. (Mn + Fe): P = 0.90: 1: 0.90 to 1.20: 1: 1.20, where Li, Mn, Fe and P compounds were added to the compound obtained in the second step, (Molar ratio).

Adjustment of the composition ratio of the main component elements, the lithium compound such as LiOH, Li ₂ CO ₃ to adjust the Li, a manganese compound such as MnCO _3, MnC ₂ O ₄ to the adjustment of _{Mn, FeCO 3, FeC 2 O} 4 , such as the adjustment of the Fe It is preferable to use PO ₄ -containing compounds such as H ₃ PO ₄ , (NH ₄ ) H ₂ PO ₄ and (NH ₄ ) ₂ HPO _{4 for} the adjustment of the iron compound and P.

Further, in order to form a fine lithium iron phosphate solid solution coated with carbon, 3 to 40% by weight of organic matter is added in the third step to prepare a precursor powder. At this time, it is necessary to make the primary particle diameter of the precursor powder small and uniformly mix with the organic material. Examples of a device used for mixing include a Henschel mixer, a mill, a high-speed mixer, and a medium agitated mill.

The organic material to be added is preferably at least one of carbon black, a sustaining compound, a sugar compound, and a synthetic resin.

At least one of the organic compound added to control the surface of the fine lithium phosphate manganese iron lithium powder and to control the diameter of the aggregated particles is preferably at least one of the organic compound, the sugar compound, and the synthetic resin.

In addition, when carbon black having high conductivity is used as the organic material to be added, firing at low temperature is possible in the fourth step. By using carbon black, a compacted body of an olivine-type lithium manganese iron phosphate powder obtained by low-temperature firing such as 400 to 500 DEG C satisfies an electrical resistivity of 1 to 1.0 x 10 &lt; ⁶ &gt; High secondary battery characteristics.

Examples of the sustaining compound include stearic acid, oleic acid, sucrose, and dextrin as sugar compounds, and polyethylene, polypropylene, and polyvinyl alcohol (PVA) as synthetic resins.

Examples of the carbon black include acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) and Ketjenblack (manufactured by Lion Corporation).

It is also preferable to adjust the agglomerated particle diameter of the precursor powder to 0.3 to 30 mu m by binding the particles to each other with the organic material added in the third step. Preferable binders include polyvinyl alcohol (PVA), polyvinyl butyral, starch, carboxymethyl cellulose and the like.

The precursor powder obtained in the third step is fired at a temperature of 250 to 850 캜 in an atmosphere of an inert gas having an oxygen concentration of 0.1% or less or a reducing gas atmosphere. As the inert gas, N ₂ , Ar, H ₂ O, CO ₂ or a mixed gas thereof is used. As the reducing gas, H ₂ or CO, or a mixed gas of these gases and the inert gas is used. As a device used for firing, a gas flow type box-shaped muffle, a gas flow type rotary furnace, a flow heat treatment furnace and the like can be given.

The Fe ^{3 +} contained in the Fe raw material is changed to Fe ^{2 +} by the added organic matter or the reducing gas, and LiMn _1-x Fe _x PO ₄ (0.05 ? X? 0.5) is generated. In order to produce LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5), the calcination temperature may be 250 ° C or higher. However, in order to form a graphite with high electron conductivity from the added organic material while completing the reaction of the unreacted material, Is calcined at 350 to 850 deg. C, more preferably at 400 to 750 deg. C for 1 to 10 hours.

The lithium manganese iron phosphate powder according to the present invention can increase the production rate of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) after hydrothermal treatment by adjusting an appropriate precursor slurry. Thereafter, the mixture is homogeneously mixed with the organic material and further calcined to obtain a fine lithium manganese iron phosphate powder having a high production rate of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) and sufficiently coated with carbon.

Next, a description will be given of a lithium manganese iron lithium LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) particle powder having an olivine structure for a nonaqueous electrolyte secondary battery according to the present invention. The lithium manganese phosphate lithium particle powder according to the present invention is preferably produced by the production method according to the first aspect of the present invention.

In the lithium manganese iron phosphate powder according to the present invention, the content of lithium and phosphorus is 0.9? Li / (Mn + Fe)? 1.2 and 0.9? P / (Mn + Fe)? 1.2. When the content of lithium and phosphorus is outside the above range, it is easy to form a different phase, and in some cases, the grain growth is promoted, so that a lithium manganese iron phosphate powder having high battery characteristics can not be obtained. Preferably, the content of lithium and phosphorus is in the range of 0.98? Li / (Mn + Fe)? 1.05, 0.98? P / (Mn + Fe)? 1.05, more preferably 1? Li / ? P / (Mn + Fe)? 1.05.

In the lithium manganese iron phosphate powder according to the present invention, the content of lithium and phosphorus is preferably Li? P.

The BET specific surface area of the lithium iron phosphate phosphor particles according to the present invention is 6 to 70 m ² / g. When the BET specific surface area is less than 6 m &lt; ² &gt; / g, the movement of Li ions in the lithium manganese iron lithium particle powder is slow, and it is difficult to extract the current. When it exceeds 70 m ² / g, the filling density of the positive electrode is lowered and the reactivity with the electrolyte increases, which is not preferable. The preferred BET specific surface area is from 10 to 65 m ² / g, more preferably from 15 to 60 m ² / g.

The carbon content of the lithium manganese iron lithium particle powder according to the present invention is 0.5 to 8.0 wt%. When the carbon content is less than 0.5% by weight, the grain growth during heat treatment can not be suppressed, and the electrical resistance of the obtained powder is increased, thereby deteriorating the charge / discharge characteristics of the secondary battery. When the carbon content exceeds 8.0 wt%, the filling density of the positive electrode is lowered, and the energy density per volume of the secondary battery is reduced. A more preferable carbon content is 1.0 to 6.0 wt%.

In the lithium manganese iron phosphate powder according to the present invention, the sulfur content of the impurity is 0.08 wt% or less, and good storage characteristics are obtained in the non-aqueous electrolyte secondary battery. When the sulfur content exceeds 0.08% by weight, impurities such as lithium sulfate are formed, and these impurities undergo decomposition reaction during charging and discharging, thereby accelerating the reaction with the electrolytic solution at the time of high temperature preservation, thereby increasing resistance after storage. A more preferable sulfur content is 500 ppm or less.

The lithium manganese iron phosphate powder according to the present invention contains 95 wt% or more of a crystalline phase of olivine-type structure LiMn _{1 -x} Fe _x PO ₄ (0.05? _X ? 0.5). If the impurity crystal phase as a Li ₃ PO ₄ is detected, LiMn ₁ obtained after firing _- the _x Fe _x PO ₄ (0.05≤x≤0.5) becomes fine particles, sometimes even higher, but the discharge capacity, Li ₃ PO ₄ was charged and their Since it does not contribute to the discharge, it is preferably less than 5% by weight.

The crystallite size of the lithium manganese iron lithium powder according to the present invention is 25 to 300 nm. It is very difficult to mass-produce powders having a crystallite size of less than 25 nm while satisfying other powder characteristics, and when the crystallite size exceeds 300 nm, it takes time for Li to migrate in the grain, The current load characteristic of the battery deteriorates. The preferred crystallite size is 30 nm to 200 nm, more preferably 40 nm to 150 nm.

The median diameter of the agglomerated particles of lithium manganese iron lithium particle powder according to the present invention is 0.3 to 30 탆. When the median diameter is less than 0.3 탆, the density of the positive electrode filling density is low and the reactivity with the electrolyte increases, which is not preferable. On the other hand, if the median diameter exceeds 30 占 퐉, it is too large in comparison with the electrode film thickness, and it is very difficult to form a sheet. The preferred median diameter of the aggregated particles is 0.5 to 15 占 퐉.

The density of the lithium manganese iron lithium particle powder according to the present invention is preferably 1.8 g / cc or more. The true density of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) is 3.6 g / cc, and the closer to the true density the better the chargeability. For this reason, the preferred compression molded product density is 2.0 g / cc or more, which is more than 50% of the true density. On the other hand, it is very difficult to mass produce a powder having a density of the compression molded product of 2.8 g / cc or more while satisfying other powder characteristics by the production method of the present invention. The lithium manganese iron phosphate powder according to the present invention is believed to have a high density of the compression molded product because the amount of carbon remaining is small and the primary particles are appropriately aggregated with each other.

The powder electrical resistivity of lithium manganese iron lithium particle powder according to the present invention is 1 to 1.0 x 10 &lt; ⁶ &gt; It was possible to lower the powder electrical resistivity by combining carbon with lithium iron phosphate manganese powder having an electrical resistivity of 1.0 × 10 ⁸ Ω · cm or less. The preferred powder electrical resistivity is 1 to 5.0 x 10 &lt; ⁵ &gt; [Omega] -cm, more preferably 5 to 1.0 x 10 &lt; ⁵ &gt;

The unit cell volume V _UC of the lithium manganese iron lithium particle powder according to the present invention is preferably in the relationship of the formula (1).

&Quot; (1) &quot;

It is well known that the lattice constant and the unit cell volume decrease linearly with the increase of the x value of LiMn _{1 - x} Fe _x PO ₄ of the olivine structure in general, according to Begard's law. The unit cell volume of olivine structure LiMn _{1 - x} Fe _x PO ₄ (0.05 ≤ x ≤ 0.5), which is assumed from the linearity of Begard 's law, was 10.9 × (1 - x) +291.36. When the unit cell volume is closer to the unit cell volume, the transition metal substitution to the Li site and the deficiency of P and O are reduced. When the unit cell volume is smaller than the unit cell volume, Li is substituted for the site of the transition metal, .

According to the heat treatment of the precursor having a composition ratio deviated from the stoichiometric ratio of LiMn _{1 - x} Fe _x PO ₄ of the olivine structure, LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) It was confirmed that an impurity crystal phase which exists more stably tends to be generated. In addition, even if the compositional ratio of Li, Mn, Fe and P is insignificant and LiMn _{1 -x} Fe _x PO ₄ single crystal phase of the olivine structure is generated, it has a different lattice constant, There was also a case where the volume was shown. In this case, it is presumed that the transition metal substitution to the Li site and the P and O deficiency occur and the battery characteristics are degraded.

Next, a non-aqueous electrolyte secondary battery using an olivine-type lithium manganese phosphate lithium particle powder according to the present invention as a positive electrode active material will be described.

In the case of producing the positive electrode sheet using the lithium manganese iron phosphate powder according to the present invention as the positive electrode active material, a conductive agent and a binder are added and mixed according to a conventional method. As the conductive agent, acetylene black, carbon black, graphite and the like are preferable, and as the binder, polytetrafluoroethylene, polyvinylidene fluoride and the like are preferable. As the solvent, for example, N-methyl-pyrrolidone is used, and the slurry containing the positive electrode active material sieved to 45 to 105 μm or less and the additive is kneaded until a honey form is obtained. The obtained slurry is coated on the current collector with a doctor blade having a groove of 25 mu m to 500 mu m. The coating speed is about 60 cm / sec, and an aluminum foil, usually about 20 μm, is used as a current collector. For solvent removal and binder softening, drying is carried out in a non-oxidizing atmosphere of Fe ^{2 +} at 80 to 180 ° C. The calender roll treatment is performed so that the sheet is subjected to a pressure of 1 to 3 t / cm &lt; ² &gt;. Since the oxidation reaction of Fe ^{2 +} to Fe ^{3 +} takes place at room temperature in the step of sheetification, it is preferable to carry out the oxidation treatment in the non-oxidizing atmosphere at the maximum.

Since the density of the positive electrode active material in the present invention is as high as 1.8 g / cc or more and the electrical resistivity of the positive electrode active material is as low as 1 to 1.0 x 10 &lt; ⁶ &gt; The addition amount of the binder can be suppressed since the BET specific surface area of the positive electrode active material is as low as 6 to 70 m ² / g, resulting in a high-density positive electrode sheet .

As the negative electrode active material, a lithium metal, a lithium / aluminum alloy, a lithium / tin alloy, graphite and the like can be used, and a negative electrode sheet is produced by doctor blade method or metal rolling similar to that of the positive electrode.

In addition to the combination of ethylene carbonate and diethyl carbonate, an organic solvent containing at least one of carbonates such as propylene carbonate and dimethyl carbonate and ethers such as dimethoxyethane may be used as the solvent of the electrolyte solution.

As the electrolyte, at least one kind of lithium salt such as lithium perchlorate and lithium tetrafluoroborate, in addition to lithium hexafluorophosphate, may be used by dissolving in the solvent.

<Action>

The olivine-type iron oxide lithium iron phosphate LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) particle powder according to the present invention is produced by hydrothermal reaction and calcination, and can be produced at low cost and with a small environmental load.

That is, the present invention provides a process for producing olivine type LiMn _{1 - x} Fe _x PO ₄ (0.05 ≦ _x ≦ 0.5), wherein LiMn _{1 - x} Fe _x PO ₄ (0.05 ≦ _x ≦ 0.5) The particles are uniformly mixed with the organic material to control the diameter of the aggregated particles and fired under an inert or reducing atmosphere to obtain a fine powdery carbon powder coated with carbon.

Further, since the lithium manganese iron lithium phosphate powder produced by the production method of the present invention controls the carbon coating and the diameter of the agglomerated particles, the nonaqueous electrolyte secondary battery using the same as the positive electrode active material has a high capacity The inventors of the present invention estimate that it can withstand repeated charge and discharge.

The non-aqueous electrolyte secondary battery using the olivine-type lithium iron phosphate lithium particle powder according to the present invention as the positive electrode active material has a discharge capacity at C / 10 at room temperature (25 ° C) of 115 mAh / g or more, The discharge capacity at 1C shows 95 mAh / g or more, and the discharge capacity at 5C at room temperature shows 80 mAh / g or more.

<Examples>

A representative embodiment of the present invention is as follows.

The Li and P concentrations of lithium and phosphorus-containing main raw materials were measured by neutralization titration using a pH system, hydrochloric acid, or NaOH reagent. The Fe concentration of the iron raw material was quantified by titration (JIS K5109) and the Mn concentration of the manganese raw material by titration (Analytical Chemistry Manual, Japan Analytical Chemistry Society). Based on the results of these analyzes, the reaction concentration and feedstock input ratio were determined.

The particle diameter of the agglomerated particles in the slurry in the first step was measured by a wet method using a laser diffraction / scattering type particle size distribution system HELOS (manufactured by Nippon Laser Co., Ltd.), and the median diameter D ₅₀ was measured.

The crystalline phase of the agglomerated particles in the slurry in the first step was obtained by filtering the aggregated particles in the slurry and then subjecting the wet cake to Cu-Kα, 40 (trade name, manufactured by Rigaku Corporation) using an X-ray diffraction apparatus RINT- kV, 300 mA, and the crystal phase was identified.

The crystal phase and crystallite size of the lithium iron phosphate particle powder and the production rate of LiMn _{1 - x} Fe _x PO ₄ (0.05? X? 0.5) in the compound obtained in the hydrothermal treatment in the second step and the lithium iron phosphate particle powder in the present invention were measured by X- Ray diffraction pattern measured by using 2500 (manufactured by Rigaku Corporation). The X-ray diffraction pattern was measured at a step of 0.02 占 such that the number of counts of the highest peak intensity was 8000 to 15000 at a range of 15 占 to 90 占 with 2? At 1.0 占 min. RIETAN2000 was used for the Rietveld analysis program. Assuming that there is no anisotropic expansion of the determiner, the TCH pseudo void function is used as the profile function, and the reliability factor S is reduced to less than 2.0 by using a finger method or the like in the asymmetry of the function Respectively.

<References> F. Izumi and T. Ikeda, Mater). Sci. Forum, 2000, Vol.198, p.321-324.

The unit cell volume of the lithium manganese iron lithium particle powder of the olivine structure (space group Pnma) according to the present invention was calculated from the product of the lattice constants a, b, and c calculated by the Rietveld analysis.

In the third step, the composition ratio of the compound powder obtained by adjusting the composition ratio of the compound obtained in the hydrothermal treatment in the second step and the lithium iron phosphate particle powder according to the present invention was measured by using an emission plasma analyzer ICAP-6500 (manufactured by Thermo Scientific Co., Manufactured by Mitsui Chemicals, Inc.]. The sample was dissolved in an acid solution at 200 캜 using an autoclave.

The specific surface area of the lithium manganese iron lithium phosphate particles according to the present invention was measured by using MONOSORB (manufactured by Yuasa Ionics Co., Ltd.) after drying and degassing the sample under nitrogen gas at 120 ° C for 45 minutes.

Particle size of the aggregated particles of the phosphoric acid manganese lithium iron particle powder according to the invention a laser diffraction-scattering type particle size distribution sealed Hello's (HELOS) using [(weeks) available from Nippon Laser manufactured, measuring the median diameter D ₅₀ to the dry process Respectively.

Carbon and sulfur content were quantified by combustion in an oxygen stream in a combustion furnace using EMIA-820 (manufactured by Horiba Seisakusho Co., Ltd.).

The compacted body density of lithium manganese iron lithium phosphate powder according to the present invention was calculated from the weight and volume of the compacted body when compacted to 1.5 t / cm ² with a jig of 13 mmφ. Further, the powder electrical resistivity was measured by the two-terminal method using the above-mentioned compression-molded article.

As a result of evaluating the change of particle diameter according to charging / discharging of lithium manganese iron lithium particle powder according to the present invention, a positively charged state in which Li is eliminated by chemical oxidation by NO ₂ BF ₄ is produced, The rate of change of diameter was calculated.

In the acetonitrile solvent, NO ₂ BF ₄ having a molar number twice as high as Li of the above-mentioned particle powder was added to the lithium manganese phosphate lithium particle powder, allowed to stand for one day for chemical oxidation, washed with acetonitrile, Powder was obtained. The particle powders before and after the chemical oxidation were measured by SEM photographs obtained with a scanning electron microscope (SEM) of S-4800 type Hitachi, Ltd., and the primary particle diameters were measured, and the rate of change of the primary particle diameter before and after chemical oxidation was calculated.

The characteristics of the secondary battery by the CR2032 type coin cell were evaluated using olivine-type lithium manganese iron lithium particle powder according to the present invention.

Polyvinylidene fluoride (manufactured by Aldrich) having a degree of polymerization of 460,000 and dissolved in N-methylpyrrolidone (manufactured by Kanto Chemical Co., Inc.) as a binder was mixed with acetylene black as a conductive material and acetylene black : PVDF = 88: 4: 8 and adjusts the positive electrode material slurry so that the% by weight of a doctor blade is applied to the whole phase Al house, 120 ℃, and dried in 10 minutes in air, pressurized to 3 t / cm ² dry sheet To prepare a positive electrode sheet.

2, the separator as a positive electrode sheet thickness punched as a 17 mmφ 0.15 mm Li negative electrode, 19 mmφ punching in cm ² (cell guard # 2400), 1 mol / l of LiPF EC dissolving ₆ and DEC (volume ratio 3: 7) (Manufactured by Kishida Chemical Co., Ltd.) was used to prepare a CR22032 type coin cell (manufactured by Hussen Co., Ltd.).

The charge and discharge characteristics of the nonaqueous electrolyte secondary battery using olivine-type lithium iron phosphate powder as the positive electrode active material according to the present invention were evaluated by measuring the discharge capacity at C / 10, 1C and 5C at room temperature. Here, C / 10 is 10 hours, 1C is 1 hour, 5C is 1/5 hours, and a theoretical capacity of 170 mAh / g of LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) It is a fixed current value. The higher the coefficient of C, the higher the current load characteristic. The voltage range at the time of charging and discharging is not particularly limited, but is set between 2.0 V and 4.5 V in the present invention.

[Example 1]

A solution of MnSO ₄ , H ₃ PO ₄ and NH ₄ OH was mixed and NH ₄ MnPO ₄ was precipitated by neutralization reaction at room temperature. The precipitate was separated by filtration, washed with pure water, and then a solution of LiOH.H ₂ O, FeSO ₄ , H ₃ PO ₄ , and ascorbic acid was added to obtain an aqueous slurry adjusted to the feed ratio shown in Table 1.

The slurry was mixed with a ball mill, and the aggregated particles were pulverized to adjust the particle size. The adjusted slurry had pH = 11, the median diameter of the aggregated particles was D ₅₀ = 5.0 μm, and the main crystalline phase of the aggregated particles after filtration was NH ₄ MnPO ₄ (the first step).

The slurry was hydrothermally treated at 180 ° C for 3 hours, and the obtained compound was filtered, washed with pure water and dried at 70 ° C overnight. From the Rietveld analysis of the obtained XRD pattern, it was confirmed that the yield ratio of LiMn _{1 - x} Fe _x PO ₄ was 95%, and Li ₃ PO ₄ was present in an amount of 5 wt% as an impurity crystalline phase other than the olivine structure. In addition, the crystallite size was 70 nm from Scherr's equation. The content of the impurity sulfur in the dried powder was 0.1 wt% or less (the second step).

To adjust the composition ratio, fine (NH ₄ ) H ₂ PO ₄ was added to the dried powder. The composition of the powder after the adjustment was analyzed using ICP to find that Li: Mn: Fe: P = 1.01: 0.80: 0.20: 1.00 (molar ratio).

10% by weight of sucrose was mixed with agate, and a small amount of pure water was added to the obtained dry powder, and the agglomerated particle diameter was adjusted with a Henschel mixer to obtain a precursor powder (the third step).

The precursor powder obtained in the third step was placed in an alumina crucible and calcined at 650 DEG C for 5 hours under a nitrogen atmosphere. The temperature raising rate was 200 ° C / hr, and the N ₂ gas flow rate was 1 L / min (fourth step).

The obtained powder was a lithium manganese iron phosphate powder having an olivine structure and its composition ratio was the same as the composition ratio of Li, Mn, Fe and P adjusted in the third step.

(Secondary electron image) of the lithium iron phosphate manganese iron particle powder having the olivine structure obtained in Fig. Table 2 shows the production conditions of the first step and the characteristics of the obtained slurry. Table 2 shows the characteristics of the powders in the second step and the production conditions of the third step, The characteristics of the battery are shown in Table 4 and FIG. 2, in which the lithium manganese phosphate lithium particle powder is positive-electrodeized and evaluated as a coin cell.

The rate of change of the primary particle size before and after the removal of Li by chemical oxidation was about 10%.

[Example 2]

The same procedure as in Example 1 was carried out except that the feedstock charge ratio was changed as shown in Table 1.

[Example 3]

Except that a solution of Fe ₃ (PO ₄ ) ₂ .8H ₂ O, Li ₃ PO _4, and LiOH 占_{2 2} O was added to NH ₄ MnPO ₄ obtained in the same manner as in Example 1, and the feed ratio was changed as shown in Table 1 An aqueous slurry was obtained in the same manner as in Example 1. Thereafter, PVA was added as an organic substance in the third step to the slurry after the hydrothermal reaction, and the same treatment as in Example 1 was conducted except that the PVA was evaporated and dried.

[Example 4]

MnSO ₄ , FeSO ₄ , H ₃ PO ₄ and NH ₄ OH were mixed and NH ₄ Mn _0.7 Fe _0.3 PO ₄ was precipitated by neutralization reaction at room temperature. The obtained precipitate was separated by filtration, washed with pure water, and then LiOH.H ₂ O, H ₃ PO ₄ and sucrose were added to obtain an aqueous slurry adjusted to the feed ratio shown in Table 1. Thereafter, the same procedures as in Example 1 were conducted except that polyethylene and stearic acid were used in an amount of 15 wt% in total as organic materials in the third step.

[Example 5]

A solution of MnSO ₄ and Na ₂ CO ₃ was mixed, and MnCO ₃ was precipitated by neutralization at room temperature. The obtained precipitate was separated by filtration, washed with pure water, and then H ₃ PO ₄ was added to precipitate HMnPO ₄ . Thereafter, the same process as in Example 1 was performed except that the raw material input ratio was changed as shown in Table 1.

[Example 6]

MnSO ₄ , FeSO ₄ and Na ₂ CO ₃ were mixed, and HMn _0.9 Fe _0.1 CO ₃ was precipitated by neutralization reaction at room temperature. The obtained precipitate was separated by filtration, washed with pure water, and then a solution of H ₃ PO ₄ was added to precipitate HMn _{0 .9} Fe _{0 .1} PO ₄ . Thereafter, the same process as in Example 1 was performed except that the raw material input ratio was changed as shown in Table 1.

[Example 7]

The raw material charging ratio was changed as shown in Table 1, and the same treatment as in Example 1 was carried out except that the total amount of sucrose and carbon black was 20 wt% as the organic substances in the third step.

[Comparative Example 1]

A solution of MnSO ₄ , H ₃ PO ₄ and NH ₄ OH was mixed and NH ₄ MnPO ₄ was precipitated by neutralization reaction at room temperature. The obtained precipitate was separated by filtration, washed with pure water, and then a solution of LiOH.H ₂ O and ascorbic acid was added to obtain an aqueous slurry adjusted to the feed ratio shown in Table 1. The procedure of Example 1 was repeated except that the particle size of the agglomerated particles of the slurry was not adjusted.

In the first step, since the agglomerated particles of the slurry were not pulverized, the median diameter D ₅₀ of the agglomerated particles was as large as 16 μm, and the yield of LiMnPO ₄ of the olivine structure of the compound obtained after the hydrothermal treatment was as low as 71% by weight . In the lithium manganese phosphate powder obtained by firing, 7 wt% of Li ₃ PO ₄ , which is an impurity crystal phase, was present and the battery characteristics deteriorated.

[Comparative Example 2]

MnSO ₄ , FeSO ₄ , H ₃ PO ₄ and LiOH · H ₂ O were mixed to obtain an aqueous slurry adjusted to the feed ratio shown in Table 1, containing the precipitate obtained by the neutralization reaction at room temperature. The slurry was mixed in a ball mill, the agglomerated particles were pulverized to adjust the particle size, and then heat treated at 180 ° C for 3 hours. The obtained precipitate was separated by filtration, washed with pure water and dried overnight at 70 ° C. Thereafter, treatment was carried out in the same manner as in Example 1. The crystallite size of the obtained dried powder was as large as 260 nm, and the impurity sulfur in the dried powder was 0.12% by weight. The lithium manganese iron lithium particle powder obtained by firing had a large sulfur content and crystallite size, and had poor battery characteristics.

[Comparative Example 3]

In the third step of Example 2, a treatment was carried out in the same manner as in Example 2 except that the organic equivalent of the organic material was 1 wt%. The lithium manganese iron phosphate powder obtained by firing was coarse particles with high electrical resistance and poor battery characteristics.

[Comparative Example 4]

Li ₂ CO ₃ , MnCO ₃ and (NH ₄ ) H ₂ PO ₄ are mixed so that the ratio of Li, Mn and P is 1: 1: 1, and further, in a mixed solvent containing ethanol and water to which PVA is added, The mixture was pulverized and mixed in a ball mill, and the resulting compound was filtered and calcined in air at 700 ° C for 2 hours to obtain a lithium manganese phosphate powder. The obtained lithium manganese phosphate powder was coarse particles having high electrical resistance and poor battery characteristics.

SEM photographs of the lithium manganese phosphate particles powder obtained in FIG. 3 and SEM photographs of Li removed by chemical oxidation are shown in FIG. 4, and Rietveld analysis results of the XRD pattern are shown in FIG. , It was confirmed that a change in the LiMnPO ₄ with fine MnPO ₄ by chemical oxidation.

[Comparative Example 5]

An aqueous slurry was obtained in the same manner as in Example 3. The hydrothermal reaction in the second step was not carried out, and the precipitate in the slurry was separated by filtration, washed with pure water, and dried overnight at 70 ° C. Thereafter, treatment was carried out in the same manner as in Example 1. The lithium manganese iron lithium particle powder obtained by firing contains a large amount of Li ₃ PO ₄ which is an impurity crystal phase, and the battery characteristics are poor.

The nonaqueous electrolyte secondary battery using olivine-type lithium iron phosphate powder as the positive electrode active material according to the present invention had a discharge capacity at C / 10 at room temperature of 115 mAh / g or more, discharge capacity at 1 C at room temperature Of 95 mAh / g or more, and a discharging capacity at room temperature of 5 C was 80 mAh / g or more.

In addition, in order to produce a positively charged state, the primary particle diameter is liable to be 50 to 100 nm when the Li is removed by chemical oxidation with NO ₂ BF ₄ of half the number of moles of Li, and the primary particle size before chemical oxidation The coarse particles larger than 200 nm showed a higher rate of change of primary particle diameters before and after chemical oxidation.

[Examples 8 to 15]

A raw material tuipbi the precursor powder obtained in the second step in the same manner as in Example 1 except changing, as shown in Table _{5, Li 2 CO 3, MnCO} 3, FeC 2 O 4, (NH 4) H 2 PO 4, ( NH ₄ ) ₂ HPO ₄ were added as required and mixed in a ball mill. The composition ratios of Li, Mn, Fe and P were adjusted as shown in Table 5. Thereafter, treatment was carried out in the same manner as in Example 1.

The main component of the obtained powder was a lithium manganese iron phosphate powder having an olivine structure and its composition ratio was the same as the composition ratio of Li, Mn, Fe and P adjusted in the third step.

Table 5 shows the production conditions of the first step and the characteristics of the obtained slurry, Table 6 shows the characteristics of the powder in the second step and the production conditions of the third step, and the iron lithium manganese phosphate particles The powder characteristics of the powders are shown in Table 9, in which lithium iron phosphate manganese phosphate powder was positive-polished and evaluated as a coin cell.

In the lithium manganese iron phosphate powder having an olivine structure according to the present invention, when the content of lithium and phosphorus satisfies Li &gt; P, generation of a Mn ₂ P ₂ O ₇ impurity crystal phase which deteriorates the battery characteristics is suppressed The tendency was seen.

Further, when the unit cell volume V _UC (? ³ ) was in the relationship shown in the formula (1), a higher discharge capacity was exhibited and battery performance tended to be good. This is presumably because the lithium iron phosphate manganese oxide having an olivine structure with less transition metal substitution to Li site and fewer P and O defects is obtained as the small unit cell volume increases.

Further, in the lithium manganese iron phosphate powder having an olivine structure according to the present invention, no impurity crystalline phase is detected, but when Li and P are out of the theoretical stoichiometric ratio, excess Li and P are ion conductive Amorphous phase is formed, and it is considered that the cell characteristics are not adversely affected.

When the lithium manganese phosphate lithium particle powder according to the present invention is positively polarized to evaluate the battery characteristics with the coin cell, the discharge capacity at 5 C is 10 to 30%, and further increase in capacity was confirmed.

From the above results, it can be concluded that the production method of olivine-type lithium manganese iron lithium particle powder according to the present invention requires almost the same amount of raw materials without using an excessive amount of raw materials, which is a low-cost and efficient manufacturing method. Further, it has been confirmed that a highly-charged positive electrode sheet of olivine-type lithium manganese iron phosphate powder having an olivine structure according to the present invention can be produced, and that a secondary battery using the same has a high capacity in terms of current load characteristics.

&Lt; Industrial applicability >

The present invention provides a nonaqueous electrolyte secondary battery having a high energy density per volume and a high current load characteristic by using an olivine-type lithium iron phosphate lithium particle powder produced by a low-cost and efficient manufacturing method as a positive electrode active material .

Claims (9)

A method for producing a lithium iron phosphate LiMn _{1 - x} Fe _x PO ₄ (0.05? _X ? 0.5) particle powder having an olivine structure and comprising a Li compound, a Mn compound, an Fe compound, a P compound and a sugar or an organic acid as raw materials , The raw material charging ratio is in a molar ratio of 0.95? Li / (Mn + Fe)? 2.0, 0.95? P / (Mn + Fe)? 1.3 and 1 to 20 mol% A slurry obtained in the first step and the slurry obtained in the first step is subjected to a hydrothermal treatment at a reaction temperature of 120 to 220 캜 to obtain an aqueous slurry having a pH of 5.5 to 12.5 by neutralization reaction of the mixed solution and to obtain LiMn _{1 - x} Fe _x PO ( ₃ ) to ( ₄ ) wherein the organic compound is added in an amount of 3 to 40 wt% to the compound obtained in the second step and the second step of washing the compound after the crystallization rate is 10 to 250 nm, % To obtain a precursor powder, and the third step in which the precursor powder obtained in the third step is subjected to oxygen concentration And a fourth step of firing at a temperature of 250 to 850 占 폚 in an inert gas or a reducing gas atmosphere of 0.1% or less. The method of claim 1, wherein, in a first step, the median diameter of the aggregated particles in the slurry is from 0.1 to 10 μm, the crystalline _{(NH 4) Mn 1 -α Fe} α PO 4 (0≤α <1) or HMn _{1 -β} Fe _β PO ₄ (0 ≦ _β <1). The production method according to claim 1 or 2, wherein the sugar or organic acid used in the first step is at least one of sucrose, ascorbic acid, and citric acid. The production method according to claim 1 or 2, wherein in the second step, the sulfur content in the compound is not more than 0.1% by weight. The production method according to claim 1 or 2, wherein the organic substance to be added in the third step is at least one of carbon black, a fat compound, a sugar compound, and a synthetic resin. delete delete delete delete

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