JP5429980B2 - Method for producing carbon-olivine-type manganese iron phosphate lithium composite and positive electrode material for lithium ion battery - Google Patents

Description

  The present invention relates to a method for producing a carbon-olivine type lithium manganese iron phosphate composite, and a positive electrode material for a lithium ion battery containing the composite.

Lithium ion batteries (lithium ion secondary batteries) were commercialized in 1991 as new batteries with high energy density, and the market is rapidly expanding as an indispensable power source for electronic devices such as mobile phones and laptop computers. Yes. However, although the battery performance has been improved by improving and developing negative electrode materials and electrolytes, rock salt type lithium cobalt oxide (LiCoO ₂ ) has been frequently used as the positive electrode material from the beginning to the present.

Although this lithium ion battery using LiCoO ₂ is excellent in performance as a small battery, there is a problem that the price fluctuates sharply due to a small reserve of cobalt as a raw material. Therefore, a positive electrode that replaces lithium cobalt oxide As active materials, olivine-type lithium iron phosphate and olivine-type lithium iron iron phosphate in which a part of the iron is substituted with manganese have been studied.

By the way, the positive electrode of a lithium ion battery usually uses LiCoO ₂ or the like as an active material, and binds the conductive material such as a carbon material for enhancing the electron conductivity in the positive electrode to the active material or the conductive aid. And forming a positive electrode mixture having a binder for forming a positive electrode mixture, or forming a layer of such a positive electrode mixture (positive electrode mixture layer) on one or both sides of a conductive substrate serving as a current collector Has been.

  However, since olivine-type lithium iron phosphate and olivine-type lithium manganese phosphate are very low in electronic conductivity, simply forming a positive electrode by coexisting a conductive auxiliary agent does not provide sufficient electron conductivity. It is difficult to ensure excellent battery characteristics.

  Therefore, a technique for increasing the electronic conductivity of olivine-type lithium iron phosphate and olivine-type lithium manganese iron phosphate has been studied.

  In addition to the former olivine-type lithium iron phosphate, the latter olivine-type lithium iron manganese phosphate has also been reported to increase the electron conductivity by forming a composite with carbon (Patent Document 1). ~ 2).

  For example, in Patent Document 1, ferrous phosphate, lithium phosphate, manganese phosphate and a conductive carbon material are mixed, the resulting mixture is pulverized in a dry process, and the pulverized product is fired at 500 to 700 ° C. Thus, it has been reported that olivine-type lithium manganese iron phosphate complexed with carbon is produced. In Patent Document 2, an alkali is added to an aqueous solution in which a divalent iron salt, a divalent manganese salt and phosphoric acid are dissolved. Add, make a coprecipitate containing iron, manganese and phosphorus, mix the coprecipitate with lithium phosphate and conductive carbon material, dry pulverize the resulting mixture, It has been reported to produce olivine-type lithium iron iron phosphate complexed with carbon by firing at 500-700 ° C.

  The electronic conductivity of the olivine-type lithium iron manganese phosphate complexed with carbon is greatly improved compared to the one not complexed with carbon, but it has better battery characteristics. However, it is not sufficient for the development of a lithium ion battery, and a battery having higher electron conductivity is desired.

Japanese Patent No. 4222559 Japanese Patent No. 4260572

  The present invention provides a method for easily and efficiently producing a carbon-olivine-type manganese iron-lithium phosphate composite having high electronic conductivity and capable of producing a lithium ion battery having a high energy density based on an olivine-type lithium manganese iron phosphate. An object of the present invention is to provide a positive electrode material for a lithium ion battery having a high energy density by using the carbon-olivine type lithium manganese iron phosphate composite obtained by the production method.

The present invention that achieves the above object includes the following steps (1) to (4): (1) a step of producing a carbon-manganese iron phosphate composite by precipitation;
(2) a step of producing a coprecipitate containing the carbon-manganese iron phosphate complex and lithium phosphate;
(3) A step of adding and mixing an organic substance to be a carbon precursor to the coprecipitate,
(4) A step of firing a mixture of the coprecipitate and an organic substance that becomes a carbon precursor,
The composition of the olivine type lithium manganese iron phosphate part is represented by the following general formula (1)
Li (Mn _1-x Fe _x ) PO ₄ (1)
(Where X = 0.1 to 0.3)
A carbon-olivine type lithium iron iron phosphate composite represented by the formula:

  In the present invention, after the coprecipitate is produced in the step (2), the coprecipitate is dried and calcined, and the step (3) is converted to the calcined product of the coprecipitate. It is good also as a process of adding the organic substance used as a carbon precursor, and making it the process of mixing, and baking the mixture of the calcined product of the said coprecipitate and the organic substance used as a carbon precursor.

  Furthermore, a positive electrode material for a lithium ion battery comprising a carbon-olivine type manganese iron phosphate lithium composite obtained by the production method of the present invention is also included in the present invention, and the carbon-olivine type manganese iron phosphate composite is also included in the present invention. And the positive electrode material for lithium ion batteries containing 0.1-15 mass% of carbon materials other than carbon derived from the carbon-olivine-type manganese iron phosphate complex is also included in the present invention.

  According to the present invention, a carbon-olivine-type manganese iron phosphate lithium composite having a high electron conductivity suitable as a positive electrode material for a lithium ion battery capable of producing a high energy density lithium ion battery is easily and efficiently produced. it can. Moreover, the carbon-olivine type manganese iron lithium phosphate composite obtained by the production method of the present invention and the positive electrode material for a lithium ion battery of the present invention containing the composite can constitute a high energy density lithium ion battery. . The reason why the present invention can achieve such an effect will be sequentially described in the following [Description of Embodiments].

  In order to improve the electronic conductivity of the positive electrode material for lithium ion batteries having olivine-type lithium manganese iron phosphate, olivine-type lithium manganese iron phosphate and carbon functioning as a conductive additive are uniformly mixed. It is required that In the production method of the present invention, the synthesis of olivine-type lithium manganese iron phosphate and the combination with carbon are simultaneously achieved by a simple and efficient method, and the carbon and olivine-type lithium manganese iron phosphate are uniformly mixed. In addition, since an organic substance that is a precursor of carbon is added and baked, carbon generated from the organic substance added thereafter and carbon already complexed with manganese phosphate or iron phosphate A carbon network with high electron conductivity was formed, thereby enabling the production of carbon-olivine type lithium iron manganese phosphate with high electron conductivity.

  In synthesizing olivine-type lithium iron iron phosphate, first, as described in Patent Document 1, a solid-phase method in which raw material compounds are mixed and baked, or a similar compound, olivine-type lithium iron phosphate, is synthesized. A hydrothermal method in which a mixture of a raw material compound and water as proposed is heated in a pressure vessel can be considered.

  However, the solid phase method requires a long mixing step in order to make the composition uniform when mixing raw material compounds before firing, and cannot be an efficient method. Moreover, in the hydrothermal method, it is necessary to add some raw material compounds in a considerably excessive amount than is theoretically required.

  Therefore, in the present invention, the carbon-manganese iron phosphate complex and the phosphoric acid are obtained by the steps (1) and (2) using a reaction in a liquid that can easily and efficiently perform uniform dispersion and mixing. A coprecipitate with lithium is obtained, and in the subsequent step (3), an organic substance to be a carbon precursor is added to and mixed with the coprecipitate. In the step (4), the coprecipitate and the carbon precursor are mixed. The carbon-olivine-type manganese iron phosphate lithium composite in which a carbon network with high electron conductivity is formed and uniformly formed by firing a mixture with an organic substance to form a body with simple equipment and It succeeded in manufacturing efficiently. Hereinafter, the method of the present invention will be described in detail.

  The step (1) in the method of the present invention is a step of producing a carbon-manganese iron phosphate complex by precipitation. Specifically, for example, an aqueous solution having phosphoric acid, a compound containing divalent manganese and a compound containing divalent iron is added to an aqueous phase in which a carbon material is dispersed, and then the water phase is dissolved in water. The carbon-manganese iron phosphate complex is precipitated by neutralization with a base.

  The carbon material used in the step (1) is not particularly limited as long as it is a powder or a dispersion thereof, but a material having good conductivity is preferred. Specific examples include carbon black (acetylene black, ketjen black, furnace black, lamp black, etc.), graphite, graphite and the like. Carbon materials with shape anisotropy (carbon materials having a fiber-like shape with a certain aspect ratio) such as carbon nanofibers, carbon nanotubes, carbon nanohorns, carbon nanowires, and carbon nanocoils are also used as carbon materials. it can. Among these, acetylene black and ketjen black, which are often used as battery materials, are particularly preferable. In the step (1), it is preferable that the content of the carbon material in the aqueous dispersion of the carbon material is, for example, 0.1 to 10% by mass.

  As phosphoric acid, orthophosphoric acid is preferable. Phosphoric acid may be used as it is, but is preferably used in the form of an aqueous solution. The concentration in the case of an aqueous solution is preferably, for example, 5 to 85% by mass.

  In dispersing the carbon material in water, it is preferable to increase the dispersibility of the carbon material using a known dispersant. As the dispersant, an anionic surfactant, a cationic surfactant, a nonionic surfactant, and the like can be used, and there is no particular limitation. However, the nonionic surfactant has only carbon remaining after firing in the step (4), This is particularly preferable because no unnecessary components remain. As for the amount of the dispersant used, it is sufficient that the carbon material can be dispersed well in water. For example, the dispersant is preferably 0.1 parts by mass or more, particularly 2 parts by mass or more with respect to 100 parts by mass of the carbon material. It is preferably 100 parts by mass or less, particularly preferably 50 parts by mass or less, and further preferably 20 parts by mass or less.

  Further, carbon black paste in which a dispersant is dispersed in advance, carbon black whose dispersibility is improved by surface treatment, or the like may be used.

  The manganese compound used in the aqueous solution having a compound containing divalent manganese is not particularly limited as long as it contains divalent manganese and is water-soluble, but water-soluble divalent manganese iron salt There are few types, and manganese sulfate (manganese sulfate monohydrate, manganese sulfate pentahydrate, etc.) can be mentioned as being easily available industrially.

  The iron compound used in the aqueous solution having a compound containing divalent iron is not particularly limited as long as it contains divalent iron and is water-soluble. There are few types, and ferrous sulfate (such as ferrous sulfate and heptahydrate) is industrially easily available. Normally, when a compound containing divalent iron is used as a raw material and olivine-type lithium iron manganese phosphate is synthesized in the air, iron is oxidized from divalent to trivalent. In this case, synthesis of the precursor before firing is performed in an inert gas atmosphere such as nitrogen gas or argon gas, or, in the final firing step, firing is performed in a reducing gas atmosphere such as hydrogen, and iron is added. It needs to be reduced. However, in the step (1) of the method of the present invention, since the reaction of phosphoric acid, a compound containing divalent manganese and a compound containing divalent iron is performed in the presence of carbon, oxidation of iron occurs. Is prevented. Therefore, the step (1) can be performed in the air, and also in the step (4), it is not necessary to perform firing in a reducing gas atmosphere (however, firing in a reducing gas atmosphere is not necessary). It is not excluded).

In the present invention, the olivine-type lithium iron manganese phosphate portion is represented by the general formula (1), that is, Li (Mn _1-x Fe _x ) PO ₄ , and X = 0.1 to 0.3, This is because when X is smaller than the above, the amount of iron is small, so the capacity (electric capacity) is small, and when X is larger than the above, the ratio of manganese decreases and the voltage decreases. This is because the energy density to be obtained cannot be obtained. That is, manganese has a voltage of about 4.0 V on the basis of lithium, but has a smaller actual capacity (referred to an actually measured capacity rather than a theoretical capacity) compared to iron. On the other hand, iron has a voltage of about 3.4 V on a lithium basis and is lower in voltage than manganese, but has a larger actual capacity than manganese. Therefore, in the present invention, by specifying the ratio of manganese and iron in a specific range, the energy density of olivine-type lithium iron phosphate having an actual capacity of 160 mAh / g is utilized by taking advantage of manganese and iron. Thus, an energy density much higher than that, that is, a large energy density that cannot be obtained with iron alone or manganese alone was obtained.

  In the present invention, a complex of olivine-type lithium manganese iron phosphate and carbon capable of producing a lithium ion battery having a high energy density as described above can be easily and efficiently produced with high electronic conductivity. X, which defines the atomic ratio of manganese to iron in the olivine-type lithium iron manganese phosphate, is within the range of X = 0.1 to 0.3 as described above, and X is 0.15 or more. X is preferably 0.25 or less.

  In the production of the carbon-olivine type lithium manganese iron phosphate composite of the present invention, the concentration of the compound in the aqueous solution having a compound containing divalent manganese is preferably 1 to 20% by mass, It is preferable that the density | concentration of this compound in the aqueous solution which has a compound containing bivalent iron is 1-10 mass%, for example.

  Examples of the water-soluble base used for neutralization include alkali metal hydroxides such as NaOH and KOH; ammonia; various amines. These water-soluble bases are preferably used as an aqueous solution having a concentration of about 1 to 50% by mass, for example. The amount of the water-soluble base used at the time of neutralization is preferably such that the pH of the reaction solution containing the precipitate after addition of the water-soluble base is 7.0 to 12.0.

  In the carbon-olivine type lithium iron phosphate composite finally obtained, the carbon content is preferably 0.1% by mass or more, particularly preferably 1% by mass or more, and particularly preferably 25% by mass or less. 10 mass% or less is preferable (it mentions later in detail). Therefore, in the step (1), the carbon material, phosphoric acid, and divalent manganese are added so that the carbon content in the finally obtained carbon-olivine-type manganese iron-phosphate lithium composite becomes the above preferable value. It is preferable to adjust the ratio of the compound containing and the compound containing divalent iron.

  In the step (1), the temperature of the reaction solution is preferably 0 to 80 ° C. In the step (1), a precipitate is obtained by neutralization with a water-soluble base. However, from the viewpoint of atomization and homogenization of the precipitate (carbon-manganese iron phosphate complex), a carbon material is contained. A water-soluble base (preferably an aqueous solution thereof) is added to a dispersion obtained by adding an aqueous solution containing a compound containing phosphoric acid, divalent manganese and a compound containing divalent iron to the dispersion. ) Is preferably added dropwise over a period of about 1 to 60 minutes, and then stirring is continued for 5 to 60 minutes. For precipitation, it is possible to change the dropping order of the phosphoric acid, the compound containing divalent manganese, the aqueous solution containing the compound containing divalent iron, and the water-soluble base, or perform simultaneous dropping.

  In the step (1), the precipitate of the carbon-manganese iron phosphate complex produced in the reaction solution is taken out by filtration or the like and used for the next step (2). In addition, when many impurities are contained, you may repeat the water washing and filtration of a filter cake.

  As described above, the carbon-manganese iron phosphate composite obtained in the step (1) employs a method of generating manganese iron phosphate in water in which a carbon material is dispersed in advance, for example, a carbon material. Is presumed to have a structure adhered to the surface of manganese iron phosphate. However, depending on the amount of manganese iron phosphate, it is considered that the carbon material (carbon black) cannot cover the entire surface of the manganese iron phosphate, and some of the surface is exposed.

  The process (2) in the method of the present invention is a process for producing a coprecipitate containing the carbon-manganese iron phosphate complex obtained in the process (1) and lithium phosphate. Examples of the step (2) include the following step (2-1) or step (2-2).

  In the step (2-1), first, the carbon-manganese iron phosphate complex obtained in the step (1) is preferably added to water containing a dispersant, and the mixture is added for a predetermined time (for example, 1 to 60). Stirring to obtain a slurry in which the carbon-manganese iron phosphate complex is uniformly dispersed. Then, phosphoric acid is added to the slurry, and a lithium compound-containing aqueous solution is further added to produce a coprecipitate containing a carbon-manganese iron phosphate complex and lithium phosphate.

  In dispersing the carbon-manganese iron phosphate complex in water, preferably, water with a dispersant added in advance is prepared, and the carbon-manganese iron phosphate complex is gradually added while stirring this. It is preferable to adopt the method of doing. As the dispersant, an anionic surfactant, a cationic surfactant, a nonionic surfactant, or the like can be used, and there is no particular limitation, but only carbon remains after firing in the step (4), and no unnecessary components remain. Therefore, a nonionic surfactant is particularly preferable.

  The content of the carbon-manganese iron phosphate complex in water is preferably 1 to 50% by mass, for example. In addition, the amount of the dispersant used is not limited as long as the carbon-manganese iron phosphate complex can be satisfactorily dispersed in water. For example, the dispersant is 0 with respect to 100 parts by mass of the carbon-manganese iron phosphate complex. 0.1 parts by mass or more is preferable, 0.2 parts by mass or more is particularly preferable, 10 parts by mass or less is preferable, 5 parts by mass or less is particularly preferable, and 2.5 parts by mass or less is more preferable.

  As the phosphoric acid used in the step (2-1), orthophosphoric acid is preferable as in the step (1). Moreover, although phosphoric acid may be used as it is, it is preferably used in the form of an aqueous solution. The concentration in the case of an aqueous solution is preferably, for example, 5 to 85% by mass.

  The lithium compound related to the lithium compound-containing aqueous solution used in the step (2-1) is not particularly limited as long as it is water-soluble, but lithium hydroxide is particularly preferable. Moreover, when using lithium hydroxide as a lithium compound, it is preferable that the density | concentration of lithium hydroxide in the lithium compound containing aqueous solution is 0.1-17 mass%, for example.

  In the step (2-1), the temperature of the reaction solution is preferably 0 to 80 ° C. In the step (2-1), a coprecipitate is obtained by adding a lithium compound-containing aqueous solution to water in which the carbon-manganese iron phosphate complex and phosphoric acid are present. The coprecipitate is atomized. From the viewpoint of homogenization, the lithium compound-containing aqueous solution is dropped in a time of about 1 to 60 minutes while sufficiently stirring the water in which the carbon-manganese iron phosphate complex and phosphoric acid are present, and then 5 to 60 minutes It is preferable to continue stirring. Furthermore, the coprecipitate can be produced by changing the dropping order of the phosphoric acid and the lithium compound-containing aqueous solution, or simultaneously dropping the phosphoric acid and the lithium compound-containing aqueous solution.

  In the step (2-2), phosphoric acid and a lithium compound-containing aqueous solution are mixed to form a lithium phosphate precipitate, and the carbon-manganese iron phosphate composite obtained in the step (1) is mixed in the water. The coprecipitate containing a carbon-manganese iron phosphate complex and lithium phosphate is obtained by adding a body and dispersing uniformly by stirring or the like. In the step (2-2), phosphoric acid and a lithium compound-containing aqueous solution are mixed in an aqueous phase in which a carbon material is dispersed in advance, and then the carbon-manganese phosphate obtained in the step (1). An iron complex may be added. As the carbon material, various materials exemplified in the step (1) can be used, and acetylene black and ketjen black are particularly preferable.

  The same thing as what can be used at the process of (2-1) can be used for the phosphoric acid and lithium compound containing aqueous solution which concern on the process of (2-2). Moreover, it is preferable to add a dispersing agent in the reaction liquid before adding the carbon-manganese iron phosphate composite obtained in the step (1). The same dispersant as in the step (2-1) can be used as the dispersant, and the amount used is preferably the same as in the step (2-1).

  In the step (2-2), when water in which a carbon material is dispersed in advance is used, it is preferable to add a dispersant to the water. The same dispersant as in the step (2-1) can be used as the dispersant. The amount used is preferably, for example, 0.1 parts by mass with respect to a total amount of 100 parts by mass of the carbon material added in advance and the carbon-manganese iron phosphate composite added thereafter, in particular, 0. 2 parts by mass or more is preferable, 10 parts by mass or less is preferable, and 5 parts by mass or less is particularly preferable.

  In the step (2-2), the temperature of the reaction solution is preferably 0 to 80 ° C. In the step (2-2), a precipitate (lithium phosphate precipitate) is obtained by mixing phosphoric acid and a lithium compound-containing aqueous solution. The lithium phosphate precipitate is atomized and homogenized. From this point of view, for example, phosphoric acid is used in the form of an aqueous solution, while the phosphoric acid aqueous solution is sufficiently stirred, the lithium compound-containing aqueous solution is added dropwise over a period of about 1 to 60 minutes, and the carbon-manganese iron phosphate composite is further added. It is preferable to continue stirring for 5 to 60 minutes after adding the body. In addition, for the formation of a lithium phosphate precipitate, phosphoric acid (preferably a phosphoric acid aqueous solution) is dropped into a lithium compound-containing aqueous solution, or phosphoric acid (preferably a phosphoric acid aqueous solution) and a lithium compound-containing aqueous solution in water It is also possible to perform simultaneous dripping.

  In either the step (2-1) or the step (2-2), a coprecipitate containing a carbon-manganese iron phosphate complex and lithium phosphate (hereinafter referred to as “carbon-manganese iron phosphate— The pH of the reaction solution at the time of production (referred to as “lithium phosphate coprecipitate”) is preferably 7.0 or more, particularly 9.0 or more, preferably 12.0 or less, particularly preferably 11.0 or less.

  The step (3) in the present invention includes the carbon-manganese phosphate iron-lithium phosphate coprecipitate obtained through the step (2-1) as described above or the step (2-2). In this step, an organic substance to be a carbon precursor is added to the slurry and mixed.

  In the present invention, the above-mentioned “organic substance to be a carbon precursor” means that “a part of carbon of the carbon-olivine-type lithium manganese iron phosphate composite” is formed through the firing step (4). It means “organic substance”, and does not mean “organic substance changes to constitute a carbon precursor”. That is, the “organic substance to be a carbon precursor” has the same meaning as “organic substance as a carbon precursor”. Examples of the organic substance that serves as the carbon precursor include monosaccharides such as glucose and fructose, disaccharides such as sucrose (sucrose), polysaccharides including trisaccharides or more such as cellulose, dextrin, and starch, and derivatives thereof. Can be suitably used, but it is inexpensive and water-soluble, and can be uniformly mixed with the carbon-manganese iron phosphate-lithium phosphate coprecipitate using water as a medium. Saccharides are preferred, and sucrose is particularly preferred.

  The organic substance to be the carbon precursor may be added as it is to the slurry containing the carbon-manganese iron phosphate-lithium phosphate coprecipitate, but is preferably added as an aqueous solution previously dissolved in water. Although the density | concentration of the organic substance used as the carbon precursor in that case is not specifically limited, 10-50 mass% is preferable. Further, at that time, it is preferable to add a dispersant such as a nonionic surfactant to thoroughly disperse the organic substance serving as the carbon precursor.

  The addition of the organic substance serving as the carbon precursor or an aqueous solution thereof is preferably performed while stirring and mixing the slurry containing the carbon-manganese iron phosphate-lithium phosphate coprecipitate, and about 10 minutes after the addition. It is preferable to continue stirring and mixing.

  Then, the slurry containing the mixture of carbon-manganese iron phosphate-lithium phosphate coprecipitate obtained as described above and an organic substance as a carbon precursor is wet-ground by a wet media pulverizer such as a sand mill or a ball mill. It is preferable to disperse them.

  That is, when an organic substance as a carbon precursor is added to and mixed with carbon-manganese iron phosphate-lithium phosphate coprecipitate, the resulting mixture tends to aggregate and form secondary particles. Rather than performing the next firing (4), it is easier to obtain a high-capacity lithium ion battery when the aggregated state is wet-pulverized by a wet media pulverizer to form primary particles and dispersed and then fired.

  A mixture of the carbon-manganese iron phosphate-lithium phosphate coprecipitate that has undergone the above-described steps and the organic substance that becomes the carbon precursor is taken out from the liquid by drying and removing moisture.

  The drying method and conditions are not particularly limited as long as moisture in the mixture can be removed. From the viewpoint of suppressing oxidation of iron in the carbon-manganese iron phosphate-lithium phosphate coprecipitate, it is preferable to dry in an inert gas such as nitrogen gas at a lower temperature, or to dry by reduced pressure drying. Although it is considered, in the case of the carbon-manganese iron phosphate-lithium phosphate coprecipitate according to the present invention, oxidation of iron hardly occurs even when drying using a hot air dryer or the like in the atmosphere. As a drying method, drying with a hot air dryer can also be employed. And when drying by this hot air dryer, it is preferable to dry with a hot air of 40-150 degreeC for about 1 to 24 hours, for example.

  The carbon-manganese iron phosphate-lithium phosphate coprecipitate obtained in the step (2-1) has, for example, a structure in which lithium phosphate is attached so as to cover the surface of the carbon-manganese iron phosphate complex. Presumed to be taken. In addition, in the step (2-2), a carbon-manganese phosphate iron-lithium phosphate co-product obtained by employing a method of adding a phosphoric acid aqueous solution and a lithium compound-containing aqueous solution to water in which a carbon material is dispersed in advance. In the deposit, for example, it is presumed that the carbon-manganese iron phosphate complex and the lithium phosphate with the carbon material attached to the surface coexist. And the organic substance used as the carbon precursor added to the carbon-manganese iron phosphate-lithium phosphate coprecipitate forms a network of carbon with a high electron conductivity with the carbon of the coprecipitate upon firing, thereby conducting electron conduction. It is presumed to increase the nature. In the present invention, in the step (3), as a carbon material for forming a carbon network, an organic substance that becomes a carbon precursor is added because the organic substance that becomes such a carbon precursor is water or It is soluble in an organic solvent such as alcohol and is mixed with a coprecipitate containing a carbon-manganese iron phosphate complex and lithium phosphate in a solution, and the organic substance that becomes the carbon precursor is This is because the surface is covered and carbonized by subsequent firing to form a network of carbon in the coprecipitate and carbon having high electron conductivity. That is, in the step (3), a carbon network with higher electron conductivity can be formed by adding an organic substance serving as a carbon precursor than by adding a particulate conductive carbon material such as carbon black. Therefore, as in Patent Document 2, the electronic conductivity is lower than that in the case where a particulate conductive carbon material is added to a coprecipitate containing iron, manganese and phosphorus without first forming a complex with carbon. This is because a high carbon network can be formed.

  In the step (4) of the method of the present invention, a mixture of the carbon-manganese iron phosphate-lithium phosphate coprecipitate obtained in the step (3) and an organic substance serving as a carbon precursor is calcined, and carbon- This is a process for producing an olivine-type lithium phosphate complex.

  As a calcination temperature in the process of (4), it is preferable to set it as 500-900 degreeC, for example. If the firing temperature is too low, it may be difficult to produce a carbon-olivine type lithium manganese iron phosphate composite, and if it is too high, some decomposition may occur. Firing is preferably performed, for example, in an inert gas atmosphere such as nitrogen gas or argon gas, but can also be performed in a reducing gas atmosphere such as hydrogen gas.

  The firing time in the step (4) is preferably 0.1 to 10 hours, for example. Moreover, when performing baking in the process of (4) in nitrogen gas atmosphere, it is preferable that the flow volume of nitrogen gas shall be 0.1-50 L / min, for example.

  In addition, if necessary, a mixture of carbon-manganese iron phosphate-lithium phosphate coprecipitate before firing and an organic substance serving as a carbon precursor, or a carbon-olivine-type lithium manganese iron phosphate composite obtained after firing The body can also be pulverized or compression molded.

  In the carbon-olivine type lithium iron manganese phosphate composite according to the present invention, the carbon content is preferably 0.1% by mass or more, and preferably 25% by mass or less. If the carbon content is too low, the effect of improving the electronic conductivity may be reduced. If the carbon content is too high, the content of the olivine-type lithium iron phosphate is reduced, so that the capacity of the battery using this as a positive electrode material is increased. Can be difficult. The carbon content is more preferably 1% by mass or more and 10% by mass or less from the viewpoint of improving the charge / discharge characteristics of the battery using the composite and the bulk density of the composite. It is more preferable.

In the method of the present invention, the reaction in each step is considered to proceed as in the following formulas (A) to (C). The following formula (A) shows the reaction in the above step (1), formula (B) in the step (2), and formula (C) in the step (4). In addition, the process of adding and mixing the organic substance which becomes a carbon precursor to the coprecipitate of (3) is merely physical mixing, and there is no chemical reaction. In the following formulas (A) to (C), the raw material compounds used are merely examples, and the method of the present invention is not limited to the use of these raw material compounds. For example, manganese phosphate [Mn ₃ (PO ₄ ) ₂ ] has trihydrate, pentahydrate, and heptahydrate, but is shown as using trihydrate. Also, in the step (2), water (H ₂ O) is generated, but the amount of iron in the manganese iron is represented by X, and it is difficult to specify the number of moles of the generated water. Therefore, the display of H ₂ O is omitted in the formula (B).

3 (1-X) MnSO ₄ · 5H ₂ O + 3XFeSO ₄ · 7H ₂ O + 2H ₃ PO ₄ + 6NaOH → (1-X) Mn ₃ (PO ₄ ) ₂ · 3H ₂ O ↓ + XFe ₃ (PO ₄ ) ₂ · 8H ₂ O ↓ + 3Na ₂ SO ₄ + 2H ₂ O (A)
(1-X) Mn ₃ (PO ₄ ) ₂ · 3H ₂ O ↓ + XFe ₃ (PO ₄ ) ₂ · 8H ₂ O ↓ + 3LiOH · H ₂ O + H ₃ PO ₄ → (1-X) Mn ₃ (PO ₄ ) ₂・ 3H ₂ O + XFe ₃ (PO ₄ ) ₂ · 8H ₂ O ↓ + Li ₃ PO ₄ (B)
(1-X) Mn ₃ (PO ₄ ) ₂ · 3H ₂ O + XFe ₃ (PO ₄ ) ₂ · 8H ₂ O + Li ₃ PO ₄ → 3Li (Mn _1-x Fe _x ) PO ₄ (C)

  Thus, in the method of the present invention, since carbon-manganese iron phosphate-lithium phosphate coprecipitate is produced in two stages of the above formula (A) and the above formula (B), divalent manganese is contained. Impurities contained in the compound to be produced, impurities contained in the compound containing divalent iron, by-products contained in the carbon-manganese iron phosphate complex [when using manganese sulfate or ferrous sulfate, In order to remove bowsho (sodium sulfate), ammonium sulfate, etc., washing with water may be performed after the above formula (A) [that is, after step (1)]. Even if such water washing is performed, the elution of the lithium compound does not occur, and the molar ratio of each element does not change. Therefore, in the final coprecipitate [coprecipitate obtained in the step (2)] The molar ratio of Li, Mn, Fe, and P can be easily controlled, and the use of an excess lithium compound is unnecessary, so that it can be manufactured at low cost and is efficient. Furthermore, the method of the present invention is also efficient in that the reaction can be performed in the vicinity of the theoretical equivalent.

  Incidentally, in the above-described hydrothermal method and the coprecipitation method other than the method of the present invention, there are many examples in which the lithium-containing compound serving as the lithium source is used in excess of the theoretically required amount. In solution methods such as hydrothermal method and coprecipitation method using manganese sulfate pentahydrate, ferrous sulfate heptahydrate, phosphoric acid and lithium hydroxide, one step shown in the following formula (D) A precipitate is obtained by precipitation, and this is fired to obtain olivine-type lithium iron manganese phosphate.

3 (1-X) MnSO ₄ · 5H ₂ O + 3XFeSO ₄ · 7H ₂ O + 3H ₃ PO ₄ + 9LiOH · H ₂ O → (1-X) Mn ₃ (PO ₄ ) ₂ · 3H ₂ O ↓ + XFe ₃ (PO ₄ ) ₂・ 8H ₂ O ↓ + Li ₂ PO ₄ ↓ + 3Li ₂ SO ₄ (D)

The precipitate obtained by this reaction is mainly composed of Mn ₃ (PO ₄ ) ₂ .3H ₂ O, Fe ₃ (PO ₄ ) ₂ .8H ₂ O and Li ₃ PO ₄ , and olivine-type manganese phosphate after firing. For iron lithium, the theoretical molar ratio is [Mn ₃ (PO ₄ ) ₂ .3H ₂ O + Fe ₃ (PO ₄ ) ₂ .8H ₂ O]: Li ₃ PO ₄ = 1: 1. However, since simple filtration contains some Li ₂ SO ₄ , it is necessary to wash the precipitate (coprecipitate) with water in order to remove it. When impurities are mixed in, it is expected to cause a capacity reduction during the charge / discharge test of the olivine-type lithium iron manganese phosphate finally obtained, and it is preferable to remove impurities as much as possible. However, since Li ₃ PO ₄ or the Li content contained in the precipitate is dissolved by washing with water, the problem is that the molar ratio deviates from the theoretical value when removing impurities.

  On the other hand, in the method of the present invention, as described above, the formation of the carbon-manganese iron phosphate-lithium phosphate coprecipitate is performed in a two-step reaction, and therefore, impurities are removed after the first-step reaction. Even if washing is performed, since no lithium-containing compound coexists at that time, there is no reduction in the amount of the lithium-containing compound by washing with water, and a reaction near the theoretical equivalent is possible.

  The carbon-olivine type manganese iron lithium phosphate composite obtained by the method of the present invention has the characteristics possessed by the olivine type lithium manganese iron phosphate and has enhanced electron conductivity, and is a positive electrode material for a lithium ion battery. Suitable for use as. In order to construct a positive electrode for a lithium ion battery using the carbon-olivine type manganese iron phosphate lithium composite according to the present invention, for example, the carbon-olivine type manganese iron iron phosphate composite is used as it is as a positive electrode material. Other than the above, as in the case of a conventionally known positive electrode, a molded body of a positive electrode mixture containing a binder and, if necessary, a conductive additive such as a carbon material may be used. Moreover, you may form these positive mixes as a positive mix layer in the single side | surface or both surfaces of the electroconductive base | substrate used as a collector as needed.

  Furthermore, the carbon-olivine type manganese iron phosphate lithium complex according to the present invention method and a carbon material other than carbon derived from the carbon-olivine type lithium manganese iron phosphate, the positive electrode material for lithium ion batteries of the present invention A positive electrode material for a lithium ion battery may be formed by adding a binder to the positive electrode material to form a positive electrode mixture. Examples of the carbon material include various carbon materials exemplified above used in the production of a carbon-olivine type lithium manganese iron phosphate composite [various carbon blacks; various carbon materials having shape anisotropy (a certain aspect ratio). Carbon material having a shape similar to that of the fiber)) and the like. In particular, in the case of the carbon material having the shape anisotropy exemplified above, the conductive path between the carbon-olivine type manganese iron-lithium phosphate composites can be favorably formed from the shape, so that the electron conductivity is further increased. The charge / discharge characteristics of a lithium ion battery using the same can be further improved.

  In the positive electrode material for a lithium ion battery containing the carbon-olivine-type manganese iron phosphate lithium composite and the carbon material, the content of the carbon material other than carbon derived from the carbon-olivine-type manganese iron lithium phosphate composite, For example, it is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 15% by mass or less, and more preferably 10% by mass or less. When the content of the carbon material other than carbon derived from the carbon-olivine type manganese iron phosphate lithium composite is too low, the effect of using the carbon material may be reduced. In addition, if the content of carbon materials other than carbon derived from the carbon-olivine-type manganese iron phosphate lithium composite is too high, the amount of olivine-type lithium manganese iron phosphate acting as an active material in the positive electrode decreases. Therefore, the energy density of a lithium ion battery using this may be reduced. In particular, in the case of a carbon material having the above shape anisotropy, the specific surface area is relatively small, so the content of carbon materials other than carbon derived from the carbon-olivine-type manganese iron lithium phosphate composite is too high. In some cases, the number of contact points with lithium manganese iron phosphate may be reduced.

  When a lithium ion battery is constructed using the carbon-olivine type lithium manganese iron phosphate composite according to the method of the present invention and a positive electrode for a lithium ion battery using the positive electrode material of the present invention, a negative electrode, a separator, There are no particular restrictions on the various configurations such as the water electrolyte and the outer package, and the same configurations as those of conventionally known lithium ion batteries can be employed.

  In power supply applications for small devices such as mobile phones and personal computers, the use of lithium-ion batteries continues to expand due to their high performance, but in the future, they will be used for large-scale devices such as automobiles and industrial vehicles. The price and safety are the bottleneck. By using olivine-type lithium manganese iron phosphate, which is highly safe, and easily and efficiently manufactured by the method of the present invention, low costs have been achieved, and lithium-ion batteries have been rapidly deployed for use in large equipment. It is expected.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention, and all modifications made without departing from the gist of the preceding and following descriptions are included in the technical scope of the present invention. In the following Examples and Comparative Examples, “%” indicating the concentration of a solution, dispersion, etc. is% based on mass unless otherwise indicated.

Example 1
(1-1) Production of Carbon-Manganese Iron Phosphate Complex Ion-exchanged water 190 cm ³ was placed in a 2 L separable flask, and a nonionic surfactant [“Emulgen MS-110 (trade name)” manufactured by Kao Corporation]] After adding 0.5 g, 2.4 g of acetylene black powder [Denka Black (trade name) manufactured by Denki Kagaku Kogyo Co., Ltd., particle size: 35 nm] was added and stirred for 15 minutes to obtain a carbon black dispersion. Thereafter, an aqueous solution prepared by dissolving 76.9 g of 85% phosphoric acid, 192.8 g of manganese sulfate pentahydrate and 55.6 g of ferrous sulfate heptahydrate in 540 cm ³ of ion-exchanged water in advance is used. Added to the black dispersion and stirred for 10 minutes. Further, 227.1 g of a 15% aqueous ammonia solution was added to the carbon black dispersion, and the mixture was stirred for 15 minutes and filtered to obtain a carbon-manganese iron phosphate composite.

(1-2) Production of carbon-manganese iron phosphate-lithium phosphate coprecipitate Ion-exchanged water 615 cm ³ was placed in a 2 L separable flask, and nonionic surfactant [Emulgen MS-110 (product of Kao Corporation) Name)]] After adding 0.5 g, the whole carbon-manganese iron phosphate composite obtained in (1-1) was added and stirred for 15 minutes to obtain a carbon-manganese iron phosphate composite dispersion. . Thereafter, 38.4 g of 85% phosphoric acid was added to the carbon-manganese iron phosphate complex dispersion, and an aqueous solution in which 41.9 g of lithium hydroxide monohydrate was dissolved in 380 cm ³ of ion-exchanged water in advance. After adding and stirring for 10 minutes, it was set as the slurry liquid containing a carbon-manganese iron phosphate-lithium phosphate coprecipitate.

(1-3) Addition of organic substance serving as carbon precursor To the carbon-manganese iron phosphate-lithium phosphate coprecipitate obtained in (1-2) above, 28.0 g of sucrose as an organic substance serving as a carbon precursor. After adding a 40% aqueous solution in which ion is dissolved in ion-exchanged water with stirring, the mixture is further stirred for 10 minutes and mixed to obtain a slurry liquid of a mixture of carbon-manganese iron phosphate-lithium phosphate coprecipitate and sucrose. It was.

(1-4) Firing The slurry liquid obtained in (1-3) above is placed in a horizontal sand mill ["Dino Mill MULTI LAB type (trade name)" manufactured by Willy et Bacofen, Inc.], and 0.5 mm is further contained therein. The zirconia beads having a diameter were filled and wet pulverized to disperse a mixture of carbon-manganese iron phosphate-lithium phosphate coprecipitate and sucrose. The dispersed slurry was dried at 70 ° C. under reduced pressure, and the obtained dried product was pulverized by rotating for 72 hours using a 1 L nylon pot containing 2 cm diameter zirconia balls. After pulverization, it was fired in a nitrogen stream at 700 ° C. for 5 hours to obtain a carbon-olivine type lithium manganese iron phosphate composite in the form of particles.

  About the carbon-olivine type manganese iron phosphate complex obtained as described above, analysis of molar ratio by ICP, confirmation of crystalline component using powder X-ray diffractometer, and fully automatic elemental analyzer All carbon contents were measured. The results and measurement methods are shown below.

[Analysis of molar ratio by ICP]
Part of the carbon-olivine type lithium iron phosphate complex obtained in (1-4) above is placed in 20% hydrochloric acid and dissolved by heating. Insoluble matter is removed by filtration, and then the filtrate is diluted. The concentration of hydrochloric acid was adjusted to 1% by mass, and each of the coprecipitates in the filtrate after concentration adjustment was determined by ICP emission analysis [“CCD-ICP emission analysis apparatus CIROS-120 (trade name)” manufactured by Rigaku Corporation]. When the ratio of components (molar ratio) was calculated, it was confirmed that Li: Mn: Fe: P = 1: 0.8: 0.2: 1.

[Confirmation of crystalline component using powder X-ray diffractometer]
The carbon-olivine type manganese iron phosphate complex obtained in (1-4) above was subjected to a powder X-ray diffractometer [manufactured by PANalytical “Fully Automatic Powder X-ray Diffractometer X′Pert PRO (trade name)”]. X-ray diffraction measurement was performed under the conditions of an anti-cathode Cu (Ni filter), a tube voltage of 45 kV, and a current of 40 mA. From the obtained diffraction pattern, the crystalline component was olivine type lithium manganese iron phosphate LiMn _0.8 Fe. _0.2 PO ₄ was confirmed.

[Measurement of carbon content using a fully automatic elemental analyzer]
The carbon-olivine type manganese iron phosphate lithium complex obtained in the above (1-4) was subjected to elemental analysis using a fully automatic elemental analyzer ["vario ELIII (trade name)" manufactured by Elemental Co., Ltd.], and the carbon -It confirmed that 5.2 mass% of carbon content was contained in the olivine type lithium manganese iron phosphate composite.

Example 2
Except that the amount of sucrose added was 13.7 g, operation was performed under the same conditions as in Example 1 to obtain a carbon-olivine type lithium manganese iron phosphate composite.

  The obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1. As a result, it was confirmed that 3.1% by mass of carbon was contained in the carbon-olivine-type lithium iron manganese phosphate composite.

Example 3
Except that the amount of sucrose added was 6.8 g, operation was performed under the same conditions as in Example 1 to obtain a carbon-olivine type lithium manganese iron phosphate composite.

  The obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1. As a result, it was confirmed that 2.0% by mass of carbon was contained in the carbon-olivine type lithium manganese iron phosphate composite, but the other components were the same as in Example 1.

Example 4
(4-1) Manufacture of carbon-manganese iron phosphate composite The same operation as (1-1) of Example 1 was performed, and the same carbon-manganese iron phosphate composite as Example 1 was obtained.

(4-2) Manufacture of carbon-manganese iron phosphate-lithium phosphate coprecipitate Ion-exchanged water 615 cm ³ was placed in a 2 L separable flask, and nonionic surfactant [Emulgen MS-110 (product of Kao Corporation) Name)]] After adding 0.5 g, the whole carbon-manganese iron phosphate composite obtained in (1-1) was added and stirred for 15 minutes to obtain a carbon-manganese iron phosphate composite dispersion. . Thereafter, 38.4 g of 85% phosphoric acid was added to the carbon-manganese iron phosphate composite dispersion, and an aqueous solution in which 41.9 g of lithium hydroxide monohydrate was previously dissolved in 380 cm ³ of ion-exchanged water. Was added and stirred for 10 minutes, followed by filtration to obtain a carbon-manganese iron phosphate-lithium phosphate coprecipitate.

(4-2-1) Drying and calcination The coprecipitate obtained in (4-2) was dried in a vacuum dryer at 40 ° C. for 24 hours. In addition, about the obtained dried material, when the molar ratio by ICP was analyzed similarly to Example 1, the molar ratio of each component was Li: Mn: Fe: P = 1: 0.8: 0.2: 1

  The dried product obtained as described above was placed in a 1 L nylon pot filled with 2 cm of zirconia balls and rotated for 72 hours for pulverization. After pulverization, in a nitrogen stream at 500 ° C. for 5 hours. It was calcined under the conditions of

(4-3) Addition of organic substance as carbon precursor Disperse 150 g of the calcined product obtained in (4-2-1) above in an aqueous solution in which 22.4 g of sucrose was previously dissolved in 425 cm ³ of ion-exchanged water. Thus, a slurry liquid of a mixture of a calcined carbon-manganese iron phosphate-lithium phosphate coprecipitate and sucrose was obtained.

(4-4) Firing A slurry of a mixture of the calcined product of carbon-manganese iron phosphate-lithium phosphate coprecipitate obtained in (4-3) and sucrose and a horizontal sand mill (manufactured by Willy et Bacofen) DYNOMILL MULTI LAB type (trade name)), filled with 0.5 mm diameter zirconia beads and wet pulverized, and calcined carbon-manganese iron phosphate-lithium phosphate coprecipitate and sucrose The mixture was dispersed. The dispersed slurry was dried under reduced pressure at 70 ° C., and the obtained pulverized powder was fired in a nitrogen stream at 700 ° C. for 5 hours to obtain a carbon-olivine type lithium manganese iron phosphate composite.

The obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1. As a result, the molar ratio of each component was Li: Mn: Fe: P = 1: 0.8: 0. 2: 1, the crystalline component was confirmed to be the olivine-type phosphate lithium manganese iron _LiMn 0.8 _Fe 0.2 PO _4, also, the carbon - the lithium manganese iron in the complex olivine-type phosphate It was confirmed that 5.1% by mass of carbon was contained.

Example 5
(5-1) Manufacture of carbon-manganese iron phosphate composite The same operation as (1-1) of Example 1 was performed, and the same carbon-manganese iron phosphate composite as Example 1 was obtained.

(5-2) Production of Carbon-Manganese Iron Phosphate-Lithium Phosphate Coprecipitate The same operation as in Example 1-2 (1-2) was carried out, and the same carbon-manganese iron phosphate as in Example 1 was used. A slurry liquid of lithium phosphate coprecipitate was obtained.

(5-3) Addition of organic substance as carbon precursor 40% aqueous solution in which 28.0 g of sucrose was dissolved in ion-exchanged water in the carbon-manganese iron phosphate-lithium phosphate coprecipitate obtained as described above. After stirring, the mixture was further stirred for 10 minutes and mixed to obtain a slurry liquid of a mixture of carbon-manganese iron phosphate-lithium phosphate coprecipitate and sucrose.

(5-4) Firing The slurry liquid of the mixture of carbon-manganese iron phosphate-lithium phosphate coprecipitate and sucrose obtained as described above was dried at 70 ° C. under reduced pressure, and in a nitrogen stream, Firing was performed at 700 ° C. for 5 hours to obtain a carbon-olivine type lithium manganese iron phosphate composite.

The carbon-olivine type manganese iron phosphate lithium composite obtained as described above was analyzed in the same manner as in Example 1. As a result, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was li: Mn: Fe: P = 1: 0.8: 0.2: 1 and crystalline component, it is confirmed as olivine-type phosphate lithium manganese iron _LiMn 0.8 _Fe 0.2 PO _4, It was also confirmed that the carbon-olivine type lithium manganese iron phosphate composite contained 5.1% by mass of carbon.

Comparative Example 1
In Comparative Example 1, a carbon-olivine type lithium iron iron phosphate composite was produced by adopting a solid phase method as a method for producing olivine type lithium iron iron phosphate.

Manganese phosphate trihydrate [Mn ₃ (PO ₄ ) ₂ .3H ₂ O], ferrous phosphate octahydrate [Fe ₃ (PO ₄ ) ₂ .8H ₂ O] and lithium phosphate ( Li ₃ PO ₄ ) is blended so that the element ratio of lithium, manganese, and iron is 1: 0.8: 0.2, and acetylene black [Denka Black (Denki Kagaku Kogyo Co., Ltd. Product name) ”] was added so that the carbon content after firing was 5.0% by mass, and mixed for 10 hours using a planetary ball mill (“ PM-100 (trade name) ”manufactured by Lecce) in a dry method. The obtained mixture was baked in a nitrogen stream at 700 ° C. for 5 hours, and the obtained baked product was pulverized with a simple cutter mill to obtain a composite.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.8: 0.2: 1, most of the crystalline component that is identified as olivine-type phosphate lithium manganese iron _LiMn 0.8 _Fe 0.2 PO _4, also, the It was confirmed that 5.1% by mass of carbon was contained in the carbon-olivine type lithium iron manganese phosphate composite.

Comparative Example 2
Also in Comparative Example 2, a carbon-olivine type lithium manganese iron phosphate composite was produced by adopting a solid phase method as a method for producing the olivine type lithium manganese iron phosphate. However, in Comparative Example 2, acetylene black was used as Comparative Example 1 as a carbon component, whereas sucrose as a carbon precursor was used to produce a carbon-olivine-type lithium manganese iron phosphate composite. went.

Manganese phosphate trihydrate [Mn ₃ (PO ₄ ) ₂ .3H ₂ O], ferrous phosphate octahydrate [Fe ₃ (PO ₄ ) ₂ .8H ₂ O] and lithium phosphate ( Li ₃ PO ₄ ) is mixed so that the element ratio of lithium, manganese, and iron is 1: 0.8: 0.2, and the carbon content after baking sucrose is 5.0 mass%. In addition, it was mixed for 10 hours using a planetary ball mill (“PM-100 (trade name)” manufactured by Lecce) by a dry method. The obtained mixture was baked in a nitrogen stream at 700 ° C. for 5 hours, and the obtained baked product was pulverized by a simple cutter mill to obtain a composite.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.8: 0.2: 1, most of the crystalline component that is identified as olivine-type phosphate lithium manganese iron _LiMn 0.8 _Fe 0.2 PO _4, also, the It was confirmed that 5.1% by mass of carbon was contained in the carbon-olivine type lithium manganese phosphate composite.

Comparative Example 3
Also in this comparative example 3, the solid-phase method was employ | adopted as a manufacturing method of olivine type lithium manganese iron phosphate, and the carbon-olivine type lithium manganese iron phosphate composite was manufactured. However, in Comparative Example 3, as the carbon component, Comparative Example 1 used acetylene black and Comparative Example 2 used sucrose, whereas acetylene black and sucrose were used in combination, and carbon-olivine type phosphoric acid was used. Manganese iron lithium composites were produced.

Manganese phosphate trihydrate [Mn ₃ (PO ₄ ) ₂ .3H ₂ O], ferrous phosphate octahydrate [Fe ₃ (PO ₄ ) ₂ .8H ₂ O] and lithium phosphate ( Li ₃ PO ₄ ) is mixed so that the element ratio of lithium, manganese, and iron is 1: 0.8: 0.2, and sucrose: acetylene black = 11: 1 (mass ratio) It added so that the carbon content after baking might be set to 5.0 mass% by the compounding quantity, and it mixed for 10 hours using the planetary ball mill ["PM-100 (brand name) by Lecce" by a dry type. The obtained mixture was baked in a nitrogen stream at 700 ° C. for 5 hours, and the obtained baked product was pulverized by a simple cutter mill to obtain a composite.

When the obtained carbon-manganese iron phosphate lithium composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine-type lithium manganese iron phosphate composite was Li: Mn: Fe: P =. 1: 0.8: 0.2: 1, it is confirmed most of the crystalline component is olivine-type phosphate lithium manganese iron _LiMn 0.8 _Fe 0.2 PO _4, also, the carbon - It was confirmed that the olivine type lithium manganese iron phosphate composite contained 5.2% by mass of carbon.

Comparative Example 4
In this comparative example 4, it becomes a carbon precursor after the step of producing the coprecipitate containing the carbon-manganese iron phosphate complex and lithium phosphate of (2) and before the firing step of (4). Carbon-olivine type lithium manganese iron phosphate composite [acetylene black: olivine type lithium manganese iron phosphate = 20: 80 (mass ratio) carbon-olivine type lithium iron manganese phosphate without adding or mixing organic substances An example of producing the composite] is shown.

[Production of carbon-manganese iron phosphate composite]
650 cm ³ of ion-exchanged water was put into a 2 L separable flask, and 4.0 g of nonionic surfactant (“Emulgen MS-110 (trade name)” manufactured by Kao Corporation) was added, followed by acetylene black powder [Electrochemical Industry Co., Ltd. “Denka Black (trade name)”, particle size 35 nm] 28.1 g was added and stirred for 15 minutes to obtain a carbon black dispersion. Thereafter, an aqueous solution prepared by previously dissolving 53.1 g of 85% phosphoric acid, 133.3 g of manganese sulfate pentahydrate and 38.4 g of ferrous sulfate heptahydrate in 430 cm ³ of ion-exchanged water was used. Added to the black dispersion and stirred for 10 minutes. Further, 184.3 g of 30% aqueous sodium hydroxide solution was added to the carbon black dispersion, and the mixture was stirred for 15 minutes and filtered to obtain a carbon-manganese iron phosphate composite.

[Production of carbon-manganese iron phosphate-lithium phosphate coprecipitate]
Carbon obtained by adding 650 cm ³ of ion-exchanged water to a 2 L separable flask and adding 4.0 g of a nonionic surfactant (“Emulgen MS-110 (trade name)” manufactured by Kao Corporation), as described above. -The total amount of manganese iron phosphate composites was added and stirred for 15 minutes to obtain a carbon-manganese iron phosphate composite dispersion. Thereafter, 25.6 g of 85% phosphoric acid was added to the carbon-manganese iron phosphate complex dispersion, and an aqueous solution in which 29.0 g of lithium hydroxide monohydrate was previously dissolved in 165 cm ³ of ion-exchanged water. Was added and stirred for 10 minutes, followed by filtration to obtain a carbon-manganese iron phosphate-lithium phosphate coprecipitate.

[Baking]
The coprecipitate obtained as described above was dried in a vacuum dryer at 40 ° C. for 24 hours. The dried coprecipitate was fired in a nitrogen stream at 600 ° C. for 5 hours, and then pulverized by a simple cutter mill to obtain a carbon-olivine-type lithium manganese iron phosphate composite. .

The carbon-olivine type manganese iron phosphate lithium composite obtained as described above was analyzed in the same manner as in Example 1. As a result, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li. : Mn: Fe: P = 1 : 0.8: 0.2: 1, confirmed that the majority of the crystalline component is olivine-type phosphate lithium manganese iron _LiMn 0.8 _Fe 0.2 PO ₄ In addition, it was confirmed that the carbon content in the carbon-olivine type lithium manganese iron phosphate composite was 20.2% by mass.

Comparative Example 5
In this comparative example 5, in place of the acetylene black: olivine type lithium manganese iron phosphate = 20: 80 (mass ratio) carbon-manganese iron iron phosphate composite in the comparative example 4, the acetylene was used. A carbon-lithium manganese iron phosphate composite of black: olivine type lithium manganese iron phosphate = 5: 95 (mass ratio) was produced.

[Production of carbon-manganese phosphate composite]
650 cm ³ of ion-exchanged water was put into a 2 L separable flask, 1.3 g of nonionic surfactant [“Emulgen MS-110 (trade name)” manufactured by Kao Corporation] was added, and acetylene black powder [Electrochemical Industry Co., Ltd. “Denka Black (trade name)”, particle size 35 nm] 6.3 g was added and stirred for 15 minutes to obtain a carbon black dispersion. Thereafter, an aqueous solution prepared by previously dissolving 53.1 g of 85% phosphoric acid, 133.3 g of manganese sulfate pentahydrate and 38.4 g of ferrous sulfate heptahydrate in 430 cm ³ of ion-exchanged water was used. Added to the black dispersion and stirred for 10 minutes. Further, 156.7 g of a 15% aqueous ammonia solution was added to the carbon black dispersion, and the mixture was stirred for 15 minutes and then filtered to obtain a carbon-manganese iron phosphate composite.

[Production of carbon-manganese phosphate-lithium phosphate coprecipitate]
Carbon obtained by adding 650 cm ³ of ion-exchanged water to a 2 L separable flask and adding 1.3 g of a nonionic surfactant [“Emulgen MS-110 (trade name)” manufactured by Kao Corporation], as described above. -The total amount of manganese iron phosphate composites was added and stirred for 15 minutes to obtain a carbon-manganese iron phosphate composite dispersion. Thereafter, 25.6 g of 85% phosphoric acid was added to the carbon-manganese iron phosphate complex dispersion, and an aqueous solution in which 29.0 g of lithium hydroxide monohydrate was previously dissolved in 165 cm ³ of ion-exchanged water. Was added and stirred for 10 minutes, followed by filtration to obtain a carbon-manganese iron phosphate-lithium phosphate coprecipitate.

[Baking]
The coprecipitate obtained as described above was dried in a vacuum dryer at 40 ° C. for 24 hours. The dried coprecipitate was baked in a nitrogen stream at 700 ° C. for 5 hours, and then pulverized by a simple cutter mill to obtain a carbon-olivine type lithium manganese iron phosphate composite. .

When the carbon-olivine type manganese iron phosphate lithium composite obtained as described above was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was as follows. li: Mn: Fe: P = 1: 0.8: 0.2: 1, that most of the crystalline component is olivine-type phosphate lithium manganese iron _LiMn 0.8 _Fe 0.2 PO ₄ It was confirmed that the carbon content in the carbon-olivine type lithium manganese iron phosphate composite was 5.2% by mass.

Comparative Example 6
In Comparative Example 6, manganese iron phosphate was synthesized in the first step without synthesizing the carbon-manganese iron phosphate complex as in step (1) in the present invention, and thereafter the same as in the present invention. A carbon-olivine type lithium manganese iron phosphate composite was produced.

[Manufacture of manganese iron phosphate]
Into a ² L separable flask, 540 cm ³ of ion-exchanged water was added, and 76.9 g of 85% phosphoric acid, 192.8 g of manganese sulfate pentahydrate, and 55.6 g of ferrous sulfate heptahydrate were dissolved. Further, 227.1 g of a 15% aqueous ammonia solution was added, stirred for 15 minutes and then filtered to obtain manganese iron phosphate.

[Production of manganese iron phosphate and lithium phosphate coprecipitate]
Into a 2 L separable flask, 615 cm ³ of ion-exchanged water was added, and the total amount of manganese iron phosphate obtained above was added and stirred for 15 minutes to obtain a manganese iron phosphate dispersion. Thereafter, 38.4 g of 85% phosphoric acid was added, an aqueous solution in which 41.9 g of lithium hydroxide monohydrate was previously dissolved in 380 cm ³ of ion-exchanged water was added, and the mixture was stirred for 10 minutes. A lithium phosphate coprecipitate slurry was prepared.

[Addition of organic substance as carbon precursor]
A 40% aqueous solution in which 34.6 g of sucrose was dissolved in ion-exchanged water was added to the slurry of manganese iron phosphate-lithium phosphate coprecipitate obtained as described above, and the mixture was stirred for 10 minutes and mixed. A slurry was obtained.

[Baking]
The slurry liquid of the mixture of manganese iron phosphate, lithium phosphate coprecipitate and sucrose obtained as described above was used as a horizontal sand mill ("Dino Mill MULTI LAB type (trade name)" manufactured by Willy et Bacofen). And filled with 0.5 mm diameter zirconia beads and wet pulverized. The obtained slurry was dried at 70 ° C. under reduced pressure, and the obtained dried product was pulverized by rotating for 72 hours using a 1 L nylon pot containing 2 cm diameter zirconia balls. After pulverization, firing was performed in a nitrogen stream at 700 ° C. for 5 hours to obtain an olivine-type lithium manganese iron phosphate composite.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component was Li: Mn: Fe: P = 1: 0.8: 0. 2: 1, and it was confirmed that the crystalline component was olivine-type lithium manganese iron phosphate LiMnPO ₄ , and the carbon content in the carbon-olivine-type lithium manganese iron phosphate composite was 5.1% by mass. It was confirmed that it was included.

[Evaluation-1 as cathode material of lithium ion battery]
A lithium ion battery having a positive electrode using the carbon-olivine type lithium iron phosphate composites obtained in Examples 1 to 5 and Comparative Examples 1 to 6 as a positive electrode material was prepared, the discharge capacity was measured, and the carbon -The olivine type lithium iron phosphate composite was evaluated as a positive electrode material. The details are as follows.

  20 mg each of the carbon-olivine type lithium iron phosphate composites obtained in Examples 1 to 5 and Comparative Examples 1 to 6 and polytetrafluoroethylene as a binder ["Teflon (registered trademark) 6" manufactured by DuPont -J "] 2 mg was kneaded in a mortar, formed into a film of about 1 cm square, placed on a nickel wire mesh, and pressurized for 5 minutes at a pressure of 1 ton to produce a working electrode (positive electrode).

In a glove box substituted with argon, two metal lithium foils pressed against a nickel wire mesh were fixed, and these were used as a counter electrode and a reference electrode. 30 ml of electrolytic solution (propylene carbonate solution in which LiClO ₄ was dissolved at a concentration of 1 mol / l) was placed in a beaker type triode cell, and the above working electrode, counter electrode and reference electrode were attached, and a test cell (lithium ion battery) Configured.

About the cell for the said test, the charging / discharging test was done using the battery charging / discharging apparatus [Hokuto Denko "HJ-1001SM8 (brand name)". The test was performed at a current density of 17 mA / g with respect to Li (Mn _0.8 Fe _0.2 ) PO ₄ , setting the upper limit of the voltage to 4.3 V, and the lower limit to 2.5 V. The discharge capacity (mAh / g) and energy density (mWh / g) per 1 g of a certain olivine type lithium iron manganese phosphate were calculated. The results are also shown in Table 1.

  As shown in Table 1, when the carbon-olivine type manganese iron phosphate lithium composites of Examples 1-5 were used as the positive electrode material, the carbon-olivine type manganese iron lithium phosphate composites of Comparative Examples 1-6 were used. Compared to the case of using as a positive electrode material, the discharge capacity is large and the energy density is high, and the carbon-olivine type manganese iron lithium phosphate composites of Examples 1 to 5 are high as the positive electrode material of a lithium ion battery. It was clear that the energy density could be achieved.

  In contrast, the carbon-olivine type lithium iron phosphate composite of Comparative Example 1 had a small discharge capacity and a low energy density because Comparative Example 1 employs a solid-phase method. It is considered that uniform mixing could not be performed, and therefore, the reaction between manganese iron phosphate and lithium phosphate at the time of firing and the complexation with carbon were not sufficiently performed.

  Moreover, the carbon-olivine type manganese iron phosphate composite of Comparative Example 2 using sucrose as a carbon precursor as the carbon component, and the carbon-olivine type of Comparative Example 3 using acetylene black and sucrose as the carbon component in combination. The lithium iron manganese phosphate composite also had a small discharge capacity and a low energy density because, in Comparative Examples 2 to 3, the solid phase method was adopted as in Comparative Example 1, It is considered that uniform mixing could not be performed, and therefore, the reaction between manganese iron phosphate and lithium phosphate at the time of firing and the complexation with carbon were not sufficiently performed.

  And, after the step of producing the coprecipitate containing the carbon-manganese iron phosphate complex and lithium phosphate of (2), before the firing step of (4), addition of an organic substance that becomes a carbon precursor, Without mixing, the produced carbon-olivine-type lithium manganese iron phosphate composite of Comparative Example 4 and the carbon-olivine-type lithium manganese iron phosphate composite of Comparative Example 5 were small in discharge capacity and low in energy density. This is presumably because the organic substance serving as a carbon precursor does not exist, so that a carbon network with acetylene black cannot be formed, and therefore sufficient electron conductivity cannot be obtained.

  Moreover, the discharge capacity of the carbon-olivine-type manganese iron phosphate lithium composite of Comparative Example 6 was small and the energy density was low without producing the carbon-manganese iron phosphate composite in the first step. This is probably because, since iron manganese oxide was synthesized, a carbon network was not formed even though sucrose was added and baked, so that sufficient electron conductivity could not be obtained.

Example 6
Instead of 192.8 g manganese sulphate pentahydrate and 55.6 g ferrous sulfate heptahydrate in Example 1, 204.9 g manganese sulphate pentahydrate and ferrous sulfate heptahydrate Except having used 41.7g of thing, it operated on the same conditions as Example 1, and obtained the carbon- olivine type lithium manganese iron phosphate composite.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.85: 0.15: 1, the crystalline component, it is confirmed as olivine-type phosphate lithium manganese iron _LiMn 0.85 _{Fe 0.15} PO _4, also, the carbon - olivine It was confirmed that 5.1 mass% of carbon was contained in the type lithium manganese phosphate complex.

Example 7
Instead of 192.8 g manganese sulphate pentahydrate and 55.6 g ferrous sulfate heptahydrate in Example 1, 180.8 g manganese sulphate pentahydrate and ferrous sulphate heptahydrate Except having used 69.5g of thing, it operated on the conditions similar to Example 1, and obtained the carbon- olivine type lithium manganese iron phosphate composite.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.75: 0.25: 1, and it was confirmed that the crystalline component was olivine-type lithium manganese iron phosphate LiMn _0.75 Fe _0.25 PO ₄ , and the above carbon-olivine It was confirmed that 5.2% by mass of carbon was contained in the type lithium manganese iron phosphate composite.

Example 8
Instead of 192.8 g manganese sulphate pentahydrate and 55.6 g ferrous sulfate heptahydrate in Example 1, 168.7 g manganese sulphate pentahydrate and ferrous sulphate heptahydrate The carbon-olivine type lithium manganese iron phosphate composite was obtained by operating under the same conditions as in Example 1 except that 83.4 g of the product was used.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.7: 0.3: 1, the crystalline component was confirmed to be olivine-type lithium iron manganese phosphate LiMn _0.7 Fe _0.3 PO ₄ , and the carbon-olivine The carbon content in the lithium manganese iron phosphate composite was confirmed to be 5.2% by mass.

Example 9
Instead of 192.8 g manganese sulphate pentahydrate and 55.6 g ferrous sulfate heptahydrate in Example 1, 216.9 g manganese sulphate pentahydrate and ferrous sulphate heptahydrate Except having used 27.8g of thing, it operated on the conditions similar to Example 1, and obtained the carbon- olivine type lithium manganese iron phosphate composite.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.9: 0.1: 1 and the crystalline component was confirmed to be olivine-type lithium iron manganese phosphate LiMn _0.9 Fe _0.1 PO ₄ , and the carbon-olivine The carbon content in the lithium manganese iron phosphate composite was confirmed to be 5.2% by mass.

Comparative Example 7
Instead of 192.8 g of manganese sulfate pentahydrate and 55.6 g of ferrous sulfate heptahydrate in Example 1, 229.0 g of manganese sulfate pentahydrate and ferrous sulfate heptahydrate Except having used 13.9g of thing, it operated on the same conditions as Example 1, and obtained the carbon-olivine type lithium manganese iron phosphate composite.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.95: 0.05: 1, the crystalline component was confirmed to be olivine-type lithium iron manganese phosphate LiMn _0.95 Fe _0.05 PO ₄ , and the carbon-olivine It was confirmed that 5.1 mass% of carbon was contained in the type lithium manganese phosphate complex.

Comparative Example 8
Instead of 192.8 g manganese sulphate pentahydrate and 55.6 g ferrous sulfate heptahydrate in Example 1, 156.7 g manganese sulphate pentahydrate and ferrous sulphate heptahydrate Except having used 97.3g of thing, it operated on the same conditions as Example 1, and obtained the carbon-olivine type manganese iron phosphate lithium composite_body | complex.

When the obtained carbon-olivine type lithium manganese iron phosphate composite was analyzed in the same manner as in Example 1, the molar ratio of each component of the carbon-olivine type lithium manganese iron phosphate composite was Li: Mn: Fe: P = 1: 0.65: 0.35: 1, the crystalline component, it is confirmed as olivine-type phosphate lithium manganese iron _LiMn 0.65 _{Fe 0.35} PO _4, also, the carbon - olivine It was confirmed that 5.2% by mass of carbon was contained in the type lithium manganese iron phosphate composite.

[Evaluation-2 as positive electrode material of lithium ion battery]
A test cell (lithium ion battery) similar to that of Example 1 was prepared using the carbon-olivine type lithium manganese iron phosphate composites obtained in Examples 6 to 9 and Comparative Examples 7 to 8 as the positive electrode material, For these test cells, the discharge capacity and energy density per gram of lithium olivine-type manganese iron phosphate were determined in the same manner as in Example 1. The results are shown in Table 2. In addition, although X value is shown in Table 2, this is a value of X of olivine type lithium manganese iron phosphate Li (Mn _1-x Fe _x ) PO ₄ .

  As shown in Table 2, Examples 6 to 9 having an X value [ratio of iron (Fe) to manganese (Mn)] in the range of 0.1 to 0.3 have an X value of 0.1 to 0. Compared to Comparative Examples 7 to 8 outside the range of .3, the energy density was high.

Claims (14)

The composition of the olivine type lithium manganese iron phosphate portion in the carbon-olivine type lithium manganese iron phosphate composite is represented by the following general formula (1):
Li (Mn _1-x Fe _x ) PO ₄ (1)
(Where X = 0.1 to 0.3)
A method for producing a carbon-olivine type lithium manganese iron phosphate composite represented by:
(1) a step of producing a carbon-manganese iron phosphate composite by precipitation;
(2) a step of producing a coprecipitate containing the carbon-manganese iron phosphate complex and lithium phosphate;
(3) A step of adding and mixing an organic substance to be a carbon precursor to the coprecipitate,
(4) A step of firing a mixture of the coprecipitate and an organic substance that becomes a carbon precursor,
A method for producing a carbon-olivine-type lithium manganese iron phosphate composite characterized by comprising:   The manufacturing method according to claim 1, wherein the mixture of the coprecipitate and the organic substance to be the carbon precursor is pulverized and dispersed by a wet media pulverizer between the step (3) and the step (4). . The composition of the olivine-type manganese iron phosphate portion in the carbon-olivine-type manganese iron phosphate lithium composite has the following general formula (1):
Li (Mn _1-x Fe _x ) PO ₄ (1)
(Where X = 0.1 to 0.3)
A method for producing a carbon-olivine type lithium manganese iron phosphate composite represented by:
(1) a step of producing a carbon-manganese iron phosphate composite by precipitation;
(2) a step of producing a coprecipitate containing the carbon-manganese iron phosphate complex and lithium phosphate, drying the coprecipitate, and calcining;
(3) A step of adding and mixing an organic substance that becomes a carbon precursor to the co-precipitate calcined product,
(4) A step of firing a mixture of the co-precipitate calcined product and an organic material to be a carbon precursor,
A method for producing a carbon-olivine-type lithium manganese iron phosphate composite characterized by comprising:   The mixture of the calcined product of the coprecipitate and the organic material to be a carbon precursor is pulverized and dispersed by a wet media pulverizer between the step (3) and the step (4). Manufacturing method.   In the step (2), the carbon-manganese iron phosphate complex obtained in the step (1) is dispersed in water, phosphoric acid is added to the water, and a lithium compound-containing aqueous solution is further added. The manufacturing method of Claim 1 or 3 which obtains the coprecipitate containing a carbon-manganese iron phosphate complex and lithium phosphate by adding.   In the step (2), the carbon-manganese iron phosphate composite obtained in the step (1) is mixed with water in which phosphoric acid and a lithium compound-containing aqueous solution are mixed to form a lithium phosphate precipitate. The production method according to claim 1 or 3, wherein a coprecipitate containing a carbon-manganese iron phosphate complex and lithium phosphate is obtained by adding and dispersing.   The manufacturing method according to claim 6, wherein phosphoric acid and an aqueous solution containing a lithium compound are mixed in water in which a carbon material is dispersed, and the carbon-manganese iron phosphate composite obtained in the step (1) is further added. .   In the step (1), an aqueous solution containing a compound containing phosphoric acid and divalent manganese and a compound containing divalent iron is added to water in which the carbon material is dispersed, and then a water-soluble base is added. The manufacturing method in any one of Claims 1-7 which obtains a carbon-manganese iron phosphate composite precipitate by neutralizing with.   The manufacturing method according to claim 1 or 3, wherein in the step (3), the organic substance serving as the carbon precursor added to the coprecipitate is a saccharide.   The production method according to claim 9, wherein the saccharide is a monosaccharide or a disaccharide.   The manufacturing method according to any one of claims 1 to 10, wherein in the step (4), the firing temperature is 500 to 900 ° C.   The carbon content in the carbon-olivine type lithium manganese iron phosphate composite obtained through the steps (1), (2), (3) and (4) is 0.1 to 25% by mass. The manufacturing method in any one of claim | item 1 -11.   It consists of a carbon-olivine type lithium iron phosphate composite obtained by the manufacturing method in any one of Claims 1-12, The positive electrode material for lithium ion batteries characterized by the above-mentioned.   A carbon-olivine type manganese iron lithium phosphate composite obtained by the production method according to claim 1 and a carbon material other than carbon derived from the carbon-olivine type lithium manganese iron phosphate composite. The positive electrode material for lithium ion batteries characterized by containing 0.1-15 mass%.