JP2007250417A - Electrode material, its manufacturing method and lithium ion battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode material composed of an element which is of low cost and is available abundantly in natural resources and can obtain a high discharging capacity, stable charge/discharge cycle characteristics, a high filling property, a high output, and excellent low temperature load characteristics or the like, and provide its manufacturing method and a lithium ion battery. <P>SOLUTION: The electrode material is composed of a combination of a plurality of primary particles 1 composed of Li<SB>x</SB>A<SB>y</SB>D<SB>z</SB>PO<SB>4</SB>(wherein, A for one or two kinds selected from a group of Cr, Mn, Fe, Co, Ni and Cu, D for one or two kinds selected from a group of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y and rare earth elements, and 0≪x≪2, 0≪y≪1.5, 0≤z≪1.5), and each of these primary particles 1 is jointed with carbon 2 formed by the thermal decomposition of reducing sugar of a third dimensional net shape to form secondary particles 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode material, a method for producing the same, and a lithium ion battery, and in particular, a positive electrode material for a non-aqueous electrolyte secondary battery, particularly an electrode material suitable for use as a positive electrode material for a lithium ion battery, and this The present invention relates to a method for producing an electrode material, and a lithium ion battery using the electrode material.

In recent years, non-aqueous electrolyte secondary batteries such as lithium ion batteries have been proposed and put into practical use as batteries that are expected to be reduced in size, weight, and capacity.
This lithium ion battery uses a positive electrode active material such as lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ) as a positive electrode material, and has a small electromotive force. There is an excellent feature of exceeding 4V.
On the other hand, Fe, which is abundant in resources and inexpensive, has attracted attention as a positive electrode material for lithium ion batteries. For example, since the phosphoric acid compound represented by LiFePO ₄ has a potential of about 3.3 V with respect to the metal Li, it can be used as a chargeable / dischargeable positive electrode material (see, for example, Non-Patent Document 1). ).
In recent years, phosphates containing transition metals other than Fe and lithium, such as LiMnPO4 and LiCoPO4, have attracted attention. These phosphates have a high operating potential and are excellent in stability at high temperatures.
A. K. Paddy et al., J. Electrochem. Soc. Vol. 144, p. 1609 (1997)

However, the conventional lithium ion battery has various problems in the positive electrode material used.
For example, LiCoO ₂ has a problem that Co itself is toxic in addition to the problem that it is expensive because the amount of Co reserve is small and the price is easily affected by market conditions.
In addition, LiNiO ₂ has excellent charge / discharge characteristics, but is never cheap, and has problems such as a decrease in stability at high temperatures and a rapid decrease in characteristics due to a composition shift from a constant ratio.
In addition, LiMn ₂ O ₄ has a problem that Mn is eluted at a high temperature, a problem of cycle deterioration due to a Mn ³⁺ yarn-teller strain, and the like.

On the other hand, although LiFePO ₄ has an excellent point that there is no problem of toxicity to the human body and the environment, it has a problem that it is still insufficient in terms of electromotive force and high capacity compared to lithium compounds such as LiCoO _2. there were. In addition, since the conductivity of the material itself is low, there is a problem that the internal resistance of the battery is large and it is difficult to increase the output. In addition, since it is a compound containing Fe (II), it is easily oxidized. Therefore, it is necessary to synthesize in a non-oxidizing atmosphere such as Ar or N ₂ or a reducing atmosphere containing H ₂ .
Further, phosphates containing transition metals other than Fe and lithium, which have been attracting attention in recent years, have a problem of low conductivity, like LiFePO ₄ and the like. These phosphates are harder to oxidize than Fe, but in an oxidizing atmosphere, an inert phase composed of oxides is formed on the surface. Therefore, the capacity and the reactivity are apt to decrease. On the other hand, it is not stable.

  The present invention has been made to solve the above-described problems, and uses inexpensive and resource-rich elements, and has a high discharge capacity, stable charge / discharge cycle performance, high fillability, high output, and good quality. An object of the present invention is to provide an electrode material capable of realizing low-temperature load characteristics and the like, a manufacturing method thereof, and a lithium ion battery.

The reason why the present inventors have completed the present invention will be described.
The present inventors have already assembled a plurality of primary particles made of lithium compounds into secondary particles, and interposing an electron conductive material such as carbon between these primary particles, It has been found that a particulate composite cathode material having excellent conductivity can be obtained. As a result of further studies in order to easily synthesize such a particulate composite cathode material, a lithium compound is formed. Li, A selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu, or two or more, and Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In Li _x A _y by spraying and heating a solution containing one or more selected from the group consisting of Si, Ge, Sc, Y and rare earth elements, P, and reducing sugar A plurality of primary particles composed of D _z PO ₄ It has been found that a particulate composite electrode material can be easily synthesized with secondary particles and these primary particles joined via carbon generated by thermal decomposition of reducing sugar as an electron conductive substance.

In general, when a Li compound such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFe _1-x M _x PO ₄ (M is any one of Co, Mn, and Ni) is used as a positive electrode material of a lithium ion battery. In charging the battery, Li ions are desorbed from the positive electrode material, and conversely, Li ions are added to the positive electrode material during discharging. The desorption and addition of Li ions occur on the surface of the positive electrode material, but at the same time, reduction and oxidation of transition metal ions such as Co, Ni, Mn, and Fe occur inside the positive electrode material.
That is, at the reaction point on the surface of the positive electrode material, the presence of the positive electrode material, Li ions from the electrolyte, and electrons must be present, but in the conventional lithium ion battery, the material itself has low electronic conductivity, and the electron This is one of the factors that hinder high output. Therefore, if the ability to supply electrons can be increased by containing a substance having electronic conductivity in the positive electrode material, the output of the battery can be increased.

In particular, in the case of a LiFe _1-x M _x PO ₄ system material, since the electronic conductivity of the material itself is low, it is possible to improve the electron supply capability by containing a substance having electronic conductivity inside, that is, the high battery performance. The output effect is extremely high.
Fe is an inexpensive raw material, but is very easily oxidized. For this reason, special attention must be paid to the quality of raw materials, storage methods, and the synthesis atmosphere, and the resulting increase in cost is a problem. However, a solution containing elements constituting lithium compounds and reducing sugars such as glucose is sprayed. By heating, the problem of oxidation of Fe can be greatly relieved. This prevention of Fe oxidation is particularly effective in the case of LiFe _1-x M _x PO ₄ -based materials.
The present invention has been made based on the above idea.

That is, the electrode material of the present invention is Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Cr, Mn, Fe, Co, Ni, Cu, D is Mg, One or more selected from the group consisting of Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y and rare earth elements, 0 <x <2, 0 <y <1.5, 0 ≦ z <1.5), a plurality of primary particles are aggregated to form secondary particles, and these primary particles are joined via carbon generated by thermal decomposition of reducing sugar. It is characterized by.

  The carbon content is preferably 0.1% by weight or more and 30% by weight or less.

The manufacturing method of the electrode material of the present invention is Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Cr, Mn, Fe, Co, Ni, Cu, and D is Mg , Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, one or more selected from the group of rare earth elements, 0 <x <2, 0 < A plurality of primary particles composed of y <1.5 and 0 ≦ z <1.5) are assembled into secondary particles, and these primary particles are joined via carbon generated by thermal decomposition of reducing sugar. And a Li component, an A component (where A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu), and D Component (However, D is Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y With one or more members selected from the group of rare earth elements), and sprayed with P component, the solution or suspension containing a reducing sugar, characterized by heating.

The component A is preferably Fe.
The reducing sugar is preferably one or more selected from the group consisting of glucose, fructose, maltose and lactose.
The content of the reducing sugar in the solution or suspension is preferably 0.2% by weight or more and 70% by weight or less with respect to the Li _x A _y D _z PO ₄ .

  The lithium ion battery of the present invention includes a positive electrode using the electrode material of the present invention.

According to the electrode material of the present invention, Li _x A _y D _z PO ₄ (where A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu, D is Mg, One or more selected from the group consisting of Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y and rare earth elements, 0 <x <2, 0 <y <1.5, 0 ≦ z <1.5), a plurality of primary particles are assembled into secondary particles, and these primary particles are joined via carbon generated by thermal decomposition of reducing sugar. Therefore, there is no possibility that an inert phase made of an oxide is generated on the surface of the primary particles, and a decrease in capacity and a decrease in reactivity can be prevented. Therefore, the discharge capacity can be increased, and the charge / discharge cycle performance can be stabilized. In addition, high output and good low temperature load characteristics can be realized.

  According to the method for producing an electrode material of the present invention, Li, one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu, Mg, Ca, Sr, and Ba , Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, a solution containing one or more selected from the group of rare earth elements, P, and a reducing sugar, or Since the suspension is sprayed and heated, it is possible to prevent the reducing sugar from forming an inactive phase composed of an oxide on the surface of the primary particles in the process of generating carbon by thermal decomposition of the reducing sugar. . Therefore, an electrode material capable of realizing high discharge capacity, stable charge / discharge cycle performance, high filling property, high output, and good low-temperature load characteristics can be easily produced at low cost.

  According to the lithium ion battery of the present invention, since the positive electrode using the electrode material of the present invention is provided, the discharge capacity of the positive electrode using this electrode can be increased, and the charge / discharge cycle performance can be stabilized. Can do. Therefore, it is possible to provide a lithium ion battery capable of realizing high discharge capacity, stable charge / discharge cycle performance, high filling property, high output, and good low-temperature load characteristics.

The best mode for carrying out the electrode material of the present invention, the manufacturing method thereof and the lithium ion battery will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

The electrode material of this embodiment is Li _x A _y D _z PO ₄ (where A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu, and D is Mg, Ca , Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, one or more selected from the group of rare earth elements, 0 <x <2, 0 <y < A plurality of primary particles composed of 1.5, 0 ≦ z <1.5) are formed into secondary particles, and these primary particles are produced by thermal decomposition of reducing sugar, which is an electronically conductive substance. It is the electrode material formed by joining via.
Here, the rare earth elements are 15 elements of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu which are lanthanum series.

In this electrode material, a plurality of primary particles made of Li _x A _y D _z PO ₄ coated with carbon generated by thermal decomposition of reducing sugar, which is an electron conductive substance, are aggregated to form secondary particles. It is preferable that the portion of the primary particles constituting the secondary particles that are exposed to the outside are also covered with carbon generated by thermal decomposition of the reducing sugar.
Here, “bonding” means that the primary particles are not simply agglomerated to form secondary particles, but are firmly bonded so that the secondary particles behave as one particle. . In the secondary particles, it is preferable that the carbon generated by the thermal decomposition of the reducing sugar, which is an electron conductive substance, has a three-dimensional network shape.

FIG. 1 is a cross-sectional view showing the cross-sectional shape of the electrode material of the present invention, in which a plurality of primary particles 1 made of Li _x A _y D _z PO ₄ are assembled, and these primary particles 1, 1,. Are joined by carbon 2 generated by thermal decomposition of reducing sugar, which is a thin-layered electronically conductive substance having a three-dimensional network shape, to form secondary particles 3. The overall shape of the secondary particles 3 can be various shapes such as a spherical shape having irregularities on the surface, a polygonal shape, etc., in addition to a substantially spherical shape having irregularities on the surface as shown in FIG.

  For A, one or more selected from the group consisting of Mn, Fe, Co, and Ni, and for D, selected from the group consisting of Mg, Ca, Sr, Ti, Zn, and Al. 1 type or 2 types or more are preferable from points, such as a high discharge potential, abundant resource amount, and safety | security.

Moreover, since the molecular structure of the reducing sugar is cyclic, it is easily carbonized by thermal decomposition, and it is possible to prevent oxidation of the metal element by exhibiting reducing properties in the thermal decomposition process. This reducing sugar generates carbon by thermal decomposition, and this carbon is preferable in terms of chemical stability, safety and cost.
The reducing sugar is preferably a monosaccharide or oligosaccharide having reducibility, and particularly preferably one or two or more kinds selected from the group of glucose, fructose, maltose and lactose. Among these, glucose is more preferable because it is excellent in reducing ability, solubility, price, and the like.

Here, the average particle diameter of the primary particles is preferably 0.001 μm or more and 20 μm or less, more preferably 0.05 μm or more and 2 μm or less.
The reason is that if the average particle size is smaller than 0.001 μm, the crystal structure may be destroyed due to the volume change due to charge / discharge, and if the average particle size is larger than 20 μm, the electrons inside the particles may be destroyed. This is because there is a shortage of supply amount and the utilization efficiency is lowered.

Further, the thickness of carbon is preferably 0.001 μm or more and 1 μm or less, more preferably 0.01 μm or more and 0.2 μm or less.
The reason is that if the thickness is less than 0.001 μm, the electron conductivity is not sufficient, and the amount of electrons supplied is insufficient. If the thickness is more than 1 μm, the ratio of the active material in the electrode material is small. This is because the active material is hardly used effectively.

The average particle size of the secondary particles is preferably 0.01 μm or more and 200 μm or less, more preferably 0.1 μm or more and 50 μm or less.
The reason is that if the average particle size is smaller than 0.01 μm, a large amount of binder is required in preparing the electrode material mixture, and as a result, the ratio of the active material in the electrode material mixture decreases, and the electrode This is because the conductivity of the material mixture also decreases, and if the average particle size is larger than 200 μm, voids are likely to occur in the electrode material mixture, resulting in a decrease in discharge capacity and charge / discharge cycle performance. This is because it may become unstable.
The shape of the secondary particles is preferably spherical. This is because the spherical shape facilitates closest packing, increases the amount of positive electrode material per unit volume, and can reduce the battery volume even with the same capacity.

The carbon content in the secondary particles is preferably 0.1 wt% or more and 30 wt% or less, more preferably 1 wt% or more and 20 wt% or less.
The reason is that if the carbon content is less than 0.1% by weight, the electronic conductivity may not be sufficiently developed, and if it is more than 30% by weight, the carbon is contained in an amount greater than the amount necessary to obtain the necessary conductivity. This is because the weight and volume density of the positive electrode active material in the particles are reduced.

The carbon in the secondary particles exists as a simple carbon and does not form a compound with other components. The carbon is Li _x A _y D _z PO ₄ (where A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu, and D is Mg, Ca, Sr). , Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, one or more selected from the group of rare earth elements, 0 <x <2, 0 <y <1. 5, 0 ≦ z <1.5) existing outside the primary particles, and the primary particles composed of Li _x A _y D _z PO ₄ and a simple mixture of carbon and Are very different.

The carbon is preferably dispersed uniformly in the secondary particles, and is preferably present in a network form between the primary particles.
If this electrode material is used as a positive electrode material of a lithium ion battery, the obtained lithium ion battery has a high discharge capacity, a stable charge / discharge cycle performance, a high filling property, a high output, and the like.

The electrode material manufacturing method of the present embodiment includes a Li component, an A component (where A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu), and a D component. (Wherein D is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements); This is a method of spraying and heating a solution or suspension containing a P component and a reducing sugar.
About said D component, it shall add as needed.
In this method, since the solution or suspension that has become spherical droplets by spraying is heated, spherical particles having excellent filling properties can be easily obtained.

Here, the manufacturing method of this electrode material is demonstrated in detail.
Examples of the Li component include lithium chloride (LiCl), lithium bromide (LiBr), lithium carbonate (Li ₂ CO ₃ ), lithium nitrate (LiNO ₃ ), lithium sulfate (Li ₂ SO ₄ ), and lithium phosphate (Li ₃ PO ₄ ), lithium inorganic acid salts such as lithium hydroxide (LiOH), lithium organic acid salts such as lithium acetate (LiCH ₃ COO) and lithium oxalate ((COOLi) ₂ ), or lithium ethoxide (LiC ₂ H Li-containing organometallic compounds such as lithium alkoxides such as ₅ O), organic lithium compounds such as (Li ₄ (CH ₃ ) ₄ ), and the like can be used.

As the component A, a compound containing one or more elements selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu is preferable, and in particular, any one of Fe, Co, Mn, and Ni Or a compound containing two or more of these elements is preferred from the viewpoint of high discharge potential, abundant resource amount, safety, and the like.
As these compounds, for example, as a compound containing Fe, iron chloride (II) (FeCl ₂ ), iron bromide (II) (FeBr ₂ ), iron acetate (II) (Fe (CH ₃ COO) ₂ ) , Iron (II) sulfate (FeSO ₄ ), etc., Mn, Co, and Ni components such as manganese chloride (MnCl ₂ ), manganese acetate (Mn (CH ₃ COO) ₂ ), nickel chloride (NiCl ₂ ), etc. Can be used.

As the D component, one or more elements selected from the group of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, and rare earth elements are used. A compound containing Mg, Ca, Ti, Al and the like is particularly preferable from the viewpoint of high discharge potential, abundant resource amount, safety and the like.
As these compounds, for example, a salt such as aluminum chloride (AlCl ₃ ) can be used as a compound containing Al, and magnesium sulfate (MgSO ₄ ), magnesium acetate (Mg) as a compound containing Mg. A salt such as (CH ₃ COO) ₂ ) can be used, and as a compound containing Ti, a salt such as titanium sulfate (Ti (SO ₄ ) ₂ ) or titanium chloride (TiCl ₄ ) can be used. .
In particular, a compound containing Al, such as aluminum chloride (AlCl ₃ ), is preferable from the viewpoint of high discharge potential, abundant resources, safety, and the like.

Examples of the P component include phosphoric acid such as orthophosphoric acid (H ₃ PO ₄ ) and metaphosphoric acid (HPO ₃ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), and ammonium dihydrogen phosphate (NH ₄ An ammonium hydrogen phosphate salt such as H ₂ PO ₄ ) can be used.
Of these, orthophosphoric acid, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate are preferred because of their relatively high purity and ease of composition control.

As the reducing sugar, monosaccharide or oligosaccharide having reducibility can be used, and in particular, one or two or more kinds selected from the group of glucose, fructose, maltose, and lactose are preferable. Among them, glucose is reduced. It is preferable because of its excellent performance, solubility, and price.
By adding this reducing sugar, the oxidation of A component and D component can be suppressed, and the metal element contained in them can be reduced. Therefore, even if a low-grade raw material is used with the A component and the D component, a good positive electrode material can be obtained, and it is not necessary to pay much attention to the handling and storage state of the raw material, as in Fe (II) salt. Even raw materials that are easily oxidized can be handled and stored normally.
In particular, in order to obtain a uniform mixed raw material that does not cause reaction / aggregation before spraying, it is preferable to use chloride as the metal component and orthophosphoric acid (H ₃ PO ₄ ) as the P component.

These raw materials (Li component, A component, D component, P component and reducing sugar) are dissolved or dispersed in a solvent to form a uniform solution or suspension, and the solution or suspension is subjected to inert atmosphere or reduction. Spray and heat in a sexual atmosphere.
As this solvent, for example, water, alcohols, ketones, water-alcohol solutions, water-ketone solutions, water-ether solutions, and the like can be used, but water is preferable from the viewpoint of ease of use and safety.

The concentration of the raw material in this solution or suspension is not particularly limited as long as it can be sprayed, but is preferably 1% by weight or more and 30% by weight or less in order to obtain a good spray state. Further, the content of the reducing sugar in the solution or suspension may be an amount sufficient to suppress the oxidation of the A component and the D component and reduce the metal element contained in them. The content is preferably 0.2% by weight or more and 70% by weight or less based on the material, that is, Li _x A _y D _z PO ₄ .

  The particle diameter of the droplets during spraying is preferably 0.05 μm or more and 500 μm or less. Although the heating temperature at the time of spraying varies depending on the raw materials used, it is preferably 500 ° C. or higher and 1000 ° C. or lower, more preferably 650 ° C. or higher and 900 ° C. or lower. The reason for this is that if the heating temperature is lower than 500 ° C., the decomposition / reaction of the droplets does not proceed sufficiently, the crystallinity is lowered, and it may become amorphous. If the temperature is higher than 1000 ° C., the product melts and vitrifies, or a low-melting point metal such as Li evaporates, and the generated electrode material may cause a composition shift.

As an atmosphere for spraying and heating, an inert atmosphere such as N ₂ or Ar is preferable.
In this manufacturing method, since reducing sugar is added to the solution or suspension, the oxidation of the A component and D component is sufficiently suppressed in an inert atmosphere such as N ₂ and Ar, and the metal elements contained therein However, a reducing atmosphere containing a reducing gas such as H ₂ is preferable when it contains a metal that is easily oxidized.

In this production method, the raw materials of each component are sprayed as fine droplets in a state of being uniformly dispersed in a solution or suspension, and heated in that state, so a thermal decomposition reaction occurs instantaneously, Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Cr, Mn, Fe, Co, Ni, Cu, D is Mg, Ca, Sr, Ba, Ti, Zn) , B, Al, Ga, In, Si, Ge, Sc, Y, one or more selected from the group of rare earth elements, 0 <x <2, 0 <y <1.5, 0 ≦ z < The secondary particles formed by joining the primary particles made of the substance shown in 1.5) through carbon generated by the thermal decomposition of the reducing sugar, which is an electron conductive substance, are formed.

The reducing sugar that is uniformly dissolved in the solution or suspension is evenly distributed in the sprayed minute droplets, so when the secondary particles are generated from the primary particles, Incorporated in a state of being uniformly distributed in the secondary particles, carbon produced by thermal decomposition of the reducing sugar is interposed between the primary particles, and in a state where the carbon is interposed between the primary particles. Primary particles are bonded to each other.
At the same time, since the individual primary particles are also covered with carbon generated by the thermal decomposition of reducing sugar, the surfaces of the secondary particles bonded with the primary particles are also covered with carbon generated by the thermal decomposition of reducing sugar.
As described above, an electrode material capable of realizing high discharge capacity, stable charge / discharge cycle performance, high filling property, high output, and good low-temperature load characteristics can be easily produced at low cost.

  By applying this electrode material to the positive electrode of a lithium ion battery, it is possible to achieve a high discharge capacity, stable charge / discharge cycle performance, high fillability, high output, and good low-temperature load characteristics.

According to the electrode material of this embodiment, Li _x A _y D _z PO ₄ (where A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, and Cu, and D is Mg , Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, one or more selected from the group of rare earth elements, 0 <x <2, 0 < A plurality of primary particles composed of y <1.5 and 0 ≦ z <1.5) are assembled into secondary particles, and these primary particles are joined via carbon generated by thermal decomposition of reducing sugar. Therefore, high discharge capacity, stable charge / discharge cycle performance, high fillability, high output, good low-temperature load characteristics, etc. can be realized.

  According to the method for producing an electrode material of the present embodiment, a Li component, an A component (where A is one or more selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu), D component (where D is one or more selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y and rare earth elements) In addition, since the solution or suspension containing the P component and the reducing sugar is sprayed and heated, the reaction can proceed in the form of minute droplets, and the average particle diameter is in the range of 0.01 to 200 μm. Secondary particles can be produced easily and inexpensively, and spherical secondary particles can be produced easily and inexpensively.

In addition, since the raw material is prevented from being oxidized by the reducing action of the reducing sugar during spray pyrolysis, a good electrode material can be easily obtained even by using a raw material that is easily oxidized.
Further, during spray pyrolysis, primary particles are joined to each other through carbon generated by thermal decomposition of reducing sugar, which is an electron conductive substance, so that the primary particles are generated by thermal decomposition of reducing sugar. Carbon can be formed in a network. Therefore, secondary particles in which carbon is formed in a network shape between primary particles can be easily produced.

According to the lithium ion battery of the present embodiment, since the electrode material of the present embodiment is applied to the positive electrode, high discharge capacity, stable charge / discharge cycle performance, high fillability, high output, good low temperature load characteristics, etc. A lithium ion battery can be provided.
In addition, since the raw materials used are inexpensive and rich in resources, an inexpensive lithium ion battery can be provided.

EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-3 and Comparative Examples 1 and 2, this invention is not limited by these Examples.
For example, in this embodiment, metal Li is used for the negative electrode in order to reflect the behavior of the electrode material itself in the data. However, a negative electrode material such as a carbon material, a Li alloy, or Li ₄ Ti ₅ O ₁₂ may be used. . A solid electrolyte may be used instead of the electrolytic solution and the separator.

Example 1
LiCl, FeCl ₂ and H ₃ PO ₄ were dissolved in pure water so that their stoichiometric ratio was 1: 1: 1 and each concentration was 0.1 mol / kg to prepare an aqueous solution A. . Next, 1.8 g of glucose was added to 1000 g of the aqueous solution A and dissolved. At this time, the glucose content in the electrode material was 11.4% by weight.
Next, this solution is sprayed using an ultrasonic atomizer to form mist droplets, and the mist droplets are heat-treated at 700 ° C. using a mixed gas of O ₂ 1% -N ₂ 99% as a carrier gas. It was introduced into the furnace and pyrolyzed. Then, this pyrolyzate was collect | recovered and spherical electrode material powder A (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder A had a LiFePO ₄ / C ratio of 94.5 / 4.5 by weight.

(Example 2)
The FeCl _2, 80% relative humidity, oxidizing the 1 month left part of FeCl ₂ in the humidified air at room temperature (25 ° C.), forcibly alter the FeCl _2. Next, an aqueous solution B was prepared in the same manner as in Example 1 by using the modified FeCl ₂ . Next, 1.8 g of glucose was added to 1000 g of this aqueous solution B and dissolved. At this time, the glucose content in the electrode material was 11.4% by weight.
Next, this solution is sprayed using an ultrasonic atomizer to form mist droplets. The mist droplets are introduced into a heat treatment furnace at 700 ° C. using N ₂ gas as a carrier gas, and pyrolysis is performed. went. Then, this pyrolyzate was collect | recovered and spherical electrode material powder B (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder B had a LiFePO ₄ / C ratio of 95/5 by weight.

(Example 3)
To 1000 g of the aqueous solution A of Example 1, 1.8 g of fructose was added and dissolved. The content rate of fructose with respect to the electrode material at this time was 11.4 weight%.
Subsequently, spray pyrolysis of this solution was performed according to Example 1. Then, this pyrolyzate was collect | recovered and spherical electrode material powder C (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder C had a LiFePO ₄ / C ratio of 94.5 / 4.5 by weight.

Example 4
To 1000 g of the aqueous solution B of Example 2, 1.8 g of fructose was added and dissolved. The content rate of fructose with respect to the electrode material at this time was 11.4 weight%.
Subsequently, spray pyrolysis of this solution was performed according to Example 2. Then, this pyrolyzate was collect | recovered and spherical electrode material powder D (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder D had a LiFePO ₄ / C ratio of 95/5 by weight.

(Example 5)
1.7 g of maltose was added to 1000 g of the aqueous solution A of Example 1 and dissolved. The maltose content in the electrode material at this time was 10.8% by weight.
Subsequently, spray pyrolysis of this solution was performed according to Example 1. Then, this pyrolyzate was collect | recovered and spherical electrode material powder E (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder E had a LiFePO ₄ / C ratio of 94.5 / 4.5 by weight.

(Example 6)
1.7 g of maltose was added to 1000 g of the aqueous solution B of Example 2 and dissolved. The maltose content in the electrode material at this time was 10.8% by weight.
Subsequently, spray pyrolysis of this solution was performed according to Example 2. Then, this pyrolyzate was collect | recovered and spherical electrode material powder F (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder F had a LiFePO ₄ / C ratio of 95/5 by weight.

(Comparative Example 1)
1.7 g of sucrose having no reducing property was added to 1000 g of the aqueous solution A of Example 1 and dissolved. The sucrose content in the electrode material at this time was 10.8% by weight.
Subsequently, spray pyrolysis of this solution was performed according to Example 1. Then, this pyrolyzate was collect | recovered and spherical electrode material powder G (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder G had a LiFePO ₄ / C ratio of 94.5 / 4.5 by weight.

(Comparative Example 2)
1.7 g of sucrose having no reducing property was added to 1000 g of the aqueous solution B of Example 2 and dissolved. The sucrose content in the electrode material at this time was 10.8% by weight.
Subsequently, spray pyrolysis of this solution was performed according to Example 2. Then, this pyrolyzate was collect | recovered and spherical electrode material powder H (secondary particle) with a particle size of 0.2-5 micrometers was obtained.
The electrode material powder H had a LiFePO ₄ / C ratio of 95/5 by weight.

“Production of lithium-ion batteries”
Example 1
The electrode material powder A obtained above, acetylene black (AB) as a conductive auxiliary agent, polyvinylidene fluoride (PVdF) as a binder, N-methyl-2-pyrrolidinone (NMP) as a solvent, these are mixed and paste Turned into. The weight ratio in the paste LiFePO _4: C: PVdF 85: 10: 5.
Next, this paste was applied onto an aluminum (Al) foil having a thickness of 30 μm and dried. Then, it compacted with the pressure of 40 Mpa, and set it as the positive electrode.

Next, this positive electrode was punched into a disk shape having an area of 2 cm ² using a molding machine, vacuum dried, and then subjected to a stainless steel (SUS) 2016 coin cell in a dry Ar atmosphere. A lithium ion battery was prepared. Metal Li was used for the negative electrode, a porous polypropylene film was used for the separator, and a 1M LiPF ₆ solution was used for the electrolyte solution. As a solvent for this LiPF ₆ solution, a solvent having a ratio of ethylene carbonate to diethyl carbonate of 1: 1 was used.

Further, the lithium ion batteries of Examples 2 to 6 and Comparative Examples 1 and 2 were respectively used in the same manner as the lithium battery of Example 1 using the electrode material powders B to H of Examples 2 to 6 and Comparative Examples 1 and 2. Was made. The weight ratios LiFePO ₄ : C: PVdF in the pastes of Examples 2 to 6 and Comparative Examples 1 and 2 were all 85: 10: 5.

"Battery charge / discharge test"
The charge / discharge test of each of the lithium ion batteries of Examples 1 to 6 and Comparative Examples 1 and 2 was performed at room temperature (25 ° C.) at a constant voltage (charged for 1 hour) with a cutoff voltage of 2-4.5 V and a charge / discharge rate of 1 C 1 hour discharge).
Table 1 shows the discharge capacities (1C) of each of Examples 1 to 6 and Comparative Examples 1 and 2 at room temperature (25 ° C.). Moreover, FIG. 2 shows the charge / discharge characteristics at room temperature (25 ° C.) of each of Examples 1 and 2 and Comparative Examples 1 and 2.

According to the above results, it was found that the electrode material powders A to F of the examples using reducing sugars can obtain a higher discharge capacity than the electrode material powders G and H of comparative examples not using reducing sugars. . In addition, the electrode material powders B, D, and F using forcibly oxidized FeCl ₂ have high discharge capacities almost equivalent to the electrode material powders A, C, and E using non-oxidized FeCl _2. I found out that Therefore, even when synthesizing an electrode material that is easily oxidized, there is no need to strictly control the oxygen concentration in the atmosphere, and even when a forcedly oxidized (low-grade) raw material is used, It has been found that a good electrode material can be synthesized.

The electrode material of the present invention is Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Cr, Mn, Fe, Co, Ni, Cu, D is Mg, Ca, One or more selected from the group consisting of Sr, Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y and rare earth elements, 0 <x <2, 0 <y <1 .5, 0 ≦ z <1.5), a plurality of primary particles are aggregated to form secondary particles, and carbon generated by thermal decomposition of reducing sugar, which is an electron conductive substance, is formed from the primary particles. It is possible to further improve the charge / discharge capacity of the lithium ion battery, stabilize the charge / discharge cycle, improve the filling property, increase the output, and improve the low-temperature load characteristics. Suitable for next-generation secondary batteries that are expected to be lighter, lighter, and higher capacity It is possible to, when the next generation of the secondary battery, the effect is very large.

It is sectional drawing which shows an example of the cross-sectional shape of the electrode material of this invention. It is a figure which shows the charging / discharging characteristic in each of Example 1, 2 and Comparative Example 1, 2 at room temperature.

Explanation of symbols

1 Primary particle 2 Carbon generated by thermal decomposition of reducing sugar 3 Secondary particle

Claims (7)

Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Cr, Mn, Fe, Co, Ni, Cu, D is Mg, Ca, Sr, Ba, Ti, Zn) , B, Al, Ga, In, Si, Ge, Sc, Y, one or more selected from the group of rare earth elements, 0 <x <2, 0 <y <1.5, 0 ≦ z < 1.5) An electrode material comprising a plurality of primary particles made of 1.5) to form secondary particles, and the primary particles are joined via carbon generated by thermal decomposition of reducing sugar. .   The electrode material according to claim 1, wherein the carbon content is 0.1 wt% or more and 30 wt% or less. Li _x A _y D _z PO ₄ (where A is one or more selected from the group of Cr, Mn, Fe, Co, Ni, Cu, D is Mg, Ca, Sr, Ba, Ti, Zn) , B, Al, Ga, In, Si, Ge, Sc, Y, one or more selected from the group of rare earth elements, 0 <x <2, 0 <y <1.5, 0 ≦ z < 1.5) is a method for producing an electrode material in which a plurality of primary particles made of 1.5) are aggregated into secondary particles, and these primary particles are joined via carbon generated by thermal decomposition of reducing sugar. And
Li component, A component (where A is one or more selected from the group of Cr, Mn, Fe, Co, Ni, Cu) and D component (where D is Mg, Ca, Sr, A solution containing Ba, Ti, Zn, B, Al, Ga, In, Si, Ge, Sc, Y, or a rare earth element), a P component, and a reducing sugar A method for producing an electrode material, wherein the suspension is sprayed and heated.   The method for producing an electrode material according to claim 3, wherein the component A is Fe.   The method for producing an electrode material according to claim 3 or 4, wherein the reducing sugar is one or more selected from the group consisting of glucose, fructose, maltose and lactose. The content of the reducing sugar in solution or suspension, said _Li x _A y _D z claim 3, 4, characterized in that relative to PO ₄ is 0.2 wt% or more and 70 wt% Or the manufacturing method of the electrode material of 5. A lithium ion battery comprising a positive electrode using the electrode material according to claim 1.

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