JP5930105B1 - Positive electrode material for lithium ion secondary battery, positive electrode for lithium ion secondary battery, lithium ion secondary battery - Google Patents

Abstract

Provided are an electrode material for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery having a high discharge capacity and mass energy density at low temperature and high speed charge / discharge. An electrode material for a lithium ion secondary battery according to the present invention includes an electrode active material made of LiFexMn1-x-yMyPO4 (0.220 ≦ x ≦ 0.350, 0.005 ≦ y ≦ 0.018). , M is only Co, or both Co and Zn, the electrode active material has an orthorhombic crystal structure, a space group is Pnma, and values of crystal lattice constants a, b, and c are 10.28 Å ≦ a ≦ 10.42 Å, 6.000 Å ≦ b ≦ 6.069 Å, 4.710 Å ≦ c ≦ 4.728 満 た し are satisfied, and the lattice volume V satisfies 289.00Å3 ≦ V ≦ 298.23Å3. [Selection figure] None

Description

  The present invention relates to an electrode material for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery.

The electrode material made of LiMnPO ₄ has a higher battery reaction voltage than the electrode material made of LiFePO ₄ and can be expected to have a high energy density (mass energy density) of about 20%. Therefore, the electrode material made of LiMnPO ₄ is expected to be developed into a secondary battery for electric vehicles.

However, in the lithium ion secondary battery comprising a positive electrode containing an electrode material consisting of LiMnPO _4, low electron conductivity of LiMnPO ₄ bulk, low Li diffusion of LiMnPO ₄ bulk, and, Jahn-Teller effect of manganese ions ^{(Mn 2+)} As a result, the LiMnPO ₄ crystals undergo anisotropic and large volume changes with the battery reaction. Therefore, in the lithium ion secondary battery having such a configuration, activation energy for inserting and desorbing lithium ions from the positive electrode is increased. As a result, the battery characteristics at a low temperature are remarkably deteriorated in this lithium ion secondary battery.

LiFe _x Mn _1-x PO ₄ (0 <x <1), in which a part of Mn in LiMnPO ₄ is replaced with Fe in order to improve battery characteristics at low temperatures of lithium ion secondary batteries, has been actively studied. (For example, refer to Patent Document 1). In LiFe _x Mn _1-x PO ₄ , since Fe is dissolved, the electron conductivity in the particles is improved as compared with LiMnPO ₄ . As a result, the charge / discharge performance of the lithium ion secondary battery including the positive electrode including the electrode material made of LiFe _x Mn _1-x PO ₄ is improved.

  However, no example has been reported in which an electrode material capable of realizing, for example, a lithium ion secondary battery excellent in battery characteristics at a low temperature or high-speed charge / discharge using the technique described in Patent Document 1 or the like has not been reported.

Therefore, to further improve the electrical characteristics of LiFe _x Mn _1-x PO ₄ and to obtain a high energy density when used as an electrode material, Mn in LiFe _x Mn _1-x PO ₄ is further replaced with a divalent metal. Substituted LiFe _x Mn _{1- xy My} PO ₄ has been studied (see, for example, Patent Documents 2 and 3).

JP 2013-101883 A Special table 2013-518378 gazette Special table 2013-518023 gazette

  However, even if it is an electrode material to the invention of patent document 2, 3, the electrode material which has a satisfactory battery characteristic was not obtained, and the further improvement was calculated | required.

  The present invention has been made in view of the above circumstances, and provides an electrode material for a lithium ion secondary battery having a high discharge capacity and mass energy density at low temperature and high speed charge / discharge, and an electrode material for the lithium ion secondary battery. It aims at providing the electrode for lithium ion secondary batteries to contain, and the lithium ion secondary battery provided with the electrode for lithium ion secondary batteries.

As a result of intensive studies to solve the above-described problems, the present inventors have found that a very small amount of Mn in LiFe _x Mn _1-x PO ₄ has a small amount of substitution of Fe (substitution amount is less than 50%). The third element M, ie, only Co, which is electrochemically inactive in a voltage range of 1.0 V to 4.3 V and has an ionic radius smaller than Mn, or is substituted by both Co and Zn. Thus, it has been found that the ion conductivity can be improved by improving the electron conductivity and setting the crystal lattice constant within a predetermined range. In addition, a part of Mn of LiFe _x Mn _1-x PO ₄ is further replaced with only Co or both Co and Zn, and the crystal lattice constant is within a predetermined range, so that the crystal lattice volume It has been found that the expansion and contraction of the lattice volume accompanying the change in the valence of the transition metal element during charging and discharging can be suppressed.

It is assumed that 50% or more of Mn in LiMnPO ₄ needs to be replaced with Fe in order to realize a lithium ion secondary battery having excellent battery characteristics at low temperatures. A lithium ion secondary battery (hereinafter referred to as “lithium ion secondary battery A”) using an electrode material made of LiFe _x Mn _1-x PO ₄ containing a large amount of Fe uses an electrode material made of LiMnPO ₄ . The charge / discharge capacity is increased as compared with the conventional lithium ion secondary battery (hereinafter referred to as “lithium ion secondary battery B”). However, in the lithium ion secondary battery A, the ratio of the battery reaction at a high voltage derived from LiMnPO ₄ is reduced, and the battery reaction derived from LiFePO ₄ is increased. Therefore, in the lithium ion secondary battery A, the effect of improving the mass energy density, which is expected when the electrode (positive electrode) contains LiMnPO ₄ , cannot be obtained.

On the other hand, a lithium ion secondary battery B or a lithium ion secondary battery using an electrode material made of LiFe _x Mn _1-x PO ₄ (0 <x <1) having a smaller amount of Fe substitution than the lithium ion secondary battery A batteries, low electron conductivity of the above LiMnPO ₄ bulk, low Li diffusion of LiMnPO ₄ bulk, and by Jahn-Teller effect of ^{Mn 2+,} particularly in low-temperature and high-speed charging and discharging, good discharge capacity and mass energy density obtained There was a problem that it was not possible.

However, according to the substance in which a part of Mn of LiFe _x Mn _1-x PO ₄ is further substituted with only Co or both Co and Zn and the crystal lattice constant is within a predetermined range, bulk electron conduction And Li diffusibility are improved, the yarn teller effect is relaxed, and the lithium de-insertion activation energy during the battery reaction is reduced, and the high material energy density of LiFe _x Mn _1-x PO ₄ is more than necessary. The present inventors have found that the low-temperature characteristics and the high-speed charge / discharge characteristics can be greatly improved without losing any of the above.

That is, the electrode material for a lithium ion secondary battery of the present invention is made of LiFe _x Mn _{1- xy My} PO ₄ (0.220 ≦ x ≦ 0.350, 0.005 ≦ y ≦ 0.018). A positive electrode material for a lithium ion secondary battery containing an electrode active material,
Said M is only Co or both Co and Zn,
The electrode active material has a crystal structure space group Pnma, and crystal lattice constants a, b, and c have values of 10.28Å ≦ a ≦ 10.42Å, 6.000Å ≦ b ≦ 6.069Å, and 4.710Å. met ≦ c ≦ 4.728Å, lattice volume V is less than the 289.00Å ³ ≦ V ≦ 298.23Å ^3,
The surface of the electrode active material is coated with a carbonaceous film, and the activation energy of the lithium ion insertion / desorption reaction occurring at the interface between the electrode active material and the carbonaceous film is 55 kJ / mol or less. And

For a lithium ion secondary battery positive electrode of the present invention includes an electrode current collector, the electrode mixture layer formed on the electrode current collector, a lithium ion secondary battery positive electrode wherein the electrode The mixture layer contains the positive electrode material for a lithium ion secondary battery of the present invention.

The lithium ion secondary battery of the present invention includes the positive electrode for a lithium ion secondary battery of the present invention.

  According to the electrode material for a lithium ion secondary battery of the present invention, since the electron conductivity and the ion conductivity are improved, a lithium ion secondary battery having a high discharge capacity and a high mass energy density is realized at low temperature and high speed charge / discharge. be able to.

  According to the electrode for a lithium ion secondary battery of the present invention, since the electrode material for a lithium ion secondary battery of the present invention is contained, the lithium ion secondary battery having a high discharge capacity and high mass energy density at low temperature and high speed charge / discharge. A secondary battery electrode can be obtained.

  According to the lithium ion secondary battery of the present invention, since the lithium ion secondary battery electrode of the present invention is provided, a lithium ion secondary battery having a high discharge capacity and high mass energy density is obtained at low temperature and high speed charge / discharge. be able to.

Embodiments of an electrode material for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery of the present invention will be described.
Note that this embodiment is specifically described in order to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[Electrode materials for lithium ion secondary batteries]
The electrode material for a lithium ion secondary battery of this embodiment is an electrode made of LiFe _x Mn _{1- xy My} PO ₄ (0.220 ≦ x ≦ 0.350, 0.005 ≦ y ≦ 0.018). An electrode material for a lithium ion secondary battery including an active material, wherein M is only Co or both Co and Zn, and the electrode active material has an orthorhombic crystal structure and a space group of Pnma The values of crystal lattice constants a, b and c satisfy 10.28Å ≦ a ≦ 10.42Å, 6.000Å ≦ b ≦ 6.069Å, 4.710Å ≦ c ≦ 4.728Å, and the lattice volume V is 289.00． ³ ≦ V ≦ 298.23Å ³ is satisfied.
The electrode material for lithium ion secondary batteries of this embodiment is mainly used as an electrode material for lithium ion secondary batteries.

The electrode material for a lithium ion secondary battery of the present embodiment is obtained by coating the surface of primary particles of an electrode active material made of LiFe _x Mn _{1- xy My} PO _{4 with a} carbonaceous film.

The average primary particle diameter of the primary particles of the electrode active material composed of LiFe _x Mn _{1- xy My} PO ₄ is preferably 50 nm or more and 400 nm or less, and more preferably 80 nm or more and 260 nm or less.
_Here, the reason for the _{LiFe x Mn 1-x-y} M y PO 4 average primary particle size ranges of the _{particles, LiFe x Mn 1-x-y} M y PO 4 having an average primary particle size of 50nm particles If it is less than 1, it becomes too fine to make it difficult to maintain good crystallinity. As a result, the lengths of the crystal lattice of LiFe _x Mn _{1- xy My} PO ₄ particles in the a-axis direction and c-axis direction are reduced. This is because it is impossible to obtain LiMnPO ₄ particles whose length in the b-axis direction is specifically shortened while keeping it large. On the other _hand, when the average primary particle size of _{LiFe x Mn 1-x-y} M y PO 4 particles exceeds 400 nm, it becomes finer the _{LiFe x Mn 1-x-y} M y PO 4 particles insufficient, as a result This is because not very fine and good crystallinity _{LiFe x Mn 1-x-y} M y PO 4 particles is obtained.

The thickness of the carbonaceous film is preferably 1 nm or more and 12 nm or less.
The reason why the thickness of the carbonaceous film is in the above range is that if the thickness is less than 1 nm, the carbonaceous film cannot be formed with a desired resistance value because the thickness of the carbonaceous film is too thin. This is because the conductivity is lowered and the conductivity as the electrode material cannot be secured. On the other hand, when the thickness of the carbonaceous film exceeds 12 nm, battery activity, for example, battery capacity per unit mass of the electrode material decreases.

The average primary particle diameter of the primary particles of the electrode active material composed of LiFe _x Mn _{1- xy My} PO ₄ coated with a carbonaceous film is preferably 65 nm or more and 400 nm or less, and 75 nm or more and 270 nm or less. It is more preferable that
Here, the reason why the average primary particle diameter of the primary particles of the electrode active material composed of LiFe _x Mn _{1- xy My} PO ₄ coated with the carbonaceous film is in the above range is that the average primary particle diameter is 65 nm. If the specific surface area of the carbonaceous electrode active material composite particles is less than 1, the required carbon mass increases, the charge / discharge capacity is reduced, and carbon coating becomes difficult and primary particles with sufficient coverage are obtained. This is because good discharge capacity and mass energy density cannot be obtained particularly at low temperatures and high-speed charge / discharge. On the other hand, if the average primary particle diameter exceeds 400 nm, it takes time to move lithium ions or electrons in the carbonaceous electrode active material composite particles, which increases internal resistance and deteriorates output characteristics. Because.

The shape of the primary particles of the electrode active material composed of LiFe _x Mn _{1- xy My} PO ₄ coated with a carbonaceous film is not particularly limited, but it is easy to produce an electrode material composed of spherical, particularly spherical particles. Therefore, the shape is preferably spherical.
Here, the reason why the spherical shape is preferable is that an electrode material paste for a lithium ion secondary battery is prepared by mixing primary particles of an electrode active material coated with a carbonaceous film, a binder, and a solvent. This is because the amount of the solvent during the treatment can be reduced and the application of the electrode material paste for a lithium ion secondary battery to the current collector is facilitated. Further, if the shape is spherical, the surface area of the primary particles of the electrode active material is minimized, so that the amount of the binder to be added can be minimized, and the internal resistance of the obtained electrode is reduced. Because you can.
Furthermore, since the shape of the primary particles of the electrode active material is spherical, and particularly spherical, it becomes easy to close-pack, so the filling amount of the electrode material for the lithium ion secondary battery per unit volume increases. This is preferable because the electrode density can be increased and the capacity of the lithium ion battery can be increased.

The amount of carbon contained in the electrode material for a lithium ion secondary battery of the present embodiment is preferably 0.5% by mass or more and 5.0% by mass or less, and 0.8% by mass or more and 2.5% by mass. The following is more preferable.
Here, the reason why the amount of carbon contained in the electrode material for a lithium ion secondary battery of the present embodiment is limited to the above range is that when the amount of carbon is less than 0.5% by mass, a battery is formed at high speed charge / discharge This is because the discharge capacity at the rate becomes low and it becomes difficult to realize sufficient charge / discharge rate performance. On the other hand, if the amount of carbon exceeds 5.0% by mass, the amount of carbon is too large, and the battery capacity of the lithium ion battery per unit mass of the primary particles of the electrode active material is unnecessarily reduced.

Further, the amount of carbon supported relative to the specific surface area of the primary particles of the electrode active material ([carbon supported amount] / [specific surface area of the primary particles of electrode active material]) is preferably 0.04 or more and 0.40 or less. 0.07 or more and 0.30 or less is more preferable.
Here, the reason why the amount of carbon supported in the electrode material for a lithium ion secondary battery of this embodiment is limited to the above range is that when the amount of carbon supported is less than 0.04, the battery is formed at a high-speed charge / discharge rate. This is because the discharge capacity is lowered and it is difficult to realize sufficient charge / discharge rate performance. On the other hand, when the amount of carbon supported exceeds 0.40, the amount of carbon is too large, and the battery capacity of the lithium ion battery per unit mass of the primary particles of the electrode active material is unnecessarily reduced.

The specific surface area of the electrode material for a lithium ion secondary battery of the present embodiment is preferably 8 m ² / g or more and 18 m ² / g or less, more preferably 10 m ² / g or more and 15 m ² / g or less. preferable.
Here, the reason why the specific surface area of the electrode material for a lithium ion secondary battery of the present embodiment is limited to the above range is that if the specific surface area is less than 8 m ² / g, the lithium ion in the carbonaceous electrode active material composite particles This is because it takes a long time to move the electrons or the electrons, which increases the internal resistance and deteriorates the output characteristics. On the other hand, when the specific surface area exceeds 18 m ² / g, the carbon mass required by increasing the specific surface area of the carbonaceous electrode active material composite particles increases, and the charge / discharge capacity decreases, which is not preferable.

"Electrode active material"
The electrode active material is made of LiFe _x Mn _{1- xy My} PO ₄ (0.220 ≦ x ≦ 0.350, 0.005 ≦ y ≦ 0.018) having a crystal structure suitable for Li diffusion.
The reason why x satisfies 0.220 ≦ x ≦ 0.350 in LiFe _x Mn _{1- xy My} PO ₄ is as follows.
First, Fe develops charge / discharge capacity in the vicinity of a voltage of 3.5 V. Therefore, the mass energy density is gradually decreased due to solid solution as compared with Co and Zn. Therefore, by setting x to a relatively large amount of 0.350 or less, improvement in low temperature characteristics can be expected within a range where the mass energy density is not excessively reduced.
On the other hand, Fe can reduce the volume resistance of the electrode active material while being kept in a high voltage state due to solid solution. Therefore, when x is 0.220 or more, charging / discharging becomes easy, and output characteristics and low-temperature characteristics can be improved. Moreover, Fe is a carbonization catalyst element, and output characteristics and low temperature characteristics can be improved by improving the coverage of the carbonaceous film by Fe solid solution.

The reason why y satisfies 0.005 ≦ y ≦ 0.018 in LiFe _x Mn _{1- xy My} PO ₄ is as follows.
First, Co and Zn are elements having an ionic radius smaller than that of Mn. When Co or Zn is replaced with Mn, the packing density of the crystal lattice of the positive electrode active material can be increased. Therefore, by setting y to 0.005 or more, a high improvement effect can be expected in the electron conductivity, the Li diffusibility, and the activation energy of the lithium ion (Li ⁺ ) insertion / release reaction.
On the other hand, Co and Zn are electrochemically inactive elements in the voltage range of 1.0 V to 4.3 V, and the reduction of charge / discharge capacity and mass energy density becomes remarkable due to a large amount of solid solution. Therefore, by setting y to a relatively small amount of 0.018 or less, the low temperature characteristics can be sufficiently improved within a range where the mass energy density is not excessively reduced.

  In the present invention, as described above, the amount of solid solution is set according to the characteristics of each element of Fe, Co, and Zn. In addition, the effect has been confirmed also in examples described later.

In LiFe _x Mn _{1- xy My} PO ₄ , M is an electrochemically inactive element within a voltage range of 1.0 V to 4.3 V. Specifically, the electrochemical inertness in the voltage range of 1.0V to 4.3V means that even when the lithium ion secondary battery is configured and the voltage is changed in the range of 1.0V to 4.3V, An element that does not contribute to the development of charge / discharge capacity is preferable because the valence of the element remains divalent.

As such M,
(1) Only Co, which is an element having an ionic radius smaller than Mn, or
(2) Both Co and Zn, which is an element having an ionic radius smaller than Mn, can be mentioned.
When M is only Co or both Co and Zn, the above y satisfies 0.005 ≦ y ≦ 0.018 and preferably satisfies 0.01 ≦ y ≦ 0.015.

In the electrode active material for a lithium ion secondary battery of the present embodiment, LiFe _x Mn _{1- xy My} PO ₄ () is obtained by substituting a part of Mn with only Co or both Co and Zn. 0.220 ≦ x ≦ 0.350, 0.005 ≦ y ≦ 0.018), the bulk electron conductivity and Li diffusibility, the activation energy of the lithium ion insertion / desorption reaction can be improved, and the output characteristics and Characteristics such as low temperature characteristics can be improved.
When M is both Co and Zn, the amount of Co is preferably larger than the amount of Zn.

LiFe _x Mn _{1- xy My} PO ₄ has an orthorhombic crystal structure and a space group of Pnma. The values of the crystal lattice constants a, b and c of LiFe _x Mn _{1- xy My} PO ₄ are 10.28 Å ≦ a ≦ 10.42 Å, 6.000 Å ≦ b ≦ 6.069 Å, 4.710 Å ≦ c The reason for satisfying ≦ 4.728Å is that this range is that the length of the crystal lattice of the LiFe _x Mn _{1- xy My} PO ₄ particle is long in the a-axis direction and c-axis direction, and LiFe _x Mn _This is because the length in the b-axis direction of the crystal lattice of _{1- xy My} PO ₄ particles is in a specifically short range.
The values of the crystal lattice constants a, b, and c of LiFe _x Mn _{1- xy My} PO ₄ are values calculated from an X-ray diffraction pattern.

The reason why the volume of the crystal lattice of LiFe _x Mn _{1- xy My} PO ₄ , that is, the lattice volume V satisfies 289.00Å ³ ≦ V ≦ 298.23Å ³ is that this range is the structure This is because the distance between the elements is appropriate, and both the bulk electron conductivity and Li diffusibility can be improved. When the distance between the elements in the structure is too close, the electron transfer between the elements is good and the electron conductivity is good. However, the gap that becomes the movement path of Li becomes narrow, so the Li diffusibility Gets worse. If the distance between elements in the structure is too far, the gap that becomes the movement path of Li becomes wide and Li diffusibility is improved. However, since it becomes difficult to exchange electrons between elements, electron conductivity Gets worse.

A lithium ion secondary battery including an electrode material layer formed on an electrode current collector using the lithium ion secondary battery electrode material of the present embodiment is 25 ° C. The ratio of the 0.1 CA discharge capacity measured at 0 ° C. to the 0.1 CA discharge capacity measured at is preferably 80% or more, and more preferably 85% or more.
If the ratio of the 0.1 CA discharge capacity measured at 0 ° C. to the 0.1 CA discharge capacity measured at 25 ° C. is 80% or more, for example, when using a lithium ion secondary battery in a cold region, It is possible to use a lithium ion secondary battery for a long time, which is no different from using a lithium ion secondary battery in a warm area. On the other hand, when the ratio of the 0.1 CA discharge capacity measured at 0 ° C. to the 0.1 CA discharge capacity measured at 25 ° C. is less than 80%, for example, when using a lithium ion secondary battery in a cold region, Compared to using a lithium ion secondary battery in a warm area, the battery is used for a very short time, which is not preferable.

A lithium ion secondary battery provided with an electrode for a lithium ion secondary battery in which an electrode mixture layer is formed on an electrode current collector using the electrode material for a lithium ion secondary battery of the present embodiment is The 0.1 CA discharge capacity measured at 1 is preferably 120 mAh / g or more, and more preferably 125 mAh / g or more.
If the 0.1 CA discharge capacity measured at 0 ° C. is 120 mAh / g or more, for example, even when using a lithium ion secondary battery in a cold region, the battery capacity is sufficient, and long-term lithium ion A secondary battery can be used. On the other hand, if the 0.1 CA discharge capacity measured at 0 ° C. is less than 120 mAh / g, for example, when a lithium ion secondary battery is used in a cold region, the battery capacity is insufficient. The use of lithium ion secondary batteries for hours is impossible.

A lithium ion secondary battery including an electrode material layer formed on an electrode current collector using the lithium ion secondary battery electrode material of the present embodiment is 25 ° C. The ratio of the mass energy density at 0 ° C. and 0.1 CA discharge to the mass energy density at 0.1 CA discharge is preferably 80% or more, and more preferably 85% or more.
When the ratio of the mass energy density at 0 ° C. and 0.1 CA discharge to the mass energy density at 25 ° C. and 0.1 CA discharge is 80% or more, for example, when using a lithium ion secondary battery in a cold district However, a high mass energy density comparable to that of using a lithium ion secondary battery in a warm region can be obtained. When such a lithium ion battery is used in an electric vehicle such as an EV (electric vehicle), a cruising range comparable to that of driving in a warm region even in a cold region can be achieved. On the other hand, when the ratio of the mass energy density at 0 ° C. and 0.1 CA discharge to the mass energy density at 25 ° C. and 0.1 CA discharge is less than 80%, for example, when using a lithium ion secondary battery in a cold district Compared with the use of lithium ion secondary batteries in warm regions, the mass energy density is significantly lower. When such a lithium ion secondary battery is used for an electric vehicle such as an EV, the cruising capability in a cold region is remarkably shortened.

In the electrode material for a lithium ion secondary battery of the present embodiment, the surface of primary particles of the electrode active material is covered with a carbonaceous film, and insertion of lithium ions (Li ⁺ ) that occurs at the interface between the electrode active material and the carbonaceous film. The activation energy of the elimination reaction is preferably 55 kJ / mol or less, and more preferably 54 kJ / mol or less.
If the activation energy of the lithium ion insertion / desorption reaction is 55 kJ / mol or less, good low temperature characteristics can be achieved without significantly inhibiting the lithium ion insertion / desorption reaction even at a low temperature of 0 ° C. It is. On the other hand, when the activation energy of the insertion / desorption reaction of lithium ions exceeds 55 kJ / mol, the insertion / release reaction of lithium ions is significantly inhibited at a low temperature such as 0 ° C., and good low-temperature characteristics cannot be achieved.

[Method for producing electrode material for lithium ion secondary battery]
The method for producing an electrode material for a lithium ion secondary battery according to the present embodiment includes, for example, a Li source, a P source, an Fe source, a Mn source, a Co source, and, if necessary, a Zn source, a solvent containing water as a main component, Mixing, and heating the obtained raw material slurry A to a temperature in the range of 120 ° C. to 250 ° C. to synthesize LiFe _x Mn _{1- xy My} PO ₄ particles under pressure; The raw slurry B obtained by dispersing LiFe _x Mn _{1- xy My} PO ₄ particles in an aqueous solvent containing a water-soluble thickener is dried and granulated, and then 550 ° C. or higher and 820 ° C. or lower. by heating to a range of _{temperatures,} and a method comprising the steps of coating the surface of _{LiFe x Mn 1-x-y} M y PO 4 particles (primary particles) by carbonaceous coating, a.

Regarding the purity of the crystal structure and the LiFe _x Mn _1-xy MyPO ₄ particles, the molar concentration of the Li source, P source, Fe source, Mn source, Co source and Zn source in the raw slurry A and the heating rate in the hydrothermal treatment Affected by.
When the raw material slurry A is too dilute, high purity LiFe _x Mn _1-xy MyPO ₄ particles can be obtained, but this is not preferable because the crystal lattice constant increases and the crystal structure becomes unsuitable for Li diffusion. When the raw material slurry A is too concentrated, the crystal lattice constant is reduced and a crystal structure preferable for Li diffusion is obtained, but impurities are easily generated and the purity of the LiFe _x Mn _1-xy MyPO ₄ particles is lowered. This is not preferable.
When the rate of temperature rise is too slow, high purity LiFe _x Mn _1-xy MyPO ₄ particles can be obtained, but this is not preferable because the crystal lattice constant is increased and the crystal structure becomes unfavorable for Li diffusion. The heating rate is preferably 1 ° C./min or more, more preferably 3 ° C./min or more.

In the above production method, first, a Li source, a P source, an Fe source, a Mn source, a Co source and, if necessary, a Zn source are put into a solvent containing water as a main component, stirred, and LiFe _x Mn ₁₋ preparing slurry a containing precursor of _x-y M _y PO _4.

These Li source, P source, Fe source, Mn source, Co source and Zn source are mixed at a molar ratio thereof (Li source: P source: Fe source: Mn source: Co source: Zn source), that is, Li: P: The molar ratio of Fe: Mn: Co: Zn is 1.8 to 3.5: 0.9 to 1.3: 0.05 to 0.35: 0.49 to 0.945: 0 to 0.14: 0. A raw material slurry A is prepared by adding water to a solvent containing water as a main component so as to be about 0.14, and stirring and mixing.
Considering the point that these Li source, P source, Fe source, Mn source, Co source and Zn source are uniformly mixed, the Li source, P source, Fe source, Mn source, Co source and Zn source are each once It is preferable to mix after making it into the state of an aqueous solution.
The molar concentration of Li source, P source, Fe source, Mn source, Co source and Zn source in this raw slurry A is high purity, high crystallinity and very fine, and LiFe having a preferable crystal lattice constant. _Since it is necessary to obtain _x Mn _{1- xy My} PO ₄ particles, the resulting LiFe _x Mn _{1- xy My} PO ₄ particles are 0.6 mol / L or more and 2.2 mol / L or less. The range is preferable.

Examples of the Li source include hydroxides such as lithium hydroxide (LiOH), lithium carbonate (Li ₂ CO ₃ ), lithium chloride (LiCl), lithium nitrate (LiNO ₃ ), and lithium phosphate (Li ₃ PO ₄ ). , Lithium inorganic acid salts such as dilithium hydrogen phosphate (Li ₂ HPO ₄ ) and lithium dihydrogen phosphate (LiH ₂ PO ₄ ), lithium such as lithium acetate (LiCH ₃ COO) and lithium oxalate ((COOLi) ₂ ) Examples include organic acid salts and hydrates thereof. As the Li source, at least one selected from these groups is preferably used.
Note that lithium phosphate (Li ₃ PO ₄ ) can also be used as a Li source and a P source.

Examples of the P source include phosphoric acid such as orthophosphoric acid (H ₃ PO ₄ ) and metaphosphoric acid (HPO ₃ ), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ), and diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ), ammonium phosphate ((NH ₄ ) ₃ PO ₄ ), lithium phosphate (Li ₃ PO ₄ ), dilithium hydrogen phosphate (Li ₂ HPO ₄ ), lithium dihydrogen phosphate (LiH ₂ PO ₄ ) and other phosphates and at least one selected from these hydrates are preferably used.

Examples of Fe sources include iron nitrate (II) (Fe (NO ₃ ) ₂ ), iron chloride (II) (FeCl ₂ ), iron sulfate (II) (FeSO ₄ ), iron acetate (II) (Fe (CH ₃ COO) ₂ ) and other iron compounds or hydrates thereof, iron nitrate (III) (Fe (NO ₃ ) ₃ ), iron chloride (III) (FeCl ₃ ), iron (III) citrate (FeC ₆ H) _And trivalent iron compounds such as ₅ O ₇ ) and lithium iron phosphate. As the Fe source, at least one selected from these groups is preferably used.

As the Mn source, a Mn salt is preferable. For example, manganese nitrate (II) (Mn (NO ₃ ) ₂ ), manganese chloride (II) (MnCl ₂ ), manganese sulfate (II) (MnSO ₄ ), manganese nitrate (II) ) (Mn (NO ₃ ) ₂ ), manganese (II) acetate (Mn (CH ₃ COO) ₂ ), and hydrates thereof. As the Mn source, at least one selected from these groups is preferably used.

As the Co source, a Co salt is preferable. For example, cobalt nitrate (II) (Co (NO ₃ ) ₂ ), cobalt chloride (II) (CoCl ₂ ), cobalt sulfate (II) (CoSO ₄ ), cobalt nitrate (II) ) (Co (NO ₃ ) ₂ ), cobalt (II) acetate (Co (CH ₃ COO) ₂ ), and hydrates thereof. As the Co source, at least one selected from these groups is preferably used.

The Zn source is preferably a Zn salt. For example, zinc nitrate (II) (Zn (NO ₃ ) ₂ ), zinc chloride (II) (ZnCl ₂ ), zinc sulfate (II) (ZnSO ₄ ), zinc nitrate (II ) (Zn (NO ₃ ) ₂ ), zinc (II) acetate (Zn (CH ₃ COO) ₂ ), and hydrates thereof. As the Zn source, at least one selected from these groups is preferably used.

The solvent containing water as a main component is either water alone or an aqueous solvent containing water as a main component and containing an aqueous solvent such as alcohol as necessary.
The aqueous solvent is not particularly limited as long as it can disperse the Li source, P source, Fe source, Mn source, Co source, and Zn source. For example, methanol, ethanol, 1-propanol, 2- Alcohols such as propanol (isopropyl alcohol: IPA), butanol, pentanol, hexanol, octanol, diacetone alcohol, ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone Esters such as diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl) Rosolve), ethers such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetylacetone and cyclohexanone, dimethylformamide, N, N-dimethylacetoacetamide, N -Amides such as methylpyrrolidone, and glycols such as ethylene glycol, diethylene glycol, and propylene glycol. These aqueous solvents may be used individually by 1 type, and 2 or more types may be mixed and used for them. Moreover, a part of Li source, P source, Fe source, Mn source, Co source and Zn source may be dissolved in these aqueous solvents.

Next, this raw material slurry A is put into a pressure vessel, heated to a temperature in the range of 120 ° C. or more and 250 ° C. or less, preferably 160 ° C. or more and 220 ° C. or less, and subjected to hydrothermal treatment for 1 hour or more and 24 hours or less, LiFe _x Mn _{1- xy My} PO ₄ particles are obtained.
The pressure in the pressure resistant container when reaching a temperature in the range of 120 ° C. or more and 250 ° C. or less is, for example, 0.3 MPa or more and 1.5 MPa or less.
In this case, it is possible to control the particle diameter of the LiFe _x Mn _{1- xy My} PO ₄ particles to a desired size by adjusting the temperature and time during the hydrothermal treatment.

Next, the raw material slurry B is prepared by dispersing LiFe _x Mn _{1- xy My} PO ₄ particles in an aqueous solvent containing a water-soluble thickener.

"Water-soluble thickener"
Although it does not specifically limit as a water-soluble thickener, For example, natural water-soluble polymers, such as gelatin, casein, collagen, hyaluronic acid, albumin, starch, methylcellulose, ethylcellulose, methylhydroxypropylcellulose, carboxymethylcellulose, hydroxymethylcellulose Semi-synthetic polymers such as hydroxypropylcellulose, sodium carboxymethylcellulose, propylene glycol alginate, etc., synthetic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, carbomer (carboxyvinyl polymer), polyacrylate, polyethylene oxide and the like are used.
These water-soluble thickeners may be used alone or in combination of two or more.

In the method for producing an electrode material for a lithium ion secondary battery of the present embodiment, the addition amount (addition rate) of the water-soluble thickener is when the total mass of the electrode active material and the water-soluble thickener is 100% by mass. The content is preferably 1% by mass or more and 15% by mass or less, more preferably 2.5% by mass or more and 9.5% by mass or less.
If the addition amount of the water-soluble thickener is less than 1% by mass, the mixing stability in the electrode material for a lithium ion secondary battery is unfavorable. On the other hand, when the addition amount of the water-soluble thickener exceeds 15% by mass, the content of the electrode active material is relatively reduced, and the battery characteristics are deteriorated.

Next, this raw material slurry B was dried and granulated, and then heated at a temperature in the range of 530 ° C. or more and 850 ° C. or less for 0.5 hour or more and 6 hours or less, and LiFe _x Mn _1-x— the surface of the _y M _y PO ₄ particles (primary particles) were coated with the carbonaceous coating to obtain a lithium ion secondary battery electrode material according to the present embodiment.

[Electrode for lithium ion secondary battery]
The electrode for a lithium ion secondary battery of the present embodiment includes an electrode current collector and an electrode mixture layer (electrode) formed on the electrode current collector, and the electrode mixture layer is the present embodiment. The electrode material for lithium ion secondary batteries is contained.
That is, the electrode for the lithium ion secondary battery of the present embodiment is formed by forming the electrode mixture layer on one main surface of the electrode current collector using the electrode material for the lithium ion secondary battery of the present embodiment. It is.
The electrode for a lithium ion secondary battery of this embodiment is mainly used as a positive electrode for a lithium ion secondary battery.

The method for producing an electrode for a lithium ion secondary battery of the present embodiment is particularly a method that can form an electrode on one main surface of an electrode current collector using the electrode material for a lithium ion secondary battery of the present embodiment. It is not limited. As a manufacturing method of the electrode for lithium ion secondary batteries of this embodiment, the following method is mentioned, for example.
First, the electrode material paste for lithium ion secondary batteries which mixes the electrode material for lithium ion secondary batteries of this embodiment, a binder, a conductive support agent, and a solvent is prepared.

"Binder"
The binder is not particularly limited as long as it can be used in water. For example, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, vinyl acetate copolymer, styrene / butadiene latex, acrylic latex, acrylonitrile. -At least 1 sort (s) selected from groups, such as a butadiene-type latex, a fluorine-type latex, a silicon-type latex, is mentioned.

The content rate of the binder in the electrode material paste for a lithium ion secondary battery is, when the total mass of the electrode material for the lithium ion secondary battery, the binder, and the conductive additive of this embodiment is 100% by mass, It is preferably 1% by mass or more and 15% by mass or less, and more preferably 3% by mass or more and 9% by mass or less.
Here, the reason why the content ratio of the binder is within the above range is that, when the content ratio of the binder is less than 1% by mass, the lithium ion secondary battery including the electrode material for the lithium ion secondary battery of the present embodiment is used. When the electrode mixture layer is formed using the electrode material paste for the electrode, the electrode mixture layer and the current collector are not sufficiently bonded, and the electrode mixture layer cracks when the electrode mixture layer is rolled. This is because there is a case in which a dropout may occur. Further, it is not preferable because the electrode mixture layer is peeled off from the current collector in the charge / discharge process of the battery, and the battery capacity and the charge / discharge rate may decrease. On the other hand, if the content of the binder exceeds 15% by mass, the internal resistance of the electrode material for lithium ion secondary batteries increases, and the battery capacity at a high-speed charge / discharge rate may decrease, which is not preferable. .

"Conductive aid"
The conductive auxiliary agent is not particularly limited, but for example, at least selected from the group of fibrous carbon such as acetylene black, ketjen black, furnace black, vapor grown carbon fiber (VGCF), carbon nanotube and the like. One type is used.

The content of the conductive auxiliary in the electrode material paste for a lithium ion secondary battery is, when the total mass of the lithium ion secondary battery electrode material, the binder and the conductive auxiliary of the present embodiment is 100% by mass, It is preferably 1% by mass or more and 15% by mass or less, and more preferably 3% by mass or more and 10% by mass or less.
Here, the reason why the content ratio of the conductive assistant is within the above range is that when the conductive assistant content is less than 1% by mass, the lithium ion secondary battery including the electrode material for a lithium ion secondary battery of the present embodiment is used. This is because when the positive electrode mixture layer (electrode mixture layer) is formed using the electrode material paste for a battery, the electron conductivity is not sufficient, and the battery capacity and the charge / discharge rate decrease, which is not preferable. On the other hand, if the content of the conductive additive exceeds 15% by mass, the electrode material occupying the positive electrode mixture layer is relatively reduced, which is not preferable because the battery capacity of the lithium ion battery per unit volume is reduced. is there.

"solvent"
In the electrode material paste for a lithium ion secondary battery including the electrode material for a lithium ion secondary battery of the present embodiment, a solvent may be appropriately added in order to facilitate application to an object to be coated such as a current collector. Good.
The main solvent is water, but an aqueous solvent such as alcohols, glycols, and ethers may be contained within a range not losing the characteristics of the electrode material for a lithium ion secondary battery of the present embodiment.

The content of the solvent in the electrode material paste for a lithium ion secondary battery is, when the total mass of the electrode material for the lithium ion secondary battery, the binder, the conductive additive, and the solvent of this embodiment is 100% by mass, It is preferably 80% by mass or more and 300% by mass or less, and more preferably 100% by mass or more and 250% by mass or less.
When the solvent is contained in the above range, an electrode material paste for a lithium ion secondary battery having excellent electrode forming properties and battery characteristics can be obtained.

  The method of mixing the electrode material for a lithium ion secondary battery of the present embodiment, the binder, the conductive additive, and the solvent is not particularly limited as long as these components can be mixed uniformly, Examples thereof include a method using a kneading machine such as a ball mill, a sand mill, a planetary (planetary) mixer, a paint shaker, or a homogenizer.

  Next, the electrode material paste for a lithium ion secondary battery is applied to one main surface of the electrode current collector to form a coating film, this coating film is dried, and then pressure-bonded to form an electrode current collector. An electrode for a lithium ion secondary battery having an electrode mixture layer formed on one main surface can be obtained.

[Lithium ion secondary battery]
The lithium ion secondary battery of the present embodiment includes the lithium ion secondary battery electrode (positive electrode) of the present embodiment, a negative electrode, a separator, and an electrolytic solution.

In the lithium ion secondary battery of this embodiment, the negative electrode, the electrolytic solution, the separator, and the like are not particularly limited.
As the negative electrode, for example, a negative electrode material such as metal Li, a carbon material, a Li alloy, or Li ₄ Ti ₅ O ₁₂ can be used.
A solid electrolyte may be used instead of the electrolytic solution and the separator.

The electrolytic solution is, for example, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed at a volume ratio of 1: 1, and lithium hexafluorophosphate (LiPF ₆ ) is added to the obtained mixed solvent. ) Can be prepared, for example, by dissolving so as to have a concentration of 1 mol / dm ³ .
As the separator, for example, porous polypropylene can be used.

  In the lithium ion secondary battery of this embodiment, since the electrode for lithium ion secondary batteries of this embodiment was used as a positive electrode, it has a high capacity and a high energy density.

  As described above, according to the electrode material for a lithium ion secondary battery of the present embodiment, since the electron conductivity and the ion conductivity are improved, the lithium having a high discharge capacity and mass energy density at low temperature and high speed charge / discharge. An ion secondary battery can be realized.

  According to the electrode for the lithium ion secondary battery of the present embodiment, since the electrode material for the lithium ion secondary battery of the present embodiment is contained, the lithium having a high discharge capacity and mass energy density at low temperature and high speed charge / discharge. An electrode for an ion secondary battery can be provided.

  According to the lithium ion secondary battery of the present embodiment, since the lithium ion secondary battery electrode of the present embodiment is provided, the lithium ion secondary battery has a high discharge capacity and mass energy density at low temperature and high speed charge / discharge. Can be provided.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

[Example 1]
"Synthesis of electrode material for lithium ion secondary battery"
LiFe _0.22 Mn _0.775 Co _0.005 PO ₄ was synthesized as follows.
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Were mixed at a molar ratio of Li: Fe: Mn: Co: P = 3: 0.22: 0.775: 0.005: 1 to prepare 600 ml of raw material slurry A. The slurry concentration was adjusted so that the finished LiFe _0.22 Mn _0.775 Co _0.005 PO ₄ was 1.5 mol / L.
Subsequently, this raw material slurry A was put in a 1.3 L capacity pressure vessel.
Then, about this raw material slurry A, after heating up with the temperature increase rate of 5 degree-C / min, a heating reaction was performed by hold | maintaining at the holding temperature of 175 degreeC for 8 hours, and hydrothermal synthesis was performed. At this time, the pressure in the pressure vessel was 0.9 MPa.
After the reaction, the atmosphere in the heat-resistant container was cooled to room temperature to obtain a precipitate of the reaction product in a cake state.
This precipitate was sufficiently washed with distilled water several times and kept at a moisture content of 60% so as not to be dried to obtain a cake-like substance.
This cake-like substance was vacuum-dried at 70 ° C. for 2 hours, and 7% by mass of polyvinyl alcohol previously adjusted to 10% by mass was dispersed in an aqueous solvent with respect to 95% by mass of the obtained powder (particles). The raw material slurry B was dried and granulated, and then heat treated at 750 ° C. for 4 hours to coat the surfaces of the particles with a carbonaceous film, whereby the electrode material for a lithium ion secondary battery of Example 1 was obtained.

"Production of lithium ion secondary battery"
To N-methyl-2-pyrrolidinone (NMP) as a solvent, an electrode material for a lithium ion secondary battery, polyvinylidene fluoride (PVdF) as a binder, and acetylene black (AB) as a conductive auxiliary agent. In addition, electrode materials: AB: PVdF = 90: 5: 5 were added in a mass ratio in the paste, and these were mixed to prepare an electrode material paste for a lithium ion secondary battery.
Next, this electrode material paste for a lithium ion secondary battery is applied to the surface of an aluminum foil (current collector) having a thickness of 30 μm to form a coating film, the coating film is dried, and an electrode is formed on the surface of the aluminum foil. A mixture layer was formed. Thereafter, the electrode mixture layer was pressurized at a predetermined pressure so as to have a predetermined density, and the lithium ion secondary battery electrode of Example 1 was produced.
Next, this lithium ion secondary battery electrode was punched into a disk shape having a diameter of 16 mm using a molding machine, vacuum-dried, and using a 2016 coin cell made of stainless steel (SUS) in a dry argon atmosphere, A lithium ion secondary battery of Example 1 was produced.
Metal lithium was used as the negative electrode, a porous polypropylene film was used as the separator, and a 1M LiPF ₆ solution was used as the electrolyte. The LiPF ₆ solution used was a mixture of ethylene carbonate and ethylene carbonate so that the volume ratio was 1: 1.

"Evaluation of reaction product precipitates"
(1) X-ray diffraction A small amount of a sample was collected from the precipitate of the reaction product in a cake state, and this sample was vacuum dried at 70 ° C. for 2 hours to obtain a powder.
When this powder was identified using an X-ray diffractometer (trade name: X'Pert PRO MPS, manufactured by PANalytical, radiation source: CuKa), single-phase LiFe _0.20 Mn _0.79 Co _0.01 It was confirmed that PO ₄ was generated. Further, the crystal lattice constant and the lattice volume were calculated from the X-ray diffraction pattern of this powder. The evaluation results are shown in Table 2.

"Evaluation of electrode materials for lithium ion secondary batteries"
(1) Carbon content The carbon content in the electrode material for lithium ion secondary batteries was measured using a carbon analyzer (trade name: EMIA-220V, manufactured by HORIBA). The evaluation results are shown in Table 1.

(2) Specific surface area Using a specific surface area meter (trade name: BELSORP-mini, manufactured by Nippon Bell Co., Ltd.), the specific surface area of the electrode material for a lithium ion secondary battery was measured by the BET method using nitrogen (N ₂ ) adsorption. . The evaluation results are shown in Table 1.

(3) Average primary particle diameter A scanning electron microscope image obtained by observing an electrode material for a lithium ion secondary battery with a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation). From this, the average primary particle size of the electrode material for a lithium ion secondary battery was obtained. The evaluation results are shown in Table 1.

"Evaluation of lithium ion secondary battery"
(1) Activation energy of lithium ion insertion / release reaction Impedance of a lithium ion secondary battery was measured using an impedance analyzer (trade name: VersaSTAT4, manufactured by Princeton Applied Research).
In the impedance measurement, the frequency was in the range of 1 MHz to 0.1 mHz, and the semicircular arc appearing at a frequency of 100 Hz or less was defined as the resistance of the lithium ion insertion / desorption reaction occurring at the interface between the electrode active material and the carbonaceous film. This impedance measurement is performed at 30 ° C., 35 ° C., 40 ° C., 45 ° C., 50 ° C., 55 ° C., and the temperature dependence of the resistance of the lithium ion insertion / desorption reaction occurring at the interface between the electrode active material and the carbonaceous film. The activation energy of the lithium ion insertion / release reaction was calculated from the slope of the Arrhenius plot.
It can be said that a lithium ion insertion / extraction reaction is easier as a high-performance electrode active material. In this example, an activation energy of 55 kJ / mol or less was used as an index for non-defective products.
The evaluation results are shown in Table 2.

(2) Battery characteristics The battery characteristics of the lithium ion secondary battery were evaluated. At an ambient temperature of 25 ° C., constant current charging was performed at a current value of 0.1 CA until the positive electrode voltage was 4.3 V with respect to the Li equilibrium voltage. The constant voltage charge was performed until it became 01CA. Then, after resting for 1 minute, constant current discharge of 0.1 CA was performed at an environmental temperature of 25 ° C. or 0 ° C. until the positive electrode voltage was 2.0 V with respect to the Li equilibrium voltage. With this test, the discharge capacity and mass energy density (unit: Wh / kg) of the lithium ion secondary battery were evaluated. The mass energy density is represented by an integrated value of the discharge capacity and the discharge voltage, and is a value corresponding to the area when the discharge voltage is plotted on the vertical axis and the discharge capacity is plotted on the horizontal axis. When measured at 0 ° C., the discharge capacity and the discharge voltage are reduced as compared with the measurement at 25 ° C., and the mass energy density is reduced. Here, for example, even if the decrease in the discharge capacity is small, the mass energy density greatly decreases if the decrease in the discharge voltage is large. By using an electrode material excellent in electron conductivity, Li diffusibility, and activation energy of insertion / extraction reaction of lithium ions (Li ⁺ ) as obtained in this example, discharge capacity and discharge can be obtained even at 0 ° C. discharge. It is possible to suppress a decrease in both voltages and to suppress a decrease in mass energy density.

In this example, in order to obtain an electrode active material capable of exhibiting high performance under a low temperature environment, a non-defective product index is a 0.1 CA discharge capacity measured at 0 ° C. of 120 mAh / g or more. .
Further, in this example, in addition to the above index, in order to obtain an electrode active material capable of exhibiting performance comparable to normal temperature even in a low temperature environment, 0% of the 0.1 CA discharge capacity measured at 25 ° C. A good product index was a ratio of 0.1 CA discharge capacity measured at 0 ° C. of 80% or more.

Further, in this example, in order to obtain an electrode active material capable of exhibiting high performance under a low temperature environment, the non-defective product has a mass energy density of 450 Wh / kg or more at 0 ° C. and 0.1 CA discharge. It was used as an index.
Further, in this example, in addition to the above index, in order to obtain an electrode active material capable of exhibiting performance comparable to room temperature even in a low temperature environment, the mass energy density at 25 ° C. and 0.1 CA discharge is A non-defective index was a mass energy density ratio of 80% or more at 0 ° C. and 0.1 CA discharge.
The evaluation results are shown in Table 3.

[Example 2]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Were mixed at a molar ratio of Li: Fe: Mn: Co: P = 3: 0.22: 0.77: 0.01: 1 to prepare Example Slurry A, except that raw material slurry A was prepared. Similarly, the electrode material for a lithium ion secondary battery of Example 2 was synthesized.
Moreover, the lithium ion secondary battery of Example 2 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Example 2 was used.

[Example 3]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.22: 0.765: 0.015: 1. Similarly, the electrode material for a lithium ion secondary battery of Example 3 was synthesized.
Further, a lithium ion secondary battery of Example 3 was produced in the same manner as in Example 1 except that the electrode material for a lithium ion secondary battery of Example 3 was used.

[Example 4]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.25: 0.745: 0.005: 1. Similarly, the electrode material for a lithium ion secondary battery of Example 4 was synthesized.
Further, a lithium ion secondary battery of Example 4 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Example 4 was used.

[Example 5]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.25: 0.74: 0.01: 1. Similarly, the electrode material for a lithium ion secondary battery of Example 5 was synthesized.
Further, a lithium ion secondary battery of Example 5 was produced in the same manner as Example 1 except that the electrode material for the lithium ion secondary battery of Example 5 was used.

[Example 6]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. And Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.25: 0.735: 0.015: 1. Similarly, the electrode material for a lithium ion secondary battery of Example 6 was synthesized.
Further, a lithium ion secondary battery of Example 6 was produced in the same manner as in Example 1 except that the electrode material for a lithium ion secondary battery of Example 6 was used.

[Example 7]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.30: 0.695: 0.005: 1. Similarly, the electrode material for a lithium ion secondary battery of Example 7 was synthesized.
Moreover, the lithium ion secondary battery of Example 7 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Example 7 was used.

[Example 8]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Were mixed in a molar ratio such that Li: Fe: Mn: Co: P = 3: 0.30: 0.69: 0.01: 1 to prepare the raw material slurry A, and Example 1 Similarly, an electrode material for a lithium ion secondary battery of Example 8 was synthesized.
Further, a lithium ion secondary battery of Example 8 was produced in the same manner as Example 1 except that the electrode material for the lithium ion secondary battery of Example 8 was used.

[Example 9]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Were mixed at a molar ratio of Li: Fe: Mn: Co: P = 3: 0.30: 0.685: 0.015: 1 to prepare raw material slurry A, and Example 1 Similarly, the electrode material for a lithium ion secondary battery of Example 9 was synthesized.
Further, a lithium ion secondary battery of Example 9 was produced in the same manner as in Example 1 except that the electrode material for a lithium ion secondary battery of Example 9 was used.

[Example 10]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.35: 0.645: 0.005: 1. Similarly, an electrode material for a lithium ion secondary battery of Example 10 was synthesized.
Moreover, the lithium ion secondary battery of Example 10 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Example 10 was used.

[Example 11]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Were mixed at a molar ratio of Li: Fe: Mn: Co: P = 3: 0.35: 0.64: 0.01: 1 to prepare Example Slurry A, except that raw material slurry A was prepared. Similarly, an electrode material for a lithium ion secondary battery of Example 11 was synthesized.
Moreover, the lithium ion secondary battery of Example 11 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Example 11 was used.

[Example 12]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.35: 0.635: 0.015: 1. Similarly, the electrode material for a lithium ion secondary battery of Example 12 was synthesized.
Moreover, the lithium ion secondary battery of Example 12 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Example 12 was used.

[Example 13]
As _follows, it was synthesized _{LiFe 0.25 Mn 0.745 Co 0.010 Zn 0.005} PO 4.
Using Li ₃ PO ₄ as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution as the Fe source, Mn (NO ₃ ) ₂ aqueous solution as the Mn source, Co (NO ₃ ) ₂ aqueous solution as the Co source, Zn Zn (NO ₃ ) ₂ aqueous solution is used as a source, and these are in a molar ratio of Li: Fe: Mn: Co: Zn: P = 3: 0.25: 0.745: 0.010: 0.005: 1 Thus, 200 ml of raw material slurry A was prepared.
Thereafter, in the same manner as in Example 1, an electrode material for a lithium ion secondary battery of Example 13 was obtained.
Moreover, the lithium ion secondary battery of Example 13 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Example 13 was used.

[Comparative Example 1]
LiFe _0.250 Mn _0.750 PO ₄ was synthesized as follows.
Li ₃ PO ₄ is used as the Li source and P source, an Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, and an Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and these are molar ratios of Li: Fe: Mn: P = It mixed so that it might be set to 3: 0.25: 0.75: 1, and 200 ml of raw material slurry A was prepared.
Thereafter, in the same manner as in Example 1, a lithium ion secondary battery electrode material of Comparative Example 1 was obtained.
Further, a lithium ion secondary battery of Comparative Example 1 was produced in the same manner as Example 1 except that the electrode material for the lithium ion secondary battery of Comparative Example 1 was used.

[Comparative Example 2]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Comparative Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.40: 0.59: 0.01: 1. Similarly, the electrode material for a lithium ion secondary battery of Comparative Example 2 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 2 was produced in the same manner as Example 1 except that the electrode material for the lithium ion secondary battery of Comparative Example 2 was used.

[Comparative Example 3]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Comparative Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.18: 0.81: 0.01: 1. Similarly, the electrode material for the lithium ion secondary battery of Comparative Example 3 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 3 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Comparative Example 3 was used.

[Comparative Example 4]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Comparative Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.25: 0.73: 0.02: 1. Similarly, the electrode material for the lithium ion secondary battery of Comparative Example 3 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 4 was produced in the same manner as Example 1 except that the electrode material for lithium ion secondary batteries of Comparative Example 4 was used.

[Comparative Example 5]
Li ₃ PO ₄ is used as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution is used as the Fe source, Mn (NO ₃ ) ₂ aqueous solution is used as the Mn source, and Co (NO ₃ ) ₂ aqueous solution is used as the Co source. Comparative Example 1 except that the raw material slurry A was prepared by mixing Li in a molar ratio of Li: Fe: Mn: Co: P = 3: 0.25: 0.748: 0.002: 1. Similarly, the electrode material for the lithium ion secondary battery of Comparative Example 3 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 5 was produced in the same manner as Example 1 except that the electrode material for the lithium ion secondary battery of Comparative Example 5 was used.

[Comparative Example 6]
As _follows, it was synthesized _{LiFe 0.25 Mn 0.745 Ni 0.005 PO 4} .
Li ₃ PO ₄ as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution as the Fe source, Mn (NO ₃ ) ₂ aqueous solution as the Mn source, Ni (NO ₃ ) ₂ aqueous solution as the Ni source, These were mixed at a molar ratio of Li: Fe: Mn: Ni: P = 3: 0.25: 0.745: 0.005: 1 to prepare 200 ml of raw material slurry A.
Thereafter, in the same manner as in Example 1, a lithium ion secondary battery electrode material of Comparative Example 6 was obtained.
Further, a lithium ion secondary battery of Comparative Example 6 was produced in the same manner as in Example 1 except that the electrode material for lithium ion secondary batteries of Comparative Example 6 was used.

[Comparative Example 7]
Li ₃ PO ₄ as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution as the Fe source, Mn (NO ₃ ) ₂ aqueous solution as the Mn source, Ni (NO ₃ ) ₂ aqueous solution as the Ni source, Comparative Example 1 except that these were mixed at a molar ratio of Li: Fe: Mn: Ni: P = 3: 0.25: 0.745: 0.005: 1 to prepare the raw material slurry A. In the same manner, an electrode material for a lithium ion secondary battery of Comparative Example 7 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 7 was produced in the same manner as Example 1 except that the electrode material for lithium ion secondary batteries of Comparative Example 7 was used.

[Comparative Example 8]
Li ₃ PO ₄ as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution as the Fe source, Mn (NO ₃ ) ₂ aqueous solution as the Mn source, Ni (NO ₃ ) ₂ aqueous solution as the Ni source, Comparative Example 1 except that these were mixed at a molar ratio of Li: Fe: Mn: Ni: P = 3: 0.25: 0.735: 0.015: 1 to prepare the raw slurry A. In the same manner, an electrode material for a lithium ion secondary battery of Comparative Example 8 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 8 was produced in the same manner as in Example 1 except that the electrode material for the lithium ion secondary battery of Comparative Example 8 was used.

[Comparative Example 9]
As _follows, it was synthesized _{LiFe 0.25 Mn 0.745 Al 0.005 PO 4} .
Li ₃ PO ₄ as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution as the Fe source, Mn (NO ₃ ) ₂ aqueous solution as the Mn source, Al (NO ₃ ) ₃ aqueous solution as the Al source, These were mixed at a molar ratio of Li: Fe: Mn: Al: P = 3: 0.25: 0.745: 0.005: 1 to prepare 200 ml of raw material slurry A.
Thereafter, in the same manner as in Example 1, a lithium ion secondary battery electrode material of Comparative Example 9 was obtained.
Further, a lithium ion secondary battery of Comparative Example 9 was produced in the same manner as Example 1 except that the electrode material for the lithium ion secondary battery of Comparative Example 9 was used.

[Comparative Example 10]
Li ₃ PO ₄ as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution as the Fe source, Mn (NO ₃ ) ₂ aqueous solution as the Mn source, Al (NO ₃ ) ₃ aqueous solution as the Al source, Comparative Example 1 except that these were mixed at a molar ratio of Li: Fe: Mn: Al: P = 3: 0.25: 0.74: 0.01: 1 to prepare the raw material slurry A. In the same manner, an electrode material for a lithium ion secondary battery of Comparative Example 10 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 10 was produced in the same manner as in Example 1 except that the electrode material for lithium ion secondary batteries of Comparative Example 10 was used.

[Comparative Example 11]
Li ₃ PO ₄ as the Li source and P source, Fe (NO ₃ ) ₂ aqueous solution as the Fe source, Mn (NO ₃ ) ₂ aqueous solution as the Mn source, Al (NO ₃ ) ₃ aqueous solution as the Al source, Comparative Example 1 except that these were mixed at a molar ratio of Li: Fe: Mn: Al: P = 3: 0.25: 0.735: 0.015: 1 to prepare the raw material slurry A. In the same manner, an electrode material for a lithium ion secondary battery of Comparative Example 11 was synthesized.
Further, a lithium ion secondary battery of Comparative Example 11 was produced in the same manner as Example 1 except that the electrode material for the lithium ion secondary battery of Comparative Example 11 was used.

"Evaluation of reaction product precipitates"
(1) X-ray diffraction The reaction product precipitates of Examples 2 to 13 and Comparative Examples 1 to 11 were identified in the same manner as in Example 1.
As a result, in Example 2, it was confirmed that single-phase LiFe _0.22 Mn _0.77 Co _0.01 PO ₄ was generated.
In Example 3, it was confirmed that single-phase LiFe _0.22 Mn _0.765 Co _0.015 PO ₄ was formed.
In Example 4, it was confirmed that single-phase LiFe _0.25 Mn _0.745 Co _0.005 PO ₄ was formed.
In Example 5, it was confirmed that single-phase LiFe _0.25 Mn _0.74 Co _0.01 PO ₄ was formed.
In Example 6, it was confirmed that single-phase LiFe _0.25 Mn _0.735 Co _0.015 PO ₄ was formed.
In Example 7, it was confirmed that single-phase LiFe _0.30 Mn _0.695 Co _0.005 PO ₄ was formed.
In Example 8, it was confirmed that single-phase LiFe _0.30 Mn _0.69 Co _0.01 PO ₄ was formed.
In Example 9, it was confirmed that single-phase LiFe _0.30 Mn _0.685 Co _0.015 PO ₄ was formed.
In Example 10, it was confirmed that single-phase LiFe _0.30 Mn _0.645 Co _0.005 PO ₄ was formed.
In Example 11, it was confirmed that single-phase LiFe _0.35 Mn _0.64 Co _0.01 PO ₄ was formed.
In Example 12, it was confirmed that single-phase LiFe _0.35 Mn _0.635 Co _0.015 PO ₄ was formed.
In Example 13, it was confirmed that single-phase LiFe _0.25 Mn _0.735 Co _0.010 Zn _0.005 PO ₄ was formed.

On the other hand, in Comparative Example 1, it was confirmed that LiFe _0.25 Mn _0.75 PO ₄ was generated.
In Comparative Example 2, it was confirmed that LiFe _0.40 Mn _0.59 Co _0.01 PO ₄ was generated.
In Comparative Example 3, it was confirmed that LiFe _0.18 Mn _0.81 Co _0.01 PO ₄ was generated.
In Comparative Example 4, it was confirmed that LiFe _0.25 Mn _0.73 Co _0.02 PO ₄ was generated.
In Comparative Example 5, it was confirmed that LiFe _0.25 Mn _0.748 Co _0.002 PO ₄ was generated.
In Comparative Example 6, it was confirmed that LiFe _0.25 Mn _0.745 Ni _0.005 PO ₄ was generated.
In Comparative Example 7, it was confirmed that LiFe _0.25 Mn _0.74 Ni _0.01 PO ₄ was generated.
In Comparative Example 8, it was confirmed that LiFe _0.25 Mn _0.735 Ni _0.015 PO ₄ was generated.
In Comparative Example 9, it was confirmed that LiFe _0.25 Mn _0.745 Al _0.005 PO ₄ was generated.
In Comparative Example 10, it was confirmed that LiFe _0.25 Mn _0.74 Al _0.01 PO ₄ was generated.
In Comparative Example 11, it was confirmed that LiFe _0.25 Mn _0.735 Al _0.015 PO ₄ was generated.
Moreover, the crystal lattice constant was computed from the X-ray-diffraction figure of the precipitate of the reaction product of Examples 2-13 and Comparative Examples 1-11. The evaluation results are shown in Table 2.

(2) Lattice Volume In the same manner as in Example 1, the lattice volume of the precipitates of the reaction products of Examples 2 to 13 and Comparative Examples 1 to 11 was calculated. The evaluation results are shown in Table 2.

"Evaluation of electrode materials for lithium ion secondary batteries"
(1) Carbon loading amount In the same manner as in Example 1, the carbon loading amount in the electrode materials for lithium ion secondary batteries of Examples 2 to 13 and Comparative Examples 1 to 11 was measured. The evaluation results are shown in Table 1.

(2) Specific surface area It carried out similarly to Example 1, and measured the specific surface area of the electrode material for lithium ion secondary batteries of Examples 2-13 and Comparative Examples 1-11. The evaluation results are shown in Table 1.

(3) Average primary particle diameter It carried out similarly to Example 1, and obtained the average primary particle diameter of the electrode material for lithium ion secondary batteries of Examples 2-13 and Comparative Examples 1-11. The evaluation results are shown in Table 1.

"Evaluation of lithium ion secondary battery"
(1) Activation energy of lithium ion insertion / desorption reaction In the same manner as in Example 1, the impedances of the lithium ion secondary batteries of Examples 2 to 13 and Comparative Examples 1 to 11 were measured, and lithium ion insertion / desorption was performed. The activation energy of the separation reaction was calculated. The evaluation results are shown in Table 1.

(2) Battery characteristics The battery characteristics of the lithium ion secondary batteries of Examples 2 to 13 and Comparative Examples 1 to 11 were evaluated in the same manner as Example 1. The evaluation results are shown in Table 3.

  From the results of Tables 1 to 3, when Examples 1 to 13 and Comparative Examples 1 to 11 are compared, the lithium ion secondary batteries of Examples 1 to 13 correspond to the 0.1 CA discharge capacity measured at 25 ° C. The ratio of 0.1 CA discharge capacity measured at 0 ° C. is 80% or more, the 0.1 CA discharge capacity measured at 0 ° C. is 120 mAh / g or more, and at 25 ° C. and 0.1 CA discharge The ratio of the mass energy density at 0 ° C. and 0.1 CA discharge to the mass energy density at 80 ° C. and the mass energy density at 0 ° C. and 0.1 CA discharge is 450 Wh / kg or more. In charge / discharge, it was confirmed that the discharge capacity and mass energy density were high.

  On the other hand, in the lithium ion secondary batteries of Comparative Examples 1 to 11, the ratio of the 0.1 CA discharge capacity measured at 0 ° C. to the 0.1 CA discharge capacity measured at 25 ° C. is less than 80% and measured at 0 ° C. The ratio of the mass energy density at 0 ° C. and 0.1 CA discharge to the mass energy density at 25 ° C. and 0.1 CA discharge is less than 80% at 0 ° C. Since the mass energy density in 0.1 CA discharge satisfies at least one of 450 Wh / kg or less, it was confirmed that the discharge capacity and the mass energy density were low at low temperature and high speed charge / discharge.

Further, regarding the solid solution amount of Fe, when x is less than 0.22, the result of Comparative Example 3 is seen, the charge / discharge capacity at 0 ° C. is 111.5 mAh / g, and the charge / discharge capacity at 25 ° C. is 139.6 mAh / g. The characteristics were lower than the criteria.
In addition, when the result of Comparative Example 2 is seen assuming that x exceeds 0.35, the 0 ° C. energy density is 441.4 Wh / kg, and the 25 ° C. energy density is 539.2 Wh / kg. It was.
On the other hand, in the case where the solid solution amount of Fe was included in the range of 0.220 ≦ x ≦ 0.350, the charge / discharge capacity and the energy density both exceeded the criterion.

Further, regarding the solid solution amount of Co, the activation energy is 57.34 kJ / mol when y is less than 0.005, and it matches the criterion of “55 kJ / mol or less”. It became a characteristic that does not.
Further, when the result of Comparative Example 4 is seen assuming that y exceeds 0.018, the 0 ° C. energy density is 441.8 Wh / kg, and the 25 ° C. energy density is 544.4 Wh / kg. It was.
On the other hand, when the solid solution amount of Co and Zn was included in the range of 0.005 ≦ y ≦ 0.018, the activation energy and the energy density both exceeded the criterion.

  From the above, it was confirmed that the present invention is useful.

The electrode material for a lithium ion secondary battery of the present invention has an electrode activity made of LiFe _x Mn _{1- xy My} PO ₄ (0.220 ≦ x ≦ 0.350, 0.005 ≦ y ≦ 0.018). M is Co alone or both Co and Zn, and the electrode active material has an orthorhombic crystal structure, a space group of Pnma, and values of crystal lattice constants a, b, and c. Satisfies 10.28Å ≦ a ≦ 10.42Å, 6.000Å ≦ b ≦ 6.069Å, 4.710Å ≦ c ≦ 4.728Å, and the lattice volume V satisfies 289.00Å ³ ≦ V ≦ 298.23Å ³ . The lithium ion secondary battery equipped with the lithium ion secondary battery electrode manufactured using this lithium ion secondary battery electrode material has high discharge capacity and high mass energy density at low temperature and high speed charge / discharge. , It can also be applied to next-generation secondary batteries that are expected to have higher voltage, higher energy density, higher load characteristics, and faster charge / discharge characteristics. It is very big.

Claims (4)

A positive electrode material for a lithium ion secondary battery comprising an electrode active material made of LiFe _x Mn _{1- xy My} PO ₄ (0.220 ≦ x ≦ 0.350, 0.005 ≦ y ≦ 0.018). And
Said M is only Co or both Co and Zn,
The electrode active material has a crystal structure space group Pnma, and crystal lattice constants a, b, and c have values of 10.28Å ≦ a ≦ 10.42Å, 6.000Å ≦ b ≦ 6.069Å, and 4.710Å. met ≦ c ≦ 4.728Å, lattice volume V is less than the 289.00Å ³ ≦ V ≦ 298.23Å ^3,
The surface of the electrode active material is coated with a carbonaceous film, and the activation energy of the lithium ion insertion / desorption reaction occurring at the interface between the electrode active material and the carbonaceous film is 55 kJ / mol or less. A positive electrode material for a lithium ion secondary battery. The ratio of 0.1 CA discharge capacity measured at 0 ° C. to 0.1 CA discharge capacity measured at 25 ° C. is 80% or more, and 0.1 CA discharge capacity measured at 0 ° C. is 120 mAh / g or more. Yes,
2. The lithium ion secondary battery according to claim 1, wherein a ratio of mass energy density at 0 ° C. and 0.1 CA discharge to mass energy density at 25 ° C. and 0.1 CA discharge is 80% or more. Positive electrode material. A positive electrode for a lithium ion secondary battery comprising: an electrode current collector; and an electrode mixture layer formed on the electrode current collector,
It said electrode mixture layer, according to claim 1 or 2 lithium ion secondary battery positive electrode characterized by containing a positive electrode material for lithium ion secondary battery according to. A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to claim 3 .