JP6960081B2 - Positive electrode active material for lithium ion secondary batteries - Google Patents

Description

The present invention relates to a positive electrode active material for a lithium ion secondary battery.

Lithium-ion secondary batteries are lighter in weight and have a higher energy density than existing batteries, and have been used in recent years as so-called portable power sources for personal computers and mobile terminals and power sources for driving vehicles. Lithium-ion secondary batteries are expected to become more and more popular in the future as high-output power sources for driving vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs). There is.

Lithium-ion secondary batteries used in high-power power sources for driving vehicles are required to have higher performance, and higher energy density is being pursued as part of the higher performance. One measure for increasing the energy density of the lithium ion secondary battery is to use a positive electrode active material having a high operating potential (high potential positive electrode active material).

As a typical positive electrode active material having a high working potential, a lithium nickel-manganese-based composite oxide having a spinel-type crystal structure containing Li, Ni, and Mn as major constituent metal elements is known. It is known that in a lithium ion secondary battery, the non-aqueous electrolytic solution is decomposed, which causes deterioration of the battery capacity. The decomposition of this non-aqueous electrolytic solution tends to occur as the working potential of the positive electrode active material increases. Therefore, in Patent Document 1, the surface of the lithium nickel-manganese-based composite oxide having a spinel-type crystal structure is coated with a lithium metal phosphor oxide having an olivine-type crystal structure so that the capacity deterioration of the lithium ion secondary battery can be suppressed. A positive electrode active material having a (coated) core-shell structure has been proposed.

Japanese Unexamined Patent Publication No. 2013-191540

However, as a result of diligent studies by the present inventor, according to Patent Document 1, a positive electrode active material having a core-shell structure in which the surface of a spinel-type lithium nickel-manganese-based composite oxide is coated with an olivine-type lithium metal phosphor oxide. , Although it is possible to suppress the capacity deterioration of the lithium ion secondary battery, it has been found that there is a problem that the battery resistance increases.

Therefore, the present invention presents a positive electrode active material for a lithium ion secondary battery having a core-shell structure in which the surface of a lithium nickel-manganese-based composite oxide having a spinel-type crystal structure is coated with a lithium metal phosphor oxide having an olivine-type crystal structure. An object of the present invention is to provide a positive electrode active material for a lithium ion secondary battery, which can suppress capacity deterioration of the lithium ion secondary battery and reduce battery resistance.

The positive electrode active material for a lithium ion secondary battery disclosed herein has a core portion and a shell portion that covers the core portion. The core portion is Li _{1 + x} Ni _0.5 Mn _1.5 O ₄ (in the formula, x is a value satisfying 0.05 ≦ x ≦ 0.3, and some of Ni and Mn are Mg, Zn, It may be substituted with at least one metal element selected from the group consisting of Co, Fe, Cr, Al, Ti, Zr, Nb, Ta, Ru, and W, and may be substituted with F ⁻ , Cl ⁻ , and N ^3-. It is composed of a composite oxide having a composition represented by (may be doped with at least one anion selected from the group consisting of) and having a spinel-type crystal structure. The shell portion is Li _{1 + y} MPO ₄ (in the formula, y is a value satisfying 0.05 ≦ y ≦ 0.3, and M is at least one selected from the group consisting of Fe, Mn, Ni, and Co. Even if a part of M is replaced with at least one metal element selected from the group consisting of Mg, Zn, Cr, Al, Ti, Zr, Nb, Ta, Ru, and W. A phosphor oxide having a composition represented by (may be doped with at least one anion selected from the group consisting of F ⁻ , Cl ⁻ , and N ^{3-) and having an olivine type crystal structure.} It is composed of

According to such a configuration, since both the core portion and the shell portion have an excess Li composition, the movement of lithium ions at the interface between the core portion and the shell portion when the lithium ion secondary battery is charged and discharged is easy. Therefore, the battery resistance can be reduced. In addition, the core-shell structure maintains the effect of suppressing capacity deterioration of the lithium-ion secondary battery. That is, according to such a configuration, there is provided a positive electrode active material for a lithium ion secondary battery that can suppress capacity deterioration of the lithium ion secondary battery and reduce battery resistance.

It is sectional drawing which shows typically the structure of the positive electrode active material for a lithium ion secondary battery which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the structure of the lithium ion secondary battery constructed by using the positive electrode active material for the lithium ion secondary battery which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the winding electrode body of the lithium ion secondary battery constructed by using the positive electrode active material for a lithium ion secondary battery which concerns on one Embodiment of this invention.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, general constitution of a positive electrode active material for a lithium ion secondary battery which does not characterize the present invention). Can be grasped as a design matter of a person skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art. Further, in the following drawings, members / parts having the same action are described with the same reference numerals. Further, the dimensional relations (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relations.

As shown in FIG. 1, the positive electrode active material 10 for a lithium ion secondary battery according to the present embodiment has a core portion 12 and a shell portion 14 that covers the core portion 12. That is, it has a core-shell structure. Although the positive electrode active material 10 has a spherical shape in FIG. 1, the shape of the positive electrode active material 10 is not limited to this, and may be non-spherical such as an amorphous shape.

The core portion 12 has Li _{1 + x} Ni _0.5 Mn _1.5 O ₄ (in the formula, x is a value satisfying 0.05 ≦ x ≦ 0.3, and some of Ni and Mn are Mg, Zn, It may be substituted with at least one metal element selected from the group consisting of Co, Fe, Cr, Al, Ti, Zr, Nb, Ta, Ru, and W, and may be substituted with F ⁻ , Cl ⁻ , and N ^3-. It is composed of a composite oxide having a composition represented by (may be doped with at least one anion selected from the group consisting of) and having a spinel-type crystal structure. By using a lithium nickel-manganese-based composite oxide having a spinel structure having such a composition in the core portion 12 of the positive electrode active material 10, the operating potential of the positive electrode active material 10 is increased, and 4.5 V (vs. Li / Li) is increased. ⁺ ) Can show an operating potential of greater than or equal to.
The amount of the metal element that partially replaces Ni and Mn is preferably 0.2 mol or less, more preferably 0.15 mol or less, with respect to 1 mol of the composite oxide having a spinel-type crystal structure. ..
The doping amount of the anion is, for example, 0.1 mol or less with respect to 1 mol of the composite oxide having a spinel-type crystal structure.

The shell portion 14 is Li _{1 + y} MPO ₄ (in the formula, y is a value satisfying 0.05 ≦ y ≦ 0.3, and M is at least one selected from the group consisting of Fe, Mn, Ni, and Co. Even if a part of M is replaced with at least one metal element selected from the group consisting of Mg, Zn, Cr, Al, Ti, Zr, Nb, Ta, Ru, and W. A phosphor oxide having a composition represented by (may be doped with at least one anion selected from the group consisting of F ⁻ , Cl ⁻ , and N ^{3-) and having an olivine type crystal structure.} It is composed of By using a lithium metal phosphor oxide having an olivine-type crystal structure having such a composition, deterioration of the battery capacity of the lithium ion secondary battery can be suppressed.
The amount of the metal element substituting a part of M is preferably 0.2 mol or less, more preferably 0.15 mol or less, with respect to 1 mol of the phosphor oxide having an olivine type crystal structure.
The doping amount of the anion is, for example, 0.1 mol or less with respect to 1 mol of the phosphor oxide having an olivine type crystal structure.

In the positive electrode active material 10 according to the present embodiment, x satisfies 0.05 ≦ x ≦ 0.3 in the core portion 12, and y is 0.05 ≦ y ≦ 0 in the shell portion 14. It satisfies 3. That is, both the core portion 12 and the shell portion 14 have a composition in which Li is excessive.
In the conventional core-shell type positive electrode active material, neither the core portion nor the shell portion has an excess Li composition.
However, like the positive electrode active material 10 according to the present embodiment, both the core portion 12 and the shell portion 14 have a composition in which Li is excessive, so that the battery resistance of the lithium ion secondary battery can be reduced. Can be done. This is because both the core portion 12 and the shell portion 14 have a composition in which Li is excessive, so that the lithium ions at the interface between the core portion 12 and the shell portion 14 when the lithium ion secondary battery is charged and discharged It is thought that this is due to the ease of movement.

From the viewpoint of further suppressing capacity deterioration and further reducing battery resistance, x and y satisfy 0.07 ≦ x ≦ 0.23 and 0.07 ≦ y ≦ 0.23 in the above composition formula. It is preferable, and it is more preferable to satisfy 0.10 ≦ x ≦ 0.20 and 0.10 ≦ y ≦ 0.20.

The average particle size of the positive electrode active material 10 according to the present embodiment is preferably 2 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. In the present specification, the "average particle size" means a _{particle size (D 50} ) corresponding to a cumulative 50% in a volume-based particle size distribution based on a general laser diffraction / light scattering method. Therefore, the positive electrode active material 10 may exist in the form of primary particles or may form secondary particles.

In the positive electrode active material 10 according to the present embodiment, the shell portion 14 has a coating layer that covers the core portion 12 as a whole (particularly uniformly), as shown in FIG. 1, rather than partially covering the core portion 12. It is preferably formed. The thickness of the shell portion 14 of the positive electrode active material 10 according to the present embodiment is preferably 100 nm or less (particularly 10 nm or more and 100 nm or less).

In the positive electrode active material 10 according to the present embodiment, the coverage of the shell portion 14 is preferably 70 atm% or more as a percentage (atm%) of the atomic ratio represented by P / (Ni + Mn + P). The percentage (atm%) of the ratio can be obtained by quantifying each element by XPS analysis.

The positive electrode active material 10 according to the present embodiment can be produced, for example, by the method described below. The positive electrode active material 10 according to the present embodiment is not limited to the one produced by the method described below.

First, core particles composed of a lithium nickel-manganese-based composite oxide having a spinel structure to be the core portion 12 are produced. Core particles can be prepared according to a conventional method.
Specifically, for example, a composite water containing nickel and manganese in a molar ratio of 0.5: 1.5 using an aqueous solution of a nickel salt, a manganese salt, and an alkaline compound (eg, sodium hydroxide) by a crystallization method. Oxide particles are prepared as precursor particles.
The precursor particles are then mixed with the lithium salt. At this time, Li contained in the lithium salt is added so as to be 1.05 mol or more and 1.3 mol or less with respect to 1 mol of the precursor particles. Then, the obtained mixture can be calcined to form core particles composed of a lithium nickel-manganese-based composite oxide having a spinel structure.
The shell portion 14 can be formed by coating the surface of the core particles with a lithium metal phosphor oxide.
Specifically, for example, the target can be formed by using the lithium metal phosphorylate having an excess Li composition, which is a material constituting the shell portion, and sputtering the core particles while rotating them.
Metal elements other than Li, Ni, and Mn and anions (F ⁻ , Cl ⁻ , and N ^3- ) can be added according to a known doping method.
In this way, the positive electrode active material 10 according to the present embodiment can be obtained.

The positive electrode active material 10 according to the present embodiment is for a lithium ion secondary battery, and the lithium ion secondary battery provided with the positive electrode active material 10 has both suppression of capacity deterioration and reduction of battery resistance. It becomes. Hereinafter, a configuration example of the lithium ion secondary battery 100 using the positive electrode active material 10 according to the present embodiment will be described with reference to the drawings.
In the present specification, the "secondary battery" generally refers to a power storage device capable of being repeatedly charged and discharged, and is a term including a so-called storage battery and a power storage element such as an electric double layer capacitor.
As used herein, the term "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and realizes charging and discharging by transferring charges associated with the lithium ions between the positive and negative electrodes.

The lithium ion secondary battery 100 shown in FIG. 2 is constructed by housing a flat wound electrode body 20 and a non-aqueous electrolyte (not shown) in a flat square battery case (that is, an outer container) 30. It is a closed type lithium ion secondary battery 100. The battery case 30 is provided with a positive electrode terminal 42 and a negative electrode terminal 44 for external connection, and a thin-walled safety valve 36 set to release the internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. Has been done. The positive and negative electrode terminals 42 and 44 are electrically connected to the positive and negative electrode current collector plates 42a and 44a, respectively. As the material of the battery case 30, for example, a lightweight metal material having good thermal conductivity such as aluminum is used.

In the wound electrode body 20, as shown in FIGS. 2 and 3, a positive electrode active material layer 54 is formed along the longitudinal direction on one side or both sides (here, both sides) of the elongated positive electrode current collector 52. The positive electrode sheet 50 and the negative electrode sheet 60 in which the negative electrode active material layer 64 is formed along the longitudinal direction on one side or both sides (here, both sides) of the long negative electrode current collector 62 are formed in two long shapes. It is overlapped with each other via the separator sheet 70 of the above and wound in the longitudinal direction. The positive electrode active material layer non-formed portion 52a (that is, the positive electrode) formed so as to protrude outward from both ends of the winding electrode body 20 in the winding axis direction (referring to the sheet width direction orthogonal to the longitudinal direction). A portion where the positive electrode current collector 52 is exposed without forming the active material layer 54) and a portion 62a where the negative electrode active material layer is not formed (that is, a portion where the negative electrode current collector 62 is exposed without forming the negative electrode active material layer 64). ) Are joined to a positive electrode current collector plate 42a and a negative electrode current collector plate 44a, respectively.

Examples of the positive electrode current collector 52 constituting the positive electrode sheet 50 include aluminum foil and the like. The positive electrode active material layer 54 contains the positive electrode active material 10 for a lithium ion secondary battery according to the above-described embodiment. Further, the positive electrode active material layer 54 may further contain a conductive material, a binder and the like. As the conductive material, for example, carbon black such as acetylene black (AB) or other carbon material (graphite or the like) can be preferably used. As the binder, for example, polyvinylidene fluoride (PVDF) or the like can be used.

Examples of the negative electrode current collector 62 constituting the negative electrode sheet 60 include copper foil and the like. The negative electrode active material layer 64 contains a negative electrode active material. As the negative electrode active material, a carbon material such as graphite, hard carbon, or soft carbon can be used. The negative electrode active material layer 64 may further contain a binder, a thickener, and the like. As the binder, for example, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF) and the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like can be used.

As the separator 70, various microporous sheets similar to those conventionally used for lithium ion secondary batteries can be used. For example, a microporous resin made of a resin such as polyethylene (PE) or polypropylene (PP). The sheet can be mentioned. The microporous resin sheet may have a single-layer structure or a multi-layer structure having two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of the PE layer). The separator 70 may include a heat resistant layer (HRL).

As the non-aqueous electrolyte, the same one as that of the conventional lithium ion secondary battery can be used, and typically, an organic solvent (non-aqueous solvent) containing a supporting salt can be used. As the non-aqueous solvent, aprotic solvents such as carbonates, esters and ethers can be used. Among them, carbonates, for example, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like can be preferably adopted. Alternatively, a fluorinated solvent such as a fluorinated carbonate such as monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC), or trifluorodimethyl carbonate (TFDMC) is preferably used. be able to. As such a non-aqueous solvent, one type can be used alone, or two or more types can be used in combination as appropriate. As the supporting salt, for example, _{lithium salts such as LiPF 6} , LiBF ₄ , and LiClO ₄ can be preferably used. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less.
The non-aqueous electrolyte contains various components other than the above-mentioned non-aqueous solvent and supporting salt, such as a gas generator, a film-forming agent, a dispersant, and a thickener, as long as the effects of the present invention are not significantly impaired. May include additives.

The lithium ion secondary battery 100 can be used for various purposes. Suitable applications include drive power supplies mounted on vehicles such as plug-in hybrid vehicles (PHVs), hybrid vehicles (HVs), and electric vehicles (EVs). The lithium ion secondary battery 100 can also be used in the form of an assembled battery in which a plurality of lithium ion secondary batteries 100 are electrically connected.

As described above, a square lithium ion secondary battery provided with a flat wound electrode body has been described as an example. However, the positive electrode active material according to the present embodiment can also be used for other types of lithium ion secondary batteries according to a known method. For example, a lithium ion secondary battery including a laminated electrode body can be constructed by using the positive electrode active material according to the present embodiment. Further, a cylindrical lithium ion secondary battery, a laminated lithium ion secondary battery, or the like can also be constructed by using the positive electrode active material according to the present embodiment.

Hereinafter, examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in such examples.

<No. Preparation of 1 to 15 positive electrode active materials>
An aqueous nickel sulfate solution and an aqueous manganese sulfate solution were mixed in the reaction vessel so as to have a molar ratio of Ni / Mn = 0.5 / 1.5. At this time, an aqueous sodium hydroxide solution was added to adjust the pH of the mixture so that the pH would be 11-12.
The resulting precipitate was filtered and dried to give composite hydroxide precursor particles.
The obtained precursor particles and lithium hydroxide were mixed. At this time, Li, Ni, and Mn were mixed so as to have a molar ratio of the compositions shown in Tables 1 and 2.
The obtained mixture was calcined at 900 ° C. for 12 hours and then further calcined at 600 ° C. for 36 hours to prepare core particles composed of a lithium nickel-manganese-based composite oxide having a spinel structure as a core portion. In addition, No. Regarding the positive electrode active material, the particles obtained here were used as they were as the positive electrode active material.
Subsequently, _Li 1 + y FePO ₄ to the target (in the formula, y is a value shown in Table 1), using a _Li 1.1 FePO ₄ and _Li 1.1 MnPO ₄ in consideration of Table 2, rotates the core particles By sputtering while sputtering, a uniform coating layer (that is, a shell portion) was formed on the surface of the core particles. A direct current was used for the sputtering, and the film formation rate was 1 nm / h. In the examination of Table 1, the sputter time was adjusted so that the coating thickness of the coating layer was 10 nm, and in the examination of Table 2, the coating layer had the coating thickness shown in Table 2.
In this way, No. 2-No. A positive electrode active material having a core-shell structure having a core portion composed of a lithium nickel-manganese-based composite oxide having a spinel structure of 15 and a shell portion composed of a lithium metal phosphorus oxide having an olivine-type crystal structure was obtained.
Further, in the examination of Table 2, the percentage of the atomic ratio represented by P / (Ni + Mn + P) as the coverage (atm%) was determined by element quantification by XPS analysis.

<Manufacturing of lithium-ion secondary battery for evaluation>
No. 1 prepared above. 1-No. Fifteen positive electrode active materials, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder are N-methyl in a mass ratio of positive electrode active material: AB: PVDF = 90: 5: 5. It was mixed with pyrrolidone to prepare a slurry for forming a positive electrode active material layer having a solid content concentration of 55%. This slurry for forming a positive electrode active material layer ^{was applied to an aluminum foil at a basis weight of 10 mg / cm 2} and dried at 120 ° C. to prepare a positive electrode sheet.
Further, natural graphite as a negative electrode active material and polyvinylidene fluoride (PVDF) as a binder are mixed with N-methylpyrrolidone at a mass ratio of natural graphite: PVDF = 95: 5, and the solid content concentration is 55%. A slurry for forming the negative electrode active material layer was prepared. This slurry for forming a negative electrode active material layer ^{was applied to a copper foil at a basis weight of 5 mg / cm 2} and dried at 120 ° C. to prepare a negative electrode sheet.
Further, a porous polyolefin sheet having a three-layer structure of PP / PE / PP was prepared as a separator.
The prepared positive electrode sheet and the negative electrode sheet were opposed to each other via a separator to prepare an electrode body.
A lithium ion secondary battery for evaluation was obtained by attaching a current collector to the prepared electrode body, housing it in a laminate case together with a non-aqueous electrolyte solution, and sealing it. _{As the non-aqueous electrolytic solution, a solution in which LiPF 6} was dissolved in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 50:50 at a concentration of 1 mol / L was used.

<Conditioning>
Each evaluation lithium ion secondary battery was placed in an environment of 25 ° C., charged at a constant current of 4.9 V at 1 C, and then discharged at a constant current of 3.5 V at 1 C for 3 cycles. At this time, the discharge capacity at the time of discharging in the third cycle was measured.

<IV resistance measurement>
After conditioning (discharged), each evaluation lithium-ion secondary battery is charged to 55% of the discharge capacity in the third cycle (that is, adjusted to SOC 55%), and is charged at 5 C for 10 seconds in an environment of 25 ° C. , Constant current (CC) discharge was performed. At this time, the IV resistance was calculated according to the following formula.
IV resistance (Ω) = ΔV / I
No. No. 1 when the IV resistance of the evaluation lithium ion secondary battery using the positive electrode active material of 1 was set to 1. 2-No. The ratio of IV resistance of the evaluation lithium ion secondary battery using 15 positive electrode active materials was determined. The results are shown in Tables 1 and 2.

<Charge / discharge cycle test>
Each evaluation lithium ion secondary battery was placed in an environment of 50 ° C., charged at a constant current of 4.9 V at 1 C, and then discharged at a constant current of 3.5 V at 1 C for 100 cycles. At this time, the discharge capacity in the first charge / discharge cycle and the discharge capacity in the 100th charge / discharge cycle were measured. The capacity deterioration rate was calculated according to the following formula.
Capacity deterioration rate (%) = (Discharge capacity in the first charge / discharge cycle-Discharge capacity in the 100th charge / discharge cycle) / Discharge capacity in the first charge / discharge cycle x 100
No. No. 1 when the capacity deterioration rate of the evaluation lithium ion secondary battery using the positive electrode active material of 1 was set to 1. 2-No. The ratio of the capacity deterioration rate of the evaluation lithium ion secondary battery using 15 positive electrode active materials was determined. The results are shown in Tables 1 and 2.

No. Reference numeral 1 denotes a positive electrode active material having no shell (a single lithium nickel-manganese-based composite oxide having a spinel structure). No. 2 has a core-shell structure, which corresponds to the prior art, but both the core portion (lithium nickel-manganese-based composite oxide having a spinel structure) and the shell portion (lithium metal phosphorus oxide having an olivine-type crystal structure) have an excess of Li. It is a positive electrode active material having no composition (that is, x = 0, y = 0). No. 1 and No. Compared with 2, the positive electrode active material having a core-shell structure with a conventional structure in which neither the core part nor the shell part has an excess Li composition can suppress the capacity deterioration of the lithium ion secondary battery, while the battery resistance. It turns out that becomes higher. Furthermore, No. 3 and No. From the result of No. 4, it can be seen that even if only one of the core portion and the shell portion has an excess Li composition, the capacity deterioration of the lithium ion secondary battery can be suppressed, but the battery resistance becomes high.
On the other hand, No. 5-No. From the result of No. 11, the positive electrode activity in which both the core portion and the shell portion have a Li-excessive composition (at least x and y satisfy 0.05 ≦ x ≦ 0.3 and 0.05 ≦ y ≦ 0.3). According to the material, not only the capacity deterioration of the lithium ion secondary battery can be suppressed as in the conventional technology, but also the battery resistance of the lithium ion secondary battery can be reduced to 1/2 or less as compared with the conventional technology. You can see that there is.

In addition, No. 5 and No. 12 to No. From the result of No. 14, when the coat thickness (thickness of the shell portion) is increased, the capacity deterioration can be further suppressed, but the battery resistance tends to increase. No. From the results of No. 15, it can be seen that even if the type of metal element of the lithium metal phosphor oxide having an olivine type crystal structure is changed, it is possible to suppress the capacity deterioration of the lithium ion secondary battery and reduce the battery resistance.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

10 Positive electrode active material 12 Core part 14 Shell part 20 Winding electrode body 30 Battery case 36 Safety valve 42 Positive electrode terminal 42a Positive electrode current collector 44 Negative electrode terminal 44a Negative electrode current collector plate 50 Positive electrode sheet (positive electrode)
52 Positive electrode current collector 52a Positive electrode active material layer non-formed portion 54 Positive electrode active material layer 60 Negative electrode sheet (negative electrode)
62 Negative electrode current collector 62a Negative electrode active material layer non-formed portion 64 Negative electrode active material layer 70 Separator sheet (separator)
100 lithium ion secondary battery

Claims (1)

A positive electrode active material for a lithium ion secondary battery having a core portion and a shell portion covering the core portion.
The core _{portion, Li 1 + x Ni 0.5 Mn} 1.5 O 4 ( wherein, x is a value der Ru satisfying 0.05 ≦ x ≦ 0.3) having a composition represented by, and spinel It is a composite oxide having a type crystal structure, and is composed of a composite oxide doped with at least one anion selected from the group consisting of F ⁻ , Cl ⁻ , and N ^3-.
The doping amount of the anion is 0.1 mol or less with respect to 1 mol of the composite oxide having the spinel-type crystal structure.
Phosphorylation said shell _{portion, Li 1 + y Fe PO 4} ( wherein, y is a value der Ru satisfying 0.05 ≦ y ≦ 0.3) having a composition represented by, and having an olivine-type crystal structure It is composed of a phosphorylated product, which is doped with at least one anion selected from the group consisting of F ⁻ , Cl ⁻ , and N ^3-.
The doping amount of the anion is 0.1 mol or less with respect to 1 mol of the phosphor oxide having the olivine type crystal structure.
The coverage of the shell is 70 atm% or more as a percentage (atm%) of the atomic ratio represented by P / (Ni + Mn + P) obtained by XPS analysis.
A positive electrode active material for a lithium ion secondary battery.

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