JP6359323B2 - Surface-modified lithium-containing composite oxide for lithium ion secondary battery positive electrode - Google Patents

Description

  The present invention relates to a surface-modified lithium-containing composite oxide for a positive electrode of a lithium ion secondary battery excellent in cycle durability and safety during high-voltage charging.

In recent years, with the rapid development of information-related equipment and communication equipment such as personal computers and mobile phones, there is an increasing demand for non-aqueous electrolyte secondary batteries such as lithium secondary batteries that are small, lightweight, and have high energy density. . As positive electrode active materials for non-aqueous electrolyte secondary batteries, LiCoO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiNi _0.8 Co _0.2 O ₂ , LiMn ₂ O ₄ A composite oxide of lithium and a transition metal or the like such as LiMnO ₂ (hereinafter also referred to as a lithium transition metal-containing composite oxide) is known.

In particular, a lithium secondary battery using lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material and using carbon such as lithium alloy, graphite, or carbon fiber as a negative electrode can obtain a high voltage of 4 V class. In particular, it is widely used as a battery having a high energy density.
However, there is a problem that a raw material compound which is a cobalt source of the lithium cobalt composite oxide is rare and expensive.
Further, in the case of a non-aqueous secondary battery using LiCoO ₂ as a positive electrode active material, the discharge capacity, the stability against heat during heating (hereinafter also simply referred to as safety), and the capacity density per unit volume of the positive electrode layer ( In the following, it is desired to further improve the battery discharge capacity by repeating the charge / discharge cycle, particularly at a high charge voltage, by the reaction between the positive electrode active material interface and the electrolyte. There were problems such as charge / discharge cycle durability, such as reduction in swell and swelling.

On the other hand, lithium nickel composite oxide (LiNiO ₂ ) using relatively inexpensive nickel has a high capacity, but has a problem that its stability to heat is low and its safety when used as a battery is lower than that of LiCoO ₂ .

In addition, lithium manganese composite oxide (LiMn ₂ O ₄ ) having a spinel structure using inexpensive manganese has high heat stability and high safety when used as a battery, but has a problem of low capacity.

Therefore, there are positive electrode active materials such as lithium nickel manganese composite oxide, lithium nickel cobalt composite oxide, and lithium nickel manganese cobalt composite oxide that compensate for the disadvantages when cobalt, nickel, or manganese element is used alone, and have both advantages. It is used.
However, even in the positive electrode active material containing these two or more transition metal elements, the discharge capacity, the charge / discharge cycle durability related to the reduction of the discharge capacity by repeated charge / discharge, the rate characteristics related to the electric capacity that can be discharged in a short time, And what satisfies all the characteristics such as safety during heating after charging has not been obtained. In particular, each characteristic when used at a high charging voltage is insufficient.

In order to solve these problems, for example, it has been proposed to improve charge / discharge cycle durability and safety by replacing part of Co in the lithium cobalt composite oxide with Mg and Ni or Al. (Patent Document 1).
Further, it has been proposed to improve the charge / discharge cycle durability and safety at a high charge voltage by replacing part of Co in the lithium cobalt composite oxide with Mg and Al (Patent Document 2, 3).

  Furthermore, by using a mixture of lithium cobalt-containing composite oxide in which part of Co is substituted with Zr and Mg and lithium nickel manganese composite oxide, charge / discharge cycle durability at high charging voltage, load characteristics, safety, etc. (Patent document 4), by covering the surface of a lithium cobalt-containing composite oxide in which a part of Co is substituted with Mg, Al, Zr, Ti, etc., with a lithium nickel manganese cobalt composite oxide, It has been proposed to improve storage characteristics at a high charging voltage (Patent Document 5).

As described above, various studies have been made so far, but in battery characteristics such as discharge capacity at high charge voltage, discharge average voltage, safety, volume capacity density, charge / discharge cycle durability, storage characteristics, etc. No lithium-containing composite oxide satisfying the above has been obtained.
For example, Patent Document 1 specifically describes LiCo _0.95 Mg _0.05 O ₂ , LiCo _0.90 Mg _0.05 Ni _0.05 O ₂ , LiCo _0.85 Mg _0.05 Ni _0.10 O. ₂ , compositions such as LiCo _0.85 Mg _0.05 Al _0.10 O ₂ are described. It is described that by substituting a part of Co with Mg, the crystal structure is stabilized to improve the charge / discharge cycle durability, and further, substitution with Ni or Al improves safety. Thus, when a part of Co was replaced with Mg alone, or Mg and Ni, or Mg and Al, battery characteristics such as discharge capacity at high charge voltage and charge / discharge cycle durability were insufficient.

Patent Document 2 specifically describes the composition of LiCo _0.94 Mg _0.05 Al _0.01 O _2. By substituting part of Co with Mg, the crystal structure is stabilized, and safety is ensured. Although it is described that the safety improvement is strengthened by substituting with Al, the discharge capacity at a high charge voltage, the charge / discharge cycle durability, etc. are only described by replacing with Mg and Al. The battery characteristics were insufficient.

  In Patent Document 3, by replacing a part of Co with Al, Mg, and further Ti, P, Mn, Zr, and Ge, the lithium cobalt-containing composite oxide has high-temperature charge / discharge cycle durability, It is described that charge / discharge cycle durability at a high charge voltage is improved. However, what is specifically described is battery characteristics when a carbon material is used for the negative electrode and charged at 4.4 V, and characteristics at a higher charging voltage are not described.

  Patent Document 4 proposes a mixed material of a lithium cobalt-containing composite oxide in which a part of Co is substituted with Zr and Mg, and a lithium nickel manganese cobalt composite oxide. By replacing Zr and Mg, the stability of lithium cobalt-containing composite oxide is increased at high voltage, and further, lithium nickel manganese cobalt composite oxide that is excellent in thermal stability at high charging voltage is mixed. It is described that the characteristics are improved. However, what is specifically described is battery characteristics when a carbon material is used for the negative electrode and charged at 4.4 V, and characteristics at a higher charging voltage are not described.

  Patent Document 5 proposes a material in which the surface of a lithium cobalt-containing composite oxide obtained by replacing a part of Co with Mg, Al, Zr, and Ti is covered with a lithium nickel manganese cobalt composite oxide. It is described that the high-temperature storage characteristics during charging are improved by coating a lithium-cobalt-containing composite oxide that is easily deteriorated at a high charge voltage with a lithium nickel manganese cobalt composite oxide that is hardly deteriorated even at a high charge voltage. However, what is specifically described is battery characteristics when a carbon material is used for the negative electrode and charged at 4.4 V, and characteristics at a higher charging voltage are not described.

JP 2003-203634 A JP 2006-324235 A JP 2009-212021 A JP 2006-156230 A JP 2008-198465 A

  Accordingly, an object of the present invention is to provide a positive electrode active material that can be used even under a high charge voltage and has excellent battery performance such as discharge capacity, discharge average voltage, charge / discharge cycle durability, and safety. .

The inventors of the present invention have intensively studied to achieve the above-mentioned problems, and have reached the present invention having the following configuration.
[1] The surface of the lithium-containing composite oxide represented by the general formula (1) is modified with a surface modification compound containing at least one element selected from the group consisting of elements of group S1 and group S2. A surface-modified lithium-containing composite oxide for a positive electrode of a lithium ion secondary battery.
_{Li 1 + x (Co (1} -a-b-m) Ni a Al b M m) 1-x O 2- (f / 2) F f (1)
(However, group S1 is a group consisting of Al, Zr, Ti, Mg, Zn, Nb, Mo, Ta, W and rare earth, and group S2 is a group consisting of F, P, and S. M is At least one selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Na, K, B, C, Si, P, S, Zn, Ga, Bi, Group 2 elements, and rare earth elements Element is -0.05 ≦ x ≦ 0.05, 0 <a ≦ 0.25, 0 <b ≦ 0.05, 0 ≦ m ≦ 0.04, and 0 ≦ f ≦ 0.05.
[2] M is selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Na, K, B, C, Si, P, S, Zn, Y, La, Ce, and Group 2 elements The surface-modified lithium-containing composite oxide according to the above [1], which is at least one kind of element.
[3] The surface-modified lithium-containing composite oxide according to [1], wherein the group S1 is a group consisting of Al, Zr, Ti, Mg, Zn, Nb, W, Y, La, and Gd.
[4] In general formula (1), f = 0, and M is at least one element selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Zn, and Group 2 elements. The surface-modified lithium-containing composite oxide according to [1], wherein the group S1 is a group consisting of Al, Zr, Ti, and Mg, and the surface modification compound includes at least one element selected from the group S1.

[5] The surface-modified lithium-containing composite oxide according to any one of [1] to [4], wherein 0.05 ≦ a + b + m ≦ 0.30.
[6] The surface-modified lithium-containing composite oxide according to any one of [1] to [4], wherein 0.005 ≦ b + m ≦ 0.07.
[7] The surface-modified lithium-containing composite oxide according to any one of [1] to [4], wherein 0 <m ≦ 0.04.
[8] Any of the above [1] to [4], wherein M is at least one element selected from the group consisting of Mg, Ca, Sr, Ti, Zr, Nb, W, Ge, Sn, and Zn. The surface-modified lithium-containing composite oxide described in 1.

[9] The above [1] to [4], in which M is at least one element selected from the group consisting of Mg, Ti, and Zr, and the lithium-containing composite oxide is represented by the general formula (2). The surface-modified lithium-containing composite oxide according to any one of the above.
Li _{1 + x} (Co _(1-ab-m) Ni _a Al _b Mg _c Zr _d Ti _e ) _1-x O ₂ (2)
(However, −0.05 ≦ x ≦ 0.05, 0 <a ≦ 0.25, 0 <b ≦ 0.05, 0 <m ≦ 0.04, 0 ≦ c ≦ 0.02, 0 ≦ d ≦ 0.02, 0 ≦ e ≦ 0.02, m = c + d + e.)
[10] The surface-modified lithium-containing composite oxide according to [9], wherein 0 <c ≦ 0.02 and 0 <d + e ≦ 0.04.
[11] The surface-modified lithium-containing composite oxide according to the above [9], wherein 0 <c ≦ 0.02 and d = e = 0.

[12] The surface-modified lithium-containing composite oxide according to [9], wherein c = 0 and 0 <d + e ≦ 0.04.
[13] Ratio of the total number of moles of group S1 elements contained in the surface modification compound to the number of moles of the lithium-containing composite oxide ((total number of moles of elements of group S1) / lithium-containing composite oxide The surface-modified lithium-containing composite oxide according to any one of the above [1] to [12], in which the number of moles is 0.0001 to 0.03.
[14] The surface modifying compound includes at least one element selected from group S1 and at least one element selected from group S2, and further includes the lithium in the total number of moles of the elements of group S2. Any of the above [1] to [13], wherein the ratio of the containing composite oxide to the number of moles ((total number of moles of group S2) / number of moles of lithium containing composite oxide) is 0.0001 to 0.03. The surface-modified lithium-containing composite oxide described in 1.
[15] The surface modification compound is Zr (CO ₃ ) ₂ , ZrOCO ₃ , ZrO ₂ , Li ₃ PO ₄ , LiF, Li ₂ SO ₄ , Al ₂ O ₃ , AlPO ₄ , TiO ₂ , LiTiO ₂ , and MgO. The surface-modified lithium-containing composite oxide according to any one of the above [1] to [14], which is at least one selected from the group consisting of:

[16] The surface-modified lithium according to any one of [1] to [14], wherein the surface-modifying compound is at least one selected from the group consisting of Zr (CO ₃ ) ₂ , ZrOCO ₃ , and ZrO _2. Containing complex oxide.
[17] The surface-modified lithium-containing composite oxide according to any one of [1] to [14], wherein the surface modification compound is TiO ₂ and / or LiTiO ₂ .
[18] The surface-modified lithium-containing composite oxide according to any one of [1] to [14], wherein the surface-modifying compound is Al ₂ O ₃ and / or AlPO ₄ .
[19] The surface modification compound is at least one selected from the group consisting of ZnO, Nb ₂ O ₅ , WO ₃ , Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , and Gd ₂ Zr ₂ O _7. The surface-modified lithium-containing composite oxide according to any one of the above [1] to [14].
[20] The capacity per 1 g of the surface-modified lithium-containing composite oxide when discharged at a current density of 40 mA per 1 g of the surface-modified lithium-containing composite oxide from 4.6 V to 2.75 V on the basis of Li ⁺ / Li. The surface-modified lithium-containing composite oxide according to any one of [1] to [19], which is 185 mAh / g or more.

[21] The above-mentioned discharge average voltage is 4.0 V or more when discharged at a current density of 40 mA per 1 g of the surface-modified lithium-containing composite oxide material from 4.6 V to 2.75 V on the basis of Li ⁺ / Li The surface modified lithium-containing composite oxide according to any one of [1] to [20].
[22] Based on Li ⁺ / Li standard, per discharge of 50 times at a current density of 100 mA per 1 g of surface-modified lithium-containing composite oxide material from 4.6 V to 2.75 V per 1 g of surface-modified lithium-containing composite oxide material The surface-modified lithium composite oxide according to any one of [1] to [21], wherein the capacity is 75% or more of the first time.
[23] The surface-modified lithium-containing composite oxide according to any one of [1] to [22], wherein the average particle size is 5 to 25 μm and the specific surface area is 0.5 m ² / g or less.
[24] In the above [1] to [23], in the X-ray diffraction using Cu—Kα ray, the half width of the diffraction peak of the (110) plane with 2θ of 65 ± 0.5 ° is 0.15 ° or less. The surface-modified lithium-containing composite oxide according to any one of the above.

[25] The surface-modified lithium-containing composite oxide according to any one of [1] to [24], wherein the amount of free alkali is 0.5 mol% or less.
[26] A positive electrode for a lithium ion secondary battery containing the surface-modified lithium-containing composite oxide according to any one of [1] to [25].
[27] A positive electrode for a lithium secondary battery containing a mixture of two or more kinds of the surface-modified lithium-containing composite oxides according to any one of the above [1] to [25] having different average particle diameters.
[28] Lithium ion containing a mixture of the surface-modified lithium-containing oxide according to any one of [1] to [25] above and a lithium-containing composite oxide (I) different from the surface-modified lithium-containing oxide Secondary battery positive electrode.

[29] The lithium composite oxide (I) is a lithium nickel cobalt manganese-containing composite oxide having a layered structure, a lithium manganese-containing composite oxide having a spinel structure, a lithium iron-containing phosphate compound having an olivine structure, or yLi ₂ QO ₃ · (1-y) LiRO ₂ (where 0 <y <1, Q is one or more metal elements having an average oxidation number of 4+, and R has an average oxidation number of 3+) The positive electrode for a lithium ion secondary battery according to the above [28], which is one or more kinds of metal elements.
[30] The positive electrode for a lithium ion secondary battery according to any one of [26] to [29], wherein the positive electrode density is 3.5 g / cm ³ or more.
[31] A lithium ion secondary battery containing the positive electrode for a lithium ion secondary battery according to any one of [26] to [30], a negative electrode, a separator, and an electrolytic solution.
[32] The lithium ion secondary battery according to [31], wherein the charge potential of the positive electrode is 4.5 V or more on the basis of Li ⁺ / Li.

[33] The negative electrode is selected from the group consisting of carbon materials, lithium titanium-containing composite oxides, lithium, metals that can be alloyed with lithium, alloys of these metals, oxides containing these metals, and nitrides. The lithium ion secondary battery according to the above [31] or [32], which contains at least one kind.
[34] The lithium ion secondary battery according to any one of [31] to [33], wherein the separator is at least one of a nonwoven fabric or a resin porous membrane.
[35] The lithium ion secondary battery according to any one of [31] to [33], wherein the separator is a laminate of porous layers having different melting points.
[36] The lithium ion secondary battery according to any one of the above [31] to [33], wherein the separator contains heat-resistant inorganic fine particles.
[37] The lithium ion secondary according to any one of the above [31] to [36], wherein the electrolytic solution contains at least one selected from the group consisting of ethylene carbonate, ethylmethyl carbonate, and diethyl carbonate. battery.
[38] The electrolyte is at least one selected from the group consisting of VC, cyclohexylbenzene, fluorobenzene, phosphate ester compounds, 4-fluoroethylene carbonate, propane sultone, succinonitrile, and ethylene sulfite as an additive. The lithium ion secondary battery according to any one of the above [31] to [37], which contains a seed.

  According to the present invention, the charging voltage is higher than usual, that is, 4.55 V or more, particularly 4.6 V or more when using lithium for the negative electrode, 4.45 V or more when using a carbon material for the negative electrode, In particular, a surface-modified lithium-containing composite oxide for a lithium secondary battery excellent in battery characteristics such as discharge capacity, discharge average voltage, cycle durability, and safety can be used even at 4.5 V or higher.

The surface-modified lithium-containing composite oxide for the positive electrode of the lithium ion secondary battery of the present invention has the general formula (1), that is, Li _{1 + x} (Co _(1-ab-m) Ni _a Al _b M _m ) _1-x O The particle surface of the lithium-containing composite oxide represented by _{2- (f / 2)} F _f (in the present specification, sometimes simply referred to as a base material) is selected from the group consisting of elements of group S1 and group S2. It is modified with a surface modification compound containing at least one element.
Group S1, Group S2, and M, x, a, b, m, and f in the general formula (1) are as described above.

In the general formula (1), the range of x is −0.05 ≦ x ≦ 0.05, preferably −0.04 ≦ x ≦ 0.04, and more preferably −0.03 ≦ x ≦ 0.03. .
In the general formula (1), the range of a which is the amount of Ni is 0 <a ≦ 0.25.
Since the cycle durability improves as the amount of Ni increases, the lower limit of a is preferably 0.02, more preferably 0.05, and even more preferably 0.07.
On the other hand, when the amount of Ni is large, the discharge voltage and the thermal safety are lowered. Moreover, since the amount of free alkali increases, the stability of the slurry at the time of producing an electrode falls. Therefore, the upper limit of a is preferably 0.20, more preferably 0.17, still more preferably 0.15, and particularly preferably 0.13. Within the above range, the cycle durability is excellent, the discharge voltage and the thermal safety are high, and the slurry during electrode production is stable.

In the general formula (1), the range of b which is the amount of Al is 0 <b ≦ 0.05.
Since the structure is stabilized and the cycle durability is improved as the amount of Al increases, the lower limit of b is preferably 0.002, more preferably 0.005, and even more preferably 0.007. On the other hand, since Al does not contribute to charging / discharging, if the amount of Al is large, the discharge capacity decreases. Therefore, the upper limit of b is preferably 0.03, more preferably 0.02, and even more preferably 0.015. Within the above range, the balance between cycle durability and discharge capacity is good.

  The atomic ratio a / b between Ni and Al is preferably 1 ≦ a / b ≦ 50 in view of the balance between cycle durability and discharge capacity. The lower limit is more preferably 2, more preferably 3, and particularly preferably 5. The upper limit is more preferably 40, still more preferably 30, and particularly preferably 25.

  In the general formula (1), M is a transition metal other than Co and Ni, Sn, Ge, Na, K, B, C, Si, P, S, Zn, Ga, Bi, a Group 2 element, and a rare earth Is at least one element selected from the group consisting of Among them, at least selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Na, K, B, C, Si, P, S, Zn, Y, La, Ce, and Group 2 elements One or more elements are preferable, and at least one element selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, B, P, Zn, Y, La, and Group 2 elements It is more preferable that it is at least one element selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Zn, and Group 2 elements, and Mg, Ca, Sr, Particularly preferred is at least one element selected from the group consisting of Ti, Zr, Nb, W, Ge, Sn and Zn. In particular, from the viewpoint of discharge capacity, safety, charge / discharge cycle durability, etc., it is most preferable that the element is at least one element selected from the group consisting of Mg, Ti, and Zr.

  The amount m of the element M is 0 ≦ m ≦ 0.04. M is an element that is effective in improving safety and cycle durability and reducing the resistance of the positive electrode active material. The more the effect is obtained, the more the effect is obtained, but there is a problem that the discharge capacity is reduced because it does not contribute to charging and discharging. . Therefore, the lower limit is more preferably more than 0, more preferably 0.0001, and particularly preferably 0.0005. Further, the upper limit is more preferably 0.03, and particularly preferably 0.02.

In the general formula (1), the range of f which is the amount of F is 0 ≦ f ≦ 0.05.
When the lithium-containing composite oxide contains fluorine, the heat generation starting temperature is improved, and the safety is further improved. Therefore, when safety is important, f is preferably 0 <f ≦ 0.05, more preferably 0.0005 ≦ f ≦ 0.03, and particularly preferably 0.001 ≦ f ≦ 0.01. On the other hand, when f = 0, that is, when the lithium-containing composite oxide does not contain fluorine, the discharge capacity tends to increase. Therefore, f = 0 is preferable when importance is attached to the capacity.

In the general formula (1), the amount of a + b + m is preferably 0.05 ≦ a + b + m ≦ 0.30. The lower limit is more preferably 0.07, further preferably 0.09, and particularly preferably 0.10. On the other hand, the upper limit is more preferably 0.25, still more preferably 0.23, and particularly preferably 0.20. greater the amount of a + b + m, i.e. although higher structural stability Co amount is small cycle durability increased to improve, whereas the rate characteristics and high discharge voltage is LiCoO ₂ Features decreases. Therefore, if a + b + m is in the above range, the balance is good.

  In the general formula (1), the amount of b + m is preferably 0.005 ≦ b + m ≦ 0.07. The lower limit is more preferably 0.01 and even more preferably 0.02. The upper limit is more preferably 0.05 and even more preferably 0.03. The larger the amount of b + m, the more effective the cycle durability and the resistance reduction of the positive electrode active material, but the discharge capacity decreases. Therefore, if b + m is in the above range, the balance is good.

  In the general formula (2), the amount c of Mg is preferably 0 ≦ c ≦ 0.02, and more preferably 0 ≦ c ≦ 0.01. The amount d of Zr is preferably 0 ≦ d ≦ 0.02, and more preferably 0 ≦ d ≦ 0.01. The amount e of Ti is preferably 0 ≦ e ≦ 0.02, and more preferably 0 ≦ e ≦ 0.01.

  According to the present invention, the lithium secondary battery can be used under a higher charging voltage than usual, that is, particularly 4.5 V or more, and has excellent battery characteristics such as discharge capacity, discharge average voltage, cycle durability, and safety. A surface-modified lithium-containing composite oxide for a secondary battery is provided. The reason why the surface-modified lithium-containing composite oxide for a lithium ion secondary battery of the present invention exhibits excellent characteristics as a positive electrode active material for a lithium secondary battery as described above is not necessarily clear. It is estimated as follows.

The structure of the lithium-containing composite oxide becomes more unstable under a higher voltage than usual because the amount of Li extracted increases. Therefore, it is necessary to stabilize the structure more than ever.
Ni has an ionic radius close to that of Co and has good compatibility, so that Ni can be uniformly dissolved in the LiCoO ₂ crystal. Therefore, it is considered that substitution of Ni stabilizes the structure and improves cycle durability. Furthermore, since Ni itself is oxidized and reduced and contributes to charge and discharge, the amount of substitution can be increased without reducing the discharge capacity.

Similarly, since Al also has an ionic radius close to that of Co and Ni, it is considered that Al dissolves uniformly in the LiCoO ₂ crystal. Since Al itself does not oxidize and reduce, it does not contribute to charging / discharging, but it is considered that the structure can be further stabilized.
In addition, since Al and Ni have good compatibility, it is considered that Al can be dissolved more uniformly in the crystal by the presence of Ni.
Furthermore, by modifying the surface of LiCoO ₂ with Ni and Al substituted with different compounds, the contact area with the electrolyte is reduced, and surface modification of the positive electrode active material due to decomposition of the electrolyte and elution of metal ions are suppressed. In addition, cycle durability can be improved and gas generation can be suppressed.

  By surface-modifying the lithium-containing composite oxide, the area where the base material and the electrolytic solution are in direct contact can be reduced, and the reaction between the base material and the electrolytic solution can be suppressed. As a result, it is possible to suppress deterioration of the surface of the base material, elution of metal ions from the surface of the base material, and oxidative decomposition of the electrolytic solution, improving cycle durability and safety, and suppressing battery expansion. Can do. Therefore, the surface modification compound is preferably a chemically stable compound.

The surface modifying compound of the lithium-containing composite oxide is a compound different from the base material, and includes group S1 (Al, Zr, Ti, Mg, Zn, Nb, Mo, Ta, W, and rare earth), and group S2 ( At least one element selected from the group consisting of F, P, and S).
When emphasizing cycle durability, the surface modification compound preferably contains at least one element selected from group S1. The element of group S1 is preferably Al, Zr, Ti, Mg, Zn, Nb, W, Y, La, and Gd, and at least one element selected from the group consisting of Al, Zr, Ti, and Mg More preferably, it is more preferably at least one element selected from the group consisting of Al and Zr, and particularly preferably Zr.

The state of the surface modification compound containing the element of group S1 is not particularly limited, but is preferably an oxide, a carbon-containing oxide, a hydroxide, a carbonate, or a lithium salt. The lithium salt is generated by a reaction with excess lithium in the base material. Among these, an oxide, a carbon-containing oxide, or a lithium salt is preferable, and an oxide or a carbon-containing oxide is more preferable. The surface modifying compound may be one kind or a mixed state of two or more kinds.
When emphasizing safety and swelling suppression, the surface modification compound preferably contains at least one element selected from the group consisting of Group S2. Among them, it is more preferable that F and / or P is contained, and it is more preferable that P is contained.
The state of the surface modification compound containing F, P, and S is not particularly limited, but is preferably an oxide, a lithium salt, or a compound with a group S1 element, and is preferably a lithium salt or a compound with a group S1 element. More preferred.

  When the compound containing F, P, and S reacts with surplus lithium contained in the base material to produce a Li salt, the amount of alkali is reduced by surface modification, which is more preferable. .

  It is more preferable that the surface modification compound contains one or more elements from the group S1 element and one or more elements from the group S2 element because it is effective in improving cycle durability and safety and suppressing swelling.

  As described above, the surface modifying compound improves various characteristics. On the other hand, if the adhesion amount is too large, it is difficult for Li ions to move between the base material and the electrolytic solution. Therefore, the total number of moles of the elements of group S1 in the surface modification compound is preferably 0.0001 or more, and more preferably 0.0005 or more in terms of mole ratio with respect to the number of moles of the base material. 0.001 or more is more preferable. Further, it is preferably 0.03 or less, more preferably 0.01 or less, and further preferably 0.005 or less.

  The total number of moles of elements of group S2 is preferably 0.0001 or more, more preferably 0.0005 or more, and more preferably 0.001 or more in terms of mole ratio with respect to the number of moles of the base material. And more preferred. Further, it is preferably 0.03 or less, more preferably 0.02 or less, and further preferably 0.01 or less.

The form of the surface modifying compound varies depending on the surface treatment and the heat treatment conditions after the surface treatment. Therefore, the surface modification compound may not be a stable compound that is in a stoichiometric ratio. Moreover, it is not limited to one type of compound, The mixed state of various compounds may be sufficient.
Examples of the surface modifying compound include Al (OH) ₃ , Al ₂ O ₃ , LiAlO ₂ , AlPO ₄ , AlF ₃ , Al ₂ (SO ₄ ) ₃ , Zr (OH) ₄ , ZrO ₂ , Zr (CO _3). ) ₂ , ZrOCO ₃ , Li ₂ ZrO ₃ , Zr ₃ (PO ₄ ) ₄ , ZrF ₄ , Li ₂ ZrF ₆ , Zr (SO ₄ ) ₂ , Ti (OH) ₄ , TiO ₂ , LiTiO ₂ , Li ₂ TiF ₆ , Mg (OH) ₂ , MgO, Li ₃ PO ₄ , LiF, Li ₂ SO ₄ , ZnO, Nb ₂ O ₅ , WO ₃ , Y ₂ O ₃ , La ₂ O ₃ , Li _0.35 La _0.55 TiO ₃ , Gd ₂ O ₃ , Gd ₂ Zr ₂ O ₇ , or a mixture of each.

As the surface modifying compound, a group consisting of Zr (CO ₃ ) ₂ , ZrOCO ₃ , ZrO ₂ , Li ₃ PO ₄ , LiF, Li ₂ SO ₄ , Al ₂ O ₃ , AlPO ₄ , TiO ₂ , LiTiO ₂ , and MgO. It is preferably at least one selected from the group consisting of
Among these, the surface modification compound is more preferably at least one selected from the group consisting of Zr (CO ₃ ) ₂ , ZrOCO ₃ , and ZrO ₂ .
Further, the surface modifying compound is particularly preferably Zr (CO ₃ ) ₂ and / or ZrOCO ₃ .

As the surface modifying compound, more preferably TiO ₂ and / or LiTiO _2. Further, the surface modifying compound is more preferably Al ₂ O ₃ and / or AlPO ₄ .
The surface modifying compound is more preferably MgO.
The surface modifying compound is more preferably at least one selected from the group consisting of Li ₃ PO ₄ , LiF, and Li ₂ SO ₄ .
The surface modifying compound is at least one selected from the group consisting of ZnO, Nb ₂ O ₅ , WO ₃ , Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , and Gd ₂ Zr ₂ O ₇ . Is more preferable.

  The average particle diameter D50 (also simply referred to as average particle diameter or D50) of the surface-modified lithium-containing composite oxide is preferably 5 μm or more and 25 μm or less. More preferably, it is 10 μm or more and 20 μm or less. The larger the particle size, the higher the packing density and the higher the battery capacity per volume. However, when the particle size is increased, the movement distance of Li ions in the particle is increased, so that the capacity and rate characteristics tend to be reduced. For this reason, the average particle size is in the above range and the balance is good.

  In the present invention, the average particle size D50 means a value that is 50% of the cumulative volume particle size distribution obtained by a laser scattering particle size distribution measuring apparatus (for example, using Microtrack HRAX-100 manufactured by Nikkiso Co., Ltd.). .

The specific surface area of the surface-modified lithium-containing composite oxide is preferably 0.5 m ² / g or less, more preferably 0.4 m ² / g or less, and further preferably 0.3 m ² / g or less. The lower limit is not particularly defined, preferable to be 0.05 m ² / g, more preferably a 0.1 m ² / g. The lower the specific surface area, the smaller the contact area with the electrolyte solution, so the cycle durability tends to improve. is there. Therefore, the specific surface area is in the above range and the balance is good.

In the present invention, the specific surface area is obtained by a specific surface area measuring apparatus (for example, using a Macsorb manufactured by Mountec Co., Ltd.) by nitrogen gas adsorption.
With respect to the surface-modified lithium-containing composite oxide, the X-ray diffraction using Cu-Kα rays has a half-value width of the diffraction peak of the (110) plane with 2θ of 65 ± 0.5 ° being 0.15 ° or less. preferable. The lower limit is preferably 0.05. The half width of the (110) plane represents the degree of crystal growth, and the smaller the value, the more advanced the crystal growth. Since the degree of crystal growth affects the average particle diameter and specific surface area, it is well balanced if it is in the above range.

In the present invention, the half width of the (110) plane is determined from the obtained X-ray diffraction spectrum by the powder X-ray diffraction method using analysis software PDXL and database ICDD PDF-2 (manufactured by Rigaku Corporation). Can do.
Further, the surface-modified lithium-containing composite oxide is a secondary particle type in which a large number of small primary particles are aggregated, a primary particle type in which several to about 10 slightly larger primary particles are collected, and a single particle in which primary particles are grown. Any of the particle types may be used, but the primary particle type or the single particle type is preferable from the viewpoint of contact with the above-described electrolytic solution.

  The amount of free alkali of the surface-modified lithium-containing composite oxide is preferably 0.5 mol% or less, more preferably 0.4 mol.% Or less, and further preferably 0.3 mol% or less. If the amount of free alkali is large, the stability of the slurry at the time of electrode preparation may be reduced, and the amount of gas generated when the battery is stored at high temperature may increase. Therefore, the lower the amount of free alkali, the better.

  In the present invention, the amount of free alkali is determined by dispersing 5 g of surface-modified lithium-containing composite oxide in 50 g of water, stirring for 30 minutes, filtering, and neutralizing titrating the filtrate with an aqueous hydrochloric acid solution. Depending on the surface modifying compound, it may be dissolved in the filtrate and neutralized at the same time as the alkali component of the base material. In that case, the filtrate after neutralization titration is analyzed by ICP, ion chromatograph or the like, and the component derived from the surface modification compound is quantified and subtracted to obtain the original alkali component of the surface modified lithium-containing composite oxide. . The amount of free alkali is calculated as the amount per 1 mol of the base material.

The surface-modified lithium-containing composite oxide of the present invention can be used even when the potential of the positive electrode is 4.6 V on the basis of Li ⁺ / Li, and this surface-modified lithium-containing composite oxide is used as the positive electrode active material. A high-capacity lithium ion secondary battery can be provided.
The battery using the surface-modified lithium-containing composite oxide of the present invention discharged at a current density of 40 mA per 1 g of the surface-modified lithium-containing composite oxide, with the positive electrode potential being 4.6 V to 2.75 V on the basis of Li ⁺ / Li. The initial discharge capacity is preferably 185 mAh / g or more, and more preferably 190 mAh / g or more. Further, the average discharge voltage at the first discharge is preferably 4.00 V or more, more preferably 4.02 V or more, and further preferably 4.05 V or more on the basis of Li ⁺ / Li.

  After the first charge / discharge, the capacity retention rate at the 50th time is preferably 75% or more when discharged at a current density of 100 mA per 1 g of the surface-modified lithium-containing composite oxide, and is preferably 80% or more. More preferred. Here, the 50th capacity retention rate is the 50th discharge capacity retention rate with respect to the first discharge capacity when discharged at a rate of 100 mA per 1 g of the surface-modified lithium-containing composite oxide.

Although the manufacturing method of the surface modification lithium containing complex oxide of this invention is not specifically limited, Specifically, it can manufacture by the following method.
A compound containing Co, Ni, Al, and M (sometimes referred to simply as a raw material in this specification), a compound containing Li (sometimes referred to simply as a Li raw material in this specification), and as necessary A compound containing F is mixed, fired, crushed, and classified to obtain a lithium-containing composite oxide as a base material.
The surface-modified lithium-containing composite oxide can be obtained by mixing the lithium-containing composite oxide with an element for surface modification in a solid or liquid state and heat-treating it.

Although it does not specifically limit as a cobalt compound, It is preferable to use cobalt hydroxide, cobalt oxyhydroxide, cobalt oxide, cobalt carbonate, cobalt sulfate, or cobalt nitrate. Among these, cobalt hydroxide, cobalt oxyhydroxide or cobalt oxide is more preferable, and cobalt oxyhydroxide or cobalt oxide is more preferable.
Each of Ni, Al, and M elements may be a single compound or a coprecipitated composite compound that is coprecipitated with cobalt.

Ni compounds, Al compounds, and M element compounds are not particularly limited, but include inorganic salts such as oxides, hydroxides, nitrates, sulfates, carbonates, acetates, oxalates, citrates, and maleic acids. Organic acid salts such as lactate, tartrate, malate and malonate are preferred. When these compounds are used, they may be mixed in solid phase together with Co raw material and Li raw material, or after impregnating Co raw material with a solution prepared by dissolving these compounds in water or an organic solvent and drying, You may mix with Li raw material.
In the case of a coprecipitation complex compound, a coprecipitation hydroxide, a coprecipitation oxyhydroxide, a coprecipitation oxide, or a coprecipitation carbonate is preferable, and among these, a coprecipitation oxyhydroxide or a coprecipitation oxide is more preferable.

Although it does not specifically limit as a lithium compound, It is preferable to use lithium carbonate or lithium hydroxide, and lithium carbonate is more preferable especially.
Although it does not specifically limit as a fluorine compound, It is preferable to use the fluoride of lithium fluoride, Al, or M element, and lithium fluoride is more preferable.
The above-mentioned Co raw material, Ni raw material, Al raw material, M element raw material, Li raw material, and F raw material are mixed so that each element has a desired atomic ratio, and then fired, crushed, and classified so that a lithium-containing composite Obtain an oxide. The firing temperature is preferably 800 to 1100 ° C, more preferably 900 to 1080 ° C, and further preferably 950 to 1050 ° C. In the case of calcining before firing, the calcining temperature is preferably 300 to 600 ° C, more preferably 350 to 600 ° C, and even more preferably 400 to 550 ° C. Further, the calcination and firing atmosphere is preferably performed in an oxygen-containing atmosphere, and more preferably in the air.

  As a surface modification method, the obtained lithium-containing composite oxide is mixed with a compound powder containing an element for surface modification in a solid phase and heat treated, or a solution in which a compound containing an element for surface modification is dissolved (hereinafter referred to as a surface modification). In this case, the surface modification solution is impregnated and then heat-treated. However, since the surface can be uniformly modified, the method of impregnating the surface modification solution is preferable.

  The method for impregnating the lithium-containing composite oxide with the surface modification solution is not limited, but means for spraying the surface modification solution onto the powder of the lithium-containing composite oxide to impregnate the surface modification solution in the container. A means of mixing with lithium-containing composite oxide, stirring, and impregnating can be used. Specific examples of the means for spraying include a spray dryer, a flash dryer, a belt dryer, a Laedige mixer, a thermoprocessor, and a paddle dryer. As a means for mixing and stirring in a container, a twin screw kneader, an axial mixer, a paddle mixer, a turbulizer, a Ladige mixer, a drum mixer and the like can be used. In particular, as a method of impregnating the lithium-containing composite oxide with the surface modification solution, it is preferable to spray and impregnate the surface modification solution while stirring the lithium-containing composite oxide powder. In addition to the commercially available stirrer, a small stirrer of about lab size can also be used. Further, the surface modification solution may be sprayed and mixed without using a stirrer.

  When the surface modification solution is impregnated into the lithium-containing composite oxide, the solid / liquid ratio (weight basis) is preferably 70/30 to 99.5 / 0.5, and more preferably 85/15 to 99/1. 90/10 to 98/2 is particularly preferable. The concentration of the compound containing the element for surface modification in the surface modification solution is preferably as high as possible because a small amount of solvent is desired in the subsequent heat treatment. However, if the concentration is too high, the viscosity increases and it becomes difficult to uniformly modify the surface of the lithium-containing composite oxide, so 0.01 to 50% by weight is preferable, and 0.1 to 30% by weight is more preferable.

As the solvent, water or an organic solvent can be used, but water is preferable from the viewpoint of cost, harmfulness, and workability. The heat treatment temperature is preferably 200 ° C to 900 ° C, more preferably 300 ° C to 800 ° C, and further preferably 350 ° C to 700 ° C. When the heat treatment temperature is low, decomposition of the raw material used for the surface modification is insufficient, and the target compound may not be obtained, or components other than the target compound, particularly organic substances may remain as impurities. On the other hand, if the heat treatment temperature is too high, the surface modifying element diffuses into the lithium composite oxide and a sufficient surface modifying effect cannot be obtained. Therefore, the heat treatment temperature is preferably within the above-mentioned temperature range, and Zr (CO ₃ ) ₂ , ZrOCO ₃ , ZrO ₂ , Li ₃ PO ₄ , LiF, Li ₂ SO ₄ , Al ₂ O ₃ , AlPO depending on the raw materials used. ₄ , TiO ₂ , LiTiO ₂ , MgO, ZnO, Nb ₂ O ₅ , WO ₃ , Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , Gd ₂ Zr ₂ O _7, etc. An oxide can be obtained. For example, when ammonium zirconium carbonate is used as a Zr surface modification raw material, Zr (CO ₃ ) ₂ which is a decomposition product is generated when the heat treatment temperature is low, ZrOCO ₃ is generated when the heat treatment temperature is higher, and ZrO ₂ is generated when the heat treatment temperature is higher. . Further, F, P, and S easily react with surplus lithium in the lithium composite oxide to generate a Li compound.

  Although it does not specifically limit as a raw material compound of the element of group S1 used for surface modification, Inorganic salts, such as an oxide, hydroxide, nitrate, sulfate, carbonate, acetate, oxalate, citrate, Preferred are organic acid salts such as maleic acid, lactate, tartrate, malate and malonate, ammonium complex solution, organometallic chelate complex solution, compound solution in which metal alkoxide is stabilized with chelate and the like. Among them, Al is preferably an aluminum lactate aqueous solution, Zr is an ammonium zirconium carbonate aqueous solution, and Ti is preferably a titanium lactate aqueous solution. Further, when the surface of the fluoride is modified, it is preferable to use a metal fluoride salt.

  Although it does not specifically limit as a compound of P used for surface modification, Phosphoric acid, pyrophosphoric acid, phosphorous acid, hypophosphorous acid, hexametaphosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, polyphosphoric acid, lithium phosphate, phosphoric acid Ammonium, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate ester and the like can be used. Among them, phosphoric acid, pyrophosphoric acid, phosphorous acid, hypophosphorous acid, tripolyphosphoric acid, tetrapolyphosphoric acid, polyphosphoric acid, lithium phosphate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, guanidine phosphate And one selected from the group consisting of choline phosphate. Among them, there is a tendency to further improve the battery performance, and there is an effect of suppressing the reaction with the electrolytic solution, phosphoric acid, pyrophosphoric acid, hypophosphorous acid, polyphosphoric acid, lithium phosphate, ammonium phosphate, hydrogen phosphate One type selected from the group consisting of diammonium, ammonium dihydrogen phosphate and guanidine phosphate is more preferred. Furthermore, at least one selected from the group consisting of phosphoric acid, pyrophosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate, which are remarkably effective and inexpensive and easily available, is particularly preferable.

Although it does not specifically limit as a compound of F used for surface modification, A metal fluoride, ammonium fluoride, ammonium hydrogen fluoride, etc. can be used. In the case of a metal fluoride, Zr is preferably ammonium hexafluorozirconate, Al is sodium hexafluoroaluminate, and Ti is preferably ammonium hexafluorotitanate.
Although it does not specifically limit as a compound of S used for surface modification, A metal sulfate, ammonium sulfate, ammonium hydrogen sulfate, etc. can be used. Of these, metal sulfate or ammonium sulfate is preferred.

  When two or more elements are surface-modified from group S1 and group S2, the ratio of each element to be surface-modified can be set to an arbitrary ratio by adjusting the amount of the raw material. Moreover, when surface-modifying by the method of impregnating a solution, it is good also as one solution which melt | dissolved two or more types of compounds, and you may divide a solution into several and may repeat an impregnation process. From the viewpoint of productivity, it is preferable to use one solution.

When producing a positive electrode for a lithium ion secondary battery from the surface-modified lithium-containing composite oxide obtained in the present invention, first, acetylene black, graphite, ketjen black, etc. are used as the surface-modified lithium-containing composite oxide powder. The carbon-based conductive material and the binder are mixed. For the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin, or the like is preferably used. The surface-modified lithium-containing composite oxide powder, conductive material and binder obtained by the present invention are made into a slurry or a kneaded product using a solvent or a dispersion medium. After applying this to a positive electrode current collector such as an aluminum foil or a stainless steel foil, the solvent is removed by heating to produce a positive electrode for a lithium ion secondary battery.
The surface-modified lithium-containing composite oxide used when producing a positive electrode for a lithium ion secondary battery in the present invention is preferably a mixture of two or more active materials having different average particle diameters. By mixing two or more kinds of active materials having different average particle diameters, the packing density of the positive electrode is increased, the capacity per unit volume of the battery can be increased, and a high capacity battery can be provided.
As described above, when two or more kinds of active materials are mixed, only the surface-modified lithium-containing composite oxide of the present invention may be mixed and used, or other lithium-containing composite oxide (I) may be used. It can also be used by mixing. By mixing other lithium-containing composite oxide (I), it is possible to provide a battery in which the respective characteristics are complemented and the characteristics are balanced.

The other lithium-containing composite oxide (I) includes a lithium nickel cobalt manganese-containing composite oxide having a layered structure, a lithium manganese-containing composite oxide having a spinel structure, a lithium iron-containing phosphate compound having an olivine structure, or yLi _2. QO ₃ · (1-y) LiRO ₂ (where 0 <y <1, Q is one or more metal elements having an average oxidation number of 4+, and R is 1+ having an average oxidation number of 3+) It is preferably a metal element of more than kinds. By mixing other lithium-containing composite oxide (I), particularly safety and cycle durability can be improved.
The density of the positive electrode is preferably 3.5 g / cm ³ or more, and more preferably 3.6 g / cm ³ or more.

In the battery using the positive electrode obtained by the present invention, the charging potential of the positive electrode is preferably 4.5 V or more, more preferably 4.55 V or more, particularly preferably 4.6 V or more on the basis of Li ⁺ / Li. By charging at a high voltage, the capacity per 1 g of the surface-modified lithium-containing oxide and the discharge average voltage can be increased, and a high-capacity lithium ion secondary battery can be provided.

The lithium ion secondary battery of this invention contains the said positive electrode, a negative electrode, a separator, and electrolyte solution.
In the lithium ion secondary battery of the present invention, the material and shape of the separator are not particularly limited, and those having insulating properties, high ion permeability, low electrical resistance, and high liquid retention are preferable.
In the present invention, a non-woven fabric made of a material that is stable and electrochemically stable with respect to the electrolyte solution and electrolyte of the battery, a porous resin membrane, or both of them can be used. . Among these, from the viewpoint of safety, it is preferable to use a nonwoven fabric or a porous film having a melting point of 80 ° C to 150 ° C. Furthermore, porous films having different melting points can be used by being laminated.
In the battery of the present invention, a separator containing heat-resistant inorganic fine particles can also be used. By containing the heat-resistant inorganic fine particles, the safety when heat is generated in the battery becomes higher.

The heat-resistant inorganic fine particles are not particularly limited, but have electrical insulation properties, are electrochemically stable, are stable to an electrolyte and an electrolyte, and are electrolyzed even at a high temperature of 150 ° C. or higher. Those that do not dissolve in the liquid are preferred. Specific examples of such heat-resistant fine particles include oxides and nitrides containing Si, Al, Ti, Zr, Sn, or Ba, and these may be used alone or in combination of two or more. You may use by mixing.
In the lithium ion secondary battery of the present invention, a nonaqueous electrolytic solution or a solid electrolyte in which a lithium salt is dissolved in an organic solvent is used.

  Various solvents can be used as the solvent for the nonaqueous electrolytic solution, and among these, a carbonate ester is preferable. The carbonate ester can be either cyclic or chain. Examples of the cyclic carbonate include propylene carbonate and ethylene carbonate. Examples of chain carbonates include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, and the like. Especially, it is preferable to contain at least 1 sort (s) chosen from the group which consists of ethylene carbonate, ethylmethyl carbonate, and diethyl carbonate from viewpoints, such as the discharge characteristic of a battery, cycling durability, and charging / discharging efficiency.

Further, the lithium salt used for the electrolyte is not particularly limited. For example, ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ CO ₂ ⁻ , ( Any one or more of lithium salts having CF ₃ SO ₂ ) ₂ N ^— or the like as an anion is preferably used. The concentration of the lithium salt contained in the electrolytic solution is preferably 0.2 to 2.0 mol / l (liter), particularly preferably 0.5 to 1.5 mol / l. In the case of this concentration range, the ionic conductivity is large and the electric conductivity of the electrolytic solution is increased.

  An additive different from the solvent and the electrolyte may be added to the electrolytic solution. The additive is at least one selected from the group consisting of vinylene carbonate (VC), cyclohexylbenzene, fluorobenzene, phosphoric ester compounds, 4-fluoroethylene carbonate, propane sultone, succinonitrile, and ethylene sulfite. It is preferable. The additive mainly serves as a positive / negative electrode protective film and suppresses reaction with the electrolyte solution component, thereby suppressing the generation of gas due to improvement in cycle durability and voltage resistance, decomposition of the electrolyte solution component, and the like.

In the lithium ion secondary battery of the present invention, a material capable of occluding and releasing lithium ions is used for the negative electrode active material. The negative electrode active material is not particularly limited. However, for example, a carbon material, a lithium titanium-containing composite oxide, a lithium metal, a metal that can be alloyed with lithium, Examples include alloys, oxides, and nitrides. These may be used alone or in combination of two or more.
As the carbon material, those obtained by pyrolyzing organic substances under various pyrolysis conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, flake graphite, and the like can be used. As the lithium titanium-containing oxide, those having a spinel structure are particularly preferable. Examples of metals that can be alloyed with lithium include Si, Pb, Sn, Al, Ag, and Ge. .
As the negative electrode current collector, a copper foil, a nickel foil, or the like is used. Such a negative electrode is preferably produced by kneading the active material with an organic solvent to form a slurry, and applying the slurry to a metal foil current collector, drying, and pressing.

  The shape of the lithium battery using the positive electrode active material for the surface-modified lithium-containing composite oxide obtained in the present invention is not particularly limited. A sheet shape, a film shape, a folded shape, a wound-type bottomed cylindrical shape, a button shape, or the like is selected depending on the application.

  Hereinafter, examples of the present invention will be described in comparison with comparative examples. However, these examples are examples of embodiments of the present invention, and the present invention is not construed as being limited to these examples.

[Example 1]
Lithium carbonate powder, cobalt oxyhydroxide powder, basic nickel carbonate powder, aluminum hydroxide powder, magnesium hydroxide powder, and zirconium oxide powder were mixed in a molar ratio of Li: Co: Ni: Al: Mg: Zr of 0.98. : 0.949: 0.03: 0.01: 0.01: 0.001, and the mixed powder was fired at 1010 ° C. for 14 hours in an air atmosphere to obtain a lithium-containing composite oxide. The composition of the obtained lithium-containing composite oxide was Li _0.99 (Co _0.949 Ni _0.03 Al _0.01 Mg _0.01 Zr _0.001 ) _1.01 O ₂ . Hereinafter, in this specification, the lithium-containing composite oxide before surface modification may be referred to as a base material.
To 100 g of the obtained lithium-containing composite oxide, 4 g of a surface modification solution having a Zr content of 2.4% by weight obtained by diluting ammonium zirconium carbonate (NH ₄ ) ₂ [Zr (CO ₃ ) ₂ (OH) ₂ ] with water was used. The surface modification precursor raw material was obtained by spraying and mixing. The Zr surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 400 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Zr was detected on the particle surface. In addition, when the generated gas during heating was measured by TPD-MS and compared with the base material, generation of CO ₂ was confirmed, and NH ₃ and NO _x were not generated. From this, the surface modification compound is presumed to be any of Zr (CO ₃ ) ₂ , ZrOCO ₃ , or a mixture of Zr (CO ₃ ) ₂ and ZrOCO ₃ .
The average particle diameter D50 of the obtained surface-modified lithium-containing composite oxide was 13.9 μm, the specific surface area was 0.23 m ² / g, the (110) half-value width was 0.09 °, and the free alkali amount was 0.23 mol%. there were.

The surface-modified lithium-containing composite oxide powder, which is a positive electrode active material, and acetylene black and polyvinylidene fluoride powder are mixed at a mass ratio of 80/12/8, and N-methylpyrrolidone is added to prepare a slurry. This was coated on one side using a doctor blade on an aluminum foil having a thickness of 20 μm. The obtained aluminum sheet was dried and roll press rolled to produce a positive electrode sheet for a lithium battery.
Next, the positive electrode sheet is used as a positive electrode, a metal lithium foil having a thickness of 500 μm is used as a negative electrode, a SUS plate is used as a negative electrode current collector, and a porous polypropylene having a thickness of 25 μm is used as a separator. Furthermore, as the electrolytic solution, stainless steel is used by using a LiPF ₆ / EC + DEC (1: 1) solution having a concentration of 1 M (meaning a mixed solution of EC and DEC having a volume ratio (1: 1) of LiPF ₆ as a solute). A simple sealed cell type lithium battery made in an argon glove box was assembled.

The above-described simple sealed cell type lithium battery is charged at a current value of 100 mA per 1 g of the positive electrode active material at 25 ° C. with an upper limit voltage of 4.6 V, and charged in a CCCV mode for 6 hours (at a constant current of 100 mA. Then, the battery was charged at a constant voltage of the upper limit voltage.The total charging time was 6 hours.) And then discharged to 2.75 V at a current value of 40 mA per 1 g of the positive electrode active material. The charge / discharge capacity was determined. As a result, the initial discharge capacity of the positive electrode active material at 25 ° C. and 2.75 to 4.6 V is 203 mAh / g, the ratio of the initial charge capacity to the discharge capacity, the initial charge / discharge efficiency is 91.2%, The discharge average voltage was 4.04 V, and the initial discharge energy was 820 mWh / g.
This battery was subjected to 50 charge / discharge cycles under the same conditions as the first time except that charging was performed at a current value of 200 mA / g of the positive electrode active material for 3 hours in the CCCV mode and discharging was performed at a current value of 100 mA / g of the positive electrode active material. The capacity retention rate after 50 charge / discharge cycles was 78.8%.

[Example 2]
Example 1 except that the molar ratio of Li: Co: Ni: Al: Mg: Zr in the mixed powder was 0.98: 0.899: 0.08: 0.01: 0.01: 0.001 In the same manner, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.99 (Co _0.899 Ni _0.08 Al _0.01 Mg _0.01 Zr _0.001 ) _1.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 3]
Example 1 except that the molar ratio of Li: Co: Ni: Al: Mg: Zr in the mixed powder was 1.02: 0.899: 0.08: 0.01: 0.01: 0.001 In the same manner, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.01 (Co _0.899 Ni _0.08 Al _0.01 Mg _0.01 Zr _0.001 ) _0.99 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 4]
Example 1 except that the molar ratio of Li: Co: Ni: Al: Mg: Zr in the mixed powder was 0.98: 0.849: 0.13: 0.01: 0.01: 0.001 In the same manner, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.99 (Co _0.849 Ni _0.13 Al _0.01 Mg _0.01 Zr _0.001 ) _1.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 5]
Example 1 except that the molar ratio of Li: Co: Ni: Al: Mg: Zr in the mixed powder was 0.98: 0.799: 0.18: 0.01: 0.01: 0.001 In the same manner, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.99 (Co _0.799 Ni _0.18 Al _0.01 Mg _0.01 Zr _0.001 ) _1.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 6]
Example 1 except that the molar ratio of Li: Co: Ni: Al: Mg: Zr in the mixed powder was 0.98: 0.749: 0.23: 0.01: 0.01: 0.001 In the same manner, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.99 (Co _0.749 Ni _0.23 Al _0.01 Mg _0.01 Zr _0.001 ) _1.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 7]
Example 1 except that the molar ratio of Li: Co: Ni: Al: Mg: Zr in the mixed powder was 1.03: 0.90: 0.07: 0.01: 0.01: 0.01 In the same manner as above, the lithium-containing composite oxide mixed powder was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.015 (Co _0.90 Ni _0.07 Al _0.01 Mg _0.01 Zr _0.01 ) _0.985 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 8]
Implementation was carried out except that the zirconium oxide powder was not mixed and the molar ratio of Li: Co: Ni: Al: Mg in the mixed powder was 0.97: 0.90: 0.08: 0.01: 0.01. In the same manner as in Example 1, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.985 (Co _0.90 Ni _0.08 Al _0.01 Mg _0.01 ) _1.015 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 9]
In the same manner as in Example 8, except that the molar ratio of Li: Co: Ni: Al: Mg in the mixed powder was 0.97: 0.88: 0.08: 0.03: 0.01, lithium was used. Containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.985 (Co _0.88 Ni _0.08 Al _0.03 Mg _0.01 ) _1.015 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 10]
Except for not mixing magnesium hydroxide powder and setting the molar ratio of Li: Co: Ni: Al: Zr in the mixed powder to 1.03: 0.90: 0.08: 0.01: 0.01, In the same manner as in Example 1, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.015 (Co _0.90 Ni _0.08 Al _0.01 Zr _0.01 ) _0.985 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 11]
A titanium oxide powder was used instead of the zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: Ti in the mixed powder was 1.03: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.015 (Co _0.90 Ni _0.08 Al _0.01 Ti _0.01 ) _0.985 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 12]
100 g of the lithium-containing composite oxide obtained in Example 2 and 4 g of a surface modification solution having a Zr content of 2.4% by weight obtained by diluting ammonium zirconium carbonate with water, and a P content obtained by dissolving ammonium dihydrogen phosphate in water. A surface modification precursor raw material was obtained by spraying and mixing 4 g of a 3.2 wt% surface modification solution. The Zr surface modification amount was 0.1 mol% with respect to the base material, and the P surface modification amount was 0.4 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 600 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Zr and P were detected on the particle surface. Further, when the powder X-ray diffraction spectrum of the surface-modified lithium-containing composite oxide in which the surface modification amounts of Zr and P were increased 10 times as a model, peaks of ZrO ₂ and Li ₃ PO ₄ were detected. From this, it is presumed that the surface modification compound of this example is a mixture of ZrO ₂ and Li ₃ PO ₄ .
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 13]
To 100 g of the lithium-containing composite oxide obtained in Example 2, 4 g of a surface modification solution having a Zr content of 2.4 wt% and an F content of 3.0 wt% diluted with ammonium hexafluorozirconate with water was sprayed. The surface modification precursor raw material was obtained by mixing. The Zr surface modification amount was 0.1 mol% with respect to the base material, and the F surface modification amount was 0.6 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 600 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.

As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Zr and F were detected on the particle surface. Moreover, as a result of measuring a powder X-ray diffraction spectrum in a model manner as in Example 12, peaks of ZrO ₂ and LiF were detected. From this, it is presumed that the surface modification compound of this example is a mixture of ZrO ₂ and LiF.
The average particle diameter D50 of the obtained surface-modified lithium composite oxide was 15.2 μm, the specific surface area was 0.19 m ² / g, the (110) half-width was 0.10 °, and the amount of free alkali was 0.23 mol%. It was.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 14]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a Zr content of 2.4 wt% and an S content of 3.3 wt%, in which ammonium zirconium carbonate and ammonium sulfate were dissolved in water. Thus, a surface modification precursor material was obtained. The Zr surface modification amount was 0.1 mol% with respect to the base material, and the S surface modification amount was 0.4 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 600 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Zr and S were detected on the particle surface. Moreover, as a result of measuring a powder X-ray diffraction spectrum in a model manner as in Example 12, peaks of ZrO ₂ and Li ₂ SO ₄ were detected. From this, it is presumed that the surface modification compound of this example is a mixture of ZrO ₂ and Li ₂ SO ₄ .
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 15]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having an Al content of 0.7% by weight obtained by diluting basic aluminum lactate with water to obtain a surface modification precursor material. It was. The Al surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, more Al was detected on the particle surface than inside the particle. Moreover, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of Al ₂ O ₃ was detected. From this, it is presumed that the surface modifying material of this example is Al ₂ O ₃ .
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 16]
For 100 g of the lithium-containing composite oxide obtained in Example 2, 4 g of a surface modification solution having an Al content of 0.7% by weight and P of 0.8% by weight, obtained by dissolving basic aluminum lactate and ammonium dihydrogen phosphate in water. The surface modification precursor raw material was obtained by spraying and mixing. The Al surface modification amount was 0.1 mol% relative to the base material, and the P surface modification amount was 0.1 mol%. This surface-modified precursor raw material was heat-treated at 600 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, more Al and P were detected on the particle surface than inside the particle. Moreover, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of AlPO ₄ was detected. From this, it is presumed that the surface modification compound of this example is AlPO ₄ .
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 17]
To 100 g of the lithium-containing composite oxide obtained in Example 2, 4 g of a surface modification solution having a Ti content of 1.2% by weight obtained by diluting titanium lactate with water was sprayed and mixed to obtain a surface modification precursor raw material. The Ti surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Ti was detected on the particle surface. Moreover, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, peaks of TiO ₂ and LiTiO ₂ were detected. From this, it is presumed that the surface modification compound of this example is a mixture of TiO ₂ and LiTiO ₂ .
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 18]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a Mg content of 0.6% by weight in which magnesium hydroxide was dissolved in water to obtain a surface modification precursor material. . The Mg surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, more Mg was detected on the particle surface than inside the particle. Further, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of MgO was detected. From this, it is estimated that the surface modification compound of a present Example is MgO.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 19]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having an F content of 3.0 wt% in which ammonium fluoride was dissolved in water to obtain a surface modification precursor material. . The F surface modification amount was 0.6 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 600 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, F was detected on the particle surface. Moreover, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of LiF was detected. From this, it is estimated that the surface modification compound of a present Example is LiF.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 20]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a P content of 3.2 wt% in which ammonium dihydrogen phosphate was dissolved in water to obtain a surface modification precursor raw material. Obtained. The P surface modification amount was 0.4 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 600 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, P was detected on the particle surface. Moreover, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of Li ₃ PO ₄ was detected. Therefore, the surface modifying compound of this example is presumed to be Li ₃ PO _4.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 21]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a Zn content of 1.7 wt% in which zinc acetate was dissolved in water to obtain a surface modification precursor material. The Zn surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.

As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Zn was detected on the particle surface. Moreover, as a result of measuring a powder X-ray diffraction spectrum in a model manner as in Example 12, a ZnO peak was detected. From this, it is estimated that the surface modification compound of a present Example is ZnO.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 22]
100 g of the lithium-containing composite oxide obtained in Example 2 was immersed in 40 g of a surface modification solution having a Nb content of 0.2% by weight in which niobium oxide and citric acid were dissolved in water, mixed and dried to obtain a surface modification precursor. Body material was obtained. The Nb surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Nb was detected on the particle surface. Moreover, as a result of measuring a powder X-ray diffraction spectrum in a model manner as in Example 12, a peak of Nb ₂ O ₅ was detected. Therefore, the surface modifying compound of this example is presumed to be Nb ₂ O _5.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 23]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a W content of 4.7 wt% in which ammonium metatungstate was dissolved in water to obtain a surface modification precursor material. . The surface modification amount of W was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.

As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, W was detected on the particle surface. Further, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of WO ₃ was detected. Therefore, the surface modifying compound of this example is presumed to be WO _3.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 24]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a Y content of 2.3 wt% obtained by dissolving yttrium acetate in water to obtain a surface modification precursor material. The Y surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Y was detected on the particle surface. Further, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of Y ₂ O ₃ was detected. Therefore, the surface modifying compound of this example is presumed that is Y ₂ O _3.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 25]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a La content of 3.6% by weight in which lanthanum acetate was dissolved in water to obtain a surface modification precursor material. The amount of La surface modification was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, La was detected on the particle surface. Moreover, as a result of measuring a powder X-ray diffraction spectrum in a model manner as in Example 12, a peak of La ₂ O ₃ was detected. Therefore, the surface modifying compound of this example is presumed to be La ₂ O _3.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 26]
100 g of the lithium-containing composite oxide obtained in Example 2 was sprayed and mixed with 4 g of a surface modification solution having a Gd content of 4.0% by weight in which gadolinium acetate was dissolved in water to obtain a surface modification precursor material. The amount of Gd surface modification was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Gd was detected on the particle surface. Moreover, as a result of measuring a powder X-ray diffraction spectrum in a model manner as in Example 12, a peak of Gd ₂ O ₃ was detected. Therefore, the surface modifying compound of this example is presumed to be Gd ₂ O _3.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 27]
Based on 100 g of the lithium-containing composite oxide obtained in Example 2, 4 g of a surface modification solution having a Zr content of 2.4% by weight diluted with ammonium zirconium carbonate with water, and a Gd content of 4.0 with gadolinium acetate dissolved in water. A surface modification precursor raw material was obtained by spraying and mixing 4 g of a weight percent surface modification solution. The Zr surface modification amount was 0.1 mol% with respect to the base material, and the Gd surface modification amount was 0.1 mol% with respect to the base material. This surface-modified precursor raw material was heat-treated at 500 ° C. for 12 hours in an air atmosphere to obtain a surface-modified lithium-containing composite oxide powder.
As a result of analyzing the cross section of the obtained surface-modified lithium-containing composite oxide by EDX, Gd and Zr were detected on the particle surface. Moreover, as a result of measuring the powder X-ray diffraction spectrum in a model manner as in Example 12, the peak of Gd ₂ Zr ₂ O ₇ was detected. Therefore, the surface modifying compound of this example is presumed to be _Gd 2 _Zr 2 _{O 7.}
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 28]
A tin oxide powder was used instead of the zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: Sn in the mixed powder was 1.00: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 Sn _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 29]
Germanium oxide powder was used instead of zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: Ge in the mixed powder was 1.00: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 Ge _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 30]
Boron oxide powder is used instead of zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: B in the mixed powder is 1.00: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 B _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 31]
Instead of zirconium oxide powder, ammonium dihydrogen phosphate powder was used, and the molar ratio of Li: Co: Ni: Al: P in the mixed powder was 1.00: 0.90: 0.08: 0.01: 0. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that .01 was changed.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 P _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 32]
Zinc oxide powder was used instead of zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: Zn in the mixed powder was 1.00: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 Zn _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 33]
Yttrium oxide powder was used instead of zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: Y in the mixed powder was 1.00: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 Y _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 34]
A lanthanum oxide powder was used instead of the zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: La in the mixed powder was 1.00: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 La _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 35]
Niobium oxide powder was used instead of zirconium oxide powder, and the molar ratio of Li: Co: Ni: Al: Nb in the mixed powder was 1.00: 0.90: 0.08: 0.01: 0.01. A lithium-containing composite oxide was synthesized in the same manner as in Example 10 except that.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 Nb _0.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 36]
Li: Co: Ni: Al: Mg: F in mixed powder using lithium carbonate powder, cobalt oxyhydroxide powder, basic nickel carbonate powder, aluminum hydroxide powder, magnesium hydroxide powder, and lithium fluoride powder A lithium-containing composite oxide was synthesized in the same manner as in Example 1, except that the molar ratio was 1.00: 0.90: 0.08: 0.01: 0.01: 0.01. Li was the sum of lithium carbonate and lithium fluoride.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.08 Al _0.01 Mg _0.01 O _1.995 F _0.01 .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 37]
Instead of cobalt oxyhydroxide powder and basic nickel carbonate powder, a coprecipitated oxyhydroxide having a Co: Ni molar ratio of 92: 8 was used, and Li: (Co + Ni): Al: Mg: Zr in the mixed powder. A lithium-containing composite oxide was synthesized in the same manner as in Example 2 except that the molar ratio was 1.02: 0.979: 0.01: 0.01: 0.001.
The composition of the obtained lithium-containing composite oxide was Li _1.01 (Co _0.901 Ni _0.078 Al _0.01 Mg _0.01 Zr _0.001 ) _0.99 O ₂ This lithium-containing composite Using the oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 38]
The same as Example 37 except that the zirconium oxide powder was not mixed and the molar ratio of Li: (Co + Ni): Al: Mg in the mixed powder was 1.02: 0.98: 0.01: 0.01. Thus, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.01 (Co _0.902 Ni _0.078 Al _0.01 Mg _0.01 ) _0.99 O _2. As a material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 39]
The same as Example 37 except that the magnesium oxide powder was not mixed and the molar ratio of Li: (Co + Ni): Al: Zr in the mixed powder was 1.03: 0.98: 0.01: 0.01. Thus, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.015 (Co _0.902 Ni _0.078 Al _0.01 Zr _0.01 ) _0.985 O _2. As a material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Example 40]
Coprecipitated oxyhydroxide having a Co: Ni: Al: Mg molar ratio of 90: 8: 1: 1 instead of cobalt oxyhydroxide powder, basic nickel carbonate powder, aluminum hydroxide powder and magnesium hydroxide powder And a lithium-containing composite oxide was synthesized in the same manner as in Example 8 except that the molar ratio of Li: (Co + Ni + Al + Mg) in the mixed powder was 1.02: 1.00.
The composition of the obtained lithium-containing composite oxide was Li _1.01 (Co _0.90 Ni _0.08 Al _0.01 Mg _0.01 ) _0.99 O _2. As a material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 1]
The basic nickel carbonate powder was not mixed, and the molar ratio of Li: Co: Al: Mg: Zr in the mixed powder was 1.02: 0.979: 0.01: 0.01: 0.001 In the same manner as in Example 1, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.01 (Co _0.979 Al _0.01 Mg _0.01 Zr _0.001 ) _0.99 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 2]
Example 1 except that the molar ratio of Li: Co: Ni: Al: Mg: Zr in the mixed powder was 0.98: 0.699: 0.28: 0.01: 0.01: 0.001 In the same manner, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.99 (Co _0.699 Ni _0.28 Al _0.01 Mg _0.01 Zr _0.001 ) _1.01 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 3]
Except that the aluminum hydroxide powder was not mixed and the molar ratio of Li: Co: Ni: Mg: Zr in the mixed powder was 1.03: 0.90: 0.07: 0.015: 0.015, In the same manner as in Example 1, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.015 (Co _0.90 Ni _0.07 Mg _0.015 Zr _0.015 ) _0.985 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 4]
In the same manner as in Example 8, except that the molar ratio of Li: Co: Ni: Al: Mg in the mixed powder was 0.97: 0.86: 0.08: 0.01: 0.05, lithium was used. Containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _0.985 (Co _0.86 Ni _0.08 Al _0.01 Mg _0.05 ) _1.015 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 5]
In the same manner as in Example 10 except that the molar ratio of Li: Co: Ni: Al: Zr in the mixed powder was 1.03: 0.86: 0.08: 0.01: 0.05, lithium was used. Containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.015 (Co _0.86 Ni _0.08 Al _0.01 Zr _0.05 ) _0.985 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50, specific surface area, (110) half-value width and free alkali amount of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 6]
Example except that aluminum hydroxide powder and zirconium oxide powder were not mixed and the molar ratio of Li: Co: Ni: Mg in the mixed powder was 1.00: 0.90: 0.05: 0.05. In the same manner as in Example 1, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.90 Ni _0.05 Mg _0.05 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50 and specific surface area of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 7]
Implementation was carried out except that the basic nickel carbonate powder and zirconium oxide powder were not mixed, and the molar ratio of Li: Co: Al: Mg in the mixed powder was 1.00: 0.85: 0.10: 0.05. In the same manner as in Example 1, a lithium-containing composite oxide was synthesized.
The composition of the obtained lithium-containing composite oxide was Li _1.00 Co _0.85 Al _0.10 Mg _0.05 O ₂ .
Using this lithium-containing composite oxide as a base material, surface modification was performed in the same manner as in Example 1 to obtain a surface-modified lithium-containing composite oxide.
In the same manner as in Example 1, measurement of the average particle diameter D50 and specific surface area of the obtained surface-modified lithium composite oxide and battery performance evaluation were performed.

[Comparative Example 8]
The lithium-containing composite oxide obtained in Example 2 was subjected to battery performance evaluation by the same method as in Example 1 using the base material as it was as the positive electrode active material without performing surface modification.

  Table 1-1 to Table 1 show the average particle diameter D50, specific surface area, (110) half width, free alkali amount, and battery performance evaluation results of the surface-modified lithium composite oxides of Examples 1 to 40 and Comparative Examples 1 to 8. -3.

  The surface-modified lithium-containing composite oxide of the present invention can be used even under a high charging voltage, and can be used as a positive electrode for a lithium secondary battery excellent in battery characteristics such as discharge capacity, discharge average voltage, cycle durability, and safety. Available.

Claims (28)

The surface of the lithium-containing composite oxide represented by the general formula (1) is modified with a surface modifying compound containing at least one element selected from the group consisting of elements of group S1 and group S2. A surface-modified lithium-containing composite oxide for a positive electrode of a lithium ion secondary battery.
_{Li 1 + x (Co (1} -a-b-m) Ni a Al b M m) 1-x O 2- (f / 2) F f ··· (1)
(However, group S1 is a group consisting of Al, Zr, Ti, Mg, Zn, Nb, Mo, Ta, W and rare earth, and group S2 is a group consisting of F, P, and S. M is At least one selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Na, K, B, C, Si, P, S, Zn, Ga, Bi, Group 2 elements, and rare earth elements Element, and -0.05 ≦ x ≦ 0.05, 0 <a ≦ 0.25, 0 < b ≦ 0.05, 0 <m ≦ 0.04, 0 ≦ f ≦ 0.05.   M is at least one selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Na, K, B, C, Si, P, S, Zn, Y, La, Ce, and Group 2 elements The surface-modified lithium-containing composite oxide according to claim 1, which is a seed element.   The surface-modified lithium-containing composite oxide according to claim 1, wherein the group S1 is a group consisting of Al, Zr, Ti, Mg, Zn, Nb, W, Y, La, and Gd.   In the general formula (1), f = 0, M is at least one element selected from the group consisting of transition metals other than Co and Ni, Sn, Ge, Zn, and Group 2 elements, The surface-modified lithium-containing composite oxide according to claim 1, wherein S1 is a group consisting of Al, Zr, Ti, and Mg, and the surface modification compound includes at least one element selected from group S1.   The surface-modified lithium-containing composite oxide according to claim 1, wherein 0.05 ≦ a + b + m ≦ 0.30.   The surface-modified lithium-containing composite oxide according to claim 1, wherein 0.005 ≦ b + m ≦ 0.07.   The surface-modified lithium according to any one of claims 1 to 4, wherein M is at least one element selected from the group consisting of Mg, Ca, Sr, Ti, Zr, Nb, W, Ge, Sn, and Zn. Containing complex oxide. M is at least one element selected from the group consisting of Mg, Ti, and Zr, and the lithium-containing composite oxide is represented by the general formula (2). Surface-modified lithium-containing composite oxide.
Li _{1 + x} (Co _(1-ab-m) Ni _a Al _b Mg _c Zr _d Ti _e ) _1-x O ₂ (2)
(However, −0.05 ≦ x ≦ 0.05, 0 <a ≦ 0.25, 0 <b ≦ 0.05, 0 <m ≦ 0.04, 0 ≦ c ≦ 0.02, 0 ≦ d ≦ 0.02, 0 ≦ e ≦ 0.02, m = c + d + e.) Ratio of the total number of moles of group S1 elements contained in the surface modification compound to the number of moles of lithium-containing composite oxide ((total number of moles of elements of group S1) / number of moles of lithium-containing composite oxide ) Is 0.0001 to 0.03, The surface-modified lithium-containing composite oxide according to any one of claims 1 to 8 . The surface-modifying compound includes at least one element selected from group S1 and at least one element selected from group S2, and further includes a total number of moles of the elements of group S2 in the lithium-containing composite oxidation. the ratio of moles object surface modified lithium according to any one of claims 1-9 ((number of moles) / lithium-containing composite oxide of the total of group S2) is 0.0001 to 0.03 Containing complex oxide. The surface modification compound is composed of Zr (CO ₃ ) ₂ , ZrOCO ₃ , ZrO ₂ , Li ₃ PO ₄ , LiF, Li ₂ SO ₄ , Al ₂ O ₃ , AlPO ₄ , TiO ₂ , LiTiO ₂ , and MgO. surface modified lithium-containing complex oxide according to any one of claims 1-10 is at least one selected from the. The surface modification compound is at least one selected from the group consisting of ZnO, Nb ₂ O ₅ , WO ₃ , Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ , and Gd ₂ Zr ₂ O _7. Item 12. The surface-modified lithium-containing composite oxide according to any one of Items 1 to 11 . Average particle size of 5 to 25 [mu] m, a specific surface area is less than 0.5 m ² / g surface modified lithium-containing complex oxide according to any one of claims 1 to 12. The surface according to any one of claims 1 to 13 , wherein the half width of the diffraction peak of the (110) plane having 2θ of 65 ± 0.5 ° in X-ray diffraction using Cu-Kα rays is 0.15 ° or less. Modified lithium-containing composite oxide. The surface-modified lithium-containing composite oxide according to any one of claims 1 to 14 , wherein the amount of free alkali is 0.5 mol% or less.   The positive electrode for lithium ion secondary batteries containing the surface modification lithium containing complex oxide in any one of Claims 1-15. A positive electrode for a lithium secondary battery containing a mixture of two or more kinds of surface-modified lithium-containing composite oxides according to any one of claims 1 to 15 , having different average particle diameters. And surface modified lithium-containing oxide according to any one of claims 1 to 15 surface modified lithium-containing oxides different from lithium-containing composite oxide (I) and a positive electrode for a lithium ion secondary battery containing a mixture of. The lithium- containing composite oxide (I) is a lithium nickel cobalt manganese-containing composite oxide having a layered structure, a lithium manganese-containing composite oxide having a spinel structure, a lithium iron-containing phosphate compound having an olivine structure, or yLi ₂ QO ₃ · (1-y) LiRO ₂ (where 0 <y <1, Q is one or more metal elements having an average oxidation number of 4+, and R is one type having an average oxidation number of 3+) The positive electrode for a lithium ion secondary battery according to claim 18 , wherein the positive electrode is a metal element as described above. A positive electrode for a lithium ion secondary battery according to any one of claims 16-19 positive electrode density of 3.5 g / cm ³ or more. A positive electrode for a lithium ion secondary battery according to any one of claims 16-20, negative electrode, separator, and a lithium ion secondary battery containing the electrolyte. The lithium ion secondary battery according to claim 21 , wherein the charge potential of the positive electrode is 4.5 V or more on the basis of Li ⁺ / Li. The negative electrode is at least one selected from the group consisting of carbon materials, lithium-titanium-containing composite oxides, lithium, metals that can be alloyed with lithium, alloys of these metals, oxides containing these metals, and nitrides The lithium ion secondary battery according to claim 21 or 22 , comprising: The lithium ion secondary battery according to any one of claims 21 to 23 , wherein the separator is at least one of a nonwoven fabric or a resin porous membrane. The lithium ion secondary battery according to any one of claims 21 to 23 , wherein the separator is a laminate of porous layers having different melting points. The lithium ion secondary battery according to any one of claims 21 to 23 , wherein the separator contains heat-resistant inorganic fine particles. The lithium ion secondary battery according to any one of claims 21 to 26 , wherein the electrolytic solution contains at least one selected from the group consisting of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. The electrolytic solution contains, as an additive, at least one selected from the group consisting of VC, cyclohexylbenzene, fluorobenzene, phosphate ester compounds, 4-fluoroethylene carbonate, propane sultone, succinonitrile, and ethylene sulfite The lithium ion secondary battery according to any one of claims 21 to 27 .