Lithium-ion secondary battery positive electrode material additive

Abstract

The present invention provides a positive electrode material for lithium ion secondary batteries and a method for producing the same, which will enable lithium secondary batteries to have high output characteristics (load characteristics and rate characteristics). [Solution] A lithium ion secondary battery positive electrode material having a layered crystal structure, which is any of a LiCoO2-based, Li(Ni,Co,Al)O2-based, and Li(Ni,Co,Mn)O2-based positive electrode material, has a cation B with an ionic radius larger than that of lithium ions and a valence of 2 or more present between the layers, and preferably a cation A with an ionic radius smaller than that of lithium ions and a valence of 2 or more present between the layers. A method for producing a lithium ion secondary battery positive electrode material includes preparing a composite oxide containing cations A and B, preparing a positive electrode material having a layered crystal structure, mixing the composite oxide with the positive electrode material, and substituting the cations A and B between the layers of the positive electrode material.

Description

[Technical field]

[0001] The present invention relates to a positive electrode material for a lithium ion secondary battery, an additive used in the production of the positive electrode material, a method for producing a positive electrode material for a lithium ion secondary battery using the additive, and a lithium ion secondary battery comprising the positive electrode material. [Background technology]

[0002] Lithium-ion secondary batteries have excellent electromotive force and energy density, and are widely used as batteries for portable electronic and communication devices such as small video cameras, mobile phones, and laptop computers. It is generally said that the characteristics of the positive electrode active material determine the characteristics of lithium-ion secondary batteries, and positive electrode active materials with layered crystal structures are used not only in portable electronic devices but also in mobile and large-scale lithium-ion secondary batteries for automobiles and power storage equipment due to their large capacity. In these fields, there is a high demand for technology, especially for output characteristics (load characteristics and rate characteristics), due to the way they are used.

[0003] For example, the following conventional techniques are related to improving the output characteristics of positive electrode materials having a layered crystal structure. x Co 1-y Me y O 2-a (Me represents one or more metal elements selected from V, Cu, Zr, Zn, Mg, Al, and Fe; x is a value of 0.9≦x≦1.1, y is a value of 0≦y≦0.01, and a is a value of -0.1≦a≦0.1.) is dry-mixed with at least one metal oxide selected from Mg, Ti, and Zr on the particle surface of a composite oxide represented by the formula (1), and heat-treated at 200 to 700°C to adhere the metal oxide to the particle surface of the composite oxide, thereby improving output characteristics. However, the test was limited to 1C (a test mode in which charging and discharging are repeated in one hour), and does not meet the technical requirements for recent lithium-ion secondary batteries that require rapid charging.

[0004] In addition, Patent Document 2 describes a method for producing a nickel-cobalt-manganese compound particle powder, a zirconium raw material, and a lithium raw material by mixing and sintering the mixture, the zirconium compound being present on the particle surface, and the chemical formula of the zirconium compound is Li x (Zr 1-y A y )O z A technology has been disclosed for producing a lithium ion secondary battery having low electrical resistance at high temperatures and excellent high-temperature rate characteristics at high temperatures by using a lithium composite oxide particle powder represented by the formula (x, y, and z are 2.0≦x≦8.0, 0≦y≦1.0, 2.0≦z≦6.0) and having a Zr content of 0.05 to 1.0 wt % as a positive electrode active material; however, the rate characteristics (output characteristics) at room temperature where lithium ion secondary batteries are most commonly used are not improved.

[0005] In addition, in Patent Document 3, Li 1.03 Chief of Staff 2.02 A technology for producing a positive electrode active material is disclosed, which is characterized in that particles are provided with a coating layer made of an oxide containing lithium and at least one coating element selected from nickel and manganese, and a surface layer made of an oxide containing yttrium in at least a part of the coating layer. This patent document only shows the improvement of cycle characteristics, and does not describe or suggest output characteristics.

[0006] Patent Document 4 discloses a technology for reducing battery resistance at 25° C., in which a lithium transition metal composite oxide having a layered crystal structure containing at least lithium and nickel is used as a core particle for a positive electrode active material used in lithium ion secondary batteries, and a coating layer made of a composite oxide containing lithium, yttrium, and zirconium is formed on at least a part of the surface of the core particle. In this technology, when Y or Zr is present in the crystal lattice of the lithium transition metal composite oxide, a sufficient effect cannot be obtained.

[0007] In addition, Patent Document 5 discloses a layered crystal structure, (Li 1-x Mg x ) 1+m (Co 1-y M 1y ) 1+n M 2 z O2 (However, M 1 represents a single element or a group of elements including at least Mn, M 2 represents a single element or a group of elements including at least one element selected from the group consisting of Na, Sr, Ba, and F, and 0.001≦x≦0.08, 0.001≦y≦0.08, 0≦z≦0.05, -0.05≦m≦0.05, and -0.05≦n≦0.05. ) and a non-aqueous secondary battery electrode containing the same as an active material are disclosed. Since the crystal structure of this lithium-cobalt-containing composite oxide is stable even under high voltage, it is said that a non-aqueous secondary battery having high capacity and excellent charge / discharge cycle characteristics even under high voltage can be obtained. The technology describes stabilization of the crystal structure, but does not describe adjustment of the interlayer. In addition, only improvement of cycle characteristics is shown, and there is no description of output characteristics.

[0008] Patent Document 6 discloses a positive electrode material for non-aqueous electrolyte secondary batteries, in which a coating layer is formed on the surface of a positive electrode active material made of a lithium-cobalt-containing composite oxide having a layered crystal structure containing at least one element selected from the group consisting of Cr, Mn, Fe, Ni, Zr, Ti, Mo, V, Al, B, and Ge, and Mg, and the coating layer is made of an oxide containing lithium, aluminum, and boron, which has a different composition from the active material. It is said that a non-aqueous electrolyte secondary battery using this as a positive electrode can extract a large capacity in a high voltage region during discharge and exhibits excellent charge-discharge cycle characteristics. This technology describes stabilization of the crystal structure, but does not describe adjustment between layers. In addition, only improvement of cycle characteristics is shown, and there is no description of output characteristics. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2003-221234 A [Patent Document 2] JP 2013-193888 A [Patent Document 3] JP 2007-242318 A [Patent Document 4] JP 2018-55808 A [Patent Document 5] JP 2015-156363 A [Patent Document 6] JP 2015-213038 A Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above problems, and aims to provide a positive electrode material for a non-aqueous electrolyte secondary battery having excellent output characteristics in which the charge / discharge capacity is unlikely to decrease even when the current value during charging / discharging is increased, and a method for producing the same. Another aim of the present invention is to provide a composite oxide for producing a positive electrode material for a non-aqueous electrolyte secondary battery having excellent output characteristics in which the charge / discharge capacity is unlikely to decrease even when the current value during charging / discharging is increased. [Means for solving the problem]

[0011] The present inventors have conducted various studies in order to solve the above problems, and have found that a positive electrode material for use in a lithium ion secondary battery, which has a layered crystal structure and in which the spaces between the lithium layers are expanded, is extremely effective in improving output characteristics by substituting a cation B, which has an ionic radius larger than that of lithium ions and has a valence of two or more, for lithium ions between the layers of the positive electrode material having a layered crystal structure, and thus completed the present invention.

[0012] The present invention has been completed based on the above findings, and the gist of the invention is as follows. (1) A positive electrode material for a lithium ion secondary battery, characterized in that a cation B having an ionic radius larger than that of lithium ion and a valence of 2 or more is present between layers of the positive electrode material having a layered crystal structure. Here, the radius of lithium ion refers to the Shannon ionic radius, which is the value of the ionic radius for 6 coordinates, 0.76 Å, reported in "Shannon et al., Acta A 32(1976)751". The same applies hereinafter.

[0013] (2) The positive electrode material for a lithium ion secondary battery according to (1), characterized in that a cation A having an ionic radius smaller than that of lithium ion and a valence of divalent or more and a cation B having an ionic radius larger than that of lithium ion and a valence of divalent or more are present between layers of the positive electrode material having a layered crystal structure.

[0014] (3) A cation B with a larger ionic radius than the lithium ion is Ca 2+ ,Sr 2+ ,Ba 2+ ,In 3+ ,Y 3+ ,La 3+ ,Ce 3+ ,Ce 4+ ,Pr 3+ ,Nd 3+ ,Sm 3+ ,EU 3+ ,Gd 3+ ,Tb 3+ ,Dy 3+ ,Ho 3+ ,Er 3+ ,Tm 3+ ,Yb 3+ ,Lu 3+ ,Bi 3+ The positive electrode material for a lithium ion secondary battery according to (1) or (2), characterized in that it is one or more selected from the following:

[0015] (4) Cation A, which has an ionic radius smaller than that of lithium ion, is Mg 2+ ,Al 3+ ,Ga3+ ,Sc 3+ ,Si 4+ ,Ge 4+ ,Ti 4+ ,Zr 4+ ,Hf 4+ ,V 5+ ,Nb 5+ ,Ta 5+ ,Mo 4+ ,Mo 5+ ,Mo 6+ ,W 4+ ,W 5+ ,W 6+ The positive electrode material for a lithium ion secondary battery according to (2) or (3), characterized in that the positive electrode material is one or more selected from the following:

[0016] (5) The lithium ion secondary battery positive electrode material according to any one of (1) to (4), characterized in that the parent phase of the positive electrode material having a layered crystal structure is any one of LiCoO2-based, Li(Ni,Co,Al)O2-based, and Li(Ni,Co,Mn)O2-based.

[0017] (6) The base composition (the composition before the addition of cations A and B) has the general formula Li 1+m Ni x Co y Mn 1-x-y-w-m M w O 2+θ wherein M is one or two elements selected from Al and Mg, m is in the ranges of -0.05≦m≦0.10, x is in the range of 0≦x≦1.0, y is in the range of 0≦y≦1.0, w is in the range of 0≦w≦0.2, 0.4≦m+x+y+w≦1.0, and θ is a value determined so as to satisfy a charge neutrality condition.

[0018] (7) A lithium ion secondary battery comprising the positive electrode material for lithium ion secondary batteries according to any one of (1) to (6).

[0019] (8) A method for producing a positive electrode material for a lithium ion secondary battery according to any one of (2) to (6), comprising the steps of: preparing a composite oxide containing the cations A and B; preparing a positive electrode material having a layered crystal structure; and mixing the composite oxide and the positive electrode material, followed by firing, thereby substituting the cations A and B with lithium ions between the layers of the positive electrode material.

[0020] (9) A method for producing a positive electrode material for a lithium ion secondary battery according to any one of (2) to (6), comprising the steps of: preparing a composite oxide containing the cations A and B; preparing a mixture of a lithium salt, a precursor of a positive electrode material having a layered crystal structure, and the composite oxide; and calcining the mixture, thereby inserting the cations A and B between the layers of the positive electrode material having the layered crystal structure.

[0021] (10) A positive electrode material additive for a lithium ion secondary battery, which is a composite oxide containing the cation B described in (3) and the cation A described in (4). The present invention also includes the following lithium ion secondary battery positive electrode material additive. [1] An additive used in the manufacture of a positive electrode material having a layered crystal structure for use in a lithium ion secondary battery, comprising a cation B having an ionic radius larger than that of a lithium ion and a valence of 2 or more, and a cation C having an ionic radius smaller than that of a lithium ion. and the valence is 2 or more. 1. A positive electrode material additive for a lithium ion secondary battery, which is a composite oxide containing a cation A. [2] The additive for a positive electrode material for a lithium ion secondary battery according to [1], wherein the valence of the cation A is 2 or more. [3] The cation B is Ca 2+ ,Sr 2+ ,Ba 2+ ,In 3+ ,Y 3+ ,La 3+ ,Ce 3+ ,Ce 4+ ,Pr 3+ ,Nd3+ ,Sm 3+ ,EU 3+ ,Gd 3+ ,Tb 3+ ,Dy 3+ ,Ho 3+ ,Er 3+ ,Tm 3+ ,Yb 3+ ,Lu 3+ ,Bi 3+ The additive for a positive electrode material for a lithium ion secondary battery according to [1] or [2] above, characterized in that it is one or more selected from the following: [4] The cation A is Mg 2+ ,Al 3+ ,Ga 3+ ,Sc 3+ ,Si 4+ ,Ge 4+ ,Ti 4+ ,Zr 4+ ,Hf 4+ ,V 5+ ,Nb 5+ ,Ta 5+ ,Mo 4+ ,Mo 5+ ,Mo 6+ ,W 4+ ,W 5+ ,W 6+ The additive for a positive electrode material for a lithium ion secondary battery according to any one of the above [1] to [3], characterized in that the additive is one or more selected from the following: Effect of the Invention

[0022] According to the present invention, it is possible to provide a positive electrode material powder for use in lithium ion secondary batteries, which can be used to manufacture a positive electrode for a lithium secondary battery having high output characteristics. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a conceptual diagram illustrating the mechanism of improving output characteristics according to the present invention, showing a conceptual diagram before cation A and cation B are inserted between the layers of a positive electrode material for a lithium ion secondary battery having a layered crystal structure. [Diagram 2]FIG. 1 is a conceptual diagram showing the mechanism of improving output characteristics according to the present invention, showing a conceptual diagram after cation A and cation B are inserted between the layers of a positive electrode material for a lithium ion secondary battery having a layered crystal structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The present invention will be described in detail below.

[0025] Typically, lithium-ion secondary batteries use lithium transition metal composite oxides with a layered crystal structure, but the present invention makes it possible to produce positive electrodes for lithium secondary batteries with high output characteristics that can absorb and release stored electricity in a short period of time even in situations where such lithium-ion secondary batteries require more current than ever before, and to provide a positive electrode material powder for use in lithium-ion secondary batteries.

[0026] The positive electrode material for lithium ion secondary batteries having a layered crystal structure with expanded interlayer spaces according to the present invention is a positive electrode material for lithium ion secondary batteries characterized in that a cation B having an ionic radius larger than that of lithium ions and a valence of divalent or greater is present between the layers of the positive electrode material having a layered crystal structure.

[0027] In the present invention, since it is necessary to widen the gap between the layers, cation B must have a larger ionic radius than lithium ions. In addition, when a monovalent cation is used, there is a risk that the monovalent cation may be released from the positive electrode material having a layered crystal structure together with the insertion and release of lithium ions accompanying charge and discharge, so the valence of cation B must be divalent or more.

[0028] The cation B for spreading the interlayer is preferably relatively harmless, inexpensive, and easily available from the viewpoint of industrial materials. An example of this is Y. 3+ ,La 3+ In addition, Ca 2+ ,Sr 2+ ,Ba 2+ ,In 3+ ,Ce 3+,Ce 4+ ,Pr 3+ ,Nd 3+ ,Sm 3+ ,EU 3+ ,Gd 3+ ,Tb 3+ ,Dy 3+ ,Ho 3+ ,Er 3+ ,Tm 3+ ,Yb 3+ ,Lu 3+ ,Bi 3+ One or more selected from the above may be mentioned.

[0029] From the viewpoint of industrial materials, it is desirable for cation A, which has an ionic radius smaller than that of lithium ion, to be relatively harmless, less expensive, and more readily available. An example of this is Zr. 4+ In addition, Mg 2+ ,Al 3+ ,Ga 3+ ,Sc 3+ ,Si 4+ ,Ge 4+ ,Ti 4+ ,Hf 4+ ,V 5+ ,Nb 5+ ,Ta 5+ ,Mo 4+ ,Mo 5+ ,Mo 6+ ,W 4+ ,W 5+ ,W 6+ Examples of the compounds include one or more selected from the above.

[0030] Figure 1 shows a schematic diagram of the layered crystal structure of the positive electrode material for lithium-ion secondary batteries before and after cations A and B are inserted between the layers. Figure 2 shows a schematic diagram of the material after insertion. + stands for lithium ion, M n+ The metal element ions (nickel, cobalt, manganese, aluminum, magnesium) that make up the positive electrode material with a layered crystal structure are mixed with O 2- The oxygen ions that make up the positive electrode material, which has a layered crystal structure, are g+ A is a cation with a smaller ionic radius than the lithium ion with a valence of g, and B is a cation with a smaller ionic radius than the lithium ion with a valence of g.h+ indicates a cation B that has a larger ionic radius than the lithium ion with a valence of h.

[0031] When cation B, which is larger than lithium ions, is inserted between the layers of the positive electrode material for lithium ion secondary batteries having a layered crystal structure as shown in Figure 1, it is thought that the simultaneous use of cation A, which has an ionic radius smaller than that of lithium ions, makes it easier to insert cation B. The reason for this is that when cation A, which has an ionic radius smaller than that of lithium ions, is used simultaneously, the ionic radius of cation A is smaller than that of lithium ions, so it is thought that it is relatively easy to replace the lithium ions between the layers. It is thought that holes are generated at the adjacent points of the sites replaced by cation A between the layers due to the difference in valence with the lithium ions. In addition, in the positive electrode material for lithium ion secondary batteries having a layered crystal structure, negatively charged oxygen ion layers exist on the top and bottom surfaces of the lithium layer. Here, around the positive holes generated between the layers due to the replacement of cation A and the difference in valence with lithium ions, these negatively charged oxygen ion layers are in close proximity to each other, so it is thought that the repulsion between the negative charges originating from the oxygen ion layers causes the layers to expand. In other words, the gap between the layers becomes larger than the gap where lithium ions could enter and exit, making it easier for cation B, which has a larger ionic radius than lithium ions, to insert between the layers, resulting in the state shown in Figure 2.

[0032] In order to obtain this effect, it is desirable that cations A and B are present in close proximity to each other, and it is desirable that cations A and B are in the form of a complex compound.

[0033] In order to prevent the compound of cation A and cation B from decomposing during firing, it is preferable to make it into a composite oxide. 0.28 Zr 0.72 O 1.86There is no particular restriction on the method for synthesizing a composite oxide in which cation A and cation B are combined, but for example, the composite oxide can be produced by sequentially carrying out a step of preparing a solution containing cation A and cation B, or a solution containing one of cations A and B in a dispersion containing particles of the other cation, and then adding a base to the solution to obtain a hydroxide slurry containing cations A and B, and a step of separating the hydroxide slurry into a solid liquid, washing, drying, and calcining the hydroxide slurry.

[0034] The preferred compounding ratio (molar ratio) of cation A to cation B is A:B=15:85 to 85:15, and more preferably A:B=28:72 to 72:28.

[0035] The lithium transition metal composite oxide that can be suitably used in the present invention has a base composition represented by the general formula Li 1+m Ni x Co y Mn 1-x-y-w-m M w O 2+θ where M is one or two elements selected from Al and Mg, m is in the range of -0.05≦m≦0.10, x is 0≦x≦1.0, y is 0≦y≦1.0, w is 0≦w≦0.2, 0.4≦m+x+y+w≦1.0, and θ is a value determined so as to satisfy the charge neutrality condition.

[0036] In addition, the range is set to -0.05≦m≦0.10 because, if m<-0.05, too much Ni will enter the Li layer, reducing the discharge capacity of the lithium transition metal composite oxide, and if m>0.10, excess Li will enter the transition metal layer, increasing the Ni valence and causing a decrease in discharge capacity. The range is set to 0≦x≦1.0 because this is a positive electrode material that utilizes Ni valence change, and 0≦y≦1.0 because it is the amount required according to the Ni amount to stabilize the crystal structure.

[0037] The lithium transition metal composite oxide Li 1+m Ni x Co y Mn 1-x-y-w-m Mw O 2+θ In O, M is selected as being effective for improving high-temperature characteristics, M is one or two metal elements selected from Al and Mg, and w preferably ranges from 0 ≦ w ≦ 0.2. When w > 0.2, the discharge capacity decreases, which is not preferable.

[0038] Examples of the positive electrode material for a lithium-ion secondary battery having the layered crystal structure include LiCoO2, LiNi 0.80 Co 0.15 Al 0.05 O2, LiNi 0.50 Co 0.20 Mn 0.30 O2, etc. are known.

[0039] When the mass% ratio of the compound in which cation A and cation B are combined is added to the lithium transition metal composite oxide, when the mass% of the compound in which cation A and cation B are combined is added is p with respect to 100 mass% of the lithium transition metal composite oxide, it is in the range of 0.1 < p < 2.3, and more preferably in the range of 0.5 ≦ p ≦ 2.0. This is because if the amount of the composite oxide containing cation A and cation B added is too small, the effect of enhancing the output characteristics cannot be confirmed, and conversely, if it is too large, the discharge capacity of the lithium transition metal composite oxide will decrease.

[0040] The maximum particle size of the lithium transition metal composite oxide particle powder according to the present invention is preferably less than 50 μm. When the maximum particle size is 50 μm or more, although it also depends on the designed thickness of the positive electrode plate, when preparing a slurry for positive electrode production and coating it on an aluminum foil, coating defects such as streaks are likely to occur, which is not preferable.

[0041] The BET specific surface area of the lithium composite oxide particle powder according to the present invention is preferably 15 m 2 / g or less. When the BET specific surface area exceeds 15 m 2 / g, the packing density decreases and the reactivity with the electrolyte increases, which is not preferable.

[0042] Next, a method for manufacturing the positive electrode material for a lithium-ion secondary battery of the present invention will be described.

[0043] The positive electrode material for lithium-ion secondary batteries of the present invention can be obtained by mixing, baking, and adjusting the particle size of a lithium salt, a transition metal compound that is the raw material for the positive electrode material having a layered crystal structure, and a composite oxide that contains a cation B having an ionic radius larger than that of a lithium ion and a cation A having an ionic radius smaller than that of a lithium ion.

[0044] Although the lithium salt is not particularly specified, lithium carbonate and lithium hydroxide are preferable. When y is less than 0.6, lithium carbonate is suitable, and when y is 0.6 or more, lithium hydroxide is suitable. In addition, the particle size of the lithium salt is preferably 10 μm or less in average particle size, taking into account the reactivity with the transition metal complex compound.

[0045] There is no particular designation for the transition metal compound used as the raw material for the positive electrode material having a layered crystal structure, but possible methods include using a compound containing Ni, Co, Mn, and Al that has been adjusted in advance to the base composition of the desired positive electrode material, or mixing Co compounds such as Co3O4 and Co(OH)2, Ni compounds such as NiO and Ni(OH)2, Mn compounds such as MnO, MnO2, Mn3O4, MnOOH, and Mn(OH)2, and Al compounds such as Al2O3 and Al(OH)3 to obtain the composition of the desired positive electrode material.

[0046] The mixing method is not particularly limited, but it is preferable to dry mix with a precision mixer. In the mixing and firing of the raw materials, there is a method in which a lithium salt and a transition metal compound as the raw material of the positive electrode material having a layered crystal structure are mixed, fired, and crushed to obtain a positive electrode material, and a composite oxide containing a cation B having an ionic radius larger than that of lithium ions and a cation A having an ionic radius smaller than that of lithium ions is mixed and fired, and a method in which a lithium salt, a transition metal compound as the raw material of the positive electrode material having a layered crystal structure, a composite oxide containing a cation B having an ionic radius larger than that of lithium ions and a cation A having an ionic radius smaller than that of lithium ions are all mixed and then fired.

[0047] Following the mixing, firing is performed. Examples of firing conditions include firing at a temperature of 750°C or higher and 1000°C or lower all at once, or a first firing step in which the firing temperature is maintained at 500°C or higher and 700°C or lower, and a second firing step which is performed consecutively from the first firing step without lowering the firing temperature and in which the firing temperature is maintained at 700°C or higher and 1000°C or lower, or a second firing step in which the firing temperature is once lowered from the first firing step to room temperature and then in which the firing temperature is maintained at 700°C or higher and 1000°C or lower.

[0048] In the first firing step, firing is performed for 2 to 10 hours at 500 to 700° C. The reason for setting the temperature at 500 to 700° C. is that the reaction between the Li salt and the transition metal complex compound occurs in this temperature range. In the second firing step, the mixture is fired at 700 to 1000°C, which is higher than that in the first firing step, for 5 to 30 hours in order to promote the reaction. If the temperature exceeds 1000°C, the primary particles will grow and the particles will sinter together, which is not preferable. If the temperature is less than 700°C, the primary particles will not grow sufficiently, resulting in low crystallinity. It is also not preferable because the desired composition cannot be obtained. A suitable firing time is not necessarily determined depending on the combination with the temperature, but is preferably 2 to 10 hours in the first firing step, and 5 to 30 hours in the second firing step.

[0049] The synthesized (calcined) lithium transition metal composite oxide is adjusted to a maximum particle size of 50 μm or less. There is no particular restriction on the means for adjusting the particle size, and for example, a roll mill, a jet mill, a sieve, etc. can be used.

[0050] When the lithium transition metal composite oxide according to the present invention is used as a positive electrode active material, a material capable of absorbing and releasing lithium, such as a carbon material or a lithium absorbing alloy, is used as a negative electrode active material, and a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous electrolyte solution or a resin is used as an electrolyte solution, as in the case of a normal lithium transition metal composite oxide. For example, lithium hexafluorophosphate (LiPF6) is used as a lithium salt, and a mixed solution of ethylene carbonate and diethyl carbonate is used as a non-aqueous electrolyte solution. In addition, LiClO4, LiAsF6, LiBF4, LiSO3CF3, LiN(SO3CF3)2, etc., or mixtures thereof, can be used as a lithium salt. In addition, diethyl carbonate, propylene carbonate, vinylene carbonate, etc., or mixtures thereof, and a polymer solid electrolyte (resin) having high ion conductivity and having a main chain of polyethyleneimine, etc., can be used as a non-aqueous electrolyte solution.

[0051] As described above, the positive electrode material for lithium ion secondary batteries of the present invention, which has a layered crystal structure with expanded interlayer spaces, can absorb and release stored electricity in a shorter time than ever before, and by using the active material of the present invention, a lithium ion secondary battery with high output characteristics can be produced. EXAMPLES

[0052] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to the examples.

[0053] Example 1 Chemical formula Li 1.02 Ni 0.49 Co 0.20 Mn 0.29 Lithium carbonate adjusted to be O2, transition metal complex compound (chemical formula: Ni 0.5 Co 0.2 Mn 0.3 (OH)2) as a complex oxide containing cations A and B, 0.28 Zr 0.72 O 1.86was added to the lithium transition metal composite oxide at a ratio of 0.5% by mass, dry mixed in a precision mixer, and then calcined in an air atmosphere at 650°C for 5 hours and then at 890°C for 11 hours. The mixture was then crushed and sized to synthesize a lithium transition metal composite oxide containing cations A and B.

[0054] (Examples 2 to 4, Examples 7 to 25, Examples 28 to 41, and Comparative Examples 2 and 3) In Examples 2, 7 to 25, 28 to 41, and Comparative Examples 2 and 3, Y 0.28 Zr 0.72 O 1.86 Instead of the above, a composite oxide (ABO) containing cations A and B in the component ratios shown in Tables 1 to 3 was used. n (where n is a value determined so as to satisfy the charge neutral condition for the valences of cations A and B) was used, and the preparation was carried out in the same manner as in Example 1.

[0055] (Example 5, Example 6, Comparative Example 4, Comparative Example 5) In Examples 5 and 6, and Comparative Examples 4 and 5, a composite oxide containing cations A and B was used. (ABO n (where n is a value determined so as to satisfy the charge neutral condition for the valences of cations A and B) was added to the lithium transition metal composite oxide in the mass % ratios shown in Tables 1 and 3, and the preparation was carried out in the same manner as in Example 1.

[0056] (Example 26) In Example 26, Y 0.28 Zr 0.72 O 1.86 The preparation was carried out in the same manner as in Example 1, except that a composite oxide containing cations A and B, and cation B' in the component ratios shown in Table 2 (ABB'On, where n is a value determined so as to satisfy the charge neutral condition for the valences of cations A, B, and B') was used instead of the above.

[0057] Example 27 In Example 27, Y 0.28 Zr 0.72 O 1.86The preparation was carried out in the same manner as in Example 1, except that a composite oxide containing cations A and B, and cations A' and B' in the component ratios shown in Table 2 (A A'B B'On, where n is a value determined so as to satisfy the charge neutral condition for the valences of cations A, A', B, and B') was used instead of the above.

[0058] Comparative Example 1 Chemical formula Li 1.02 Ni 0.49 Co 0.20 Mn 0.29 Lithium carbonate adjusted to be O2, transition metal complex compound (chemical formula: Ni 0.5 Co 0.2 Mn 0.3 (OH)2) was dry mixed in a precision mixer, then sintered at 650°C for 5 hours and then at 890°C for 11 hours, crushed, and sized to synthesize a lithium transition metal composite oxide.

[0059] (Example 40) Chemical formula Li 1.02 Ni 0.49 Co 0.20 Mn 0.29 Lithium carbonate adjusted to be O2, transition metal complex compound (chemical formula: Ni 0.5 Co 0.2 Mn 0.3 (OH)2) was added and dry mixed in a precision mixer, then calcined at 850°C for 10 hours in an air atmosphere and crushed. 0.28 Zr 0.72 O 1.86 was added to the lithium transition metal composite oxide at a ratio of 0.5% by mass, dry mixed in a precision mixer, and then fired at 850°C for 6 hours in an air atmosphere, crushed, and sized to synthesize a lithium transition metal composite oxide containing cations A and B.

[0060] (Example 42) Chemical formula Li 1.00 Ni 0.85 Co 0.15 Al 0.05 Lithium hydroxide adjusted to form O2, transition metal complex compound (chemical formula: Ni 0.85 Co0.15 Al 0.05 (OH)2) as a complex oxide containing cations A and B, 0.33 Zr 0.67 O 1.84 The mixture was added to the lithium transition metal composite oxide at a ratio of 0.5% by mass, dry mixed in a precision mixer, and then fired at 600°C for 5 hours while flowing oxygen gas, and then at 800°C for 20 hours. The mixture was then crushed and sized to synthesize a lithium transition metal composite oxide containing cations A and B.

[0061] (Example 43) Chemical formula Li 1.00 Ni 0.85 Co 0.15 Al 0.05 Lithium hydroxide adjusted to form O2, transition metal complex compound (chemical formula: Ni 0.85 Co 0.15 Al 0.05 The mixture was then dry mixed in a precision mixer, and calcined at 600°C for 5 hours while flowing oxygen gas, and then at 800°C for 15 hours, after which it was crushed. 0.33 Zr 0.67 O 1.84 was added to the lithium transition metal composite oxide at a ratio of 0.5% by mass, dry mixed in a precision mixer, and then fired at 800°C for 5 hours while flowing oxygen gas. The mixture was then crushed and sized to synthesize a lithium transition metal composite oxide containing cations A and B.

[0062] (Example 44) In Example 44, Y 0.33 Zr 0.67 O 1.84 The preparation was carried out in the same manner as in Example 42, except that a composite oxide containing cations A and B, and cation B' in the component ratios shown in Table 4 (ABB'On, where n is a value determined so as to satisfy the charge neutral condition for the valences of cations A, B, and B') was used instead of the above.

[0063] Comparative Example 6 Chemical formula Li 1.00 Ni 0.85 Co 0.15 Al0.05 Lithium hydroxide adjusted to form O2, transition metal complex compound (chemical formula: Ni 0.85 Co 0.15 Al 0.05 The mixture was dry mixed in a precision mixer, then fired at 600°C for 5 hours in an oxygen gas flow, then at 800°C for 20 hours, after which it was crushed and sized to synthesize a lithium transition metal composite oxide.

[0064] Comparative Example 7 In Comparative Example 7, Y 0.33 Zr 0.67 O 1.84 Instead of the above, a composite oxide (ABO) containing cations A and B in the ratios shown in Table 4 was used. n (where n is a value determined so as to satisfy the charge neutral condition for the valences of cations A and B) was used, and the preparation was carried out in the same manner as in Example 42.

[0065] (Comparative Example 8 and Comparative Example 9) In Comparative Examples 8 and 9, a composite oxide containing cations A and B in the component ratios shown in Table 4 (ABOn, where n is a value determined so as to satisfy the charge neutral condition for the valences of cations A and B) was added to the lithium transition metal composite oxide in the mass % ratios shown in Table 7, but the preparation was performed in the same manner as in Example 42.

[0066] (Positive electrode production) A positive electrode was prepared by using the lithium transition metal composite oxides synthesized in the above examples and comparative examples as the positive electrode active material. Timcal's product names KS6 and Super-P were used as the conductive assistant, and Kureha's product name KF polymer (a solution of PVdF dissolved in N-methylpyrrolidone) was used as the binder. The weight ratio of "positive electrode active material: KS6: Super-P: binder" was weighed out in a ratio of "94: 1: 2: 3", and NMP was added and kneaded to prepare a positive electrode slurry. The obtained slurry was applied to an aluminum current collector by the doctor blade method, dried, punched into a disk shape with a diameter of 13 mm, and pressed to prepare a positive electrode.

[0067] (Coin cell assembly) For the positive electrode, negative electrode, electrolyte, and separator in the above-mentioned Examples and Comparative Examples, a disk-shaped piece of metallic lithium was cut out, a 1 mol / l solution of the solute LiPF6 in a solvent of ethylene carbonate and diethyl carbonate mixed in a volume ratio of 3:7, and a microporous membrane made of polypropylene was used, respectively, and a coin-type battery CR2032 type (diameter 20 mm, height 3.2 mm) was assembled to perform battery evaluation measurements.

[0068] (Battery evaluation) The coin-type lithium secondary battery thus fabricated was first subjected to initial activation in a thermostatic chamber at 25°C. Charging was performed at a rate of 35mA / g, with a constant current and voltage upper limit of 4.23V, and charging was terminated when the current reached 2mA / g. Discharging was performed at a rate of 35mA / g, with a lower discharge voltage limit of 3.0V. For initial activation, charging and discharging were repeated three times under these conditions. Next, the coin-type lithium secondary battery after the initial activation was placed in a thermostatic chamber at 45°C, and charging was terminated when the current reached 7mA / g at a rate of 80mA / g and a constant current / voltage upper limit of 4.23V, and discharging was performed at a rate of 80mA / g and a lower discharge voltage limit of 3.0V, and a charge / discharge test was performed 60 times.

[0069] Next, the coin-type lithium secondary battery after the 60-cycle charge-discharge test was subjected to a rate characteristic evaluation in a thermostatic chamber at 25°C. First, charging was performed at a rate of 35 mA / g with a constant current and voltage upper limit of 4.23 V, and charging was terminated when the current reached 2 mA / g. Discharging was performed once at a rate of 35 mA / g with a lower discharge voltage limit of 3.0 V. Subsequently, charging was performed at a rate of 35 mA / g with a constant current and voltage upper limit of 4.23 V, and charging was terminated when the current reached 2 mA / g. Discharging was performed once at a rate of 350 mA / g with a lower discharge voltage limit of 3.0 V.

[0070] In Examples 1 to 41 and Comparative Examples 1 to 5, the rate characteristics (%) were calculated by dividing the discharge capacity of each Example and Comparative Example when the discharge rate was 350 mA / g and the lower limit voltage was 3.0 V under the above conditions by the discharge capacity of Comparative Example 2 when the discharge rate was 350 mA / g and the lower limit voltage was 3.0 V. In other words, rate characteristic (%) = (discharge capacity of each example and comparative example at discharge rate of 350 mA / g and lower discharge voltage limit of 3.0 V) ÷ (discharge capacity of comparative example 2 at discharge rate of 350 mA / g and lower discharge voltage limit of 3.0 V).

[0071] In addition, in Examples 42 to 44 and Comparative Examples 7 to 9, the rate characteristics (%) were calculated by dividing the discharge capacity of each Example and Comparative Example when the discharge rate was 350 mA / g and the lower limit voltage was 3.0 V under the above conditions by the discharge capacity of Comparative Example 7 when the discharge rate was 350 mA / g and the lower limit voltage was 3.0 V. In other words, rate characteristic (%) = (discharge capacity of each Example and Comparative Example when discharge rate is 350 mA / g and lower limit voltage is 3.0 V) ÷ (discharge capacity of Comparative Example 7 when discharge rate is 350 mA / g and lower limit voltage is 3.0 V).

[0072] The addition ratio of cation A (and cation A') to cation B (and cation B') was set to 1 mol in total.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] [Table 4]

[0077] As shown in Tables 1, 2, and 3, the rate characteristics of the positive electrode materials having a layered crystal structure that does not contain either cation A or cation B shown in Comparative Example 1 and the positive electrode material having a layered crystal structure that contains cation A shown in Comparative Example 2 are all improved in the positive electrode materials having a layered crystal structure synthesized by adding cation B in Examples 1 to 41, or a complex oxide containing cation A (and cation A') and cation B (and cation B').

[0078] Similarly, as shown in Table 4, the rate characteristics of the positive electrode material having a layered crystal structure not containing either cation A or cation B shown in Comparative Example 6, and the positive electrode material having a layered crystal structure containing cation A shown in Comparative Example 7 are all improved in the positive electrode materials having a layered crystal structure synthesized by adding cation B in Examples 42 to 44, or a complex oxide containing cation A (and cation A') and cation B (and cation B').

[0079] It was confirmed from Examples 1 to 4 and Comparative Example 3 that there is a preferred blend ratio of cation A and cation B, and if the amount of cation B is too small, the rate characteristics do not improve. From Comparative Examples 4 and 5 for Example 1, or Comparative Examples 8 and 9 for Example 42, it was confirmed that there is a preferred ratio by mass of the composite oxide containing cation A and cation B to the lithium transition metal composite oxide.

Claims

【Request 1】 The additive is used to insert cation A and cation B between layers of a positive electrode material having a layered crystal structure for use in a lithium ion secondary battery, and is a composite oxide containing cation B having an ionic radius larger than that of a lithium ion and a valence of 2 or more, and cation A having an ionic radius smaller than that of a lithium ion and a valence of 2 or more (provided that cation A is Ti 4+ And the cation B is Ba 2+ and cation A is Ti 4+ and cation B is Sr 2+ . 【Request 2】 The cation B is Ca 2+ , Sr 2+ , Ba 2+ , In 3+ , Y 3+ , La 3+ , Ce 3+ , Ce 4+ , P 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , Lu 3+ , Bi 3+ 2. The positive electrode material additive for a lithium ion secondary battery according to claim 1, wherein the additive is one or more selected from the following:

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