JP5181482B2 - Method for producing positive electrode active material for non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, and more specifically, a positive electrode active material for a non-aqueous electrolyte secondary battery that has excellent thermal stability and a high charge / discharge capacity, and its The present invention relates to a manufacturing method suitable for industrial production.

In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density is strongly desired. A lithium ion secondary battery is used as such a secondary battery. By the way, although a lithium ion secondary battery is comprised with a positive electrode and negative electrode material, electrolyte solution, etc., the material which can detach | desorb and insert lithium is used as the active material of the negative electrode and the positive electrode. The positive electrode active material is currently being actively researched and developed.
Among these, a lithium ion secondary battery using a lithium metal composite oxide, particularly a lithium cobalt composite oxide (LiCoO ₂ ) that can be synthesized relatively easily, as a positive electrode active material has a high voltage of 4V. Therefore, practical use is progressing as a battery having a high energy density. In the lithium ion secondary battery using this lithium cobalt composite oxide (LiCoO ₂ ), many developments have been made so far to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained. ing.

  However, since the lithium cobalt composite oxide uses rare and expensive cobalt as a raw material, it has been a cause of cost increase of the battery. For this reason, what is cheaper than a lithium cobalt complex oxide as a positive electrode active material is desired. In addition, recently, as a use of lithium ion secondary batteries, not only small secondary batteries for portable electronic devices but also expectation to be applied as large secondary batteries for power storage, electric vehicles, etc. Yes. Therefore, reducing the cost of the active material and making it possible to manufacture a cheaper lithium ion secondary battery can be expected to have a large ripple effect in these wide fields.

Under such circumstances, a lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese, which is cheaper than cobalt, or a lithium nickel composite oxide (LiNiO ₂ ) using nickel as a positive electrode active material for a lithium ion secondary battery. ) Has been proposed as a new material. Here, the lithium manganese composite oxide is an effective alternative to the lithium cobalt composite oxide because its raw material is inexpensive and has excellent thermal stability, in particular, safety with respect to ignition and the like. However, since its theoretical capacity is only about half that of the lithium cobalt composite oxide, it has a drawback that it is difficult to meet the demand for higher capacity of lithium ion secondary batteries, which is increasing year by year. Further, at a temperature of 45 ° C. or higher, there is a drawback that self-discharge is intense and the charge / discharge life is also reduced.

  On the other hand, the lithium nickel composite oxide has almost the same theoretical capacity as the lithium cobalt composite oxide, and shows a slightly lower battery voltage than the lithium cobalt composite oxide. Therefore, decomposition due to oxidation of the electrolyte is less likely to be a problem. Since high capacity can be expected, development is actively conducted. However, when a lithium-ion secondary battery is produced using a lithium nickel composite oxide composed only of nickel as a positive electrode active material without replacing a part of nickel with another element, a lithium cobalt composite oxide There is a problem that cycle characteristics are inferior to In addition, when used or stored in a high-temperature environment, the battery performance is relatively easily lost.

As this solution, for example, Li _w Ni _x Co _y B _Z O ₂ (wherein w, x, y) can be used as a positive electrode active material capable of maintaining good battery performance during storage and use in a high temperature environment. , Z is 0.05 ≦ w ≦ 1.10, 0.5 ≦ x ≦ 0.995, 0.005 ≦ z ≦ 0.20, and x + y + z = 1.) That is, a lithium nickel composite oxide to which cobalt and boron are added has been proposed (for example, see Patent Document 1).
Further, for the purpose of improving the self-discharge characteristics and cycle characteristics of the lithium ion secondary battery, Li _z Ni _a Co _b M _c O _z (wherein M is Al, V, Mn, Fe, Cu or Zn). X, a, b, c are 0.8 ≦ x ≦ 1.2, 0.01 ≦ a ≦ 0.99, 0.01 ≦ b ≦ 0.99, Lithium-nickel based composite oxide represented by 0.01 ≦ c ≦ 0.3 and 0.8 ≦ a + b + c ≦ 1.2 is proposed (for example, see Patent Document 2).
However, in the lithium nickel composite oxide obtained by the above-described conventional manufacturing method, both the charge capacity and discharge capacity are higher and the cycle characteristics are improved as compared with the lithium cobalt composite oxide. If left in the environment, there is a problem that oxygen is released from a lower temperature than that of the cobalt-based composite oxide.

In order to solve such a problem, for example, for the purpose of improving the thermal stability of the lithium ion secondary battery positive electrode material, Li _{a Mb} Ni _c Co _d O _e (wherein M is Al, It is at least one element selected from Mn, Sn, In, Fe, V, Cu, Mg, Ti, Zn or Ti, and a, b, c, d and e are 0 <a <1.3, 0. 02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, 1.8 <e <2.2, and b + c + d = 1)) (For example, see Patent Document 3). Here, for example, when aluminum is selected as the additive element M, it is confirmed that if the amount of substitution from nickel to aluminum is increased, the decomposition reaction of the positive electrode active material is suppressed and the thermal stability is improved. . However, if nickel is replaced with an effective amount of aluminum to ensure sufficient stability, the amount of nickel that contributes to the oxidation-reduction reaction accompanying the charge / discharge reaction decreases, so the initial capacity, which is the most important for battery performance, is large. It had the problem of being lowered. This is because Al is stable at trivalent, and Ni also stabilizes at trivalent in order to match the charge, so that a portion that does not contribute to the oxidation-reduction reaction (Redox reaction) occurs, resulting in a decrease in capacity. Conceivable.

  By the way, recently, the demand for higher capacity for small secondary batteries such as portable electronic devices is increasing, and sacrificing the capacity to ensure safety is an advantage of the high capacity of lithium nickel composite oxide You will lose. Furthermore, the movement to use lithium ion secondary batteries for large-sized secondary batteries is also prominent, and among them, expectations are high as power sources for hybrid vehicles and electric vehicles. When used as a power source for automobiles, solving the problem of the lithium nickel composite oxide that is inferior in safety is a big problem. Therefore, in a positive electrode active material for a non-aqueous electrolyte secondary battery, it is required to secure charge / discharge capacity and further improve thermal stability.

JP-A-8-45509 (first page, second page) Japanese Patent Laid-Open No. 8-213015 (first page, second page) JP-A-5-242891 (first and second pages)

  In view of the above-mentioned problems of the prior art, an object of the present invention is a production method suitable for industrial production of a positive electrode active material for a non-aqueous electrolyte secondary battery that is excellent in thermal stability and has a high charge / discharge capacity. Is to provide.

  In order to achieve the above object, the present inventors have conducted extensive research on a positive electrode active material for a non-aqueous electrolyte secondary battery, and as a result, have found that a specific general substance containing lithium, nickel, cobalt, and an additive element (M). It is a complex oxide represented by the formula, and as the additive element (M), two or more specific elements are combined so that the average valence becomes a specific value. Improving the thermal stability in the charged state while ensuring, obtaining a positive electrode active material for a non-aqueous electrolyte secondary battery having good thermal stability and high charge / discharge capacity, and It was found that a non-aqueous electrolyte secondary battery with high capacity and high safety can be obtained using Moreover, the process of obtaining the nickel cobalt composite hydroxide which controlled the atomic ratio of nickel and cobalt, the process of obtaining the nickel cobalt addition element (M) composite hydroxide which controlled the atomic ratio of the additive element (M), nickel cobalt addition The positive electrode active material is industrially efficiently produced by a manufacturing method including a step of obtaining an element (M) composite oxide and a step of obtaining a lithium nickel cobalt-added element (M) composite oxide in which the atomic ratio of lithium is controlled. Found to be produced. Thus, the present invention has been completed.

That is, according to the first invention of the present invention, for a non-aqueous electrolyte secondary battery comprising a composite oxide represented by the following general formula (i) containing lithium, nickel, cobalt and an additive element (M) A method for producing a positive electrode active material, wherein the positive electrode active material is a single phase in which an additive element (M) is dissolved , and is produced by the following steps (a) to (d). A method for producing a positive electrode active material for an aqueous electrolyte secondary battery is provided.
_{Li 1 + z Ni 1-x} -y Co x M y O 2 ··· (i)
(Wherein x, y, z satisfy the requirements of 0.10 ≦ x ≦ 0.21, 0.015 ≦ y ≦ 0.08, −0.05 ≦ z ≦ 0.10, and M is oxygen (It is composed of at least two elements selected from aluminum (Al), manganese (Mn), niobium (Nb), and molybdenum (Mo)), which have an affinity for and better than nickel, and the average valence exceeds three.)
Step (a): After adding an alkaline aqueous solution to a mixed aqueous solution of nickel salt and cobalt salt, they are stirred at a constant speed to cause coprecipitation, and the precipitate is collected after reaching a steady state in the reaction vessel. And filtering and washing with water to obtain a nickel-cobalt composite hydroxide having a controlled atomic ratio of nickel and cobalt.
Step (b): The nickel-cobalt composite hydroxide is dispersed in an aqueous solution containing an additive element (M) composed of at least two elements selected from aluminum, manganese, niobium or molybdenum, and the composite hydroxide Or impregnating the surface of the composite hydroxide with the hydroxide of the additive element (M) produced by the neutralization treatment, followed by drying to add atoms of the additive element (M) A nickel cobalt-added element (M) composite hydroxide having a controlled ratio is obtained.
Step (c): The nickel cobalt-added element (M) composite hydroxide is fired at a temperature of 300 to 900 ° C. to obtain a nickel cobalt-added element (M) composite oxide.
Step (d): The nickel-cobalt additive element in which the nickel-cobalt additive element (M) composite oxide and the lithium compound are mixed and the mixture is baked at a temperature of 650 to 850 ° C. to control the atomic ratio of lithium. (M) A composite oxide is obtained.

According to the second invention of the present invention, in the first invention, the nickel-cobalt composite hydroxide obtained in the step (a) is a substantially spherical particle. A method for producing a positive electrode active material is provided.

The present invention is a production method suitable for industrial production of a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a composite oxide powder having excellent thermal stability and high charge / discharge capacity. The non-aqueous electrolyte secondary battery in the invention is a high-capacity and high-safety non-aqueous electrolyte secondary battery using the positive electrode active material for the non-aqueous electrolyte secondary battery obtained by the present invention, so that its industrial The value is extremely great. As a result, it is possible to meet the demand for higher capacity in small secondary batteries such as portable electronic devices, and to ensure the safety required for large secondary batteries that are power sources for hybrid vehicles and electric vehicles. It is more advantageous because it can.

Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, the production method thereof, and the non-aqueous electrolyte secondary battery using the same will be described in detail.
1. Positive electrode active material for non-aqueous electrolyte secondary battery The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is represented by the following general formula (i) containing lithium, nickel, cobalt and an additive element (M). A positive electrode active material for a non-aqueous electrolyte secondary battery comprising a single-phase composite oxide in which an additive element (M) is dissolved, wherein the additive element (M) is produced by the following steps (a) to (d) .
_{Li 1 + z Ni 1-x} -y Co x M y O 2 ··· (i)
(Wherein, x, y, z are, 0.10 ≦ x ≦ 0.21,0.015 ≦ y ≦ 0.08, meets the requirements of -0.05 ≦ z ≦ 0.10, M is It consists of at least two elements selected from aluminum (Al), manganese (Mn), niobium (Nb), and molybdenum (Mo), which have an affinity for oxygen better than nickel, and the average valence exceeds three . )
Step (a): After adding an alkaline aqueous solution to a mixed aqueous solution of nickel salt and cobalt salt, they are stirred at a constant speed to cause coprecipitation, and the precipitate is collected after reaching a steady state in the reaction vessel. And filtering and washing with water to obtain a nickel-cobalt composite hydroxide having a controlled atomic ratio of nickel and cobalt.
Step (b): The nickel-cobalt composite hydroxide is dispersed in an aqueous solution containing an additive element (M) composed of at least two elements selected from aluminum, manganese, niobium or molybdenum, and the composite hydroxide Or impregnating the surface of the composite hydroxide with the hydroxide of the additive element (M) produced by the neutralization treatment, followed by drying to add atoms of the additive element (M) A nickel cobalt-added element (M) composite hydroxide having a controlled ratio is obtained.
Step (c): The nickel cobalt-added element (M) composite hydroxide is fired at a temperature of 300 to 900 ° C. to obtain a nickel cobalt-added element (M) composite oxide.
Step (d): The nickel-cobalt additive element in which the nickel-cobalt additive element (M) composite oxide and the lithium compound are mixed and the mixture is baked at a temperature of 650 to 850 ° C. to control the atomic ratio of lithium. (M) A composite oxide is obtained.

In the positive electrode active material, lithium, nickel, the following general formula containing cobalt and additive element _(M): nonaqueous including a complex oxide represented by _{Li 1 + z Ni 1-x} -y Co x M y O 2 The positive electrode active material for an electrolyte secondary battery, wherein the additive element (M) is composed of two or more elements having an affinity for oxygen superior to nickel, and the average valence of the additive element (M) is: It is important to exceed the trivalence. Here, the average valence (V) of the additive element (M) is represented by the following relational expression.
_{V = (V 1 × Y 1} + V 2 × Y 2 + V 3 × Y 3 + ···) / y
(Where Y ₁ , Y ₂ , Y ₃ ,... Represent the amount of additive elements (M ₁ , M ₂ , M ₃ ,...) V ₁ , V ₂ , V ₃ ,. .. represents the valence of the additive element (M ₁ , M ₂ , M ₃ ,..., Y represents y = Y ₁ + Y ₂ + Y ₃ +...)

This point will be described below in relation to the charge / discharge reaction of the non-aqueous electrolyte secondary battery.
In general, the charge / discharge reaction of a non-aqueous electrolyte secondary battery proceeds by reversibly entering and exiting lithium ions in the positive electrode active material. It is said that the positive electrode active material from which lithium is extracted by charging becomes unstable at high temperatures, so that when heated, the active material decomposes and releases oxygen, which causes combustion of the electrolyte and an exothermic reaction. . Here, if the heat dissipation rate to the outside of the battery is larger than the internal heat generation rate, the temperature of the battery will not rise, but if the reverse, the temperature of the battery will rise and lead to thermal runaway. Therefore, improving the safety of the battery means that, from the standpoint of the positive electrode side, the decomposition reaction of the positive electrode active material from which lithium is extracted is suppressed or the reaction rate is reduced.

By the way, conventionally, as a method of suppressing the decomposition reaction of the positive electrode active material, it has been disclosed and generally carried out that a part of nickel is replaced by an element having strong covalent bond with oxygen such as aluminum. According to this method, if the amount of substitution from nickel to aluminum is increased, the decomposition reaction of the positive electrode active material can surely be suppressed and the thermal stability can be improved, but on the other hand, the redox reaction accompanying the charge / discharge reaction As a result, the amount of nickel that contributes to the decrease is reduced, leading to a decrease in charge / discharge capacity. Therefore, the amount of substitution with aluminum at this time had to be limited to some extent. As a result, such a replacement with aluminum cannot provide a sufficient reversible capacity if sufficient thermal stability is ensured, and at the expense of thermal stability to obtain a certain level of capacity. There was a technical problem that had to be done.
In addition, when an element having an affinity for oxygen other than aluminum that is superior to nickel and having a higher valence is used alone, in general, it has a sufficient effect on thermal stability without causing a heterogeneous phase in the positive electrode material. It is known that it is difficult to substitute and dissolve the amount that can be exhibited.

  On the other hand, in the present invention, the additive element (M) is a combination of two or more elements having an affinity for oxygen superior to nickel so that the average valence exceeds three. Thus, by replacing nickel with two or more elements having higher oxygen affinity than nickel and dissolving them in solid solution, a sufficient effect on thermal stability is exhibited and the average valence of the additive element (M) exceeds 3 valences. By doing so, the average valence of nickel can be made less than 3, and thereby the charge / discharge capacity of the battery can be ensured.

  Such an additive element (M) is not particularly limited, and a combination of elements having a lower base than nickel, that is, an oxygen affinity higher than that of nickel, so that the average valence exceeds three is used. Among these, in particular, aluminum (as an additive element (M) that can be dissolved in an amount capable of exhibiting a sufficient effect on thermal stability without causing a heterogeneous phase in the composite oxide) It is preferable to use at least two elements selected from Al), manganese (Mn), niobium (Nb), and molybdenum (Mo).

  That is, as described above, aluminum has a strong covalent bond and a strong affinity for oxygen, and thus has an effect of reducing oxygen release at a high temperature and suppressing a decomposition reaction of the positive electrode. However, since aluminum is trivalent and extremely stable, it cannot contribute to the oxidation-reduction reaction. As a result, when the added amount is increased, the capacity is significantly reduced, and there is a problem that the added amount is limited. Manganese, niobium or molybdenum is an element useful for improving thermal stability because it has higher oxygen affinity than nickel and higher valence than aluminum, but these elements alone ensure thermal stability. Therefore, there is a problem that a sufficient amount is difficult to be dissolved in the composite oxide without causing a heterogeneous phase. However, if at least two kinds of elements selected from aluminum (Al), manganese (Mn), niobium (Nb) or molybdenum (Mo) are used in combination, the above problems can be solved, and a sufficient effect on thermal stability can be obtained. The amount that can be exhibited can be dissolved in the composite oxide without causing a heterogeneous phase, and a decrease in charge / discharge capacity generally caused by the addition of elements can be suppressed.

  The element having the maximum valence among the additive elements (M) is molybdenum (Mo), and its valence is hexavalent. Therefore, the upper limit of the average valence of the additive element (M) is 6 Less than the value. Further, in order to minimize the decrease in charge / discharge capacity, the average valence of the additive element (M) is increased by suppressing the amount of aluminum substitution and increasing the proportion of manganese, niobium or molybdenum, for example, 3. It is preferable to be pentavalent or higher.

Further, at this time, the general _formula: is wherein the _{Li 1 + z Ni 1-x} -y Co x M y O 2, x, y, z is determined to satisfy the following requirements (1) to (3) .
Requirement (1) is 0.10 ≦ x ≦ 0.21 as the Co substitution amount x. That is, a pure lithium nickel composite oxide (LiNiO ₂ ) that does not perform element substitution has a disadvantage that it is inferior in cycle characteristics, but in order to solve this, it is useful to substitute a part of Ni with Co. It is known that there is. Here, in particular, sufficient cycle characteristics can be obtained by setting the value of x to 0.10 or more. On the other hand, if the amount of substitution of Co is increased, the initial capacity is significantly lowered, and the high capacity, which is the greatest merit of the positive electrode active material made of nickel-based composite oxide, is sacrificed. .21.

The requirement (2) is that the substitution amount y of the additive element (M) is 0.015 ≦ y ≦ 0.08. That is, if the value of y is less than 0.015, a sufficient thermal stability effect cannot be obtained. On the other hand, if the value of y exceeds 0.08, it is difficult to form a solid solution without causing a heterogeneous phase. The average valence of nickel will be significantly smaller than the trivalence. Incidentally, when the average valence of nickel is considerably smaller than trivalent, - by a redox reaction of [bivalent tetravalent], since the charge and discharge potential rises undesirably.

  In requirement (3), the amount of lithium z is −0.05 ≦ z ≦ 0.10. That is, if the value of z is less than −0.05, the charge / discharge capacity decreases, while if it exceeds 0.10, the thermal stability decreases.

  The particle size distribution of the positive electrode active material is not particularly limited, but preferably, D50 is 8 to 11 μm and the tap density is 2.2 to 2.8 g / mL. Thereby, when producing a positive electrode, excellent filling properties of the positive electrode active material can be obtained.

  When the positive electrode active material is used for the positive electrode, the initial discharge capacity of the battery is 170 mAh / g or more, preferably 185 mAh / g or more. Furthermore, the heating rate by a differential scanning calorimeter (DSC) when heated after charging is 26 W / g or less. Thereby, there is no practical problem in safety as a battery.

2. Method for producing positive electrode active material for non-aqueous electrolyte secondary battery The method for producing the positive electrode active material for non-aqueous electrolyte secondary battery of the present invention is not particularly limited. A method characterized by including (d) is used.
Step (a): After adding an alkaline aqueous solution to a mixed aqueous solution of nickel salt and cobalt salt, they are stirred at a constant speed to cause coprecipitation, and the precipitate is collected after reaching a steady state in the reaction vessel. And filtering and washing with water to obtain a nickel-cobalt composite hydroxide having a controlled atomic ratio of nickel and cobalt.
Step (b): The nickel-cobalt composite hydroxide is dispersed in an aqueous solution containing an additive element (M) composed of at least two elements selected from aluminum, manganese, niobium or molybdenum, and the composite hydroxide Or impregnating the surface of the composite hydroxide with the hydroxide of the additive element (M) produced by the neutralization treatment, followed by drying to add atoms of the additive element (M) A nickel cobalt-added element (M) composite hydroxide having a controlled ratio is obtained.
Step (c): The nickel cobalt-added element (M) composite hydroxide is fired at a temperature of 300 to 900 ° C. to obtain a nickel cobalt-added element (M) composite oxide.
Step (d): The nickel-cobalt additive element in which the nickel-cobalt additive element (M) composite oxide and the lithium compound are mixed and the mixture is baked at a temperature of 650 to 850 ° C. to control the atomic ratio of lithium. (M) A composite oxide is obtained.

(1) Process (I)
In the above step (a), an alkaline aqueous solution is added to a mixed aqueous solution of nickel salt and cobalt salt, and then they are stirred at a constant speed to cause coprecipitation, and the precipitate is obtained after reaching a steady state in the reaction vessel. Is collected, filtered and washed with water to obtain a nickel-cobalt composite hydroxide (NiCo (OH) ₂ ) in which the atomic ratio of nickel and cobalt is controlled. Here, the atomic ratio of nickel and cobalt is controlled, for example, by adjusting the atomic ratio of nickel and cobalt contained in the mixed solution so as to be a predetermined value satisfying the general formula representing the positive electrode active material. Is done. At this time, in order to obtain substantially spherical particles, it is preferable to maintain the pH in the range of 10 to 12.5 and the reaction temperature in the range of 50 to 80 ° C.

  The mixed aqueous solution of nickel salt and cobalt salt used in the step (a) is not particularly limited, and a solution obtained by dissolving a water-soluble salt such as sulfate, chloride, nitrate, etc. in a desired composition is used. Further, the concentration of the aqueous solution is not particularly limited, and a saturated concentration is preferable for the purpose of reducing the amount of the solution, but a concentration at which crystals do not precipitate even when left at room temperature is preferable. For example, the total of nickel and cobalt is preferably 1 to 2 mol / liter, and more preferably 1.5 to 2 mol / liter.

  As a blending ratio of the nickel salt and the cobalt salt, the molar amount of cobalt with respect to the total amount of nickel, cobalt, and additive element (M) in the composite oxide containing lithium, nickel, cobalt, and additive element (M) is obtained. It adjusts so that it may contain in the range of 0.10-0.21 by ratio. This means that x in the above general formula is performed so as to satisfy the range of 0.10 ≦ x ≦ 0.21. Thereby, the atomic ratio of nickel and cobalt can be controlled.

  The aqueous alkali solution used in the above step (ii) is not particularly limited, and a solution in which an alkali metal hydroxide such as sodium hydroxide is dissolved is used. The concentration of the alkaline aqueous solution is not particularly limited, and is preferably 12% by weight or more and not more than a saturated concentration for the purpose of suppressing the liquid amount.

  In the step (a), a complexing agent can be added as necessary. As the complexing agent, a drug having an action of increasing the solubility of nickel and cobalt is used. Among them, ammonium chloride, ammonium carbonate, ammonium fluoride and the like can be mentioned in addition to ammonia and ammonium sulfate. A supply is preferred.

(2) Process (b)
In the step (b), the nickel-cobalt composite hydroxide is dispersed in an aqueous solution containing an additive element (M) composed of at least two elements selected from aluminum, manganese, niobium or molybdenum, and the composite hydroxide After impregnating the compound in the product or adhering the hydroxide of the additive element (M) produced by the neutralization treatment to the surface of the composite hydroxide, drying is performed, and then the additive element (M) is dried. This is a step of obtaining a nickel cobalt additive element (M) composite hydroxide (NiCoM (OH) ₂ ) in which the atomic ratio is controlled. Here, the control of the atomic ratio of the additive element (M) is, for example, the additive element contained in the aqueous solution containing the additive element (M) so as to have a predetermined value that satisfies the general formula representing the positive electrode active material. This is done by adjusting the blending ratio of (M) with respect to the total amount of nickel and cobalt. Moreover, this process can be performed several times using the aqueous solution containing each of the additive element (M).

  The aqueous solution containing the additive element (M) composed of at least two elements selected from aluminum, manganese, niobium or molybdenum used in the above step (b) is not particularly limited, and aluminum, manganese, niobium or molybdenum. An alkaline or acidic aqueous solution in which a compound of an additive element (M) consisting of at least two elements selected from is dissolved is used. Among them, for example, aluminum is sodium aluminate, aluminum sulfate, etc. Examples of manganese sulfate include niobium pentoxide, sodium niobate, and the like, and molybdenum includes aqueous solutions of sodium molybdate, ammonium molybdate, and the like.

  As a blending ratio of the additive element (M), the additive element (M) is added to the total amount of nickel, cobalt, and additive element (M) in the composite oxide containing lithium, nickel, cobalt, and the additive element (M). M) is adjusted so as to be contained in the range of 0.015 to 0.08 by atomic ratio. This is performed so that y in the general formula of the positive electrode active material satisfies the range of 0.015 ≦ y ≦ 0.08.

(3) Process (C)
The said process (C) is a process of baking the said nickel cobalt addition element (M) composite hydroxide at the temperature of 300-900 degreeC, and obtaining a nickel cobalt addition element (M) composite oxide (NiCoMO). Thereby, a substantially spherical composite oxide powder is obtained.

  The firing temperature used in the step (c) is 300 to 900 ° C., and the firing time is not particularly limited, but is preferably about 10 to 20 hours. Further, the atmosphere during firing is not particularly limited, but is performed in an oxygen atmosphere such as an air stream or an oxygen stream. That is, if the firing temperature is less than 300 ° C., decomposition of the hydroxide is insufficient, while if it exceeds 900 ° C., particle growth occurs, which is not preferable.

(4) Process (d)
In the step (d), the nickel-cobalt additive element (M) composite oxide and a lithium compound are mixed, and the mixture is baked at a temperature of 650 to 850 ° C. to control the lithium atomic ratio. In this step, an additive element (M) composite oxide (LiNiCoMO ₂ ) is obtained. Here, the control of the atomic ratio of lithium is performed by, for example, changing the mixing ratio of lithium contained in the lithium compound to nickel, cobalt, and an additive element (so that the general formula representing the positive electrode active material is satisfied). By adjusting to the total amount of M). Thereby, a substantially spherical composite oxide powder is obtained.

  The lithium compound used in the step (d) is not particularly limited, and is at least one selected from the group consisting of lithium hydroxide, oxyhydroxide, oxide, carbonate, nitrate and halide. Of these, lithium carbonate, lithium hydroxide, or a hydrate thereof is preferable.

  As a blending ratio of the lithium compound, lithium is 0 in atomic ratio with respect to the total amount of nickel, cobalt, and additive element (M) in the composite oxide containing lithium, nickel, cobalt, and additive element (M). .95 to 1.10. This is performed so that z in the composition formula (1) satisfies the range of −0.05 ≦ z ≦ 0.10.

The firing temperature used in the step (d) is 650 to 850 ° C., and the firing time is not particularly limited, but is preferably about 10 to 20 hours. In addition, the firing atmosphere is not particularly limited, but is performed in an oxidizing atmosphere such as an air stream or an oxygen stream.
That is, when the firing temperature is less than 650 ° C., the reaction with the lithium compound does not proceed sufficiently, and it becomes difficult to synthesize a lithium nickel composite oxide having a desired layered structure. On the other hand, when the temperature exceeds 850 ° C., Ni is mixed into the Li layer, Li is mixed into the Ni layer, the layered structure is disturbed, and the site occupancy of metal ions other than lithium at the 3a site increases, which is a lithium site. The mixing rate of metal ions at the 3a site is increased, the lithium ion diffusion path is obstructed, and the battery using the positive electrode has a reduced initial capacity and output.

As another method for producing a positive electrode active material of the present invention, an alkaline aqueous solution is added to a mixed aqueous solution of a nickel salt, a cobalt salt and a salt of an additive element (M) instead of the above steps (b) and (b). A step of obtaining a nickel cobalt additive element (M) composite hydroxide at a time can be performed.
Also, instead of the above steps (a), (b) and (c), a nickel compound, a cobalt compound, and an additive element (M) compound are simply mixed and baked to obtain a nickel cobalt additive element (M) composite oxidation. Even in the method of performing the step of obtaining an object, it can be used without any problem as long as a state in which all of these metal elements are in solid solution with each other can be realized.
Furthermore, even before mixing with the lithium compound, even if these metal elements are not completely dissolved, it is possible to realize a state in which all the metal elements are dissolved after mixing with the lithium compound and firing. Any method can be used if possible. For example, when the final lithium metal composite oxide is used, if the metal elements are in solid solution with each other, the step (c) of firing the composite hydroxide to form the composite oxide is omitted. Can do.
Here, as the nickel compound and cobalt compound, oxides, carbonates, nitrates, hydroxides, oxyhydroxides, and the like are used. As the additive element (M) compound, an oxide, a carbonate, an ammonium salt, or the like is used.

3. Non-aqueous electrolyte secondary battery in the non-aqueous electrolyte secondary battery The present invention high safety in high capacity obtained by using the positive electrode active material for a nonaqueous electrolyte secondary battery obtained by the above production method as a positive electrode.
Here, the configuration of the lithium ion secondary battery will be described in detail for each component. The lithium ion secondary battery according to the present invention is composed of the same components as those of a general lithium ion secondary battery, such as a positive electrode, a negative electrode, and a non-aqueous electrolyte. The forms described below are merely examples, and the nonaqueous electrolyte secondary battery according to the present invention should be implemented in variously modified and improved forms based on the knowledge of those skilled in the art, including the following forms. Can do. Moreover, the use of the nonaqueous electrolyte secondary battery in the present invention is not particularly limited.

As the positive electrode active material, as described above, the lithium, nickel, the formula contains cobalt and additive element _{(M): Li 1 + z} Ni 1-x-y Co x M y O 2 ( wherein, x, y , Z is 0.10 ≦ x ≦ 0.21, 0.015 ≦ y ≦ 0.08, −0.05 ≦ z ≦ 0.10, and M is aluminum, manganese, niobium or molybdenum. Consisting of at least two selected elements).

The positive electrode is not particularly limited and can be produced, for example, as follows. The powdered positive electrode active material, conductive material, binder, and binder are mixed, and if necessary, the target solvent such as activated carbon and viscosity adjustment is added and kneaded to prepare the positive electrode mixture paste. Make it. The respective mixing ratios in the positive electrode mixture are also important factors that determine the performance of the lithium secondary battery. For example, when the total mass of the solid content of the positive electrode mixture excluding the solvent is 100% by mass, the content of the positive electrode active material is 60 to 95% by mass, as in the case of the positive electrode of a general lithium secondary battery. It is desirable that the content of the material is 1 to 20% by mass and the content of the binder is 1 to 20% by mass.
The obtained positive electrode mixture paste is applied to the surface of a current collector made of, for example, aluminum foil, and dried to scatter the solvent. Moreover, it may pressurize with a roll press etc. to raise an electrode density as needed. In this way, a sheet-like positive electrode can be produced. The obtained sheet-like positive electrode can be cut into an appropriate size according to the intended battery and used for battery production.

As the conductive agent, for example, carbon black materials such as graphite (natural graphite, artificial graphite, expanded graphite, etc.), acetylene black, ketjen black and the like can be used. Examples of the binder that can be used include polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluororubber, styrene butadiene, cellulose resin, and polyacrylic acid. Moreover, as the binder, it plays a role of keeping the active material particles together, and for example, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene is used. be able to.
Furthermore, if necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as this solvent. Moreover, activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

Next, components other than the positive electrode used in the nonaqueous electrolyte secondary battery of the present invention will be described.
However, the nonaqueous electrolyte secondary battery of the present invention is characterized in that the positive electrode active material is used, and other components are not particularly limited.
Examples of the negative electrode include metallic lithium, lithium alloys, and the like, and a negative electrode mixture in which a binder is mixed with a negative electrode active material capable of inserting and extracting lithium ions, and an appropriate solvent is added to form a paste. It is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.
As the negative electrode active material, for example, a fired organic compound such as natural graphite, artificial graphite, or a phenol resin, or a powdery carbon material such as coke can be used. In this case, as the negative electrode binder, a fluorine-containing resin such as polyvinylidene fluoride can be used as in the case of the positive electrode, and the active material and the solvent for dispersing the binder include N-methyl-2-pyrrolidone. Organic solvents can be used.

  The separator is disposed between the positive electrode and the negative electrode. This separator separates a positive electrode and a negative electrode and retains an electrolyte. For example, a thin film of polyethylene, polypropylene or the like and a film having many minute holes can be used.

The non-aqueous electrolyte solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, tetrahydrofuran, and 2-methyl. At least one selected from ether compounds such as tetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, or phosphorus compounds such as triethyl phosphate and trioctyl phosphate can be used. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

  The shape of the lithium secondary battery according to the present invention composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte can be various, such as a cylindrical type and a laminated type. In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and this electrode body is impregnated with the non-aqueous electrolyte. The positive electrode current collector and the positive electrode terminal that communicates with the outside, and the negative electrode current collector and the negative electrode terminal that communicates with the outside are connected using a current collecting lead or the like. The battery having the above structure can be sealed in a battery case to complete the battery.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the composition used in the examples and comparative examples, the average valence of the additive element (M), the crystal structure, the particle size distribution, the powder packing density, the charge / discharge capacity, and the safety evaluation method of the positive electrode are as follows. is there.

(1) Composition analysis: The analysis was performed using an ICP emission spectrometer (Plasma Spectrometer SPS3000 manufactured by Seiko Instruments Inc).
(2) Evaluation of the average valence of the additive element (M) of the positive electrode active material: It was determined by the relational expression of the average valence (V) of the additive element (M) described above.
(3) Analysis of the crystal structure of the positive electrode active material: The positive electrode active material was analyzed with an X-ray diffractometer (manufactured by Rigaku Electric Co., Ltd .: RINT-1400).
(4) Measurement of the particle size distribution of the positive electrode active material: D50 (particle size at a cumulative distribution rate of 50% by mass) was determined from the particle size distribution measured with a laser scattering particle size measuring device (Microtrack HRA manufactured by Nikkiso).
(5) Measurement of powder packing density (tap density) of positive electrode active material: 12 g of powder is put into a 20 ml glass graduated cylinder and tapped 500 times with a shaking specific gravity measuring instrument (KRS-409, Kuramochi Scientific Instruments). After that, the powder packing density was determined.

(6) Evaluation of charge / discharge capacity of positive electrode active material: 70 parts by mass of active material powder was mixed with 20 parts by mass of acetylene black and 10 parts by mass of PTFE. Lithium metal was used as the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (made by Toyama Pharmaceutical Co., Ltd.) using 1M LiClO ₄ as a supporting salt was used as the electrolyte. A 2032 type coin battery was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C. FIG. 1 shows a schematic structure of a 2032 type coin battery. Here, the coin battery is composed of a positive electrode (evaluation electrode) 3 in a positive electrode can 6, a lithium metal negative electrode 1 in a negative electrode can 5, an electrolyte-impregnated separator 2, a gasket 4, and a current collector 7.
The prepared battery is left for about 24 hours, and after the open circuit voltage OCV (open circuit voltage) is stabilized, the current density with respect to the positive electrode is set to 0.5 mA / cm ² and charged to a cutoff voltage of 4.3 V to obtain an initial charge capacity. The capacity when the battery was discharged to a cutoff voltage of 3.0 V after a one hour rest was defined as the initial discharge capacity. A multi-channel voltage / current generator (R6741A) manufactured by ADVANTEST was used for measuring the charge / discharge capacity.

(7) Safety evaluation of positive electrode: CCCV charge of 2032 type coin battery manufactured by the same method as described above up to a cut-off voltage of 4.5V (constant current-constant voltage charge. First, charge is operated at a constant current. Then, a charging method using a two-phase charging process of terminating charging at a constant voltage.), And then disassembling with care not to short-circuit, and taking out the positive electrode. 3.0 mg of this electrode was measured, 1.3 mg of the electrolyte was added, sealed in an aluminum measurement container, and heated at a rate of temperature increase of 10 ° C./min using a differential scanning calorimeter (PTC-10A, manufactured by Rigaku). The heat generation behavior was measured from room temperature to 400 ° C., and the heat generation rate was determined.

Example 1
(1) Preparation of nickel-cobalt composite hydroxide Nickel sulfate (made by Wako Pure Chemical Industries, reagent grade) and cobalt sulfate (made by Wako Pure Chemical Industries) so that the mixing ratio of nickel and cobalt is 85:15 in atomic ratio. , Reagent special grade) was added, and a 2 mol / L mixed aqueous solution with a total concentration of nickel and cobalt was prepared in the reaction vessel. Next, in the reaction tank, together with the mixed solution, a sodium hydroxide aqueous solution having a concentration of 25% by weight prepared using sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd., reagent grade) and a 25% by weight aqueous ammonia solution as a complexing agent are used. (Wako Pure Chemical Industries, reagent special grade) was added simultaneously. At this time, the pH was maintained in the range of 10 to 12.5, and the reaction temperature was maintained in the range of 50 to 80 ° C. Then, after the inside of the reaction vessel was in a steady state, the overflowed precipitate was collected, filtered, washed with water and dried to obtain spherical particles of nickel cobalt composite hydroxide.

(2) Synthesis of nickel cobalt-added element (M) composite hydroxide Next, as an aqueous solution of niobium salt, an aqueous solution of niobium in which niobium pentachloride is dissolved in an aqueous potassium hydroxide solution having a concentration of 150 g / L, and an aqueous mixed solution of manganese and aluminum A mixed aqueous solution of manganese sulfate and aluminum sulfate was prepared.
First, a nickel cobalt composite hydroxide was slurried with a niobium aqueous solution at a normal temperature at a concentration of 1500 g / L, and then a predetermined amount of a mixed aqueous solution of manganese and aluminum was added thereto and stirred uniformly. It adjusted so that pH might be set to 8-10 using the sulfuric acid of weight%. Thereafter, the entire amount of the hydroxide slurry in the reaction vessel was recovered, filtered, washed with water and dried to obtain a dry powder of nickel cobalt additive element (M) composite hydroxide. In addition, niobium (Nb), manganese (Mn), and aluminum (Al) are each 0.00% with respect to the total amount of nickel, cobalt, and additive metal (M) contained in the nickel cobalt additive element (M) composite hydroxide. Each aqueous solution was prepared so that it might become 5, 0.5, and 1 at%.

(3) Preparation of nickel-cobalt additive element (M) composite oxide Subsequently, 30 g of the obtained composite hydroxide was inserted into a 5 cm × 12 cm × 3 cm magnesia firing container, and a sealed electric furnace was used. After heating up to 700 ° C. at a rate of temperature increase of 5 ° C./min in an air stream with a flow rate of 3 L / min, firing at that temperature for 10 hours, cooling to room temperature in the furnace and adding nickel cobalt additive element (M) A spherical particle was obtained.

(4) Synthesis of positive electrode active material The obtained composite oxide and commercially available lithium hydroxide (manufactured by FMC Co., Ltd.), the atomic ratio of lithium to the total amount of nickel, cobalt and additive element (M) in the composite oxide After weighing to 1: 1.05, the mixture was sufficiently mixed using a shaker mixer device (TURBULA Type T2C manufactured by WAB) with such a strength that the shape of spherical secondary particles was maintained. 20 g of this mixture was inserted into a 5 cm × 12 cm × 3 cm magnesia firing vessel, and heated to 450 ° C. at a heating rate of 5 ° C./min in an oxygen stream at a flow rate of 3 L / min using a sealed electric furnace. And calcined for 2 hours. Next, after heating up to 730 ° C. at a temperature rising rate of 0.47 ° C./min, firing at that temperature for 10 hours, cooling to room temperature in the furnace and firing of the lithium nickel cobalt additive element (M) composite oxide A positive electrode active material made of powder was obtained.

(5) Evaluation of positive electrode active material and positive electrode Composition of the obtained positive electrode active material, average valence of additive element (M), D50 of particle size distribution, powder packing density (tap density), charge / discharge capacity, and positive electrode Safety was evaluated by the above evaluation method. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Example 2)
Nickel in which niobium (Nb), manganese (Mn), and aluminum (Al) are contained in the nickel cobalt additive element (M) composite hydroxide in the above [synthesis of nickel cobalt additive element (M) composite hydroxide] In each of the aqueous solutions prepared so as to be 0.5, 0.5, and 2 at% with respect to the total amount of cobalt and the additive metal (M), and in the above [Synthesis of positive electrode active material], the temperature rising rate was 5 The positive electrode active material was obtained in the same manner as in Example 1 except that the temperature was raised to 730 ° C. at a rate of ℃ / min and baked at that temperature for 5 hours. ), The D50 of the particle size distribution, the powder packing density (tap density), the charge / discharge capacity, and the safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Example 3)
Nickel in which niobium (Nb), manganese (Mn), and aluminum (Al) are contained in the nickel cobalt additive element (M) composite hydroxide in the above [synthesis of nickel cobalt additive element (M) composite hydroxide] In the above [Synthesis of positive electrode active material], each aqueous solution was prepared so as to be 0.5, 0.5, and 3 at%, respectively, with respect to the total amount of cobalt and additive metal (M), and the rate of temperature increase was 5 The positive electrode active material was obtained in the same manner as in Example 1 except that the temperature was raised to 730 ° C. at a rate of ℃ / min and baked at that temperature for 5 hours. ), The D50 of the particle size distribution, the powder packing density (tap density), the charge / discharge capacity, and the safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

Example 4
Using the positive electrode active material obtained in the same manner as in Example 1, first, manganese (Mn) was further added to the total amount of nickel, cobalt, and additive metal (M) contained in the positive electrode active material to a value of 0. The positive electrode active material was slurried at a concentration of 5000 g / L in an aqueous manganese nitrate solution so as to increase by 5 at%, and then vacuum dried at 250 ° C. for 10 hours to obtain a dry powder.
Next, using the obtained dry powder, in [Synthesis of positive electrode active material], the temperature was raised to 500 ° C. at a temperature rising rate of 5 ° C./min in an oxygen stream having a flow rate of 3 L / min, and the temperature was maintained for 5 hours. A positive electrode active material was obtained in the same manner except that it was fired. The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Example 5)
First, the nickel-cobalt composite hydroxide obtained in the same manner as in Example 1 was made of aluminum with respect to the total amount of nickel, cobalt, and additive metal (M) contained in the nickel-cobalt additive element (M) composite hydroxide. After slurrying in a sodium aluminate aqueous solution containing aluminum (Al) so that (Al) is 3.5 at% at a concentration of 500 g / L at room temperature, the concentration is 47 wt% while stirring uniformly. The pH was adjusted to 8 to 10 using sulfuric acid. Thereafter, the entire amount of hydroxide slurry in the reaction vessel was recovered, filtered, washed with water and dried to obtain a dry powder. Next, the obtained dry powder composed of nickel cobalt aluminum composite hydroxide was fired under the same conditions as in [Preparation of nickel cobalt-added element (M) composite oxide] to obtain an intermediate fired product.
Further, using the obtained intermediate fired product, first, manganese (Mn) is 0.5 at% with respect to the total amount of nickel, cobalt, and additive metal (M) contained in the positive electrode active material. After slurrying in an aqueous manganese nitrate solution containing Mn) at a concentration of 5000 g / L, it was vacuum dried at 250 ° C. for 10 hours to obtain a dry powder. Next, using the obtained dry powder, in [Synthesis of positive electrode active material], the temperature was increased to 750 ° C. at a temperature increase rate of 5 ° C./min in an oxygen stream at a flow rate of 3 L / min. A positive electrode active material was obtained in the same manner except that it was fired for a period of time.
The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Example 6)
Example except that manganese nitrate aqueous solution containing manganese (Mn) was used so that manganese (Mn) was 1 at% with respect to the total amount of nickel, cobalt and additive metal (M) contained in the positive electrode active material. 5, the positive electrode active material was obtained, the composition of the obtained positive electrode active material, the average valence of the additive element (M), the particle size distribution D50, the powder packing density (tap density), the charge / discharge capacity, And the safety | security of the positive electrode was evaluated by the said evaluation method. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Example 7)
First, the nickel-cobalt composite hydroxide obtained in the same manner as in Example 1 was made of aluminum with respect to the total amount of nickel, cobalt, and additive metal (M) contained in the nickel-cobalt additive element (M) composite hydroxide. (Al), Molybdenum (Mo), respectively, in a mixed aqueous solution of sodium aluminate and sodium molybdate and pure water containing aluminum (Al) and molybdenum (Mo) and pure water so as to be 2 and 1.5 at%, respectively. Then, the slurry was slurried at a concentration of 500 g / L, and adjusted to a pH of 8 to 10 using sulfuric acid having a concentration of 47% by weight with uniform stirring. Thereafter, the entire amount of hydroxide slurry in the reaction vessel was recovered, filtered, washed with water and dried to obtain a dry powder.
Next, the obtained dry powder composed of nickel cobalt aluminum molybdenum composite hydroxide was fired under the same conditions as in [Synthesis of positive electrode active material] to obtain a positive electrode active material. The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Example 8)
Using the intermediate fired product obtained in the same manner as in Example 5, first, molybdenum (Mo) was 0.5 at% with respect to the total amount of nickel, cobalt, and additive metal (M) contained in the positive electrode active material. After being slurried in an aqueous ammonium molybdate solution containing molybdenum (Mo) at a concentration of 5000 g / L, it was vacuum dried at 250 ° C. for 10 hours to obtain a dry powder. Next, using the obtained dry powder composed of nickel cobalt aluminum molybdenum composite hydroxide, in the above [Synthesis of positive electrode active material], 750 at a temperature rising rate of 5 ° C./min in an oxygen stream of 3 L / min. A positive electrode active material was obtained in the same manner except that the temperature was raised to 0 ° C. and baked at that temperature for 5 hours.
The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

Example 9
Using the nickel-cobalt composite hydroxide obtained in the same manner as in Example 1, first, molybdenum (Mo) was 1 at% relative to the total amount of nickel, cobalt, and additive metal (M) contained in the positive electrode active material. After being slurried in an ammonium molybdate containing molybdenum (Mo) so as to have a concentration of 5000 g / L, the slurry was vacuum dried at 250 ° C. for 10 hours to obtain a dry powder.
Furthermore, the obtained dry powder contains manganese (Mn) so that manganese (Mn) is 0.5 at% with respect to the total amount of nickel, cobalt, and additive metal (M) contained in the positive electrode active material. After slurrying in an aqueous manganese nitrate solution at a concentration of 5000 g / L, it was vacuum dried at 250 ° C. for 10 hours to obtain a dry powder.
Thereafter, using the obtained dry powder composed of nickel cobalt molybdenum manganese composite hydroxide, in the above [Synthesis of positive electrode active material], 750 ° C. at a temperature rising rate of 5 ° C./min in an oxygen stream with a flow rate of 3 L / min. The positive electrode active material was obtained in the same manner except that the temperature was raised to 5 ° C. and baked at that temperature for 5 hours.
The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Comparative Example 1)
In the above [Synthesis of nickel-cobalt additive element (M) composite hydroxide], the total amount of nickel, cobalt, and additive metal (M) contained in the nickel-cobalt additive element (M) composite hydroxide is aluminum (Al ) Is 3.0 at%, a sodium aluminate aqueous solution containing aluminum (Al) is used, and in the above [Synthesis of positive electrode active material], the temperature rising rate is 5 in an oxygen stream at a flow rate of 3 L / min. A positive electrode active material was obtained in the same manner as in Example 1 except that the temperature was raised to 750 ° C. at a temperature of 750 ° C./min and baked at that temperature for 5 hours. The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Comparative Example 2)
Comparative Example, except that aluminum (Al) is 7.0 at% based on the total amount of nickel, cobalt, and additive metal (M) contained in the nickel cobalt additive element (M) composite hydroxide. 1 was performed, and a positive electrode active material was obtained. The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

(Comparative Example 3)
Comparative Example, except that aluminum (Al) is 10.0 at% based on the total amount of nickel, cobalt, and additive metal (M) contained in the nickel cobalt additive element (M) composite hydroxide 1 was performed, and a positive electrode active material was obtained. The composition of the positive electrode active material obtained, the average valence of the additive element (M), D50 of the particle size distribution, powder packing density (tap density), charge / discharge capacity, and safety of the positive electrode were evaluated by the above evaluation methods. The results are shown in Table 1. The crystal structure was a complex oxide single phase having a hexagonal layered structure.

From Table 1, in Examples 1-9, at least 2 sorts of elements chosen from aluminum, manganese, niobium, or molybdenum were used as an addition element (M), and the composition of the obtained positive electrode active material, and also an addition element (M ) For the non-aqueous electrolyte secondary battery comprising the lithium nickel cobalt-added element (M) composite oxide powder that is excellent in thermal stability and has high charge / discharge capacity. It can be seen that a positive electrode active material and a high-capacity non-aqueous electrolyte secondary battery using the positive electrode active material can be obtained. That is, the initial discharge capacity exceeds 170 mAh / g, and the heat generation rate by DSC measurement is 26 W / g or less, which indicates that the battery is an excellent material as a new battery material replacing lithium cobalt composite oxide.
On the other hand, in Comparative Examples 1 to 3, since the additive element (M) does not meet these conditions, it can be seen that satisfactory results cannot be obtained in either thermal stability or initial discharge capacity.

  These relationships will be described with reference to the drawings. FIG. 2 shows the relationship between the initial discharge capacity and the heat generation rate of the positive electrode active materials obtained in Examples and Comparative Examples. As is clear from FIG. 2, the lithium metal composite oxide of the present invention (Example) has a lower heat generation rate and higher safety than the conventional product (Comparative Example) even with the same discharge capacity. I understand that.

As is clear from the above, the positive electrode active material for a nonaqueous electrolyte secondary battery obtained by the production method of the present invention is excellent in thermal stability and has a high charge / discharge capacity, and a positive electrode for a nonaqueous electrolyte secondary battery. A non-aqueous electrolyte secondary battery that is an active material and uses it is a high-capacity, high-safety non-aqueous electrolyte secondary battery, and thus has a high charge / discharge capacity while being excellent in safety. In order to make use of the merit, it is suitable for use as a power source for small portable electronic devices that always require high capacity.
Moreover, in the power supply for electric vehicles, it is indispensable to install an expensive protection circuit for ensuring higher safety in addition to ensuring safety by increasing the size of the battery. However, the non-aqueous electrolyte secondary battery obtained by the manufacturing method of the present invention has excellent safety, so that not only is it easy to ensure safety, but also an expensive protection circuit is simplified, and the Since it can be made into cost, it is suitable as a power supply for electric vehicles. The electric vehicle power source includes not only an electric vehicle driven purely by electric energy but also a so-called hybrid vehicle power source used in combination with a combustion engine such as a gasoline engine or a diesel engine.

It is the schematic of the cross section of the coin battery used for battery evaluation. It is a figure showing the relationship between the initial stage discharge capacity and the heat generation rate which the positive electrode active material obtained by the Example and the comparative example has.

Explanation of symbols

1 Lithium metal negative electrode 2 Separator (electrolyte impregnation)
3 Positive electrode (Evaluation electrode)
4 Gasket 5 Negative electrode can 6 Positive electrode can 7 Current collector

Claims (2)

Lithium, nickel, a process for the preparation of cobalt and a positive electrode active material for a non-aqueous electrolyte secondary battery comprising a composite oxide represented by the following general formula containing an additive element (M) (i), positive electrode active The substance is a single phase in which the additive element (M) is dissolved , and is produced by the following steps (a) to (d). A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.
_{Li 1 + z Ni 1-x} -y Co x M y O 2 ··· (i)
(Wherein x, y, z satisfy the requirements of 0.10 ≦ x ≦ 0.21, 0.015 ≦ y ≦ 0.08, −0.05 ≦ z ≦ 0.10, and M is oxygen (It is composed of at least two elements selected from aluminum (Al), manganese (Mn), niobium (Nb), and molybdenum (Mo)), which have an affinity for and better than nickel, and the average valence exceeds three.)
Step (a): After adding an alkaline aqueous solution to a mixed aqueous solution of nickel salt and cobalt salt, they are stirred at a constant speed to cause coprecipitation, and the precipitate is collected after reaching a steady state in the reaction vessel. And filtering and washing with water to obtain a nickel-cobalt composite hydroxide having a controlled atomic ratio of nickel and cobalt.
Step (b): The nickel-cobalt composite hydroxide is dispersed in an aqueous solution containing an additive element (M) composed of at least two elements selected from aluminum, manganese, niobium or molybdenum, and the composite hydroxide Or impregnating the surface of the composite hydroxide with the hydroxide of the additive element (M) produced by the neutralization treatment, followed by drying to add atoms of the additive element (M) A nickel cobalt-added element (M) composite hydroxide having a controlled ratio is obtained.
Step (c): The nickel cobalt-added element (M) composite hydroxide is fired at a temperature of 300 to 900 ° C. to obtain a nickel cobalt-added element (M) composite oxide.
Step (d): The nickel-cobalt additive element in which the nickel-cobalt additive element (M) composite oxide and the lithium compound are mixed and the mixture is baked at a temperature of 650 to 850 ° C. to control the atomic ratio of lithium. (M) A composite oxide is obtained.   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the nickel-cobalt composite hydroxide obtained in the step (a) is substantially spherical particles.

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