JP7056035B2 - Manufacturing method of positive electrode active material for non-aqueous secondary batteries and transition metal compounds - Google Patents

Description

The present invention relates to a method for producing a positive electrode active material for a non-aqueous secondary battery and a transition metal compound produced from a transition metal compound which is a precursor of the positive electrode active material.

In recent years, with the spread of portable electronic devices such as mobile phones and notebook personal computers, there is a strong demand for the development of small and lightweight non-aqueous electrolyte secondary batteries having high energy density. As a secondary battery satisfying such a requirement, there is a lithium ion secondary battery. In the lithium ion secondary battery, a material capable of desorbing and inserting lithium is used as the active material of the negative electrode and the positive electrode.

Lithium-ion secondary batteries are still being actively researched and developed, but among them, lithium-ion secondary batteries using layered or spinel-type lithium metal composite oxide as the positive electrode active material have a high voltage of 4V class. Therefore, it is being put into practical use as a battery having a high energy density.

The positive electrode active materials proposed so far include lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel, which is cheaper than cobalt, and lithium. Examples thereof include nickel-cobalt-manganese composite oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) and lithium-manganese composite oxide using manganese (LiMn ₂ O ₄ ).

Of these, lithium-nickel composite oxide has attracted attention as a positive electrode active material with good cycle characteristics, high capacity, and excellent battery characteristics, and attempts have been made to further increase the capacity for electric vehicles in recent years.

As a method for improving the battery characteristics of the lithium-nickel composite oxide, addition of various elements has been studied, and in particular, addition of a transition metal element such as W, Mo, Nb, Ta, Re, which can take an expensive number, is considered. It is considered valid.

For example, in Patent Document 1, the resistance inside the lithium ion secondary battery is reduced and the output is high by using a mixture of lithium metal composite oxide powder and lithium tungstate as the positive electrode material of the non-aqueous electrolyte secondary battery. It is said that it can bring about.

Japanese Unexamined Patent Publication No. 2016-225277

However, no method for adding a foreign element to increase the capacity of a lithium ion secondary battery using a lithium nickel composite oxide as a positive electrode has been proposed. Further, in the future, it is desired to further reduce the internal resistance value of the lithium ion secondary battery and increase the capacity.

Therefore, an object of the present invention is to provide a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery and a transition metal compound capable of obtaining a high capacity with a small internal resistance.

As a result of diligent studies to solve the above problems, the present inventor sprays and mixes a solution of a compound containing lithium and tungsten in the mixing step, and at least a part of the surface of the transition metal compound is lithium and By coating with a compound containing tungsten, it was found that the internal resistance is small and a high capacity can be obtained, and the present invention has been completed.

That is, the present invention is a method for producing a positive electrode active material for a non-aqueous secondary battery produced from a transition metal compound which is a precursor of a positive electrode active material, and is composed of at least primary particles and the primary particles thereof aggregated together. A mixing step of mixing the transition metal compound composed of the secondary particles and a solution in which a compound containing synthesized lithium and tungsten is dissolved to obtain a mixture, a drying step of drying the mixture to obtain a dried product, and the above-mentioned It has a firing step of mixing and firing a dried product and a lithium compound, and in the mixing step, a solution of the compound containing lithium and tungsten is sprayed and mixed, and at least a part of the surface of the transition metal compound. Is coated with a compound containing lithium and tungsten, the compound containing lithium and tungsten is lithium tungstate, and the composition formula of the lithium tungstate is Li 2 _WO 4 _.

By doing so, at least a part of the surface of the transition metal compound is coated with the compound containing lithium and tungsten, so that the positive electrode active material after firing is coated with the lithium tungsten compound, so that the internal resistance is small. Moreover, it is possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery capable of obtaining a high capacity. Further, in this way, the interaction with the surface of the transition metal compound is optimized, and lithium tungstate can be coated more uniformly.

At this time, in one aspect of the present invention, the transition metal compound is one selected from Ni, Co, M (M is Mg, Al, Ca, Ti, V, Cr, Mn, Mo, Nb, Zr). Any one of the nickel composite oxide or the nickel composite hydroxide containing the above elements) or a mixture thereof may be used.

In this way, it is possible to provide a positive electrode active material for a non-aqueous electrolyte secondary battery in which a transition metal compound is produced from a nickel composite oxide containing Ni, Co, and M or a nickel composite hydroxide.

At this time, in one aspect of the present invention, the molar percentage of tungsten in the compound containing lithium and tungsten is 0.05 to 0.05 with respect to the total molar amount of Ni, Co and M contained in the transition metal compound. It may be 0.15 mol%.

By doing so, the optimum amount of the compound containing lithium and tungsten can be obtained, and the obtained positive electrode active material can be sufficiently coated with the compound containing lithium and tungsten.

At this time, in one aspect of the present invention, the weight of the solution of the compound containing lithium and tungsten may be 5 to 20 wt% with respect to the weight of the transition metal compound.

By doing so, the solution of the compound containing lithium and tungsten can be sufficiently spread between the particles of the transition metal compound and on the surface thereof, and the surface of the transition metal compound can be uniformly coated.

At this time, in one aspect of the present invention, the solution of the compound containing lithium and tungsten may be an aqueous solution.

In this way, at least a part of the surface of the transition metal compound can be more uniformly coated with the compound containing lithium and tungsten.

At this time, in one aspect of the present invention, the lithium compound mixed in the firing step is selected from lithium hydroxide, lithiumoxy hydroxide, lithium oxide, lithium carbonate, lithium nitrate and lithium halide. It may be at least one kind or a mixture thereof.

By doing so, it is possible to prevent impurities from remaining after firing, reduce the internal resistance of the lithium ion secondary battery, and increase the capacity.

At this time, in one aspect of the present invention, the molar ratio of lithium in the lithium compound may be 0.98 to 1.25 with respect to the molar amount of the transition metal compound.

By doing so, the crystallinity of the obtained calcined powder can be improved, the internal resistance of the lithium ion secondary battery can be reduced, and the capacity can be increased.

At this time, in one aspect of the present invention, the firing step may be performed in an oxidizing atmosphere at a maximum temperature of 650 ° C. or higher and 780 ° C. or lower.

By doing so, the crystal structure of the positive electrode active material for a non-aqueous secondary battery can be stabilized.

At this time, in one aspect of the present invention, the obtained positive electrode active material for _a non-aqueous secondary battery may be represented by the general formula: Lia Ni _{1-xy Cox My WZO 2} . good. (In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo. A is 0.95 ≦ a ≦ 1.11. x is a numerical value satisfying 0 <x ≦ 0.15, y is a numerical value satisfying 0 <y ≦ 0.07, x + y ≦ 0.2, 0.05 ≦ z ≦ 0.15).

By doing so, it is possible to provide the above-mentioned general-type positive electrode active material for a non-aqueous secondary battery, which has a small internal resistance of the lithium ion secondary battery and can obtain a high capacity.

According to the present invention, it is possible to provide a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery and a transition metal compound capable of obtaining a high capacity while having a small internal resistance of the lithium ion secondary battery. Moreover, the manufacturing method is easy and suitable for production on an industrial scale, and its industrial value is extremely large.

FIG. 1 is a process diagram showing an outline of a method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a coin-type battery in the embodiment. 3A and 3B are Nyquist plot diagrams in the embodiment, FIG. 3A shows the sum of the solution resistance, the negative electrode resistance and its capacity, and the positive electrode resistance and its capacity, and FIG. 3B shows the above. Is shown in the circuit diagram.

Hereinafter, preferred embodiments of the present invention will be described in detail. The embodiments described below do not unreasonably limit the content of the present invention described in the claims, and can be modified without departing from the gist of the present invention. Moreover, not all of the configurations described in the present embodiment are indispensable as the means for solving the present invention. A method for producing a positive electrode active material for a non-aqueous secondary battery and a transition metal compound according to an embodiment of the present invention will be described in detail in the following order.
1. 1. Manufacturing method of positive electrode active material for non-aqueous secondary batteries 1-1. Mixing process 1-2. Drying process 1-3. Baking process 2. Transition metal compounds

<1. Manufacturing method of positive electrode active material for non-aqueous secondary batteries>
Hereinafter, a method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a process diagram showing an outline of a method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention. The method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention is produced from a transition metal compound which is a precursor of the positive electrode active material. The method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention includes at least a mixing step S1, a drying step S2, and a firing step S3. Further, the mixing step S1 is characterized in that a solution of the compound containing lithium and tungsten is sprayed and mixed, and at least a part of the surface of the transition metal compound is coated with the compound containing lithium and tungsten. Hereinafter, each step will be described in detail.

<1-1. Mixing step S1>
First, the mixing step S1 in the method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention will be described. In the mixing step S1, the transition metal compound composed of primary particles and secondary particles formed by aggregating the primary particles is mixed with a solution of a compound containing lithium and tungsten to obtain a mixture thereof.

Here, the mixing step S1 is characterized in that a solution of the compound containing lithium and tungsten is sprayed and mixed, and at least a part of the surface of the transition metal compound is coated with the compound containing lithium and tungsten. ..

This is because it is difficult for the compound containing lithium and tungsten to uniformly cover the surface of the transition metal compound in the conventional method in which a solution of a compound containing lithium and tungsten is directly added and mixed. Therefore, in the mixing step S1 in the method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention, a solution of a compound containing lithium and tungsten is sprayed and mixed.

By this method, the compound containing lithium and tungsten covers the particle surface of the transition metal compound widely and uniformly. Here, the transition metal compound which is a precursor of the positive electrode active material has a larger specific surface area than the synthesized positive electrode active material and has large pores in a wide range. However, even in such a surface state, by spraying and mixing the solution of the compound of lithium and tungsten, the particles of the compound of lithium and tungsten become fine particles, and the compound of lithium and tungsten penetrates through the pores to the inside of the precursor. The surface of the primary particles inside the positive electrode active material that can permeate and are synthesized can be easily and efficiently coated.

Therefore, by covering the particle surface of the transition metal compound widely and uniformly, it is possible to easily cover the surface of the primary particles inside the positive electrode active material to be synthesized, and during the charge / discharge reaction of the lithium ion secondary battery. The conduction path of lithium becomes good, and it becomes possible to increase the capacity and decrease the resistance of the lithium ion secondary battery.

The transition metal compound is a nickel composite oxide containing Ni, Co, M (M is one or more elements selected from Mg, Al, Ca, Ti, V, Cr, Mn, Mo, Nb, and Zr). Alternatively, it is preferably any one of nickel composite hydroxides or a mixture thereof.

By doing so, it is produced from a nickel composite oxide containing Ni, Co, and M or a nickel composite hydroxide, and is used for a non-aqueous electrolyte secondary battery capable of increasing the capacity and lowering the resistance of the lithium ion secondary battery. A positive electrode active material can be provided. The molar percentage of tungsten in the compound containing lithium and tungsten is preferably 0.05 to 0.15 mol% with respect to the total molar amount of Ni, Co and M contained in the transition metal compound.

When the molar percentage of the above tungsten is less than 0.05 mol%, the compound containing lithium and tungsten cannot sufficiently coat the surface of the transition metal compound, and sufficiently covers the surface of the resulting positive electrode active material. This is not possible, and since the conduction path of lithium during the charge / discharge reaction of the lithium ion secondary battery is not sufficiently formed, it is difficult to obtain higher capacity and lower resistance.

On the other hand, when the molar percentage of tungsten exceeds 0.15 mol%, the amount of the compound containing lithium and tungsten covering the surface of the transition metal compound increases, and the resulting lithium and tungsten covering the surface of the positive electrode active material are obtained. As the proportion of the compound contained increases, the capacity per weight decreases, and it is difficult to obtain higher capacity and lower resistance.

Therefore, within the above range, the optimum amount of the compound containing lithium and tungsten is added, and the obtained positive electrode active material can be sufficiently coated with the compound containing lithium and tungsten.

The weight of the solution of the compound containing lithium and tungsten is preferably 5 to 20 wt% with respect to the weight of the transition metal compound.

When the weight of the solution of the compound containing lithium and tungsten is less than 5 wt% with respect to the weight of the transition metal compound, the solution does not sufficiently spread on the surface of the transition metal compound, and the compound of lithium and tungsten is the transition metal compound. There is a risk that the surface of the particles will not be covered evenly.

On the other hand, when the weight of the solution of the compound containing lithium and tungsten exceeds 20 wt% with respect to the weight of the transition metal compound, the mixture of the transition metal compound and the compound containing lithium and tungsten becomes a paste at the time of mixing. As a result, the handleability is extremely deteriorated, and it may take time to dry the obtained mixture.

Therefore, within the above range, the optimum amount of the compound containing lithium and tungsten is added, and the obtained positive electrode active material can be sufficiently coated with the compound containing lithium and tungsten.

Further, the solution of the compound containing lithium and tungsten is preferably an aqueous solution. For example, when an organic solvent such as ethanol, methanol, or compound is used, the solvent tends to volatilize when sprayed, and the concentration of lithium and tungsten in the solution may increase, which may increase the viscosity of the solution. At this time, it is highly possible that the solution of the compound containing lithium and tungsten does not uniformly coat the surface of the transition metal compound. Therefore, the advantage of making an aqueous solution is a feature because it is sprayed at the time of mixing. If it is an aqueous solution, the solution is easy to handle. Thereby, the surface of the transition metal compound can be more uniformly coated with the compound containing lithium and tungsten.

The compound containing lithium and tungsten is preferably lithium tungstate. Further, it is preferable that the composition formula of the lithium tungstate is Li ₂ WO ₄ . By doing so, the interaction with the surface of the transition metal compound is optimized, and lithium tungstate can be coated more uniformly. As the mixing method, a known method may be used.

<1-2. Drying step S2>
Next, in the drying step S2 after the mixing step S1, the mixture is dried to obtain a dried product. Known conditions can be used as the drying conditions. That is, the temperature and time may be dried at a known temperature and time.

<1-3. Baking step S3>
Next, after the drying step S2, the dried product and the lithium compound are mixed and fired. When mixing the above dried product with the lithium compound, a general mixer can be used. For example, a shaker mixer, a Ladyge mixer, a Julia mixer, a V blender, or the like can be used to mix the lithium and tungsten compounds. The lithium compound may be uniformly mixed to the extent that the secondary particle shape of the transition metal compound coated with the above is not destroyed.

The lithium compound mixed in the firing step S3 is not particularly limited, but is at least one selected from lithium hydroxide, lithiumoxy hydroxide, lithium oxide, lithium carbonate, lithium nitrate and lithium halide, or at least one thereof. It is preferably a mixture. By doing so, it is possible to prevent impurities from remaining after firing, reduce the internal resistance of the lithium ion secondary battery, and increase the capacity. In particular, it is more preferable to use a nickel composite hydroxide or a lithium hydroxide having good reactivity with the nickel composite oxide.

The mixing ratio of the transition metal compound coated with the compound containing lithium and tungsten and the lithium compound, which is mixed in the mixing step S1, is not particularly limited, but the transition between lithium and other than lithium in the positive electrode active material after firing described below. As for the ratio of the metal element, the ratio of lithium and the transition metal element other than lithium in the mixture of the transition metal compound coated with the compound containing lithium and tungsten and the lithium compound mixed in the firing step S3 is substantially maintained.

Therefore, the molar ratio of lithium in the lithium compound is preferably 0.98 to 1.25 with respect to the molar amount of the transition metal compound.

If the molar ratio of lithium in the lithium compound is less than 0.98 with respect to the molar amount of the transition metal compound, the crystallinity of the obtained calcined powder may be very poor. On the other hand, if the molar ratio exceeds 1.25, the sintering of the secondary particles is likely to proceed and coarse particles are generated, or unreacted lithium remains and the internal resistance is increased, which is not preferable.

Therefore, within the above range, the crystallinity of the calcined powder can be maintained well, and the coarsening of the particles due to the progress of sintering of the particles at the time of calcining can be suppressed. Therefore, the crystallinity of the obtained calcined powder is improved, the internal resistance of the lithium ion secondary battery is small, and the capacity can be increased.

Further, the firing step S3 is preferably performed in an oxidizing atmosphere with a maximum temperature of 650 ° C. or higher and 780 ° C. or lower.

If the maximum temperature is more than 500 ° C., a composite oxide (lithium-nickel composite oxide) is produced, but if the maximum temperature is less than 650 ° C., the crystals are underdeveloped and structurally unstable. When such a composite oxide (lithium-nickel composite oxide) is used as the positive electrode active material, the crystal structure of the positive electrode active material is easily destroyed due to a phase transition due to charging and discharging. In addition, the growth of primary particles may be insufficient, and the specific surface area and porosity may become too large.

On the other hand, if it is fired at a temperature such that the maximum temperature exceeds 780 ° C., cation mixing is likely to occur, the layered structure in the crystal of the lithium nickel composite oxide is destroyed, and it may be difficult to insert or remove lithium ions. There is sex. Moreover, there is a possibility that the crystals of the lithium nickel composite oxide will be decomposed and nickel oxide or the like will be produced. Further, the composite oxide particles may be sintered to form coarse composite oxide particles, and the average particle size of the lithium nickel composite oxide may become too large. Then, the primary particles may grow and the specific surface area and porosity may become too small. As a result, by setting the temperature in the above range, it is possible to further increase the capacity and reduce the resistance.

The holding time in the firing step is preferably 1 to 6 hours, more preferably 2 to 4 hours. If the retention time is less than 1 hour, crystallization will be insufficient, and if it exceeds 6 hours, calcination will proceed too much and cation mixing may occur.

In this firing, a lithium nickel composite oxide can be synthesized unless the atmosphere is non-oxidizing, and it is preferable to use a mixed gas atmosphere of 18 to 100% by volume of oxygen and an inert gas, and the oxygen concentration is 90% by volume or more. Is more preferable.

If the lithium compound is fired in an atmosphere having an oxygen concentration of 18% by volume or more, that is, an atmosphere having an oxygen content higher than that of the air atmosphere, the reactivity between the lithium compound and the nickel composite hydroxide or the nickel composite oxide can be improved. In order to further increase the reactivity and obtain a lithium nickel composite oxide having excellent crystallinity, it is more preferable to use a mixed gas atmosphere having an oxygen concentration of 90% by volume or more, and an oxygen atmosphere (oxygen concentration of 98% or more). Is even more preferred. Further, it is preferable to create an atmosphere that has been dehumidified and decarbonated.

The positive electrode active material for a non-aqueous secondary battery obtained through the above-mentioned steps is represented by _a general formula: Lia Ni _{1-xy Co x} My W _{ZO 2} . (In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo. A is 0.95 ≦ a ≦ 1.11. x is a numerical value satisfying 0 <x ≦ 0.15, y is a numerical value satisfying 0 <y ≦ 0.07, x + y ≦ 0.2, 0.05 ≦ z ≦ 0.15.) It is possible to provide the above-mentioned general-type positive electrode active material for a non-aqueous secondary battery, which has a small internal resistance of the secondary battery and can obtain a high capacity.

<2. Transition metal compounds>
Next, the transition metal compound according to the embodiment of the present invention will be described. The transition metal compound according to one embodiment of the present invention is one or more elements selected from Ni, Co, M (M is Mg, Al, Ca, Ti, V, Cr, Mn, Mo, Nb, Zr). ) Is a transition metal compound. The transition metal compound is any one of nickel composite oxides or nickel composite hydroxides or a mixture thereof, and the transition metal compound is composed of primary particles and the primary particles thereof aggregated together. It consists of next particles. Further, it is characterized in that at least a part of the surface of the primary particles and the secondary particles formed by aggregating the primary particles is coated with a compound containing lithium and tungsten.

By doing so, by covering the particle surface of the transition metal compound widely and uniformly, the surface of the primary particles inside the positive electrode active material to be synthesized can also be easily coated, and the lithium ion secondary battery can be charged. The conduction path of lithium during the discharge reaction becomes good, and it becomes possible to increase the capacity and decrease the resistance of the lithium ion secondary battery.

The molar percentage of tungsten in the compound containing lithium and tungsten may be 0.05 to 0.15 mol% with respect to the total molar amount of Ni, Co and M contained in the transition metal compound. preferable. The critical significance in this range is the same as that described in the method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention.

Further, it is preferable that the compound containing lithium and tungsten is lithium tungstate, and the composition formula of the lithium tungstate is Li ₂ WO ₄ . The preferred reason is also the same as that described in the method for producing a positive electrode active material for a non-aqueous secondary battery according to an embodiment of the present invention.

Next, a method for producing a positive electrode active material for a non-aqueous secondary battery and a transition metal compound according to an embodiment of the present invention will be described in detail with reference to Examples. The present invention is not limited to these examples.

(Example 1)
(Manufacturing of positive electrode active material for non-aqueous secondary batteries)
The transition metal compound which is the precursor of the positive electrode active material was synthesized by a known method, and a nickel composite oxide (Ni _0.88 Co _0.06 Al _0.06 O) was used. Then, a solution of the compound containing lithium and tungsten to be mixed with the nickel composite oxide was prepared as follows.

23.9 g of powdered lithium hydroxide was mixed with 115.9 g of powdered tungsten oxide and calcined at 200 ° C. for 2 hours in a platinum crucible to obtain lithium tungstate. The obtained lithium tungstate was confirmed to be Li ₂ WO ₄ by XRD qualitative analysis. The crucible was put into a beaker containing 7.3 liters of pure water, and the entire amount of lithium tungstate was dissolved to obtain an aqueous solution of lithium tungstate. The concentration of the lithium tungstate aqueous solution determined from the calculated production of Li ₂ WO ₄ was 0.068 mol / L.

As a mixing step, 20 g of the lithium tungstic acid aqueous solution (20 wt% with respect to the nickel composite oxide) was sprayed onto 100 g of the nickel composite oxide and mixed to obtain a mixture. The molar percentage (W / (NI + Co + Al)) of tungsten in the sprayed aqueous solution of lithium tungstate to the total molar amount of nickel, cobalt, and aluminum in the nickel composite oxide is 0.10 mol%. The percentage concentration of this tungsten is the concentration of tungsten in the obtained positive electrode active material. Then, as a drying step, the above mixture was dried at 120 ° C. for 12 hours under vacuum.

As a firing step, 99.89 g of the nickel composite oxide coated with lithium tungstate obtained above and 32.64 g of lithium hydroxide were mixed with a shaker mixer, and the maximum temperature was set to 675 ° C. for 3 hours in an oxygen atmosphere. It was calcined to obtain a lithium-nickel composite oxide coated with lithium tungstate, which was used as a positive electrode material.

The tungsten content in this positive electrode material was analyzed by the ICP method, and it was confirmed that the composition was 0.10 mol% with respect to the total of nickel, cobalt and the additive element M.

(Battery manufacturing and evaluation)
A 2032 type coin battery 1 (hereinafter referred to as a coin type battery 1) shown in FIG. 2 was used for the evaluation of the positive electrode active material. As shown in FIG. 2, the coin-type battery 1 is composed of a case 2 and an electrode 3 housed in the case 2.

The case 2 has a positive electrode can 2a that is hollow and has one end open, and a negative electrode can 2b that is arranged in the opening of the positive electrode can 2a. When the negative electrode can 2b is arranged in the opening of the positive electrode can 2a, , A space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a.

The electrode 3 is composed of a positive electrode 3a, a separator 3c, and a negative electrode 3b, and is laminated so as to be arranged in this order. The positive electrode 3a contacts the inner surface of the positive electrode can 2a, and the negative electrode 3b contacts the inner surface of the negative electrode can 2b. It is housed in the case 2.

The case 2 is provided with a gasket 2c, and the gasket 2c fixes the relative movement between the positive electrode can 2a and the negative electrode can 2b so as to maintain a non-contact state. Further, the gasket 2c also has a function of sealing the gap between the positive electrode can 2a and the negative electrode can 2b and airtightly blocking the space between the inside and the outside of the case 2.

The coin-type battery 1 used was manufactured as follows. First, 52.5 mg of the positive electrode active material, 15 mg of acetylene black and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa to prepare a positive electrode 3a.

Next, the prepared positive electrode 3a was dried in a vacuum dryer at 120 ° C. for 12 hours. Using the dried positive electrode 3a, the negative electrode 3b, the separator 3c, and the electrolytic solution, the coin-type battery 1 of FIG. 2 was produced in a glove box having an Ar atmosphere in which the dew point was controlled to −80 ° C.

For the negative electrode 3b, a graphite powder having an average particle size of about 20 μm punched into a disk shape having a diameter of 14 mm and a negative electrode sheet coated with polyvinylidene fluoride on a copper foil were used. Further, as the separator 3c, a polyethylene porous membrane having a film thickness of 25 μm was used. As the electrolytic solution, an equal amount mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting electrolyte (manufactured by Tomiyama Pure Chemical Industries, Ltd.) was used.

The initial discharge capacity and positive electrode resistance indicating the performance of the manufactured coin-type battery 1 were evaluated by the following methods. The initial discharge capacity is the cutoff voltage 4 with the current density for the positive electrode set to 0.1 mA / cm ² after the open circuit voltage OCV (open circuit voltage) is stabilized by leaving it for about 24 hours after manufacturing the coin-type battery 1. The initial discharge capacity was defined as the capacity when the battery was charged to 3 V, paused for 1 hour, and then discharged to a cutoff voltage of 3.0 V.

The positive electrode resistance is measured by the AC impedance method using a frequency response analyzer and a potentiogalvanostat (manufactured by Solartron, 1255B) after charging the coin-type battery 1 with a charging potential of 4.1 V, and is shown in FIG. 3 (A). Obtained the Nyquist plot shown. Note that FIG. 3B shows a circuit diagram of FIG. 3A.

Since the obtained Nyquist plot shown in FIG. 3 (A) is represented as the sum of the solution resistance, the negative electrode resistance and its capacitance, and the characteristic curve showing the positive electrode resistance and its capacitance, an equivalent circuit is constructed based on this Nyquist plot. The value of the positive electrode resistance was calculated by using the fitting calculation.

As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 201.0 mAh / g, and the positive electrode resistance was 2.1 Ω.

(Example 2)
In Example 2, the weight concentration of the aqueous solution of lithium tungstate was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%. The maximum temperature in the firing step was 710 ° C. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 202.0 mAh / g, and the positive electrode resistance was 2.1 Ω.

(Example 3)
In Example 3, the weight concentration of the aqueous solution of lithium tungstate was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%. The maximum temperature in the firing step was set to 750 ° C. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 203.0 mAh / g, and the positive electrode resistance was 2.0 Ω.

(Example 4)
In Example 4, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.034 mol / L. The weight concentration of the lithium tungstate aqueous solution was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.05 mol%. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 204.0 mAh / g, and the positive electrode resistance was 2.0 Ω.

(Example 5)
In Example 5, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.102 mol / L. The weight concentration of the aqueous solution of lithium tungstate was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.15 mol%. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 202.0 mAh / g, and the positive electrode resistance was 2.0 Ω.

(Example 6)
In Example 6, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.278 mol / L. The weight concentration of the lithium tungstate aqueous solution was 5 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 201.0 mAh / g, and the positive electrode resistance was 2.1 Ω.

(Example 7)
In Example 7, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.139 mol / L. The weight concentration of the lithium tungstate aqueous solution was 10 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 201.0 mAh / g, and the positive electrode resistance was 2.1 Ω.

(Example 8)
In Example 8, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.091 mol / L. The weight concentration of the lithium tungstic acid aqueous solution was 15 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 202.0 mAh / g, and the positive electrode resistance was 2.0 Ω.

(Example 9)
In Example 9, the weight concentration of the lithium tungstate aqueous solution was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%. The maximum temperature in the firing step was 640 ° C. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 197.0 mAh / g, and the positive electrode resistance was 2.4 Ω.

(Example 10)
In Example 10, the weight concentration of the lithium tungstate aqueous solution was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%. The maximum temperature in the firing step was set to 800 ° C. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 196.5 mAh / g, and the positive electrode resistance was 2.4 Ω.

(Example 11)
In Example 11, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.139 mol / L. The weight concentration of the aqueous solution of lithium tungstate was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was 0.20 mol%. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 196.5 mAh / g, and the positive electrode resistance was 2.2 Ω.

(Example 12)
In Example 12, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.021 mol / L. The weight concentration of the aqueous solution of lithium tungstate was 20 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was 0.03 mol%. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 197.0 mAh / g, and the positive electrode resistance was 2.5 Ω.

(Example 13)
In Example 13, the concentration of the lithium tungstate aqueous solution in the mixing step was 0.056 mol / L. The weight concentration of the aqueous solution of lithium tungstate was 25 wt%. The molar percentage of tungsten in the compound containing lithium and tungsten was set to 0.10 mol%. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 197.0 mAh / g, and the positive electrode resistance was 2.4 Ω.

(Comparative Example 1)
As Comparative Example 1, an aqueous solution of lithium tungstate in the mixing step was sprayed and not mixed. Other conditions were the same as in Example 1.

Further, the battery was manufactured and evaluated in the same manner as in Example 1. As a result, the initial discharge capacity obtained from the coin-type battery using the obtained positive electrode active material was 196.0 mAh / g, and the positive electrode resistance was 2.5 Ω. The results under the above conditions are shown in Table 1.

In all the examples in which the lithium tungstate aqueous solution was sprayed and mixed in the mixing step, the initial discharge capacity of the battery was higher and the positive electrode resistance was smaller than in the comparative example in which the lithium tungstate aqueous solution was sprayed and not mixed. It became.

Further, comparing Example 1 in which the molar percentage of the sprayed tungsten is in the range of 0.05 to 0.15 mol% and Examples 11 and 12 outside the above range, Example 1 is the initial stage of the battery. The discharge capacity was high and the positive electrode resistance was also small. Therefore, it was found that when the molar percentage of tungsten in the compound containing lithium and tungsten is 0.05 to 0.15 mol%, the initial discharge capacity of the battery is further high and the positive electrode resistance is also small.

Further, comparing Examples 1, 6, 7, and 8 in which the molality of the solution of the compound containing lithium and tungsten is 5 to 20 wt% and Example 13, which is outside the above range, Examples 1, 6, and 7. , 8 had a higher initial discharge capacity of the battery and a smaller positive electrode resistance. Therefore, it was found that when the molality of the solution of the compound containing lithium and tungsten is 5 to 20 wt%, the initial discharge capacity of the battery is further high and the positive electrode resistance is also small.

Further, comparing Examples 1, 2 and 3 in which the maximum temperature in the firing step is 650 to 780 ° C. and Examples 9 and 10 outside the above range, Examples 1, 2 and 3 are the initial batteries. The discharge capacity was high and the positive electrode resistance was also small. Therefore, it was found that when the maximum temperature in the firing step is 650 to 780 ° C., the initial discharge capacity of the battery is further high and the positive electrode resistance is also small.

From the above, according to the method for producing a positive electrode active material for a non-aqueous secondary battery and the transition metal compound according to the embodiment of the present invention, the internal resistance of the lithium ion secondary battery is small and the capacity can be increased. We were able to provide a method for producing a positive electrode active material for an aqueous electrolyte secondary battery and a transition metal compound. Moreover, the manufacturing method is easy and suitable for production on an industrial scale, and its industrial value is extremely large.

Although each embodiment and each embodiment of the present invention have been described in detail as described above, those skilled in the art will be able to make many modifications that do not substantially deviate from the new matters and effects of the present invention. , Will be easy to understand. Therefore, all such modifications are included in the scope of the present invention.

For example, a term described at least once in a specification or drawing with a different term in a broader or synonymous manner may be replaced by that different term anywhere in the specification or drawing. Further, the method for producing the positive electrode active material for a non-aqueous secondary battery, the composition of the transition metal compound, and the operation are not limited to those described in each embodiment and each embodiment of the present invention, and various modifications can be carried out.

S1 mixing process, S2 drying process, S3 firing process 1 2032 type coin battery, 2 cases, 2a positive electrode can, 2b negative electrode can, 2c gasket, 3 electrode, 3a positive electrode, 3b negative electrode, 3c separator

Claims (9)

A method for producing a positive electrode active material for a non-aqueous secondary battery, which is produced from a transition metal compound which is a precursor of the positive electrode active material.
At least, a mixing step of mixing the transition metal compound composed of primary particles and secondary particles composed of aggregated primary particles with a solution in which a synthesized compound containing lithium and tungsten is dissolved to obtain a mixture.
A drying step of drying the mixture to obtain a dried product,
It has a firing step of mixing the dried product and a lithium compound and firing.
In the mixing step, a solution of the compound containing lithium and tungsten is sprayed and mixed, and at least a part of the surface of the transition metal compound is coated with the compound containing lithium and tungsten.
The compound containing lithium and tungsten is lithium tungstate.
A method for producing a positive electrode active material for a non-aqueous secondary battery, wherein the composition formula of lithium tungstate is Li ₂ WO ₄ . The transition metal compound is a nickel composite oxide containing Ni, Co, M (M is one or more elements selected from Mg, Al, Ca, Ti, V, Cr, Mn, Mo, Nb, and Zr). The method for producing a positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein it is any one of nickel composite hydroxides or a mixture thereof. The molar percentage of tungsten in the compound containing lithium and tungsten is characterized by being 0.05 to 0.15 mol% with respect to the total molar amount of Ni, Co and M contained in the transition metal compound. The method for producing a positive electrode active material for a non-aqueous secondary battery according to claim 2. The non-aqueous system according to any one of claims 1 to 3, wherein the weight concentration of the solution of the compound containing lithium and tungsten is 5 to 20 wt% with respect to the weight of the transition metal compound. A method for manufacturing a positive electrode active material for a secondary battery. The method for producing a positive electrode active material for a non-aqueous secondary battery according to any one of claims 1 to 4, wherein the solution of the compound containing lithium and tungsten is an aqueous solution. The lithium compound mixed in the firing step is at least one selected from lithium hydroxide, lithiumoxy hydroxide, lithium oxide, lithium carbonate, lithium nitrate and lithium halide, or a mixture thereof. The method for producing a positive electrode active material for a non-aqueous secondary battery according to any one of claims 1 to 5 , which is characterized by the above-mentioned method. The non-aqueous system according to any one of claims 1 to 6 , wherein the molar ratio of lithium in the lithium compound is 0.98 to 1.25 with respect to the molar amount of the transition metal compound. A method for manufacturing a positive electrode active material for a secondary battery. The positive electrode active material for a non-aqueous secondary battery according to any one of claims 1 to 7 , wherein the firing step is performed in an oxidizing atmosphere at a maximum temperature of 650 ° C. or higher and 780 ° C. or lower. Manufacturing method. Any of claims 1 to 8 , wherein the obtained positive electrode active material for a non-aqueous secondary battery is represented by _a general formula: _Lia Ni _1-xy Co _x My W _z O ₂ . The method for producing a positive electrode active material for a non-aqueous secondary battery according to item 1.
(In the formula, M is at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo. A is 0.95 ≦ a ≦ 1.11. x is a numerical value satisfying 0 <x ≦ 0.15, y is a numerical value satisfying 0 <y ≦ 0.07, x + y ≦ 0.2, 0.05 ≦ z ≦ 0.15).

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