JP6050403B2 - Positive electrode active material for lithium ion battery, positive electrode for lithium ion battery, and lithium ion battery - Google Patents

Description

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

Lithium-containing transition metal oxides are generally used as positive electrode active materials for lithium ion batteries. Specifically, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), etc., improved characteristics (higher capacity, cycle characteristics, storage characteristics, reduced internal resistance) In order to improve the rate characteristics and safety, it is underway to combine them. Lithium ion batteries for large-scale applications such as in-vehicle use and load leveling are required to have different characteristics from those of conventional mobile phones and personal computers.

  Conventionally, various researches and developments have been made on improving the battery characteristics required for such lithium ion batteries. As means for improving battery characteristics, for example, a material in which the electrode density of a positive electrode material is improved and large and small particles are mixed has been proposed. The material is configured such that the small particles of the same material fill the gaps between the large particles of the Li-containing transition metal composite oxide.

  As such a technique, for example, in Patent Document 1, the average particle size of the lithium composite oxide particles is in the range of 0.1 to 50 μm, and the particle size distribution of the lithium composite oxide particles has two or more peaks. A positive electrode active material characterized in that it exists is disclosed. And according to this, it is described that the positive electrode active material which can provide the nonaqueous electrolyte secondary battery which has the outstanding initial capacity and capacity | capacitance retention is obtained.

In Patent Document 2, the particles constituting the lithium metal composite oxide powder are mainly composed of secondary particles formed by aggregating a plurality of primary particles of the lithium metal composite oxide, and the shape of the secondary particles is A particle having a particle diameter of 1 μm or less is added to a particle having a spherical shape or an elliptical spherical shape, having a particle size substantially in the range of 1 to 40 μm, an average particle size of 5 to 11 μm, and a normal particle size distribution. The powder has a specific surface area of 0.5 to 3.5% by volume, and the specific surface area of the powder is not greater than the specific surface area of the powder formed by removing particles having a particle diameter of 1 μm or less from the powder. Non-aqueous system characterized in that the tap density of the powder is 3 m ² / g larger, and the tap density of the powder is 0.2 g / cm ³ smaller than the tap density of the powder formed by removing particles having a particle diameter of 1 μm or less from the powder. Positive electrode active material for electrolyte secondary battery It has been disclosed. And thereby, inconvenience in production such as dust generation when the whole of the powder constituting the positive electrode active material for a non-aqueous electrolyte secondary battery is pulverized, capacity reduction due to lower packing density does not occur, Further, it is described that a secondary battery capable of increasing output can be provided by increasing the contact area between the electrolytic solution and the positive electrode active material and increasing the number of places where Li ions diffuse.

JP 2000-82466 A Japanese Patent No. 4766840

  However, when a positive electrode active material is produced by mixing a large particle size and a small particle size Li-containing transition metal composite oxide, there are the following problems. In general, a small particle size Li-containing transition metal composite oxide is rapidly deteriorated and greatly inferior in charge / discharge characteristics because the area of the surface-modified part formed by the reaction of the electrolytic solution by charge / discharge is large with respect to the volume. . Accordingly, when a positive electrode active material in which a Li-containing transition metal composite oxide having a large particle size and a small particle size is mixed is used, the charge / discharge function of the battery may be deteriorated. Moreover, the Li-containing transition metal composite oxide having a small particle size reduces the activity of the surface of the adjacent Li-containing transition metal composite oxide having a large particle size in order to alter the electrolyte solution in the vicinity thereof. There is a possibility that the charge / discharge characteristics of the battery may be deteriorated.

  With respect to such a problem, an object of the present invention is to provide a positive electrode active material for a lithium ion battery having good battery characteristics.

  As a result of various investigations to solve such problems, the present inventor has mixed the Li-containing transition metal composite oxide with a predetermined amount of inorganic ceramics as particles having a small particle diameter, thereby obtaining battery characteristics. It has been found that a positive electrode active material for a lithium ion battery can be obtained.

The present invention completed on the basis of the above knowledge includes, in one aspect, a Li-containing transition metal composite oxide, and an inorganic ceramic having an average particle diameter of 0.18 to 1 μm and 10 to 1000 wtppm, The oxide has the composition formula: Li _{1 + x} Ni _1-y Me _y O _{2 + z}
(In the above formula, Me is one or more of Mn, Co, Al, and Mg, x is −0.1 to 0.1, y is the total composition of metals represented by Me, and 0 .1 to 0.5, and z is -0.1 to 0.2.)
The inorganic ceramic is an oxide, nitride, carbide, or a combination of one or more elements selected from Al, Si, Mg, Zr, and Y, and the Li-containing transition metal composite oxide the average particle diameter of the object is positive electrode active material for lithium ion batteries Ru 4~12μm der.

In another embodiment of the positive electrode active material for a lithium ion battery of the present invention, the inorganic ceramic material is selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , SiC, and YSZ (yttria stabilized zirconia). One or more selected.

  In still another aspect, the present invention provides a positive electrode for a lithium ion battery using the positive electrode active material for a lithium ion battery of the present invention.

  In still another aspect, the present invention is a lithium ion battery using the positive electrode for a lithium ion battery of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material for lithium ion batteries with a favorable battery characteristic can be provided.

(Configuration of positive electrode active material for lithium ion battery)
The positive electrode active material for a lithium ion battery of the present invention includes a Li-containing transition metal composite oxide and an inorganic ceramic having an average particle diameter of 0.02 to 1 μm and 10 to 1000 wtppm. According to such a configuration, the inorganic ceramic functions as a particle having a small particle size and promotes the contact between the Li-containing transition metal composite oxides having a large particle size. Rate characteristics are improved. Moreover, since the Li-containing transition metal composite oxide is not used as a particle having a small particle size as in the prior art, and the deterioration of the particle having a small particle size is suppressed, the rate characteristics of the battery using the positive electrode active material are deteriorated. Is satisfactorily suppressed.

  If the average particle size of the inorganic ceramic is less than 0.02 μm, the effect of improving the rate characteristic is poor, and if it exceeds 1 μm, the resistance increases and the rate characteristic deteriorates. Further, if the content of the inorganic ceramic is less than 10 wtppm, the effect of improving the rate characteristics is poor, and if it exceeds 1000 wtppm, the initial capacity of the battery using the positive electrode active material is lowered. The inorganic ceramics preferably has an average particle diameter of 0.1 to 1 μm, and more preferably 0.3 to 0.9 μm. Moreover, it is preferable that content of an inorganic ceramic is 50-1000 wtppm, and it is more preferable that it is 100-500 wtppm.

In the positive electrode active material for a lithium ion battery according to the present invention, the inorganic ceramic is an oxide, nitride, carbide or combination of one or more elements selected from Al, Si, Mg, Zr, and Y. It is preferable that it is at least one selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , SiC, and YSZ (yttria stabilized zirconia).

  In the positive electrode active material for a lithium ion battery of the present invention, the Li-containing transition metal composite oxide preferably has an average particle size of 4 to 12 μm. When the average particle size of the Li-containing transition metal composite oxide is less than 4 μm, the added ceramic particles have a relatively larger particle size than the Li-containing transition metal composite oxide, so that the added ceramic particles contain Li. There is a possibility that the effect of hindering the contact between the transition metal composite oxides may occur. In addition, when the average particle size of the Li-containing transition metal composite oxide exceeds 12 μm, the gap between the Li-containing transition metal composite oxide particles is increased to promote the contact between the Li-containing transition metal composite oxide particles. Needs to add a large amount of ceramic particles, which may cause a problem of reducing the discharge capacity of the battery. The average particle size of the Li-containing transition metal composite oxide is more preferably 4 to 10 μm, and even more preferably 6 to 10 μm.

In the positive electrode active material for a lithium ion battery of the present invention, the Li-containing transition metal composite oxide has a composition formula: Li _{1 + x} Ni _1-y Me _y O _{2 + z}
(In the above formula, Me is one or more of Mn, Co, Al, and Mg, x is −0.1 to 0.1, y is the total composition of metals represented by Me, and 0 .1 to 0.5, and z is -0.1 to 0.2.)
It is preferable to be represented by

  The ratio of lithium to all metals in the positive electrode active material for a lithium ion battery is 0.9 to 1.1. If the ratio is less than 0.9, it is difficult to maintain a stable crystal structure. This is because there is a risk that it will not be possible to secure a high capacity. In addition, since the composition of nickel in the positive electrode active material for lithium ion batteries is 0.5 to 0.9, the capacity, output, and safety of the lithium ion battery using the positive electrode active material for lithium ion batteries are balanced. Improve well.

(Method for producing positive electrode active material for lithium ion battery)
The manufacturing method of the positive electrode active material for lithium ion batteries which concerns on embodiment of this invention is demonstrated in detail.
-Production of Li-containing transition metal composite oxide powder-
First, a metal salt solution is prepared by dissolving nickel nitrate and, if necessary, cobalt nitrate, manganese nitrate, aluminum nitrate, and magnesium nitrate in pure water so that a predetermined amount of metal atoms is present. Next, while stirring a solution in which lithium carbonate is added and dispersed in pure water so that the molar number of lithium and the total of the metal elements is 0.9 to 1.1: 1, the metal salt solution is stirred. The slurry is dropped to prepare a slurry containing Li, Ni, and in some cases Co, Mn, Al, and Mg.
Next, the slurry is spray-dried using, for example, a micro mist dryer having a three-fluid nozzle to obtain a powder containing Li, Ni, and optionally Co, Mn, Al, and Mg.
Next, when the powder contains 70% or more and 90% or less of Ni with respect to the total amount of metal, for example, using a roller hearth kiln, the powder is fired at 880 ° C. for 2 hours, and then 700 hours over 1 hour. The temperature is lowered to 0 ° C. and held for 2 hours, and then cooled to room temperature over 3 hours. When the powder contains Ni of 50% or more and less than 70% with respect to the total amount of metal, for example, using a roller hearth kiln, the powder is fired at 900 ° C. for 2 hours and then 700 ° C. over 1 hour. The temperature is lowered to 2 hours and held for 2 hours, and then cooled to room temperature over 3 hours.
Next, the obtained fired product is pulverized using, for example, a roll mill and a pulverizer to obtain a Li-containing transition metal composite oxide powder.

-Preparation of inorganic ceramic powder-
The inorganic ceramic powder is appropriately pulverized by, for example, a jet mill to prepare a product having a predetermined particle size.

-Production of positive electrode active material-
The positive electrode active material for a lithium ion battery of the present invention is obtained by adding the above-mentioned inorganic ceramic powder to the above-mentioned Li-containing transition metal composite oxide powder and mixing the powder using, for example, a ball mill.

(Configuration of positive electrode for lithium ion battery and lithium ion battery using the same)
The positive electrode for a lithium ion battery according to an embodiment of the present invention includes, for example, a positive electrode mixture prepared by mixing a positive electrode active material for a lithium ion battery having the above-described configuration, a conductive additive, and a binder from an aluminum foil or the like. The current collector has a structure provided on one side or both sides. Moreover, the lithium ion battery which concerns on embodiment of this invention is equipped with the positive electrode for lithium ion batteries of such a structure.

  Examples for better understanding of the present invention and its advantages are provided below, but the present invention is not limited to these examples.

-Production of Li-containing transition metal composite oxide powder-
(Examples 1-7 , 9-23 , Comparative Examples 1-14, Reference Examples 1-3 , 9 )
First, a metal salt solution was prepared by dissolving nickel nitrate, manganese nitrate, and cobalt nitrate in pure water so that the molar ratios of Ni, Mn, and Co atoms were 8: 1: 1, respectively. Next, the metal salt solution is dropped while stirring a solution in which lithium carbonate is added and dispersed in pure water so that the molar ratio of lithium to the total of the metal elements is 1.04: 1. A slurry containing Ni, Co and Mn was prepared. Next, the slurry was spray-dried using a micro mist dryer having a three-fluid nozzle to obtain a powder containing Li, Ni, Co and Mn. Next, using a roller hearth kiln, the powder was heated from room temperature to 880 ° C. over 1 hour and held for 2 hours. After firing, the temperature was lowered to 700 ° C. over 1 hour. After maintaining the time, it was cooled to room temperature over 3 hours. Next, the obtained fired product was pulverized using a roll mill and a pulverizer, and the pulverization strength in the pulverizer was adjusted to obtain three types of particle sizes of Li-containing transition metal composite oxide powder A.

(Examples 24 to 25, Comparative Example 15, Reference Example 4)
A metal salt solution was prepared by dissolving nickel nitrate and manganese nitrate in pure water so that the molar ratio of Ni and Mn atoms was 8: 2, respectively. Next, the metal salt solution is dropped while stirring a solution in which lithium carbonate is added and dispersed in pure water so that the molar ratio of lithium to the total of the metal elements is 1.02: 1. A slurry containing Ni, Ni and Mn was prepared. Next, the slurry was spray-dried using a micro mist dryer having a three-fluid nozzle to obtain a powder containing Li, Ni, and Mn. Next, using a roller hearth kiln, the powder was heated from room temperature to 880 ° C. over 1 hour and held for 2 hours. After firing, the temperature was lowered to 700 ° C. over 1 hour. After maintaining the time, it was cooled to room temperature over 3 hours. Next, the obtained fired product was pulverized using a roll mill and a pulverizer to obtain a Li-containing transition metal composite oxide powder B.

(Examples 26 to 27, Comparative Example 16, Reference Example 5)
A metal salt solution was prepared by dissolving nickel nitrate, cobalt nitrate, and aluminum nitrate in pure water so that the molar ratios of Ni, Co, and Al atoms were 8: 1: 1, respectively. Next, the metal salt solution is dropped while stirring a solution in which lithium carbonate is added and dispersed in pure water so that the molar ratio of lithium to the total of the metal elements is 1.00: 1. A slurry containing Ni, Co, and Al was prepared. Next, the slurry was spray-dried using a micro mist dryer having a three-fluid nozzle to obtain a powder containing Li, Ni, Co, and Al. Next, using a roller hearth kiln, the powder was heated from room temperature to 880 ° C. over 1 hour and held for 2 hours. After firing, the temperature was lowered to 700 ° C. over 1 hour. After maintaining the time, it was cooled to room temperature over 3 hours. Next, the obtained fired product was pulverized using a roll mill and a pulverizer to obtain a Li-containing transition metal composite oxide powder C.

(Examples 28 to 29, Comparative Example 17, Reference Example 6)
A metal salt solution was prepared by dissolving nickel nitrate, cobalt nitrate, and magnesium nitrate in pure water so that the molar ratios of Ni, Co, and Mg atoms were 8: 1: 1, respectively. Next, the metal salt solution is dropped while stirring a solution in which lithium carbonate is added and dispersed in pure water so that the molar ratio of lithium to the total of the metal elements is 1.04: 1. A slurry containing Ni, Co, and Mg was prepared. Next, the slurry was spray-dried using a micro mist dryer having a three-fluid nozzle to obtain a powder containing Li, Ni, Co, and Mg. Next, using a roller hearth kiln, the powder was heated from room temperature to 880 ° C. over 1 hour and held for 2 hours. After firing, the temperature was lowered to 700 ° C. over 1 hour. After maintaining the time, it was cooled to room temperature over 3 hours. Next, the obtained fired product was pulverized using a roll mill and a pulverizer to obtain a Li-containing transition metal composite oxide powder D.

(Examples 30 to 31, Comparative Example 18, Reference Example 7)
A metal salt solution was prepared by dissolving nickel nitrate, manganese nitrate, and cobalt nitrate in pure water so that the molar ratios of Ni, Mn, and Co atoms were 5: 3: 2, respectively. Next, the metal salt solution is dropped while stirring a solution in which lithium carbonate is added and dispersed in pure water so that the molar ratio of lithium to the total of the metal elements is 1.04: 1. A slurry containing Ni, Mn, and Co was prepared. Next, the slurry was spray-dried using a micro mist dryer having a three-fluid nozzle to obtain a powder containing Li, Ni, Mn, and Co. Next, using a roller hearth kiln, the powder was heated from room temperature to 900 ° C. over 1 hour, held for 2 hours, fired, and then cooled to 700 ° C. over 1 hour. After maintaining the time, it was cooled to room temperature over 3 hours. Next, the obtained fired product was pulverized using a roll mill and a pulverizer to obtain a Li-containing transition metal composite oxide powder E.

(Examples 32-33, Comparative Example 19, Reference Example 8)
A metal salt solution was prepared by dissolving nickel nitrate, cobalt nitrate, aluminum nitrate, and magnesium nitrate in pure water so that the molar ratios of Ni, Co, Al, and Mg atoms were 5: 3: 1: 1, respectively. Next, the metal salt solution is dropped while stirring a solution in which lithium carbonate is added and dispersed in pure water so that the molar ratio of lithium to the total of the metal elements is 1.04: 1. A slurry containing Ni, Co, Al, and Mg was prepared. Next, the slurry was spray-dried using a micro mist dryer having a three-fluid nozzle to obtain a powder containing Li, Ni, Co, Al, and Mg. Next, using a roller hearth kiln, the powder was heated from room temperature to 900 ° C. over 1 hour, held for 2 hours, fired, and then cooled to 700 ° C. over 1 hour. After maintaining the time, it was cooled to room temperature over 3 hours. Next, the obtained fired product was pulverized using a roll mill and a pulverizer to obtain a Li-containing transition metal composite oxide powder F.

-Preparation of inorganic ceramic powder-
In order to use in Examples, commercially available inorganic ceramic powder was appropriately pulverized by a jet mill to prepare a product having a predetermined particle size. The particle size was measured with a laser diffraction / scattering particle size distribution measuring device (Microtrack manufactured by Nikkiso Co., Ltd.), and the particle size with a volume cumulative frequency of 50% in the obtained particle size distribution curve was defined as the average particle size. Since Al ₂ O ₃ used in Comparative Example 3 had a particle size smaller than the measurement range of this machine, it was about 0.01 μm when observed with a scanning electron microscope.

-Preparation of small particle size Li-containing transition metal composite oxide-
For use in a comparative example, the Li-containing transition metal composite oxide powder pulverized by the pulverizer is further pulverized by a jet mill to produce a small-sized Li-containing transition metal composite oxide for addition in the comparative example. did.

(Evaluation)
-Evaluation of Li-containing transition metal composite oxide composition-
The metal content in each Li-containing transition metal composite oxide was measured with an inductively coupled plasma optical emission spectrometer (ICP-OES), and the composition of each metal was measured. The lithium content was measured by ion chromatography, and the oxygen content was measured by LECO.
Example 1 7,9～ 23, Comparative Examples 1 to 14, Reference Examples 1 to 3, the composition of the Li-containing transition metal composite oxide A used in 9 was _{Li 1.04 Ni 0.80 Mn 0.10 Co 0.10} O 2.15 .
The composition of the Li-containing transition metal composite oxide B used in Examples 24 to 25, Comparative Example 15, and Reference Example 4 was Li _1.02 Ni _0.80 Mn _0.20 O _2.12 .
The composition of the Li-containing transition metal composite oxide C used in Examples 26 to 27, Comparative Example 16, and Reference Example 5 was Li _1.00 Ni _0.80 Co _0.10 Al _0.10 O _2.04 .
The composition of the Li-containing transition metal composite oxide D used in Examples 28 to 29, Comparative Example 17, and Reference Example 6 was Li _1.04 Ni _0.80 Co _0.10 Mg _0.10 O _2.07 .
The composition of the Li-containing transition metal composite oxide E used in Examples 30 to 31, Comparative Example 18, and Reference Example 7 was Li _1.04 Ni _0.50 Mn _0.30 Co _0.20 O _2.12 .
The composition of the Li-containing transition metal composite oxide F used in Examples 32-33, Comparative Example 19, and Reference Example 8 was Li _1.04 Ni _0.50 Co _0.30 Al _0.10 Mg _0.10 O _2.16 .

-Evaluation of average particle size-
Laser diffraction / scattering type particle size distribution measuring device (larger particle size Li-containing transition metal composite oxide particle size distribution and smaller particle size Li-containing transition metal complex oxide particle size distribution (only for comparative examples)) Nikkiso Co., Ltd. Microtrac) measured, and the particle size distribution curve obtained in the particle size distribution curve, the particle size of the volume cumulative frequency 50% was taken as the average particle size.

-Production of positive electrode active material-
Add the above-mentioned inorganic ceramic powder (Examples and Comparative Examples) or the above-mentioned small particle size Li-containing transition metal composite oxide (Comparative Example) to the above-mentioned Li-containing transition metal composite oxide powder, By using and mixing, the positive electrode active material for lithium ion batteries was produced.

-Evaluation of battery characteristics-
Obtained by weighing 96 wt% of the positive electrode active material, 1.6 wt% of PVDF, and 2.4 wt% of carbon black and adding PVDF dissolved in N-methylpyrrolidone to a mixture of the positive electrode active material and carbon black. The slurry was applied on an Al foil, dried and pressed to obtain a positive electrode. A 2032 type coin cell for evaluation was produced using Li metal as a counter electrode and 1M-LiPF6 dissolved in EC-DMC (1: 1) in an electrolytic solution. In a constant temperature bath at 25 ° C., the charge / discharge voltage range is 3.0 V to 4.3 V, the charge is performed at 0.1 C in all cycles, the discharge is performed at 0.1 C in the first and 21st cycles, and others The cycle was performed at 1C. The discharge capacity at the second cycle 1C is divided by the discharge capacity at the first cycle 0.1C and the initial rate characteristic, and the discharge capacity at the 22nd cycle 1C is divided by the discharge capacity at the 21st cycle 0.1C and after 21 cycles. Rate characteristics were calculated.
These results are shown in Tables 1 and 2.

(Evaluation results)
Tables 1 and 2 are arranged according to the composition of the large-particle-size Li-containing transition metal composite oxide as a base. Reference Examples 1 to 8 are samples with only large particles as a base. The positive electrode active material generally has different characteristics depending on the composition. For example, although the capacity is higher when the amount of Ni is higher, the rate and the rate after elapse of the cycle are deteriorated.
When compared for each composition of the Li-containing transition metal composite oxide having a large particle size as a base, the rate after the cycle elapses without any change in the capacity of the first cycle due to the addition of ceramic particles. Recognize. In addition, when Li-containing transition metal composite oxide particles having the same composition and small particle diameter are added, the initial rate is slightly improved, but after the cycle, it is greatly deteriorated compared to the case where it is not added. Recognize.
Moreover, since Examples 1-7 , 9-33 , and Reference Example 9 all include Li-containing transition metal composite oxide and inorganic ceramics having an average particle diameter of 0.02-1 μm and 10-1000 wtppm, The battery characteristics were all good.
In addition, Comparative Examples 1 to 19 do not include inorganic ceramics as small particles, or include inorganic ceramics as small particles, but the average particle diameter is outside the range of 0.02 to 1 μm and 10 to 1000 wtppm. As a result, at least one of the battery characteristics was defective.

Claims (4)

Li-containing transition metal composite oxide, and
Including 10 to 1000 wtppm inorganic ceramics having an average particle size of 0.18 to 1 μm,
The Li-containing transition metal complex oxide has a composition formula: Li _{1 + x} Ni _1-y Me _y O _{2 + z}
(In the above formula, Me is one or more of Mn, Co, Al, and Mg, x is −0.1 to 0.1, y is the total composition of metals represented by Me, and 0 .1 to 0.5, and z is -0.1 to 0.2.)
In expressed,
The inorganic ceramic is an oxide, nitride, carbide, or a combination of one or more elements selected from Al, Si, Mg, Zr, Y;
The positive electrode active material for an average particle diameter of the lithium-ion battery Ru 4~12μm der of the Li-containing transition metal composite oxide. _2. The lithium ion battery according to claim 1 , wherein the inorganic ceramic is at least one selected from the group of Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , SiC, and YSZ (yttria stabilized zirconia). Positive electrode active material. The positive electrode for lithium ion batteries using the positive electrode active material for lithium ion batteries of Claim 1 or 2 . The lithium ion battery using the positive electrode for lithium ion batteries of Claim 3 .