A high-voltage lithium cobalt oxide battery positive electrode material and preparation method thereof

Abstract

The present invention provides a high-voltage lithium cobalt oxide battery positive electrode material, which comprises lithium cobalt oxide as a core and a coating layer covering the surface of the lithium cobalt oxide, wherein the coating layer comprises at least two of tungsten oxide, titanium oxide and aluminum oxide and contains tungsten oxide. The content of tungsten in the lithium cobalt oxide battery positive electrode material is 1000ppm~2000ppm, and the lithium cobalt oxide as the core is doped with doping elements, wherein the doping elements comprise at least two of aluminum, magnesium, strontium and titanium. The lithium cobalt oxide battery positive electrode material of the present invention has a stable structure and effectively improves the cycle stability of the lithium cobalt oxide positive electrode material under high voltage. The material has excellent capacity, rate and high-temperature cycle performance under high voltage conditions of 3.0-4.45V. It also improves the battery performance of the lithium cobalt oxide battery positive electrode material used in high-temperature environments. It has great application prospects in lithium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and in particular to a high-voltage lithium cobalt oxide battery positive electrode material and a preparation method thereof. Background Art

[0002] Lithium cobalt oxide (LiCoO2) is the earliest commercialized positive electrode material for lithium-ion batteries. Due to its high material density and electrode compaction density, lithium-ion batteries using lithium cobalt oxide positive electrodes have high volume energy density. Therefore, lithium cobalt oxide is a widely used positive electrode material in lithium-ion batteries. As consumer electronics products have increasing requirements for the battery life of lithium-ion batteries, there is an urgent need to further improve the volume energy density of batteries. Increasing the charging voltage of lithium cobalt oxide batteries can increase the battery's gram capacity and volume energy density. Therefore, the development of the next generation of lithium cobalt oxide materials with higher charging voltages has become a hot topic of common concern in the scientific research community and enterprises. At present, the charging cut-off voltage of lithium cobalt oxide batteries has gradually increased from 4.20V when it was first commercialized in 1991 to 4.45V (vs Li / Li + ), the volume energy density has exceeded 700Wh / L.

[0003] The invention patent 202011054318.X discloses a lithium cobalt oxide and its preparation method and application. The preparation method of the lithium cobalt oxide comprises: subjecting cobalt metal element and / or cobalt metal oxide, dopant, oxidant, water, conductive metal salt and optional ammonia solution to chemical corrosion crystallization reaction under the conditions of redox potential ORP value ≤ 100mv, complexing agent concentration of 0.1-20g / L, and conductivity ≥ 100uS / cm, followed by magnetic separation, aging alkali washing, solid-liquid separation, washing and drying, and lithiation. The method provided by the present invention is used to prepare lithium cobalt oxide. The dissolution and crystallization process does not produce wastewater and continuously consumes water, thereby achieving the purpose of being environmentally friendly. In addition, the lithium cobalt oxide obtained as the positive electrode material for the corresponding lithium-ion battery also has high gram capacity and excellent cycle stability, and has great industrial application prospects.

[0004] However, battery materials are often used in harsh environments, and the performance of existing lithium cobalt oxide battery positive electrode materials in such harsh environments needs to be improved. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a high-voltage lithium cobalt oxide battery positive electrode material and a preparation method thereof.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is: a high-voltage lithium cobalt oxide battery positive electrode material, wherein the lithium cobalt oxide battery positive electrode material comprises lithium cobalt oxide as a core and a coating layer covering the surface of the lithium cobalt oxide, the coating layer comprises at least two of tungsten oxide, titanium oxide, and aluminum oxide and contains tungsten oxide, the tungsten content in the lithium cobalt oxide battery positive electrode material is 1000ppm~2000ppm, and the lithium cobalt oxide as the core is doped with doping elements, and the doping elements include at least two of aluminum, magnesium, strontium and titanium.

[0007] The above-mentioned high-voltage lithium cobalt oxide battery positive electrode material has a core and coating structure, with lithium cobalt oxide as the core and doping elements including aluminum, magnesium, strontium and titanium. At the same time, the coating contains tungsten oxide material, and is matched with aluminum oxide or titanium oxide as a coating layer. The material in the coating layer interacts with the doping elements and lithium cobalt oxide material. After high-temperature sintering, the doping elements and the coating layer material are evenly distributed and structurally stable, effectively improving the cycle stability of the lithium cobalt oxide positive electrode material under high voltage. The material has excellent capacity, rate and high-temperature cycle performance under high voltage conditions of 3.0-4.45V. It also improves the battery performance of lithium cobalt oxide battery positive electrode materials used in high-temperature environments. It has great application prospects in lithium-ion batteries.

[0008] Preferably, the coating layer comprises tungsten oxide and titanium oxide.

[0009] The above-mentioned high-voltage lithium cobalt oxide battery positive electrode material has better capacity, rate, and high-temperature cycle performance, and the battery performance used in high-temperature environments is also improved.

[0010] Preferably, the coating layer is tungsten oxide, titanium oxide and aluminum oxide.

[0011] Preferably, the lithium cobalt oxide serving as the core is doped with at least two of aluminum, magnesium, strontium and titanium and contains strontium and titanium.

[0012] The above-mentioned high-voltage lithium cobalt oxide battery positive electrode material has better capacity, rate, and high-temperature cycle performance, and the battery performance used in high-temperature environments is also improved.

[0013] Preferably, the total content of the doping elements in the high-voltage lithium cobalt oxide battery positive electrode material is 2000ppm to 4000ppm.

[0014] Preferably, the doping elements include aluminum, magnesium, strontium and titanium.

[0015] The above-mentioned high-voltage lithium cobalt oxide battery positive electrode material has better capacity, rate, and high-temperature cycle performance, and the battery performance used in high-temperature environments is also improved.

[0016] Preferably, the total metal elements in the coating layer material account for 2000 to 3500 ppm by weight of the high-voltage lithium cobalt oxide battery positive electrode material.

[0017] Preferably, the Dv50 of the high-voltage lithium cobalt oxide battery positive electrode material is 14 to 17 μm.

[0018] Preferably, the content of tungsten in the positive electrode material of the lithium cobalt oxide battery is 1300ppm to 1800ppm.

[0019] The above-mentioned high-voltage lithium cobalt oxide battery positive electrode material has better capacity, rate, and high-temperature cycle performance, and the battery performance used in high-temperature environments is also improved.

[0020] The present invention also provides a method for preparing any of the above-mentioned high-voltage lithium cobalt oxide battery positive electrode materials, the preparation method comprising the following steps:

[0021] (1) uniformly mixing a cobalt source, a doping element source, and a lithium source, heating the mixture to 900-950° C. in an oxygen-containing gas atmosphere and sintering the mixture for 9-14 hours to obtain a first sintered material having a Dv50 particle size of 1-8 μm;

[0022] (2) uniformly mixing the cobalt source, the doping element source, and the lithium source, heating the mixture to 980-1050° C. in an oxygen-containing gas atmosphere, and sintering the mixture for 9-14 hours to obtain a second sintered material having a Dv50 particle size of 20-23 μm;

[0023] (3) The second sintered material and the first sintered material are mixed in a weight ratio of (1.5-5):1, and then mixed evenly with the coating layer source material, and sintered at 780-880°C for 8-13 hours in an oxygen-containing gas atmosphere to obtain the high-voltage lithium cobalt oxide battery positive electrode material.

[0024] Preferably, the cobalt source is cobalt trioxide, the lithium source is lithium carbonate, the doping element source is an oxide or hydroxide of the corresponding element, and the coating layer source material is an oxide or hydroxide of the corresponding element.

[0025] The beneficial effects of the present invention are as follows: the present invention provides a high-voltage lithium cobalt oxide battery positive electrode material and a preparation method thereof. The high-voltage lithium cobalt oxide battery positive electrode material of the present invention has a core and a coating layer structure, wherein lithium cobalt oxide serves as the core and the doping elements include aluminum, magnesium, strontium and titanium. At the same time, the coating layer includes a tungsten oxide material and is matched with aluminum oxide or titanium oxide. The material in the coating layer interacts with the doping elements and the lithium cobalt oxide material. After high-temperature sintering, the doping elements and the coating layer material are evenly distributed and structurally stable, effectively improving the cycle stability of the lithium cobalt oxide positive electrode material under high voltage. The material has excellent capacity, rate and high-temperature cycle performance under high voltage conditions of 3.0-4.45V. It also improves the battery performance of the lithium cobalt oxide battery positive electrode material used in high-temperature environments. It has great application prospects in lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an SEM image of the high-voltage lithium cobalt oxide battery positive electrode material according to an embodiment of the present invention.

[0027] Figure 2 This is a high-temperature battery performance cycle diagram of the high-voltage lithium cobalt oxide battery positive electrode material according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0029] Example 1

[0030] As an embodiment of the present invention, a high-voltage lithium cobalt oxide battery positive electrode material is provided. The lithium cobalt oxide battery positive electrode material comprises lithium cobalt oxide as a core and a coating layer covering the surface of the lithium cobalt oxide. The coating layer is tungsten oxide and titanium oxide. The lithium cobalt oxide as the core is doped with doping elements, and the doping elements include strontium and titanium.

[0031] Lithium cobalt oxide satisfies the chemical formula Li y Co (1-x) M x O2, wherein 0<x≤0.5, y=1, that is, lithium and oxygen are prepared in a molar ratio of 1:2, and M1 is Ti and Sr.

[0032] According to ICP-MS testing, the content of tungsten in the positive electrode material of lithium cobalt oxide battery is 1586.7ppm; the content of titanium in the coating layer of the positive electrode material of lithium cobalt oxide battery is 987.6ppm;

[0033] According to ICP-MS detection, the total content of doping elements in the high-voltage lithium cobalt oxide battery positive electrode material is 3004.9 ppm, the content of strontium is 1508.4 ppm, and the content of titanium is 1496.5 ppm;

[0034] The Dv50 of the high-voltage lithium cobalt oxide battery positive electrode material is 16.82 μm.

[0035] The method for preparing the positive electrode material of a high-voltage lithium cobalt oxide battery in this embodiment includes the following steps:

[0036] (1) uniformly mixing a cobalt source, a doping element source, and a lithium source, heating the mixture to 940° C. in an oxygen-containing gas atmosphere and sintering the mixture for 10 hours to obtain a first sintered material having a Dv50 particle size of 5.08 μm;

[0037] (2) uniformly mixing the cobalt source, the doping element source, and the lithium source, heating the mixture to 1000° C. in an oxygen-containing gas atmosphere and sintering the mixture for 10 hours to obtain a second sintered material having a Dv50 particle size of 20.55 μm;

[0038] (3) The second sintered material and the first sintered material are mixed in a weight ratio of 4.5:1, and then mixed evenly with the coating layer source material, and sintered at 850° C. for 10 hours in an oxygen-containing gas atmosphere to obtain the high-voltage lithium cobalt oxide battery positive electrode material.

[0039] In the preparation method, the cobalt source is cobalt tetroxide, the lithium source is lithium carbonate, the doping element source is the oxide of the corresponding element, and the coating layer source material is the oxide of the corresponding element.

[0040] Element content detection

[0041] 1. Weigh 0.1 g of the high-voltage lithium cobalt oxide battery cathode material prepared in this example to the nearest 0.01 and record the actual mass. Add 5 mL of 35% hydrochloric acid solution and microwave digest in a polytetrafluoroethylene microwave digestion vessel. After the liquid cools, transfer the amount to a 20 mL volumetric flask.

[0042] Establish ICP-MS standard curves for strontium, tungsten, titanium, aluminum, and magnesium.

[0043] The solution after microwave digestion was diluted in a gradient manner, and the dilution multiple was recorded. The diluted solution was detected by ICP-MS to quantify the tungsten content in the solution. The tungsten content in the positive electrode material of the high-voltage lithium cobalt oxide battery was calculated based on the mass of the positive electrode material of the ion battery, the quantification to 20 mL, and the gradient dilution multiple.

[0044] 2. Since the doping element contains Ti and the coating layer also contains titanium, the above-mentioned method for measuring ICP-MS cannot clearly determine the content of Ti in the material.

[0045] Therefore, for the detection of the content of the Ti element in this embodiment, including the elements in all embodiments in which the doping elements overlap with the coating layer elements, the above method is referred to, and the first sintered material obtained in step (1) is digested with hydrochloric acid to determine the content of the doping element in the first sintered material. Then, based on the yield mass ratio of the first sintered material and the final high-voltage lithium cobalt oxide battery positive electrode material, the content of the doping element in the high-voltage lithium cobalt oxide battery positive electrode material is calculated.

[0046] Then, by directly measuring the total Ti content in the high-voltage lithium cobalt oxide battery positive electrode material and deducting the doping element Ti content, the titanium content in the coating layer can be calculated.

[0047] Example 2

[0048] As a high-voltage lithium cobalt oxide battery positive electrode material in an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the coating layer is tungsten oxide and aluminum oxide.

[0049] According to ICP-MS detection, the content of tungsten in the positive electrode material of lithium cobalt oxide battery is 1588.3ppm, and the content of Al in the coating layer of the positive electrode material of lithium cobalt oxide battery accounts for 993.4ppm of the positive electrode material of lithium cobalt oxide battery.

[0050] Example 3

[0051] As a high-voltage lithium cobalt oxide battery positive electrode material according to an embodiment of the present invention, the only difference between this embodiment and embodiment 1 is that the doping elements include strontium, titanium, and magnesium, that is, during the sintering step (2), the ratio of the first sintering material and the coating layer source doping material is exactly the same.

[0052] According to ICP-MS detection, the content of doping elements in the high-voltage lithium cobalt oxide battery positive electrode material is 1003.8 ppm of strontium, 999.3 ppm of Ti, and 998.4 ppm of Mg.

[0053] Example 4

[0054] As a high-voltage lithium cobalt oxide battery positive electrode material according to an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the doping elements include strontium, titanium, and aluminum, that is, during the sintering step (2), the ratio of the first sintering material and the coating layer source doping material is exactly the same.

[0055] According to ICP-MS detection, the content of doping elements in the high-voltage lithium cobalt oxide battery positive electrode material is 997.6 ppm of strontium, 996.2 ppm of Ti, and 1002.4 ppm of Al.

[0056] Example 5

[0057] As a high-voltage lithium cobalt oxide battery positive electrode material according to an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the doping elements include strontium, titanium, aluminum, and magnesium, that is, during the sintering step (2), the ratio of the first sintering material and the coating layer source doping material is exactly the same.

[0058] According to ICP-MS detection, the content of doping elements in the high-voltage lithium cobalt oxide battery positive electrode material is 746.7 ppm of strontium, 752.1 ppm of Ti, 755.6 ppm of Al, and 748.4 ppm of magnesium.

[0059] Example 6

[0060] As a high-voltage lithium cobalt oxide battery positive electrode material in an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the content of tungsten oxide in the coating layer is adjusted.

[0061] According to ICP-MS detection, the content of tungsten in the positive electrode material of lithium cobalt oxide battery is 1056.4ppm; the content of titanium in the coating layer of the positive electrode material of lithium cobalt oxide battery accounts for 989.3ppm of the positive electrode material of lithium cobalt oxide battery.

[0062] Example 7

[0063] As a high-voltage lithium cobalt oxide battery positive electrode material in an embodiment of the present invention, the only difference between this embodiment and Example 1 is that the content of tungsten oxide in the coating layer is adjusted.

[0064] According to ICP-MS detection, the content of tungsten in the positive electrode material of lithium cobalt oxide battery is 1896.4ppm; the content of titanium in the coating layer of the positive electrode material of lithium cobalt oxide battery accounts for 991.2ppm of the positive electrode material of lithium cobalt oxide battery.

[0065] Comparative Example 1

[0066] As a comparative example of the present invention, a high-voltage lithium cobalt oxide battery positive electrode material is used. The only difference between this comparative example and Example 1 is that the coating layer is tungsten oxide, and the total amount of tungsten oxide in the coating layer of this comparative example is equal to the total amount of tungsten oxide and titanium oxide in the coating layer of Example 1 (the total amount of raw materials sintered in step (2) is controlled to be equal).

[0067] Comparative Example 2

[0068] As a comparative example of the present invention, a high-voltage lithium cobalt oxide battery positive electrode material is used. The only difference between this comparative example and Example 1 is that the coating layer is titanium oxide, and the total amount of titanium oxide in the coating layer of this comparative example is equal to the total amount of tungsten oxide and titanium oxide in the coating layer of Example 1 (the total amount of raw materials sintered in step (2) is controlled to be equal).

[0069] Comparative Example 3

[0070] As a comparative example of the present invention, a high-voltage lithium cobalt oxide battery positive electrode material is used. The only difference between this comparative example and Example 1 is that the coating layer is aluminum oxide, and the total amount of aluminum oxide in the coating layer of this comparative example is equal to the total amount of tungsten oxide and titanium oxide in the coating layer of Example 1 (the total amount of raw materials sintered in step (2) is controlled to be equal).

[0071] Comparative Example 4

[0072] As a comparative example of the present invention, a high-voltage lithium cobalt oxide battery positive electrode material is used. The only difference between this comparative example and Example 1 is that the preparation method is different.

[0073] The preparation method of the positive electrode material of the high-voltage lithium cobalt oxide battery comprises the following steps:

[0074] (1) The cobalt source, the doping element source, and the lithium source were uniformly mixed, and the mixture was heated to 940° C. in an oxygen-containing gas atmosphere and sintered for 10 hours to obtain a first sintered material having a Dv50 particle size of 5.08 μm; (the first sintered material of this comparative example was prepared in the same batch as the first sintered material of Example 1)

[0075] (2) The first sintered material is uniformly mixed with the coating layer source material according to a weight ratio, and sintered at 850° C. for 10 hours in an oxygen-containing gas atmosphere to obtain the high-voltage lithium cobalt oxide battery positive electrode material; the amount of the first sintered material in this step is the sum of the amounts of the first sintered material and the second sintered material in Example 1.

[0076] Comparative Example 5

[0077] As a comparative example of the present invention, a high-voltage lithium cobalt oxide battery positive electrode material is used. The only difference between this comparative example and Example 1 is that the preparation method is different.

[0078] (1) The cobalt source, the doping element source, and the lithium source were uniformly mixed, and the mixture was heated to 1000° C. in an oxygen-containing gas atmosphere and sintered for 10 hours to obtain a second sintered material having a Dv50 particle size of 20.55 μm; (the second sintered material of this comparative example was prepared in the same batch as the second sintered material of Example 1)

[0079] (2) The second sintered material and the coating layer source material are mixed evenly, and sintered at 850° C. for 10 hours in an oxygen-containing gas atmosphere to obtain the high-voltage lithium cobalt oxide battery positive electrode material. The amount of the second sintered material in this step is the sum of the amounts of the first sintered material and the second sintered material in Example 1.

[0080] 1. Experimental Methods

[0081] 1. Material characterization and performance testing

[0082] 2. Performance Testing

[0083] Battery performance testing of battery materials

[0084] The battery material test conditions for the examples and comparative examples are as follows:

[0085] (1) The lithium cobalt oxide positive electrode material obtained in Examples 1-7 and Comparative Examples 1-5 was uniformly mixed with acetylene black (Super P), a conductive agent, and polyvinylidene fluoride (PVDF) in a mass ratio of 9:0.5:0.5. The mixture was adjusted into a slurry with N-methyl-pyrrolidone (NMP), and then evenly applied on aluminum foil. After vacuum drying, the pressed sheet was taken out and cut into a positive electrode sheet of the required size;

[0086] (2) Preparation of lithium-ion half-cell: The lithium-ion battery is assembled from the above-mentioned positive electrode sheet, lithium negative electrode, separator between the positive and negative electrodes and electrolyte. Charge and discharge system: voltage range 3.0-4.45V; tested at room temperature 25℃, 0.2C discharge capacity / mAh / g, rate performance 1C, 4C, 1C / 1C charge and discharge cycle capacity retention rate for 50 weeks at high temperature of 60℃.

[0087] Table 1 Performance of high voltage lithium cobalt oxide battery cathode materials

[0088]

[0089]

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high voltage lithium cobalt oxide battery positive electrode material, characterized in that: The lithium cobalt oxide battery positive electrode material comprises lithium cobalt oxide as a core and a coating layer covering the surface of the lithium cobalt oxide, and the lithium cobalt oxide satisfies the chemical formula Li y Co (1-x) M x O2, wherein 0<x≤0.5, y=1, the coating layer comprises tungsten oxide and titanium oxide, the content of tungsten in the positive electrode material of the lithium cobalt oxide battery is 1000ppm~2000ppm, and the lithium cobalt oxide as the core is doped with doping elements, and the doping elements are strontium and titanium; The method for preparing the high-voltage lithium cobalt oxide battery positive electrode material comprises the following steps: (1) uniformly mixing a cobalt source, a doping element source, and a lithium source, heating the mixture to 900-950° C. in an oxygen-containing gas atmosphere and sintering the mixture for 9-14 hours to obtain a first sintered material having a Dv50 particle size of 1-8 μm; (2) uniformly mixing the cobalt source, the doping element source, and the lithium source, heating the mixture to 980-1050° C. in an oxygen-containing gas atmosphere and sintering the mixture for 9-14 hours to obtain a second sintered material having a Dv50 particle size of 20-23 μm; (3) The second sintered material and the first sintered material are mixed in a weight ratio of (1.5-5):1, and then mixed evenly with the coating layer source material, and sintered at 780-880°C for 8-13 hours in an oxygen-containing gas atmosphere to obtain the high-voltage lithium cobalt oxide battery positive electrode material.

2. The high-voltage lithium cobalt oxide battery positive electrode material according to claim 1, characterized in that: The coating layer is tungsten oxide, titanium oxide and aluminum oxide.

3. The high-voltage lithium cobalt oxide battery positive electrode material according to claim 1, characterized in that: The total content of the doping elements in the high-voltage lithium cobalt oxide battery positive electrode material is 2000ppm~4000ppm, and the Dv50 of the high-voltage lithium cobalt oxide battery positive electrode material is 14~17μm.

4. The high-voltage lithium cobalt oxide battery positive electrode material according to claim 1, characterized in that: The total metal elements in the coating layer material account for 2000-3500 ppm of the weight of the high-voltage lithium cobalt oxide battery positive electrode material.

5. The high-voltage lithium cobalt oxide battery positive electrode material according to claim 1, characterized in that: The content of tungsten in the positive electrode material of the lithium cobalt oxide battery is 1300ppm~1800ppm.

6. The method for preparing a high-voltage lithium cobalt oxide battery positive electrode material according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) uniformly mixing a cobalt source, a doping element source, and a lithium source, heating the mixture to 900-950° C. in an oxygen-containing gas atmosphere and sintering the mixture for 9-14 hours to obtain a first sintered material having a Dv50 particle size of 1-8 μm; (2) uniformly mixing the cobalt source, the doping element source, and the lithium source, heating the mixture to 980-1050° C. in an oxygen-containing gas atmosphere and sintering the mixture for 9-14 hours to obtain a second sintered material having a Dv50 particle size of 20-23 μm; (3) The second sintered material and the first sintered material are mixed in a weight ratio of (1.5-5):1, and then mixed evenly with the coating layer source material, and sintered at 780-880°C for 8-13 hours in an oxygen-containing gas atmosphere to obtain the high-voltage lithium cobalt oxide battery positive electrode material.

7. The method for preparing a high-voltage lithium cobalt oxide battery positive electrode material according to claim 6, characterized in that: The cobalt source is cobalt trioxide, the lithium source is lithium carbonate, the doping element source is the oxide or hydroxide of the corresponding element, and the coating layer source material is the oxide or hydroxide of the corresponding element.

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