Modified high-nickel ternary material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of positive electrode materials, and particularly relates to a modified high-nickel ternary material and a preparation method and application thereof. The invention provides a preparation method of a modified high-nickel ternary material, which comprises the following steps: mixing and sintering a high-nickel ternary material and a coating agent to obtain the modified high-nickel ternary material, the coating agent comprises ammonium phosphate and a bismuth compound; the molar ratio of phosphate ions in the ammonium phosphate to bismuth in the bismuth compound is (1.1-1.5): 1. The prepared modified high-nickel ternary material is large in specific capacity and good in cycling stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials, and in particular relates to a modified high-nickel ternary material and a preparation method and application thereof. Background Art

[0002] Ternary lithium-ion batteries have attracted widespread attention due to their high gram capacity and high charge and discharge efficiency. x Co y Mn (1-x-y) O2, x ≥ 0.8) has a higher gram capacity and lower cost; but as the nickel content gradually increases, the high-nickel ternary material also shows a decrease in cycle stability and thermal stability, and structural degradation occurs during the cycle, leading to performance degradation.

[0003] In the prior art, materials are coated on the outside of high-nickel ternary materials to reduce side reactions, but the steps are cumbersome, and the surface residual alkali of the high-nickel ternary materials after coating is high, and the cycle stability and thermal stability are poor. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of high-nickel ternary materials in the prior art, such as high residual alkali on the surface, poor cyclic stability and thermal stability, thereby providing a modified high-nickel ternary material and its preparation method and application.

[0005] To this end, the present invention provides the following technical solutions.

[0006] The present invention provides a method for preparing a modified high-nickel ternary material, comprising the following steps:

[0007] The high-nickel ternary material and the coating agent are mixed and sintered to obtain a modified high-nickel ternary material;

[0008] The coating agent includes ammonium phosphate and bismuth compound;

[0009] The molar ratio of the phosphate ion in the ammonium phosphate salt to the bismuth element in the bismuth compound is (1.1-1.5):1.

[0010] In an optional embodiment, the preparation step of the high-nickel ternary material includes: mixing a precursor, a lithium source and an additive, and heat treating to obtain the high-nickel ternary material;

[0011] The precursor includes Ni x Co y Mn 1-x-y (OH)2, 0.8≤x<1, 0<y≤0.1.

[0012] In an optional embodiment, the ammonium phosphate salt includes at least one of ammonium polyphosphate, ammonium phosphate, diammonium hydrogen phosphate and diammonium dihydrogen phosphate;

[0013] In an optional embodiment, the bismuth compound includes at least one of bismuth oxide and bismuth hydroxide.

[0014] In an optional embodiment, based on the mass of the high-nickel ternary material, the added amount of the coating agent is 0.05-0.7wt%.

[0015] In an optional embodiment, the sintering is performed in an oxygen atmosphere;

[0016] In an optional embodiment, the sintering temperature is 850-900°C;

[0017] In an optional embodiment, the heating rate of the sintering is 1.5-5°C / min;

[0018] In an optional embodiment, the sintering time is 3-7 hours.

[0019] In an optional embodiment, the lithium source includes lithium hydroxide;

[0020] In an optional embodiment, the additive includes at least one of tungsten oxide, aluminum oxide, zirconium oxide, niobium oxide, boron oxide and yttrium oxide.

[0021] In an optional embodiment, the ratio of the total molar amount of nickel, cobalt and manganese in the precursor to the molar amount of lithium in the lithium source is 1:(1.02-1.06);

[0022] In an optional embodiment, based on the mass of the precursor, the additive is added in an amount of 0.05-0.8 wt %.

[0023] In an optional embodiment, the heat treatment is performed under an oxygen atmosphere;

[0024] In an optional embodiment, the heat treatment temperature is 600-950°C;

[0025] In an optional embodiment, the heating rate of the heat treatment is 1-5°C / min;

[0026] In an optional embodiment, the heat treatment time is 8-15 hours.

[0027] The present invention also provides a modified high-nickel ternary material prepared by the above preparation method.

[0028] The present invention also provides an application of the modified high-nickel ternary material prepared by the above preparation method in a lithium ion battery.

[0029] The technical solution of the present invention has the following advantages:

[0030] 1. The preparation method of the modified high-nickel ternary material provided by the present invention comprises the following steps: mixing the high-nickel ternary material and the coating agent, sintering, and obtaining the modified high-nickel ternary material; the coating agent comprises ammonium phosphate and a bismuth compound; the molar ratio of phosphate ions in the ammonium phosphate and bismuth elements in the bismuth compound is (1.1-1.5): 1. The modified high-nickel ternary material prepared by the present invention has a large specific capacity and good cycle stability. The surface of the high-nickel ternary material is coated with bismuth phosphate and lithium phosphate. The bismuth phosphate is relatively stable due to the presence of a strong PO covalent bond, and also has good HF corrosion resistance, effectively inhibiting the interface side reaction between the high-nickel ternary material and the electrolyte, and improving the cycle stability of the high-nickel ternary material; the present invention limits the molar ratio of phosphate ions in the ammonium phosphate salt and the bismuth element in the bismuth compound to (1.1-1.5): 1, ensuring that the bismuth element in the bismuth compound can completely generate bismuth phosphate, and the remaining phosphate ions react with the residual lithium on the surface of the high-nickel ternary material to generate lithium phosphate, which can reduce the surface residual alkali, and inhibit the interface side reaction between the high-nickel ternary material and the electrolyte, and improve the cycle stability; lithium phosphate also has good ionic conductivity, which can improve the transmission rate of lithium ions. The preparation method provided by the present invention has simple steps.

[0031] 2. The preparation method of the modified high-nickel ternary material provided by the present invention adds additives when preparing the high-nickel ternary material, thereby enhancing the internal structural stability of the high-nickel ternary material, and the double coating layer of lithium phosphate and bismuth phosphate inhibits the side reaction at the interface between the high-nickel ternary material and the electrolyte; the two work together to effectively improve the cycle stability of the material. DETAILED DESCRIPTION

[0032] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0033] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0034] Example 1

[0035] This embodiment provides a method for preparing a ternary material double-coated with bismuth phosphate and lithium phosphate, comprising the following steps:

[0036] (1) Ni 0.8 Co 0.1Mn 0.1 The (OH)2 precursor, lithium hydroxide, zirconium oxide, yttrium oxide and tungsten oxide were mixed evenly in a high-speed mixer, heated to 750°C at 2.5°C / min in an oxygen atmosphere for 10 hours, and naturally cooled to room temperature to obtain a ternary material; wherein Ni 0.8 Co 0.1 Mn 0.1 The ratio of the total molar amount of nickel, cobalt and manganese in the (OH)2 precursor to the molar amount of lithium in lithium hydroxide is 1:1.04; Ni 0.8 Co 0.1 Mn 0.1 The mass ratio of (OH)2 precursor, zirconium oxide, yttrium oxide and tungsten oxide is 1:0.002:0.002:0.001.

[0037] (2) The ternary material, ammonium phosphate and bismuth trioxide are mixed evenly in a high-pressure mixer at a mass ratio of 1:0.0015:0.002, heated to 850°C at 2°C / min in an oxygen atmosphere, sintered for 4 hours, and naturally cooled to room temperature to obtain a ternary material double-coated with bismuth phosphate and lithium phosphate.

[0038] Example 2

[0039] This embodiment provides a method for preparing a ternary material double-coated with bismuth phosphate and lithium phosphate, comprising the following steps:

[0040] (1) Ni 0.9 Co 0.05 Mn 0.05 The (OH)2 precursor, lithium hydroxide, zirconium oxide, aluminum oxide, tungsten oxide and niobium oxide were mixed evenly in a high-speed mixer, heated to 700°C at 3.1°C / min in an oxygen atmosphere for 10 hours, and then cooled naturally to room temperature to obtain a ternary material; Ni 0.9 Co 0.05 Mn 0.05 The ratio of the total molar amount of nickel, cobalt and manganese in the (OH)2 precursor to the molar amount of lithium in lithium hydroxide is 1:1.04; Ni 0.9 Co 0.05 Mn 0.05 The mass ratio of (OH)2 precursor, zirconium oxide, aluminum oxide, tungsten oxide and niobium oxide is 1:0.002:0.002:0.001:0.001.

[0041] (2) The ternary material, diammonium hydrogen phosphate and bismuth hydroxide were mixed evenly in a high-pressure mixer at a mass ratio of 1:0.0026:0.004, heated to 880°C at 2°C / min in an oxygen atmosphere, sintered for 6 hours, and naturally cooled to room temperature to obtain a ternary material double-coated with bismuth phosphate and lithium phosphate.

[0042] Example 3

[0043] This embodiment provides a method for preparing a ternary material double-coated with bismuth phosphate and lithium phosphate, comprising the following steps:

[0044] (1) Ni 0.9 Co 0.05 Mn 0.05 The (OH)2 precursor, lithium hydroxide, boron oxide, aluminum oxide, tungsten oxide and niobium oxide were mixed evenly in a high-speed mixer, heated to 900°C at 5°C / min for 15h in an oxygen atmosphere, and naturally cooled to room temperature to obtain a ternary material; Ni 0.9 Co 0.05 Mn 0.05 The ratio of the total molar amount of nickel, cobalt and manganese in the (OH)2 precursor to the molar amount of lithium in lithium hydroxide is 1:1.06; 0.9 Co 0.05 Mn 0.05 The mass ratio of (OH)2 precursor, boron oxide, aluminum oxide, tungsten oxide and niobium oxide is 1:0.002:0.002:0.002:0.002.

[0045] (2) The ternary material, ammonium dihydrogen phosphate and bismuth trioxide are mixed evenly in a high-pressure mixer at a mass ratio of 1:0.00137:0.00187, the mixture is heated to 900°C at a rate of 5°C / min in an oxygen atmosphere, and the mixture is sintered for 7 h. The mixture is then naturally cooled to room temperature to obtain a ternary material double-coated with bismuth phosphate and lithium phosphate.

[0046] Comparative Example 1

[0047] This comparative example provides a method for preparing a ternary material. Compared with Example 1, the only difference is that step (2) is not performed.

[0048] Comparative Example 2

[0049] This comparative example provides a method for preparing a ternary material. Compared with Example 2, the only difference is that step (2) is not performed.

[0050] Comparative Example 3

[0051] This comparative example provides a method for preparing a ternary material. Compared with Example 1, the only difference is that step (2) is different. Step (2) is as follows:

[0052] The ternary material, ammonium phosphate and bismuth trioxide are uniformly mixed in a mass ratio of 1:0.00128:0.002, the temperature is increased to 850°C at 2°C / min in an oxygen atmosphere, and the mixture is sintered for 4 hours. The mixture is then naturally cooled to room temperature to obtain the ternary material.

[0053] Test Case

[0054] The performance tests of the ternary materials prepared in Examples 1-3 and Comparative Examples 1-3 were carried out as follows:

[0055] The ternary material, polyvinylidene fluoride (PVDF), and Super P (SP) were weighed and homogenized according to the mass ratio of 97.2:1.3:1.5, and then the aluminum foil was spread on the coating machine for coating (surface density of 15-17 mg / cm 2 ), put it into an 80℃ forced air drying oven and dry it for 2h; then punch, weigh, bake the electrode, and make it into a CR2032 button battery.

[0056] The performance test of the battery prepared above is as follows:

[0057] (1) Cycle performance test: The battery was placed in a blue-electric test system with a charging voltage of 3.0-4.3 V, a charge and discharge rate of 1 C, and a cycle number of 100. The results are shown in Table 1.

[0058] (2) Detection method of residual alkali: The residual alkali is detected by a potentiometric titrator. 5g of positive electrode material is added to 100ml of water to prepare a solution. An acidic solution is used as a titrant to neutralize the alkaline substance in the positive electrode material. The potential change is recorded at the same time. When the potential change reaches the preset end point potential, the titration ends. The residual alkali content in the positive electrode material is calculated by calculating the volume of the titrant consumed during the titration process. The results are shown in Table 1.

[0059] (3) Thermal stability test method: At 45°C, the battery was placed in a blue-electric test system with a charging voltage of 3.0-4.3 V, a charge and discharge rate of 1C, and a cycle number of 100. The results are shown in Table 1.

[0060] Table 1 Performance results of various embodiments and comparative examples

[0061]

[0062] It can be seen from Table 1 that after the modified high-nickel ternary material prepared by the preparation method provided by the present invention is used to make a battery, the cycle performance is good and the residual alkali is low. It can be seen from the capacity retention rate of the battery after 100 cycles at high temperature that the modified high-nickel ternary material prepared by the present invention has good thermal stability and structural stability.

[0063] It can be seen from Example 1 and Comparative Example 3 that when the molar ratio of phosphate ions in the ammonium phosphate salt to the bismuth element in the bismuth compound is 1:1 and not in the range of (1.1-1.5):1, the cycle performance deteriorates, the residual alkali increases, and the capacity retention rate after 100 cycles at high temperature decreases significantly.

[0064] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing a modified high-nickel ternary material, characterized in that: The steps include: The high-nickel ternary material and the coating agent are mixed and sintered to obtain a modified high-nickel ternary material; The coating agent includes ammonium phosphate and bismuth compound; The molar ratio of the phosphate ion in the ammonium phosphate salt to the bismuth element in the bismuth compound is (1.1-1.5):

1.

2. The preparation method according to claim 1, characterized in that: The preparation steps of the high-nickel ternary material include: mixing a precursor, a lithium source and an additive, and heat treating to obtain the high-nickel ternary material; The precursor includes Ni x Co y Mn 1-x-y (OH)2, 0.8≤x<1, 0<y≤0.

1.

3. The preparation method according to claim 1, characterized in that: The ammonium phosphate salt comprises at least one of ammonium polyphosphate, ammonium phosphate, diammonium hydrogen phosphate and diammonium dihydrogen phosphate; and / or, The bismuth compound includes at least one of bismuth oxide and bismuth hydroxide.

4. The preparation method according to claim 1, characterized in that: Based on the mass of the high-nickel ternary material, the added amount of the coating agent is 0.05-0.7wt%.

5. The preparation method according to claim 1, characterized in that: The sintering is carried out in an oxygen atmosphere; and / or, The sintering temperature is 850-900° C.; and / or, The heating rate of the sintering is 1.5-5°C / min; and / or, The sintering time is 3-7h.

6. The preparation method according to claim 2, characterized in that: The lithium source comprises lithium hydroxide; and / or, The additive includes at least one of tungsten oxide, aluminum oxide, zirconium oxide, niobium oxide, boron oxide and yttrium oxide.

7. The preparation method according to claim 6, characterized in that: The ratio of the total molar amount of nickel, cobalt and manganese in the precursor to the molar amount of lithium in the lithium source is 1:(1.02-1.06); and / or, Based on the mass of the precursor, the amount of the additive added is 0.05-0.8wt%.

8. The preparation method according to claim 7, characterized in that: The heat treatment is carried out in an oxygen atmosphere; and / or, The heat treatment temperature is 600-950°C; and / or, The heating rate of the heat treatment is 1-5°C / min; and / or, The heat treatment time is 8-15h.

9. The modified high-nickel ternary material obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the modified high-nickel ternary material prepared by the preparation method according to any one of claims 1 to 8 in lithium-ion batteries.

Images