A modified ternary lithium electrode material, a preparation method and application thereof

Abstract

This invention belongs to the field of lithium-ion battery technology, specifically relating to a modified ternary lithium electrode material, its preparation method, and its application. The preparation method provided by this invention includes: 1) mixing a nickel-containing precursor and a first lithium source, followed by calcination to obtain a nickel-containing cathode material; 2) mixing a second lithium source, a tungsten source, and an organic solvent under a first stirring to form a mixed solution, spraying the mixed solution onto the nickel-containing cathode material obtained in step 1) using a spray method, followed by a second stirring and sintering to obtain a one-coated ternary cathode material; 3) depositing an organic tungsten source precursor and water onto the surface of the one-coated ternary cathode material obtained in step 2) using atomic layer deposition to obtain the modified ternary lithium electrode material. The modified ternary lithium electrode material prepared by the specific preparation method of this invention can suppress surface degradation and structural instability, exhibiting good cycle performance and first-cycle efficiency in lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a modified ternary lithium electrode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles, the market demand for high-performance lithium-ion batteries has been greatly promoted and stimulated. As the energy density requirements for lithium-ion batteries continue to increase, the market demand for ternary lithium-ion battery materials has maintained an upward trend. Cathode materials play a crucial role in determining electrochemical performance. Due to their advantages such as low cost, environmental friendliness, and reversible capacity, ternary cathode materials are considered one of the ideal candidate materials for current and future power batteries. Whether from a policy perspective, market demand, or technological evolution direction, ternary materials have become an inevitable trend in the development of power lithium-ion battery materials.

[0003] However, lithium-ion batteries exhibit significant capacity decay and poor rate performance during cycling. In recent years, researchers have discovered that doping and coating processes can improve capacity decay and rate performance during cycling. However, conventional surface coatings increase the interfacial resistance of the cathode material, still causing irreversible capacity loss. Therefore, the cycle stability of lithium-ion batteries remains to be improved. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the cycle stability of existing lithium-ion batteries still needs to be improved during the cycle process, thereby providing a modified ternary lithium electrode material, its preparation method and application.

[0005] This invention provides a method for preparing a modified ternary lithium electrode material, comprising the following steps: 1) The nickel-containing precursor and the first lithium source are mixed and calcined to obtain a nickel-containing cathode material; 2) The second lithium source, tungsten source and organic solvent are mixed by first stirring to form a mixed solution. The mixed solution is sprayed onto the nickel-containing cathode material obtained in step 1) by spraying. Then, it is mixed by second stirring and sintered to obtain a one-time coated ternary cathode material. 3) The organic tungsten source precursor and water are deposited on the surface of the ternary cathode material obtained in step 2) by atomic layer deposition to obtain the modified ternary lithium electrode material.

[0006] Preferably, the general chemical formula of the nickel-containing precursor in step 1) is Ni x Co y Mn z (OH)2, where x+y+z=1.

[0007] The ratio of the total molar amount of metal elements in the nickel-containing precursor to the molar amount of lithium source in the first lithium source is 1:(0.9-1.02).

[0008] Preferably, the calcination temperature in step 1) is 650-750℃, and the calcination time is 7-11h; The first lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium acetate, and lithium oxalate.

[0009] Preferably, in step 2), the second lithium source is selected from at least one of lithium acetate, lithium hydroxide, lithium carbonate, and lithium oxalate; The tungsten source is selected from ethanol tungsten; The ratio of the molar amount of lithium in the second lithium source to the molar amount of tungsten in the tungsten source is (0.01-0.5):(0.5-2). The mass concentration of the second lithium source in the mixed solution is 8-15 wt%.

[0010] Preferably, the spraying rate of the mixed solution onto the positive electrode material in step 2) is 0.5-1 mL / min; In step 2), the second stirring speed is 100-400 rpm and the second stirring time is 10-30 min.

[0011] The present invention does not impose specific limitations on the stirring speed and time of the first stirring and mixing, as long as the purpose of uniform mixing is achieved.

[0012] Optionally, the first stirring temperature is 60-90℃, the first stirring time is 5-8h, and the first stirring speed is 400-600rpm.

[0013] Preferably, the sintering in step 2) includes a first sintering and a second sintering; Optionally, the first sintering temperature is 250-450℃, and the first sintering time is 1-3h; The second sintering temperature is 400-700℃, and the second sintering time is 3-7h; The atmosphere for the second sintering is an inert atmosphere; Optionally, the inert atmosphere is selected from nitrogen atmosphere.

[0014] Optionally, the atmosphere for the first sintering is oxygen. The first sintering is also known as pre-sintering.

[0015] Preferably, in step 2), the mass of tungsten in the mixed solution accounts for 800-1200 ppm of the mass content of the nickel-containing cathode material; And / or, in step 3), an organic tungsten source precursor and water are sequentially deposited on the surface of the ternary cathode material obtained in step 2), and then the process of sequentially depositing the organic tungsten source precursor and water is repeated. After the repeated process is completed, annealing is performed to obtain the modified ternary lithium electrode material.

[0016] Preferably, the organic tungsten source precursor in step 3) is selected from bis(tert-butylimino)bis(dimethylamino)tungsten; The deposition temperature is 50-100℃; When the organic tungsten source precursor and water are deposited sequentially, the deposition time of the organic tungsten source precursor is 1-5s, and the deposition time of the water is 1-5s. After the deposition of the tungsten source precursor is completed, inert gas purging is also performed to remove excess tungsten source precursor. Optionally, the treatment step of repeatedly depositing the organic tungsten source precursor and water is repeated 1-50 times. Optionally, the annealing temperature is 400-700℃, and the annealing time is 3-7h; The average thickness of the deposited layer is 1%-1.5% of the D50 particle size of the ternary cathode material coated in the first stage.

[0017] This invention provides a modified ternary lithium electrode material, which is prepared by the above-described method for preparing modified ternary lithium electrode materials.

[0018] The present invention also provides an application of the modified ternary lithium electrode material described above in lithium-ion batteries.

[0019] The technical solution of this invention has the following advantages: The present invention provides a method for preparing modified ternary lithium electrode materials, comprising the following steps: 1) mixing a nickel-containing precursor and a first lithium source, calcining to obtain a nickel-containing cathode material; 2) mixing a second lithium source, a tungsten source, and an organic solvent by a first stirring to form a mixed solution, spraying the mixed solution onto the nickel-containing cathode material obtained in step 1) by a spray method, then mixing by a second stirring and sintering to obtain a one-time coated ternary cathode material; 3) depositing an organic tungsten source precursor and water onto the surface of the one-time coated ternary cathode material obtained in step 2) by atomic layer deposition to obtain the modified ternary lithium electrode material. The present invention provides a method for one-time coating of nickel-containing cathode materials using a wet process with a second lithium source and a tungsten source. The wet coating technology does not form island-like aggregations and can more uniformly coat the cathode material. The Li2WO4 formed on the surface of the one-time coated ternary cathode material serves as the coating layer. Li2WO4 has strong ionic conductivity and high mechanical strength, which is beneficial for enhancing the cycle performance of the nickel-containing cathode material by adjusting the interfacial reaction. Then, atomic layer deposition is used to perform a secondary deposition on the surface of the ternary cathode material after primary coating. This further compensates for the structural defects in the primary coating process of the cathode material using wet methods, achieving a uniform coating effect. This reduces the damage to the cathode material from the organic electrolyte during cycling, thereby further improving cycle performance. The modified ternary lithium electrode material prepared by the specific method of this invention can suppress surface degradation and structural instability, exhibiting excellent cycle performance and first-time efficiency when applied in lithium-ion batteries. Detailed Implementation

[0020] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0021] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0022] Example 1 This embodiment provides a method for preparing a modified ternary lithium electrode material, including the following steps: 1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ nickel-rich precursor and LiOH are mixed, Ni 0.8 Co 0.1 Mn 0.1The ratio of the total molar amount of Ni, Co, and Mn in the nickel-rich (OH)2 precursor to the molar amount of Li in LiOH is 1:1.02. The precursor is heated to 650℃ at a heating rate of 1℃ / min and calcined for 7h to obtain a nickel-containing cathode material. 2) Lithium acetate, tungsten ethoxide, and ethanol were stirred at 80°C and 500 rpm for 6 hours to form a mixed solution. The molar ratio of lithium in lithium acetate to tungsten in tungsten ethoxide was 0.5:1, and the mass concentration of lithium acetate in the mixed solution was 10 wt%. The mixed solution was sprayed at 0.5 mL / min onto 500 g of nickel-containing cathode material obtained in step 1) by spraying (the mass of tungsten in the sprayed mixed solution accounted for 1000 ppm of the mass content of nickel-containing cathode material). The mixture was then stirred at 300 rpm for 30 minutes. The mixture was then sintered at 350°C for 1 hour under an oxygen atmosphere, and then sintered at 500°C for 5 hours under a nitrogen atmosphere to obtain the one-time coated ternary cathode material. 3) The primary coated ternary cathode material obtained in step 2) is subjected to deposition treatment at 70°C under vacuum conditions, including sequentially depositing bis(tert-butylimino)bis(dimethylamino)tungsten on the surface of the primary coated ternary cathode material obtained in step 2), removing excess bis(tert-butylimino)bis(dimethylamino)tungsten by nitrogen purging, and then depositing water. The deposition time of bis(tert-butylimino)bis(dimethylamino)tungsten is 3s, and the deposition time of water is 3s. The above deposition treatment steps are repeated 20 times. The deposition layer is formed by annealing at 550°C for 5h. The average thickness of the deposition layer accounts for 1.3% of the D50 particle size of the primary coated ternary cathode material, thus obtaining the modified ternary lithium electrode material.

[0023] Example 2 This embodiment provides a method for preparing a modified ternary lithium electrode material, which differs from Example 1 only in that the molar ratio of lithium in lithium acetate to tungsten in ethanol is 0.5:1.5.

[0024] Example 3 This embodiment provides a method for preparing a modified ternary lithium electrode material, which differs from Example 1 only in that the molar ratio of lithium in lithium acetate to tungsten in ethanol is 0.5:2.

[0025] Example 4 This embodiment provides a method for preparing a modified ternary lithium electrode material. The only difference between this method and Example 1 is that "spraying the mixed solution onto the 500g nickel-containing cathode material obtained in step 1) at a rate of 0.5 mL / min by spraying" is replaced with "spraying the mixed solution onto the 500g nickel-containing cathode material obtained in step 1) at a rate of 1 mL / min by spraying".

[0026] Example 5 This embodiment provides a method for preparing a modified ternary lithium electrode material. The only difference between this method and Example 1 is that "then, under a nitrogen atmosphere, a second sintering at 500°C for 5 hours" is replaced with "then, under a nitrogen atmosphere, a second sintering at 700°C for 5 hours".

[0027] Example 6 This embodiment provides a method for preparing a modified ternary lithium electrode material, including the following steps: 1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ nickel-rich precursor and LiOH are mixed, Ni 0.8 Co 0.1 Mn 0.1 The ratio of the total molar amount of Ni, Co, and Mn in the (OH)2 nickel-rich precursor to the molar amount of Li in LiOH is 1:1.03. The precursor is heated to 750℃ at a heating rate of 1℃ / min and calcined for 8 hours to obtain a nickel-containing cathode material. 2) Lithium acetate, tungsten ethoxide, and ethanol were stirred at 80°C and 500 rpm for 6 hours to form a mixed solution. The molar ratio of lithium in lithium acetate to tungsten in tungsten ethoxide was 0.5:1, and the mass concentration of lithium acetate in the mixed solution was 15 wt%. The mixed solution was sprayed at 0.5 mL / min onto 500 g of nickel-containing cathode material obtained in step 1) by spraying (the mass of tungsten in the sprayed mixed solution accounted for 1200 ppm of the mass content of nickel-containing cathode material). The mixture was then stirred at 200 rpm for 25 minutes. The mixture was then sintered at 450°C for 2 hours under an oxygen atmosphere, and then sintered at 700°C for 3 hours under a nitrogen atmosphere to obtain the one-time coated ternary cathode material. 3) The primary coated ternary cathode material obtained in step 2) is subjected to deposition treatment at 50°C under vacuum conditions, including sequentially depositing bis(tert-butylimino)bis(dimethylamino)tungsten on the surface of the primary coated ternary cathode material obtained in step 2), removing excess bis(tert-butylimino)bis(dimethylamino)tungsten by nitrogen purging, and then depositing water. The deposition time of bis(tert-butylimino)bis(dimethylamino)tungsten is 2s, and the deposition time of water is 2s. The above deposition treatment steps are repeated 50 times. The deposition layer is formed by annealing at 700°C for 3h. The average thickness of the deposition layer accounts for 1.5% of the D50 particle size of the primary coated ternary cathode material, thus obtaining the modified ternary lithium electrode material.

[0028] Example 7 This embodiment provides a method for preparing a modified ternary lithium electrode material, including the following steps: 1) Ni 0.8 Co 0.1Mn 0.1 (OH)₂ nickel-rich precursor and LiOH are mixed, Ni 0.8 Co 0.1 Mn 0.1 The ratio of the total molar amount of Ni, Co, and Mn in the nickel-rich (OH)2 precursor to the molar amount of Li in LiOH is 1:1.00. The precursor is heated to 700℃ at a heating rate of 1℃ / min and calcined for 11h to obtain a nickel-containing cathode material. 2) Lithium acetate, tungsten ethoxide, and ethanol were stirred at 80°C and 500 rpm for 6 hours to form a mixed solution. The molar ratio of lithium in lithium acetate to tungsten in tungsten ethoxide was 0.5:1, and the mass concentration of lithium acetate in the mixed solution was 8 wt%. The mixed solution was sprayed at 0.5 mL / min onto 500 g of nickel-containing cathode material obtained in step 1) by spraying (the mass of tungsten in the sprayed mixed solution accounted for 800 ppm of the mass content of nickel-containing cathode material). The mixture was then stirred at 400 rpm for 10 minutes, sintered at 250°C for 3 hours under an oxygen atmosphere, and then sintered at 400°C for 7 hours under a nitrogen atmosphere to obtain the one-time coated ternary cathode material. 3) The primary coated ternary cathode material obtained in step 2) is subjected to deposition treatment at 80°C under vacuum conditions, including sequentially depositing bis(tert-butylimino)bis(dimethylamino)tungsten on the surface of the primary coated ternary cathode material obtained in step 2), removing excess bis(tert-butylimino)bis(dimethylamino)tungsten by nitrogen purging, and then depositing water. The deposition time of bis(tert-butylimino)bis(dimethylamino)tungsten is 4s, and the deposition time of water is 4s. The above deposition treatment steps are repeated 10 times. The deposition layer is formed by annealing at 500°C for 7h. The average thickness of the deposition layer accounts for 1.0% of the D50 particle size of the primary coated ternary cathode material, thus obtaining the modified ternary lithium electrode material.

[0029] Comparative Example 1 This embodiment provides a method for preparing a modified ternary lithium electrode material, including the following steps: 1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ nickel-rich precursor and LiOH are mixed, Ni 0.8 Co 0.1 Mn 0.1 The ratio of the total molar amount of Ni, Co, and Mn in the nickel-rich (OH)2 precursor to the molar amount of Li in LiOH is 1:1.02. The precursor is heated to 650℃ at a heating rate of 1℃ / min and calcined for 7h to obtain a nickel-containing cathode material. 2) The nickel-containing cathode material obtained in step 1) is stirred and mixed at a low speed of 300 rpm for 30 min, sintered for 1 h at 350 °C under an oxygen atmosphere, and then sintered for 5 h at 500 °C under a nitrogen atmosphere to obtain the pretreated ternary cathode material. 3) The pretreated ternary cathode material obtained in step 2) is subjected to deposition treatment at 70°C under vacuum conditions, including sequentially depositing bis(tert-butylimino)bis(dimethylamino)tungsten on the surface of the pretreated ternary cathode material obtained in step 2), removing excess bis(tert-butylimino)bis(dimethylamino)tungsten by nitrogen purging, and then depositing water. The deposition time of bis(tert-butylimino)bis(dimethylamino)tungsten is 3s, and the deposition time of water is 3s. The above deposition treatment steps are repeated 20 times. The deposition layer is formed by annealing at 550°C for 5h. The average thickness of the deposition layer accounts for 1.3% of the D50 particle size of the pretreated ternary cathode material, thus obtaining the modified ternary lithium electrode material.

[0030] Comparative Example 2 This embodiment provides a method for preparing a modified ternary lithium electrode material, including the following steps: 1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ nickel-rich precursor and LiOH are mixed, Ni 0.8 Co 0.1 Mn 0.1 The ratio of the total molar amount of Ni, Co, and Mn in the nickel-rich (OH)2 precursor to the molar amount of Li in LiOH is 1:1.02. The precursor is heated to 650℃ at a heating rate of 1℃ / min and calcined for 7h to obtain a nickel-containing cathode material. 2) Lithium acetate, tungsten ethoxide, and ethanol were stirred at 80°C and 500 rpm for 6 hours to form a mixed solution. The molar ratio of lithium in lithium acetate to tungsten in tungsten ethoxide was 0.5:1, and the mass concentration of lithium acetate in the mixed solution was 10 wt%. The mixed solution was sprayed at 0.5 mL / min onto 500 g of nickel-containing cathode material obtained in step 1) by spraying (the mass of tungsten in the sprayed mixed solution accounted for 1000 ppm of the mass content of nickel-containing cathode material). The mixture was then stirred at 300 rpm for 30 min, sintered at 350°C for 1 hour under an oxygen atmosphere, and then sintered at 500°C for 5 hours under a nitrogen atmosphere to obtain the modified ternary lithium electrode material.

[0031] Test case The modified ternary lithium electrode materials obtained in Examples 1-7 and Comparative Examples 1-2 were used as the main materials to prepare coin cells for electrical performance testing. Coin cell preparation: The main material was mixed in an N-methylpyrrolidone solvent at a mass ratio of 90:5 (polyvinylidene fluoride PVDF):5 (acetylene black), and then homogenized, coated, dried, and cut to form the positive electrode sheet (the areal density of the positive electrode material is 8.0 mg / cm³). 2 A CR2032 coin cell was assembled in an argon-filled glove box using a lithium metal sheet as the counter electrode, a glass fiber as the separator, and a 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC to DMC volume ratio of 1:1) as the electrolyte. The prepared coin cells were placed in the Blue Electric testing system for electrical performance testing. The test conditions were: charge / discharge voltage range of 2.5V-4.25V, test temperature of 25℃, and one cycle at 0.1C / 0.1C to test the specific capacity of the battery during the first charge and the specific capacity during the first discharge. The initial efficiency was calculated as (specific capacity during first discharge / specific capacity during first charge * 100%). Then, the battery's cycle performance was tested by cycling at 1C / 1C for 50 cycles. The test results are shown in Table 1.

[0032]

[0033] Table 1 Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a modified ternary lithium electrode material, characterized in that, Includes the following steps: 1) The nickel-containing precursor and the first lithium source are mixed and calcined to obtain a nickel-containing cathode material; 2) The second lithium source, tungsten source and organic solvent are mixed by first stirring to form a mixed solution. The mixed solution is sprayed onto the nickel-containing cathode material obtained in step 1) by spraying. Then, it is mixed by second stirring and sintered to obtain a one-time coated ternary cathode material. The tungsten source is selected from ethanol tungsten; The sintering includes a first sintering and a second sintering; wherein the first sintering temperature is 250-450℃ and the first sintering time is 1-3h; the second sintering temperature is 400-700℃ and the second sintering time is 3-7h, and the atmosphere is an inert atmosphere; 3) The organic tungsten source precursor and water are deposited sequentially on the surface of the primary coated ternary cathode material obtained in step 2) using atomic layer deposition. Then, the sequential deposition of the organic tungsten source precursor and water is repeated. After the repeated treatment is completed, annealing is performed to obtain the modified ternary lithium electrode material. The average thickness of the deposited layer accounts for 1%-1.5% of the D50 particle size of the primary coated ternary cathode material. The organic tungsten source precursor is selected from bis(tert-butylimino)bis(dimethylamino)tungsten; The deposition temperature is 50-100℃; When the organic tungsten source precursor and water are deposited sequentially, the deposition time of the organic tungsten source precursor is 1-5s, and the deposition time of the water is 1-5s. The deposition process, including the deposition of tungsten source precursors, further includes inert gas purging to remove excess tungsten source precursors. The treatment step of repeatedly depositing the organic tungsten source precursor and water is repeated 1-50 times. The annealing temperature is 400-700℃, and the annealing time is 3-7h.

2. The method for preparing the modified ternary lithium electrode material according to claim 1, characterized in that, The chemical formula of the nickel-containing precursor in step 1) is Ni x Co y Mn z (OH)2, wherein x+y+z = 1. The ratio of the total molar amount of metal elements in the nickel-containing precursor to the molar amount of lithium source in the first lithium source is 1:(0.9-1.02).

3. The method for preparing the modified ternary lithium electrode material according to claim 1, characterized in that, The calcination temperature in step 1) is 650-750℃, and the calcination time is 7-11h; The first lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium acetate, and lithium oxalate.

4. The method for preparing the modified ternary lithium electrode material according to claim 1, characterized in that, In step 2), the second lithium source is selected from at least one of lithium acetate, lithium hydroxide, lithium carbonate, and lithium oxalate; The ratio of the molar amount of lithium in the second lithium source to the molar amount of tungsten in the tungsten source is (0.01-0.5):(0.5-2). The mass concentration of the second lithium source in the mixed solution is 8-15 wt%.

5. The method for preparing the modified ternary lithium electrode material according to claim 1, characterized in that, In step 2), the spraying rate of the mixed solution onto the positive electrode material is 0.5-1 mL / min. In step 2), the second stirring speed is 100-400 rpm and the second stirring time is 10-30 min.

6. The method for preparing the modified ternary lithium electrode material according to claim 1, characterized in that, In step 2), the inert atmosphere is selected from nitrogen atmosphere.

7. The method for preparing the modified ternary lithium electrode material according to claim 1, characterized in that, In step 2), the mass of tungsten in the mixed solution accounts for 800-1200 ppm of the mass content of the nickel-containing cathode material.

8. A modified ternary lithium electrode material, characterized in that, It is prepared by the method for preparing the modified ternary lithium electrode material according to any one of claims 1-7.

9. The application of the modified ternary lithium electrode material according to claim 8 in lithium-ion batteries.

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