Selenium-doped high-nickel ternary material, and preparation method and application thereof

Abstract

The present disclosure relates to a selenium-doped high-nickel ternary material, a preparation method and application thereof, the selenium-doped high-nickel ternary material comprising a particle of a chemical formula of Li q Ni x Co y Mn z Se m O p , 0.8 <= q <= 1.2, x + y + z = 1, 0.6 <= x <= 0.9, 0.05 <= y <= 0.2, 0.05 <= z <= 0.2, 0

Description

Technical Field

[0001] This disclosure relates to the field of ternary material preparation for lithium-ion batteries, specifically to a selenium-doped high-nickel ternary material, its preparation method, and its application. Background Technology

[0002] High-nickel ternary material LiNi x Co y M 1-x-y O2 (typically x≥0.6) has a high energy density, which is expected to meet the high driving range requirements of electric vehicles, and is therefore considered the most promising cathode material for lithium-ion batteries. However, Ni... 2+ With Li + With similar ionic radii, dislocation phenomena (i.e., Li / Ni mixing) easily occur, affecting the layered structure stability of ternary materials. As the Ni content increases, the discharge specific capacity of ternary materials increases, but the Li / Ni mixing intensifies, leading to an increase in irreversible capacity and a decrease in the stability of the ternary materials. This results in a decline in their electrochemical cycling performance and thermal stability, which is detrimental to practical production and applications. Studies have shown that bulk ion doping is an effective way to improve the stability of the layered structure of materials. Numerous reports have been made on doping with high-valence metal elements (such as Al, Nb, Zr, V, Ti, etc.) and low-valence non-metal elements (such as F, B, P, etc.), but research on doping with high-valence non-metal elements is relatively limited.

[0003] The literature Adv. Funct. Mater. 2021, 31, 2010095 achieved bulk doping of high-valence P and B ions by introducing NH4H2PO4 and B2O3 during lithiation calcination. Compared with undoped ternary materials, the doped materials exhibited significantly superior electrochemical cycling stability. Therefore, doping with high-valence non-metallic ions is expected to effectively improve material stability. Selenium (Se) itself has excellent electronic conductivity and high capacity, playing an important role in Li-Se batteries. Introducing Se doping into layered materials LiCoO2 has shown good performance (Adv. Mater. 2020, 2005182), but Se readily reacts with lithium salts to form a lithium selenate coating, leading to a decrease in battery specific capacity. However, there are still few reports on the bulk doping modification of ternary materials by Se. Summary of the Invention

[0004] The purpose of this disclosure is to provide a selenium-doped high-nickel ternary material, its preparation method, and its application. This selenium-doped high-nickel ternary material has a stable layered structure and can effectively improve the electrochemical cycling stability of the material.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a selenium-doped high-nickel ternary material, wherein the selenium-doped high-nickel ternary material comprises a compound with the chemical formula Li q Ni x Co y Mn z Se m O p For particles, 0.8 ≤ q ≤ 1.2, x + y + z = 1, 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.2, 0.05 ≤ z ≤ 0.2, 0 <m≤0.1,1.9≤p≤2.3;

[0006] The high-nickel ternary material has selenium doped into its crystal lattice.

[0007] Optionally, the selenium element includes +4 valent selenium and / or +6 valent selenium.

[0008] Optionally, the average particle size is 3-16 μm.

[0009] A second aspect of this disclosure provides a method for preparing selenium-doped high-nickel ternary materials, the method comprising the following steps:

[0010] S1. The selenium source is mixed with the high-nickel ternary precursor and subjected to a first heat treatment in an oxygen-containing atmosphere to obtain the selenium-doped high-nickel ternary precursor.

[0011] S2. The lithium source is mixed with the selenium-doped high-nickel ternary precursor and subjected to a second heat treatment in an oxygen-containing atmosphere.

[0012] Optionally, the chemical formula of the high-nickel ternary precursor is Ni a Co b Mn c (OH)2, a+b+c=1, 0.6≤a≤0.9, 0.05≤b≤0.2, 0.05≤c≤0.2;

[0013] The average particle size of the high-nickel ternary precursor is 3-16 μm.

[0014] Optionally, the selenium source includes one or more of elemental selenium, selenium dioxide, sodium selenate, sodium selenite, and selenium tetrachloride;

[0015] The lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium chloride.

[0016] Optionally, the molar ratio of the selenium source to the high-nickel ternary precursor, calculated as selenium element, is (0.05-10):100;

[0017] The molar ratio of the lithium source to the high-nickel ternary precursor, calculated as lithium element, is (0.8-1.2):1.

[0018] Optionally, in step S1, the first heat treatment is calcination, and the conditions for the first heat treatment include: a time of 2-10 hours and a temperature of 300-600°C.

[0019] In step S2, the second heat treatment method is calcination, and the conditions for the second heat treatment include: time of 5-25 hours and temperature of 600-850℃.

[0020] Optionally, the oxygen-containing atmosphere is an oxygen atmosphere or an air atmosphere;

[0021] Optionally, the mixing method is solid-phase ball milling for 0.5-5 hours.

[0022] The third aspect of this disclosure provides a selenium-doped high-nickel ternary material prepared using the method described in the second aspect of this disclosure.

[0023] This disclosure provides a fourth aspect of a lithium-ion battery, the lithium-ion battery comprising a positive electrode, an electrolyte and a negative electrode, wherein the positive electrode comprises a selenium-doped high-nickel ternary material as described in the first or third aspect of this disclosure.

[0024] Through the above technical solution, this disclosure introduces a selenium source into a high-nickel ternary precursor and then pre-calcines it to obtain a selenium-doped high-nickel ternary material. The preparation method of this disclosure effectively expands the spatial distance between Se atoms and Li atoms, realizing bulk doping of Se elements in the high-nickel ternary material. Furthermore, the selenium element in the material mainly exists in a high valence state and is doped in the lattice of the high-nickel ternary material, which can reduce the Li / Ni mixing degree, increase the layered structure stability of the ternary material, and effectively improve the electrochemical cycle stability of the material.

[0025] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0027] Figure 1 The X-ray diffraction patterns are those of the high-nickel ternary materials prepared in Example 1 and Comparative Example 1 of this disclosure.

[0028] Figure 2 The X-ray diffraction patterns are shown for the high-nickel ternary materials prepared in Examples 2, 3 and Comparative Example 2 of this disclosure.

[0029] Figure 3The X-ray diffraction patterns are shown for the high-nickel ternary materials prepared in Example 4 and Comparative Example 3 of this disclosure.

[0030] Figure 4 Scanning electron microscope image and elemental distribution map of the high-nickel ternary material prepared in Example 2 of this disclosure.

[0031] Figure 5 The X-ray photoelectron spectrum of the high-nickel ternary material prepared in Example 2 of this disclosure is shown.

[0032] Figure 6 Electrochemical cycling diagrams of the high-nickel ternary materials prepared in Examples 2, 3 and Comparative Example 2 of this disclosure. Detailed Implementation

[0033] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0034] The first aspect of this disclosure provides a selenium-doped high-nickel ternary material, said selenium-doped high-nickel ternary material comprising a compound with the chemical formula Li. q Ni x Co y Mn z Se m O p For particles, 0.8 ≤ q ≤ 1.2, x + y + z = 1, 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.2, 0.05 ≤ z ≤ 0.2, 0 <m≤0.1,1.9≤p≤2.3;

[0035] The high-nickel ternary material has selenium doped into its crystal lattice.

[0036] According to one embodiment of the present disclosure, XPS analysis of the selenium-doped high-nickel ternary material of the present disclosure shows that selenium exists in a higher valence state, for example, selenium includes +4 valence selenium and / or +6 valence selenium.

[0037] In this disclosure, "the high-nickel ternary material is doped with selenium" means that at least a portion of the selenium element is doped in the lattice of the high-nickel ternary material, and preferably, all of the selenium element is doped in the lattice of the high-nickel ternary material.

[0038] According to one embodiment of this disclosure, the average particle size is 3-16 μm.

[0039] A second aspect of this disclosure provides a method for preparing selenium-doped high-nickel ternary materials, the method comprising the following steps:

[0040] S1. The selenium source is mixed with the high-nickel ternary precursor and subjected to a first heat treatment in an oxygen-containing atmosphere to obtain the selenium-doped high-nickel ternary precursor.

[0041] S2. The lithium source is mixed with the selenium-doped high-nickel ternary precursor and subjected to a second heat treatment in an oxygen-containing atmosphere.

[0042] According to one embodiment of this disclosure, the chemical formula of the high-nickel ternary precursor is Ni. a Co b Mn c (OH)2, a+b+c=1, 0.6≤a≤0.9, 0.05≤b≤0.2, 0.05≤c≤0.2; the average particle size of the high-nickel ternary precursor is 3-16μm.

[0043] In this disclosure, in order to achieve uniform mixing, the mixing method in steps S1 and S2 can be solid-phase ball milling for 0.5-5 hours; solid-phase ball milling can be carried out, for example, on a planetary ball mill.

[0044] According to one embodiment of this disclosure, the selenium source and lithium source are conventional in the art. For example, the selenium source includes one or more of elemental selenium, selenium dioxide, sodium selenate, sodium selenite, and selenium tetrachloride; the lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium chloride.

[0045] According to one embodiment of this disclosure, the molar ratio of selenium source to high-nickel ternary precursor, calculated as selenium element, is (0.05-10):100, preferably (0.5-5):100, and more preferably (0.5-3.5):100.

[0046] According to one embodiment of this disclosure, the molar ratio of lithium source to high-nickel ternary precursor, calculated as lithium element, is (0.8-1.2):1, preferably (1.0-1.1):1.

[0047] According to one embodiment of this disclosure, in steps S1 and S2, the oxygen-containing atmosphere is an oxygen atmosphere or an air atmosphere.

[0048] According to one embodiment of this disclosure, in step S1, the first heat treatment is calcination, which can be carried out in a sagger. The conditions for the first heat treatment include: a time of 2-10 hours, preferably 3-6 hours; and a temperature of 300-600°C, preferably 500-600°C. The above temperature range can avoid the volatilization of selenium due to excessively high temperatures, and also avoid uneven distribution of selenium due to excessively low temperatures.

[0049] According to one embodiment of this disclosure, in step S2, the second heat treatment is calcination, which can be carried out in a sagger; the conditions for the second heat treatment include: a time of 5-25 hours, preferably 10-20 hours; and a temperature of 600-850°C, preferably 700-800°C.

[0050] The third aspect of this disclosure provides a selenium-doped high-nickel ternary material prepared by the method described in the second aspect of this disclosure. The material has the same characteristics as the selenium-doped high-nickel ternary material described in the first aspect of this disclosure, and will not be described in detail here.

[0051] This disclosure provides a fourth aspect of a lithium-ion battery, the lithium-ion battery comprising a positive electrode, an electrolyte and a negative electrode, wherein the positive electrode comprises a selenium-doped high-nickel ternary material as described in the first or third aspect of this disclosure.

[0052] According to one embodiment of this disclosure, the negative electrode is conventional in the art and may include one or more of lithium sheets, carbon materials, and silicon-carbon composite materials.

[0053] According to one embodiment of this disclosure, the electrolyte is conventional in the art, and may include one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, lithium hexafluorophosphate, and dimethyl carbonate.

[0054] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way.

[0055] All raw materials used in the examples were obtained through commercial purchases and, unless otherwise specified, were of analytical grade.

[0056] The scanning electron microscope was tested using a FEI QUANTA400 instrument, and the method used an accelerating voltage of 20 kV.

[0057] The X-ray photoelectron spectroscopy instrument was a Thermo Fisher Thermo ESCALAB 250 from the United States, and the method used was an Al Kα X-ray emission source.

[0058] The X-ray diffraction pattern was tested using an X-ray powder diffractometer manufactured by Philips, USA. The method used a Cu target anode Kα radiation source with a step width of 0.02°, a scanning speed of 2° / min, and 2θ = 10°-80°.

[0059] The average particle size was measured using a laser particle size analyzer, specifically a MasterSizer 2000 instrument.

[0060] Example 1

[0061] The selenium-doped high-nickel ternary material A1 was prepared using the following steps:

[0062] (1) Selenium powder and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (average particle size of 6.96 μm) was mixed evenly in a planetary ball mill at a molar ratio of 0.5:100 for 3 hours. The resulting mixture was then placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 550 °C for 3 hours to obtain a selenium-doped high-nickel ternary precursor.

[0063] (2) LiOH·H2O and the above-mentioned selenium-doped high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750℃ for 10 hours. The resulting solid product was crushed and sieved to obtain selenium-doped high-nickel ternary material Al with an average particle size of 7.99 μm and the chemical formula LiNi. 0.8 Co 0.1 Mn 0.1 Se 0.005 O 2.0125 According to the X-ray photoelectron spectroscopy, the selenium element included both +4 and +6 valence selenium.

[0064] Example 2

[0065] The selenium-doped high-nickel ternary material A2 was prepared using the following steps:

[0066] (1) SeO2 and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (average particle size of 10.03 μm) was mixed evenly in a planetary ball mill at a molar ratio of 1:100 for 2 hours. The resulting mixture was then placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 500 °C for 5 hours to obtain a selenium-doped high-nickel ternary precursor.

[0067] (2) LiOH·H2O and the above-mentioned selenium-doped high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1.05:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750℃ for 15 hours. The resulting solid product was crushed and sieved to obtain selenium-doped high-nickel ternary material A2 with an average particle size of 10.08 μm and the chemical formula Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 Se0.01 O 2.05 According to the X-ray photoelectron spectroscopy, the selenium element included both +4 and +6 valence selenium.

[0068] Example 3

[0069] The selenium-doped high-nickel ternary material A3 was prepared using the following steps:

[0070] (1) SeO2 and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (average particle size of 10.03 μm) was mixed evenly in a planetary ball mill at a molar ratio of 4:100 for 3 hours. The resulting mixture was then placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 500 °C for 5 hours to obtain a selenium-doped high-nickel ternary precursor.

[0071] (2) LiOH·H2O and the above-mentioned selenium-doped high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1.05:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750℃ for 15 hours. The resulting solid product was crushed and sieved to obtain selenium-doped high-nickel ternary material A3 with an average particle size of 10.38 μm and the chemical formula Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 Se 0.04 O 2.125 According to the X-ray photoelectron spectroscopy, the selenium element included both +4 and +6 valence selenium.

[0072] Example 4

[0073] The selenium-doped high-nickel ternary material A4 was prepared using the following steps:

[0074] (1) SeO2 and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (average particle size of 14.01 μm) was mixed uniformly in a planetary ball mill at a molar ratio of 2:100 for 4 hours. The resulting mixture was then placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 600 °C for 5 hours to obtain a selenium-doped high-nickel ternary precursor.

[0075] (2) LiOH·H2O and the above-mentioned selenium-doped high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1.1:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750℃ for 18 hours. The resulting solid product was crushed and sieved to obtain selenium-doped high-nickel ternary material A3 with an average particle size of 13.43 μm and the chemical formula Li 1.1 Ni 0.8 Co 0.1 Mn 0.1 Se 0.02 O 2.1 According to the X-ray photoelectron spectroscopy, the selenium element included both +4 and +6 valence selenium.

[0076] Example 5

[0077] The selenium-doped high-nickel ternary material A5 was prepared using the method described in Example 1, except that the high-nickel ternary precursor was replaced with Ni. 0.6 Co 0.2 Mn 0.2 (OH)2 (average particle size 9.62 μm), replacing LiOH·H2O with lithium carbonate of equal molar Li, selenium-doped high-nickel ternary material A5, average particle size 9.71 μm, chemical formula LiNi 0.6 Co 0.2 Mn 0.2 Se 0.005 O 2.0125 According to the X-ray photoelectron spectroscopy, the selenium element included both +4 and +6 valence selenium.

[0078] Comparative Example 1

[0079] The high-nickel ternary material D1 was prepared using the following steps:

[0080] (1) The high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (average particle size of 6.96 μm) was placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 550 °C for 3 h to obtain a pre-calcined high-nickel ternary precursor.

[0081] (2) LiOH·H2O and the above-mentioned pre-calcined high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750℃ for 10 hours. The resulting solid product was crushed and sieved to obtain high-nickel ternary material D1 with an average particle size of 7.94 μm and the chemical formula LiNi. 0.8 Co0.1 Mn 0.1 O2.

[0082] Comparative Example 2

[0083] The high-nickel ternary material D2 was prepared using the following steps:

[0084] (1) The high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (average particle size of 10.03 μm) was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 500 °C for 5 h to obtain a pre-calcined high-nickel ternary precursor.

[0085] (2) LiOH·H2O and the above-mentioned pre-calcined high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1.05:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750℃ for 15 hours. The resulting solid product was crushed and sieved to obtain high-nickel ternary material D2 with an average particle size of 10.07 μm and the chemical formula Li 1.05 Ni 0.8 Co 0.1 Mn 0.1 O 2.025 .

[0086] Comparative Example 3

[0087] The high-nickel ternary material D3 was prepared using the following steps:

[0088] (1) The high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (average particle size of 14.01 μm) was placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 600 °C for 5 h to obtain a pre-calcined high-nickel ternary precursor.

[0089] (2) LiOH·H2O and the above-mentioned pre-calcined high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1.1:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750℃ for 18 hours. The resulting solid product was crushed and sieved to obtain high-nickel ternary material D3 with an average particle size of 12.95 μm and the chemical formula Li 1.1 Ni 0.8 Co 0.1 Mn 0.1 O 2.05 .

[0090] Comparative Example 4

[0091] The high-nickel ternary material D4 was prepared using the following steps:

[0092] (1) The high-nickel ternary precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2 (average particle size of 9.62 μm) was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 550 °C for 3 h to obtain a pre-calcined high-nickel ternary precursor.

[0093] (2) Lithium carbonate and the above-mentioned pre-calcined high-nickel ternary precursor were mixed evenly in a planetary ball mill at a molar ratio of 1:1. The resulting mixture was placed in a crucible and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750°C for 10 hours. The resulting solid product was crushed and sieved to obtain high-nickel ternary material D4 with an average particle size of 9.69 μm and the chemical formula LiNi. 0.6 Co 0.2 Mn 0.2 O2.

[0094] XRD tests were performed on the selenium-doped high-nickel ternary material A1 prepared in Example 1 and the high-nickel ternary material D1 prepared in Comparative Example 1. The results are as follows: Figure 1 As shown.

[0095] according to Figure 1 The results show that, under the same conditions, compared with the undoped high-nickel ternary material (Comparative Example 1), the selenium-doped high-nickel ternary material (Example 1) has higher I content. 003 / I 104 The ratio increased from 1.30 to 1.33, indicating that the Li / Ni mixing degree decreased and the layered structure of the material became more stable.

[0096] The (003) peak position of the selenium-doped high-nickel ternary material A1 is shifted at a lower angle relative to the (003) peak of the high-nickel ternary material D1, indicating that selenium is doped inside the crystal lattice of the high-nickel ternary material. Furthermore, no obvious Li2SeO4 diffraction peaks are observed in the range of 2θ = 20-27°, indicating that no Li2SeO4 coating layer is formed on the surface of the high-nickel ternary material disclosed in this invention.

[0097] XRD, scanning electron microscopy, and X-ray photoelectron spectroscopy were performed on the selenium-doped high-nickel ternary material A2 prepared in Example 2 and the high-nickel ternary material D2 prepared in Comparative Example 2. The results are as follows: Figure 2 , Figure 4 and Figure 5 As shown.

[0098] according to Figure 2The results show that, under the same conditions, compared with the undoped high-nickel ternary material (Comparative Example 2), the high-nickel ternary material with a small amount of selenium doping (Example 2) has higher I content. 003 / I 104 The ratio increased from 1.22 to 1.34, indicating that the Li / Ni mixing degree decreased and the layered structure of the material became more stable.

[0099] The (003) peak position of the selenium-doped high-nickel ternary material A2 is shifted at a lower angle relative to the (003) peak of the high-nickel ternary material D2, indicating that selenium is doped inside the crystal lattice of the high-nickel ternary material. Furthermore, no obvious Li2SeO4 diffraction peaks are observed in the range of 2θ = 20-27°, indicating that no Li2SeO4 coating layer is formed on the surface of the high-nickel ternary material disclosed in this invention.

[0100] according to Figure 4 The results show that the Se element is evenly distributed and no obvious aggregation phenomenon is observed.

[0101] according to Figure 5 The results show that the selenium element includes +4-valent selenium and +6-valent selenium, that is, Se element is doped into the high-nickel ternary material in a higher valence state.

[0102] The selenium-doped high-nickel ternary material A3 prepared in Example 3 was subjected to XRD testing, and the results are as follows: Figure 2 As shown.

[0103] according to Figure 2 The results show that, compared to the selenium-doped high-nickel ternary material (Example 2), the selenium-doped high-nickel ternary material (Example 3) has higher efficiency. 003 / I 104 The ratio of (003) and the peak position of (003) remain almost unchanged, but obvious diffraction peaks of Li2SeO4 appear in the range of 2θ = 20-27°, indicating that some of the Se source and lithium source in the high-nickel ternary material A3 form a Li2SeO4 coating layer on the surface of the high-nickel ternary material.

[0104] XRD tests were performed on the selenium-doped high-nickel ternary material A4 prepared in Example 4 and the high-nickel ternary material D3 prepared in Comparative Example 3. The results are as follows: Figure 3 As shown.

[0105] according to Figure 3 The results show that, under the same conditions, compared with the undoped high-nickel ternary material (Comparative Example 3), the high-nickel ternary material with a small amount of selenium doping (Example 4) has higher I content. 003 / I 104 The ratio increased from 1.21 to 1.31, indicating that the Li / Ni mixing degree decreased and the layered structure of the material became more stable.

[0106] The (003) peak position of the selenium-doped high-nickel ternary material A4 is shifted at a lower angle relative to the (003) peak of the high-nickel ternary material D3, indicating that selenium is doped inside the crystal lattice of the high-nickel ternary material. Furthermore, no obvious Li2SeO4 diffraction peaks are observed in the range of 2θ = 20-27°, indicating that no Li2SeO4 coating layer is formed on the surface of the high-nickel ternary material disclosed in this invention.

[0107] XRD tests were performed on the selenium-doped high-nickel ternary material A5 prepared in Example 5 and the high-nickel ternary material D5 prepared in Comparative Example 5. The results show that, under the same conditions, compared to the undoped high-nickel ternary material (Comparative Example 5), the high-nickel ternary material (Example 5) with a small amount of selenium doping has a higher concentration of I... 003 / I 104 The decrease in the Li / Ni ratio indicates a smaller degree of Li / Ni mixing, resulting in a more stable layered structure in the material.

[0108] The (003) peak position of the selenium-doped high-nickel ternary material A5 is shifted at a lower angle relative to the (003) peak of the high-nickel ternary material D5, indicating that selenium is doped inside the crystal lattice of the high-nickel ternary material. Furthermore, no obvious Li2SeO4 diffraction peaks are observed in the range of 2θ = 20-27°, indicating that no Li2SeO4 coating layer is formed on the surface of the high-nickel ternary material disclosed in this invention.

[0109] Test case

[0110] Electrochemical stability tests were performed on the selenium-doped high-nickel ternary material A2 prepared in Example 2, the selenium-doped and lithium selenate-coated high-nickel ternary material A3 prepared in Example 3, and the high-nickel ternary material D2 prepared in Comparative Example 2. The specific steps are as follows:

[0111] Ternary materials, conductive agent (acetylene black), and binder (polyvinylidene fluoride) were weighed according to a mass ratio of 94:3:3 and mixed evenly. The mixture was then coated onto aluminum foil and cut into sheets to serve as the positive electrode. In an argon-atmospheric glove box, the positive electrode, negative electrode (lithium sheet), separator (Celgard 2300), and electrolyte (1M LiPF6 dissolved in a 1:1:1 volume ratio of ethylene carbonate EC: dimethyl carbonate DEC: ethyl methyl carbonate EMC) were assembled into a coin cell. Charge-discharge tests were then conducted on a Blue Electric CT-3001A 1U system. The charge-discharge voltage range was 2.75-4.3V, and the charge-discharge rate was 0.5C (1C = 200mA·g). -1 The result is as follows: Figure 6 As shown.

[0112] according to Figure 6The results show that the lithium-ion battery prepared using D2 retains 84.5% of its capacity after 150 cycles; the lithium-ion battery prepared using A2, compared to the lithium-ion battery prepared using D2, does not show a decrease in initial capacity and retains 91.1% of its capacity after 150 cycles; the lithium-ion battery prepared using A3, compared to the lithium-ion batteries prepared using A2 and D2, shows a decrease in initial capacity and retains 96.0% of its capacity after 150 cycles, but its capacity is still lower than that of A2. Based on the above data, it can be seen that doping selenium into the lattice of high-nickel ternary materials can maintain the initial capacity of the high-nickel ternary materials and significantly improve their stability, while the formation of a lithium selenate coating on the surface will reduce the initial capacity of the high-nickel ternary materials. Therefore, the selenium-doped high-nickel ternary materials disclosed in this invention possess excellent electrochemical stability.

[0113] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0114] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0115] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing selenium-doped high-nickel ternary materials, characterized in that, The method includes the following steps: S1. The selenium source is mixed with the high-nickel ternary precursor and subjected to a first heat treatment in an oxygen-containing atmosphere to obtain the selenium-doped high-nickel ternary precursor. S2. The lithium source is mixed with the selenium-doped high-nickel ternary precursor and subjected to a second heat treatment in an oxygen-containing atmosphere. The molar ratio of the selenium source to the high-nickel ternary precursor, calculated as selenium element, is (1-3.5):100; In step S1, the first heat treatment method is calcination, and the conditions of the first heat treatment include: time of 2-10 hours and temperature of 300-600℃. In step S2, the second heat treatment method is calcination, and the conditions for the second heat treatment include: time of 5-25 hours and temperature of 600-850℃. The selenium-doped high-nickel ternary material includes materials with the chemical formula Li. q Ni x Co y Mn z Se m O p For particles, 0.8 ≤ q ≤ 1.2, x + y + z = 1, 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.2, 0.05 ≤ z ≤ 0.2, 0 <m≤0.1,1.9≤p≤2.3; The high-nickel ternary material is doped with selenium in its crystal lattice; the selenium includes +4-valent selenium and +6-valent selenium.

2. The method according to claim 1, wherein, The chemical formula of the high-nickel ternary precursor is Ni a Co b Mn c (OH)2, a+b+c=1, 0.6≤a≤0.9, 0.05≤b≤0.2, 0.05≤c≤0.2; The average particle size of the high-nickel ternary precursor is 3-16 μm.

3. The method according to claim 1, wherein, The selenium source includes one or more of elemental selenium, selenium dioxide, sodium selenate, sodium selenite, and selenium tetrachloride. The lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium chloride.

4. The method according to claim 1, wherein, The molar ratio of the lithium source to the high-nickel ternary precursor, calculated as lithium element, is (0.8-1.2):

1.

5. The method according to claim 1, wherein, The oxygen-containing atmosphere is an oxygen atmosphere or an air atmosphere.

6. The method according to claim 1, wherein, The mixing method is solid-phase ball milling, with a time of 0.5-5 h.

7. A selenium-doped high-nickel ternary material prepared by the method according to any one of claims 1-6.

8. The selenium-doped high-nickel ternary material according to claim 7, wherein, The average particle size is 3-16 μm.

9. A lithium-ion battery, the lithium-ion battery comprising a positive electrode, an electrolyte, and a negative electrode, characterized in that, The positive electrode comprises the selenium-doped high-nickel ternary material as described in claim 7 or 8.

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