A high-nickel ternary material with phosphorus-sulfur co-doping on the surface, a preparation method thereof, and a lithium-ion battery containing the same

Abstract

The present invention relates to a surface phosphorus-sulfur co-doped high nickel ternary material, a preparation method thereof, and a lithium ion battery containing the same. The surface phosphorus-sulfur co-doped high nickel ternary material comprises a chemical formula of Li q Ni x Co y Mn z O p P m S n Particles, x+y+z=1, 0.6≤x≤0.9, 0.05≤y≤0.2, 0.05≤z≤0.2, 0.8≤q≤1.2, 1.8≤p≤2.2, 0

Description

Technical Field

[0001] The present disclosure relates to the field of preparation of ternary materials for lithium-ion batteries, and in particular to a high-nickel ternary material with phosphorus and sulfur co-doped on the surface, a preparation method thereof, and a lithium-ion battery comprising the same. Background Art

[0002] Lithium-ion batteries play a vital role in the fields of power supply and energy storage. Among them, high-nickel ternary materials (Ni ≥ 0.6) have the advantages of low cost and high specific capacity, and are currently the mainstream positive electrode materials for high-energy-density lithium-ion batteries. As the nickel content increases, the discharge specific capacity of the ternary material increases, but when the Ni content is ≥ 0.6, the material is unstable in the air and easily absorbs water to produce surface residual alkali (including residual LiOH and Li2CO3), which reduces the performance of the material and easily leads to surface side reactions and safety hazards. Therefore, the material requires more stringent storage and transportation conditions.

[0003] To reduce the air sensitivity of materials, the most effective method is to modify their surface. Surface ion doping not only prevents material capacity loss but also increases the surface stability of the material itself, potentially meeting the need for direct surface modification. Currently, surface doping mostly uses a single element, which has limited effects on the cycling and safety performance of high-nickel ternary materials. Therefore, multi-element surface doping is gradually gaining attention.

[0004] For example, fluorine-phosphorus co-doping reported in CN112018332A, germanium / fluorine / nitrogen co-doping reported in CN111653762A, and aluminum-fluorine co-doping reported in CN111377487A can reduce surface side reactions and improve material structural stability. However, the distribution of dopant ions is difficult to control, so effective surface ion doping methods still face certain difficulties. Summary of the Invention

[0005] The present disclosure provides a surface phosphorus-sulfur co-doped high-nickel ternary material, a preparation method thereof, and a lithium-ion battery containing the same. The phosphorus and sulfur elements in the phosphorus-sulfur co-doped high-nickel ternary material are doped on the material surface, resulting in low air sensitivity and a long shelf life, making it easy to store and transport. The lithium-ion battery containing the material exhibits good cycle performance.

[0006] In order to achieve the above-mentioned object, the present disclosure provides a surface phosphorus-sulfur co-doped high nickel ternary material in the first aspect, wherein the surface phosphorus-sulfur co-doped high nickel ternary material comprises a chemical formula of Li q Ni x Co y Mn z O p P m S nParticles, where x + y + z = 1, 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.2, 0.05 ≤ z ≤ 0.2, 0.8 ≤ q ≤ 1.2, 1.8 ≤ x ≤ 2.2, 0 < m ≤ 0.1, 0 < n ≤ 0.1; wherein, phosphorus and sulfur elements are doped on the surface of the particles.

[0007] Optionally, the surface phosphorus-sulfur co-doped high-nickel ternary material has the following scanning electron microscope energy spectrum and X-ray photoelectron spectrum characteristics:

[0008] A1 is 0.1 - 5%, A2 is 0.1 - 5%, A = A1 + A2, and A is 0.2 - 10%;

[0009] Based on the total number of atoms of all elements on the surface of the particles, A1 is the atomic proportion of phosphorus element on the surface of the particles;

[0010] A2 is the atomic proportion of sulfur element on the surface of the particles;

[0011] A is the sum of the atomic proportions of phosphorus and sulfur elements on the surface of the particles;

[0012] D1 is 0.01 - 2.5%, D2 is 0.01 - 2.5%, D = D1 + D2, and D is 0.02 - 5%;

[0013] Based on the total number of atoms of all elements in the particle bulk phase, D1 is the total atomic proportion of phosphorus element in the particle bulk phase; <00OO070>D2 is the total atomic proportion of sulfur element in the particle bulk phase;

[0015] D is the sum of the total atomic proportions of phosphorus and sulfur elements in the particle bulk phase;

[0016] The ratio of A to D is 2 - 20. [[ID=;32]]<00OO076>The second aspect of the present disclosure provides a method for preparing a surface phosphorus-sulfur co-doped high-nickel ternary material, the method comprising the following steps:

[0018] S1 Mix a lithium source with a high-nickel ternary precursor and perform a first heat treatment in an oxygen atmosphere or an air atmosphere to obtain a first solid material;

[0019] S2 In an inert atmosphere, perform a second heat treatment on the first non-metal source and the first solid material to obtain a second solid material;

[0020] S3 In an inert atmosphere, perform a third heat treatment on the second non-metal source and the second solid material;

[0021] Wherein, the first non-metal source is a phosphorus source, and the second non-metal source is a sulfur source;

[0022] Alternatively, the first non-metal source is a sulfur source, and the second non-metal source is a phosphorus source.

[0023] Optionally, the chemical formula of the high nickel ternary precursor is Ni x Co y Mn z (OH)2, x+y+z=1, 0.6≤x≤0.9, 0.05≤y≤0.2, 0.05≤z≤0.2.

[0024] Optionally, the molar ratio of the lithium source to the high-nickel ternary precursor, calculated as lithium element, is (0.8-1.2):1;

[0025] The molar ratio of the phosphorus source to the first solid material, calculated as phosphorus element, is (0.1-10):10;

[0026] The molar ratio of the sulfur source to the first solid material, calculated as sulfur element, is (0.1-10):10.

[0027] Optionally, the lithium source includes one or more of lithium hydroxide, lithium carbonate and lithium nitrate;

[0028] The phosphorus source includes one or more of sodium hypophosphite, ammonium hypophosphite and red phosphorus;

[0029] The sulfur source includes one or more of elemental sulfur, ammonium sulfide and ammonium hydrogen sulfide;

[0030] Optionally, in step S1, the first heat treatment is performed by calcination, and the conditions of the first heat treatment include: a time of 10-20 hours and a temperature of 600-850°C;

[0031] In step S2 and step S3, the second heat treatment and the third heat treatment are performed by calcination. The conditions of the second heat treatment and the third heat treatment are the same or different and independently include: a time of 1-5 hours and a temperature of 200-550° C.;

[0032] In step S2 and step S3, the inert atmosphere includes one or more of nitrogen, argon and helium.

[0033] Optionally, step S2 and step S3 are performed in a tube furnace, the first non-metallic source and the second non-metallic source are respectively placed upstream of the tube furnace, and the first solid material and the second solid material are respectively placed downstream of the tube furnace.

[0034] A third aspect of the present disclosure provides a surface phosphorus-sulfur co-doped high-nickel ternary material prepared by the method described in the second aspect of the present disclosure.

[0035] A fourth aspect of the present disclosure provides a lithium-ion battery, comprising a positive electrode, an electrolyte, and a negative electrode, wherein the positive electrode comprises the phosphorus-sulfur co-doped high-nickel ternary material described in the first aspect or the third aspect of the present disclosure.

[0036] Through the above technical solution, the phosphorus and sulfur elements in the surface phosphorus-sulfur co-doped high-nickel ternary material of the present application are mainly doped on the surface of the particles, which can improve the surface stability of the material. On the one hand, the co-doping of surface phosphorus and sulfur can reduce the air sensitivity of the material and extend the shelf life. After long-term storage, the material can still maintain a high initial charge and discharge specific capacity, making it easy to store and transport. On the other hand, the co-doping of surface phosphorus and sulfur can have a coating effect, preventing electrolyte corrosion on the material. Under long-term electrochemical cycles, the material can still maintain a relatively stable structure and a high capacity retention rate, showing excellent electrochemical cycle stability.

[0037] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0039] Figure 1 This is the first charge and discharge curve of the surface phosphorus-sulfur co-doped high-nickel ternary materials A1 and A1-1 prepared in Examples 1 and 5 of the present application.

[0040] Figure 2 This is the first charge and discharge curve of the high nickel ternary materials D1 and D1-1 prepared in Comparative Examples 1 and 4 of the present application.

[0041] Figure 3 This is the first charge and discharge curve of the high nickel ternary materials D2 and D2-1 prepared in Comparative Examples 2 and 5 of the present application.

[0042] Figure 4 This is the first charge and discharge curve of the high nickel ternary materials D3 and D3-1 prepared in Comparative Examples 3 and 6 of the present application.

[0043] Figure 5 Electrochemical cycle curves of high-nickel ternary materials A2 and D1 prepared in Example 2 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0044] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0045] In the first aspect of the present disclosure, a high-nickel ternary material with surface phosphorus and sulfur co-doping is provided. The high-nickel ternary material with surface phosphorus and sulfur co-doping comprises particles with the chemical formula Li q Ni x Co y Mn z O p P m S n , where x + y + z = 1, 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.2, 0.05 ≤ z ≤ 0.2, 0.8 ≤ q ≤ 1.2, 1.8 ≤ p ≤ 2.2, 0 < m ≤ 0.1, 0 < n ≤ 0.1; wherein the phosphorus element and the sulfur element are doped on the surface of the particles.

[0046] In the present disclosure, "the phosphorus element and the sulfur element are doped on the surface of the particles" means that, based on the total amount of the phosphorus element and the sulfur element in the particles, the content of the phosphorus element and the sulfur element on the surface is higher than that in the bulk phase, and the phosphorus element and the sulfur element in the material of the present application are doped on the surface of the particles. Further, the ratio of the sum of the atomic ratios of the phosphorus element and the sulfur element on the surface of the particles to the sum of the total atomic ratios of the phosphorus element and the sulfur element in the bulk phase of the particles is 2 - 20.

[0047] In an embodiment of the present disclosure, the high-nickel ternary material with surface phosphorus and sulfur co-doping has the following scanning electron microscope energy spectrum and X-ray photoelectron spectrum characteristics:

[0048] A1 is 0.1 - 5%, A2 is 0.1 - 5%, A = A1 + A2, and A is 0.2 - 10%; preferably, A1 is 0.5 - 3%, A2 is 0.5 - 3%, and A is 1 - 6%;

[0049] Based on the total number of atoms of all elements on the surface of the particles, A1 is the atomic ratio of the phosphorus element on the surface of the particles;

[0050] A2 is the atomic ratio of the sulfur element on the surface of the particles;

[0051] A is the sum of the atomic ratios of the phosphorus element and the sulfur element on the surface of the particles;

[0052] D1 is 0.01 - 2.5%, D2 is 0.01 - 2.5%, D = D1 + D2, and D is 0.02 - 5%; preferably, D1 is 0.05 - 1.5%, D2 is 0.05 - 1.5%, and D is 0.1 - 3%;

[0053] Based on the total number of atoms of all elements in the bulk phase of the particles, D1 is the total atomic ratio of the phosphorus element in the bulk phase of the particles;

[0054] D2 is the total atomic ratio of the sulfur element in the bulk phase of the particles;

[0055] D is the sum of the total atomic percentages of phosphorus and sulfur in the particle bulk phase;

[0056] The ratio of A to D is 1-20, preferably 3-10; the ratio of A1 to A2 is 0.1-10, preferably 0.5-5.

[0057] In the present disclosure, "the atomic proportion on the surface of the particle" refers to the ratio of the number of atoms of phosphorus or sulfur on the surface of the particle to the total number of atoms of all elements on the surface; "the total atomic proportion in the bulk phase of the particle" refers to the ratio of the total number of atoms of phosphorus or sulfur in the bulk phase of the particle to the total number of atoms of all elements; all elements include lithium, nickel, cobalt, manganese, oxygen, sulfur and phosphorus.

[0058] In the above preferred embodiment, the phosphorus and sulfur elements of the surface phosphorus-sulfur co-doped high-nickel ternary material disclosed in the present invention are mainly doped on the surface of the particles, which has a coating effect on the internal material, not only reducing the air sensitivity of the material and extending the shelf life; but also avoiding the corrosion of the electrolyte to the material, and maintaining a stable structure and a high capacity retention rate under a longer electrochemical cycle.

[0059] A second aspect of the present disclosure provides a method for preparing a surface phosphorus-sulfur co-doped high-nickel ternary material, the method comprising the following steps:

[0060] S1: mixing a lithium source and a high-nickel ternary precursor and performing a first heat treatment in an oxygen atmosphere or an air atmosphere to obtain a first solid material;

[0061] S2, under an inert atmosphere, subjecting the first non-metallic source and the first solid material to a second heat treatment to obtain a second solid material;

[0062] S3, under an inert atmosphere, subjecting the second non-metallic source and the second solid material to a third heat treatment;

[0063] Wherein, the first non-metallic source is a phosphorus source, and the second non-metallic source is a sulfur source;

[0064] Alternatively, the first non-metal source is a sulfur source, and the second non-metal source is a phosphorus source.

[0065] In order to control the content and ratio of the surface doping elements, the present disclosure dopes phosphorus and sulfur separately, and does not specifically limit the doping order.

[0066] In order to make the prepared material have a higher capacity, in one embodiment of the present disclosure, the chemical formula of the high nickel ternary precursor is Ni x Co y Mn z(OH)2, x+y+z=1, 0.6≤x≤0.9, 0.05≤y≤0.2, 0.05≤z≤0.2, preferably, 0.7≤x≤0.9, 0.05≤y≤0.15, 0.05≤z≤0.15.

[0067] In the present disclosure, the average particle size of the high-nickel ternary precursor is 5-15 μm, for example, 10 μm.

[0068] In one embodiment of the present disclosure, the molar ratio of the lithium source calculated as lithium element to the high-nickel ternary precursor is (0.8-1.2):1, preferably (0.9-1.1):1; the molar ratio of the phosphorus source calculated as phosphorus element to the first solid material is (0.1-10):10, preferably (0.5-5):10; the molar ratio of the sulfur source calculated as sulfur element to the first solid material is (0.1-10):10, preferably (0.5-5):10. By meeting the above ratios, effective surface doping of sulfur and phosphorus elements can be achieved on the basis of obtaining a high-nickel ternary material with better performance.

[0069] In one embodiment of the present disclosure, the lithium source includes one or more of lithium hydroxide, lithium carbonate and lithium nitrate; the phosphorus source includes one or more of sodium hypophosphite, ammonium hypophosphite and red phosphorus; and the sulfur source includes one or more of elemental sulfur, ammonium sulfide and ammonium hydrogensulfide.

[0070] In one embodiment of the present disclosure, in step S1, the first heat treatment is performed by calcination, and the conditions of the first heat treatment include: a time of 10-20 hours and a temperature of 600-850°C; preferably, a time of 12-18 hours and a temperature of 700-800°C.

[0071] In one embodiment of the present disclosure, in step S2 and step S3, the second heat treatment and the third heat treatment are performed by calcination, and the conditions of the second heat treatment and the third heat treatment are the same or different, and each independently includes: time is 1-5h, temperature is 200-550°C; preferably, the conditions of the second heat treatment include: time is 1.5-3h, temperature is 300-500°C; the conditions of the third heat treatment include: time is 1.5-3h, temperature is 300-500°C.

[0072] In one embodiment of the present disclosure, in step S2 and step S3, the inert atmosphere includes one or more of nitrogen, helium and argon.

[0073] In one embodiment of the present disclosure, steps S2 and S3 are performed in a tube furnace, with the first non-metallic source and the second non-metallic source respectively placed upstream of the tube furnace, and the first solid material and the second solid material respectively placed downstream of the tube furnace. Specifically, the steps include: placing the first non-metallic source upstream of the tube furnace, placing the first solid material downstream of the tube furnace, and performing a second heat treatment under an inert atmosphere to obtain the second solid material; placing the second non-metallic source upstream of the tube furnace, placing the second solid material downstream of the tube furnace, and performing a third heat treatment under an inert atmosphere. In the present disclosure, upstream and downstream are defined along the flow direction of the first non-metallic source and the second non-metallic source. The phosphorus source or sulfur source placed upstream generates a fluid containing phosphorus or sulfur under high temperature. The phosphorus-containing fluid is, for example, phosphine and / or gaseous phosphorus, and the sulfur-containing fluid is, for example, hydrogen sulfide and / or elemental sulfur. The phosphorus-containing or sulfur-containing fluid flows downstream and contacts and reacts with the first solid material or the second solid material. The fluid containing phosphorus or sulfur undergoes a substitution reaction with the metal element on the surface of the first solid material or the second solid material to form a metal phosphide or metal sulfide (MP or MS), and / or undergoes an oxidation-reduction reaction to form a metal phosphorus oxide or metal sulfur oxide (MPOx or MSOx, M represents a metal element, x>0), forming a structure in which phosphorus and sulfur elements are doped on the surface.

[0074] A third aspect of the present disclosure provides a surface phosphorus-sulfur co-doped high-nickel ternary material prepared by the method described in the second aspect of the present disclosure.

[0075] In the present disclosure, the phosphorus and sulfur elements of the above-mentioned surface phosphorus-sulfur co-doped high-nickel ternary material are doped on the surface of the particles, and based on the total amount of phosphorus and sulfur elements in the particles, the content of phosphorus and sulfur elements on the surface is higher than that in the bulk phase. For example, after scanning electron microscopy and X-ray photoelectron spectroscopy, the ratio of the sum of the atomic proportions of phosphorus and sulfur elements on the particle surface to the sum of the total atomic proportions in the bulk phase of the particles is 2-20.

[0076] A fourth aspect of the present disclosure provides a lithium-ion battery, comprising a positive electrode, an electrolyte, and a negative electrode, wherein the positive electrode comprises the surface phosphorus-sulfur co-doped high-nickel ternary material described in the first aspect or the third aspect of the present disclosure.

[0077] Furthermore, the negative electrode material of the lithium-ion battery includes one or more of a lithium sheet, a carbon material, and a silicon-carbon composite material, and the electrolyte includes one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, lithium hexafluorophosphate, and dimethyl carbonate. This is conventional in the art and is not specifically required here.

[0078] The reagents used in the examples and comparative examples of this application are all commercially available.

[0079] The scanning electron microscope energy spectrum test instrument model is FEI QUANTA400, and the method is as follows: the acceleration voltage is 20kV;

[0080] The X-ray photoelectron spectroscopy test instrument model is the American Thermo Fisher Thermo ESCALAB 250, and the method is to use an Al Kα X-ray emission light source;

[0081] The test method for the first charge and discharge curve is to use Wuhan LAND CT3001A 1U battery performance test system, and the first charge and discharge rate is 0.1C (1C=200mA / g).

[0082] Examples 1-8 are used to illustrate the surface phosphorus-sulfur co-doped high-nickel ternary material of the present application and its preparation method.

[0083] Example 1

[0084] The surface phosphorus-sulfur co-doped high nickel ternary material of the present application is prepared by the following steps:

[0085] S1 LiOH·H2O and high nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 was mixed uniformly in a planetary ball mill at a molar ratio of 1.05:1, and the obtained mixture was placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750°C for 15 hours. The obtained solid product was crushed and sieved to obtain a first solid material;

[0086] S2: Under a nitrogen atmosphere, sodium hypophosphite and the first solid material are placed in the upstream and downstream of a tube furnace in a molar ratio of 1:10, and subjected to a second heat treatment at 350° C. for 2 h, followed by cooling to room temperature to obtain a second solid material;

[0087] S3, under a nitrogen atmosphere, places sulfur powder and the second solid material respectively in the upstream and downstream of a tube furnace in a molar ratio of sulfur powder to the first solid material of 1:10, and performs a third heat treatment at a temperature of 500°C for 2 hours. After cooling to room temperature, a high-nickel ternary material A1 with surface phosphorus and sulfur co-doping is obtained.

[0088] The surface phosphorus-sulfur co-doped high nickel ternary material A1 prepared in Example 1 was subjected to scanning electron microscope energy spectrum and X-ray photoelectron spectroscopy detection, and the results are listed in Table 1.

[0089] Example 2

[0090] S1 LiOH·H2O and high nickel ternary precursor Ni 0.8 Co 0.1 Mn0.1 (OH)2 was mixed uniformly in a planetary ball mill at a molar ratio of 1.05:1, and the obtained mixture was placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750°C for 15 hours. The obtained solid product was crushed and sieved to obtain a first solid material;

[0091] S2: Under a nitrogen atmosphere, sulfur powder and the first solid material are placed in the upstream and downstream of a tube furnace in a molar ratio of 1:10, and subjected to a second heat treatment at 500° C. for 2 h, and then cooled to room temperature to obtain a second solid material;

[0092] S3: Under a nitrogen atmosphere, sodium hypophosphite and the second solid material are placed in the upstream and downstream of a tube furnace respectively according to a molar ratio of sodium hypophosphite to the first solid material of 1:10, and a third heat treatment is performed at a temperature of 350°C for 2 hours. The material is then cooled to room temperature to obtain a high-nickel ternary material A2 with surface phosphorus-sulfur co-doping.

[0093] The surface phosphorus-sulfur co-doped high nickel ternary material A2 prepared in Example 2 was subjected to scanning electron microscope energy spectrum and X-ray photoelectron spectroscopy detection, and the results are listed in Table 1.

[0094] Example 3

[0095] The same method as in Example 1 was used to prepare the surface phosphorus-sulfur co-doped high nickel ternary material A4, except that the phosphorus source used was ammonium hypophosphite.

[0096] The surface phosphorus-sulfur co-doped high nickel ternary material A3 prepared in Example 3 was subjected to scanning electron microscope energy spectrum and X-ray photoelectron spectroscopy detection. The results are listed in Table 1.

[0097] Example 4

[0098] The same method as in Example 1 was used to prepare the surface phosphorus-sulfur co-doped high nickel ternary material A4, except that the sulfur source used was ammonium hydrogen sulfide.

[0099] The surface phosphorus-sulfur co-doped high nickel ternary material A4 prepared in Example 4 was subjected to scanning electron microscope energy spectrum and X-ray photoelectron spectroscopy detection, and the results are listed in Table 1.

[0100] Comparative Example 1

[0101] The high nickel ternary material D1 was prepared by the following method:

[0102] S1 LiOH·H2O and high nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1(OH)2 was mixed uniformly in a planetary ball mill at a molar ratio of 1.05:1, and the obtained mixture was placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750°C for 15 hours. The obtained solid product was crushed and sieved to obtain a first solid material;

[0103] S2: Under a nitrogen atmosphere, the first solid material is placed in a tubular furnace for a second heat treatment at 350°C for 2 hours, followed by a third heat treatment at 500°C for 2 hours. The material is cooled to room temperature to obtain a high-nickel ternary material D1.

[0104] The high nickel ternary material D1 prepared in Comparative Example 1 was subjected to scanning electron microscope energy spectrum and X-ray photoelectron spectroscopy detection, and the results are listed in Table 1.

[0105] Comparative Example 2

[0106] S1 LiOH·H2O and high nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 was mixed uniformly in a planetary ball mill at a molar ratio of 1.05:1, and the obtained mixture was placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750°C for 15 hours. The obtained solid product was crushed and sieved to obtain a first solid material;

[0107] S2: Under a nitrogen atmosphere, sodium hypophosphite and the first solid material are placed in the upstream and downstream of a tube furnace in a molar ratio of 1:5, and a second heat treatment is performed at 350°C for 2 hours; then a third heat treatment is performed at 500°C for 2 hours, and the mixture is cooled to room temperature to obtain a surface phosphorus-doped high-nickel ternary material D2.

[0108] The surface phosphorus-doped high nickel ternary material D2 prepared in Comparative Example 2 was subjected to scanning electron microscope energy spectrum and X-ray photoelectron spectroscopy detection, and the results are listed in Table 1.

[0109] Comparative Example 3

[0110] S1 LiOH·H2O and high nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 was mixed uniformly in a planetary ball mill at a molar ratio of 1.05:1, and the obtained mixture was placed in a sagger and subjected to a first heat treatment under an oxygen atmosphere at a temperature of 750°C for 15 hours. The obtained solid product was crushed and sieved to obtain a first solid material;

[0111] S2: Under a nitrogen atmosphere, sulfur powder and the first solid material are placed in the upstream and downstream of a tube furnace in a molar ratio of 1:5, and a second heat treatment is performed at 350°C for 2 hours; then a third heat treatment is performed at 500°C for 2 hours, and the material is cooled to room temperature to obtain a surface sulfur-doped high-nickel ternary material D3.

[0112] The surface sulfur-doped high nickel ternary material D3 prepared in Comparative Example 3 was subjected to scanning electron microscopy and X-ray photoelectron spectroscopy, and the results are listed in Table 1.

[0113] Examples 5-8

[0114] The surface phosphorus-sulfur co-doped high nickel ternary materials prepared in Examples 1-4 were placed at room temperature for 45 days to obtain surface phosphorus-sulfur co-doped high nickel ternary materials A1-1, A2-1, A3-1 and A4-1.

[0115] Comparative Examples 4-6

[0116] The high-nickel ternary materials prepared in Comparative Examples 1-3 were placed at room temperature for 45 days to obtain high-nickel ternary materials D1-1, D2-1 and D3-1.

[0117] Figure 1 3. It is the first charge and discharge curve of the surface phosphorus-sulfur co-doped high nickel ternary materials A1 and A1-1 prepared in Example 1 and Example 5.

[0118] Figure 2 These are the first charge and discharge curves of the high-nickel ternary materials D1 and D1-1 prepared in Comparative Examples 1 and 4.

[0119] Figure 3 These are the first charge and discharge curves of the high-nickel ternary materials D2 and D2-1 prepared in Comparative Examples 2 and 5.

[0120] Figure 4 These are the first charge and discharge curves of the high-nickel ternary materials D3 and D3-1 prepared in Comparative Examples 3 and 6.

[0121] Figure 5 Electrochemical cycle curves of high nickel ternary materials A2 and D1 prepared in Example 2 and Comparative Example 1.

[0122] In the above embodiments and comparative examples, the first heat treatment, the second heat treatment and the third heat treatment are all carried out by calcination, and the high nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 The average particle size of (OH)2 is 10 μm, and the testing method is a Malvern laser particle size analyzer.

[0123] Test Example 1-14

[0124] The high nickel ternary materials of Examples 1-8 and Comparative Examples 1-6 were used as positive electrodes, and lithium sheets were used as negative electrodes. - 1 A solution of LiPF6 in ethylene carbonate / ethyl methyl carbonate / dimethyl carbonate (mass ratio of 1:1:1) was used as the electrolyte, and a porous polypropylene film (Celgard 2300) was used as the separator. CR2032 button half-cells were prepared and their initial discharge capacity was tested. The results are listed in Table 2.

[0125] The cycling performance of the materials of Example 2 and Comparative Example 1 was tested, and the results were as follows: Figure 5 The test method is as follows: the charge and discharge voltage range is 2.75-4.3V; the charge and discharge rate is 0.1C for the first 4 times and 0.5C for the 5th and subsequent times.

[0126] Table 1

[0127]

[0128] In Table 1, A1 is the atomic fraction of phosphorus on the surface of the particle; A2 is the atomic fraction of sulfur on the surface of the particle; A is the sum of the atomic fractions of phosphorus and sulfur on the surface of the particle; D1 is the total atomic fraction of phosphorus in the bulk phase of the particle, D2 is the total atomic fraction of sulfur in the bulk phase of the particle, and D is the sum of the total atomic fractions of phosphorus and sulfur in the bulk phase of the particle.

[0129] Table 2

[0130]

[0131] According to the data in Tables 1 and 2, the phosphorus and sulfur elements in the high-nickel ternary material prepared by the method of the present application are mainly distributed on the surface of the material. When it is used as the positive electrode of a lithium-ion battery, compared with the high-nickel ternary material doped with only sulfur (Comparative Example 3), only phosphorus (Comparative Example 2), and no doping element (Comparative Example 1), the surface phosphorus-sulfur co-doped high-nickel ternary material of the present application can still maintain a higher first discharge capacity after placement, and the capacity retention rate of the first discharge after 45 days in the air is 91.4-93.7%; and according to Figure 5 It can be seen that compared with the high-nickel ternary material without doped elements (Comparative Example 1), the material of the present application shows excellent capacity retention after 300 cycles, which shows that the material prepared in the present application has lower air sensitivity and longer storage period, and good cycle performance.

[0132] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within 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 scope of protection of the present disclosure.

[0133] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0134] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing a surface phosphorus-sulfur co-doped high nickel ternary material, characterized in that: The method comprises the following steps: S1: mixing a lithium source and a high-nickel ternary precursor and performing a first heat treatment in an oxygen atmosphere or an air atmosphere to obtain a first solid material; S2, under an inert atmosphere, subjecting the first non-metallic source and the first solid material to a second heat treatment to obtain a second solid material; S3, under an inert atmosphere, subjecting the second non-metallic source and the second solid material to a third heat treatment; Wherein, the first non-metallic source is a phosphorus source, and the second non-metallic source is a sulfur source; Alternatively, the first non-metal source is a sulfur source, and the second non-metal source is a phosphorus source; The molar ratio of the sulfur source calculated as sulfur element to the first solid material is (0.1-10):10; The molar ratio of the phosphorus source to the first solid material, calculated as phosphorus element, is (0.1-10):10; In step S2 and step S3, the second heat treatment and the third heat treatment are performed by calcination. The conditions of the second heat treatment and the third heat treatment are the same or different and independently include: a time of 1-5 hours and a temperature of 200-550° C.; The surface phosphorus-sulfur co-doped high nickel ternary material has the following scanning electron microscope energy spectrum and X-ray photoelectron spectroscopy characteristics: A1 is 0.1-5%, A2 is 0.1-5%, A=A1+A2, A is 0.2-10%; Based on the total number of atoms of all elements on the surface of the particle, A1 is the atomic ratio of phosphorus on the surface of the particle; A2 is the atomic ratio of sulfur on the surface of the particle; A is the sum of the atomic percentages of phosphorus and sulfur on the surface of the particle; D1 is 0.01-2.5%, D2 is 0.01-2.5%, D=D1+D2, D is 0.02-5%; Based on the total number of atoms of all elements in the particle bulk phase, D1 is the total atomic ratio of phosphorus in the particle bulk phase; D2 is the total atomic percentage of sulfur in the bulk phase of the particle; D is the sum of the total atomic percentages of phosphorus and sulfur in the particle bulk phase; The ratio of A to D is 2-20.

2. The method according to claim 1, wherein The chemical formula of the high nickel ternary precursor is Ni x Co y Mn z (OH)2, x+y+z=1, 0.6≤x≤0.9, 0.05≤y≤0.2, 0.05≤z≤0.

2.

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

4. The method according to claim 1, wherein The lithium source includes one or more of lithium hydroxide, lithium carbonate and lithium nitrate; The phosphorus source includes one or more of sodium hypophosphite, ammonium hypophosphite and red phosphorus; The sulfur source includes one or more of elemental sulfur, ammonium sulfide and ammonium hydrogensulfide.

5. The method according to claim 1, wherein In step S1, the first heat treatment is performed by calcination, and the conditions of the first heat treatment include: a time of 10-20 hours and a temperature of 600-850°C; In step S2 and step S3, the inert atmosphere includes one or more of nitrogen, helium and argon.

6. The method according to claim 1, wherein Step S2 and step S3 are performed in a tube furnace, the first non-metallic source and the second non-metallic source are placed upstream of the tube furnace, and the first solid material and the second solid material are placed downstream of the tube furnace.

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

8. The surface phosphorus-sulfur co-doped high nickel ternary material according to claim 7, wherein: The surface phosphorus and sulfur co-doped high-nickel ternary material contains particles with the chemical formula Li q Ni x Co y Mn z O p P m S n where x + y + z = 1, 0.6 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.2, 0.05 ≤ z ≤ 0.2, 0.8 ≤ q ≤ 1.2, 1.8 ≤ p ≤ 2.2, 0 < m ≤ 0.1, 0 < n ≤ 0.1; wherein, phosphorus and sulfur elements are doped on the surface of the particles.

9. A lithium-ion battery, characterized in that: The lithium-ion battery comprises a positive electrode, an electrolyte and a negative electrode, wherein the positive electrode comprises the surface phosphorus-sulfur co-doped high-nickel ternary material according to claim 7 or 8.

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