A surface phosphorus-doped high-nickel ternary material, a preparation method thereof and a lithium ion battery comprising the same

Abstract

The present disclosure relates to a surface phosphorus-doped high-nickel ternary material, a preparation method thereof and a lithium ion battery comprising the same, the surface phosphorus-doped high-nickel ternary material comprising particles of a chemical formula of Li q Ni x Co y Mn z O p P m , 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, and the phosphorus element is doped on the surface of the material. The surface phosphorus-doped high-nickel ternary material prepared by the method of the present disclosure has a stable layered structure, and the phosphorus element doping on the surface can play a coating effect to slow down the corrosion of the electrolyte on the material, thereby effectively improving the electrochemical cycle stability of the material.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of lithium ion battery ternary material preparation, in particular, to a surface phosphorus-doped high-nickel ternary material, a preparation method thereof and a lithium ion battery comprising the same. BACKGROUND

[0002] High-nickel ternary materials (Ni≥0.6) have the advantages of low cost and high specific capacity, and are currently the mainstream positive electrode material of high-energy-density lithium ion power batteries. With the increase of nickel content, the discharge specific capacity of the ternary material increases, but Ni 2+ and Li + have more serious dislocation phenomena (both have similar ionic radii), resulting in significantly deteriorated cycle performance and thermal stability. In addition, when the Ni content is ≥0.6, the material has serious water absorption, which not only affects the coating effect, but also easily produces surface residual alkali (including residual LiOH and Li2CO3), leading to surface side reactions and safety hazards. In order to reduce the problems of ion mixing and surface residual alkali, the effective method is to modify the material by body phase ion doping and surface coating. Body phase ion doping can stabilize the layered structure, reduce the degree of cation mixing, and improve the structural stability of the material; while surface coating can reduce the direct contact of the material with the electrolyte, avoid the occurrence of electrode side reactions, and improve the interface stability of the material.

[0003] There are a large number of literature reports on body phase ion doping and surface coating, but there are also some problems with these two modification methods. On the one hand, the implementation of body phase ion doping often requires the introduction of additional ions in the precursor, increasing the synthesis difficulty of the precursor; on the other hand, the modification steps of surface coating are complicated, and the capacity loss of the original ternary material is easily caused. Therefore, developing a more effective method to fully utilize the advantages of both methods can further improve the electrochemical performance of the material, which is also the difficulty and hotspot of the current modification. Among them, surface ion doping can combine the advantages of body phase ion doping and surface coating, but the distribution of the doped ions is difficult to control. In addition, the current research on surface doping mainly focuses on metal elements (such as vanadium ion surface doping of CN110176587A, Ta surface doping of CN113066978A, etc.), while surface doping of non-metal elements is rarely reported, so the method of surface doping of non-metal elements needs further research. SUMMARY

[0004] The purpose of the present disclosure is to provide a surface phosphorus-doped high-nickel ternary material, a preparation method thereof and a lithium ion battery comprising the same. The phosphorus element in the phosphorus-doped high-nickel ternary material is mainly doped on the surface of the material, which not only can increase the stability of the layered structure, but also can play a coating effect, slow down the corrosion of the electrolyte on the material, and effectively improve the electrochemical cycle stability of the material.

[0005] To achieve the above object, the first aspect of the present disclosure provides a surface phosphorus-doped high-nickel ternary material, which comprises particles of chemical formula Li q Ni x Co y Mn z O p P m , 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; wherein the surface phosphorus-doped high-nickel ternary material has the following scanning electron microscope energy spectrum and X-ray photoelectron spectrum characteristics:

[0006] A is 0.1-5%;

[0007] A is the atomic percentage of phosphorus on the surface of the particles based on the total number of atoms of all elements on the surface of the particles;

[0008] D is 0.01-2.5%;

[0009] D is the total atomic percentage of phosphorus in the particle phase based on the total number of atoms of all elements in the particle phase;

[0010] The ratio of A to D is 2-20.

[0011] Optionally, the ratio of A to D is 4-10.

[0012] The second aspect of the present disclosure provides a method for preparing a surface phosphorus-doped high-nickel ternary material, which comprises the following steps:

[0013] (1) mixing a lithium source with a high-nickel ternary material precursor, and performing first heat treatment under an oxygen atmosphere or an air atmosphere to obtain a first solid material;

[0014] (2) performing second heat treatment on the first solid material with a phosphorus source under an inert atmosphere;

[0015] (3) performing third heat treatment on the pre-product obtained in step (2) under an oxygen atmosphere or an air atmosphere.

[0016] 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.

[0017] Optionally, the lithium source comprises one or more of lithium hydroxide, lithium carbonate and lithium nitrate.

[0018] The phosphorus source includes one or more of sodium hypophosphite, ammonium hypophosphite and red phosphorus.

[0019] Optionally, the molar ratio of the lithium source to the high-nickel ternary precursor in terms of lithium element is (0.8-1.2):1.

[0020] The molar ratio of the phosphorus source to the first solid material in terms of phosphorus element is (0.05-5):10.

[0021] Optionally, in step (1), the first heat treatment is performed by calcination, and the first heat treatment is performed under conditions including a time of 10-20h and a temperature of 600-850℃.

[0022] In step (2), the second heat treatment is performed by calcination, and the second heat treatment is performed under conditions including a time of 1-5h and a temperature of 200-450℃.

[0023] In step (3), the third heat treatment is performed by calcination, and the third heat treatment is performed under conditions including a time of 3-8h and a temperature of 600-850℃.

[0024] Optionally, step (2) is performed in a tube furnace, and the phosphorus source is placed upstream of the tube furnace and the first solid material is placed downstream of the tube furnace.

[0025] The phosphorus source generates a fluid containing phosphorus element under the action of high temperature, and the fluid containing phosphorus element flows downstream of the tube furnace and reacts with the first solid material.

[0026] The third aspect of the present disclosure provides a surface-phosphorus-doped high-nickel ternary material prepared by the method of the second aspect of the present disclosure.

[0027] The fourth aspect of the present disclosure provides a lithium ion battery, which includes a positive electrode, an electrolyte and a negative electrode, and the positive electrode contains the surface-phosphorus-doped high-nickel ternary material of the first aspect or the third aspect of the present disclosure.

[0028] Through the above technical solution, the surface-phosphorus-doped high-nickel ternary material is obtained by first obtaining a first solid material through high-temperature solid-phase reaction and then performing gas-phase phosphorization and calcination. The surface-phosphorus-doped high-nickel ternary material has good stability of layered structure, and the phosphorus element is mainly doped on the surface of the particles, which can play a coating effect and slow down the corrosion of the electrolyte on the material, thereby effectively improving the electrochemical cycle stability of the material.

[0029] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, illustrate the present disclosure and, together with the specific embodiments described below, serve to explain the present disclosure, but do not constitute a limitation on the present disclosure. In the drawings:

[0031] Figure 1 Electrochemical cycle curves of high-nickel ternary materials A1 and D1 prepared for Example 1 and Comparative Example 1 of the present application.

[0032] Figure 2 Electrochemical cycle curves of high-nickel ternary materials A2 and D2 prepared for Example 2 and Comparative Example 2 of the present application.

[0033] Figure 3 Electrochemical cycle curves of high-nickel ternary materials A3 and D3 prepared for Example 3 and Comparative Example 3 of the present application.

[0034] Figure 4 X-ray diffraction patterns of high-nickel ternary materials A1 and D1 prepared for Example 1 and Comparative Example 1 of the present application.

[0035] Figure 5 X-ray diffraction patterns of high-nickel ternary materials A2 and D2 prepared for Example 2 and Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0036] The specific embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present disclosure, and are not intended to limit the present disclosure.

[0037] The first aspect of the present disclosure provides a surface phosphorus-doped high-nickel ternary material, the surface phosphorus-doped high-nickel ternary material comprising particles of a chemical formula of Li q Ni x Co y Mn z O p P m , 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; wherein the surface phosphorus-doped high-nickel ternary material has the following scanning electron microscope energy spectrum and X-ray photoelectron spectrum characteristics:

[0038] A is 0.1-5%;

[0039] A is the atomic percentage of phosphorus element on the surface of the particles based on the total number of atoms of all elements on the surface of the particles;

[0040] D is 0.01-2.5%;

[0041] D is the total atomic percentage of phosphorus in the particle phase, based on the total number of atoms of all elements in the particle phase;

[0042] The ratio of A to D is 2-20.

[0043] In an embodiment of the present disclosure, A is 1-4%, preferably 2-3.5%, and further preferably 2.4-3.2%; D is 0.1-2%, preferably 0.2-1%, and further preferably 0.25-0.7%.

[0044] In an embodiment of the present disclosure, the ratio of A to D is 2-15, further preferably 4-13, and more preferably 4-10.

[0045] In the present disclosure, the content of phosphorus on the surface of the material of the present application is higher than that in the bulk phase, based on the total amount of phosphorus in the particle, and the phosphorus in the material of the present application is doped on the surface of the material.

[0046] In the present disclosure, the "atomic percentage of phosphorus on the surface of the material" refers to the proportion of the number of atoms of phosphorus on the surface of the particle to the total number of atoms of all elements on the surface; the "total atomic percentage of phosphorus in the bulk phase of the material" refers to the proportion of the total number of atoms of phosphorus in the particle phase to the total number of atoms of all elements; all elements include lithium, nickel, cobalt, manganese, oxygen and phosphorus.

[0047] In the above preferred embodiment, the phosphorus element of the surface phosphorus-doped high-nickel ternary material of the present disclosure is mainly doped on the surface of the particle, which has a coating effect on the internal material, avoids corrosion of the electrolyte on the material, and can still maintain a stable structure and a high capacity retention rate under a long-term electrochemical cycle.

[0048] In the present disclosure, the I (003) / I (104) of the surface phosphorus-doped high-nickel ternary material is 1.0-1.5, and preferably 1.1-1.4; wherein, I (003) represents the diffraction peak intensity of the (003) crystal face in the X-ray diffraction pattern of the surface phosphorus-doped high-nickel ternary material; and I (104) represents the diffraction peak intensity of the (104) crystal face in the X-ray diffraction pattern of the surface phosphorus-doped high-nickel ternary material.

[0049] The second aspect of the present disclosure provides a method for preparing a surface phosphorus-doped high-nickel ternary material, which comprises the following steps:

[0050] (1) mixing a lithium source with a high-nickel ternary material precursor, and performing a first heat treatment in an oxygen atmosphere or an air atmosphere to obtain a first solid material;

[0051] (2) a second heat treatment of the phosphorus source and the first solid material under an inert atmosphere;

[0052] (3) a third heat treatment of the pre-product obtained in step (2) under an oxygen atmosphere or an air atmosphere.

[0053] In order to make the prepared material have a higher capacity, in an 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, 0.1≤y≤0.15, 0.1≤z≤0.15.

[0054] In the present disclosure, the average particle size of the high-nickel ternary precursor is 5-15 μm, for example, can be 10 μm.

[0055] In an 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.

[0056] In an embodiment of the present disclosure, the molar ratio of the lithium source to the high-nickel ternary precursor in terms of lithium element is (0.8-1.2):1, preferably (0.95-1.15):1; the molar ratio of the phosphorus source to the first solid material in terms of phosphorus element is (0.05-5):10, preferably (0.5-5):10, further preferably (1-5):10. Satisfying the above ratios can realize effective surface doping of phosphorus elements on the basis of obtaining a high-nickel ternary material with better performance.

[0057] In an embodiment of the present disclosure, in step (1), the first heat treatment is roasting, and the conditions of the first heat treatment include: a time of 10-20 h and a temperature of 600-850 ℃; preferably, a time of 12-18 h and a temperature of 700-800 ℃. In step (2), the second heat treatment is roasting, and the conditions of the second heat treatment include: a time of 1-5 h and a temperature of 200-450 ℃; preferably, a time of 1.5-4 h and a temperature of 250-400 ℃. In step (3), the third heat treatment is roasting, and the conditions of the third heat treatment include: a time of 3-8 h and a temperature of 600-850 ℃; preferably, a time of 4-7 h and a temperature of 700-800 ℃.

[0058] In order to remove surface impurities, in one embodiment of the present disclosure, the method further comprises: stirring and mixing the second solid material obtained in step (2) with water at a mass ratio of 1:(0.5-2) for 5-80 min, filtering and drying to obtain a pre-product. Further, the drying conditions include: time of 0.5-5 h and temperature of 80-100 °C.

[0059] In the present disclosure, the inert atmosphere includes one or more of nitrogen, argon and helium.

[0060] In one embodiment of the present disclosure, step (2) is carried out in a tube furnace, the phosphorus source is placed upstream of the tube furnace, and the first solid material is placed downstream of the tube furnace. Wherein, upstream and downstream are defined along the flow direction of the phosphorus source, the phosphorus source placed upstream generates a phosphorus element-containing fluid, such as phosphine and / or gaseous phosphorus, under the action of high temperature, which flows to the downstream and reacts with the first solid material. The phosphorus element-containing fluid reacts with the surface metal elements in the first solid material to form metal phosphide (MP) or / and metal phosphorus oxide (MPOx, M represents a metal element, x>0), forming a structure with surface phosphorus doping.

[0061] The third aspect of the present disclosure provides a surface phosphorus-doped high-nickel ternary material prepared by the method of the second aspect of the present disclosure.

[0062] In the present disclosure, the phosphorus element doping of the above-mentioned surface phosphorus-doped high-nickel ternary material is on the surface of the particles, and the content of phosphorus element on the surface is higher than that in the bulk phase based on the total amount of phosphorus element in the particles, further, by scanning electron microscopy and X-ray photoelectron spectroscopy, the ratio of the atomic percentage of phosphorus element on the surface of the particles to the total atomic percentage of phosphorus element in the bulk phase of the particles is 2-20, preferably 2-15, further preferably 4-13, and more preferably 4-10.

[0063] The fourth aspect of the present disclosure provides a lithium ion battery, which comprises a positive electrode, an electrolyte and a negative electrode, wherein the positive electrode comprises the surface phosphorus-doped high-nickel ternary material of the first aspect or the third aspect of the present disclosure.

[0064] Further, the negative electrode material of the above-mentioned lithium ion battery, for example, comprises one or more of lithium sheet, carbon material and silicon-carbon composite material, and the electrolyte, for example, comprises one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, lithium hexafluorophosphate and dimethyl carbonate. This is conventional in the art, and no specific requirements are made herein.

[0065] The reagents used in the examples and comparative examples of the present application are commercially available.

[0066] The testing instrument model of the scanning electron microscope energy spectrum is FEI QUANTA400, and the method is accelerating voltage of 20kV.

[0067] The testing instrument model of the X-ray photoelectron spectrum is American Thermo Fisher Thermo ESCALAB 250, and the method is using Al Kα X-ray emission light source.

[0068] The testing instrument model of the X-ray diffraction pattern is the X-ray powder diffractometer of American Philips Company, and the method is using Cu target anode Kα radiation source, step width of 0.02°, scanning speed of 2° / min, 2θ=10°-80°.

[0069] Example 1

[0070] The surface phosphorus-doped high-nickel ternary material of the application is prepared by the following steps:

[0071] (1) LiOH·H2O and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 are mixed uniformly on a planetary ball mill in a molar ratio of 1.05:1, the obtained mixture is loaded into a sagger, and first heat treatment is carried out under an oxygen atmosphere, the temperature is 750℃, and the time is 15h, the obtained solid product is crushed and sieved to obtain a first solid material;

[0072] (2) Under a nitrogen atmosphere, sodium hypophosphite and the first solid material are respectively placed in the upstream and downstream of a tube furnace in a molar ratio of 0.5:10, second heat treatment is carried out, the temperature is 350℃, and the time is 2h, after cooling to room temperature, stirring and mixing with water in a mass ratio of 1:1 for 30min, stirring, filtering and drying at 120℃ for 4h, a pre-product is obtained;

[0073] (3) The pre-product is loaded into a sagger, third heat treatment is carried out under an oxygen atmosphere, the temperature is 750℃, and the time is 5h, the obtained material is crushed and sieved to obtain a surface phosphorus-doped high-nickel ternary material A1.

[0074] The surface phosphorus-doped high-nickel ternary material A1 prepared in Example 1 is detected by scanning electron microscope energy spectrum, X-ray photoelectron spectrum and XRD diffraction test, and the results are shown in Table 1.

[0075] Example 2

[0076] (1) LiOH·H2O and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1LiOH·H2O and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2are mixed uniformly on a planetary ball mill in a molar ratio of 1.08:1, the obtained mixture is loaded into a crucible, a first heat treatment is carried out under an oxygen atmosphere, the temperature is 700℃, and the time is 15h, the obtained solid product is crushed and sieved to obtain a first solid material;

[0077] (2) Under an argon atmosphere, sodium hypophosphite and the first solid material are placed in the upstream and downstream of a tube furnace respectively in a molar ratio of 1:10, a second heat treatment is carried out, the temperature is 400℃, and the time is 2h, after cooling to room temperature, stirring and mixing with water in a mass ratio of 1:1 for 30min, stirring, filtering and drying at 120℃ for 4h, a pre-product is obtained;

[0078] (3) The pre-product is loaded into a crucible, a third heat treatment is carried out under an oxygen atmosphere, the temperature is 700℃, and the time is 5h, the obtained material is crushed and sieved to obtain a surface phosphorus-doped high-nickel ternary material A2.

[0079] The surface phosphorus-doped high-nickel ternary material A2 prepared in Example 2 is subjected to scanning electron microscope energy spectrum, X-ray photoelectron spectrum detection and XRD diffraction test, and the results are shown in Table 1.

[0080] Example 3

[0081] (1) LiOH·H2O and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2are mixed uniformly on a planetary ball mill in a molar ratio of 1.08:1, the obtained mixture is loaded into a crucible, a first heat treatment is carried out under an oxygen atmosphere, the temperature is 700℃, and the time is 15h, the obtained solid product is crushed and sieved to obtain a first solid material;

[0082] (2) Under an argon atmosphere, sodium hypophosphite and the first solid material are placed in the upstream and downstream of a tube furnace respectively in a molar ratio of 1:10, a second heat treatment is carried out, the temperature is 400℃, and the time is 2h, after cooling to room temperature, stirring and mixing with water in a mass ratio of 1:1 for 30min, stirring, filtering and drying at 120℃ for 4h, a pre-product is obtained;

[0083] (3) The pre-product is loaded into a crucible, a third heat treatment is carried out under an oxygen atmosphere, the temperature is 700℃, and the time is 5h, the obtained material is crushed and sieved to obtain a surface phosphorus-doped high-nickel ternary material A2.

[0084] The surface phosphorus-doped high-nickel ternary material A2 prepared in Example 2 is subjected to scanning electron microscope energy spectrum, X-ray photoelectron spectrum detection and XRD diffraction test, and the results are shown in Table 1.

[0085] Example 4

[0086] Surface phosphorus-doped high-nickel ternary material A4 was prepared by the same method as Example 1, except that the phosphorus source was ammonium hypophosphite.

[0087] The surface phosphorus-doped high-nickel ternary material A4 prepared in Example 4 was subjected to scanning electron microscope energy spectrum, X-ray photoelectron spectrum detection and XRD diffraction test, and the results are shown in Table 1.

[0088] Example 5

[0089] Surface phosphorus-doped high-nickel ternary material A5 was prepared by the same method as Example 1, except that the second heat treatment time was 3 h and the temperature was 400°C.

[0090] The surface phosphorus-doped high-nickel ternary material A5 prepared in Example 5 was subjected to scanning electron microscope energy spectrum, X-ray photoelectron spectrum detection and XRD diffraction test, and the results are shown in Table 1.

[0091] Comparative Example 1

[0092] High-nickel ternary material D1 was prepared by the following method:

[0093] (1) LiOH H2O and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 were mixed uniformly in a planetary ball mill at a molar ratio of 1.05:1, the obtained mixture was loaded into a sagger, and first heat treatment was carried out under an oxygen atmosphere at a temperature of 750°C for 15 h. The obtained solid product was crushed and sieved to obtain a first solid material;

[0094] (2) The first solid material was introduced into a tube furnace under a nitrogen atmosphere, and second heat treatment was carried out at a temperature of 350°C for 2 h. After cooling to room temperature, the product was stirred and mixed with water at a mass ratio of 1:1 for 30 min, stirred and filtered, and dried at 120°C for 4 h to obtain a pre-product;

[0095] (3) The pre-product was loaded into a sagger, and third heat treatment was carried out under an oxygen atmosphere at a temperature of 750°C for 5 h. The obtained material was crushed and sieved to obtain high-nickel ternary material D1.

[0096] The high-nickel ternary material D1 prepared in Comparative Example 1 was subjected to scanning electron microscope energy spectrum, X-ray photoelectron spectrum detection and XRD diffraction test, and the results are shown in Table 1.

[0097] Comparative Example 2

[0098] (1) LiOH H2O and high-nickel ternary precursor Ni 0.8 Co 0.1Mn 0.1 LiOH·H2O and high-nickel ternary precursor Ni

[0099] (2) The first solid material was introduced into a tube furnace under an argon atmosphere, and a second heat treatment was performed at a temperature of 400℃ for 2h. After cooling to room temperature, the product was mixed with water at a mass ratio of 1:1 for 30min, and then stirred, filtered, and dried at 120℃ for 4h to obtain a pre-product;

[0100] (3) The pre-product was loaded into a crucible, and a third heat treatment was performed under an oxygen atmosphere at a temperature of 700℃ for 5h. The obtained material was crushed and sieved to obtain high-nickel ternary material D2.

[0101] The high-nickel ternary material D2 prepared in Comparative Example 2 was subjected to scanning electron microscope energy spectrum, X-ray photoelectron spectrum detection, and XRD diffraction test, and the results are shown in Table 1.

[0102] Comparative Example 3

[0103] (1) LiOH·H2O and high-nickel ternary precursor Ni 0.8 Co 0.1 Mn 0.1 LiOH·H2O and high-nickel ternary precursor Ni

[0104] (2) The first solid material was introduced into a tube furnace under an argon atmosphere, and a second heat treatment was performed at a temperature of 400℃ for 2h. After cooling to room temperature, the product was mixed with water at a mass ratio of 1:1 for 30min, and then stirred, filtered, and dried at 120℃ for 4h to obtain a pre-product;

[0105] (3) The pre-product was loaded into a crucible, and a third heat treatment was performed under an oxygen atmosphere at a temperature of 700℃ for 5h. The obtained material was crushed and sieved to obtain high-nickel ternary material D2.

[0106] The high-nickel ternary material D3 prepared in Comparative Example 3 was subjected to scanning electron microscope energy spectrum, X-ray photoelectron spectrum detection, and XRD diffraction test, and the results are shown in Table 1.

[0107] In the above Examples 1-5 and Comparative Examples 1-3, the first heat treatment, the second heat treatment, and the third heat treatment were all performed by calcination, and the high-nickel ternary precursor Ni0.8 Co 0.1 Mn 0.1 The average particle size of (OH)2 is 10 μm, and the test method is to use a Malvern laser particle size analyzer.

[0108] Table 1

[0109] Example / Comparative Example Number Material Number Chemical Formula A，％ D，％ A / D I 003 / I 104 ]]> Example 1 A1 Li 1.01 Ni 0.8 Co 0.1 Mn 0.1 O 2.002 P 0.008 ]]> 2.13 0.19 11.2 1.25 Example 2 A2 Li 1.03 Ni 0.8 Co 0.1 Mn 0.1 O 2.029 P 0.011 ]]> 2.5 0.26 9.6 1.30 Example 3 A3 Li 1.1 Ni 0.8 Co 0.1 Mn 0.1 O2 .074 P 0.026 ]]> 3.01 0.61 4.9 1.33 Example 4 A4 Li 1.01 Ni 0.8 Co 0.1 Mn 0.1 O 2.006 P 0.004 ]]> 1.4 0.11 12.7 1.24 Example 5 A5 Li 1.01 Ni 0.8 Co 0.1 Mn 0.1 O 2.001 P 0.009 ]]> 2.25 0.22 10.2 1.27 Comparative Example 1 D1 Li 1.01 Ni 0.8 Co 0.1 Mn 0.1 O 2.01 ]]> 0 0 - 1.21 Comparative Example 2 D2 Li 1.03 Ni 0.8 Co 0.1 Mn 0.1 O 2.03 ]]> 0 0 - 1.24 Comparative Example 3 D3 Li 1.1 Ni 0.8 Co 0.1 Mn 0.1 O 2.1 ]]> 0 0 - 1.28

[0110] In Table 1, A is the atomic percentage of phosphorus element on the surface of the particles; D is the total atomic percentage of phosphorus element in the particle phase.

[0111] According to the data in Table 1, under the same conditions, the I (003) / I (104) value of the high-nickel ternary material doped with surface phosphorus element is higher than that of the high-nickel ternary material without phosphorus element doping, indicating that the Li / Ni mixing degree is small, the layered structure is stable, and the material has higher cycle stability.

[0112] Test Examples 1-6

[0113] The high-nickel ternary materials of Examples 1-3 and Comparative Example 1-3 were used as positive electrodes, lithium pieces were used as negative electrodes, 1 mol·L - 1 A solution of LiPF6 in ethylene carbonate / methyl ethyl carbonate / dimethyl carbonate (mass ratio 1:1:1) was used as an electrolyte, and a porous polypropylene film (Celgard 2300) was used as a separator to prepare CR2032 button-type half batteries, and the cycle performance was tested, and the results are shown in Table 2. The test method is as follows: the charge and discharge voltage range is 2.75-4.3 V; the charge and discharge rate is 0.1 C for the first 4 times and 0.5 C after 5 times.

[0114] Figure 1 The electrochemical cycle curves of the high-nickel ternary materials A1 and D1 prepared in Example 1 and Comparative Example 1 of the present application.

[0115] Figure 2 The electrochemical cycle curves of the high-nickel ternary materials A2 and D2 prepared in Example 2 and Comparative Example 2 of the present application.

[0116] Figure 3 The electrochemical cycle curves of the high-nickel ternary materials A3 and D3 prepared in Example 3 and Comparative Example 3 of the present application.

[0117] Figure 4 The X-ray diffraction patterns of the high-nickel ternary materials A1 and D1 prepared in Example 1 and Comparative Example 1 of the present application.

[0118] Figure 5 The X-ray diffraction patterns of the high-nickel ternary materials A2 and D2 prepared in Example 2 and Comparative Example 2 of the present application.

[0119] Table 2

[0120]

[0121] According to the data in Table 2, the phosphorus element in the high-nickel ternary material prepared by the method of the application is mainly distributed on the surface of the material. As the positive electrode of the lithium ion battery, the surface phosphorus-doped high-nickel ternary material of the application has no obvious capacity loss after 200 cycles, showing excellent capacity retention rate, which indicates that the material prepared by the application has good cycle performance.

[0122] The preferred embodiments of the present disclosure are described in detail above in combination with the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Within the technical concept range of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all belong to the protection range of the present disclosure.

[0123] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combinations are not described again in the present disclosure.

[0124] In addition, any combination of various different embodiments of the present disclosure can also be made, as long as it does not deviate from the idea of the present disclosure, and it should also be considered as disclosed by the present disclosure.

Claims

1. A method of preparing a surface phosphorus doped high nickel ternary material, characterized in that, The method comprises the following steps: (1) mixing a lithium source with a high-nickel ternary material precursor, and performing first heat treatment under an oxygen atmosphere or an air atmosphere to obtain a first solid material; (2) performing second heat treatment on the first solid material and a phosphorus source under an inert atmosphere; (3) performing third heat treatment on a pre-product obtained in step (2) under an oxygen atmosphere or an air atmosphere; In step (2), the second heat treatment is performed by calcination, and the second heat treatment is performed at a temperature of 200-450°C for 1-5h; In step (3), the third heat treatment is performed by calcination, and the third heat treatment is performed at a temperature of 750-850°C for 3-8h; 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; The molar ratio of the phosphorus source to the first solid material is (0.05-5):10 in terms of phosphorus element; Step (2) is performed in a tube furnace, the phosphorus source is placed in the upstream of the tube furnace, and the first solid material is placed in the downstream of the tube furnace; The phosphorus source generates a fluid containing phosphorus element under the action of high temperature, and the fluid containing phosphorus element flows to the downstream of the tube furnace and reacts with the first solid material.

2. The method of claim 1, wherein, The lithium source comprises one or more of lithium hydroxide, lithium carbonate and lithium nitrate; The phosphorus source comprises one or more of sodium hypophosphite, ammonium hypophosphite and red phosphorus.

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

4. The method of claim 1, wherein, In step (1), the first heat treatment is performed by calcination, and the first heat treatment is performed at a temperature of 600-850°C for 10-20h.

5. A surface phosphorus-doped high-nickel ternary material prepared by the method in any one of claims 1-4.

6. The surface phosphorus doped high nickel ternary material of claim 5, wherein, The surface phosphorus-doped high-nickel ternary material comprises particles with a chemical formula of Li q Ni x Co y Mn z O p P m 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 The surface phosphorus-doped high-nickel ternary material has the following scanning electron microscope energy spectrum and X-ray photoelectron spectrum characteristics: A is 0.1-5%; A is the atomic percentage of phosphorus element on the surface of the particles based on the total number of atoms of all elements on the surface of the particles; D is 0.01-2.5%; D is the total atomic percentage of phosphorus element in the particle phase based on the total number of atoms of all elements in the particle phase; The ratio of A to D is 2-20.

7. The surface phosphorus doped high nickel ternary material of claim 6, wherein, The ratio of A to D is 4-10.

8. A lithium-ion battery, characterized by, The lithium ion battery comprises a positive electrode, an electrolyte and a negative electrode, and the positive electrode comprises the surface phosphorus-doped high-nickel ternary material in any one of claims 5-7.

Images