Molybdenum-doped and lithium molybdate-coated single-crystal ultrahigh-nickel binary lithium ion battery positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a molybdenum-doped and lithium molybdate-coated single-crystal ultrahigh-nickel binary lithium ion battery positive electrode material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing a nickel-cobalt binary precursor with a lithium salt, carrying out high-temperature calcination to obtain a lithium-deficient single-crystal ultrahigh-nickel binary positive electrode material, mixing the lithium-deficient single-crystal ultrahigh-nickel binary positive electrode material with an aqueous solution of ammonium molybdate, drying, adding a small amount of lithium salt, and carrying out secondary high-temperature calcination to obtain the lithium-deficient single- and finally, the molybdenum-doped and lithium molybdate-coated single-crystal ultrahigh-nickel binary lithium ion battery positive electrode material is obtained. According to the preparation method disclosed by the invention, a lithium molybdate surface coating layer and a Mo-O bond with high bond energy are introduced and cooperate with each other to stabilize a lattice structure and inhibit lattice oxygen evolution and harmful phase change of the material in a circulating process while an excellent single crystal particle morphology is maintained, so that the comprehensive electrochemical performance of the material is improved, and the preparation method has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material, and a preparation method and application thereof. Background Art

[0002] With the rapid development of industries such as new energy vehicles and new energy storage, driven by continuous progress in related technologies and support from national industrial policies, the fields of power batteries and energy storage batteries are booming. my country's lithium-ion battery industry is entering a new phase of vigorous development. This is accompanied by an increasing demand for lithium-ion batteries with high energy density and high power output. Consequently, research on high-performance cathode materials has become a focus of considerable attention. Among various lithium-ion battery cathode materials, ultra-high nickel layered oxide cathodes offer high energy density and are the development direction for next-generation lithium-ion battery cathode materials. Currently, common cathodes have a polycrystalline morphology, consisting of secondary particles formed by the agglomeration of primary particles. However, polycrystalline ultra-high nickel cathode materials suffer from intergranular cracking, leading to numerous side reactions, poor cycling stability, and a low safety factor.

[0003] Single-crystal ultra-high nickel cathode materials can avoid the occurrence of intergranular cracks, reduce side reactions at the solid-liquid interface, and improve bulk and interfacial stability. However, single-crystal structures cannot fundamentally solve the problem of structural degradation from the surface to the bulk of the material. In addition, single-crystal cathodes will still experience intragranular cracks under high voltage. As the cycle progresses, the cracks extend to the material surface, causing the new surface to come into contact with the electrolyte, exacerbating capacity decay.

[0004] To solve the above problems, surface coating, element doping, core-shell structure, concentration gradient structure and other methods can be used. An inert coating is coated on the surface of the positive electrode material to physically isolate the positive electrode material from contact with the electrolyte, reduce side reactions during charging and discharging, and improve the stability and safety of the material. However, this type of coating layer often reduces the capacity of the positive electrode and hinders the transmission of lithium ions at the electrode interface. By doping with elements such as Ti, Zr, and Mg, the change in unit cell parameters caused by the H2-H3 phase transition can be effectively reduced, thereby reducing anisotropic strain, and can also play a role in suppressing voltage attenuation and reducing transition metal dissolution. These methods have greatly improved the cycle stability of the material, but in high-voltage and long-cycle application scenarios, the problem of microcracks is still unavoidable.

[0005] Doping single-crystal ultra-high nickel cathode materials with the metal element Mo and coating them with the ion conductor Li2MoO4 can solve their shortcomings to a certain extent, improve the cycle stability and safety performance of single-crystal ultra-high nickel cathode materials, and improve the electrochemical performance of the cathode materials.

[0006] CN118833875A discloses a molybdenum-doped lithium nickelate cathode material produced by mixing and grinding a certain amount of nickel hydroxide, a lithium source, and ammonium molybdate, followed by high-temperature sintering in an oxygen atmosphere tube furnace. This method can suppress severe interfacial reactions between the cathode material and the electrolyte in solid-state batteries. However, the material produced by this method has a polycrystalline morphology and exhibits microcracks. Furthermore, the ammonium molybdate and precursor are mixed using physical grinding, resulting in uneven distribution of the doping element.

[0007] CN117038887A discloses a method of converting Ni 0.8 Co 0.1 Mn 0.1 A single-crystal, high-nickel ternary cathode material, coated with lithium molybdate and doped with molybdenum, is obtained by mixing an (OH)2 precursor, LiOH·H2O, and Li2MoO4 and calcining them at high temperature. This method simultaneously achieves single crystal formation, coating, and doping, avoiding structural damage during the washing process. However, this method directly uses Li2MoO4 as the Mo source, resulting in a mixing uniformity and consistency that is unsuitable for industrial applications. Furthermore, the nickel content of the prepared material only accounts for 80% of the transition metal elements, and materials with higher nickel contents have not been studied. Summary of the Invention

[0008] In response to the deficiencies in the prior art, the present invention aims to provide a molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material, as well as a preparation method and application thereof. While maintaining the excellent single-crystal particle morphology, the present invention introduces a lithium molybdate surface coating layer and a Mo-O bond with high bond energy. The two work together to stabilize the lattice structure, inhibit lattice oxygen precipitation and harmful phase changes of the material during the cycle process, thereby improving the comprehensive electrochemical performance of the material and having good application prospects.

[0009] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0010] A method for preparing a molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material comprises the following steps: using a nickel-cobalt binary hydroxide precursor as a raw material, mixing it with a lithium salt, and calcining it at high temperature to obtain a lithium-deficient single-crystal ultra-high nickel positive electrode material; then mixing it with a molybdenum source and a lithium salt, and calcining it at high temperature again to finally obtain a molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material.

[0011] The method for preparing the above-mentioned molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material comprises the following steps:

[0012] Step 1: Evenly mix the dried nickel-cobalt binary precursor with the lithium source, calcine them in stages in a tubular atmosphere furnace with flowing oxygen, heat them to 450-550°C, and keep them warm for 3-5 hours, then continue to heat them to 800-900°C, keep them warm for 20-24 hours, and finally cool them to room temperature with the furnace, grind and sieve them, and perform gas phase crushing to obtain a lithium-deficient single crystal ultra-high nickel positive electrode material;

[0013] Step 2: Take the lithium-deficient single crystal ultra-high nickel cathode material and (NH4)6Mo7O 24 ·4H2O aqueous solution, stirred for 0.5-1.5h, heated in a water bath to 55-65℃, continued stirring for 5.5-6.5h, then placed in a vacuum drying oven, dried at 75-85℃, ground and sieved to obtain surface-attached (NH4)6Mo7O 24 Lithium-deficient single crystal ultra-high nickel cathode material;

[0014] Step 3: Take the surface-attached (NH4)6Mo7O 24 The lithium-deficient single crystal ultra-high nickel positive electrode material is evenly mixed with a lithium source, calcined in stages in a tubular atmosphere furnace with flowing oxygen, heated to 450-550°C, and kept warm for 3-5 hours, then continued to heat to 650-850°C, kept warm for 8-12 hours, and finally cooled to room temperature with the furnace. After grinding and sieving, a molybdenum-doped and lithium molybdate-coated single crystal ultra-high nickel binary lithium-ion battery positive electrode material is obtained.

[0015] Preferably, the chemical formula of the ultra-high nickel binary precursor in step 1 is Ni 0.93 Co 0.07 (OH)2, the lithium source is at least one of lithium nitrate, lithium acetate, lithium carbonate and lithium hydroxide.

[0016] Preferably, the vacuum drying temperature of the nickel-cobalt binary precursor powder in step 1 is 60-100°C.

[0017] More preferably, the vacuum drying temperature of the binary precursor powder is 80°C.

[0018] Preferably, the dried nickel-cobalt binary precursor powder Ni 0.93 Co 0.07 (OH)2 and lithium source n(Ni+Co):nLi=1:1.1 (molar ratio).

[0019] Preferably, in step 2, (NH4)6Mo7O 24 The mass of the lithium-deficient single crystal ultra-high nickel cathode material mixed with 4H2O aqueous solution is 1-2g.

[0020] Preferably, in step 2, the lithium-deficient single crystal ultra-high nickel positive electrode material and (NH4)6Mo7O 24In 4H2O, n(Ni+Co):nMo=0.99:0.01 (molar ratio).

[0021] Preferably, in step 3, (NH4)6Mo7O is attached to the surface 24 The lithium-deficient single crystal ultra-high nickel positive electrode material and the lithium source have n(Ni+Co):nLi=0.9:0.1.

[0022] The molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material prepared by the above preparation method has Ni≥0.9mol, and its diffraction peak is the characteristic peak of the a-NaFeO2 layered structure, belonging to the hexagonal crystal system and R-3m space group.

[0023] The above-mentioned molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material is used as a positive electrode in lithium-ion batteries.

[0024] Beneficial effects:

[0025] Compared with the prior art, the present invention discloses a molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material, and its preparation method and application. The single-crystal ultra-high nickel lithium-ion battery positive electrode material is prepared by a two-step lithiation method combined with molybdenum doping and lithium molybdate coating processes. Compared with single-crystal ultra-high nickel lithium-ion battery positive electrode materials prepared by other methods, it exhibits better cycle performance. The specific advantages are as follows:

[0026] 1. The two-step lithiation method is conducive to the growth of single crystal particles to a suitable size, avoiding the inhibitory effect of molybdenum on particle growth during high-temperature calcination, and retaining the advantage of high energy density of single crystal ultra-high nickel cathode;

[0027] 2. Molybdenum doping is conducive to forming a more stable crystal structure and inhibiting the degradation of material structure during the cycle;

[0028] 3. The surface lithium molybdate coating can isolate the direct contact between the electrolyte and the positive electrode material, while accelerating the ion transfer rate.

[0029] 4. The present invention uses water-soluble ammonium molybdate as the molybdenum source, and the ammonium molybdate is attached to the surface of the precursor by evaporating the aqueous solution. Compared with mixing methods such as grinding, the molybdenum source is more evenly distributed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The XRD patterns of Examples 1 to 3 and Comparative Examples 1 to 7 of the present invention are shown below:

[0031] Figure 2 The SEM images of the positive electrode materials prepared under different processes are as follows: a) Example 1; b) Example 2; c) Example 3; d) Comparative Example 1; e) Comparative Example 2; f) Comparative Example 3;

[0032] Figure 3 This is the SEM image of Comparative Example 4;

[0033] Figure 4 SEM images of positive electrode materials prepared under different processes, wherein a) Comparative Example 8; b) Comparative Example 9; c) Comparative Example 10; d) Comparative Example 11; e) Comparative Example 12; f) Comparative Example 13; g) Comparative Example 14; h) Comparative Example 15; i) Comparative Example 16; j) Comparative Example 17; k) Comparative Example 18; l) Comparative Example 19; m) Comparative Example 20;

[0034] Figure 5 The SEM images of the positive electrode materials prepared under different processes, wherein a) Comparative Example 21; b) Comparative Example 22; c) Comparative Example 23; d) Comparative Example 24; e) Comparative Example 25; f) Comparative Example 26;

[0035] Figure 6 The SEM images of the positive electrode materials prepared under different processes, wherein a) Comparative Example 27; b) Comparative Example 28; c) Comparative Example 29; d) Comparative Example 30;

[0036] Figure 7 The SEM images of the positive electrode materials prepared under different processes, wherein a) Comparative Example 31; b) Comparative Example 32; c) Comparative Example 33;

[0037] Figure 8 The high-precision XRD patterns of Example 3 and Comparative Example 3 are shown;

[0038] Figure 9 The Raman spectra of Example 3 and Comparative Example 3 are shown;

[0039] Figure 10 This is the EDS image of Example 3, where blue represents Ni and pink represents Mo;

[0040] Figure 11 This is the STEM image of the surface of Example 3;

[0041] Figure 12 The cycle performance curves of Examples 1 to 3 and Comparative Examples 1 to 4 are shown;

[0042] Figure 13 dQ dV of Example 3 and Comparative Example 3 at different cycle numbers -1 curve;

[0043] Figure 14 DEMS test curves of Example 3 and Comparative Example 3. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner in conjunction with the accompanying drawings and preferred embodiments below, but the scope of protection of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased on the market or can be prepared by existing methods. The room temperature proposed in the present invention refers to 25°C.

[0046] A method for preparing a molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material comprises the following steps:

[0047] Step 1: Evenly mix the dried nickel-cobalt binary precursor with LiOH·H2O and Li2CO3, and calcine them in stages in a tubular atmosphere furnace with flowing oxygen, first at 450-550°C for 3-5 hours, then at 800-900°C for 20-24 hours, and finally cool them to room temperature with the furnace, grind and sieve them, and perform gas phase crushing to obtain a lithium-deficient single crystal ultra-high nickel positive electrode material;

[0048] Step 2: Take the lithium-deficient single crystal ultra-high nickel cathode material and (NH4)6Mo7O 24 ·4H2O aqueous solution, stirred for 0.5-1.5h, heated in a water bath to 55-65℃, continued stirring for 5.5-6.5h, then placed in a vacuum drying oven, dried at 75-85℃, ground and sieved to obtain surface-attached (NH4)6Mo7O 24 Lithium-deficient single crystal ultra-high nickel cathode material;

[0049] Step 3: Take the surface-attached (NH4)6Mo7O 24 The lithium-deficient single crystal ultra-high nickel positive electrode material is uniformly mixed with LiOH·H2O and calcined in a tubular atmosphere furnace with flowing oxygen in stages, first at 450-550℃ for 3-5 hours, then at 650-850℃ for 8-12 hours, and finally cooled to room temperature with the furnace. After grinding and sieving, a molybdenum-doped and lithium molybdate-coated single crystal ultra-high nickel binary lithium-ion battery positive electrode material is obtained.

[0050] In the present invention, the vacuum drying temperature of the binary precursor powder is 60-100°C, preferably 80°C. The first staged sintering lithiation process is 500°C for 3-5 hours, followed by 800-900°C for 20-24 hours. In a preferred embodiment, the sintering process is first 500°C for 4 hours, followed by 850°C for 22 hours. The second staged sintering lithiation process is 450-550°C for 3-5 hours, followed by 650-850°C for 8-12 hours. In a preferred embodiment, the sintering process is first 500°C for 4 hours, followed by 800°C for 10 hours.

[0051] Example 1:

[0052] Step 1: weigh 5.00 g of Ni dried in vacuum at 80°C. 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 2.06g LiOH·H2O and 0.40g Li2CO3, where n(Ni+Co):n Li(LiOH·H2O):n Li(Li2CO3)=1:0.9:0.2 (molar ratio), and placed in an oxygen-permeable tubular furnace for staged sintering, first at 500°C for 4h, then at 850°C for 22h, and then cooled to room temperature with the furnace, ground through a 300-mesh sieve, and subjected to gas phase crushing to obtain a lithium-deficient single crystal ultra-high nickel positive electrode material.

[0053] Step 2: weigh 0.0721g (NH4)6Mo7O 24 4H2O was dissolved in 20 mL of deionized water, and 3.9449 g of lithium-deficient single crystal ultra-high nickel cathode material was added. After stirring for 1 h, the mixture was heated in a water bath to 60 ° C and stirred for 6 h. The mixture was then placed in a vacuum drying oven, dried at 80 ° C and ground through a 300 mesh sieve to obtain surface-attached (NH4)6Mo7O 24 Lithium-deficient single crystal ultra-high nickel positive electrode material.

[0054] Step 3, take 0.9862g of the sieved surface-attached (NH4)6Mo7O 24 The lithium-deficient single crystal ultra-high nickel cathode material powder was uniformly mixed with 0.0434 g LiOH·H2O, wherein n(Ni+Co+Mo):n Li(LiOH·H2O)=1:0.1 (molar ratio), and the mixture was placed in an oxygen-permeable tubular furnace for staged sintering, first at 500°C for 4 hours, then at 700°C for 10 hours, and then cooled to room temperature with the furnace. After grinding and sieving, a molybdenum-doped and lithium molybdate-coated single crystal ultra-high nickel lithium-ion battery cathode material was obtained.

[0055] Example 2:

[0056] The second high-temperature calcination process in step 3 is the same as in Example 1, except that the second high-temperature calcination process is first held at 500° C. for 4 hours and then held at 750° C. for 10 hours.

[0057] Example 3:

[0058] The second high-temperature calcination process in step 3 is the same as in Example 1, except that the second high-temperature calcination process is first held at 500° C. for 4 hours and then held at 800° C. for 10 hours.

[0059] Comparative Example 1:

[0060] Step 1, weigh 5.00g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 2.06g LiOH·H2O and 0.40g Li2CO3, where n(Ni+Co):n Li(LiOH·H2O):n Li(Li2CO3)=1:0.9:0.2 (molar ratio). The mixture was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4h, then at 850°C for 22h, and then cooled to room temperature with the furnace. After grinding, sieving and gas-phase crushing, the lithium-deficient single crystal ultra-high nickel positive electrode material was obtained.

[0061] Step 2: Weigh 3.9449 g of lithium-deficient single crystal ultra-high nickel positive electrode material and add 20 mL of deionized water. After stirring for 1 hour, heat it in a water bath to 60°C, continue stirring for 6 hours, then place it in a vacuum drying oven, dry it at 80°C, and grind and sieve it.

[0062] Step 3: Take 0.9862g of the sieved powder and mix it evenly with 0.0434g of LiOH·H2O, where n(Ni+Co):nLi(LiOH·H2O)=1:0.1 (molar ratio), place it in an oxygen-permeable tubular furnace and sinter it in stages, first at 500°C for 4h, then at 700°C for 10h, then cool it to room temperature with the furnace, grind and sieve to obtain a single crystal ultra-high nickel lithium-ion battery positive electrode material.

[0063] Comparative Example 2:

[0064] The same procedures as in Comparative Example 1 were followed except that the second high-temperature calcination process in step 3 was changed to first keeping the temperature at 500° C. for 4 h and then keeping the temperature at 750° C. for 10 h.

[0065] Comparative Example 3:

[0066] Except that the second high-temperature calcination process in step 3 is changed to first keeping at 500° C. for 4 hours and then keeping at 800° C. for 10 hours, the rest is the same as that of comparative example 1.

[0067] Comparative Example 4:

[0068] Weigh 2.00g Ni 0.93 Co 0.07(OH)2 powder was uniformly mixed with 1.05g LiOH·H2O, wherein nLi:n(Ni+Co)=1.15:1 (molar ratio), and the mixture was placed in an oxygen-permeable tubular furnace for staged sintering, first at 500°C for 4h, then at 700°C for 14h, and then cooled to room temperature with the furnace. After grinding and sieving, a polycrystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0069] The positive electrode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were made into 2032-type button-type simulated batteries to test their electrochemical performance. The specific steps are as follows: (1) The positive electrode materials, conductive acetylene black and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1, and PVDP was first dissolved in an appropriate amount of N-methylpyrrolidone (NMP). Then, the mixed positive electrode materials and acetylene black powder were added to NMP and stirred to form a slurry; (2) The slurry was evenly scraped onto an aluminum foil substrate, and the wet electrode was placed in a vacuum drying oven, dried at 110°C for 12 hours, and cut into positive electrode sheets; (3) In a dry glove box, a simulated battery was assembled. The above-mentioned self-made positive electrode sheet was used as the positive electrode, the metal lithium sheet was used as the negative electrode, the Celgard2500 membrane was used as the diaphragm, and the electrolyte was 1 mol·L -1 The LiPF6 was dissolved in a solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (volume ratio 1:1:1) to test its electrochemical performance, as shown in Table 1.

[0070] Table 1 Electrochemical properties of positive electrode materials of Examples 1-3 and Comparative Examples 1-4 at 2.70-4.50V

[0071]

[0072] It can be seen from Table 1 that the first charge and discharge efficiency of Examples 1 to 3 and Comparative Examples 1 to 3 are lower than that of Comparative Example 4. This is because the primary particle size of the polycrystalline positive electrode material is smaller than that of the single crystal material, and the specific surface area of the spherical secondary particles composed of the primary particles is larger than that of the single crystal particles. The first discharge capacity and the first charge and discharge efficiency of Examples 1 to 3 are higher than those of Comparative Examples 1 to 3. This is because the surface side reactions are reduced after the lithium molybdate coating. After 100 cycles at 4.5V and 0.5C, the capacity retention rates of Examples 1 to 3 and Comparative Examples 1 to 3 are higher than those of Comparative Example 4. This is because the polycrystalline positive electrode material will have serious intercrystalline cracks during the cycle, and the electrolyte will penetrate into it and react with the active material, accelerating the degradation of the material structure, while the single crystal positive electrode material fundamentally avoids the occurrence of intercrystalline cracks and has better cycle stability. Compared with Comparative Examples 1 to 3, the discharge capacity and capacity retention rate of Examples 1 to 3 after the cycle are higher, among which Example 3 still has 161.6mAh·g -1The discharge specific capacity and capacity retention rate reached 79.0%, the highest among all samples. This is because the Mo element forms a more stable Mo-O bond after entering the crystal lattice, which improves the structural stability of the material. The surface lithium molybdate also plays a protective role, thereby reducing capacity attenuation during the cycle.

[0073] Comparative Example 5:

[0074] Weigh 2.00g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 1.05g LiOH·H2O, where nLi:n(Ni+Co)=1.15:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 850°C for 22h, and then cooled to room temperature with the furnace. After grinding, sieving and gas-phase crushing, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0075] Comparative Example 6:

[0076] Weigh 2.00g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 0.96g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 850°C for 22h, and then cooled to room temperature with the furnace. After grinding, sieving and gas-phase crushing, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0077] Comparative Example 7:

[0078] Weigh 2.00g Ni 0.93 Co 0.07 (OH)2 powder was evenly mixed with 1.05g LiOH·H2O, where nLi:n(Ni+Co)=1.15:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 875°C for 22h, and then cooled to room temperature with the furnace. After grinding, sieving and gas-phase crushing, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0079] Comparative Example 8:

[0080] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 750°C for 18h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0081] Comparative Example 9:

[0082] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 850°C for 16h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0083] Comparative Example 10:

[0084] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 850°C for 18h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0085] Comparative Example 11:

[0086] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 850°C for 20h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0087] Comparative Example 12:

[0088] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 850°C for 25h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0089] Comparative Example 13:

[0090] Weigh 18.9923g Ni 0.93 Co 0.07(OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 775°C for 20h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0091] Comparative Example 14:

[0092] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 800°C for 20h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0093] Comparative Example 15:

[0094] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 825°C for 20h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0095] Comparative Example 16:

[0096] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in stages in an oxygen-permeable tubular furnace, first at 500°C for 4h, then at 950°C for 16h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0097] Comparative Example 17:

[0098] Weigh 18.9923g Ni 0.93 Co 0.07(OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in a muffle furnace in stages, first at 500°C for 4h, then at 850°C for 16h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0099] Comparative Example 18:

[0100] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, wherein nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in a muffle furnace in stages, first at 500°C for 4h, then at 850°C for 16h, and then cooled to room temperature with the furnace. The mixture was then placed in an oxygen-permeable tubular furnace and calcined at 850°C for 5h. Finally, the mixture was cooled to room temperature with the furnace, and the single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained after grinding and sieving.

[0101] Comparative Example 19:

[0102] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, where nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in a muffle furnace in stages, first at 500°C for 4h, then at 850°C for 20h, and then cooled to room temperature with the furnace. After grinding and sieving, a single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0103] Comparative Example 20:

[0104] Weigh 18.9923g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 9.1151g LiOH·H2O, wherein nLi:n(Ni+Co)=1.05:1 (molar ratio), and sintered in a muffle furnace in stages, first at 500°C for 4h, then at 850°C for 20h, and then cooled to room temperature with the furnace. The mixture was then placed in an oxygen-permeable tubular furnace and calcined at 850°C for 5h. Finally, the mixture was cooled to room temperature with the furnace, and the single-crystal ultra-high nickel lithium-ion battery positive electrode material was obtained after grinding and sieving.

[0105] Comparative Example 21:

[0106] Weigh 0.0285g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 2.9790g of Ni 0.93 Co 0.07The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0107] 1.8994 g of the sieved powder was weighed and uniformly mixed with 0.9967 g of LiOH·H2O, with nLi:n(Ni+Co+Mo)=1.15:1 (molar ratio). The powder was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 h, then at 875°C for 22 h, and then cooled to room temperature with the furnace. After grinding, sieving and vapor phase crushing, a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0108] Comparative Example 22:

[0109] Weigh 0.0570g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 2.9581g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0110] 1.8996 g of the sieved powder was weighed and uniformly mixed with 0.9948 g of LiOH·H2O, with nLi:n(Ni+Co+Mo)=1.15:1 (molar ratio). The powder was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 h, then at 875°C for 22 h, and then cooled to room temperature with the furnace. After grinding, sieving and vapor phase crushing, a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0111] Comparative Example 23:

[0112] Weigh 0.0853g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 2.9373g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0113] 1.8998 g of the sieved powder was weighed and uniformly mixed with 0.9929 g of LiOH·H2O, with nLi:n(Ni+Co+Mo)=1.15:1 (molar ratio). The powder was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 h, then at 875°C for 22 h, and then cooled to room temperature with the furnace. After grinding, sieving and vapor phase crushing, a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0114] Comparative Example 24:

[0115] Weigh 0.1135g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 2.9166g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0116] 1.9000 g of the sieved powder was weighed and uniformly mixed with 0.9910 g of LiOH·H2O, with nLi:n(Ni+Co+Mo)=1.15:1 (molar ratio). The mixture was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 h, then at 875°C for 22 h, and then cooled to room temperature with the furnace. After grinding, sieving and vapor phase crushing, a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0117] Comparative Example 25:

[0118] Weigh 0.1415g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 2.8959g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0119] 1.9002 g of the sieved powder was weighed and uniformly mixed with 0.9891 g of LiOH·H2O at a molar ratio of nLi:n(Ni+Co+Mo)=1.15:1. The powder was then sintered in an oxygen-permeable tubular furnace in stages, first at 500°C for 4 h and then at 875°C for 22 h. The material was then cooled to room temperature with the furnace, ground, sieved, and vapor-phase crushed to obtain a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material.

[0120] Comparative Example 26:

[0121] Weigh 0.1695g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 2.8754g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0122] 1.9004 g of the sieved powder was weighed and uniformly mixed with 0.9873 g of LiOH·H2O at a molar ratio of nLi:n(Ni+Co+Mo)=1.15:1. The powder was then sintered in an oxygen-permeable tubular furnace in stages, first at 500°C for 4 h and then at 875°C for 22 h. The mixture was then cooled to room temperature with the furnace, ground, sieved, and vapor-phase crushed to obtain a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material.

[0123] Comparative Example 27:

[0124] Weigh 0.0380g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 3.9720g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0125] Weigh 3.0000 g of the sieved powder and mix it evenly with 1.1700 g of LiOH·H2O and 0.2277 g of Li2CO3, with nLi(LiOH·H2O):n Li(Li2CO3):n(Ni+Co+Mo)=0.9:0.2:1. Place it in an oxygen-permeable tubular furnace and sinter it in stages, first at 500°C for 4 h, then at 875°C for 22 h, then cool it to room temperature with the furnace, grind it, sieve it, and perform gas-phase crushing.

[0126] 2.0000 g of the powder after gas phase crushing was weighed and uniformly mixed with 0.0867 g of LiOH·H2O, with n Li(LiOH·H2O):n(Ni+Co+Mo)=0.1:1. The mixture was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 hours and then at 700°C for 10 hours. The mixture was then cooled to room temperature with the furnace and ground and sieved to obtain a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material.

[0127] Comparative Example 28:

[0128] Weigh 0.0759g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 3.9442g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0129] Weigh 3.0000 g of the sieved powder and mix it evenly with 1.1678 g of LiOH·H2O and 0.2273 g of Li2CO3, with nLi(LiOH·H2O):n Li(Li2CO3):n(Ni+Co+Mo)=0.9:0.2:1. Place it in an oxygen-permeable tubular furnace and sinter it in stages, first at 500°C for 4 h, then at 875°C for 22 h, then cool it to room temperature with the furnace, grind it, sieve it, and perform gas-phase crushing.

[0130] 2.0000 g of the powder after gas phase crushing was weighed and uniformly mixed with 0.0865 g of LiOH·H2O, with n Li(LiOH·H2O):n(Ni+Co+Mo)=0.1:1. The mixture was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 hours and then at 700°C for 10 hours. The mixture was then cooled to room temperature with the furnace and ground and sieved to obtain a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material.

[0131] Comparative Example 29:

[0132] Weigh 0.1137g (NH4)6Mo7O 24 4H2O was dissolved in 20mL of deionized water and 3.9164g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0133] Weigh 3.0000 g of the sieved powder and mix it evenly with 1.1678 g of LiOH·H2O and 0.2273 g of Li2CO3, with nLi(LiOH·H2O):n Li(Li2CO3):n(Ni+Co+Mo)=0.9:0.2:1. Place it in an oxygen-permeable tubular furnace and sinter it in stages, first at 500°C for 4 h, then at 875°C for 22 h, then cool it to room temperature with the furnace, grind it, sieve it, and perform gas-phase crushing.

[0134] 2.0000 g of the powder after gas phase crushing was weighed and uniformly mixed with 0.0865 g of LiOH·H2O, with n Li(LiOH·H2O):n(Ni+Co+Mo)=0.1:1. The mixture was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 hours and then at 700°C for 10 hours. The mixture was then cooled to room temperature with the furnace and ground and sieved to obtain a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material.

[0135] Comparative Example 30:

[0136] Weigh 0.1513g (NH4)6Mo7O 244H2O was dissolved in 20mL of deionized water and 3.8888g of Ni 0.93 Co 0.07 The (OH)2 powder was stirred in a water bath at 60°C for 6 h, dried in a vacuum drying oven at 80°C, and then ground and sieved.

[0137] Weigh 3.0000 g of the sieved powder and mix it evenly with 1.1633 g of LiOH·H2O and 0.2264 g of Li2CO3, with nLi(LiOH·H2O):n Li(Li2CO3):n(Ni+Co+Mo)=0.9:0.2:1. Place it in an oxygen-permeable tubular furnace and sinter it in stages, first at 500°C for 4 h, then at 875°C for 22 h, then cool it to room temperature with the furnace, grind it, sieve it, and perform gas-phase crushing.

[0138] 2.0000 g of the powder after gas phase crushing was weighed and uniformly mixed with 0.0862 g of LiOH·H2O, with n Li(LiOH·H2O):n(Ni+Co+Mo)=0.1:1. The mixture was placed in an oxygen-permeable tubular furnace and sintered in stages, first at 500°C for 4 hours and then at 700°C for 10 hours. The mixture was then cooled to room temperature with the furnace and ground and sieved to obtain a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material.

[0139] Comparative Example 31:

[0140] Weigh 3.0000g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 1.2344g LiOH·H2O and 0.3603g Li2CO3, with n Li(LiOH·H2O):n Li(Li2CO3):n(Ni+Co)=0.9:0.2:1, and placed in an oxygen-permeable tubular furnace for staged sintering, first at 500℃ for 4h, then at 850℃ for 22h, and then cooled to room temperature with the furnace, ground, sieved and gas-phase crushed.

[0141] Weigh 0.9931g of the powder after gas phase crushing and 0.0090g of (NH4)6Mo7O 24 ·4H2O and 0.0433g LiOH·H2O were uniformly mixed and placed in an oxygen-permeable tubular furnace for staged sintering, first at 500℃ for 4h, then at 700℃ for 10h, and then cooled to room temperature with the furnace. After grinding and sieving, a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0142] Comparative Example 32:

[0143] Weigh 3.0000g Ni 0.93 Co 0.07(OH)2 powder was uniformly mixed with 1.2344g LiOH·H2O and 0.3603g Li2CO3, with n Li(LiOH·H2O):n Li(Li2CO3):n(Ni+Co)=0.9:0.2:1, and placed in an oxygen-permeable tubular furnace for staged sintering, first at 500℃ for 4h, then at 850℃ for 22h, and then cooled to room temperature with the furnace, ground, sieved and gas-phase crushed.

[0144] Weigh 0.9862g of the powder after gas phase crushing and 0.0180g of (NH4)6Mo7O 24 ·4H2O and 0.0433g LiOH·H2O were uniformly mixed and placed in an oxygen-permeable tubular furnace for staged sintering, first at 500℃ for 4h, then at 700℃ for 10h, and then cooled to room temperature with the furnace. After grinding and sieving, a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0145] Comparative Example 33:

[0146] Weigh 3.0000g Ni 0.93 Co 0.07 (OH)2 powder was uniformly mixed with 1.2344g LiOH·H2O and 0.3603g Li2CO3, with n Li(LiOH·H2O):n Li(Li2CO3):n(Ni+Co)=0.9:0.2:1, and placed in an oxygen-permeable tubular furnace for staged sintering, first at 500℃ for 4h, then at 850℃ for 22h, and then cooled to room temperature with the furnace, ground, sieved and gas-phase crushed.

[0147] Weigh 0.9794g of the powder after gas phase crushing and 0.0270g of (NH4)6Mo7O 24 ·4H2O and 0.0432g LiOH·H2O were uniformly mixed and placed in an oxygen-permeable tube furnace for staged sintering, first at 500℃ for 4h, then at 700℃ for 10h, and then cooled to room temperature with the furnace. After grinding and sieving, a molybdenum-doped and lithium molybdate-coated single-crystalline ultra-high nickel lithium-ion battery positive electrode material was obtained.

[0148] Figure 1 The XRD spectra of some single crystal and polycrystalline positive electrode materials were compared. Examples 1 to 3 and comparative examples 1 to 7 all showed the typical structural characteristics of LiNiO2 positive electrode materials. The diffraction peaks were characteristic peaks of a-NaFeO2 layered structure, belonging to the hexagonal system and R-3m space group. The (006) / (012) and (018) / (110) pairs of diffraction peaks of the positive electrode materials of Examples 1 to 3 were obviously split, forming a better layered structure. The peak intensity ratio of (003) to (104) was similar to that of the layered positive electrode material LiNiO2. + / Ni 2+The degree of mixing is related to the peak intensity ratio I (003) / I (104) The larger the value, the lower the degree of cation mixing.

[0149] Table 2 compares the unit cell parameters and peak intensity ratios of Examples 1 to 3 and Comparative Examples 1 to 7. The a-axis and c-axis lengths and unit cell volumes of Examples 1 to 3 are larger than those of Comparative Examples 1 to 3, indicating that Mo 6+ After entering the lattice, the interlayer spacing is increased, which is beneficial to the transmission of lithium ions; the peak intensity ratio I (003) / I (104) are smaller than the corresponding comparative examples 1 to 3, which is mainly due to the fact that Mo 6+ The introduction of Ni 2+ The cell parameters of Examples 1 to 3 increase successively, indicating that a higher secondary calcination temperature is conducive to Mo incorporation, and the peak intensity is higher than that of I (003) / I (104) The gradual decrease is due to the intensification of lithium-nickel mixing caused by high temperature.

[0150] Table 2 Cell parameters and (003) / (104) peak intensity ratios of positive electrode materials of Examples 1-3 and Comparative Example 1

[0151]

[0152]

[0153] Figure 2 are SEM images of Examples 1 to 3 and Comparative Examples 1 to 3, Figure 3 This image shows Comparative Example 4. It shows that Examples 1-3 and Comparative Examples 1-3 form single crystal particles approximately 2 μm in size, while Comparative Example 4 forms secondary particles approximately 2 μm in size formed by agglomeration of primary particles. The morphology of Examples 1-3 and Comparative Examples 1-3 is primarily determined by the initial high-temperature calcination. The difference in morphology from Comparative Example 7 demonstrates the effectiveness of high-temperature solid-phase sintering for the synthesis of single-crystal, ultra-high nickel lithium-ion battery cathode materials.

[0154] Figure 4 The SEM images of comparative examples 8 to 20 are shown. All of comparative examples 8 to 20 have single crystal morphology, but there are problems such as particle agglomeration and uneven particle size distribution, which are not conducive to obtaining excellent electrochemical performance.

[0155] Figure 5 The SEM images of Comparative Examples 21 to 26 are shown. Figure 6 The SEM images of comparative examples 27 to 30 are shown. Since the Mo element inhibits grain growth during high-temperature calcination, the particle sizes of comparative examples 21 to 30 are generally small, and some samples exhibit polycrystalline morphology.

[0156] Figure 7The SEM images of comparative examples 31 to 33 are shown. All of comparative examples 31 to 33 have single crystal morphology, but the second high-temperature calcination temperature is low, resulting in the Mo element not effectively entering the crystal lattice, and the doping effect is not ideal.

[0157] Figure 8 The high-precision XRD patterns of Example 3 and Comparative Example 3 are shown below. Figure 9 3 and 4 are Raman spectra of Example 3 and Comparative Example 3. It can be seen that there is an additional spinel phase in Example 3. Figure 10 This is the EDS image of Example 3, which shows that Mo element exists on the surface of Example 3. Figure 11 The STEM image of the surface of Example 3 shows a spinel Li2MoO4 coating layer attached to the surface of the layered positive electrode. The above confirms the effectiveness of Mo modification.

[0158] Figure 12 It shows that as the lithium insertion and extraction process continues, the cycle retention rates of Examples 1 to 3 and Comparative Examples 1 to 3 are all higher than those of Comparative Example 4, indicating that the single crystal positive electrode material has better cycle stability. Among them, after 100 cycles at a rate of 0.5C, the discharge capacity of Example 3 is still 161.6 mAh·g -1 , the capacity retention rate reaches 76.0%, and the discharge specific capacity and capacity retention rate are both the highest. This shows that molybdenum doping plays a role in stabilizing the lattice structure of the material, and lithium molybdate coating plays a role in isolating direct contact with the electrolyte and reducing side reactions, which is more conducive to improving the cycle stability of the material.

[0159] Figure 13 Shows the dQ dV of Example 3 and Comparative Example 3 at different cycle numbers -1 Curve, dQ dV of both at the first cycle -1 The curves are highly overlapped, showing similar phase transition behavior (H1-M-H2-H3). After 100 cycles, the H2-H3 phase transition peak intensity of Comparative Example 3 is significantly weakened, indicating that its layered structure has been severely degraded during the cycling process. However, Example 3 still maintains a high H2-H3 peak intensity after cycling, indicating that molybdenum doping and lithium molybdate coating can effectively protect the material's crystal structure and inhibit harmful phase transitions.

[0160] Figure 14 The DEMS test curves of Example 3 and Comparative Example 3 show that during charging to 4.7 V, Example 3 produces almost no oxygen, while Comparative Example 3 produces a large amount of oxygen and the amount of carbon dioxide released increases significantly, indicating that molybdenum doping and lithium molybdate coating modification greatly enhance lattice oxygen stability and inhibit oxygen precipitation.

[0161] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs a structure and embodiment similar to this technical solution without inventiveness, they shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a single crystal ultra-high nickel binary lithium ion battery positive electrode material doped with molybdenum and coated with lithium molybdate, characterized in that: Using nickel-cobalt binary hydroxide precursor as raw material, after mixing with lithium salt, it is calcined at high temperature to obtain a lithium-deficient single crystal ultra-high nickel positive electrode material, which is then mixed with a molybdenum source and lithium salt, and calcined at high temperature again to finally obtain a molybdenum-doped and lithium molybdate-coated single crystal ultra-high nickel binary lithium-ion battery positive electrode material.

2. The method for preparing the molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material according to claim 1, characterized in that: The following steps are involved: Step 1: Evenly mix the dried nickel-cobalt binary precursor with the lithium source, calcine them in stages in a tubular atmosphere furnace with flowing oxygen, heat them to 450-550°C, and keep them warm for 3-5 hours, then continue to heat them to 800-900°C, keep them warm for 20-24 hours, and finally cool them to room temperature with the furnace, grind and sieve them, and perform gas phase crushing to obtain a lithium-deficient single crystal ultra-high nickel positive electrode material; Step 2: Take the lithium-deficient single crystal ultra-high nickel cathode material and (NH4)6Mo7O 24 ·4H2O aqueous solution, stirred for 0.5-1.5h, heated in a water bath to 55-65℃, continued stirring for 5.5-6.5h, then placed in a vacuum drying oven, dried at 75-85℃, ground and sieved to obtain surface-attached (NH4)6Mo7O 24 Lithium-deficient single crystal ultra-high nickel cathode material; Step 3: Take the surface-attached (NH4)6Mo7O 24 The lithium-deficient single crystal ultra-high nickel positive electrode material is evenly mixed with a lithium source, calcined in stages in a tubular atmosphere furnace with flowing oxygen, heated to 450-550°C, and kept warm for 3-5 hours, then continued to heat to 650-850°C, kept warm for 8-12 hours, and finally cooled to room temperature with the furnace. After grinding and sieving, a molybdenum-doped and lithium molybdate-coated single crystal ultra-high nickel binary lithium-ion battery positive electrode material is obtained.

3. The method for preparing the molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material according to claim 2, characterized in that: The chemical formula of the ultra-high nickel binary precursor in step 1 is Ni 0.93 Co 0.07 (OH)2, the lithium source is at least one of lithium nitrate, lithium acetate, lithium carbonate and lithium hydroxide.

4. The method for preparing the molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material according to claim 2, characterized in that: The vacuum drying temperature of the nickel-cobalt binary precursor powder in step 1 is 60-100°C.

5. The method for preparing the molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material according to claim 2, characterized in that: Dried nickel-cobalt binary precursor powder Ni 0.93 Co 0.07 (OH)2 and lithium source n(Ni+Co):nLi=1:1.1 (molar ratio).

6. The method for preparing the molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material according to claim 2, characterized in that: In step 2, (NH4)6Mo7O 24 The mass of the lithium-deficient single crystal ultra-high nickel cathode material mixed with the 4H2O aqueous solution is 1-2g.

7. The method for preparing the molybdenum-doped and lithium molybdate-coated single-crystal ultra-high nickel binary lithium-ion battery positive electrode material according to claim 2, characterized in that: In step 2, the lithium-deficient single crystal ultra-high nickel positive electrode material and (NH4)6Mo7O 24 In 4H2O, n(Ni+Co):nMo=0.99:0.01 (molar ratio).

8. The method for preparing a single crystal ultra-high nickel binary lithium ion battery positive electrode material according to claim 2, characterized in that: In step 3, (NH4)6Mo7O is attached to the surface 24 The lithium-deficient single crystal ultra-high nickel positive electrode material and the lithium source have n(Ni+Co):nLi=0.9:0.

1.

9. A single crystal ultra-high nickel binary lithium-ion battery positive electrode material doped with molybdenum and coated with lithium molybdate prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The single crystal ultra-high nickel binary lithium ion battery positive electrode material contains Ni≥0.9 mol, and its diffraction peak is a characteristic peak of a-NaFeO2 layered structure, belonging to the hexagonal system and R-3m space group.

10. Use of the single crystal ultra-high nickel binary lithium ion battery positive electrode material according to claim 9 as a positive electrode in a lithium ion battery.

Images