A ternary positive electrode material, preparation method and application thereof

Abstract

The present invention provides a ternary positive electrode material, its preparation method and application. The ternary positive electrode material comprises a ternary positive electrode material matrix and a coating layer coated on the surface of the ternary positive electrode material matrix, wherein the coating layer is a nitride metal; the chemical formula of the ternary positive electrode material matrix is: LiNi x Co y Mn 1‑x‑y O2, wherein 0<x<1, 0<y<1. The preparation method is simple and easy, and the obtained ternary positive electrode material can stabilize the electrode / electrolyte interface and isolate Ni when used as a positive electrode material for lithium ion batteries. 4+ The channels that react with the electrolyte significantly reduce the dissolution of transition metal ions corroded by HF, significantly improve the storage performance of the material at high temperature and full charge, and can also significantly reduce the DCR growth during the material cycle, thereby improving the material's cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a ternary positive electrode material, a preparation method thereof, and applications thereof. Background Art

[0002] Lithium-ion batteries are widely used in electronics, aerospace, energy storage and electric vehicles due to their high voltage, high energy density and excellent safety performance. Among them, the positive electrode material in the battery system is a key factor affecting battery performance. Among the existing positive electrode material systems, ternary materials are widely used due to their high specific energy density and good cycle performance. However, under full charge and high temperature conditions, the highly oxidized Ni on the surface of the ternary positive electrode material 4+ The ions will react with the electrolyte to produce HF and alkyl carbonates, etc. HF will cause the degradation of the positive electrode surface structure and a sharp decline in cycle performance.

[0003] In order to improve the storage and electrochemical performance of ternary cathode materials under full charge and high temperature conditions, a common strategy is to coat the cathode material surface with nano-metal oxides (such as aluminum oxide, titanium oxide, and magnesium oxide) using a solid-phase mixing method. However, the cycling and storage performance of cathode materials coated with general metal oxides under full charge and high temperature conditions are not well improved. This is mainly due to the following reasons: (1) the coating layer is not uniform, making it difficult to completely isolate the electrode / electrolyte interface; (2) the general metal oxide coating layer easily reacts with HF decomposed from the electrolyte to form a new exposed interface, resulting in continuous structural degradation and performance degradation of the interface; (3) the general metal oxide coating layer is in an insulating state, and the internal resistance of lithium ions passing through the interface layer is large, resulting in poor rate and cycling performance of the material.

[0004] For example, CN114014377A reduces and then oxidizes a metal oxide to coat a portion of the surface of a nickel-cobalt-manganese precursor with a metal oxide layer, which is then mixed with a lithium source and sintered to produce a ternary positive electrode material for a lithium-ion battery. This positive electrode material reduces the charge-discharge migration distance and interfacial reaction impedance of lithium ions, optimizing the battery's low-temperature performance and rate performance. However, the coating layer of this positive electrode material exhibits poor uniformity, and the battery's high-temperature storage and cycling performance are not effectively improved. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a ternary cathode material, a preparation method and application thereof. The ternary cathode material can stabilize the electrode / electrolyte interface, isolate Ni 4+ The channel that reacts with the electrolyte improves the storage performance of the positive electrode material at high temperature and fully charged state, significantly reduces the DCR growth during the material cycle, and improves the cycle performance of the material.

[0006] In a first aspect, the present invention provides a ternary positive electrode material, comprising a ternary positive electrode material substrate and a coating layer coated on the surface of the ternary positive electrode material substrate, wherein the coating layer is a metal nitride;

[0007] The chemical formula of the ternary cathode material matrix is: LiNi x Co y Mn 1-x-y O2, where 0<x<1, 0<y<1.

[0008] Preferably, the mass ratio of the coating layer to the ternary positive electrode material matrix is (0.001-0.1):1.

[0009] Preferably, the particle size of the ternary positive electrode material matrix is 4-20 μm.

[0010] Preferably, the metal nitride includes any one or a combination of at least two of titanium nitride, silicon nitride, aluminum nitride, tungsten nitride, strontium nitride, magnesium nitride or zirconium nitride, preferably titanium nitride.

[0011] In a second aspect, the present invention provides a method for preparing a ternary positive electrode material, comprising the following steps:

[0012] Mixing the ternary cathode material matrix and the flocculant to form a base liquid;

[0013] A water / organic solvent coating liquid containing metal nitride is added to the base liquid to obtain a mixed liquid, which is then dried and sintered in sequence to obtain a ternary positive electrode material.

[0014] Preferably, the flocculant includes any one or more of polyvinyl alcohol, citric acid, polyacrylonitrile or polyacrylamide.

[0015] Preferably, the organic solvent includes any one or more of ethanol, acetone or formic acid.

[0016] Preferably, the mass ratio of the ternary cathode material matrix, flocculant, water / organic solvent coating liquid and metal nitride is 1:(0.1-1.0):(0.2-5.0):(0.1-1.5).

[0017] Preferably, the volume ratio of water to organic solvent is 1:(0.20-1.25).

[0018] Preferably, the addition rate of the water / organic solvent coating solution is 0.1-0.5 mL / min, preferably 0.5 mL / min.

[0019] Preferably, the sintering temperature is 200-500° C., and the sintering time is 5-25 hours.

[0020] In a third aspect, the present invention provides a lithium-ion battery comprising the ternary positive electrode material or the ternary positive electrode material prepared by the preparation method.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention can stabilize the electrode / electrolyte interface by coating a dense metal nitride layer on the surface of the ternary positive electrode material matrix, isolating Ni 4+ The channel that reacts with the electrolyte significantly reduces the dissolution of transition metal ions caused by HF corrosion, and significantly improves the storage performance of the material at high temperature and full charge;

[0023] (2) The metal nitride coating is conducive to the insertion and extraction of lithium ions, significantly reducing the DCR growth during the material cycle and improving the cycle performance of the ternary cathode material;

[0024] (3) The metal nitride coating has excellent mechanical strength and can maintain the integrity of the coating during the material crushing process;

[0025] (4) The preparation method of the ternary positive electrode material matrix provided by the present invention is simple and easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an SEM image of the ternary cathode material obtained in Example 1;

[0027] Figure 2 XRD patterns of the positive electrode materials obtained in Examples 1-2 and Comparative Examples 1-3;

[0028] Figure 3 This is a comparison chart of the cycle performance of the positive electrode materials obtained in Example 1-2 and Comparative Example 1-2 at 55°C. DETAILED DESCRIPTION

[0029] All raw materials involved in the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0030] The present invention provides a ternary positive electrode material, comprising a ternary positive electrode material substrate and a coating layer coated on the surface of the ternary positive electrode material substrate, wherein the coating layer is a nitride metal;

[0031] The chemical formula of the ternary cathode material matrix is: LiNi x Co y Mn 1-x-y O2, where 0<x<1, 0<y<1.

[0032] The present invention can stabilize the electrode / electrolyte interface and isolate Ni 4+ The channels for reaction with the electrolyte significantly reduce the dissolution of transition metal ions caused by HF corrosion, significantly improving the storage performance of the material at high temperatures and under full charge. The metal nitride coating also facilitates the insertion and extraction of lithium ions, significantly reducing the increase in the DCR during the material cycle and improving the cycling performance of the ternary cathode material. In addition, the metal nitride coating has excellent mechanical strength and can maintain the integrity of the coating during the material pulverization process.

[0033] In the present invention, the mass ratio of the coating layer to the ternary positive electrode material matrix is preferably (0.001-0.1):1, which can be 0.001:1, 0.005:1, 0.01:1, 0.03:1, 0.05:1, 0.07:1, 0.09:1 or 0.1:1, etc. Other point values within the above numerical range can be selected, and they will not be repeated here.

[0034] In the present invention, the particle size of the ternary positive electrode material matrix is preferably 4-20μm, which can be 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm or 20μm, etc. Other point values within the above numerical range can be selected, and they will not be repeated here.

[0035] In the present invention, the metal nitride preferably includes any one or a combination of at least two of titanium nitride, silicon nitride, aluminum nitride, tungsten nitride, strontium nitride, magnesium nitride or zirconium nitride, preferably titanium nitride.

[0036] The present invention also provides a method for preparing a ternary cathode material, comprising the following steps:

[0037] Mixing the ternary cathode material matrix and the flocculant to form a base liquid;

[0038] A water / organic solvent coating liquid containing metal nitride is added to the base liquid to obtain a mixed liquid, which is then dried and sintered in sequence to obtain a ternary positive electrode material.

[0039] In the present invention, the ternary cathode material matrix can be prepared according to conventional methods well known to those skilled in the art. For example, the ternary cathode material matrix can be prepared according to the following method:

[0040] After the ternary cathode material matrix precursor and the lithium source are uniformly mixed, they are sintered in an atmosphere of oxygen and / or air.

[0041] The chemical formula of the ternary cathode material matrix precursor is Ni x Co y Mn 1-x-y(OH)2, wherein 0<x<1, 0<y<1. The sintering temperature is preferably 300-1000℃, and the sintering time is preferably 8-30h.

[0042] The sintering temperature may be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, etc.

[0043] The sintering time can be 8 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours or 30 hours, etc.

[0044] Other point values within the above numerical range can be selected and will not be described in detail here.

[0045] In the present invention, the sintering preferably further includes jaw crushing and pulverizing treatment, so that the particle size of the ternary positive electrode material matrix obtained after pulverization is 4-20 μm.

[0046] In the present invention, the water / organic solvent coating solution containing the metal nitride preferably also includes a cationic surfactant. This is to allow the surfactant to be adsorbed on the surface of the metal nitride and to be positively charged, and to be adsorbed on the surface of the negatively charged positive electrode material by electrostatic action, thereby forming a nano-coating layer. The present invention preferably adds the metal nitride and the cationic surfactant to the water / organic solvent coating solution and allows it to stand for 20-30 hours. The standing time can be 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, or 30 hours, and other values within the above numerical range can be selected, which will not be repeated here.

[0047] The cationic surfactant is preferably an aqueous cationic surfactant, preferably comprising any one or more of cetyltrimethylammonium chloride, dodecyltrimethylammonium chloride, or cetylpyridinium chloride. The flocculant is preferably any one or more of polyvinyl alcohol, citric acid, polyacrylonitrile, or polyacrylamide, more preferably polyvinyl alcohol. The organic solvent is preferably any one of ethanol, acetone, or formic acid, more preferably ethanol, because the addition of ethanol can adjust the dielectric constant of the solution and improve the solubility of the coating solution for surfactants containing organic structures such as alkyl groups.

[0048] In the present invention, the mass ratio of the ternary cathode material matrix, flocculant, water / organic solvent coating solution, and metal nitride is 1:(0.1-1.0):(0.2-5.0):(0.1-1.5). The mass ratio of the metal nitride to the cationic surfactant is preferably 1:(0.1-1.5). The volume ratio of water to the organic solvent is preferably 1:(0.20-1.25).

[0049] The mass ratio of the ternary positive electrode material matrix, flocculant, water / organic solvent coating liquid and metal nitride can be 1:0.1:0.2:0.1, 1:0.2:1:0.5, 1:0.4:0.5:0.3, 1:0.5:1:0.6, 1:1:2:0.8, 1:1:3:1 or 1:1:5:1.5, etc.

[0050] The mass ratio of the metal nitride to the cationic surfactant can be 1:0.1, 1:0.3, 1:0.5, 1:0.7, 1:0.9, 1:1.1, 1:1.3 or 1:1.5, etc.

[0051] The volume ratio of water to organic solvent can be 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1 or 1:1.25, etc.

[0052] Other point values within the above numerical range can be selected and will not be described in detail here.

[0053] In the present invention, the water / organic solvent coating solution is preferably added using a peristaltic pump. If the addition speed is too fast, it will not form a uniform coating layer and may even damage the structure of the coating layer. In the present invention, the water / organic solvent coating solution is preferably added at a speed of 0.1-0.5 mL / min, more preferably 0.5 mL / min.

[0054] The addition rate of the water / organic solvent coating liquid can be 0.1 mL / min, 0.2 mL / min, 0.3 mL / min, 0.4 mL / min or 0.5 mL / min, and other point values within the above numerical range can be selected, which will not be repeated here.

[0055] Before drying, if the solids content of the mixed solution is within the range of 5-50%, evaporation of water is not required. However, if the obtained mixed solution is relatively dilute or a sol having a target solids content is desired, evaporation to dryness is preferably further performed. The evaporation to dryness preferably involves placing the mixed solution in a rotary evaporator and evaporating the solvent at a temperature not exceeding 80° C. to obtain a sol having the target solids content.

[0056] The present invention has no particular limitation on the drying method, but spray drying is preferred.

[0057] In the present invention, the sintering temperature is preferably 200-500° C., and the sintering time is preferably 5-25 hours.

[0058] The sintering temperature may be 200°C, 250°C, 300°C, 350°C, 400°C, 450°C or 500°C.

[0059] The sintering time can be 5h, 10h, 15h, 20h or 25h.

[0060] Other point values within the above numerical range can be selected and will not be described in detail here.

[0061] The preparation method provided by the invention is simple and easy to implement and can realize industrial production.

[0062] In a third aspect, the present invention provides a lithium-ion battery comprising the ternary positive electrode material or the ternary positive electrode material prepared by the preparation method.

[0063] 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.

[0064] To further illustrate the present invention, the following examples are provided for detailed description. The sources of the raw materials used in the following examples are not particularly limited and can be purchased from the market or prepared according to conventional preparation methods known to those skilled in the art.

[0065] Example 1

[0066] This embodiment provides a positive electrode material LiNi coated with nano-TiN 0.65 Co 0.07 Mn 0.28 O2@TiN, its preparation method is as follows:

[0067] (1) Ni with a particle size of 4 μm 0.65 Co 0.07 Mn 0.28 The (OH)2 precursor and lithium hydroxide were mixed evenly in a Li / (Ni+Mn) molar ratio of 1.04, and sintered at 940 ° C for 12 h in a box furnace under oxygen atmosphere. The ternary positive electrode material LiNi was obtained after being crushed by bipolar rollers (upper spacing 15 cm, lower spacing 5 cm). 0.65 Co 0.07 Mn 0.28 O2;

[0068] (2) 1 g of 20 nm TiN and 0.5 g of hexadecyltrimethylammonium chloride were added to 200 mL of a water / ethanol solution with a water / ethanol volume ratio of 0.5. The solution was stirred for 1 h to dissolve the solution, and the solution was allowed to stand for 24 h before use.

[0069] (3) Take 50g of the ternary cathode material obtained in step (1) and 5g of polyvinyl alcohol, add them to 200mL of deionized water, and ultrasonicate for 1h, keeping the solution in a stirring state to form a base liquid;

[0070] (4) adding the water / ethanol coating solution containing nano-TiN to the base solution via a peristaltic pump (flow rate of 0.5 mL / min), stirring evenly, and then rotary evaporating at 50° C. to a solid content of 35% to obtain a sol;

[0071] (5) The above sol was spray-dried (70°C, 20 min) to form granules, and sintered at 400°C for 10 h in air atmosphere to obtain LiNi 0.65 Co 0.07 Mn 0.28 O2@TiN.

[0072] The morphology of the cathode material obtained in Example 1 was characterized using a scanning electron microscope. Figure 1 As shown, it can be seen that there is an obvious coating layer structure on the surface of the ternary positive electrode material, and the coating layer is relatively uniform, and the overall coating effect is good.

[0073] Example 2

[0074] This embodiment provides a positive electrode material LiNi coated with nano-TiN 0.65 Co 0.07 Mn 0.28 O2@TiN, its preparation method is as follows:

[0075] (1) Ni with a particle size of 4 μm 0.65 Co 0.07 Mn 0.28 The (OH)2 precursor and lithium hydroxide were mixed evenly in a Li / (Ni+Mn) molar ratio of 1.04, and sintered at 940 ° C for 12 h in an oxygen atmosphere in a box furnace. The rollers (upper spacing 15 cm, lower spacing 5 cm) were crushed to obtain the ternary positive electrode one-sintered material LiNi 0.65 Co 0.07 Mn 0.28 O2;

[0076] (2) 1 g of 100 nm TiN and 1 g of hexadecyltrimethylammonium chloride were added to 200 mL of a water / ethanol solution with a water / ethanol volume ratio of 1. The solution was stirred for 1 h to dissolve the TiN nanoparticles to obtain a water / ethanol coating solution. The solution was allowed to stand for 24 h before use.

[0077] (3) Take 35g of the ternary cathode material obtained in step (1) and 1g of polyvinyl alcohol, add them to 200mL of deionized water, and ultrasonicate for 1h, keeping the solution in a stirring state to form a base liquid;

[0078] (4) adding the water / ethanol coating solution containing nano-TiN to the base solution via a peristaltic pump (flow rate of 0.2 mL / min), stirring evenly, and then rotary evaporating at 50° C. to a solid content of 35% to obtain a sol;

[0079] (5) The above sol was spray-dried (60°C, 25 min) to form granules, and sintered at 400°C for 10 h in air atmosphere to obtain LiNi 0.65 Co 0.07 Mn 0.28 O2@TiN.

[0080] Example 3

[0081] This embodiment provides a positive electrode material LiNi coated with nano-TiN 0.6 Co 0.1 Mn 0.3 O2@TiN, its preparation method is as follows:

[0082] (1) Ni with a particle size of 10 μm 0.6 Co 0.1 Mn 0.3 The (OH)2 precursor and lithium hydroxide were mixed evenly in a Li / (Ni+Mn) molar ratio of 1.08, and sintered at 960 ° C for 15 h in an oxygen atmosphere in a box furnace. The rollers (upper spacing 15 cm, lower spacing 5 cm) were crushed to obtain the ternary positive electrode one-sintered material LiNi 0.6 Co 0.1 Mn 0.3 O2;

[0083] (2) 1 g of 50 nm TiN and 2 g of hexadecyltrimethylammonium chloride were added to 200 mL of a water / ethanol solution with a water / ethanol volume ratio of 1.25. The solution was stirred for 1 h to dissolve the solution, and the solution was allowed to stand for 24 h before use.

[0084] (3) Take 25g of the ternary cathode material obtained in step (1) and 3g of polyvinyl alcohol, add them to 200mL of deionized water, and ultrasonicate for 1h, keeping the solution in a stirring state to form a base liquid;

[0085] (4) adding the water / ethanol coating solution containing nano-TiN to the base solution via a peristaltic pump (flow rate of 0.45 mL / min), stirring evenly, and then rotary evaporating at 50° C. to a solid content of 50% to obtain a sol;

[0086] (5) The above sol was spray-dried (80°C, 15 min) to form granules, and sintered at 300°C for 10 h in air atmosphere to obtain LiNi 0.6 Co 0.1Mn 0.3 O2@TiN.

[0087] Example 4

[0088] This embodiment provides a positive electrode material LiNi coated with nano-TiN 0.8 Co 0.1 Mn 0.1 O2@TiN, its preparation method is as follows:

[0089] (1) Ni with a particle size of 12 μm 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor and lithium hydroxide were mixed evenly in a Li / (Ni+Mn) molar ratio of 1.06, and sintered at 780 ° C for 18 h in an oxygen atmosphere in a box furnace. The rollers (upper spacing 15 cm, lower spacing 5 cm) were crushed to obtain the ternary positive electrode one-sintered material LiNi 0.65 Co 0.07 Mn 0.28 O2@TiN;

[0090] (2) 2 g of 100 nm TiN and 0.4 g of hexadecyltrimethylammonium chloride were added to 200 mL of a water / ethanol solution with a water / ethanol volume ratio of 0.4. The solution was stirred for 1 h to dissolve the TiN nanoparticles to obtain a water / ethanol coating solution. The solution was allowed to stand for 24 h before use.

[0091] (3) Take 20g of the ternary cathode material obtained in step (1) and 2g of polyvinyl alcohol, add them to 100mL of deionized water, and ultrasonicate for 1h, keeping the solution in a stirring state to form a base liquid;

[0092] (4) adding the water / ethanol coating solution containing nano-TiN to the base solution via a peristaltic pump (flow rate of 0.4 mL / min), stirring evenly, and then rotary evaporating at 50° C. to a solid content of 25% to obtain a sol;

[0093] (5) The above sol was spray-dried (70°C, 20 min) to granulate, and sintered at 270°C for 10 h in air atmosphere to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2@TiN.

[0094] Example 5

[0095] This embodiment provides a positive electrode material LiNi coated with nano-TiN 0.65 Co 0.07 Mn 0.28O2@TiN, compared with Example 1, the only difference is that the addition rate of the water / ethanol coating solution containing nano-TiN in step (4) is 2 mL / min, and the other steps and parameters are consistent with Example 1.

[0096] Example 6

[0097] This embodiment provides a positive electrode material LiNi coated with nano-TiN 0.65 Co 0.07 Mn 0.28 Compared with Example 1, the only difference of O2@TiN is that the sintering temperature in step (5) is 650°C, and the other steps and parameters are consistent with Example 1.

[0098] Comparative Example 1

[0099] This comparative example provides a ternary positive electrode material LiNi 0.65 Co 0.07 Mn 0.28 O2, the preparation method is as follows:

[0100] (1) Ni with a particle size of 4 μm 0.65 Co 0.07 Mn 0.28 After the (OH)2 precursor and lithium hydroxide were evenly mixed in a Li / (Ni+Mn) molar ratio of 1.04, they were sintered at 940°C for 12 h in an oxygen atmosphere in a box furnace, and crushed on rollers (upper spacing 15 cm, lower spacing 5 cm) to obtain a ternary positive electrode one-sintered material;

[0101] (2) Place the ternary cathode material in a box furnace and sinter it at 400 ° C for 10 h in an air atmosphere to obtain the ternary cathode material LiNi 0.65 Co 0.07 Mn 0.28 O2.

[0102] Comparative Example 2

[0103] This comparative example provides a ternary positive electrode material LiNi 0.65 Co 0.07 Mn 0.28 O2@TiN is coated using the traditional dry method. The specific steps are as follows:

[0104] (1) Ni with a particle size of 4 μm 0.65 Co 0.07 Mn 0.28 The (OH)2 precursor and lithium hydroxide were mixed evenly in a Li / (Ni+Mn) molar ratio of 1.04, and sintered at 940 ° C for 12 h in an oxygen atmosphere in a box furnace. The rollers (upper spacing 15 cm, lower spacing 5 cm) were crushed to obtain the ternary positive electrode one-sintered material LiNi0.65 Co 0.07 Mn 0.28 O2;

[0105] (2) Take 2.5 kg of the above-obtained LiNi 0.65 Co 0.07 Mn 0.28 O2 was mixed with 15g of nano-TiN and sintered at 400℃ for 12h in air atmosphere in a box furnace to obtain LiNi 0.65 Co 0.07 Mn 0.28 O2@TiN.

[0106] Comparative Example 3

[0107] This comparative example provides a ternary positive electrode material LiNi 0.65 Co 0.07 Mn 0.28 O2@Al2O3 is coated using the traditional dry method. The specific steps are as follows:

[0108] (1) Ni with a particle size of 4 μm 0.65 Co 0.07 Mn 0.28 The (OH)2 precursor and lithium hydroxide were mixed evenly in a Li / (Ni+Mn) molar ratio of 1.04, and sintered at 940 ° C for 12 h in an oxygen atmosphere in a box furnace. The rollers (upper spacing 15 cm, lower spacing 5 cm) were crushed to obtain the ternary positive electrode one-sintered material LiNi 0.65 Co 0.07 Mn 0.28 O2;

[0109] (2) Take 2.5 kg of the above-obtained LiNi 0.65 Co 0.07 Mn 0.28 O2 was mixed with 12g of nano-Al2O3 and sintered at 400℃ for 12h in air atmosphere in a box furnace to obtain LiNi 0.65 Co 0.07 Mn 0.28 O2@Al2O3.

[0110] Performance Testing

[0111] XRD characterization was performed on the positive electrode materials obtained in Examples 1-2 and Comparative Examples 1-3. The results are as follows: Figure 2 As shown, it can be seen that no impurity peaks appear in the spectra of the positive electrode materials obtained in Examples 1-2 and Comparative Examples 1-3, and the surface nano-TiN coating does not change the crystal structure of the material. According to the XRD refinement data, the intensity ratio of the 003 / 104 peak of the sample is greater than 1.2, indicating that the material has a low Li / Ni mixing value.

[0112] For the positive electrode materials prepared in Examples 1-6 and Comparative Examples 1-3, the metal dissolution amounts of Ni, Co, and Mn were compared after storage at 80°C for 30 and 60 days, respectively, when the batteries were fully charged. The testing method was as follows: the prepared ternary positive electrode materials were assembled into button cells. When the batteries were fully charged (4.4V), the cells were disassembled after storage at 80°C for 30 and 60 days, respectively. The positive electrode sheets were cleaned with DMC, the active material layer of the positive electrode sheets was scraped off, and then heated in aqua regia for 15-30 minutes to dissolve. The solutions were then subjected to ICP testing to determine the Ni, Co, and Mn contents, yielding the data in Table 1.

[0113] Table 1

[0114]

[0115]

[0116] It can be seen from the data in Table 1 above that the metal dissolution amounts of the three elements Ni, Co, and Mn in the positive electrode materials obtained in Examples 1-4 are significantly lower than those in Comparative Examples 1-3, indicating that the ternary positive electrode material provided by the present invention can form an effective and stable interface layer, significantly reduce the electrode / electrolyte interface reaction, and reduce the dissolution of transition metal Ni, Co, and Mn elements caused by HF corrosion on the material surface.

[0117] From the data results of Comparative Examples 2 and 3, it can be seen that the transition metal ion dissolution of the ternary material of Comparative Example 2 coated with nano-TiN using the traditional dry process is significantly less, indicating that the effect of TiN coating is better than that of traditional alumina.

[0118] From the data results of Examples 1-2 and 5-6, it can be seen that the addition rate of the water / ethanol coating solution containing nano-TiN or the sintering temperature of the sol will affect the metal dissolution amount of the three elements Ni, Co, and Mn in the positive electrode material.

[0119] The positive electrode materials obtained in Example 1-2 and Comparative Example 1-2 were subjected to a cycle performance test at 55° C. The test method is as follows:

[0120] The prepared ternary cathode material was assembled into a button cell, wherein the electrode material: conductive carbon black = 90:10 wt%, the solvent was NMP, and the battery electrode surface density was 1.2 mg / cm 2 , at a voltage of 2.8-4.4V, charge and discharge at a rate of 0.1C / 0.1C for 3 cycles at 55℃, and then at a rate of 1C / 1C for 50 cycles, the result is Figure 3 data.

[0121] The test results are as follows Figure 3As shown, it can be seen that the cycle performance of the positive electrode material obtained in Example 1-2 is significantly better than that in Comparative Example 1-2.

[0122] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A ternary cathode material comprising a ternary cathode material substrate and a coating layer coated on the surface of the ternary cathode material substrate, wherein the coating layer is a metal nitride; The metal nitride is titanium nitride; The chemical formula of the ternary cathode material matrix is: LiNi x Co y Mn 1-x-y O2, where 0<x<1, 0<y<1; The ternary cathode material is prepared according to the following method: Mixing the ternary cathode material matrix and the flocculant to form a base liquid; adding a water / organic solvent coating solution containing metal nitride to the base solution to obtain a mixed solution, and sequentially drying and sintering the mixed solution to obtain a ternary positive electrode material; The metal nitride-containing water / organic solvent coating solution further comprises an aqueous cationic surfactant, wherein the aqueous cationic surfactant comprises any one or more of hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride or hexadecylpyridinium chloride; The addition rate of the water / organic solvent coating solution is 0.1-0.5 mL / min; The sintering temperature is 200-500° C., and the sintering time is 5-25 h.

2. The ternary cathode material according to claim 1, characterized in that The mass ratio of the coating layer to the ternary positive electrode material matrix is (0.001-0.1):

1.

3. The ternary cathode material according to claim 1, characterized in that The particle size of the ternary positive electrode material matrix is 4-20 μm.

4. The method for preparing a ternary cathode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Mixing the ternary cathode material matrix and the flocculant to form a base liquid; adding a water / organic solvent coating solution containing metal nitride to the base solution to obtain a mixed solution, and sequentially drying and sintering the mixed solution to obtain a ternary positive electrode material; The water / organic solvent coating liquid containing metal nitride further comprises an aqueous cationic surfactant; the aqueous cationic surfactant comprises any one or more of cetyltrimethylammonium chloride, dodecyltrimethylammonium chloride or cetylpyridinium chloride; The metal nitride is titanium nitride; The addition rate of the water / organic solvent coating solution is 0.1-0.5 mL / min; The sintering temperature is 200-500° C., and the sintering time is 5-25 h.

5. The preparation method according to claim 4, characterized in that The flocculant includes any one or more of polyvinyl alcohol, citric acid, polyacrylonitrile or polyacrylamide; The organic solvent includes any one or more of ethanol, acetone or formic acid.

6. The preparation method according to claim 4, characterized in that The mass ratio of the ternary cathode material matrix, flocculant, water / organic solvent coating liquid and metal nitride is 1:(0.1-1.0):(0.2-5.0):(0.1~1.5); The volume ratio of the water to the organic solvent is 1:(0.20-1.25).

7. A lithium-ion battery, characterized in that: The invention comprises the ternary positive electrode material according to any one of claims 1 to 3 or the ternary positive electrode material prepared by the preparation method according to any one of claims 4 to 6.

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