A core-shell structured ternary cathode material, its preparation method and a lithium-ion battery

Abstract

The present invention discloses a core-shell structured ternary cathode material, a preparation method thereof, and a lithium-ion battery, which relates to the technical field of lithium-ion battery materials. The core-shell structured ternary cathode material includes a core layer and a shell layer. The shell layer includes a film-forming coating layer and an island-shaped coating layer. The film-forming coating layer is formed by coating ternary fine powder in the nickel-rich ternary water-washing waste liquid, and the island-shaped coating layer is obtained by reacting a metal salt solution with the residual lithium on the core layer and the film-forming coating layer. The present invention adopts secondary coating, so that the coating dew points that may exist in the primary coating can be filled in the secondary coating, the coating layer is denser and more uniform, and the coating effect is better. The present invention realizes the recycling and reuse of the nickel-rich ternary water-washing waste liquid, avoids the economic loss and resource waste in the waste liquid treatment process, and the obtained core-shell structured ternary cathode material has a stable coating shell layer, taking into account the ion conduction performance and a certain electrical conductivity, and has excellent cycle performance and rate performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium - ion battery materials, and more particularly, to a core - shell structured ternary cathode material, a preparation method thereof, and a lithium - ion battery. Background Art

[0002] The nickel - rich layered material is one of the most widely used advanced lithium - ion battery cathodes at present. Increasing the nickel content in the layered cathode material can provide high capacity, but the nickel - rich cathode material is chemically unstable and its surface will react with moisture or air to form residual lithium compounds on the surface. These lithium compounds react with the electrolyte during the battery cycling process to generate gas, which will cause safety problems such as battery swelling, and there is a potential risk of fire and explosion. At present, a large number of studies have been carried out to remove the residual lithium compounds by using various solvents (such as water, ethanol, and polyaniline). Among them, the cheap and efficient water - washing process has been recognized by battery enterprises and applied in practice. Some studies have shown that after water - washing, the nickel - rich cathode material can effectively reduce gas generation under high - temperature storage.

[0003] However, the water - washing process consumes a huge amount of pure water, and the generated waste liquid needs to be strictly treated before being discharged. In the current industrial nickel - rich ternary water - washing process, the main components of the wastewater are spinel / shale - phase ternary cathode micropowders, LiOH, Li2CO3, and extremely small amounts of metal elements. When the existing process treats the wastewater from the industrial nickel - rich ternary water - washing process, it cannot effectively reuse the main components in the wastewater from the industrial nickel - rich ternary water - washing process, resulting in economic losses and resource waste during the waste - liquid treatment process, and also easily causing environmental pollution.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a core - shell structured ternary cathode material, a preparation method thereof, and a lithium - ion battery.

[0006] The present invention is implemented as follows:

[0007] In a first aspect, the present invention provides a core - shell structured ternary cathode material, which includes a core layer and a shell layer. The general formula of the core layer is LiNi x Co y Mn (1-x-y) O2, where 0.3 ≤ x < 1, y > 0, and 1 - x - y > 0. The shell layer includes a film - forming coating layer and an island - like coating layer. The film - forming coating layer coats the surface of the core layer, and the island - like coating layer coats the surface of the film - forming coating layer. The film - forming coating layer is a ternary micropowder, and its general formula is LiNi a Co b Mn (1-a-b)O₂, where 0.7 ≤ a < 1, b > 0, and 1 - a - b > 0; the island-shaped coating layer is obtained by reacting a metal salt solution with the residual lithium on the core layer and the film-forming coating layer.

[0008] In a second aspect, the present invention provides a method for preparing a core-shell structured ternary cathode material, which includes:

[0009] (1) Stir the nickel-rich ternary washing waste liquid, perform vacuum distillation to obtain a ternary suspension, and add a dispersant to obtain a ternary dispersion. Among them, the main component in the nickel-rich ternary washing waste liquid is ternary fine powder, and the general formula of the ternary fine powder is LiNi a Co b Mn (1-a-b) O₂, where 0.7 ≤ a < 1, b > 0, and 1 - a - b > 0;

[0010] (2) Coating the ternary dispersion on a ternary substrate to form a film-forming coating layer to obtain an intermediate; the general formula of the ternary substrate is LiNi x Co y Mn (1-x-y) O₂, 0.3 ≤ x < 1, y > 0, and 1 - x - y > 0;

[0011] (3) Coating a metal salt solution on the intermediate to obtain a coated material;

[0012] (4) Sintering the coated material to form an island-shaped coating layer, and obtaining a core-shell structured ternary cathode material after cooling and sieving.

[0013] In a second aspect, the present invention provides a lithium-ion battery, which includes the core-shell structured ternary cathode material as described in any one of the above embodiments or the core-shell structured ternary cathode material obtained by the preparation method of the core-shell structured ternary cathode material as described in any one of the above embodiments.

[0014] The present invention has the following beneficial effects:

[0015] The preparation method of the core-shell structured ternary cathode material provided by this application obtains a ternary suspension with a certain concentration through vacuum distillation, uses a dispersant to improve the dispersibility of the suspension particles, conducts the first coating on the ternary substrate with a ternary dispersion liquid, and then combines with a metal salt solution for secondary coating. The obtained product after sintering will adhere to the ternary fine powder on the surface of the substrate and melt on the surface of the substrate, thereby forming a stable coating layer, taking into account both the ion conduction performance and the electrical conductivity. After sieving, a mixed-phase core-shell coating layer is obtained, and the obtained shell layer is a mixed-phase coating layer, which is composed of a spinel / shale-phase film coating layer and an island-shaped coating layer obtained by the reaction of the metal salt solution with residual lithium. It can effectively protect the inner core substrate from electrolyte corrosion, reduce side reactions, and reduce gas generation, thereby obtaining a ternary cathode material with long cycle life and low gas production. The present invention adopts a secondary spraying method, so that the coating dew point that may exist in the primary spraying can be filled in the secondary spraying, and the coating layer is denser and more uniform. Moreover, the coating environment is carried out at a certain temperature, which is also beneficial to improving the fluidity of the material. The mutual friction between the primary particles and the spraying droplets improves the coating effect. The present invention can realize the recycling and reuse of the washing waste liquid of nickel-rich ternary materials, avoid the economic losses and resource waste in the waste liquid treatment process, and at the same time provide a solution to the possible environmental pollution. The present invention will produce obvious economic and social benefits. The obtained core-shell structured ternary cathode material has a stable coating shell, taking into account both the ion conduction performance and a certain electrical conductivity, and has excellent cycle performance and rate performance. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 XRD pattern of the core-shell structured ternary cathode material provided in Example 1 of this application;

[0018] Figure 2 SEM pattern of the core-shell structured ternary cathode material provided in Example 1 of this application;

[0019] Figure 3 Cross-sectional morphology diagram of the core-shell structured ternary cathode material provided in Example 1 of this application;

[0020] Figure 4 Cycling stability curve provided in Experimental Example 1 of this application;

[0021] Figure 5 Rate performance curve provided in Experimental Example 2 of this application. Detailed Description of the Invention

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not indicated with the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0023] The present invention provides a core-shell structured ternary cathode material, which includes a core layer and a shell layer. The general formula of the core layer is LiNi x Co y Mn (1-x-y) O2, where 0.3 ≤ x < 1, y > 0, and 1 - x - y > 0. The shell layer includes a film coating layer and an island coating layer. The film coating layer is coated on the surface of the core layer, and the island coating layer is coated on the surface of the film coating layer; the film coating layer is a ternary fine powder, and its general formula is LiNi a Co b Mn (1-a-b) O2, where 0.7 ≤ a < 1, b > 0, and 1 - a - b > 0; the island coating layer is obtained by reacting a metal salt solution with the residual lithium on the core layer and the film coating layer.

[0024] The mass percentage of the core layer and the shell layer is 99% - 99.95%: 0.05% - 1%; the mass percentage of the film coating layer and the island coating layer in the shell layer is 20% - 40%: 60% - 80%.

[0025] The metal salt solution includes at least one of an iron solution, a cobalt solution, a manganese solution, a zirconium solution, an aluminum solution, a titanium solution, a tungsten solution, and a niobium solution;

[0026] Preferably, the mass concentration of any one of the metal salt solutions is 1% - 30%;

[0027] Preferably, the metal salt solution includes an iron solution, a cobalt solution, and a manganese solution, and the island coating is a cobalt-rich manganese lithium compound and lithium iron phosphate;

[0028] Preferably, the iron solution includes at least one of ferrous nitrate, ferric sulfate, and ferric chloride; the cobalt solution includes at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride; the manganese solution includes at least one of manganese nitrate, manganese sulfate, and manganese chloride;

[0029] Preferably, the general formula of the cobalt-rich manganese lithium compound is LiCo c Mn (1-c) O2, where 0.2 ≤ c < 1, 1 - c > 0.

[0030] It should be understood that when the metal salt solution includes at least one of a zirconium solution, an aluminum solution, a titanium solution, a tungsten solution, and a niobium solution, this part of the metal salt solution will react with lithium after subsequent sintering to form at least one of lithium zirconate, lithium metaaluminate, lithium titanate, lithium tungstate, and lithium niobate. Therefore, the composition of the shell layer in this application may also include at least one of lithium zirconate, lithium metaaluminate, lithium titanate, lithium tungstate, and lithium niobate.

[0031] The present invention provides a method for preparing a core-shell structured ternary cathode material, which comprises the following steps:

[0032] (1) Stir the nickel-rich ternary washing waste liquid, perform reduced-pressure distillation to obtain a ternary suspension, and add a dispersant to obtain a ternary dispersion.

[0033] Among them, the main component in the nickel-rich ternary washing waste liquid is ternary micropowder, and the general formula of the ternary micropowder is Li (1-x) Ni a Co b Mn (1-a-b) O2, where 0≤x≤0.5, 0.7≤a<1, b>0, and 1-a-b>0; the solid content of the ternary micropowder in the nickel-rich ternary washing waste liquid is 0.001%-2%; the composition of the nickel-rich ternary washing waste liquid also includes LiOH and Li2CO3. Before reduced-pressure distillation, the mass concentration of LiOH is 0.01%-0.8%, and the mass concentration of Li2CO3 is 0.01%-0.6%; after reduced-pressure distillation, the mass concentration of LiOH is 0.1%-8%, and the mass concentration of Li2CO3 is 0.1%-6%. The solid content of the ternary suspension after reduced-pressure distillation of the nickel-rich ternary washing waste liquid is 1%-20%.

[0034] The dispersant is used to disperse the ternary suspension, which is beneficial to improving the uniformity of subsequent coating. The volume ratio of the ternary suspension to the dispersant is 5-10:7-14.

[0035] In this application, the dispersant includes but is not limited to at least one of sodium pyrophosphate solution, sodium tripolyphosphate, and sodium hexametaphosphate. Preferably, the dispersant in this application is a sodium pyrophosphate solution with a mass concentration of 1%-6%. The sodium pyrophosphate solution can not only play a dispersing role but also react with the iron solution in the subsequent metal salt solution to form lithium iron phosphate and coat it on the surface of the substrate, increasing the ion conduction performance and certain electrical conductivity.

[0036] (2) Coating the ternary dispersion on the ternary substrate to form a film coating layer to obtain an intermediate;

[0037] The general formula of the ternary substrate is LiNi x Co y Mn (1-x-y)O2, where 0.3 ≤ x < 1, y > 0, and 1 - x - y > 0; Coating the ternary dispersion on the ternary substrate includes coating the ternary dispersion on the mixed-flowing ternary substrate in a spray manner; the spraying speed is 1 - 200 mL / min; the mixed-flowing manner includes at least one of ball milling, plow blade mixing, mechanical mixing, and pneumatic mixing. In this embodiment, by spraying and coating the ternary dispersion on the high-speed flowing intermediate, the coating can be made more uniform. In addition, in this application, the temperature of the ternary dispersion is 25 - 90 °C; the temperature of the ternary substrate is 25 - 150 °C.

[0038] (3) Coating the metal salt solution on the intermediate to obtain a coated material;

[0039] Coating the metal salt solution on the intermediate includes coating the metal salt solution on the mixed-flowing intermediate in a spray manner; the spraying speed is 1 - 200 mL / min; the mixed-flowing manner includes at least one of ball milling, plow blade mixing, mechanical mixing, and pneumatic mixing. In this application, the temperature of the metal salt solution is 25 - 90 °C, and the temperature of the intermediate is 25 - 150 °C;

[0040] Preferably, the metal salt solution includes at least one of iron solution, cobalt solution, manganese solution, zirconium solution, aluminum solution, strontium solution, cerium solution, and titanium solution; the mass concentration of any one in the metal salt solution is 1% - 30%; the volume ratio of the ternary suspension to the metal salt solution is 5 - 10:7 - 14.

[0041] (4) Sintering the coated material to form an island-shaped coating layer, and obtaining the core-shell structured ternary cathode material after cooling and sieving.

[0042] After coating the metal salt on the intermediate, sintering is carried out in air, oxygen, nitrogen, or a mixed atmosphere. The sintering temperature is 300 - 800 °C, the heating rate is 1 °C / min - 6 °C / min, and the holding time is 2 - 10 h; sintering can make the metal salt react with the residual lithium on the core layer and the film-forming coating layer, so that the product will adhere to and melt on the surface of the ternary fine powder on the core layer, thus forming a stable coating layer, taking into account the ion conduction performance and the electrical conductivity, and calcination can repair the defects of the lithium-deficient phase raw materials. For example, the lithium-deficient phase raw material Li (1-x) Ni a Co b Mn (1-a-b) O2, where Li 1-x represents the lithium-deficient phase, so that the final composition of the shell layer is LiNi a Co b Mn (1-a-b) O2. After sintering, the mesh number of the cooling and sieving is 100 - 500 meshes.

[0043] In addition, the present application also provides a lithium-ion battery, which includes the above core-shell structured ternary cathode material.

[0044] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0045] Example 1

[0046] A preparation method of a core-shell structured ternary cathode material includes the following steps:

[0047] (1) Stir the nickel-deficient lithium phase Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2-containing nickel-rich ternary washing waste liquid, and evaporate the water through vacuum distillation to obtain a ternary suspension with a concentration of 10%.

[0048] (2) Weigh 100 mL of the ternary suspension, add 140 mL of a sodium pyrophosphate solution with a concentration of ⑥%, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 60 °C, and coat the ternary dispersion onto a high-speed flowing ternary substrate by spraying to obtain an intermediate, with a spraying speed of 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0049] (3) Weigh 60 mL of a 25.56% ferrous nitrate solution, 40 mL of a 23.85% cobalt nitrate solution, and 40 mL of a 23.33% manganese nitrate solution respectively and mix them as a metal salt solution. Heat the metal salt solution to 60 °C and then coat it onto the high-speed flowing intermediate by spraying to obtain a coated material, with a spraying speed of 20 mL / min.

[0050] (4) Transfer the coated material obtained in step (3) to a box-type sintering furnace for calcination, with a heating rate of 3 °C / min, a calcination temperature of 650 °C, a calcination time of 6 h, and a calcination atmosphere of oxygen. After cooling and passing through a 300-mesh sieve after taking out of the furnace, a core-shell structured ternary cathode material is obtained.

[0051] Reaction principle:

[0052] 2Na4P2O7 + 4Fe(NO3)2 + 2LiOH + Li2CO3 → 4LiFePO4 + 8NaO + 4N2 + 10O2 + H2O + CO2;

[0053] 4Co(NO3)2 + 4Mn(NO3)2 + 2LiOH + Li2CO3 → 4LiCoMnO2 + H2O + CO2 + 8N2 + 21O2.

[0054] The nuclear layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.33LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.33LiFePO4, 0.33LiCo 0.5 Mn 0.5 O2, and the total mass proportion of the shell layer is 0.6%.

[0055] For the XRD patterns of the core-shell structured ternary cathode material obtained in Example 1 and the main components of the nickel-rich ternary washing waste liquid, please refer to Figure 1 , from Figure 1 it can be seen that I(003) / I(104) of Example 1 = 1.31. For the main component Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2 of the nickel-rich ternary washing waste liquid, the peak intensity ratio I (003) / I(104) = 0.98, and there is no splitting of (006) / (102) and (108) / (110), indicating that it has no obvious layered structure and is damaged during the washing process, mainly existing in the spinel and shale phases. That is, the film coating layer formed by coating the ternary dispersion liquid on the ternary substrate is the spinel and shale phases.

[0056] For the SEM of the core-shell structured ternary cathode material obtained in Example 1, please refer to Figure 2 , from Figure 2 it can be known that the diameter of its single crystal particles is about 5 μm, and the surface coating layer combines film coating and island coating. For the cross-sectional morphology of the core-shell structured ternary cathode material obtained in Example 1, please refer to Figure 3 , from Figure 3 it can be seen that the ternary fine powder is effectively fused to the surface of the substrate, and the thickness of the coating layer is about 193 nm.

[0057] Example 2

[0058] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0059] (1) Stir the nickel-rich ternary washing waste liquid containing 0.5% of Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, and evaporate the water through vacuum distillation to obtain a ternary suspension with a concentration of 10%;

[0060] (2) Weigh 50 mL of the ternary suspension, add 70 mL of a sodium pyrophosphate solution with a concentration of 6%, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 60 °C and then coat it onto a rapidly flowing ternary substrate by spraying to obtain an intermediate, with a spraying speed of 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0061] (3) Weigh 30 mL of a ferrous nitrate solution with a concentration of 25.56%, 20 mL of a cobalt nitrate solution with a concentration of 23.85%, and 20 mL of a manganese nitrate solution with a concentration of 23.33% respectively and mix them as the metal salt solution. Heat the metal salt solution to 60 °C and then coat it onto the rapidly flowing intermediate by spraying to obtain the coated material, with a spraying speed of 20 mL / min.

[0062] (4) Transfer the coated material from step (3) to a box-type sintering furnace for calcination, with a heating rate of 3 °C / min, a calcination temperature of 650 °C, a calcination time of 6 h, and a calcination atmosphere of oxygen. After taking out of the furnace, cool it and screen it to obtain the core-shell structured ternary cathode material.

[0063] The nuclear layer structural formula of the obtained core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.33LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.33LiFePO4, 0.33LiCo 0.5 Mn 0.5 O2, and the total mass proportion of the shell layer is 0.3%.

[0064] Example 3

[0065] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0066] (1) Stir the nickel-rich ternary washing waste liquid containing 0.5% of Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, evaporate the water by vacuum distillation to obtain a ternary suspension with a concentration of 10%;

[0067] (2) Weigh 100 mL of the ternary suspension, add 140 mL of a sodium pyrophosphate solution with a concentration of 6%, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 60 °C and then coat it onto a rapidly flowing ternary substrate by spraying to obtain an intermediate, with a spraying speed of 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0068] (3) Weigh 60 mL of a ferrous nitrate solution with a concentration of 25.56%, 40 mL of a cobalt nitrate solution with a concentration of 23.85%, and 40 mL of a manganese nitrate solution with a concentration of 23.33% respectively and mix them as the metal salt solution. After heating the solution to 60 °C, coat it onto the rapidly flowing intermediate by spraying respectively to obtain the coated material, with a spraying speed of 20 mL / min.

[0069] (4) Transfer the coated material from step (3) to a box-type sintering furnace for calcination, with a heating rate of 3 °C / min, a calcination temperature of 750 °C, a calcination time of 8 h, and a calcination atmosphere of oxygen. After cooling and sieving after taking out of the furnace, a core-shell structured ternary cathode material is obtained.

[0070] The nuclear layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.33LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.33LiFePO4, 0.33LiCo 0.5 Mn 0.5 O2, and the total mass proportion of the shell layer is 0.6%.

[0071] Example 4

[0072] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0073] (1) Stir the nickel-rich ternary water-washed waste liquid containing Li with a concentration of 0.5% 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, evaporate the water by vacuum distillation to obtain a ternary suspension with a concentration of 10%;

[0074] (2) Weigh 100 mL of the ternary suspension, add 140 mL of a sodium pyrophosphate solution with a concentration of 6%, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 60 °C, and coat the ternary dispersion onto a high-speed flowing ternary substrate by spraying to obtain an intermediate, with a spraying speed of 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0075] (3) Weigh 100 mL of a zirconium nitrate solution with a concentration of 5%, 50 mL of an aluminum nitrate solution with a concentration of 10%, and 50 mL of a niobium oxide alkali solution with a concentration of 10% respectively. After heating to 60 °C, coat them onto the high-speed flowing intermediate by spraying in sequence to obtain a coated material, with a spraying speed of 20 mL / min.

[0076] (4) Transfer the coated material in step (3) to a box-type sintering furnace for calcination. The heating rate is 3 °C / min, the calcination temperature is 650 °C, the calcination time is 6 h, and the calcination atmosphere is oxygen. After cooling and passing through a 300-mesh sieve after taking out of the furnace, a core-shell structured ternary cathode material is obtained.

[0077] The core layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.64LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.09Li2ZrO3, 0.15LiAlO2, 0.12LiNbO3, and the total mass proportion of the shell layer is 0.33%.

[0078] Example 5

[0079] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0080] (1) Stir the nickel-rich ternary water-washed waste liquid containing Li 1-x Ni 0.8 Co 0.15 Mn 0.05 O2 with a concentration of 2%, and evaporate the water through vacuum distillation to obtain a ternary suspension with a concentration of 18%;

[0081] (2) Weigh 70 mL of the ternary suspension, add 120 mL of a sodium pyrophosphate solution with a concentration of 2%, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 40 °C, and coat the ternary dispersion onto a high-speed flowing ternary substrate by spraying to obtain an intermediate, with a spraying speed of 50 mL / min. Among them, the ternary substrate is LiNi0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 120 °C.

[0082] (3) Weigh out 50 mL of a 10% ferrous nitrate solution, 30 mL of a 10% cobalt nitrate solution, and 30 mL of a 10% manganese nitrate solution respectively and mix them as the metal salt solution. Heat the metal salt solution to 40 °C and then coat it onto the high-speed flowing intermediate in a spray manner to obtain the coated material, with a spray speed of 20 mL / min.

[0083] (4) Transfer the coated material from step (3) to a box-type sintering furnace for calcination. The heating rate is 1 °C / min, the calcination temperature is 450 °C, the calcination time is 10 h, and the calcination atmosphere is nitrogen. After cooling and passing through a 300-mesh sieve, a core-shell structured ternary cathode material is obtained.

[0084] The core layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.68LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.15LiFePO4, 0.17LiCo 0.5 Mn 0.5 O2, and the total mass proportion of the shell layer is 0.7%.

[0085] Example 6

[0086] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0087] (1) Stir the nickel-rich ternary washing waste liquid containing 0.1% of Li 1-x Ni 0.7 Co 0.15 Mn 0.15 O2, evaporate the water by vacuum distillation to obtain a ternary suspension with a concentration of 5%;

[0088] (2) Weigh out 60 mL of the ternary suspension, add 100 mL of a 4% sodium pyrophosphate solution, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 90 °C and coat the ternary dispersion onto the high-speed flowing ternary substrate in a spray manner to obtain the intermediate, with a spray speed of 100 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 150 °C.

[0089] (3) Weigh out 50 mL of a 30% ferrous nitrate solution, 30 mL of a 30% cobalt nitrate solution, and 30 mL of a 30% manganese nitrate solution separately and mix them as the metal salt solution. Heat the metal salt solution to 90 °C and then coat it onto the high-speed flowing intermediate in a spray manner to obtain the coated material, with a spray speed of 20 mL / min.

[0090] (4) Transfer the coated material from step (3) to a box-type sintering furnace for calcination. The heating rate is 6 °C / min, the calcination temperature is 800 °C, the calcination time is 4 h, and the calcination atmosphere is air. After taking out of the furnace and cooling, sieve through a 300-mesh sieve to obtain the core-shell structured ternary cathode material.

[0091] The core layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.15LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.39LiFePO4, 0.46LiCo 0.5 Mn 0.5 O2, and the total mass proportion of the shell layer is 0.4%.

[0092] Comparative Example 1

[0093] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0094] (1) Stir the nickel-rich ternary water-washed waste liquid containing 0.5% Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, evaporate the water through vacuum distillation to obtain a 10% ternary suspension;

[0095] (2) Weigh out 100 mL of the ternary suspension, add 140 mL of a 6% sodium pyrophosphate solution, ultrasonically stir to obtain a ternary dispersion, heat the ternary dispersion to 60 °C, and coat it onto the high-speed flowing ternary substrate in a spray manner to obtain the coated material, with a spray speed of 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0096] (3) Transfer the coated material from step (2) to a box-type sintering furnace for calcination. The heating rate is 3 °C / min, the calcination temperature is 650 °C, the calcination time is 6 h, and the calcination atmosphere is oxygen. After taking out of the furnace and cooling, sieve to obtain the core-shell structured ternary cathode material.

[0097] The nuclear layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, and the total mass proportion of the shell layer is 0.2%.

[0098] For the XRD pattern of the core-shell structured ternary cathode material prepared in Comparative Example 1, please refer to Figure 1 , and from Figure 1 it can be seen that the peak shapes and peak intensities of Example 1 and Comparative Example 1 are similar. For Example 1, I(003) / I(104) = 1.31, and for Comparative Example 1, I(003) / I(104) = 1.27. The I(003) / I(104) of Comparative Example 1 is slightly lower than that of Example 1, indicating that its lithium-nickel mixing is more serious.

[0099] Comparative Example 2

[0100] A preparation method of a core-shell structured ternary cathode material includes the following steps:

[0101] (1) Weigh 140 mL of a 6% sodium pyrophosphate solution, 60 mL of a 25.56% ferrous nitrate solution, 40 mL of a 23.85% cobalt nitrate solution, and 40 mL of a 23.33% manganese nitrate solution respectively, heat them to 60 °C, and then coat them onto a high-speed flowing ternary substrate in a spray manner in sequence to obtain a coated material.

[0102] (2) Transfer the coated material obtained in step (1) to a box-type sintering furnace for calcination. The heating rate is 3 °C / min, the calcination temperature is 650 °C, the calcination time is 6 h, and the calcination atmosphere is oxygen. After cooling and sieving after taking out of the furnace, a core-shell structured ternary cathode material is obtained.

[0103] The nuclear layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.5LiFePO4, 0.5LiCo 0.5 Mn 0.5 O2, and the total mass proportion of the shell layer is 0.4%.

[0104] Comparative Example 3

[0105] A preparation method of a core-shell structured ternary cathode material includes the following steps:

[0106] (1) Weigh 60 mL of ferrous nitrate solution with a concentration of 25.56%, 40 mL of cobalt nitrate solution with a concentration of 23.85%, and 40 mL of manganese nitrate solution with a concentration of 23.33% respectively, mix them as the metal salt solution, heat the metal salt solution to 60 °C, and then coat it onto the high-speed flowing ternary substrate by spraying to obtain an intermediate. The spraying speed is 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C;

[0107] (2) Stir the nickel-rich ternary washing waste liquid containing 0.5% of Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, evaporate the water by vacuum distillation to obtain a ternary suspension with a concentration of 10%, weigh 100 mL of the ternary suspension, add 140 mL of sodium pyrophosphate solution with a concentration of 6%, obtain a ternary dispersion after ultrasonic stirring, heat the ternary dispersion to 60 °C, and coat it onto the high-speed flowing intermediate by spraying to obtain a coated material. The spraying speed is 20 mL / min.

[0108] (3) Transfer the coated material obtained in step (2) to a box-type sintering furnace for calcination. The heating rate is 3 °C / min, the calcination temperature is 650 °C, the calcination time is 6 h, and the calcination atmosphere is oxygen. After cooling and sieving through a 300-mesh sieve, a core-shell structured ternary cathode material is obtained.

[0109] The core layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.33LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.33LiFePO4, 0.33LiCo 0.5 Mn 0.5 O2, and the total mass ratio of the shell layer is 0.6%.

[0110] Comparative Example 4

[0111] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0112] (1) Stir the nickel-rich ternary washing waste liquid containing 0.5% of Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, evaporate the water by vacuum distillation to obtain a ternary suspension with a concentration of 5%;

[0113] (2) Weigh 50 mL of the ternary suspension, add 140 mL of a sodium pyrophosphate solution with a concentration of 6%, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 60 °C, and coat the ternary dispersion onto a high-speed flowing ternary substrate by spraying to obtain an intermediate. The spraying speed is 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0114] (3) Weigh 60 mL of a ferrous nitrate solution with a concentration of 25.56%, 40 mL of a cobalt nitrate solution with a concentration of 23.85%, and 40 mL of a manganese nitrate solution with a concentration of 23.33% respectively and mix them as the metal salt solution. Heat the metal salt solution to 60 °C and then coat it onto the high-speed flowing intermediate by spraying to obtain a coated material. The spraying speed is 20 mL / min.

[0115] (4) Transfer the coated material in step (3) to a box-type sintering furnace for calcination. The heating rate is 3 °C / min, the calcination temperature is 650 °C, the calcination time is 6 h, and the calcination atmosphere is oxygen. After taking out of the furnace, cool it and pass it through a 300-mesh sieve to obtain the core-shell structured ternary cathode material.

[0116] The core layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.11LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.44LiFePO4, 0.44LiCo 0.5 Mn 0.5 O2. The total mass percentage of the shell layer is 0.6%, and the mass percentage of the film coating layer and the island coating layer is 89%:11%.

[0117] Comparative Example 5

[0118] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0119] (1) Stir the nickel-rich ternary washing waste liquid containing 0.5% of Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2, evaporate the water by vacuum distillation to obtain a ternary suspension with a concentration of 20%;

[0120] (2) Weigh 200 mL of the ternary suspension, add 280 mL of a sodium pyrophosphate solution with a concentration of 6%, and obtain a ternary dispersion after ultrasonic stirring. Heat the ternary dispersion to 60 °C, and coat the ternary dispersion onto a high-speed flowing ternary substrate by spraying to obtain an intermediate, with a spraying speed of 20 mL / min. Among them, the ternary substrate is LiNi 0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0121] (3) Weigh 120 mL of a ferrous nitrate solution with a concentration of 25.56%, 80 mL of a cobalt nitrate solution with a concentration of 23.85%, and 80 mL of a manganese nitrate solution with a concentration of 23.33% respectively and mix them as a metal salt solution. Heat the metal salt solution to 60 °C and then coat it onto the high-speed flowing intermediate by spraying to obtain a coated material, with a spraying speed of 20 mL / min.

[0122] (4) Transfer the coated material from step (3) to a box-type sintering furnace for calcination, with a heating rate of 3 °C / min, a calcination temperature of 650 °C, a calcination time of 6 h, and a calcination atmosphere of oxygen. After cooling and passing through a 300-mesh sieve after leaving the furnace, a core-shell structured ternary cathode material is obtained.

[0123] The nuclear layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.5LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.25LiFePO4, 0.25LiCo 0.5 Mn 0.5 O2, and the total mass proportion of the shell layer is 1.6%.

[0124] Comparative Example 6

[0125] A preparation method of a core-shell structured ternary cathode material, comprising the following steps:

[0126] (1) Stir the nickel-rich ternary water-washed waste liquid containing Li 1-x Ni 0.9 Co 0.05 Mn 0.05 O2 with a concentration of 0.5%, and evaporate the water through vacuum distillation to obtain a ternary suspension with a concentration of 10%;

[0127] (2) Weigh 100 mL of the ternary suspension, stir it ultrasonically and heat it to 60 °C, and coat the ternary dispersion onto a high-speed flowing ternary substrate by spraying to obtain an intermediate, with a spraying speed of 20 mL / min. Among them, the ternary substrate is LiNi0.6 Co 0.2 Mn 0.2 O2, with a mass of 5 kg and a substrate temperature of 110 °C.

[0128] (3) Weigh out 140 mL of a 6% disodium hydrogen phosphate solution, 60 mL of a 25.56% ferrous nitrate solution, 40 mL of a 23.85% cobalt nitrate solution, and 40 mL of a 23.33% manganese nitrate solution respectively. After heating to 60 °C, they are sequentially coated onto the high-speed flowing intermediate in a spray manner to obtain a coated material, and the spray speed is 20 mL / min.

[0129] (4) Transfer the coated material from step (3) to a box-type sintering furnace for calcination. The heating rate is 3 °C / min, the calcination temperature is 650 °C, the calcination time is 6 h, and the calcination atmosphere is oxygen. After cooling through a 300-mesh sieve after taking out of the furnace, a core-shell structured ternary cathode material is obtained.

[0130] The core layer structural formula of the prepared core-shell structured ternary cathode material is: LiNi 0.6 Co 0.2 Mn 0.2 O2, and the shell layer structural formula is: 0.33LiNi 0.9 Co 0.05 Mn 0.05 O2, 0.33LiFePO4, 0.33LiCo 0.5 Mn 0.5 O2, and the total mass ratio of the shell layer is 0.6%.

[0131] I. Capacity experiment

[0132] Test method: Measure the capacity data of the core-shell structured ternary cathode materials obtained in Examples 1-6 and Comparative Examples 1-5 under the conditions of a test voltage of 2.8 - 4.35 V, a test rate of 0.1 C, and a test temperature of 25 °C.

[0133] Please refer to Table 1 for the test results.

[0134] Table 1. Discharge capacity of the core-shell structured ternary material

[0135]

[0136] As can be seen from Table 1, Example 1 has a higher capacity. In Example 2, in order to reduce the amount of shell coating, the impact on the capacity is not obvious, but it can be seen from the cycle curve that the cycle retention rate will be reduced; in Example 3, the capacity is significantly reduced, indicating that a higher calcination temperature will affect the capacity of the final calcined material; in Example 4, the capacity is lower, mainly because the adjustment of the coating layer components inhibits the intercalation and deintercalation of lithium ions; as can be seen from Comparative Example 1, Comparative Example 1 omits the coating of the metal salt solution in Example 1 and directly sinters the coated material, and its discharge specific capacity and discharge efficiency are lower than those in Example 1. As can be seen from Comparative Example 2, Comparative Example 2 omits the coating of the ternary dispersion liquid, resulting in its charge specific capacity, discharge specific capacity and discharge efficiency being lower than those in Example 1. In Comparative Example 3, the metal salt solution is coated first and then the ternary dispersion liquid is coated, and the charge specific capacity, discharge specific capacity and discharge efficiency of the obtained product are slightly lower than those in Example 1. It can be seen from the cycle curve that its cycle stability will deteriorate. In the product finally obtained in Comparative Example 4, the mass percentages of the film coating layer and the island-shaped coating layer are not within the scope of this application, and its effect is also worse than that in Example 1. In Comparative Example 5, the total mass percentage of the shell layer exceeds 1%. At this time, its effect is also worse than that in Examples 1-6, indicating that when the coating amount is too high, it will affect the capacity performance of the material.

[0137] II. Cycle Stability Experiment

[0138] Test method: The core-shell structured ternary cathode materials obtained in Examples 1-6 and Comparative Examples 1-5 were cycled 80 times at a rate of 1C under the conditions of a test voltage of 2.8-4.35V and a test temperature of 25°C, and the corresponding capacity retention rate was measured.

[0139] For the test results, please refer to Figure 4 , from Figure 4 it can be seen that Example 1 has better cycle stability. After 80 cycles, the capacity retention rate is 86.56%, and its cycle stability is better than that of Comparative Examples 1-5.

[0140] III. Rate Performance Experiment

[0141] Test method: The core-shell structured ternary cathode materials obtained in Example 1 and Comparative Examples 1-2 were tested at test voltages of 2.8-4.35V and a test temperature of 25°C. The test rates were 0.1C, 0.2C, 0.5C, 1C, 2C, 3C, and 0.1C, and each rate was cycled twice.

[0142] For the test results, please refer to Figure 5 , from Figure 5 it can be seen that Example 1 has better rate performance.

[0143] In summary, the preparation method of the core-shell structured ternary cathode material provided by this application can achieve the recycling and reuse of the washing waste liquid of nickel-rich ternary materials. It obtains a ternary suspension with a certain concentration through vacuum distillation, and cooperates with a dispersant to improve the dispersibility of suspension particles. The ternary substrate is coated for the first time with a ternary dispersion liquid, and then coated for the second time in combination with a metal salt solution. The product obtained by sintering will adhere to the ternary fine powder on the surface of the substrate and melt on the surface of the substrate, thereby forming a stable coating layer, taking into account both ionic conductivity and electrical conductivity. After sieving, a mixed-phase core-shell coating layer is obtained, and the obtained shell layer is a mixed-phase coating layer, which is composed of a spinel / shale-phase film coating layer and an island-shaped coating layer obtained by the reaction of the metal salt solution with residual lithium. It can effectively protect the inner core substrate from electrolyte corrosion, reduce side reactions, and reduce gas generation, thereby obtaining a ternary cathode material with long cycle life and low gas production. The present invention adopts a secondary spraying method, so that the coating dew point that may exist in the primary spraying can be filled in the secondary spraying, and the coating layer is denser and more uniform. Moreover, the coating environment is carried out at a certain temperature, which is also beneficial to improving the fluidity of the material. The mutual friction between the primary particles and the spray droplets improves the coating effect. The present invention provides a method for recycling and reusing the washing waste liquid of nickel-rich ternary materials, avoiding economic losses and resource waste in the waste liquid treatment process, and at the same time providing a solution to the possible environmental pollution. The present invention will produce obvious economic and social benefits. The obtained core-shell structured ternary cathode material has a stable coating shell, taking into account both ionic conductivity and certain electrical conductivity, and has excellent cycle performance and rate performance.

[0144] The foregoing are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A core-shell structured ternary cathode material, characterized in that, It includes a core layer and a shell layer. The general formula of the core layer is LiNi x Co y Mn (1-x-y) O2, where 0.3 ≤ x < 1, y > 0, and 1 - x - y > 0. The shell layer includes a film-forming coating layer and an island-shaped coating layer. The film-forming coating layer covers the surface of the core layer, and the island-shaped coating layer covers the surface of the film-forming coating layer; the film-forming coating layer is a ternary fine powder with the general formula LiNi a Co b Mn (1-a-b) O2, where 0.7 ≤ a < 1, b > 0, and 1 - a - b > 0. Stir the nickel-rich ternary washing waste liquid to obtain a ternary dispersion liquid. The main component of the nickel-rich ternary washing waste liquid is ternary fine powder. Coating the ternary dispersion liquid on a ternary substrate forms the film-forming coating layer; the island-shaped coating layer is obtained by reacting a metal salt solution with the residual lithium on the core layer and the film-forming coating layer; The mass percentage of the core layer and the shell layer is 99% - 99.95%: 0.05% - 1%; the mass percentage of the film coating layer and the island coating layer in the shell layer is 20% - 40%: 60% - 80%; The metal salt solution includes an iron solution, a cobalt solution, and a manganese solution. The island coating is a cobalt-rich lithium manganese compound and lithium iron phosphate. The general formula of the cobalt-rich lithium manganese compound is LiCo c Mn (1-c) O2, where 0.2 ≤ c < 1 and 1 - c > 0.

2. The core-shell structured ternary cathode material according to claim 1, wherein The mass concentration of any one of the metal salt solutions is 1% - 30%.

3. The core-shell structured ternary cathode material according to claim 1, wherein The iron solution includes at least one of ferrous nitrate, ferric sulfate and ferric chloride; the cobalt solution includes at least one of cobalt nitrate, cobalt sulfate and cobalt chloride; the manganese solution includes at least one of manganese nitrate, manganese sulfate and manganese chloride.

4. A method for preparing the core-shell structured ternary cathode material according to any one of claims 1-3, characterized in that, It includes: (1) Stir the nickel-rich ternary washing waste liquid, and perform vacuum distillation to obtain a ternary suspension. Add a dispersant to obtain a ternary dispersion liquid. Among them, the main component in the nickel-rich ternary washing waste liquid is ternary micro-powder, and the general formula of the ternary micro-powder is LiNi a Co b Mn (1-a-b) O2, where 0.7 ≤ a < 1, b > 0, and 1 - a - b > 0. The dispersant is at least one of sodium pyrophosphate solution, sodium tripolyphosphate, and sodium hexametaphosphate; (2) Coating the ternary dispersion liquid on a ternary substrate to form a film coating layer, thereby obtaining an intermediate; the general formula of the ternary substrate is LiNi x Co y Mn (1-x-y) O2, where 0.3 ≤ x < 1, y > 0, and 1 - x - y > 0; (3) Coating the metal salt solution on the intermediate to obtain a coated material; (4) Sintering the coated material to form an island coating layer, and obtaining a core-shell structured ternary cathode material after cooling and sieving.

5. The preparation method of the core-shell structured ternary cathode material according to claim 4, characterized in that, The solid content of the ternary fine powder in the rich nickel ternary washing waste liquid is 0.001% - 2%.

6. The preparation method of the core-shell structured ternary cathode material according to claim 5, characterized in that, The components of the rich nickel ternary washing waste liquid further include LiOH and Li2CO3. Before vacuum distillation, the mass concentration of LiOH is 0.01% - 0.8%, and the mass concentration of Li2CO3 is 0.01% - 0.6%; after vacuum distillation, the mass concentration of LiOH is 0.1% - 8%, and the mass concentration of Li2CO3 is 0.1% - 6%.

7. The preparation method of the core-shell structured ternary cathode material according to claim 5, characterized in that, The solid content of the ternary suspension after vacuum distillation of the rich nickel ternary washing waste liquid is 1% - 20%.

8. The preparation method of the core-shell structured ternary cathode material according to claim 4, wherein, The mass concentration of the sodium pyrophosphate solution is 1% - 6%.

9. The preparation method of the core-shell structured ternary cathode material according to claim 4, characterized in that, The volume ratio of the ternary suspension to the dispersant is 5 - 10: 7 - 14.

10. The preparation method of the core-shell structured ternary cathode material according to claim 4, characterized in that, Coating the ternary dispersion on the ternary substrate includes coating the ternary dispersion on the mixed-flow ternary substrate in a spray manner.

11. The preparation method of the core-shell structured ternary cathode material according to claim 10, wherein, The temperature of the ternary dispersion is 25 - 90°C; the temperature of the ternary substrate is 25 - 150°C.

12. The preparation method of the core-shell structured ternary cathode material according to claim 10, characterized in that, The speed of the spray is 1 - 200 mL / min.

13. The preparation method of the core-shell structured ternary cathode material according to claim 10, characterized in that, The mixed-flow method includes at least one of ball milling, plow blade mixing, mechanical mixing and gas flow mixing.

14. The preparation method of the core-shell structured ternary cathode material according to claim 4, wherein Coating the metal salt solution on the intermediate includes coating the metal salt solution on the mixed-flow intermediate in a spray manner.

15. The preparation method of the core-shell structured ternary cathode material according to claim 14, characterized in that, The temperature of the metal salt solution is 25 - 90°C, and the temperature of the intermediate is 25 - 150°C.

16. The preparation method of the core-shell structured ternary cathode material according to claim 14, characterized in that, The metal salt solution includes an iron solution, a cobalt solution and a manganese solution.

17. The preparation method of the core-shell structured ternary cathode material according to claim 14, characterized in that, The mass concentration of any one of the metal salt solutions is 1% - 30%.

18. The preparation method of the core-shell structured ternary cathode material according to claim 4, wherein, The volume ratio of the ternary suspension to the metal salt solution is 5 - 10: 7 - 14.

19. The preparation method of the core-shell structured ternary cathode material according to claim 4, characterized in that, The sintering temperature is 300 - 800°C, the heating rate is 1°C / min - 6°C / min, and the holding time is 2 - 10 h.

20. The preparation method of the core-shell structured ternary cathode material according to claim 4, wherein, The sintering is carried out in air, oxygen, nitrogen or a mixed atmosphere.

21. The preparation method of the core-shell structured ternary cathode material according to claim 4, wherein The sieve mesh number for cooling and sieving is 100 mesh - 500 mesh.

22. A lithium-ion battery, characterized in that, It includes a core-shell structured ternary cathode material obtained by using the core-shell structured ternary cathode material described in any one of claims 1 - 3 or the preparation method of the core-shell structured ternary cathode material described in any one of claims 4 - 21.

Images