A high-nickel precursor material with a multi-layer structure and a preparation method and application thereof

Abstract

The application provides a high-nickel precursor material with a multilayer structure and a preparation method and application thereof. The preparation method adopts a coprecipitation method and is divided into four stages. Through first-stage coprecipitation, nucleation is completed, and a loose and porous ternary nickel-cobalt-manganese inner core is generated. Through second-stage coprecipitation, a niobium-doped layer is formed. Through third-stage coprecipitation, a dense ternary nickel-cobalt-manganese outer shell is formed. Through fourth-stage coprecipitation, a coating layer containing metal M is formed on the outermost layer. Thus, the high-nickel precursor material with uniform particle size distribution, high sphericity, uniform doping, certain gradient distribution and multilayer structure can be obtained. The prepared positive electrode material can improve the discharge capacity, rate performance and cycle performance of a lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to lithium ion batteries, in particular to a high-nickel precursor material with a multi-layer structure and a preparation method and application thereof. BACKGROUND

[0002] Currently, lithium ion batteries, referred to as LIB, are widely used in various devices, and it is expected that the market of lithium ion batteries will grow more than five times in the next ten years, especially the rapid popularization of medium and large power batteries for electric vehicles (EV, PHEV, HEV, etc.) and energy storage systems (ESS) will drive the growth of the lithium ion battery market. In recent years, the new energy vehicle market has become the main driving force for the rapid development of the global lithium battery industry. In addition, as an important part of grid energy storage technology, electrochemical energy storage plays an increasingly important role in peak load shifting, new energy grid connection and power system auxiliary services.

[0003] The prior art generally uses hydrogen-oxygen co-precipitation and calcination methods to prepare ternary cathode materials. For example, in CN113651371A, a mixed metal ion aqueous solution is pumped into a tank reactor at a controllable rate under nitrogen conditions, and an aqueous solution of alkali and ammonia is pumped into the tank reactor, a co-precipitation reaction occurs, then after washing, filtering and drying, a hydroxide precursor is obtained, then the hydroxide precursor and LiOH are mixed and calcined at a high temperature under a flowing oxygen atmosphere to obtain the final product. The obtained ternary cathode material can be subjected to surface modification treatment, by coating some metal compounds, lithium salts or conductive carbon materials with appropriate thickness on the surface of the ternary material, the direct contact of the active material with the electrolyte can be isolated, the occurrence of side reactions can be reduced, and the dissolution of transition metal ions can be inhibited. For example, CN110190254A discloses a preparation method of lithium phosphate coated ternary cathode material for lithium ion batteries, which comprises the following steps:

[0004] (1) Dissolve the phosphoric acid source in an organic solvent to form a solution, the mass fraction of the phosphoric acid source in the solution is 0.05-0.8%; (2) Add the ternary cathode material for lithium ion batteries to the solution in step (1), stir for 5-120 minutes to make it uniformly dispersed, then dry until the organic solvent is completely evaporated, to obtain the lithium phosphate coated ternary cathode material for lithium ion batteries.

[0005] However, an excess of lithium salt is generally added to the ternary cathode material during the preparation process to prevent lithium loss during the sintering process, therefore, free lithium ions always exist on the surface of the material, which can easily react with H2O and CO2 in the air to generate basic substances LiOH and Li2CO3, the formation of surface residual alkali seriously hinders the performance of the ternary cathode material itself. Moreover, in order to ensure that Ni 2+ can be oxidized to Ni 3+, a large amount of oxygen will be needed in the calcination process, otherwise Ni 2+ and Li + will produce a large amount of cationic disorder due to similar ionic radii, thereby affecting the electrochemical performance of the positive electrode material.

[0006] Surface modification treatment is an effective means to improve the cycle stability of ternary positive electrode materials, but the modification effect of improving the interface stability of the oxidized positive electrode is limited to the surface of the active material particles, and the coating effect is greatly related to the interface compatibility of the coating layer and the active material. At the same time, the individual modification synthesis process conditions are relatively harsh, and the preparation cost is high.

[0007] In summary, there is a need to develop a high-nickel precursor material with a multi-layer structure and its preparation method and application. SUMMARY

[0008] In view of the problems in the prior art, the present application provides a high-nickel precursor material with a multi-layer structure and its preparation method and application. The preparation method adopts a co-precipitation method and is divided into four stages. Through first-stage co-precipitation, nucleation is completed, and a loose and porous ternary nickel-cobalt-manganese inner core is generated. Through second-stage co-precipitation, a niobium-doped layer is formed. Through third-stage co-precipitation, a dense ternary nickel-cobalt-manganese outer shell is formed. Through fourth-stage co-precipitation, a coating layer containing metal M is formed on the outermost layer. Thus, a high-nickel precursor material with uniform particle size distribution, high sphericity, uniform doping, certain gradient distribution, and multi-layer structure can be obtained. The prepared positive electrode material can improve the discharge capacity, rate performance, and cycle performance of lithium ion batteries.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] One of the purposes of the present application is to provide a preparation method of a high-nickel precursor material with a multi-layer structure, which comprises the following steps:

[0011] The nickel-cobalt-manganese ternary solution, the precipitant solution, and the complexing agent solution are injected into the reaction bottom liquid in parallel flow to perform first-stage co-precipitation;

[0012] After reaching the first target particle size, the niobium salt-containing solution is further injected in parallel flow, and four parallel injections are maintained to perform second-stage co-precipitation;

[0013] After reaching the second target particle size, the injection of the niobium salt-containing solution is stopped, and three parallel injections are maintained to perform third-stage co-precipitation;

[0014] After reaching the third target particle size, the coating agent solution and the dispersant solution are further injected in parallel flow, and five parallel injections are maintained to perform fourth-stage co-precipitation;

[0015] After reaching the final target particle size, the material undergoes solid-liquid separation, washing, drying, slurry treatment, sand milling, and spray pyrolysis in sequence to obtain a high-nickel precursor material with a multi-layered structure.

[0016] The coating agent in the coating agent solution is a compound containing metal M, wherein metal M includes at least one of aluminum (Al), titanium (Ti), niobium (Nb), zirconium (Zr), tungsten (W), vanadium (V), strontium (Sr), or gallium (Ga).

[0017] The preparation method described in this invention employs a co-precipitation method and is divided into four stages. In the first stage of co-precipitation, nucleation is completed, generating a loose and porous ternary nickel-cobalt-manganese core. In the second stage of co-precipitation, a niobium-doped layer is formed. In the third stage of co-precipitation, a dense ternary nickel-cobalt-manganese shell is formed. In the fourth stage of co-precipitation, a coating layer containing metal M is formed on the outermost layer. Thus, a high-nickel precursor material with uniform particle size distribution, high sphericity, uniform doping, a certain gradient distribution, and a multilayer structure can be obtained.

[0018] The preparation method described in this invention yields a high-nickel precursor material with a multilayer structure. The internal nucleation site forms a loose and porous structure, which helps to alleviate stress concentration in the material during electrochemical reactions and improves cycle performance. The outer shell surface structure is dense, which helps to increase the tap density of the material, while the gradient distribution structure improves the electrochemical performance of the material.

[0019] The preparation method described in this invention involves niobium doping in the second stage of co-precipitation. During the reaction, niobium oxide is deposited on the surface of the primary particles to reduce the interfacial resistance, avoid polarization, and facilitate rapid lithium-ion transport. At the same time, the Ni-O structure formed on the surface also contributes to structural stability and improves electrochemical cycling performance.

[0020] The preparation method of the present invention adds a surface dispersant in the fourth stage co-precipitation. Due to the steric hindrance, the surface dispersant causes the particles to agglomerate and the surface charge to increase, and the particles repel each other, thereby promoting deagglomeration. This makes the particles more uniformly dispersed and prevents clumping when the positive electrode slurry is coated, thus improving the battery capacity.

[0021] The preparation method described in this invention involves slurry treatment, sand milling, and spray pyrolysis before sintering. The sand milling process makes the co-precipitation doping reaction more uniform, while the spray pyrolysis method effectively reduces the particle size. Granulation forms more uniformly dispersed spheres, avoiding agglomeration. This also facilitates the synthesis of single crystals in the subsequent sintering process, thereby improving the performance of the cathode material.

[0022] As a preferred technical solution of the present invention, the molar ratio of Ni, Co and Mn in the nickel-cobalt-manganese ternary solution is x:y:(1-xy); wherein, 0.8 < x < 1.0, 0 < y < 0.2.

[0023] Preferably, after the fourth stage co-precipitation and before the solid-liquid separation, the general formula of the niobium-containing precursor in the system is Ni. a Co b Mn c Nb d M e (OH)2, where 0.6 < a < 0.9, 0 < b < 0.2, 0 < c < 0.1, 0 < d < 0.1, 0 < e < 0.1, and a + b + c + d + e = 1.

[0024] Preferably, the total concentration of metal ions in the nickel-cobalt-manganese ternary solution is 20-120 g / L, such as 20 g / L, 40 g / L, 60 g / L, 80 g / L, 100 g / L or 120 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] Preferably, the precipitant solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0026] Preferably, the concentration of the precipitant solution is 25-35 wt%, such as 25 wt%, 26 wt%, 28 wt%, 30 wt%, 31 wt%, 33 wt%, or 35 wt%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0027] Preferably, the complexing agent solution is ammonia.

[0028] Preferably, the concentration of the complexing agent solution is 10-15 wt%, such as 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0029] Preferably, the reaction base solution is prepared from pure water, sodium hydroxide solution, and ammonia water, specifically including: adding pure water, sodium hydroxide solution, and ammonia water to the reaction apparatus as the reaction base solution, starting stirring, heating the reaction base solution to 40-60℃, adjusting the pH value of the reaction base solution to 10.0-12.0, the ammonia concentration to 4-6 g / L, introducing N2, and controlling the N2 introduction rate to be 0.2-2 m³ / min. 3 / h.

[0030] Preferably, in the first stage of co-precipitation, the injection flow rate of the complexing agent solution is 500-700 mL / h, such as 500 mL / h, 550 mL / h, 600 mL / h, 650 mL / h or 700 mL / h, etc.; the injection flow rate of the precipitant solution is 1.6-2.0 L / h, such as 1.6 L / h, 1.7 L / h, 1.8 L / h, 1.9 L / h or 2.0 L / h, etc.; and the injection flow rate of the nickel-cobalt-manganese ternary solution is 4-8 L / h, such as 4 L / h, 5 L / h, 6 L / h, 7 L / h or 8 L / h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] Preferably, the pH value of the first stage co-precipitation is 11.0-12.0, such as 11.0, 11.1, 11.3, 11.5, 11.6, 11.8 or 12.0, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the concentration of ammonia co-precipitated in the first stage is 3-5 g / L, such as 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L or 5 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] Preferably, the first target particle size is 1.5-2μm, such as 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm or 2μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] As a preferred technical solution of the present invention, the niobium salt in the niobium salt-containing solution includes at least one of niobium oxalate, niobium sulfate, niobium nitrate, niobium tetrachloride, niobium pentachloride, niobium tetrafluoride, niobium pentafluoride, niobium pentoxide, or niobium oxyphosphate, preferably niobium nitrate.

[0035] Preferably, the concentration of niobium salt in the niobium salt-containing solution is 10-200 g / L, such as 10 g / L, 30 g / L, 50 g / L, 80 g / L, 100 g / L, 130 g / L, 150 g / L, 170 g / L, or 200 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0036] Preferably, in the second stage of co-precipitation, the doping amount of niobium is controlled to be 0.05-5% of the total mass of the ternary nickel, cobalt and manganese elements, such as 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4% or 5%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] It should be noted that the doping amount of niobium described in this invention is controlled at 0.05-5% of the total mass of ternary nickel-cobalt-manganese elements after the entire high-nickel precursor material is prepared.

[0038] As a preferred embodiment of the present invention, in the second stage of co-precipitation, the injection flow rate of the complexing agent solution is 600-800 mL / h, for example, 600 mL / h, 650 mL / h, 700 mL / h, 750 mL / h, or 800 mL / h, and the injection flow rate of the precipitant solution is 2.2-3.0 L / h, for example, 2.2 L / h, 2.4 L / h, 2.5 L / h, 2.6 L / h, 2.8 L / h, or 3.0 L / h. For example, the injection flow rate of the nickel-cobalt-manganese ternary solution is 8-10 L / h, such as 8 L / h, 8.5 L / h, 9 L / h, 9.5 L / h, or 10 L / h, etc., and the injection flow rate of the niobium salt solution is 100-500 mL / h, such as 100 mL / h, 200 mL / h, 300 mL / h, 400 mL / h, or 500 mL / h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] Preferably, the pH value of the second stage coprecipitation is 9.5-10.5, such as 9.5, 9.7, 9.8, 10.0, 10.1, 10.3 or 10.5, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0040] Preferably, the concentration of ammonia co-precipitated in the second stage is 4-6 g / L, such as 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L or 6 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] Preferably, the second target particle size is 3-3.5 μm, such as 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm or 3.5 μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0042] As a preferred embodiment of the present invention, in the third stage co-precipitation, the injection flow rate of the complexing agent solution is 800-900 mL / h, such as 800 mL / h, 820 mL / h, 830 mL / h, 850 mL / h, 870 mL / h, or 900 mL / h, etc.; the injection flow rate of the precipitant solution is 3.0-4.0 L / h, such as 3.0 L / h, 3.1 L / h, 3.3 L / h, 3.5 L / h, 3.6 L / h, 3.8 L / h, or 4.0 L / h, etc.; and the injection flow rate of the nickel-cobalt-manganese ternary solution is 10-15 L / h, such as 10 L / h, 11 L / h, 12 L / h, 13 L / h, 14 L / h, or 15 L / h, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] Preferably, the pH value of the third stage co-precipitation is 10.2-11.0, such as 10.2, 10.4, 10.6, 10.8 or 11.0, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0044] Preferably, the concentration of ammonia in the third stage co-precipitation is 6-8 g / L, such as 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L or 8 g / L, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] Preferably, the third target particle size is 4-4.5 μm, such as 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm or 4.5 μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0046] As a preferred technical solution of the present invention, the concentration of the coating agent solution is 10-50 g / L, such as 10 g / L, 20 g / L, 30 g / L, 40 g / L or 50 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0047] Preferably, the dispersant in the dispersant solution is at least one of tetramethylammonium hydroxide, diethylene glycol, polyvinylpyrrolidone (PVP), sodium polyacrylate, triethanolamine, alkyl glycoside, maleic acid-acrylic acid copolymer (MA-AA), polyethylene glycol, or polyacryl alcohol, with tetramethylammonium hydroxide being the most preferred.

[0048] It should be noted that the degree of polymerization of polyvinylpyrrolidone described in this invention is n = 250-300, the degree of polymerization of sodium polyacrylate is n = 3000-5000, the degree of polymerization of maleic acid-acrylic acid copolymer is n = 20-30, the degree of polymerization of alkyl glycoside is n = 1.4-1.6, the degree of polymerization of polyethylene glycol is n = 1000-2000, and the degree of polymerization of polyacryl alcohol is n = 1000-2000.

[0049] Preferably, the concentration of the dispersant in the dispersant solution is 20-100 g / L, such as 20 g / L, 40 g / L, 60 g / L, 80 g / L or 100 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0050] As a preferred embodiment of the present invention, in the fourth stage co-precipitation, the injection flow rate of the complexing agent solution is 900-1000 mL / h, for example 900 mL / h, 910 mL / h, 930 mL / h, 950 mL / h, 970 mL / h, 990 mL / h, or 1000 mL / h, etc.; the injection flow rate of the precipitant solution is 4.0-4.5 L / h, for example 4.0 L / h, 4.1 L / h, 4.2 L / h, 4.3 L / h, 4.4 L / h, or 4.5 L / h, etc.; and the injection flow rate of the nickel-cobalt-manganese ternary solution is 10-15 L / h, for example 1 L / h. The injection flow rate of the coating agent solution is 0 L / h, 11 L / h, 12 L / h, 13 L / h, 14 L / h, or 15 L / h, etc., and the injection flow rate of the dispersant solution is 200-400 mL / h, such as 200 mL / h, 250 mL / h, 300 mL / h, 350 mL / h, or 400 mL / h, etc., but it is not limited to the values ​​listed. Other unlisted values ​​within the above range are also applicable.

[0051] Preferably, the pH value of the fourth stage co-precipitation is 10.2-11.0, such as 10.2, 10.4, 10.6, 10.8 or 11.0, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0052] Preferably, the ammonia concentration in the fourth stage co-precipitation is 6-8 g / L, such as 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L, or 8 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0053] Preferably, the fourth target particle size is 4.5-5μm, such as 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm or 5μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0054] As a preferred technical solution of the present invention, the reaction temperatures of the first stage coprecipitation, the second stage coprecipitation, the third stage coprecipitation, and the fourth stage coprecipitation are the same, all being 40-60℃, such as 40℃, 45℃, 50℃, 55℃, or 60℃, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0055] Preferably, the stirring speeds for the first stage co-precipitation, the second stage co-precipitation, the third stage co-precipitation, and the fourth stage co-precipitation are the same, all between 250-380 r / min, such as 250 r / min, 280 r / min, 300 r / min, 310 r / min, 330 r / min, 350 r / min, or 380 r / min, but are not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0056] Preferably, the washing includes washing at least three times with sodium hydroxide solution and hot water, respectively.

[0057] Preferably, the drying temperature is 100-150℃, such as 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0058] Preferably, the pulping treatment yields a slurry with a solid content of 20-40 wt%, such as 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0059] Preferably, the sanding includes: using zirconium balls with a diameter of 0.1-1mm, such as 0.1mm, 0.3mm, 0.5mm, 0.6mm, 0.8mm or 1mm, and sanding for 2-10 hours, such as 2h, 4h, 6h, 8h or 10h, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0060] Preferably, the inlet temperature of the spray pyrolysis is 200-300℃, such as 200℃, 210℃, 230℃, 250℃, 260℃, 280℃ or 300℃, and the outlet temperature is 80-150℃, such as 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0061] A second objective of this invention is to provide a high-nickel precursor material with a multilayer structure, which is prepared using the preparation method described in one objective.

[0062] The third objective of this invention is to provide an application of a high-nickel precursor material with a multilayer structure, wherein the high-nickel precursor material with a multilayer structure is mixed with a lithium source and sintered to obtain a high-nickel cathode material.

[0063] The high-nickel precursor material with a multi-layered structure is prepared by the preparation method described in one of the objectives, or the high-nickel precursor material with a multi-layered structure is the high-nickel precursor material with a multi-layered structure described in the second objective.

[0064] Preferably, the ratio of the total molar amount of nickel, cobalt, and manganese in the high-nickel precursor material with a multilayer structure to the molar amount of lithium in the lithium source is 1:(1-1.1), such as 1:1, 1:1.01, 1:1.03, 1:1.05, 1:1.07, or 1:1, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0065] Preferably, the sintering includes a first sintering and a second sintering performed sequentially.

[0066] Preferably, the heating rate of the first sintering is 2-6℃ / min, such as 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min or 6℃ / min, the target temperature is 400-700℃, such as 400℃, 450℃, 500℃, 550℃, 600℃, 650℃ or 700℃, and the holding time is 3-6h, such as 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0067] Preferably, the heating rate of the second sintering is 2-6℃ / min, such as 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min or 6℃ / min, etc., the target temperature is 700-1000℃, such as 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, etc., and the holding time is 10-20h, such as 10h, 12h, 14h, 16h, 18h or 20h, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0068] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0069] (1) The preparation method described in this invention adopts a co-precipitation method and is divided into four stages. Through the first stage of co-precipitation, the nucleus is formed and a loose and porous ternary nickel-cobalt-manganese core is generated. Through the second stage of co-precipitation, a niobium-doped layer is formed. Through the third stage of co-precipitation, a dense ternary nickel-cobalt-manganese shell is formed. Through the fourth stage of co-precipitation, a coating layer containing metal M is formed on the outermost layer. Thus, a high-nickel precursor material with uniform particle size distribution, high sphericity, uniform doping, a certain gradient distribution, and a multi-layer structure can be obtained.

[0070] (2) The preparation method described in this invention yields a high-nickel precursor material with a multilayer structure. A loose and porous structure is formed at the nucleation site inside, which helps to alleviate stress concentration in the material during electrochemical reactions and improves cycle performance. The outer shell surface structure is dense, which helps to increase the tap density of the material. The gradient distribution structure improves the electrochemical performance of the material.

[0071] (3) The preparation method described in this invention performs niobium doping in the second stage of co-precipitation. In the reaction, niobium oxide is deposited on the surface of the primary particles to reduce the interfacial resistance, avoid polarization behavior, and facilitate the rapid transport of lithium ions. At the same time, the Ni-O structure formed on the surface is also conducive to the stability of the structure and improves the electrochemical cycle performance.

[0072] (4) In the preparation method described in this invention, a surface dispersant is added in the fourth stage co-precipitation. Due to the steric hindrance, the surface dispersant repels each other as the particles agglomerate and the surface charge increases, thereby promoting deagglomeration and making the particles more uniformly dispersed. This prevents clumping when the positive electrode slurry is coated, thus improving the battery capacity.

[0073] (5) The preparation method described in this invention involves slurry treatment, sand milling, and spray pyrolysis before sintering. The sand milling process makes the co-precipitation doping reaction more uniform, and the spray pyrolysis method effectively reduces the particle size. Granulation forms more uniformly dispersed spheres, avoiding agglomeration. This process is also beneficial for the synthesis of single crystals in the subsequent sintering process, thus improving the performance of the cathode material. Attached Figure Description

[0074] Figure 1 This is the EDS diagram of the niobium-containing precursor hydroxide obtained from the drying process in Example 1 for Nb.

[0075] Figure 2 This is a SEM image of the niobium-containing precursor hydroxide obtained by drying in Example 1;

[0076] Figure 3 This is a cross-sectional SEM image of the niobium-containing precursor hydroxide obtained by drying in Example 1;

[0077] Figure 4 This is a SEM image of the niobium-containing precursor oxide obtained by spray pyrolysis in Example 1. Detailed Implementation

[0078] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0079] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0080] Example 1

[0081] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure, the method comprising the following steps:

[0082] Prepare a nickel-cobalt-manganese ternary solution, a precipitant solution, a complexing agent solution, a niobium-containing salt solution, a coating agent solution, and a dispersant solution. The molar ratio of Ni, Co, and Mn in the nickel-cobalt-manganese ternary solution is 0.83:0.12:0.05, and the total metal ion concentration in the solution is 80 g / L. The precipitant solution is a 30 wt% NaOH solution; the complexing agent solution is a 12 wt% ammonia solution; the niobium-containing salt solution is a 50 g / L niobium nitrate solution; the coating agent solution is a 20 g / L aluminum sulfate solution; and the dispersant solution is a 50 g / L tetramethylammonium hydroxide solution.

[0083] 10m 3 6.7m was added to the reactor. 3 Pure water, a certain amount of NaOH solution and ammonia water were used as the reaction substrate, and 1m 3Nitrogen gas is introduced into the reaction substrate at a rate of / h, and the mixture is stirred at a speed of 100r / min to ensure uniform mixing. Then, the temperature is raised to 55℃, the pH of the reaction substrate is adjusted to 11.5-11.8, the ammonia concentration is 5g / L, and the total alkalinity is controlled to 18g / L.

[0084] The nickel-cobalt-manganese ternary solution, precipitant solution, and complexing agent solution were injected concurrently into the reaction substrate. The injection flow rate of the complexing agent solution was 600 mL / h, the injection flow rate of the precipitant solution was 2.0 L / h, and the injection flow rate of the nickel-cobalt-manganese ternary solution was 6 L / h. The first stage of co-precipitation was carried out, with the pH value controlled at 11.5 and the ammonia concentration at 4 g / L. After the first target particle size of 2 μm was reached, the first stage of co-precipitation ended, and nucleation was completed.

[0085] Further co-current injection of niobium salt solution was carried out, with the injection flow rate of complexing agent solution at 800 mL / h, precipitant solution at 2.5 L / h, nickel-cobalt-manganese ternary solution at 8 L / h, and niobium salt solution at 300 mL / h. The amount of niobium nitrate added was controlled so that the niobium doping amount was 2% of the total mass of the ternary nickel-cobalt-manganese elements. The second stage of co-precipitation was carried out by maintaining four co-current injections. The pH value of the second stage of co-precipitation was controlled at 10.0 and the ammonia concentration was 6 g / L. After the second target particle size of 3.5 μm was reached, the second stage of co-precipitation was completed.

[0086] Stop the injection of the niobium salt solution. The injection flow rate of the complexing agent solution is 800 mL / h, the injection flow rate of the precipitant solution is 4.0 L / h, and the injection flow rate of the nickel-cobalt-manganese ternary solution is 12 L / h. Maintain the three parallel injections for the third stage of co-precipitation. Control the pH value of the third stage co-precipitation to be 10.5 and the ammonia concentration to be 8 g / L. After the third target particle size of 4 μm is reached, the third stage co-precipitation ends.

[0087] Further co-current injection of coating agent solution and dispersant solution, with the injection flow rate of complexing agent solution being 1000 mL / h, precipitant solution being 4.0 L / h, nickel-cobalt-manganese ternary solution being 15 L / h, coating agent solution being 300 mL / h, and dispersant solution being 300 mL / h, maintaining five co-current injections for the fourth stage of co-precipitation, controlling the pH value of the fourth stage co-precipitation to be 10.5, the ammonia concentration to be 8 g / L, maintaining the ammonia concentration and pH value in the reaction system constant, and stopping the feeding when the particle D50 of the reaction product reaches the final target particle size of 4.5 μm;

[0088] The precursor powder was subjected to solid-liquid separation, washing, and drying in sequence. The washing process included four alkaline washes with sodium hydroxide solution followed by five water washes with hot water. The drying process included drying at 90°C. The resulting precursor powder was transferred to a slurrying kettle for slurrying treatment to obtain a slurry with a solid content of 20 wt%. The slurry was then milled for 8 hours using zirconium balls with a diameter of 0.5 mm. The resulting slurry was then pumped into a spray dryer for spray pyrolysis, with the inlet temperature controlled at 250°C and the outlet temperature at 100°C, to obtain a high-nickel precursor material with a multilayer structure.

[0089] Regarding the niobium-containing precursor hydroxide obtained by drying in this embodiment, Figure 1 The EDS plot for Nb is shown, which shows that Nb is uniformly doped inside the particles and forms a ring of a certain thickness. Figure 2 and Figure 3 SEM images and cross-sectional SEM images are shown respectively. It can be seen that a loose and porous structure is formed at the nucleation site inside the particles, which helps to alleviate stress concentration in the material during electrochemical reactions and improves cycle performance. Meanwhile, the external surface structure is dense and the gradient distribution structure improves the electrochemical performance of the material.

[0090] Figure 4 This is a SEM image of the niobium-containing precursor oxide obtained by spray pyrolysis in this embodiment. As can be seen from the image, spray pyrolysis effectively reduces particle size and avoids agglomeration. It also facilitates the synthesis of single crystals in the subsequent sintering process, thereby improving the performance of the cathode material.

[0091] Example 2

[0092] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Example 1 is that in the second stage co-precipitation, the doping amount of niobium is controlled to be 0.1% of the total mass of the ternary nickel-cobalt-manganese elements.

[0093] Example 3

[0094] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Embodiment 1 is that, in the second stage co-precipitation, the doping amount of niobium is controlled to be 0.2% of the total mass of the ternary nickel-cobalt-manganese elements.

[0095] Example 4

[0096] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Embodiment 1 is that in the second stage co-precipitation, the doping amount of niobium is controlled to be 0.5% of the total mass of the ternary nickel-cobalt-manganese elements.

[0097] Example 5

[0098] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Embodiment 1 is that in the second stage co-precipitation, the amount of niobium doping is controlled to be 1% of the total mass of the ternary nickel-cobalt-manganese elements.

[0099] Example 6

[0100] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure. Compared with Example 1, the only difference is that in the second stage co-precipitation, the doping amount of niobium is controlled to be 5% of the total mass of the ternary nickel-cobalt-manganese elements.

[0101] Example 7

[0102] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Embodiment 1 is that in the second stage co-precipitation, the doping amount of niobium is controlled to be 8% of the total mass of the ternary nickel-cobalt-manganese elements.

[0103] Example 8

[0104] This embodiment provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Embodiment 1 is that in the second stage co-precipitation, the doping amount of niobium is controlled to be 10% of the total mass of the ternary nickel-cobalt-manganese elements.

[0105] Comparative Example 1

[0106] This comparative example provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Example 1 is that no dispersant solution was added in the fourth stage co-precipitation.

[0107] Comparative Example 2

[0108] This comparative example provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Example 1 is that a niobium-containing salt solution is no longer injected in the second-stage co-precipitation, i.e., niobium doping is no longer performed.

[0109] Comparative Example 3

[0110] This comparative example provides a method for preparing a high-nickel precursor material with a multilayer structure. Compared with Example 1, the only difference is that the slurry treatment, sand milling, and spray pyrolysis are completely omitted, and the obtained niobium-containing precursor hydroxide is directly used as a high-nickel precursor material with a multilayer structure.

[0111] Comparative Example 4

[0112] This comparative example provides a method for preparing a high-nickel precursor material with a multilayer structure. The only difference from Example 1 is that sand milling is completely omitted, that is, the slurry obtained by pulping is directly subjected to spray pyrolysis.

[0113] The multi-layered high-nickel precursor material prepared in the above examples and comparative examples was batch-mixed with lithium hydroxide in a high-speed mixer. The ratio of the total molar amount of nickel, cobalt, and manganese in the multi-layered high-nickel precursor material to the molar amount of lithium hydroxide was controlled to be 1:1.05. The resulting mixture was then subjected to a first sintering and a second sintering in a box furnace. The heating rate for the first sintering was 4°C / min, the target temperature was 450°C, and the holding time was 5 hours. The heating rate for the second sintering was 4°C / min, the target temperature was 850°C, and the holding time was 20 hours. The sintered material was cooled, crushed, and sieved to obtain a high-nickel cathode material. The high-nickel cathode material and the conductive... The positive electrode slurry is prepared by mixing the electrolyte and binder PVP in a mass ratio of 8:1:1 and adding them to N-methylpyrrolidone (NMP). The positive electrode slurry is then coated onto aluminum foil. After drying the coated electrode in a vacuum oven at 120°C, it is cut into 12mm diameter discs as the positive electrode and lithium metal sheets as the negative electrode. A separator is used to separate the positive and negative electrodes. The electrolyte is a ternary commercial electrolyte 1MLiPF6 as the solute and a mixture of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1 as the solvent. The negative electrode shell, negative electrode, electrolyte, separator, electrolyte, positive electrode, current collector and positive electrode shell are stacked and pressed together in sequence to form a coin cell lithium-ion battery.

[0114] The prepared coin-type lithium-ion batteries were subjected to electrochemical performance tests. The test voltage was 3.0–4.3V. The initial discharge specific capacity and initial coulombic efficiency were measured at 0.1C, and the capacity retention rate after 100 charge-discharge cycles was measured at 1C. The test results are shown in Table 1.

[0115] Table 1

[0116] Item Initial discharge specific capacity (mAh / g) Initial coulombic efficiency (%) Capacity retention rate (%) Example 1 203.2 93.7 91.4 Example 2 197.5 91.4 87.8 Example 3 202.6 92.8 89.7 Example 4 202.1 91.9 91.0 Example 5 199.3 91.4 89.9 Example 6 202.1 92.7 91.1 Example 7 198.9 91.7 90.9 Example 8 200.2 91.5 90.3 Comparative Example 1 195.2 90.1 88.7 Comparative Example 2 189.7 88.3 83.9 Comparative Example 3 192.4 89.2 85.8 Comparative Example 4 193.6 89.8 86.2

[0117] As can be seen from Table 1, the first discharge capacity and capacity retention rate were the highest in Example 1, indicating that the best electrochemical performance can be obtained when the mass percentage of niobium nitrate doping is controlled at about 2%. At the same time, the data comparison between Example 1 and Comparative Example 1 shows that the use of dispersant can make the particles more uniformly dispersed and improve the battery capacity.

[0118] In summary, the preparation method of this invention employs a co-precipitation method and is divided into four stages. The first stage of co-precipitation completes nucleation, generating a loose and porous ternary nickel-cobalt-manganese core. The second stage of co-precipitation forms a niobium-doped layer. The third stage of co-precipitation forms a dense ternary nickel-cobalt-manganese shell. The fourth stage of co-precipitation forms a coating layer containing metal M on the outermost layer. This yields a high-nickel precursor material with uniform particle size distribution, high sphericity, uniform doping, a certain gradient distribution, and a multilayer structure. The prepared cathode material can improve the discharge capacity, rate performance, and cycle performance of lithium-ion batteries.

[0119] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0120] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0121] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0122] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a high-nickel precursor material with a multilayer structure, characterized in that, The preparation method includes the following steps: The nickel-cobalt-manganese ternary solution, precipitant solution, and complexing agent solution were injected concurrently into the reaction substrate to carry out the first stage of co-precipitation; After reaching the first target particle size, a niobium-containing salt solution is injected in parallel to maintain four parallel injections for the second stage of co-precipitation. Once the second target particle size is reached, the injection of the niobium-containing salt solution is stopped, and the three parallel injections are maintained for the third stage of co-precipitation. After reaching the third target particle size, the coating agent solution and dispersant solution are injected in parallel to maintain five parallel injections for the fourth stage of co-precipitation. After reaching the final target particle size, the material undergoes solid-liquid separation, washing, drying, slurry treatment, sand milling, and spray pyrolysis in sequence to obtain a high-nickel precursor material with a multi-layered structure. In the nickel-cobalt-manganese ternary solution, the molar ratio of Ni, Co, and Mn is x:y:(1-xy); where 0.8 < x < 1.0, 0 < y < 0.2; after the fourth stage co-precipitation and before the solid-liquid separation, the general formula of the niobium-containing precursor in the system is Ni. a Co b Mn c Nb d M e (OH)2, where 0.6 < a < 0.9, 0 < b < 0.2, 0 < c < 0.1, 0 < d < 0.1, 0 < e < 0.1, and a + b + c + d + e = 1; The total concentration of metal ions in the nickel-cobalt-manganese ternary solution is 20-120 g / L; in the first stage of coprecipitation, the injection flow rate of the complexing agent solution is 500-700 mL / h, the injection flow rate of the precipitant solution is 1.6-2.0 L / h, and the injection flow rate of the nickel-cobalt-manganese ternary solution is 4-8 L / h; the pH value of the first stage of coprecipitation is 11.0-12.0; the ammonia concentration of the first stage of coprecipitation is 3-5 g / L; and the first target particle size is 1.5-2 μm. The niobium salt concentration in the niobium-containing salt solution is 10-200 g / L; in the second stage co-precipitation, the niobium doping amount is controlled to be 0.05-5% of the total mass of the ternary nickel-cobalt-manganese elements; in the second stage co-precipitation, the injection flow rate of the complexing agent solution is 600-800 mL / h, the injection flow rate of the precipitant solution is 2.2-3.0 L / h, the injection flow rate of the nickel-cobalt-manganese ternary solution is 8-10 L / h, and the injection flow rate of the niobium salt-containing solution is 100-500 mL / h; the pH value of the second stage co-precipitation is 9.5-10.5; the ammonia concentration of the second stage co-precipitation is 4-6 g / L; the second target particle size is 3-3.5 μm; In the third-stage coprecipitation, the injection flow rate of the complexing agent solution is 800-900 mL / h, the injection flow rate of the precipitant solution is 3.0-4.0 L / h, and the injection flow rate of the nickel-cobalt-manganese ternary solution is 10-15 L / h; the pH value of the third-stage coprecipitation is 10.2-11.0; the ammonia concentration of the third-stage coprecipitation is 6-8 g / L; and the third target particle size is 4-4.5 μm. The coating agent in the coating solution is a compound containing metal M, wherein metal M is composed of at least one of aluminum, titanium, zirconium, tungsten, vanadium, strontium, or gallium; the concentration of the coating agent solution is 10-50 g / L; the dispersant in the dispersant solution is at least one of tetramethylammonium hydroxide, diethylene glycol, polyvinylpyrrolidone, sodium polyacrylate, triethanolamine, alkyl glycoside, maleic acid-acrylic acid copolymer, polyethylene glycol, or polyacryl alcohol; the concentration of the dispersant in the dispersant solution is 20-100 g / L; the fourth stage In the coprecipitation process, the injection flow rate of the complexing agent solution is 900-1000 mL / h, the injection flow rate of the precipitant solution is 4.0-4.5 L / h, the injection flow rate of the nickel-cobalt-manganese ternary solution is 10-15 L / h, the injection flow rate of the coating agent solution is 200-400 mL / h, and the injection flow rate of the dispersant solution is 200-400 mL / h; the pH value of the fourth-stage coprecipitation is 10.2-11.0; the ammonia concentration of the fourth-stage coprecipitation is 6-8 g / L; and the final target particle size is 4.5-5 μm.

2. The preparation method according to claim 1, characterized in that, The niobium salt in the niobium-containing salt solution includes at least one of niobium oxalate, niobium sulfate, niobium nitrate, niobium tetrachloride, niobium pentachloride, niobium tetrafluoride, or niobium pentafluoride.

3. The preparation method according to claim 1, characterized in that, The reaction temperatures for the first stage coprecipitation, the second stage coprecipitation, the third stage coprecipitation, and the fourth stage coprecipitation are all the same, at 40-60℃.

4. The preparation method according to claim 1, characterized in that, The pulping process yields a slurry with a solid content of 20-40 wt%.

5. The preparation method according to claim 1, characterized in that, The grinding process includes: using zirconium balls with a diameter of 0.1-1 mm and grinding for 2-10 hours.

6. The preparation method according to claim 1, characterized in that, The inlet temperature of the spray pyrolysis is 200-300℃, and the outlet temperature is 80-150℃.

7. A high-nickel precursor material with a multilayer structure, characterized in that, It is prepared by the preparation method described in any one of claims 1-6.

8. An application of a high-nickel precursor material with a multilayer structure, characterized in that, A high-nickel cathode material is obtained by mixing a multi-layered high-nickel precursor material with a lithium source and then sintering it. The high-nickel precursor material with a multi-layered structure is prepared by the preparation method described in any one of claims 1-6, or the high-nickel precursor material with a multi-layered structure is the high-nickel precursor material with a multi-layered structure described in claim 7.

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