Precursor material of a multi-layer structure, method for producing the same, cathode material, lithium-ion battery

Abstract

This invention belongs to the field of lithium-ion battery material technology and discloses a precursor for a lithium-ion battery cathode material. The core of the precursor is a nickel-cobalt-manganese hydroxide, and the outer layer is a multilayer structure formed by alternating layers of lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide and nickel-cobalt-manganese hydroxide, with the innermost and outermost layers of the multilayer structure being lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide. Furthermore, this invention discloses a co-precipitation method for preparing the above-mentioned precursor. Lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide is coated onto the surface of the nickel-cobalt-manganese hydroxide, and this coating serves as a repeating component unit to form the precursor. After lithium-ion mixing and sintering, the lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide is converted into high-entropy oxides, which can accelerate lithium-ion transport. Moreover, the spacing of the high-entropy oxides can effectively suppress the cracking of secondary particles, hinder side reactions between the electrode and electrolyte, promote cathode-electrolyte interface kinetics, and improve electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to multilayer precursor materials and their preparation methods. Background Technology

[0002] Coating modification is a commonly used modification method for precursors of cathode materials in lithium-ion batteries. CN113871583A discloses a method for preparing a coated ternary precursor, specifically: dissolving the ternary precursor in water in the presence of a solubilizer to obtain a precursor solution; dissolving a metal salt in an alcohol compound to obtain a coating solution; mixing the coating solution and the precursor solution to achieve wet hydrolysis coating; and then performing solid-liquid separation, washing with water, and vacuum drying to obtain a coated ternary precursor with a surface coated with a metal hydroxide. CN115872459A discloses a double-layer coated ternary precursor, including a core, an inner coating layer covering the outer surface of the core, and an outer coating layer covering the outer surface of the inner coating layer; wherein the core includes a ternary hydroxide, the inner coating layer includes a ternary carbonate, and the outer coating layer includes at least one of aluminum hydroxide, magnesium hydroxide, and titanium hydroxide. The multi-layer coating structure can accelerate lithium-ion transport, while the uniform coating layer can effectively suppress the cracking of secondary particles. Summary of the Invention

[0003] The first objective of this invention is to provide a multilayer coated modified precursor and its preparation method; the second objective of this invention is to provide a cathode material; and the third objective of this invention is to provide a lithium-ion battery.

[0004] To achieve the above objectives, the present invention provides the following specific technical solutions.

[0005] First, the present invention provides a precursor for a lithium-ion battery cathode material. The core of the precursor is a nickel-cobalt-manganese hydroxide, and the core is surrounded by a multilayer structure formed by alternating layers of lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide and nickel-cobalt-manganese hydroxide. The innermost and outermost layers of the multilayer structure are both lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide.

[0006] In a further preferred embodiment, the multi-layer structure has at least three layers.

[0007] In a further preferred embodiment, the core of the precursor has a D50 of 4~5μm; and the thickness of each layer of the multilayer structure is in the range of 1~5μm.

[0008] In a further preferred embodiment, the multilayer structure has 5 layers, which, from the core to the outside, are lanthanum aluminum iron chromium magnesium zinc hydroxide, nickel cobalt manganese hydroxide, lanthanum aluminum iron chromium magnesium zinc hydroxide, nickel cobalt manganese hydroxide, and lanthanum aluminum iron chromium magnesium zinc hydroxide.

[0009] Secondly, the present invention provides a method for preparing the precursor of the above-mentioned lithium-ion battery cathode material, comprising the following steps:

[0010] (1) Prepare a mixed salt solution A of nickel, cobalt, and manganese;

[0011] Prepare a soluble mixed salt solution B of lanthanum salt, aluminum salt, iron salt, chromium salt, magnesium salt, zinc salt and polyethylene glycol;

[0012] Preparation of sodium hydroxide solution C;

[0013] Prepare a mixed solution D of sodium hydroxide and sodium carbonate;

[0014] Preparation of complexing agent solution;

[0015] (2) Mixed salt solution A, sodium hydroxide solution C and complexing agent solution are introduced into reactor I in parallel to carry out a co-precipitation reaction to obtain material I;

[0016] (3) Add material I to reaction vessel II, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material II;

[0017] (4) Add material II to reaction vessel III, and flow in mixed salt solution A, sodium hydroxide solution C and complexing agent solution to carry out co-precipitation reaction to obtain material III;

[0018] (5) Add material III to reaction vessel IV, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material IV;

[0019] Similarly, multilayer precursors can be prepared through a co-precipitation process.

[0020] In a further preferred embodiment, the nickel salt, cobalt salt, and manganese salt used to prepare the mixed salt solution A are at least one of sulfate, nitrate, and chloride salts, respectively.

[0021] In a further preferred embodiment, the total concentration of nickel, cobalt, and manganese metal ions in the mixed salt solution A is 1-5 mol / L.

[0022] In a further preferred embodiment, the lanthanum salt, aluminum salt, iron salt, chromium salt, magnesium salt, and zinc salt are all nitrates.

[0023] In a further preferred embodiment, the molar ratio of lanthanum, aluminum, iron, chromium, magnesium, and zinc in the mixed salt solution B is 1-5:1:1:1:1:1.

[0024] In a further preferred embodiment, the total concentration of lanthanum, aluminum, iron, chromium, magnesium, and zinc ions in the mixed salt solution B is 1-3 mol / L.

[0025] In a further preferred embodiment, the concentration of polyethylene glycol in the mixed salt solution B is 20-30 g / L.

[0026] In a further preferred embodiment, the concentration of the sodium hydroxide solution C is 6-10 mol / L.

[0027] In a further preferred embodiment, the molar ratio of sodium hydroxide to sodium carbonate in the mixed solution D is 1:1-2.

[0028] In a further preferred embodiment, the total molar concentration of sodium hydroxide and sodium carbonate in the mixed solution D is 1-5 mol / L.

[0029] In a further preferred embodiment, the complexing agent is ammonia.

[0030] In a further preferred embodiment, the concentration of the complexing agent solution is 8-13 mol / L.

[0031] In a further preferred embodiment, the temperature of the coprecipitation reaction described in steps (2), (4) and the corresponding analogous steps is 50-60℃, the reaction atmosphere is a nitrogen atmosphere or an inert gas atmosphere, and the pH value of the reaction system is 11.5-13.5.

[0032] In a further preferred embodiment, the temperature of the coprecipitation reaction described in steps (3), (5) and the corresponding analogous steps is 60-80℃, and the reaction atmosphere is a nitrogen atmosphere or an inert gas atmosphere.

[0033] In a further preferred embodiment, steps (2), (4) and the corresponding analogous steps can be carried out in the same reactor.

[0034] In a further preferred embodiment, steps (3), (5), and the corresponding analogous steps can be carried out in the same reactor.

[0035] Based on the same inventive concept, the present invention provides a lithium-ion battery cathode material, which is obtained by sintering the aforementioned precursor mixed with lithium.

[0036] In addition, the present invention provides a lithium-ion battery comprising the above-mentioned positive electrode material.

[0037] One or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0038] This invention forms a precursor by coating a nickel-cobalt-manganese hydroxide with a lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide, using this as a repeating unit. After lithium-ion mixing and sintering, the lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide transforms into high-entropy oxides, which accelerate lithium-ion transport. Furthermore, the spacing of these high-entropy oxides effectively suppresses secondary particle cracking, hinders side reactions between the electrode and electrolyte, promotes cathode-electrolyte interface kinetics, and improves electrochemical performance.

[0039] The process of this invention is easy to control, simple to operate, and can be continuously produced, making it suitable for large-scale commercial applications.

[0040] The preparation method provided by this invention can directly utilize existing equipment in the factory, has low equipment requirements, and is easy to directly industrialize. Attached Figure Description

[0041] Figure 1 The image shows the SEM image of the precursor obtained in Example 1. Detailed Implementation

[0042] First, the present invention provides a precursor for a lithium-ion battery cathode material. The core of the precursor is a nickel-cobalt-manganese hydroxide, and the core is surrounded by a multilayer structure formed by alternating layers of lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide and nickel-cobalt-manganese hydroxide. The innermost and outermost layers of the multilayer structure are both lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide.

[0043] A precursor is formed by coating a nickel-cobalt-manganese hydroxide with a lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide, using this component as a repeating unit. The number of repeating unit units is at least two, and this invention further claims protection for a number of three repeating unit units. When the number of repeating units is three, the performance of both the precursor and the cathode material is superior, and the cost is lower. Specifically, in a particularly preferred embodiment of this invention, the multilayer structure has five layers, from the core to the outside: lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide, nickel-cobalt-manganese hydroxide, lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide, nickel-cobalt-manganese hydroxide, and lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide.

[0044] Preferably, the core of the precursor has a D50 of 4~5μm; and the thickness of each layer of the multilayer structure is in the range of 1~5μm.

[0045] Furthermore, the present invention utilizes a co-precipitation method to construct repeating units.

[0046] The method for preparing the precursor of the above-mentioned lithium-ion battery cathode material provided by the present invention includes the following steps:

[0047] (1) Prepare a mixed salt solution A of nickel, cobalt, and manganese;

[0048] Prepare a soluble mixed salt solution B of lanthanum salt, aluminum salt, iron salt, chromium salt, magnesium salt, zinc salt and polyethylene glycol;

[0049] Preparation of sodium hydroxide solution C;

[0050] Prepare a mixed solution D of sodium hydroxide and sodium carbonate;

[0051] Preparation of complexing agent solution;

[0052] (2) Mixed salt solution A, sodium hydroxide solution C and complexing agent solution are introduced into reactor I in parallel to carry out a co-precipitation reaction to obtain material I;

[0053] (3) Add material I to reaction vessel II, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material II;

[0054] (4) Add material II to reaction vessel III, and flow in mixed salt solution A, sodium hydroxide solution C and complexing agent solution to carry out co-precipitation reaction to obtain material III;

[0055] (5) Add material III to reaction vessel IV, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material IV;

[0056] Similarly, multilayer precursors can be prepared through a co-precipitation process.

[0057] In a particularly preferred embodiment of the present invention, the method for preparing the precursor of the lithium-ion battery cathode material includes the following steps:

[0058] (1) Prepare a mixed salt solution A of nickel, cobalt, and manganese;

[0059] Prepare a soluble mixed salt solution B of lanthanum salt, aluminum salt, iron salt, chromium salt, magnesium salt, zinc salt and polyethylene glycol;

[0060] Preparation of sodium hydroxide solution C;

[0061] Prepare a mixed solution D of sodium hydroxide and sodium carbonate;

[0062] Preparation of complexing agent solution;

[0063] (2) Mixed salt solution A, sodium hydroxide solution C and complexing agent solution are introduced into reactor I in parallel to carry out a co-precipitation reaction to obtain material I;

[0064] (3) Add material I to reaction vessel II, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material II;

[0065] (4) Add material II to reaction vessel III, and flow in mixed salt solution A, sodium hydroxide solution C and complexing agent solution to carry out co-precipitation reaction to obtain material III;

[0066] (5) Add material III to reaction vessel IV, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material IV;

[0067] (6) Add material IV to reactor V, and flow in mixed salt solution A, sodium hydroxide solution C and complexing agent solution to carry out co-precipitation reaction to obtain material V;

[0068] (7) Add material V to reactor VI and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain a multilayer precursor.

[0069] In the solution preparation process of step (1), the nickel salt, cobalt salt, and manganese salt used to prepare the mixed salt solution A can be soluble salts. In a specific embodiment of the present invention, the nickel salt, cobalt salt, and manganese salt used to prepare the mixed salt solution A are at least one of sulfate, nitrate, and chloride salts, respectively.

[0070] Based on experimental and industrial experience, in some specific embodiments of the present invention, the total concentration of nickel, cobalt, and manganese in the mixed salt solution A is 1-5 mol / L, more preferably 2-4 mol / L. The molar ratio of nickel, cobalt, and manganese can be freely formulated by those skilled in the art according to actual conditions. For example, it can be formulated based on NCM532, NCM622, NCM811, etc.

[0071] In specific embodiments of the present invention, the lanthanum salt, aluminum salt, iron salt, chromium salt, magnesium salt, and zinc salt are all nitrates. Those skilled in the art should understand that soluble salts of lanthanum, aluminum, iron, chromium, magnesium, and zinc salts can all be used in the present invention, and they can choose freely. Considering the high solubility of nitrates in aqueous solutions, nitrates are therefore chosen in specific embodiments of the present invention.

[0072] In a specific embodiment of the present invention, the molar ratio of lanthanum, aluminum, iron, chromium, magnesium, and zinc in the mixed salt solution B is 1-5:1:1:1:1:1. This molar ratio of lanthanum, aluminum, iron, chromium, magnesium, and zinc is beneficial for the formation of high-entropy oxides during the subsequent roasting process.

[0073] In a specific embodiment of the present invention, the total concentration of the metal elements lanthanum, aluminum, iron, chromium, magnesium and zinc in the mixed salt solution B is 1-3 mol / L, more preferably 2-3 mol / L.

[0074] In a specific embodiment of the present invention, the concentration of polyethylene glycol in the mixed salt solution B is 20-30 g / L.

[0075] In a specific embodiment of the present invention, the concentration of the sodium hydroxide solution C is 6-10 mol / L, more preferably 8-10 mol / L.

[0076] In a specific embodiment of the present invention, when co-precipitating lanthanum, aluminum, iron, chromium, magnesium, and zinc, a mixed solution of sodium hydroxide and sodium carbonate is selected as the precipitant. Sodium hydroxide and sodium carbonate together provide an alkaline environment for the precipitation of the metal elements. Sodium hydroxide is strongly alkaline, and may cause the precipitate to redissolve during the precipitation process. Adding sodium carbonate can neutralize its alkalinity, allowing the precipitation reaction to proceed normally. Further, the molar ratio of sodium hydroxide to sodium carbonate in the mixed solution D is 1:1-2. Further, the total molar concentration of sodium hydroxide and sodium carbonate in the mixed solution D is 1-5 mol / L.

[0077] Furthermore, during the co-precipitation process, the total molar amount of sodium hydroxide and sodium carbonate in the mixed solution D should be sufficient to precipitate the target amounts of lanthanum, aluminum, iron, chromium, magnesium, and zinc.

[0078] In a specific embodiment of the present invention, the complexing agent is ammonia. However, those skilled in the art should understand that other commonly used complexing agents in the art can also be used. Further, the concentration of the complexing agent is 8-13 mol / L, preferably 8-10 mol / L.

[0079] In a specific embodiment of the present invention, the temperature of the coprecipitation reaction described in steps (2), (4) and the corresponding analogous steps is 50-60°C, the reaction atmosphere is a nitrogen atmosphere or an inert gas atmosphere, and the pH value of the reaction system is 11.5-13.5.

[0080] In a specific embodiment of the present invention, the temperature of the coprecipitation reaction described in steps (3), (5) and the corresponding analogous steps is 60-80°C, and the reaction atmosphere is a nitrogen atmosphere or an inert gas atmosphere.

[0081] In a specific embodiment of the present invention, steps (2), (4) and the corresponding analogous steps can be carried out in the same reaction vessel.

[0082] In a specific embodiment of the present invention, steps (3), (5) and the corresponding analogous steps can be carried out in the same reaction vessel.

[0083] In a particularly preferred embodiment of the present invention, the temperature of the co-precipitation reaction in steps (2), (4), and (6) is 50-60°C, the reaction atmosphere is a nitrogen atmosphere or an inert gas atmosphere, and the pH value of the reaction system is 11.5-13.5. The reaction temperature mainly affects the chemical reaction rate. The higher the temperature, the faster the reaction rate, but excessively high temperatures can cause problems such as precursor oxidation and uncontrollable reaction processes, while excessively low temperatures can make the reaction difficult to proceed. The pH value during the precipitation process directly affects the formation and growth of crystal particles. If the pH value is too high or too low, the product quality will drop sharply, resulting in unqualified products.

[0084] In a particularly preferred embodiment of the present invention, the temperature of the coprecipitation reaction in steps (3), (5), and (7) is 60-80°C, and the reaction atmosphere is a nitrogen atmosphere or an inert gas atmosphere.

[0085] In a particularly preferred embodiment of the present invention, the particle size D50 of material I is 4-5 μm; the particle size D50 of material II is 5-6 μm; the particle size D50 of material III is 9-10 μm; the particle size D50 of material IV is 10-11 μm; the particle size D50 of material V is 14-15 μm; and the particle size D50 of the precursor is 15-16 μm. Those skilled in the art will understand that the particle size range can be further adjusted based on further optimization of the material properties, which is very easy to do.

[0086] Furthermore, in a particularly preferred embodiment of the present invention, steps (2), (4), and (6) involve the co-precipitation of nickel-cobalt-manganese hydroxides, which can be carried out in the same or different reaction vessels, and can be designed according to actual conditions in the actual industrialization process. Similarly, steps (3), (5), and (7) involve the co-precipitation of lanthanum, aluminum, iron, chromium, magnesium, and zinc, which can also be carried out in the same or different reaction vessels, and can be designed according to actual conditions in the actual industrialization process.

[0087] Based on the same inventive concept, the present invention provides a lithium-ion battery cathode material, which is obtained by sintering the aforementioned precursor mixed with lithium.

[0088] In addition, the present invention provides a lithium-ion battery comprising the above-mentioned positive electrode material.

[0089] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0090] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0091] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0092] Example 1

[0093] (1) Prepare a mixed salt solution A of nickel, cobalt, and manganese by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in water; wherein the total molar concentration of the three elements is 2 mol / L, and the molar ratio of nickel, cobalt, and manganese is 0.8:0.1:0.1. Prepare a sodium hydroxide solution C with a concentration of 8 mol / L. Prepare an ammonia solution with a concentration of 10 mol / L. Prepare a mixed solution B of metal nitrates and polyethylene glycol, wherein the molar ratio of lanthanum nitrate, aluminum nitrate, iron nitrate, chromium nitrate, magnesium nitrate, and zinc nitrate is 5:1:1:1:1:1, the total molar concentration of the metal elements lanthanum, aluminum, iron, chromium, magnesium, and zinc is 3 mol / L, and the concentration of polyethylene glycol is 20 g / L. Prepare a mixed solution D of NaOH and Na2CO3, wherein the molar ratio of sodium hydroxide to sodium carbonate is 1:2, and the total molar concentration is 3 mol / L.

[0094] (2) Under a nitrogen atmosphere, mixed salt solution A, sodium hydroxide solution C, and ammonia solution were pumped into reactor 1 using different peristaltic pumps to carry out the first stage coprecipitation reaction. The conditions for controlling the coprecipitation reaction were: temperature 55℃, pH 12.5, stirring speed 500 rpm, and free ammonia concentration 14.5 g / L. When the particle size of the precipitate reached 4 μm, the feeding was stopped, and material I was obtained.

[0095] (3) Transfer material I to reactor 2#, and feed the prepared solution B and mixed solution D into reactor 2# at a constant speed using metering pumps, with the feeding speed controlled at 400 mL / min. Control the reaction temperature at 70℃ and the stirring speed at 500 rpm. Stop feeding when the particle size of the precipitate reaches 5μm, and obtain material II.

[0096] (4) Transfer material II to reactor 1# and carry out the reaction as described in step (2) to obtain material III, the particle size of material III reaches 9μm.

[0097] (5) Transfer material III to reactor 2# and carry out the reaction as described in step (3) to obtain material IV, the particle size of material IV reaches 10μm.

[0098] (6) Transfer material IV to reactor 1# and carry out the reaction as described in step (2) to obtain material V, the particle size of material V reaches 14μm.

[0099] (7) Transfer material V to reactor 2# and carry out the reaction as described in step (3) to obtain precursor slurry with a particle size of 15μm.

[0100] (8) The precursor slurry is filtered, washed and dried to obtain a multi-layered precursor material.

[0101] (9) The obtained multilayer precursor material and lithium hydroxide monohydrate were ball-milled and mixed at a molar ratio of 1:1.05. Then, the mixture was calcined at 500°C for 4 h in an oxygen atmosphere, followed by calcination at 900°C for 16 h to obtain the cathode material.

[0102] Figure 1 The image shows the SEM image of the precursor material obtained in Example 1. It can be seen that the precursor is spherical and has a smooth surface.

[0103] Comparative Example 1

[0104] The difference between Comparative Example 1 and Example 1 is that the precursor has only a two-layer structure, consisting of a nickel-cobalt-manganese hydroxide coated with a lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide. The specific process is as follows:

[0105] (1) Same as step (1) in Example 1.

[0106] (2) Under a nitrogen atmosphere, mixed salt solution A, sodium hydroxide solution C, and ammonia solution were pumped into reactor 1 using different peristaltic pumps to carry out the first stage coprecipitation reaction. The conditions for controlling the coprecipitation reaction were: temperature 55℃, pH 12.5, stirring speed 500 rpm, and free ammonia concentration 14.5 g / L. When the particle size of the precipitate reached 14 μm, the feeding was stopped, and material I was obtained.

[0107] (3) Transfer material I to reactor 2#, and feed the prepared solution B and mixed solution D into reactor 2# at a constant speed using metering pumps, with the feeding speed controlled at 400 mL / min. Control the reaction temperature at 70℃ and the stirring speed at 500 rpm. Stop feeding when the particle size of the precipitate reaches 15μm to obtain the precursor slurry.

[0108] (4) The precursor slurry is filtered, washed and dried to obtain the precursor material.

[0109] (5) The obtained precursor material and lithium hydroxide monohydrate were ball-milled and mixed at a molar ratio of 1:1.05, and then calcined at 500°C for 4 h in an oxygen atmosphere, followed by calcination at 900°C for 16 h to obtain the cathode material.

[0110] Comparative Example 2

[0111] The difference between Comparative Example 2 and Example 1 is that the precursor is a nickel-cobalt-manganese hydroxide. The specific process is as follows:

[0112] (1) Same as step (1) in Example 1.

[0113] (2) Under a nitrogen atmosphere, mixed salt solution A, sodium hydroxide solution C, and ammonia solution were pumped into reactor 1 using different peristaltic pumps to carry out the first stage coprecipitation reaction. The conditions for controlling the coprecipitation reaction were: temperature 55℃, pH 12.5, stirring speed 500 rpm, and free ammonia concentration 14.5 g / L. When the particle size of the precipitate reached 15 μm, the feeding was stopped, and the precursor slurry was obtained.

[0114] (3) The precursor slurry is filtered, washed and dried to obtain the precursor material.

[0115] (4) The obtained precursor material and lithium hydroxide monohydrate were ball-milled and mixed at a molar ratio of 1:1.05, and then calcined at 500°C for 4 h in an oxygen atmosphere, followed by calcination at 900°C for 16 h to obtain the cathode material.

[0116] Example 2

[0117] (1) Prepare a mixed salt solution A of nickel, cobalt, and manganese by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in water; wherein the total molar concentration of the three elements is 1 mol / L, and the molar ratio of nickel, cobalt, and manganese is 0.7:0.1:0.2. Prepare a sodium hydroxide solution C with a concentration of 6 mol / L. Prepare an ammonia solution with a concentration of 8 mol / L. Prepare a mixed solution B of metal nitrates and polyethylene glycol, wherein the molar ratio of lanthanum nitrate, aluminum nitrate, iron nitrate, chromium nitrate, magnesium nitrate, and zinc nitrate is 3:1:1:1:1:1, the total molar concentration of the metal elements lanthanum, aluminum, iron, chromium, magnesium, and zinc is 2 mol / L, and the concentration of polyethylene glycol is 25 g / L. Prepare a mixed solution D of NaOH and Na2CO3, wherein the molar ratio of sodium hydroxide to sodium carbonate is 1:1, and the total molar concentration is 5 mol / L.

[0118] (2) Under a nitrogen atmosphere, mixed salt solution A, sodium hydroxide solution C, and ammonia solution were pumped into reactor 1 using different peristaltic pumps to carry out the first stage coprecipitation reaction. The conditions for controlling the coprecipitation reaction were: temperature 50℃, pH 11.5, stirring speed 400 rpm, and free ammonia concentration 12 g / L. When the particle size of the precipitate reached 5 μm, the feeding was stopped, and material I was obtained.

[0119] (3) Transfer material I to reactor 2#, and feed the prepared solution B and mixed solution D into reactor 2# at a constant speed using metering pumps, with the feeding speed controlled at 600 mL / min. Control the reaction temperature at 80℃ and the stirring speed at 600 rpm. Stop feeding when the particle size of the precipitate reaches 6μm, and obtain material II.

[0120] (4) Transfer material II to reactor 1# and carry out the reaction as described in step (2) to obtain material III, the particle size of material III reaches 10μm.

[0121] (5) Transfer material III to reactor 2# and carry out the reaction as described in step (3) to obtain material IV, the particle size of material IV reaches 11μm.

[0122] (6) Transfer material IV to reactor 1# and carry out the reaction as described in step (2) to obtain material V, the particle size of material V reaches 15μm.

[0123] (7) Transfer material V to reactor 2# and carry out the reaction as described in step (3) to obtain precursor slurry with a particle size of 16μm.

[0124] (8) The precursor slurry is filtered, washed and dried to obtain a multi-layered precursor material.

[0125] (9) The obtained multilayer precursor material and lithium hydroxide monohydrate were ball-milled and mixed at a molar ratio of 1:1.05. Then, the mixture was calcined at 500°C for 4 h in an oxygen atmosphere, followed by calcination at 900°C for 16 h to obtain the cathode material.

[0126] Example 3

[0127] (1) Prepare a mixed salt solution A of nickel, cobalt, and manganese by dissolving nickel sulfate, cobalt sulfate, and manganese sulfate in water; wherein the total molar concentration of the three elements is 5 mol / L, and the molar ratio of nickel, cobalt, and manganese is 0.6:0.2:0.2. Prepare a sodium hydroxide solution C with a concentration of 8 mol / L. Prepare an ammonia solution with a concentration of 13 mol / L. Prepare a mixed solution B of metal nitrates and polyethylene glycol, wherein the molar ratio of lanthanum nitrate, aluminum nitrate, iron nitrate, chromium nitrate, magnesium nitrate, and zinc nitrate is 1:1:1:1:1:1, the total molar concentration of the metal elements lanthanum, aluminum, iron, chromium, magnesium, and zinc is 1 mol / L, and the concentration of polyethylene glycol is 30 g / L. Prepare a mixed solution D of NaOH and Na2CO3, wherein the molar ratio of sodium hydroxide to sodium carbonate is 1:1.5, and the total molar concentration is 1 mol / L.

[0128] (2) Under a nitrogen atmosphere, mixed salt solution A, sodium hydroxide solution C, and ammonia solution were pumped into reactor 1 using different peristaltic pumps to carry out the first stage coprecipitation reaction. The conditions for controlling the coprecipitation reaction were: temperature 60℃, pH 13.5, stirring speed 400 rpm, and free ammonia concentration 12 g / L. When the particle size of the precipitate reached 5 μm, the feeding was stopped, and material I was obtained.

[0129] (3) Transfer material I to reactor 2#, and feed the prepared solution B and mixed solution D into reactor 2# at a constant speed using metering pumps, with the feeding speed controlled at 500 mL / min. Control the reaction temperature at 60℃ and the stirring speed at 600 rpm. Stop feeding when the particle size of the precipitate reaches 5μm, and obtain material II.

[0130] (4) Transfer material II to reactor 3# and carry out the reaction as described in step (2) to obtain material III, the particle size of material III reaches 9μm.

[0131] (5) Transfer material III to reactor 4# and carry out the reaction as described in step (3) to obtain material IV, the particle size of material IV reaches 10μm.

[0132] (6) Transfer material IV to reactor 5# and carry out the reaction as described in step (2) to obtain material V, the particle size of material V reaches 14μm.

[0133] (7) Transfer material V to reactor 6# and carry out the reaction as described in step (3) to obtain precursor slurry with a particle size of 15μm.

[0134] (8) The precursor slurry is filtered, washed and dried to obtain a multi-layered precursor material.

[0135] (9) The obtained multilayer precursor material and lithium hydroxide monohydrate were ball-milled and mixed at a molar ratio of 1:1.05. Then, the mixture was calcined at 500°C for 4 h in an oxygen atmosphere, followed by calcination at 900°C for 16 h to obtain the cathode material.

[0136] The positive electrode materials obtained in Examples 1-3 and Comparative Examples 1-2 were assembled into batteries in the following manner: the positive electrode material, binder PVDF, and conductive agent were mixed in a ratio of 8:1:1, dry-milled for 10 min, and then NMP solvent was added. After homogenization, the mixture was stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was uniformly coated on aluminum foil. A lithium metal sheet was used as the negative electrode. A lithium-ion secondary electrolyte LB-037 (1M LiPF6 in DEC:EC:EMC=1:1:1 Vol%) was used as the electrolyte, and Celgard2325 was used as the separator to assemble a coin cell of LIR2032.

[0137] The electrical performance of the battery was tested as follows: In a 25°C constant temperature chamber, the battery was charged at a constant current rate of 0.1C to 4.3V, then charged at a constant voltage rate to 0.01C (cutoff), and then discharged at 0.1C to 3V. This cycle was repeated twice. After that, the battery was charged at a constant current rate of 0.5C to 4.3V, then charged at a constant voltage rate to 0.05C (cutoff), and then discharged at 0.5C to 3V. The charge and discharge capacity was recorded.

[0138] Table 1

[0139]

[0140] Table 1 shows the electrochemical performance of the assembled batteries. As can be seen from the table, the cathode material obtained by calcining the multilayer precursor provided by this invention exhibits higher initial discharge specific capacity and capacity retention after assembly into a battery. Comparing Example 1, Comparative Example 1, and Comparative Example 2, compared to the cathode materials obtained by calcining the bilayer and monolayer precursors, the cathode material obtained by calcining the multilayer precursor of this invention shows improved initial discharge specific capacity and capacity retention after assembly into a battery.

[0141] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A precursor of a lithium ion battery cathode material, characterized in that, The core of the precursor is a nickel-cobalt-manganese hydroxide, and the core is surrounded by a multilayer structure formed by alternating layers of lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide and nickel-cobalt-manganese hydroxide. The innermost and outermost layers of the multilayer structure are both lanthanum-aluminum-iron-chromium-magnesium-zinc hydroxide.

2. The precursor of the lithium ion battery cathode material according to claim 1, wherein, The core of the precursor has a D50 of 4~5μm; the thickness of each layer of the multilayer structure is 1~5μm.

3. The precursor of the lithium ion battery cathode material according to claim 1 or 2, characterized in that, The multi-layer structure has at least 3 layers.

4. The precursor of the lithium ion battery cathode material according to claim 3, wherein the precursor is characterized by, The multilayer structure has 5 layers, which, from the core to the outside, are lanthanum aluminum iron chromium magnesium zinc hydroxide, nickel cobalt manganese hydroxide, lanthanum aluminum iron chromium magnesium zinc hydroxide, nickel cobalt manganese hydroxide, and lanthanum aluminum iron chromium magnesium zinc hydroxide.

5. A method for preparing a precursor for a lithium-ion battery cathode material according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Prepare a mixed salt solution A of nickel, cobalt, and manganese; Prepare a soluble mixed salt solution B of lanthanum salt, aluminum salt, iron salt, chromium salt, magnesium salt, zinc salt and polyethylene glycol; Preparation of sodium hydroxide solution C; Prepare a mixed solution D of sodium hydroxide and sodium carbonate; Preparation of complexing agent solution; (2) Mixed salt solution A, sodium hydroxide solution C and complexing agent solution are introduced into reactor I in parallel to carry out a co-precipitation reaction to obtain material I; (3) Add material I to reaction vessel II, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material II; (4) Add material II to reaction vessel III, and flow in mixed salt solution A, sodium hydroxide solution C and complexing agent solution to carry out co-precipitation reaction to obtain material III; (5) Add material III to reaction vessel IV, and flow in mixed salt solution B and mixed solution D to carry out co-precipitation reaction to obtain material IV; Similarly, multilayer precursors can be prepared through a co-precipitation process.

6. The preparation method according to claim 5, characterized in that, The nickel salt, cobalt salt, and manganese salt used to prepare mixed salt solution A are at least one of sulfate, nitrate, and chloride salts, respectively. The total concentration of nickel, cobalt, and manganese metal ions in the mixed salt solution A is 1-5 mol / L; The complexing agent is ammonia water; The concentration of the complexing agent solution is 8-13 mol / L.

7. The preparation method according to claim 5, characterized in that, The lanthanum salt, aluminum salt, iron salt, chromium salt, magnesium salt, and zinc salt mentioned are all nitrates; The molar ratio of lanthanum, aluminum, iron, chromium, magnesium, and zinc in the mixed salt solution B is 1-5:1:1:1:1:1; The total concentration of lanthanum, aluminum, iron, chromium, magnesium and zinc metal ions in the mixed salt solution B is 1-3 mol / L; The concentration of polyethylene glycol in the mixed salt solution B is 20-30 g / L; The molar ratio of sodium hydroxide to sodium carbonate in the mixed solution D is 1:1-2; The total molar concentration of sodium hydroxide and sodium carbonate in the mixed solution D is 1-5 mol / L.

8. The preparation method according to any one of claims 5-7, characterized in that, The temperature of the coprecipitation reaction described in steps (2), (4) and the corresponding analogous steps is 50-60℃, the reaction atmosphere is nitrogen atmosphere or inert gas atmosphere, and the pH value of the reaction system is 11.5-13.

5.

9. The preparation method according to any one of claims 5-7, characterized in that, The temperature of the coprecipitation reaction described in steps (3), (5) and the corresponding analogous steps is 60-80℃, and the reaction atmosphere is a nitrogen atmosphere or an inert gas atmosphere.

10. The preparation method according to any one of claims 5-7, characterized in that, Steps (2), (4), and the corresponding analogous steps are carried out in the same reactor; Steps (3), (5), and the corresponding analogous steps are carried out in the same reactor.

11. A lithium-ion battery cathode material, characterized in that, The cathode material is obtained by sintering a precursor prepared by any one of claims 1-4 or by any one of claims 5-10 after mixing lithium with the precursor.

12. A lithium-ion battery, characterized in that, Includes the cathode material as described in claim 11.

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