CN114420911A - Low-residual-lithium high-nickel cathode material with double-shell structure, preparation method thereof and lithium ion battery - Google Patents

Low-residual-lithium high-nickel cathode material with double-shell structure, preparation method thereof and lithium ion battery Download PDF

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CN114420911A
CN114420911A CN202210074746.1A CN202210074746A CN114420911A CN 114420911 A CN114420911 A CN 114420911A CN 202210074746 A CN202210074746 A CN 202210074746A CN 114420911 A CN114420911 A CN 114420911A
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nickel
low
lithium
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CN114420911B (en
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王慧萍
李崇
张彩虹
方向乾
曹壮
乔水伶
吕明
高峰
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Shaanxi Rainbow New Materials Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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Abstract

The invention discloses a low-residual lithium high-nickel cathode material with a double-shell structure, a preparation method thereof and a lithium ion battery, wherein the preparation method comprises the following steps: mixing NiaCobMnc(OH)2Mixing lithium hydroxide and a doping agent, washing after sintering to form slurry, mixing the slurry with nickel-cobalt-manganese mixed salt with low nickel proportion and ammonia water to carry out surface coprecipitation coating reaction, and mixing and sintering a product after the reaction, LiCl and metal chloride with fused salt sintering performance to prepare the low-residual-lithium high-nickel cathode material with a double-shell structure. The internal core of the cathode material is Li (Ni)aCobMnc)1‑ sAsO2，a≥0.8，0B is not less than 0.15, a + b + c is 1, s is more than 0 and not more than 0.05; the inner shell is LiNixCoyMnzO2X is more than or equal to 0 and less than or equal to 0.7, y is more than or equal to 0.1 and less than or equal to 1.0, and x + y + z is equal to 1; the outer shell is LimMnCl6M is more than 0 and less than or equal to 3, M + gamma n is 6, and gamma is the valence of M metal. The nickel content of the inner shell is low, and the problems of high residual lithium on the surface of the high-nickel material, easiness in water absorption and unstable structure are solved. LimMnCl6The material is a lithium ion fast conductor substance, is beneficial to the migration and transmission of lithium ions and electrons, and improves the rate capability of the material.

Description

Low-residual-lithium high-nickel cathode material with double-shell structure, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion battery anode materials, and relates to a low-residual-lithium high-nickel anode material with a double-shell structure, a preparation method of the anode material and a lithium ion battery.
Background
The new energy automobile industry is in a rapid development stage, and meanwhile, with the continuous improvement of the mileage requirement of the new energy automobile, the high-nickel anode material with the energy density superimposed with the comprehensive cost advantage becomes the future trend.
In the high nickel composite multi-element anode material system, Ni is added along with the increase of nickel content3+Is increased stepwise, but Ni3 +The stability of the ions in the air is poor, and the ions are easy to be reduced into Ni2+And associated with the occurrence of a lithium precipitation phenomenon, LiOH and Li are formed on the surface layer of the particles2CO3An alkaline substance. In addition, in the preparation of the ternary material, in consideration of lithium volatilization under high temperature conditions, an excessive lithium source is usually introduced, so that redundant lithium salt is remained on the surface of final material particles, particularly in the process of manufacturing the high-nickel ternary cathode material, the volatilization amount of the lithium salt is low due to low sintering temperature, the content of the redundant lithium salt on the surface of the material is further increased, and the problem of high residual alkali on the surface of the high-nickel material is aggravated。
Excessive residual alkali or residual lithium on the surface of the high-nickel material particles can bring many hazards in the battery application process, and 1) the excessive residual lithium can cause higher pH value, so that the gelation of slurry can be caused in the preparation process of the battery cell pole piece, and the coating of the slurry is not uniform. 2) Too high residual lithium on the surface of the material has poor conductivity and blocks Li+De-intercalation, resulting in greater polarization. 3) LiOH on the surface of the material reacts with electrolyte to generate HF and Li2CO3Can cause serious flatulence during high-temperature storage of the battery and influence the safety performance of the battery.
For high nickel positive electrode materials, including lithium nickel cobalt manganese oxide (NMC), lithium Nickel Cobalt Aluminate (NCA) and high nickel cobalt free surface residual lithium problems are of critical importance, although it is not possible to have absolutely no residue, but it is necessary to keep its content as low as possible or to control it within a stable and reasonable range (typically below 1000 ppm). At present, researches on how to solve the problem of residual lithium on the surface of the high-nickel material are relatively few. The existing research mainly focuses on removing residual lithium by a process of water washing and secondary sintering, but the water washing can damage lithium in a ternary material structure to a certain extent, and the multiplying power and the cycle performance of the material are obviously reduced. Secondly, the surface coating modification is also an effective method for reducing the residual lithium amount on the surface of the ternary material, but the existing coating process has more routes, the residual alkali reducing effect is uneven and has larger difference, and the improvement is still needed.
The residual alkali content of the current commercial high-nickel product is still high, the residual lithium content is between 1500ppm and 2000ppm, and the requirement on the battery manufacturing environment still needs harsh conditions. Therefore, researchers are still required to continuously explore more effective methods for further reducing the problem of alkali residue on the surface of the nickel-rich material.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a low-residual lithium high-nickel cathode material with a double-shell structure, a preparation method thereof and a lithium ion battery, so that the purposes of stabilizing the surface structure of the high-nickel cathode and reducing the residual lithium on the surface are achieved, and the rate capability, the cycle performance and the safety performance of the high-nickel cathode material are improved.
The invention is realized by the following technical scheme:
a preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
s1: mixing NiaCobMnc(OH)2Uniformly stirring the lithium hydroxide and the doping agent, and sintering in pure oxygen to obtain a high nickel matrix material;
the dopant is any one, two or three of nano metal oxides of Zr, Sr, Nb, Y, Al, Mg and Ti;
s2: stirring pure water and the high nickel substrate material uniformly, washing with water to obtain mixed slurry, adding a nickel-cobalt-manganese mixed salt solution and an ammonia water solution into the obtained mixed solution, adjusting the pH value to be alkaline, reacting, and aging, dehydrating and drying the reaction solution to obtain the low nickel hydroxide coated high nickel substrate material;
s3: uniformly stirring and mixing the low-nickel hydroxide coated high-nickel matrix material, LiCl and metal chloride with fused salt sintering performance, and sintering in an air atmosphere to obtain a low-residual lithium high-nickel cathode material with a double-shell structure;
the metal chloride with the fused salt sintering performance is InCl3、ZrCl4、YCl3、AlCl3、BiCl3、GaCl3、ScCl3And LaCl3Or a mixture of any two of them.
Preferably, the nickel-cobalt-manganese mixed salt solution in step S2 is a mixed solution of water-soluble nickel salt, water-soluble cobalt salt and water-soluble manganese salt; the water-soluble nickel salt is nickel sulfate, nickel nitrate, nickel acetate or nickel chloride, the water-soluble cobalt salt is cobalt sulfate, cobalt nitrate, cobalt chloride or cobalt acetate, and the water-soluble manganese salt is manganese sulfate, manganese nitrate, manganese chloride or manganese acetate.
Preferably, in the step S2, the pH value is adjusted to 11.0-13.0, the reaction time is 10-150 min, the reaction temperature is 50-90 ℃, the reaction solution is subjected to filter pressing dehydration after the reaction, and vacuum drying is carried out at 80-150 ℃, so as to prepare the low-nickel hydroxide coated high-nickel matrix material.
Preferably, in step S3, the ratio of the molar amount of LiCl added to the sum of the molar amounts of the low-nickel hydroxide on the surface of the low-nickel hydroxide coated high-nickel matrix material prepared in step S2 and the metallic chloride having molten salt sintering property added in step S3 is (1.0-1.2): 1.
Preferably, in the step S3, the stirring speed is 150-700 rpm, and the stirring time is 5-60 min.
Preferably, the sintering temperature in the step S1 is 600 to 900 ℃, the sintering temperature in the step S3 is 200 to 800 ℃, and the sintering temperature in the step S1 is higher than the sintering temperature in the step S3.
According to the double-shell structure low-residual-lithium high-nickel cathode material prepared by the method, the cathode material is of a core-shell structure, and the chemical expression of an internal core of the core-shell structure is as follows: li (Ni)aCobMnc)1-sAsO2Wherein a is more than or equal to 0.8, b is more than or equal to 0 and less than or equal to 0.15, a + b + c is 1, and s is more than 0 and less than or equal to 0.05; the molar ratio of Ni in the inner core is not less than 0.8;
the A is any one, two or three of Zr, Sr, Nb, Y, Al, Mg and Ti;
the shell is of a double-shell structure, and the double-shell structure comprises an inner shell and an outer shell;
the chemical expression of the inner shell is LiNixCoyMnzO2Wherein x is more than or equal to 0 and less than or equal to 0.7, y is more than or equal to 0.1 and less than or equal to 1.0, and x + y + z is equal to 1;
the chemical expression of the outer shell is LimMnCl6Wherein M is more than 0 and less than or equal to 3, M + gamma n is 6, and gamma is the valence of M metal;
and M is one or two of In, Zr, Y, Al, Bi, Ga, Sc and La.
Preferably, the coating amount of the inner shell is 0.01-5% of the mass of the inner core; the coating amount of the outer shell is 0.01-0.5% of the mass of the inner core; the residual lithium amount on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is not more than 1000 ppm.
A lithium ion battery adopts the low-residual lithium high-nickel anode material with the double-shell structure as the anode of the lithium ion battery.
Compared with the prior art, the invention has the following beneficial technical effects:
a preparation method of a double-shell structure high-nickel positive electrode material with low residual lithium comprises the steps of firstly synthesizing a high-nickel base material, then synthesizing a low-nickel hydroxide coating layer on the surface of the high-nickel base material, coating LiCl and a metal chloride with fused salt sintering performance on the high-nickel base material coated with the low-nickel hydroxide to form conversion from high nickel to low nickel material, and sintering to obtain the double-shell structure high-nickel positive electrode material with low residual lithium, so that the low-nickel ternary material can effectively react, the residual lithium on the surface of the high-nickel material is reduced, and the preparation method is reasonable in design, easy to operate, low in manufacturing cost and low in equipment requirement.
Furthermore, the pH value is 11.0-13.0, which is beneficial to coprecipitation reaction to form a low-nickel hydroxide coating layer.
Furthermore, the vacuum drying is adopted, so that the drying efficiency is improved, and the high-temperature oxidation and other side reactions are prevented from occurring to influence the product capacity.
Further, in the step S3, the stirring speed is 150 to 700rpm, and the stirring time is 5 to 60min, so that the reactants can be fully and uniformly mixed.
Further, the sintering temperature in step S1 is higher than that in step S3, and the crystal form and electrical properties of the matrix material are affected by too high a temperature in step S3.
The invention also discloses a low-residual lithium high-nickel cathode material with a double-shell structure, wherein the cathode material has a double-shell structure, and the internal nuclear chemical expression is Li (Ni)aCobMnc)1-sAsO2Wherein, the molar ratio of Ni in the inner core is not less than 0.8, the content of nickel is higher, and the high energy density of the anode material is effectively ensured. The double-shell structure comprises an inner shell and an outer shell, wherein the chemical expression of the inner shell is LiNixCoyMnzO2The nickel content is low, the conversion from the high nickel material to the low nickel material is formed, and the problems of high residual lithium on the surface of the high nickel material, easy water absorption and the like are effectively solvedThe surface structure is unstable, which is beneficial to the exertion of the cycle performance. The chemical expression of the outer shell is LimMnCl6，LimMnCl6The material is a lithium ion fast conductor substance, is beneficial to improving the de-intercalation speed of lithium ions and the migration and transmission of electrons, and effectively improves the rate capability of the material.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic flow chart of a method for preparing a positive electrode material according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. are used for indicating the orientation or positional relationship based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship which is usually arranged when the product of the present invention is used, the description is merely for convenience and simplicity, and the indication or suggestion that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, cannot be understood as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.
Furthermore, the term "horizontal", if present, does not mean that the component is required to be absolutely horizontal, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the embodiments of the present invention, it should be further noted that unless otherwise explicitly stated or limited, the terms "disposed," "mounted," "connected," and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The invention is described in further detail below with reference to the accompanying drawings:
as shown in fig. 1, the preparation method of the low residual lithium high nickel cathode material with a double-shell structure of the invention specifically comprises the following steps:
s1: preparation of high nickel base material
High nickel precursor NiaCobMnc(OH)2Lithium hydroxide and doping agent are evenly stirred and sintered in pure oxygen, and then the product is cooled, crushed and sieved to break up the internal nuclear matrix material, thereby facilitating the subsequent processAnd (5) uniformly wrapping. And preparing an internal core matrix material of the cathode material, namely a high nickel matrix material.
The dopant is any one, two or three of nanometer metal oxides of Zr, Sr, Nb, Y, Al, Mg and Ti.
S2: co-precipitation coating
Adding pure water into a reaction kettle, starting stirring, adding the high nickel substrate material into the pure water, stirring and washing to obtain mixed slurry, gradually adding a nickel-cobalt-manganese mixed salt solution and an ammonia water solution into the mixed solution to perform in-situ coprecipitation reaction, adjusting the pH value of a reaction system to 11.0-13.0 in the reaction, and after the reaction, aging, dehydrating and drying the reaction solution to obtain the low-nickel hydroxide coated high nickel substrate material; the reaction time of the coprecipitation reaction is 10-150 min, the reaction temperature is 50-90 ℃, the pH value can be adjusted by dripping a small amount of NaOH solution, and the temperature is automatically adjusted by a reaction kettle temperature control system. And after the coprecipitation reaction is finished, aging, filter-pressing and dehydrating the mixed slurry, and performing vacuum drying at 80-150 ℃ to obtain the low-nickel hydroxide coated high-nickel matrix material.
Wherein the mass ratio of the pure water to the high-nickel matrix material is (0.5-1.5): 1;
wherein the nickel-cobalt-manganese mixed salt solution is a mixed solution of water-soluble nickel salt, water-soluble cobalt salt and water-soluble manganese salt; the water-soluble nickel salt is any one of nickel sulfate, nickel nitrate, nickel acetate or nickel chloride, the water-soluble cobalt salt is any one of cobalt sulfate, cobalt nitrate, cobalt chloride or cobalt acetate, and the water-soluble manganese salt is any one of manganese sulfate, manganese nitrate, manganese chloride or manganese acetate.
S3: dry coating
Adding a high nickel matrix material coated with low nickel hydroxide, LiCl and a metal chloride with molten salt sintering performance into a high-speed mixer, and mechanically mixing uniformly, wherein the stirring speed of the high-speed mixer is 150-700 rpm, and the stirring time is 5-60 min. Sintering for 2-20 h in air atmosphere, and screening and deironing to obtain the cathode material, wherein impurities caused by sintering and magnetic impurities generated in the production process can be effectively removed in the screening and deironing processes. The adding sequence of the low-nickel hydroxide coated high nickel base material, the LiCl and the metal chloride with the fused salt sintering performance is that the first weight of the low-nickel hydroxide coated high nickel base material, the LiCl and the metal chloride with the fused salt sintering performance are stirred and mixed, and then the rest weight of the low-nickel hydroxide coated high nickel base material prepared in the step S2 is added, wherein the weight ratio of the first weight of the low-nickel hydroxide coated high nickel base material to the rest weight of the low-nickel hydroxide coated high nickel base material is 1:1, so that the improvement of the mixing efficiency is facilitated, and the mixing among substances is more uniform.
The metal chloride with the fused salt sintering performance is InCl2、ZrCl4、YCl4、AlCl3、BiCl2、GaCl3、ScCl3And LaCl3Or a mixture of any two of them.
The addition of LiCl in a molar amount allows the low nickel hydroxide on the surface of the low nickel hydroxide-coated high nickel base material prepared in step S2 and the metal chloride having a molten salt sintering property added in step S3 to completely react. Preferably, according to the stoichiometric ratio of the chemical reaction, the ratio of the molar quantity of the added LiCl to the sum of the molar quantity of the low-nickel hydroxide on the surface of the low-nickel hydroxide coated high-nickel base material prepared in the step S2 and the molar quantity of the metal chloride with the molten salt sintering performance added in the step S3 is (1.0-1.2): 1, and the LiCl and the metal chloride with the molten salt sintering performance have nano or submicron grade.
The sintering temperature in the step S1 is 600-900 ℃, the sintering temperature in the step S3 is 200-800 ℃, and the sintering temperature in the step S1 is higher than the sintering temperature in the step S3.
The anode material prepared by the method is of a core-shell structure, and the chemical expression of the core matrix material in the core-shell structure is as follows: li (Ni)aCobMnc)1-sAsO2Wherein a is more than or equal to 0.8, b is more than or equal to 0 and less than or equal to 0.15, a + b + c is 1, and s is more than 0 and less than or equal to 0.05; the internal core matrix material comprises a high-nickel ternary material and a cobalt-free high-nickel material, and the morphology of the internal core matrix material comprises single crystal and polycrystal, wherein the molar ratio of Ni is not lessAt 0.8; in the formula, A is any one, two or three of Zr, Sr, Nb, Y, Al, Mg and Ti;
the shell of the anode material is of a double-shell structure, and the double-shell structure comprises an inner-layer shell and an outer-layer shell; the chemical expression of the inner shell is LiNixCoyMnzO2Wherein x is more than or equal to 0 and less than or equal to 0.7, y is more than or equal to 0.2 and less than or equal to 1.0, and x + y + z is equal to 1; the outer shell is Li in chemical expressionmMnCl6Wherein M is more than 0 and less than or equal to 3, M + gamma n is 6, gamma is the valence of M metal, and M is one or two of In, Zr, Y, Al, Bi, Ga, Sc and La. Wherein the coating amount of the inner shell is 0.01-5% of the mass of the inner core matrix material, and the coating amount of the outer shell is 0.01-0.5% of the mass of the inner core matrix material; the residual lithium amount on the surface of the cathode material is not more than 1000 ppm.
The invention also provides a lithium ion battery, and the low-residual lithium high-nickel cathode material with the double-shell structure is used as the cathode of the lithium ion battery.
Compared with the prior art, the method firstly synthesizes the high nickel matrix material, and then forms the low nickel precursor coating layer on the surface of the high nickel matrix material in an in-situ coprecipitation mode, namely the high nickel matrix material coated by the low nickel hydroxide. Then the dry coating process is carried out, and a molten salt cooling sintering method is matched to form a coating layer with a double-shell structure, wherein the inner shell layer is a low-nickel layer, and the outer shell layer forms LimMnCl6The lithium ion fast conductor material of (1). Through double-shell coating, the problems of unstable surface structure of materials such as high residual lithium on the surface of a high-nickel material, easy water absorption and the like are effectively solved; the coprecipitation coating of the low-nickel compound is realized in the high-nickel washing process, the conversion from high-nickel to low-nickel materials is formed, and the content of residual lithium on the surface of the high-nickel material is effectively reduced; meanwhile, by adopting LiCl and metal chloride with fused salt sintering performance to coat and match with a fused salt sintering method, the effective reaction of the low-nickel ternary material is realized, the residual lithium on the surface of the high-nickel material is reduced, and Li can be formedmMnCl6The lithium ion fast conductor material improves the lithium ion de-intercalation speed and the multiplying power performance of the material. The invention has the advantages of relatively simple preparation process, low manufacturing cost and low equipment requirement,has good application prospect.
The invention is further illustrated by the following specific examples:
example 1
A preparation method of a double-shell structure low-residual-lithium high-nickel cathode material comprises the following steps:
(1) preparation of high nickel base material
1000g of high nickel precursor Ni0.83Co0.12Mn0.05(OH)2430g of lithium hydroxide and 2.5g of ZrO are uniformly mixed at a high speed, and are subjected to pure oxygen sintering at the temperature of 800 ℃, and then are cooled, crushed and sieved by a 400-mesh sieve to obtain the high-nickel matrix material.
(2) Low nickel co-precipitation coating
Preparing: nitrate of three elements of nickel, cobalt and manganese are respectively prepared into a nickel, cobalt and manganese nitrate solution with the concentration of 2mol/L according to the molar ratio of nickel ions to cobalt ions to manganese ions of 5:2:3, and ammonia water with the mass concentration of 15 wt% and NaOH solution with the molar concentration of 0.5mol/L are prepared.
Adding 400ml of pure water into a reaction kettle, starting stirring, adding 500g of high nickel matrix material into the pure water, washing for 10min, controlling the temperature of the reaction kettle to be 60 ℃, and gradually adding 100ml of nickel-cobalt-manganese nitrate solution and ammonia water into the reaction kettle by a peristaltic pump according to 10ml/min to perform in-situ coprecipitation reaction; dropwise adding NaOH solution to adjust the pH value to be 11.0-12.0, after the coprecipitation reaction is finished, aging, filter-pressing and dehydrating the slurry, and drying at the temperature of 120 ℃ in vacuum to obtain a low-nickel hydroxide coated high-nickel substrate material;
(3) dry coating and fused salt sintering
High nickel matrix material coated with low nickel hydroxide, LiCl and InCl3Adding the materials into a mixer according to the proportion of 100:1.15:0.4 for mechanical mixing, sintering the obtained mixed material in an air atmosphere furnace at the temperature of 700 ℃ for 8 hours, crushing, sieving and removing iron to obtain the low-residual lithium high-nickel cathode material with the double-shell structure, wherein the chemical formula of the inner core of the cathode material is Li (Ni)0.83Co0.12Mn0.05)0.98Zr0.02O2Nickel of which containsThe content is high, and the chemical formula of the inner shell layer is LiNi0.5Co0.3Mn0.2O2The chemical formula of the shell layer is Li3InCl6The amount of residual lithium on the surface of the material was 750ppm as measured by acid-base titration.
Example 2
A preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
(1) preparation of high nickel base material
1000g of high nickel precursor Ni0.91Co0.08Mn0.01(OH)2430g of lithium hydroxide and 2.5g of ZrO are uniformly mixed at a high speed, and are subjected to pure oxygen sintering at the temperature of 730 ℃, and then are cooled, crushed and sieved by a 400-mesh sieve, so that the high-nickel matrix material is obtained.
(2) Low nickel co-precipitation coating
Preparing: respectively preparing sulfate of three elements of nickel, cobalt and manganese into a nickel, cobalt and manganese sulfate solution with the concentration of 2mol/L according to the molar ratio of nickel ions, cobalt ions and manganese ions of 6:2:2, and preparing ammonia water with the mass concentration of 15 wt% and NaOH solution with the molar concentration of 0.5 mol/L. And preparing ammonia water with the mass concentration of 15 wt% and NaOH solution with the molar concentration of 0.5 mol/L.
Adding 400ml of pure water into a reaction kettle, starting stirring, adding 500g of high nickel matrix material into the pure water, washing for 10min, controlling the temperature of the reaction kettle to be 60 ℃, and gradually adding 100ml of nickel-cobalt-manganese sulfate solution and ammonia water into the reaction kettle by a peristaltic pump according to 10ml/min to perform in-situ coprecipitation reaction; and dropwise adding NaOH solution to adjust the pH value to be 11.0-12.0, after the coprecipitation reaction is finished, aging, filter-pressing and dehydrating the slurry, and drying at the temperature of 120 ℃ in vacuum to obtain the low-nickel hydroxide coated high-nickel matrix material.
(3) Dry coating and fused salt sintering
High nickel matrix material coated with low nickel hydroxide, LiCl and InCl3And BiCl3Adding into a mixer, and mechanically mixing, wherein the low-nickel hydroxide-coated high-nickel matrix material, LiCl, and InCl3And BiCl3The mass ratio of 100:1.15:0.3:0.1 to obtainSintering the obtained mixed material in an air atmosphere furnace at 600 ℃ for 10h, crushing, sieving and removing iron to obtain the low-residual-lithium high-nickel cathode material with a double-shell structure, wherein the chemical formula of the core in the cathode material is Li (Ni)0.91Co0.08Mn0.01)0.98Zr0.02O2Its nickel content is higher, and the chemical formula of inner shell layer is LiNi0.6Co0.2Mn0.2O2The chemical formula of the shell layer is Li3In0.9Bi0.1Cl6The amount of residual lithium on the surface of the material was 990ppm by acid-base titration.
Comparative example 1
Conventional LiNi0.83Co0.12Mn0.05O2The material and the preparation method thereof comprise the following steps:
the precursor Ni0.83Co0.12Mn0.05(OH)2Lithium hydroxide and ZrO2Mixing according to the molar ratio of 1:1.05:0.002, sintering for 12 hours at 800 ℃ in an oxygen atmosphere, crushing, and sieving by a 300-mesh sieve to finally obtain the high-nickel 83 matrix.
The crushed 83 base material is washed by water according to the mass ratio of 1:1, vacuumized at 120 ℃, coated with 1500ppm of alumina by a dry method and added into a high-speed mixer for mixing, sintered for 8 hours in an air atmosphere furnace at 700 ℃, and sieved to prepare a comparative sample 1.
Comparative example 2
Conventional LiNi0.91Co0.08Mn0.01O2The material and the preparation method thereof comprise the following steps:
the precursor Ni0.91Co0.08Mn0.01(OH)2Lithium hydroxide and ZrO2Mixing according to the molar ratio of 1:1.05:0.002, sintering for 12 hours at 730 ℃ in an oxygen atmosphere, crushing, and sieving by a 300-mesh sieve to finally obtain the high-nickel 91 matrix.
And (3) washing the ground 91 ternary matrix material with water according to the mass ratio of 1:1, performing vacuum treatment at 120 ℃, calculating the weight of the dry-coated 1500ppm alumina and the matrix material, adding the mixture into a high-speed mixer for mixing, sintering in an air atmosphere furnace at the temperature of 600 ℃ for 8 hours, and performing sieving treatment to obtain a comparative sample 2.
And (3) testing the material performance:
the residual lithium and charging (3.0-4.3V) characteristics of the double-shell structure high-nickel cathode material prepared in examples 1 and 2 and the ternary cathode material prepared in comparative examples 1 and 2 were tested, and the test results are shown in table 1:
TABLE 1 comparison of residual alkali and strain performance data for examples 1 and 2 and comparative examples 1 and 2
Figure BDA0003483415020000111
The experimental data in table 1 show that, compared with the comparative example, the residual alkali of the positive electrode material prepared by the invention is obviously reduced, the cycle retention rate is high, the influence on the capacity is less than 1mAh, and the rate capability is obviously improved.
Example 3
A preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
s1: preparation of high nickel base material
High nickel precursor Ni0.88Co0.11Mn0.04(OH)2Lithium hydroxide and nano SrO particles are uniformly stirred and mixed, and are sintered in pure oxygen at the sintering temperature of 730 ℃, and then the product is cooled, crushed and sieved to prepare the internal core matrix material of the anode material, namely the high nickel matrix material.
S2: co-precipitation coating
Adding pure water into a reaction kettle, starting stirring, adding the high nickel matrix material into the pure water, and uniformly stirring. Wherein the mass ratio of the pure water to the high-nickel matrix material is 0.5: 1. Gradually adding a mixed solution of nickel chloride, cobalt chloride and manganese chloride and an ammonia water solution in a molar ratio of 6:1:3 into the mixed solution to perform in-situ coprecipitation reaction, adjusting the pH value of a reaction system to 11.0-12.0 by adopting a NaOH solution in the reaction, reacting for 10min at 50 ℃, aging, filter-pressing and dehydrating the reaction solution after the reaction, and performing vacuum drying at 80 ℃ to obtain the low-nickel hydroxide coated high-nickel matrix material.
S3: dry coating and fused salt sintering
Half the weight of the low nickel hydroxide coated high nickel matrix material prepared in step S2, nano LiCl particles, nano InCl3Particles and nano ZrCl4The particles are added into a high-speed mixer to be mechanically mixed evenly, and then the rest half weight of the high nickel matrix material coated by the low nickel hydroxide is added, wherein the stirring speed of the high-speed mixer is 150rpm, and the stirring time is 5 min. Sintering for 6 hours in air atmosphere at the sintering temperature of 600 ℃, and sieving and deironing to obtain the low-residual lithium high-nickel cathode material with the double-shell structure;
the LiCl is added according to the stoichiometric ratio in the molar amount of the low nickel hydroxide on the surface of the low nickel hydroxide coated high nickel matrix material prepared in the step S2 and the InCl added in the step S32The ratio of the sum of the molar amounts is 1:1, and LiCl, InCl3And ZrCl4The particles are all nano-sized.
The positive electrode material prepared by the method is of a core-shell structure, and the chemical expression of the core-shell structure internal core high nickel matrix material is as follows: li (Ni)0.88Co0.11Mn0.04)0.99Sr0.01O2The internal core matrix material comprises a high-nickel ternary material and a cobalt-free high-nickel material, and the morphology of the internal core matrix material comprises single crystal and polycrystal.
The shell of the anode material is of a double-shell structure, and the double-shell structure comprises an inner-layer shell and an outer-layer shell; the chemical expression of the inner shell is LiNi0.6Co0.1Mn0.3O2(ii) a The outer shell is Li in chemical expression0.28(In0.8Zr0.2)Cl6. Wherein, the coating amount of the inner shell is 0.01 percent of the mass of the inner core matrix material, and the coating amount of the outer shell is 0.01 percent of the mass of the inner core matrix material; the residual lithium content on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is 924 ppm.
Example 4
A preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
s1: preparation of high nickel base material
High nickel precursor Ni0.8Co0.1Mn0.1(OH)2Lithium hydroxide and nano NbO particles are uniformly stirred and mixed, and are sintered in pure oxygen at the sintering temperature of 800 ℃, and then the product is cooled, crushed and sieved to prepare the internal core matrix material of the anode material, namely the high nickel matrix material.
S2: co-precipitation coating
Adding pure water into a reaction kettle, starting stirring, adding the high nickel matrix material into the pure water, and uniformly stirring to obtain mixed slurry. Wherein the mass ratio of the pure water to the high nickel matrix material is 0.7: 1. Gradually adding a mixed solution of nickel chloride, cobalt chloride and manganese chloride and an ammonia water solution in a molar ratio of 5:1:4 into the mixed solution to perform in-situ coprecipitation reaction, adjusting the pH value of a reaction system to 11.0-12.0 by adopting a NaOH solution in the reaction, reacting for 30min at 70 ℃, after the reaction, aging, filter-pressing and dehydrating the reaction solution, and performing vacuum drying at 100 ℃ to obtain the low-nickel hydroxide coated high-nickel matrix material.
S3: dry coating and fused salt sintering
Half the weight of the low nickel hydroxide-coated high nickel matrix material, nano-sized LiCl particles, and nano-sized YCl prepared in step S23The particles are added into a high-speed mixer to be mechanically mixed evenly, and then the rest half weight of the high nickel matrix material coated by the low nickel hydroxide is added, wherein the stirring speed of the high-speed mixer is 200rpm, and the stirring time is 10 min. Sintering the mixture for 5 hours in air atmosphere at the sintering temperature of 570 ℃, and obtaining the anode material through screening and iron removal processes;
the molar amount of LiCl added is in stoichiometric ratio with the low nickel hydroxide coated high nickel matrix material obtained in step S2 and YCl added in step S33The sum of the molar amounts being 1.1:1, and LiCl and YCl3The particles are all nano-sized.
The cathode material prepared by the method is of a core-shell structure, and the chemical expression of the core matrix material in the core-shell structure is Li (Ni)0.80Co0.10Mn0.1)0.97Nb0.03O2The internal core matrix material comprises a high-nickel ternary material and a cobalt-free high-nickel material, and the morphology of the internal core matrix material comprises single crystal and polycrystal.
The shell of the anode material is of a double-shell structure, and the double-shell structure comprises an inner-layer shell and an outer-layer shell; the chemical expression of the inner shell is LiNi0.5Co0.1Mn0.4O2(ii) a (ii) a The outer shell is Li in chemical expression3YCl6. Wherein, the coating amount of the inner shell is 0.05 percent of the mass of the inner core matrix material, and the coating amount of the outer shell is 0.02 percent of the mass of the inner core matrix material; the residual lithium content on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is 796 ppm.
Example 5
A preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
s1: preparation of high nickel base material
High nickel precursor Ni0.91Co0.08Mn0.01(OH)2Lithium hydroxide, nano-Y2O3And uniformly stirring and mixing the particles, sintering the particles in pure oxygen at 780 ℃, and then cooling, crushing and sieving the product to obtain the internal core matrix material of the cathode material, namely the high-nickel matrix material.
S2: co-precipitation coating
Adding pure water into a reaction kettle, starting stirring, adding the high nickel matrix material into the pure water, and uniformly stirring. Wherein the mass ratio of the pure water to the high-nickel matrix material is 1:1. Adding a mixed solution of nickel acetate, cobalt acetate and manganese acetate and an ammonia water solution in a molar ratio of 5:2:3 into the mixed solution step by step to perform in-situ coprecipitation reaction, adjusting the pH value of a reaction system to 11.0-12.0 by adopting a NaOH solution in the reaction, reacting for 50min at the reaction temperature of 60 ℃, aging, filter-pressing and dehydrating the reaction solution after the reaction, and performing vacuum drying at 140 ℃ to obtain the low-nickel hydroxide coated high-nickel matrix material.
S3: dry coating and fused salt sintering
A high nickel base coated with the low nickel hydroxide obtained in step S2Bulk material, nano LiCl particles and nano YCl3The particles are added into a high-speed mixer for mechanical mixing uniformly, the stirring speed of the high-speed mixer is 500rpm, and the stirring time is 30 min. Sintering the mixture for 10 hours in air atmosphere at the sintering temperature of 450 ℃, and obtaining the anode material through screening and iron removal processes;
the molar amount of LiCl added is in stoichiometric ratio with the low nickel hydroxide coated high nickel matrix material obtained in step S2 and YCl added in step S33The sum of the molar amounts being 1.2:1, LiCl and YCl3Are all nano-scale.
The cathode material prepared by the method is of a core-shell structure, and the chemical expression of the core matrix material in the core-shell structure is Li (Ni)0.91Co0.08Mn0.01)0.97Y0.03O2The internal core matrix material comprises a high-nickel ternary material and a cobalt-free high-nickel material, and the morphology of the internal core matrix material comprises single crystal and polycrystal.
The shell of the anode material is of a double-shell structure, and the double-shell structure comprises an inner-layer shell and an outer-layer shell; the chemical expression of the inner shell is LiNi0.5Co0.2Mn0.3O2(ii) a The outer shell is Li in chemical expression3YCl6. Wherein, the coating amount of the inner shell is 0.1 percent of the mass of the inner core matrix material, and the coating amount of the outer shell is 0.1 percent of the mass of the inner core matrix material; the residual lithium content on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is 930 ppm.
Example 6
A preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
s1: preparation of high nickel base material
High nickel precursor Ni0.83Co0.11Mn0.06(OH)2Lithium hydroxide and nano MgO particles are uniformly stirred and mixed, and are sintered in pure oxygen at the sintering temperature of 760 ℃, and then the product is cooled, crushed and sieved to prepare the internal core matrix material of the anode material, namely the high nickel matrix material.
S2: co-precipitation coating
Adding pure water into a reaction kettle, starting stirring, adding the high nickel matrix material into the pure water, and uniformly stirring to obtain mixed slurry. Wherein the mass ratio of the pure water to the high-nickel matrix material is 1.3: 1. Gradually adding a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate and an ammonia water solution in a molar ratio of 6:2:2 into the mixed solution to perform in-situ coprecipitation reaction, adjusting the pH value of a reaction system to 12.0-13.0 by adopting a NaOH solution in the reaction, reacting for 78min at the reaction temperature of 80 ℃, after the reaction, aging, filter-pressing and dehydrating the reaction solution, and performing vacuum drying at 145 ℃ to obtain the low-nickel hydroxide coated high-nickel matrix material.
S3: dry coating and fused salt sintering
The low nickel hydroxide coated high nickel base material, the nano LiCl particles and the nano AlCl prepared in the step S23With InCl3The particles are added into a high-speed mixer for mechanical mixing uniformly, the stirring speed of the high-speed mixer is 640rpm, and the stirring time is 45 min. Sintering for 15 hours in air atmosphere at the sintering temperature of 700 ℃, and sieving and deironing to obtain the anode material;
the molar amount of LiCl added is in stoichiometric ratio with the low nickel hydroxide coated high nickel matrix material obtained in step S2 and the BiCl added in step S33With InCl3The sum of the molar weights is 1.2:1, LiCl, AlCl3With InCl3Are all sub-nanometer.
The cathode material prepared by the method is of a core-shell structure, and the chemical expression of the core matrix material in the core-shell structure is Li (Ni)0.83Co0.11Mn0.06)0.985Mg0.015O2The internal core matrix material comprises a high-nickel ternary material and a cobalt-free high-nickel material, and the morphology of the internal core matrix material comprises single crystal and polycrystal.
The shell of the anode material is of a double-shell structure, and the double-shell structure comprises an inner-layer shell and an outer-layer shell; the chemical expression of the inner shell is LiNi0.6Co0.2Mn0.2O2(ii) a The outer shell is Li in chemical expression3Al0.5In0.5Cl6. Wherein the coating amount of the inner shell is inner1.3 percent of the mass of the core matrix material, and the coating amount of the outer shell is 0.3 percent of that of the inner core matrix material; the residual lithium content on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is 931 ppm.
Example 7
A preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
s1: preparation of high nickel base material
High nickel precursor Ni0.80Mn0.2(OH)2Lithium hydroxide, nano TiO2And uniformly stirring and mixing the particles, sintering the particles in pure oxygen at the sintering temperature of 890 ℃, and then cooling, crushing and sieving the product to obtain the internal core matrix material of the cathode material, namely the high-nickel matrix material.
S2: co-precipitation coating
Adding pure water into a reaction kettle, starting stirring, adding the high nickel matrix material into the pure water, and uniformly stirring to obtain mixed slurry. Wherein the mass ratio of the pure water to the high-nickel matrix material is 1.5: 1. And (2) gradually adding a mixed solution of nickel nitrate, cobalt nitrate and manganese nitrate and an ammonia water solution in a molar ratio of 5:2:3 into the mixed slurry to perform in-situ coprecipitation reaction, wherein a pH value of a reaction system is adjusted to 11.0-12.0 by adopting a NaOH solution in the reaction, the reaction time is 130min, the reaction temperature is 90 ℃, and after the reaction, the reaction solution is aged, subjected to filter pressing dehydration, and subjected to vacuum drying at 150 ℃ to obtain the low-nickel hydroxide coated high-nickel matrix material.
S3: dry coating and fused salt sintering
The low nickel hydroxide coated high nickel matrix material prepared in the step S2, nano LiCl particles and nano ScCl3The particles are added into a high-speed mixer for mechanical mixing uniformly, the stirring speed of the high-speed mixer is 700rpm, and the stirring time is 60 min. Sintering the mixture for 20 hours in air atmosphere at the sintering temperature of 750 ℃, and performing screening and iron removal processes to obtain the anode material;
the molar amount of LiCl added is in stoichiometric ratio with the low nickel hydroxide coated high nickel matrix material obtained in step S2 and the GaCl added in step S33Mole ofThe sum of the amounts being 1.2:1, LiCl and ScCl3Are all in submicron order.
The cathode material prepared by the method is of a core-shell structure, and the chemical expression of the core matrix material in the core-shell structure is Li (Ni)0.8Mn0.2)0.96Ti0.04O2The internal core matrix material comprises a high-nickel ternary material and a cobalt-free high-nickel material, and the morphology of the internal core matrix material comprises single crystal and polycrystal.
The shell of the anode material is of a double-shell structure, and the double-shell structure comprises an inner-layer shell and an outer-layer shell; the chemical expression of the inner shell is LiNi0.5Co0.2Mn0.3O2(ii) a The outer shell is Li in chemical expression3ScCl6. Wherein, the coating amount of the inner shell is 2.8 percent of the mass of the inner core matrix material, and the coating amount of the outer shell is 0.4 percent of the mass of the inner core matrix material; the residual lithium content on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is 852 ppm.
Example 8
A preparation method of a low-residual lithium high-nickel cathode material with a double-shell structure comprises the following steps:
s1: preparation of high nickel base material
High nickel precursor Ni0.90Mn0.10(OH)2Lithium hydroxide, nano TiO2Particles and nano-ZrO2And uniformly stirring and mixing the particles, sintering the particles in pure oxygen at 860 ℃, and then cooling, crushing and sieving the product to obtain the internal core matrix material of the cathode material, namely the high-nickel matrix material.
S2: co-precipitation coating
Adding pure water into a reaction kettle, starting stirring, adding the high nickel matrix material into the pure water, and uniformly stirring to obtain mixed slurry. Wherein the mass ratio of the pure water to the high-nickel matrix material is 1.5: 1. And (2) gradually adding a mixed solution of nickel acetate, cobalt acetate and manganese acetate and an ammonia water solution in a molar ratio of 4:2:4 into the mixed slurry to perform in-situ coprecipitation reaction, wherein a pH value of a reaction system is adjusted to 12.0-13.0 by adopting a NaOH solution in the reaction, the reaction time is 150min, the reaction temperature is 70 ℃, and after the reaction, the reaction solution is aged, subjected to filter pressing dehydration, and subjected to vacuum drying at 150 ℃ to obtain the low-nickel hydroxide coated high-nickel matrix material.
S3: dry coating and fused salt sintering
The low nickel hydroxide coated high nickel matrix material prepared in the step S2, nano LiCl particles and nano ScCl3Particles and nano-LaCl3The particles are added into a high-speed mixer for mechanical mixing uniformly, the stirring speed of the high-speed mixer is 700rpm, and the stirring time is 60 min. Sintering the mixture for 20 hours in air atmosphere at the sintering temperature of 800 ℃, and obtaining the anode material through screening and iron removal processes;
the molar amount of LiCl added was in stoichiometric ratio with the low nickel hydroxide coated high nickel matrix material obtained in step S2 and ScCl added in step S33With LaCl3The sum of the molar weights is 1.2:1, LiCl, ScCl3With LaCl3Are all nano-scale.
The cathode material prepared by the method is of a core-shell structure, and the chemical expression of the core matrix material in the core-shell structure is Li (Ni)0.90Mn0.1)0.95Zr0.025Ti0.25O2The internal core matrix material comprises a high-nickel ternary material and a cobalt-free high-nickel material, and the morphology of the internal core matrix material comprises single crystal and polycrystal.
The shell of the anode material is of a double-shell structure, and the double-shell structure comprises an inner-layer shell and an outer-layer shell; the chemical expression of the inner shell is LiNi0.4Co0.2Mn0.4O2(ii) a The outer shell is Li in chemical expression3Sc0.8La0.2Cl6. Wherein, the coating amount of the inner shell is 5 percent of the mass of the inner core matrix material, and the coating amount of the outer shell is 0.5 percent of the mass of the inner core matrix material; the residual lithium amount on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is 960 ppm.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A preparation method of a low-residual-lithium high-nickel cathode material with a double-shell structure is characterized by comprising the following steps of:
s1: mixing NiaCobMnc(OH)2Uniformly stirring the lithium hydroxide and the doping agent, and sintering in pure oxygen to obtain a high nickel matrix material;
the dopant is any one, two or three of nano metal oxides of Zr, Sr, Nb, Y, Al, Mg and Ti;
s2: stirring pure water and the high nickel substrate material uniformly, washing with water to obtain mixed slurry, adding a nickel-cobalt-manganese mixed salt solution and an ammonia water solution into the obtained mixed solution, adjusting the pH value to be alkaline, reacting, and aging, dehydrating and drying the reaction solution to obtain the low nickel hydroxide coated high nickel substrate material;
s3: uniformly stirring and mixing the low-nickel hydroxide coated high-nickel matrix material, LiCl and metal chloride with fused salt sintering performance, and sintering in an air atmosphere to obtain a low-residual lithium high-nickel cathode material with a double-shell structure;
the metal chloride with the fused salt sintering performance is InCl3、ZrCl4、YCl3、AlCl3、BiCl3、GaCl3、ScCl3And LaCl3Or a mixture of any two of them.
2. The method for preparing a double-shell structured positive electrode material with low residual lithium and high nickel content as claimed in claim 1, wherein the solution of mixed nickel, cobalt and manganese salts in step S2 is a mixed solution of water-soluble nickel salt, water-soluble cobalt salt and water-soluble manganese salt; the water-soluble nickel salt is nickel sulfate, nickel nitrate, nickel acetate or nickel chloride, the water-soluble cobalt salt is cobalt sulfate, cobalt nitrate, cobalt chloride or cobalt acetate, and the water-soluble manganese salt is manganese sulfate, manganese nitrate, manganese chloride or manganese acetate.
3. The preparation method of the double-shell structure low-residual-lithium high-nickel positive electrode material according to claim 1, wherein in the step S2, the pH value is adjusted to 11.0-13.0, the reaction time is 10-150 min, the reaction temperature is 50-90 ℃, and the reaction solution is subjected to filter pressing dehydration after reaction and vacuum drying at 80-150 ℃ to prepare the low-nickel hydroxide coated high-nickel matrix material.
4. The method for preparing the double-shell structure cathode material with low residual lithium and high nickel content according to claim 1, wherein in the step S3, the ratio of the molar quantity of LiCl to the sum of the molar quantity of the low nickel hydroxide coated on the surface of the low nickel hydroxide coated high nickel matrix material prepared in the step S2 and the molar quantity of the metal chloride with molten salt sintering property added in the step S3 is (1.0-1.2): 1.
5. The preparation method of the double-shell-structured low-residual-lithium high-nickel cathode material according to claim 1, wherein in the step S3, the stirring speed is 150-700 rpm, and the stirring time is 5-60 min.
6. The method for preparing the double-shell-structured low-residual-lithium high-nickel cathode material as claimed in claim 1, wherein the sintering temperature in the step S1 is 600-900 ℃, the sintering temperature in the step S3 is 200-800 ℃, and the sintering temperature in the step S1 is higher than the sintering temperature in the step S3.
7. The double-shell structure low-residual-lithium high-nickel cathode material prepared by the method according to any one of claims 1 to 6, wherein the cathode material is of a core-shell structure, and the chemical expression of an internal core of the core-shell structure is as follows: li (Ni)aCobMnc)1- sAsO2Wherein a is more than or equal to 0.8, b is more than or equal to 0 and less than or equal to 0.15, a + b + c is 1, and s is more than 0 and less than or equal to 0.05; the molar ratio of Ni in the inner core is not less than 0.8;
the A is any one, two or three of Zr, Sr, Nb, Y, Al, Mg and Ti;
the shell is of a double-shell structure, and the double-shell structure comprises an inner shell and an outer shell;
the chemical expression of the inner shell is LiNixCoyMnzO2Wherein x is more than or equal to 0 and less than or equal to 0.7, y is more than or equal to 0.1 and less than or equal to 1.0, and x + y + z is equal to 1;
the chemical expression of the outer shell is LimMnCl6Wherein M is more than 0 and less than or equal to 3, M + gamma n is 6, and gamma is the valence of M metal;
and M is one or two of In, Zr, Y, Al, Bi, Ga, Sc and La.
8. The double-shell-structured low-residual-lithium high-nickel cathode material as claimed in claim 7, wherein the coating amount of the inner shell is 0.01-5% of the mass of the inner core; the coating amount of the outer shell is 0.01-0.5% of the mass of the inner core; the residual lithium amount on the surface of the low-residual lithium high-nickel cathode material with the double-shell structure is not more than 1000 ppm.
9. A lithium ion battery, characterized in that the low residual lithium high nickel cathode material with a double shell structure in claim 7 or 8 is used as the cathode of the lithium ion battery.
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