CN111689525B

CN111689525B - Preparation method of orthosilicate anode material coated ternary material

Info

Publication number: CN111689525B
Application number: CN202010463540.9A
Authority: CN
Inventors: 余柏烈; 魏国祯; 曾雷英
Original assignee: Xiamen Xiaw New Energy Materials Co ltd
Current assignee: Xiamen Xiaw New Energy Materials Co ltd
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2022-08-19
Anticipated expiration: 2040-05-27
Also published as: CN111689525A

Abstract

The invention discloses a preparation method of an orthosilicate anode material coated ternary material. The chemical composition general formula of the orthosilicate anode material is Li ₂ MSiO ₄ (M ═ at least one of Fe, Mn, Co and Ni), the coating content of the positive electrode material accounts for 0.01-10% of the mass fraction of the positive electrode material, and the coating thickness is 10-1000 nm. The process of the invention is as follows: firstly, the residual lithium content and components on the surface of the ternary material are measured, then a nano-scale lithium source, a corresponding metal M source, a silicon source and the like are added according to the coating content and the molecular molar ratio, and the ternary anode material coated by the orthosilicate anode material can be obtained by fluidization mixing, tabletting, sintering, powder making and sieving. The preparation method is a pure dry process, is simple and feasible, can reduce the residual lithium on the surface, simultaneously can improve the overcharge resistance and the thermal stability of the ternary material, improves the electrical property of the material, and has a certain industrial application prospect.

Description

Preparation method of orthosilicate-based anode material coated ternary material

Technical Field

The invention belongs to the technical field of lithium ion battery anode materials and preparation thereof, and particularly relates to a preparation method of an orthosilicate anode material dry-coated ternary material.

Background

With the rapid development of 3C digital electronic products, electric tools and electric vehicles, the requirements for batteries are higher and higher, and among the key technologies that restrict the development of batteries, the positive electrode material technology is one of the keys. In the actual sintering production of the cathode material, particularly the medium-high nickel ternary material, due to the volatilization of lithium, an excessive lithium source is often added to obtain a better crystal structure, so that residual lithium is often present on the surface of a product. The residual lithium refers to oxides, hydroxides, carbonates and the like of lithium on the surface of the ternary material, and the powder is easy to absorb moisture due to the high pH value of the alkaline material; the strong basicity can cause the PVDF binder to agglomerate, so that the viscosity of the battery slurry is increased and even is in a gel state, and the processing performance of the battery slurry is influenced. At present, water washing is mostly used for removing residual lithium in actual production, and although the effect is good, a series of problems of resource waste, sewage treatment, high energy consumption and the like are caused. In some researches, a small amount of precursors of various cathode materials, vanadate, phosphate and the like are added for heat treatment to reduce residual lithium on the surface, and various technologies use wet treatment technologies more, so that the method provides challenges for actual industrial production. Therefore, it is particularly critical to find a technology and a material which can perform dry coating and is suitable for industrial production.

Orthosilicate-based positive electrode material Li ₂ MSiO ₄ (M ═ at least one of Fe, Mn, Co and Ni) has good overcharge resistance and thermal stability. 1mol of orthosilicate cathode material can theoretically realize 2mol of Li ⁺ The theoretical specific capacity of the intercalation and deintercalation of (particularly) Mn series materials can reach 333mAh/g, which is higher than that of the intercalation and deintercalation of only 1mol of Li ⁺ LiFePO of (2) ₄ Si has a lower electronegativity than P, and contributes to an increase in electron conductivity.

In patent CN 104393260 a, a method for preparing a lithium-manganese-rich material coated with silicate is proposed, which comprises adding ethyl orthosilicate, lithium salt and water and alcohol solution of other metal soluble salts into a lithium-manganese-rich positive electrode material, refluxing and stirring, evaporating the solution to dryness, and calcining under vacuum or inert gas protection to obtain the lithium-manganese-rich positive electrode material coated with orthosilicate. Patent CN 104752685 a proposes a lithium ion battery positive electrode material and a preparation method thereof, in which orthosilicate ester and a salt solution containing Mn (and M) are mixed to form a sol, then a positive electrode material core is added, an orthosilicate coating layer containing Mn (and M) is formed on at least a part of the surface of the positive electrode material core, and finally the lithium ion battery positive electrode material is obtained by heat treatment. In the related patents of the currently applied orthosilicate based cathode material coating, wet coating is more selected, and although the uniformity of the coating layer can be ensured, the cost is increased in the actual industrial production, and the process is more complicated and is not beneficial to the industrial application. Patent CN 105990563 a proposes a secondary lithium battery, its positive electrode material and a method for preparing the positive electrode material, in which a main material of the lithium-containing transition metal oxide LixMyN1-yO2- α a β is prepared, and then a Si source is added to sinter the lithium-containing transition metal oxide LixMyN1-yO2- α a β to prepare the LixMyN1-yO2- α a β positive electrode material with the surface coated with the lithium-containing transition metal silicate xLi2O · yN' Oa · SiO2- λ B ζ coating layer. Only quantify the coating amount in the patent, other key indexes are not mentioned, the effect influence of the mixing mode on the coating is large, the conventional means or the mixing effect is poor, and the coating uniformity is difficult to guarantee. Or the cost is high, and the exertion of the practical performance of the coating material is limited. In addition, in order to prepare products with excellent performance, the anode material, especially high-nickel products, often needs to be added with excessive lithium source for sintering before sintering, the synthesis route often causes excessive surface residual lithium, the content of the general residual lithium is 0.5-5%, the subsequent battery manufacturing process is influenced, joint treatment is rarely considered in the surface residual lithium treatment, and the input amount and the input mode of the additive are relatively extensive.

Disclosure of Invention

In order to improve the capacity of the medium-high nickel ternary cathode material, further stabilize the structure of the medium-high nickel ternary cathode material, enhance the electrical property of the medium-high nickel ternary cathode material and effectively remove residual lithium on the surface of the cathode material, the invention aims to provide a preparation method of an orthosilicate system cathode material-coated ternary material, and the whole preparation process is a pure dry preparation process and is beneficial to industrial application and popularization.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a preparation method of an orthosilicate anode material coated ternary material is characterized by comprising the following steps: the method comprises the following steps:

1) respectively dissolving nickel salt, cobalt salt and manganese salt in water, mixing according to a certain molar ratio, obtaining hydroxide containing three metal salts by adopting a coprecipitation method, and marking the hydroxide as a precursor Ni _x Co _y Mn _(1-x-y) (OH) ₂ ；

2) Mixing lithium salt and the precursor obtained in the step 1) according to a certain lithium metal molar ratio, sintering (SJ1), and milling to obtain a corresponding ternary cathode material;

3) taking the ternary cathode material obtained in the step 2) to carry out surface residual lithium content test, and accurately measuring the residual lithium content and component information;

4) according to different coating amounts, the chemical formula of the positive electrode material of the orthosilicate system is combined with Li ₂ MSiO ₄ (MAt least one of Fe, Mn, Co and Ni) and the condition of residual lithium on the surface, adding a nano-scale lithium source, a silicon source and a metal M source into the ternary cathode material obtained in the step 2), mixing in a fluidized manner, tabletting, Sintering (SJN), pulverizing, sieving and repeating the steps for multiple times to obtain the ternary material coated by the orthosilicate cathode material.

Further, precursor Ni in the step 1) above _x Co _y Mn _(1-x-y) (OH) ₂ Wherein, 0.5<x<0.9，0.05<y<0.25，0<x+y<1。

Further, preferably, x is 0.6 and y is 0.2.

Further, preferably, x is 0.8 and y is 0.1.

Further, the molar ratio of the lithium metal in the step 2) is 1.01<Li:M _{General (1)} <1.30。

Further, it is preferable that the molar ratio of lithium metal is 1.05. ltoreq. Li: M _{General (1)} ≤1.20。

Further, in the step 4), the coating content of the orthosilicate based anode material accounts for 0.01-10% of the mass fraction of the anode material, and the thickness of the coating layer is 10-1000 nm.

Further, in the step 4), the coating content of the orthosilicate-based positive electrode material is preferably 0.01 to 1 mass percent of the positive electrode material, and the thickness of the coating is preferably 10 to 100 nm.

Further, the source of lithium in the orthosilicate-based positive electrode material in step 4) includes residual lithium on the surface of the ternary material and an additional lithium source, wherein the lithium source includes but is not limited to one of lithium oxide, lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate; wherein the silicon source includes but is not limited to one of silicon dioxide, lithium silicate, and organosilicon.

Further, the metal M source in step 4) includes, but is not limited to, one or more of oxides, carbonates, nitrates, and the like of Fe, Mn, Co, Ni.

Further, in the step 4), fluidized mixing is carried out, specifically, the ternary material obtained in the step 2) and other materials are sprayed into a fluidized mixing coating machine through medium-low speed air flow in proportion, mixing is continued for 5-60 min after the feeding is finished, the ternary material is dispersed in a fluidized bed, the nanoscale additive is sprayed on a ternary material matrix, and other nanoscale materials are continuously adsorbed on the surface of matrix particles, so that the mixing process is finished.

Furthermore, the pressure of the medium-low speed airflow is 0.01-0.5 MPa, so that the materials are dispersed as much as possible after entering the fluidized bed, particle agglomeration and surface residual lithium stripping are eliminated, and the main structure of the matrix is not influenced.

Further, the step 4) is added with a nanoscale lithium source, a silicon source and a metal M source, wherein the first addition molar ratio is Li: and (Si + M) is 0.5-1: 1, and the increase of the ratio of (Si + M) to (M) is increased step by step for multiple times along with the sintering, wherein the increase of the ratio of (Si + M) to (M) is 10% -50%, namely the ratio of (Li): (Si + M) 0.55-1.5: 1, third Li: (Si + M) 0.6-2: 1 … …; until the test and design values Li: (Si + M) ═ 2.01: 1.

Furthermore, the silicon source and the metal M source are added in the step 4), the grain size of the D50 added for the first time is 500-1000nm, and then the grain size is reduced step by step for multiple times along with the progress of sintering, the reduction range is 100-1000%, namely the grain size is 50-500nm for the second time and … … for the third time, so that the cladding layer is densified, redundant additive impurities are effectively eliminated, and the optimal cladding effect is achieved.

Further, the mixture obtained in the step 4) is tabletted under the pressure of 0.1-0.3 MPa, and the thickness of the pressed sample is 1-20 mm.

Further, the mixture is Sintered (SJN) in the step 4), wherein the SJN is sintered for multiple times, N is more than or equal to 2 and less than or equal to 10, the sintering temperature is 300-700 ℃, and the heat preservation time is 1-10 hours.

Further, preferably, the mixture is Sintered (SJN) in the step 4), wherein the SJN is sintered for multiple times, N is more than or equal to 4 and less than or equal to 6, the sintering temperature is 300-500 ℃, and the heat preservation time is 2-5 hours.

Further, the mixture Sintering (SJN) in the step 4) is carried out for multiple times, wherein the SJN is more than or equal to 2 and less than or equal to 10, the first sintering temperature is 700 ℃, the sintering temperature is continuously reduced along with the increase of the sintering times, the reduction range is 50-100 ℃, namely the second sintering temperature is 650 ℃, and the third sintering temperature is 300- … … ℃.

After the scheme is adopted, the invention has the beneficial effects that:

1. a certain amount of lithium source, silicon source and corresponding metal compound are added, and the condition of residual lithium on the surface of the ternary material is combined for mixing, tabletting and sintering, so that the content of residual lithium is effectively reduced. The tabletting treatment makes the contact between the base material and the additive tighter, the surface defects are filled more effectively, and the reaction is more sufficient.

2. The orthosilicate system anode material has poor conductivity, and a thin and uniform nano layer is formed on the surface of the ternary material, so that the problem of poor conductivity is effectively solved by the nano material, the electrical property of the ternary material is fully exerted, and the overall electrical property, the overcharge resistance and the thermal stability of the material are improved.

3. The problems of non-uniformity and high wet cost of the traditional solid phase mixing (ball milling mixing and high mixing machine mixing) are solved, and the problem of local agglomeration of the traditional mixing mode is solved by optimizing and improving the mixing mode and equipment and mixing the nanoscale additive in a spraying mode and a base material in a contact mode. The additive is adsorbed on the surface of the substrate to repair the surface defects. And optimizing sintering for many times, continuously reducing and repairing surface defects and improving surface active sites through the change condition of the specific surface area, and effectively forming a uniform coating layer on the surface of the material. The additive is dispersed uniformly, the coating amount is less, the coating layer is relatively thin, and the synthesis temperature can be reduced.

4. The material selected in the whole flow is cheap and easy to obtain, the preparation process is simple, the process is a pure dry process, and the industrial popularization and application are easy. The main body of the whole system is conventional equipment, and is more beneficial to popularization and application, although the main body structure of the equipment is common, the main body structure is not simply superposed and applied, and a more perfect mixing effect is achieved by improving the matching mode of the equipment and optimizing and improving key components in the key equipment to a greater extent.

Drawings

FIGS. 1 and 2 are SEM images of a synthesized final product;

FIG. 3 is an SEM image of a product obtained by conventional solid phase mixing;

FIG. 4 shows an apparatus used in the production process of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and examples. It should be noted that, if not conflicting, the embodiments of the present invention and the features in the embodiments may be combined with each other within the scope of the present invention.

Example 1

Respectively dissolving nickel salt, cobalt salt and manganese salt in water, mixing according to a molar ratio of 6:2:2, and obtaining hydroxide containing three metal salts by adopting a coprecipitation method; according to the molar ratio of lithium metal Li to M _{General (1)} Mixing lithium salt and the precursor, sintering and pulverizing to obtain the corresponding ternary cathode material, which is marked as sample 1. And (3) testing the residual lithium content on the surface of the sample 1, and accurately measuring the residual lithium content and the component information. According to the mol ratio of Li: a lithium source and an additive were added in a ratio of (Si + M) ═ 0.8:1, the particle size of the additive was 500nm, fluidized mixing was carried out for 30min, and tabletting was carried out under a pressure of 0.10MPa and the sintering temperature (SJ2) was 600 ℃ and the sample 2 was recorded. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 2, and accurately determining the content of the residual lithium and component information. According to a molar ratio of Li: (Si + M) ═ 1.2:1 was added to the lithium source and additives, the particle size of the additives was 250nm, fluidized mixing was carried out for 30min, and the tablets were pressed under a pressure of 0.10MPa and the sintering (SJ3) temperature was 550 ℃ and the sample 3 was recorded. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 3, and accurately determining the content of the residual lithium and component information. According to the mol ratio of Li: (Si + M) ═ 1.6:1 was added to the lithium source and additives, the particle size of the additives was 100nm, fluidized mixing was carried out for 30min, and the tablets were pressed under a pressure of 0.10MPa and the sintering (SJ4) temperature was 500 ℃ and the sample was designated as sample 4. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 4, and accurately determining the content of the residual lithium and component information. According to a molar ratio of Li: lithium source and additive are added in a ratio of (Si + M) ═ 2:1, the additive particle size is 40nm, fluidized mixing is carried out for 30min, tabletting is carried out under a pressure of 0.10MPa, and the sintering temperature (SJ5) is 450 ℃, and the sample 5 is marked. The sample 5 is subjected to surface residual lithium and additive (Si + M) content test, and the residual is accurately measuredLithium content and composition information. According to a molar ratio of Li: (Si + M) ═ 2.01:1 was added to the lithium source and additives, the particle size of the additives was 10nm, fluidized mixing was carried out for 30min, and the tablets were pressed under a pressure of 0.10MPa and the sintering (SJ6) temperature was 400 ℃ and the sample was designated as sample 6.

Comparative example 1

For comparison, the fluidized mixing process of example 1 was changed to a conventional ball-milling mixing process, and the corresponding samples were designated as comparative sample 2 and comparative sample 3 … …

Comparative example 2

And for comparison, the sintering is simplified, the coating adopts one-step sintering to complete sample preparation, namely, the content of residual lithium and additives (Si + M) on the surface is tested, and the content of the residual lithium and the component information are accurately measured. According to the mol ratio of Li: a lithium source and an additive were added in a ratio of (Si + M) ═ 2.01:1, the particle size of the additive was 10nm, fluidized mixing was carried out for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and a sintering (SJ2) temperature of 400 ℃ to obtain a comparative sample 21.

Comparative example 3

And for comparison, the sintering is simplified, the coating adopts one-step sintering to complete sample preparation, namely, the content of residual lithium and additives (Si + M) on the surface is tested, and the content of the residual lithium and the component information are accurately measured. According to the mol ratio of Li: adding lithium source and additive (Si + M) ═ 2.01:1, the particle diameter of additive is 10nm, fluidizing and mixing for 30min, tabletting under the pressure of 0.10MPa, and sintering (SJ2) temperature is 600 ℃; crushing, mixing in a fluidized manner for 30min, tabletting under the pressure of 0.10MPa, and sintering (SJ3) at the temperature of 560 ℃; crushing, mixing in a fluidized way for 30min, tabletting under the pressure of 0.10MPa, and sintering (SJ4) at the temperature of 500 ℃; crushing, mixing in a fluidized way for 30min, tabletting under the pressure of 0.10MPa, and sintering (SJ5) at the temperature of 450 ℃; crushed, fluidized and mixed for 30min, and pressed into tablets at a pressure of 0.10MPa and a sintering temperature (SJ6) of 400 ℃ to obtain a reference 31.

TABLE 1 results of testing physicochemical properties of samples

Example 1	Sample No. 1	Sample 2	Sample 3	Sample 4	Sample No. 5	Sample No. 6
							Surface residual Li +/%)	0.561	0.612	0.512	0.401	0.256	0.248
BET/m ³ *g ^-1	0.435	0.512	0.473	0.289	0.243	0.239
							Comparative example 1	/	Comparative sample 2	Comparative sample 3	Comparative sample 4	Comparative sample 5	Comparative sample 6
Surface residual Li +/%)	/	0.556	0.531	0.446	0.412	0.422
							BET/m ³ *g ^-1	/	0.452	0.401	0.356	0.432	0.551

As can be seen from table 1: in example 1, as the multiple sintering progresses, the surface residual Li decreases to a lower level, and the BET value in sample 6 decreases to a smaller extent than that in sample 5, and gradually approaches equilibrium. BET continuously modifies surface defects as the surface coating material continues to fall, filling voids. The coating is more and more uniform and compact. In contrast, in comparative example 1, although the residual Li was decreased continuously, the decrease was limited, and the BET tended to increase after decreasing, while the decrease remained high. Therefore, the limitation of the traditional solid-phase mixing mode is that the fine (nanoscale or sub-nanoscale) materials cannot be uniformly dispersed. BET do not decrease back-increase indicates that the additive is locally agglomerated, rather than coated on the substrate surface.

TABLE 2 sample physicochemical and Electrical Properties test results

As can be seen from table 2: sample 6 is superior in capacity, normal temperature, high temperature cycles, etc. The method has the advantages that the factors influencing the final coating effect of the material are more, the material obtained by simple adjustment/replacement of the conventional method has certain difference with the material obtained in the invention in performance, and the method has certain improvement in selection.

Example 2

Respectively dissolving nickel salt, cobalt salt and manganese salt in water, mixing according to a molar ratio of 6:2:2, and obtaining hydroxide containing three metal salts by adopting a coprecipitation method; according to the molar ratio of lithium metal Li to M _{General assembly} The lithium salt and the precursor were mixed, sintered, and milled to obtain the corresponding ternary positive electrode material, which was designated as sample 21. And (3) testing the residual lithium content on the surface of the sample 21, and accurately measuring the residual lithium content and the component information. According to a molar ratio of Li: lithium source and additive were added at a ratio of (Si + M): 0.6:1, the particle size of the additive was 800nm, fluidized mixing was carried out for 30min, tabletting was carried out under a pressure of 0.10MPa, and the sintering temperature (SJ2) was 600 ℃ and was recorded as sample 22. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 22, and accurately determining the content of the residual lithium and component information. According to the mol ratio of Li: a lithium source and an additive were added to the mixture in a ratio of (Si + M) ═ 0.8:1, the particle size of the additive was 400nm, the mixture was fluidized and mixed for 30 minutes, and the mixture was pressed into tablets under a pressure of 0.10MPa and a sintering temperature (SJ3) was 550 ℃ to obtain sample 23. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 23, and accurately determining the content of the residual lithium and component information. According to the mol ratio of Li: (Si + M) ═ 1:1 lithium source and additive were added, the particle size of the additive was 200nm, fluidized mixing was carried out for 30min, and tabletting was carried out under a pressure of 0.10MPa and the sintering (SJ4) temperature was 500 ℃ and the sample was designated as sample 24. And (3) testing the residual lithium and additive (Si + M) content on the surface of the sample 24, and accurately determining the residual lithium content and component information. According to the mol ratio of Li: a lithium source and an additive were added in a ratio of (Si + M) ═ 1.2:1, the particle size of the additive was 100nm, fluidized mixing was carried out for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and a sintering (SJ5) temperature of 450 ℃ to obtain sample 25. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 25, and accurately measuring the content of the residual lithium and component information. According to the mol ratio of Li: (Si + M) ═ 1.4:1 lithium source incorporation and additionThe additive, the particle size of which is 50nm, was fluidized and mixed for 30min, and was tabletted under a pressure of 0.10MPa and a sintering (SJ6) temperature of 400 ℃ and was recorded as sample 26. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 26, and accurately determining the content of the residual lithium and component information. According to the mol ratio of Li: (Si + M) ═ 1.6:1 was added to the lithium source and additives, the particle size of the additives was 25nm, fluidized mixing was conducted for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and the sintering temperature (SJ5) was 350 ℃ and this was recorded as sample 27. And (3) testing the residual lithium and the additive (Si + M) content on the surface of the sample 27, and accurately measuring the residual lithium content and the component information. According to the mol ratio of Li: lithium source and additive were added at a ratio of (Si + M) ═ 1.8:1, the additive particle size was 10nm, fluidized mixing was carried out for 30min, tabletting was carried out under a pressure of 0.10MPa, and the sintering (SJ6) temperature was 300 ℃, and this was recorded as sample 28. And (3) testing the residual lithium and additive (Si + M) content on the surface of the sample 28, and accurately determining the residual lithium content and the component information. According to a molar ratio of Li: (Si + M) ═ 2.01:1 was added to the lithium source and additives, the particle size of the additives was 5nm, fluidized mixing was conducted for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and the sintering temperature (SJ6) was 300 ℃ and this was designated as sample 29.

Example 3

Respectively dissolving nickel salt, cobalt salt and manganese salt in water, mixing according to a molar ratio of 6:2:2, and obtaining hydroxide containing three metal salts by adopting a coprecipitation method; according to the molar ratio of lithium metal Li to M _{General assembly} The lithium salt and the precursor were mixed, sintered, and milled to obtain the corresponding ternary positive electrode material, which was designated as sample 31. And (3) testing the residual lithium content on the surface of the sample 31, and accurately measuring the residual lithium content and the component information. According to the mol ratio of Li: lithium source and additive were added at a ratio of (Si + M) ═ 0.5:1, the particle size of the additive was 500nm, fluidized mixing was carried out for 30min, tabletting was carried out under a pressure of 0.10MPa, and the sintering temperature (SJ2) was 600 ℃, and this was recorded as sample 32. And (3) testing the residual lithium and additive (Si + M) content on the surface of the sample 32, and accurately measuring the residual lithium content and the component information. According to a molar ratio of Li: a lithium source and an additive were added to the mixture in a ratio of (Si + M) ═ 0.8:1, the particle size of the additive was 200nm, the mixture was fluidized and mixed for 30 minutes, and the mixture was pressed into tablets under a pressure of 0.10MPa and a sintering temperature (SJ3) was 550 ℃ to obtain sample 33. Sample 33 was subjected to surface residual lithium and additionAnd (4) testing the content of the agent (Si + M) to accurately measure the content of residual lithium and component information. According to a molar ratio of Li: a lithium source and an additive were added in a ratio of (Si + M) ═ 1.1:1, the particle size of the additive was 80nm, fluidized mixing was carried out for 30min, and tabletting was carried out under a pressure of 0.10MPa and the sintering temperature (SJ4) was 500 ℃ and designated as sample 34. And (3) testing the residual lithium and additive (Si + M) content on the surface of the sample 34, and accurately measuring the residual lithium content and the component information. According to a molar ratio of Li: lithium source and additive were added at a ratio of (Si + M) ═ 1.4:1, the additive particle size was 40nm, fluidized mixing was carried out for 30min, tabletting was carried out under a pressure of 0.10MPa, and the sintering (SJ5) temperature was 450 ℃, and sample 35 was recorded. And (3) testing the content of residual lithium and additives (Si + M) on the surface of the sample 35, and accurately measuring the content of the residual lithium and component information. According to the mol ratio of Li: (Si + M) ═ 1.7:1 was added to the lithium source and additives, the particle size of the additives was 20nm, fluidized mixing was carried out for 30min, and the tablets were pressed under a pressure of 0.10MPa and the sintering (SJ6) temperature was 400 ℃ and the sample was designated as 36. And (3) testing the residual lithium and additive (Si + M) content on the surface of the sample 36, and accurately measuring the residual lithium content and component information. According to a molar ratio of Li: (Si + M) ═ 2.01:1 was added to the lithium source and additives, the particle size of the additives was 10nm, fluidized mixing was conducted for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and the sintering temperature (SJ5) was 350 ℃ and this was designated as sample 37.

Example 4

Respectively dissolving nickel salt, cobalt salt and manganese salt in water, mixing according to a molar ratio of 6:2:2, and obtaining hydroxide containing three metal salts by adopting a coprecipitation method; according to the molar ratio of lithium metal Li to M _{General assembly} And (5) mixing the lithium salt and the precursor, sintering and pulverizing to obtain the corresponding ternary cathode material, which is marked as sample 41. And (4) testing the residual lithium content on the surface of the sample 41 to accurately measure the residual lithium content and the component information. According to a molar ratio of Li: (Si + M) ═ 1:1 lithium source and additive were added, the particle size of the additive was 500nm, fluidized mixing was carried out for 30min, and tabletting was carried out under a pressure of 0.10MPa and the sintering (SJ2) temperature was 600 ℃ and the sample was designated as 42. And (3) testing the residual lithium and the additive (Si + M) content on the surface of the sample 42, and accurately measuring the residual lithium content and the component information. According to a molar ratio of Li: adding lithium source and additive in the ratio of (Si + M) ═ 1.5:1, the additive grain size is 100nm, fluidizing and mixing30min, tabletting at a pressure of 0.10MPa and a sintering (SJ3) temperature of 550 ℃ and recording as sample 43. And (3) testing the residual lithium and the additive (Si + M) content on the surface of the sample 43, and accurately measuring the residual lithium content and the component information. According to the mol ratio of Li: a lithium source and an additive were added in a ratio of (Si + M) ═ 2.01:1, the particle size of the additive was 10nm, fluidized mixing was carried out for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and a sintering (SJ4) temperature of 500 ℃ to obtain sample 44.

Example 5

Respectively dissolving nickel salt, cobalt salt and manganese salt in water, mixing according to a molar ratio of 6:2:2, and obtaining hydroxide containing three metal salts by adopting a coprecipitation method; according to the molar ratio of lithium metal Li to M _{General assembly} The lithium salt and the precursor were mixed, sintered, and milled to obtain the corresponding ternary positive electrode material, which was designated as sample 51. And (3) testing the residual lithium content on the surface of the sample 51, and accurately measuring the residual lithium content and the component information. According to the mol ratio of Li: lithium source and additive were added at a ratio of (Si + M) ═ 1.6:1, the additive particle size was 500nm, fluidized mixing was carried out for 30min, tabletting was carried out under a pressure of 0.10MPa, and the sintering (SJ2) temperature was 500 ℃, and this was recorded as sample 52. And (3) testing the residual lithium and additive (Si + M) content on the surface of the sample 52, and accurately measuring the residual lithium content and the component information. According to the mol ratio of Li: lithium source and additive were added at a ratio of (Si + M): 1.8:1, the particle size of the additive was 200nm, fluidized and mixed for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and a sintering (SJ3) temperature of 400 ℃ to obtain sample 53. The sample 53 is subjected to surface residual lithium and additive (Si + M) content testing, and the residual lithium content and component information are accurately determined. According to a molar ratio of Li: (Si + M) ═ 2.01:1 was added to the lithium source and additives, the particle size of the additives was 50nm, fluidized mixing was conducted for 30min, and the mixture was pressed into tablets under a pressure of 0.10MPa and the sintering temperature (SJ4) was 300 ℃ and designated as sample 54.

TABLE 3 sample physicochemical and Electrical Properties test results

As can be seen from table 3: the quality of the coating effect is closely related to the specific surface area of the material, the better the coating effect is, the smaller the BET value is, the more complete and compact the surface repair of the material is. On the other hand, from the electrical property, the sintering times of the samples 29 and 37 are more in the preparation process, and the addition mode/collocation mode of the additive is more beneficial to forming a compact nano structure on the surface of the material, so that the corrosion of the electrolyte is more effectively resisted in the charging and discharging processes, the body structure is more stable, and the cycle performance is better.

Fig. 1 and 2 are SEM images of the resultant final product, and it can be seen that the matrix particles are dispersed, less agglomerated, and a layer of gray additive is uniformly distributed on the surface.

Fig. 3 is an SEM image of a product obtained by conventional solid phase mixing, and it can be seen from the SEM image that the aggregation between matrix particles is severe, which is unstable during the circulation process, and affects the performance of the electrical properties, and the gray additive is not uniformly distributed, and the matrix is exposed much, and the expected effect cannot be achieved.

FIG. 4 shows an apparatus used in the production process of the present invention. The gas generating device generates high-pressure gas to provide transportation power for materials. Firstly, the matrix material is put into the fluidized bed from the matrix bin under the conveying of high-pressure gas, and the irregularly moving and fully dispersed solid particles are formed in the fluidized bed. And then adding an additive, wherein the nanoscale additive continuously enters the fluidized bed under the action of the dispersing sprayer to be mixed with the base material, and the base material is micron-sized, and the additive is nanoscale, so that the nanoscale additive continuously collides in the fluidized bed, and the nanoscale additive can be continuously adsorbed on the surface of the base material according to the characteristics of the powder material, so that the surface defects are continuously repaired, and a compact and uniform structure is preliminarily formed.

The principles and embodiments of the present invention are explained herein using specific examples, and the above descriptions of examples and comparative examples are only used to help understand the method of the present invention and its core ideas; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. Therefore, the present invention is not limited to the specific embodiments and the equivalent structures or equivalent processes, which are directly or indirectly applied to other related technical fields, and the same principles are included in the scope of the present invention. And should not be construed as limiting the invention.

Claims

1. A preparation method of an orthosilicate anode material coated ternary material is characterized by comprising the following steps: the method comprises the following steps:

1) respectively dissolving nickel salt, cobalt salt and manganese salt in water, mixing according to a certain molar ratio, obtaining hydroxide containing three metal salts by adopting a coprecipitation method, and marking as a precursor Ni _x Co _y Mn _（1-x-y） (OH) ₂ ；

2) According to a certain lithium metal mole ratio, the ratio is 1.01<Li:M _{General assembly} <1.30, mixing lithium salt with the precursor obtained in the step 1), sintering SJ1, and milling to obtain a corresponding ternary cathode material; SJ1 is sintered for one time;

4) according to different coating amounts, the chemical formula of the positive electrode material of the orthosilicate system is combined with Li ₂ MSiO ₄ Adding a nanoscale lithium source, a silicon source and a metal M source into the ternary cathode material obtained in the step 2), mixing in a fluidized manner, tabletting, sintering SJN, pulverizing, and sieving for multiple times, and gradually reducing the particle sizes of the silicon source and the metal M source along with the sintering to obtain the ternary material coated by the orthosilicate system cathode material; wherein the lithium source comprises one of lithium oxide, lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate; its SJN is multiple sintering.

2. The method for preparing the orthosilicate anode material-coated ternary material according to claim 1, wherein the precursor Ni in the step 1) is Ni _x Co _y Mn _（1-x-y） (OH) ₂ Wherein, 0.5<x<0.9，0.05<y<0.25，0<x+y<1。

3. The method for preparing the orthosilicate based cathode material-coated ternary material according to claim 1, wherein the coating content of the orthosilicate based cathode material in the step 4) accounts for 0.01-10% of the mass fraction of the cathode material, and the coating thickness is 10-1000 nm.

4. The method as claimed in claim 1, wherein the lithium source in the orthosilicate based cathode material in step 4) includes residual lithium on the surface of the ternary material and an additional lithium source, and wherein the silicon source includes one of silicon dioxide, lithium silicate and organosilicon.

5. The method for preparing an orthosilicate based cathode material coated ternary material according to claim 1, wherein the metal M source in step 4) comprises one or more of oxides, carbonates and nitrates of Fe, Mn, Co and Ni.

6. The method for preparing an orthosilicate based anode material-coated ternary material according to claim 1, wherein in the step 4), the ternary material obtained in the step 2) and other materials are sprayed into a fluidization mixing coating machine through medium-low speed airflow according to a certain proportion, the ternary material and other materials are continuously mixed for 5-60 min after the charging is completed, the ternary material is dispersed in a fluidization bed, the nanoscale additive is sprayed on a ternary material matrix, and other nanoscale materials are continuously adsorbed on the surface of matrix particles, so that the mixing process is completed.

7. The method for preparing an orthosilicate anode material-coated ternary material according to claim 6, wherein the pressure of the medium-low speed airflow is 0.01-0.5 MPa, so that the material is dispersed as much as possible after entering a fluidized bed, particle agglomeration is eliminated, residual lithium on the surface is stripped, and the main structure of the matrix is not affected.

8. The method for preparing an orthosilicate anode material-coated ternary material according to claim 1, wherein the step 4) is performed by adding a nanoscale lithium source, a nanoscale silicon source and a nanoscale metal M source, wherein the first-time molar ratio of the nanoscale lithium source to the nanoscale silicon source to the metal M source is Li: (Si + M) = 0.5-1: 1, and with the increase of the sintering times, increasing the distribution step by step for multiple times, wherein the increase is 10% -50%, namely, the Li is distributed for the second time: (Si + M) = 0.55-1.5: 1, third Li: (Si + M) = 0.6-2: 1; until the test and design values Li: (Si + M) =2.01: 1.

9. The method as claimed in claim 1, wherein the silicon source and the metal M source are added in the step 4), the particle size of D50 added for the first time is 500-1000nm, the particle size is gradually reduced for multiple times with the increase of sintering times, the reduction range is 100-1000%, that is, the particle size is 50-500nm for the second time and 5-250nm for the third time, the small particle size material continuously fills the defect of large particle coating, the surface is modified, the coating layer is densified, and the excessive additive impurities are effectively eliminated, so as to achieve the best coating effect.

10. The method for preparing the orthosilicate based cathode material-coated ternary material according to claim 1, wherein the mixture obtained in the step 4) is tabletted at a pressure of 0.1-0.3 MPa and a sample pressing thickness of 1-20 mm.

11. The method as claimed in claim 1, wherein the sintering SJN of the mixture in step 4) has a temperature of 2-10, the first sintering temperature is 500-700 ℃, the sintering temperature is decreased with the increase of the sintering frequency, the decrease range is 50-100 ℃, i.e. the second sintering temperature is 400-650 ℃, and the third sintering temperature is 300-600 ℃.