CN117342625A

CN117342625A - Positive electrode material precursor, preparation method thereof, positive electrode material and lithium ion battery

Info

Publication number: CN117342625A
Application number: CN202210753975.6A
Authority: CN
Inventors: 张同宝; 张宇; 汪碧微; 朱烨; 陈芳; 贾银娟
Original assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Current assignee: China Petroleum and Chemical Corp; Sinopec Shanghai Research Institute of Petrochemical Technology
Priority date: 2022-06-28
Filing date: 2022-06-28
Publication date: 2024-01-05

Abstract

The invention relates to the field of lithium ion batteries, and discloses a positive electrode material precursor, a preparation method thereof, a positive electrode material and a lithium ion battery. The precursor of the positive electrode material is a secondary microsphere formed by agglomeration of primary particles, the secondary microsphere comprises an inner core layer, an intermediate layer and an outermost layer, the ratio of the intensities of the diffraction peaks of (110) crystal faces to (102) crystal faces in the X-ray diffraction spectrum of the inner core layer is 1-8, and the specific surface area of the secondary microsphere is 0.5-15m ² And/g. The preparation method of the positive electrode material precursor comprises the following steps: carrying out precipitation reaction on the metal source solution, the precipitator solution and the complexing agent solution to obtain a reaction productA material; carrying out solid-liquid separation and drying on the reaction product; wherein the total reaction time is recorded as R hours, and the solid content of the precipitation reaction system is not higher than 7wt% in the first 1/8R hours of the reaction. The positive electrode material prepared by the positive electrode material precursor is applied to a lithium ion battery, and the specific discharge capacity of the positive electrode material precursor is obviously improved.

Description

Positive electrode material precursor, preparation method thereof, positive electrode material and lithium ion battery

Technical Field

The invention relates to the field of lithium ion batteries, in particular to a positive electrode material precursor, a preparation method thereof, a positive electrode material and a lithium ion battery.

Background

The development of electric tools and electronic devices requires a positive electrode material with high energy density and long-cycle stability. Lithium nickel cobalt manganese or lithium nickel cobalt aluminum composite oxide having a layered structure is an important positive electrode active material of a lithium secondary battery.

In the lithium nickel cobalt manganese or lithium nickel cobalt aluminum composite oxide, nickel, cobalt, manganese and aluminum play a role in ternary synergy, and the discharge specific capacity of the positive electrode material can be improved by improving the content of nickel in the positive electrode material, so that the energy density of the lithium battery is improved. However, after the nickel content in the components reaches a certain content, the specific discharge capacity is not obviously improved, and a new mechanism for improving the specific discharge capacity is required to be developed. And secondly, as the discharge specific capacity of the positive electrode material is improved, the electrochemical activity of the material is increased, so that the cycle stability is deteriorated. These problems all need to be solved.

The lithium nickel cobalt manganese or lithium nickel cobalt aluminum composite oxide is generally prepared by a coprecipitation process to prepare a precursor material, and then is produced by high temperature solid phase reaction with lithium salt. The property of the precursor determines the discharge specific capacity and the cycle stability of the final positive electrode material, and the design and development of a new precursor material are expected to improve the energy density and the cycle stability of the lithium nickel cobalt manganese or lithium nickel cobalt aluminum composite oxide.

Disclosure of Invention

The invention aims to solve the problem that the discharge specific capacity of a ternary positive electrode material in the charge and discharge process of a battery is low in the prior art, and provides a positive electrode material precursor, a preparation method thereof, a positive electrode material and a lithium ion battery.

In order to achieve the above object, a first aspect of the present invention provides a positive electrode material precursor, which is a secondary microsphere formed by agglomeration of primary particles; wherein the secondary microsphere comprises an inner core layer, an intermediate layer and an outermost layer from inside to outside, and the ratio of the intensities of the (110) crystal face diffraction peaks to the (102) crystal face diffraction peaks in the X-ray diffraction spectrum of the inner core layer is 1-8, preferably 1.5-4; the specific surface area of the secondary microsphere is 0.5-15m ² /g。

In a second aspect, the present invention provides a method for preparing a precursor of a positive electrode material, the method comprising the steps of:

(1) Carrying out precipitation reaction on the metal source solution, the precipitator solution and the complexing agent solution to obtain a reaction product;

(2) Carrying out solid-liquid separation and drying on the reaction product to obtain the anode material precursor;

Wherein the total reaction time is expressed as R hours, and the solid content of the precipitation reaction system is not more than 7wt%, preferably not more than 5wt%, in the first 1/8R hours from the start of the reaction.

Preferably, the concentration of the complexing agent in the precipitation reaction system gradually increases, and the concentration change rate of the complexing agent gradually decreases.

Preferably, the concentration of the complexing agent is varied at a rate of 1 mol/L.multidot.h or less, preferably from 0.001 to 1 mol/L.multidot.h, and more preferably from 0.001 to 0.5 mol/L.multidot.h.

Preferably, the concentration of the complexing agent is changed at a rate of not less than 0.021 mol/L.multidot.h, preferably 0.021 to 1 mol/L.multidot.h, more preferably 0.021 to 0.5 mol/L.multidot.h, within the first 1/8R hour of the start of the reaction.

Preferably, the time from the addition of the complexing agent to the completion of the reaction to the concentration of the complexing agent of 80% or more in the precipitation reaction system is not more than 1/4R hours.

In a third aspect, the present invention provides a positive electrode material precursor prepared by the method described in the second aspect.

A fourth aspect of the present invention provides a positive electrode material comprising a lithium source and a positive electrode material precursor according to the first or third aspect above.

A fifth aspect of the present invention provides a lithium ion battery comprising the positive electrode material according to the fourth aspect.

Through the technical scheme, the invention can obtain the following beneficial effects:

the precursor of the positive electrode material provided by the invention is different from the precursor prepared in the prior art in that the precursor is a secondary microsphere formed by agglomeration of primary particles, and the secondary microsphere comprises a three-layer structure from inside to outside, namely a core layer, a middle layer and an outermost layer. Wherein the inner core layer has a specific diffraction peak structure, and the ratio of the intensities of the (110) and (102) crystal plane diffraction peaks is 1-8, preferably 1.5-4; the specific surface area of the secondary microsphere is 0.5-15m ² /g。

According to the invention, the solid content of the precipitation reaction system is controlled to be not higher than 7wt%, preferably not higher than 5wt%, in the first 1/8R hour after the reaction starts, so that the prepared inner core layer of the positive electrode material precursor has a specific diffraction peak structure, and meanwhile, the positive electrode material precursor has a higher specific surface area, the diffraction peak structure and the high specific surface area are beneficial to the intercalation and deintercalation of lithium ions, the problem that active materials, particularly internal active materials, are difficult to utilize is effectively solved, the specific discharge capacity of the materials under different multiplying powers is improved, and the energy density and the dynamic performance of the lithium ion battery are further improved. The positive electrode material prepared by using the positive electrode material precursor is applied to a lithium ion battery, and the discharge specific capacity of the lithium ion battery is high. The embodiment shows that the first discharge specific capacity at the 0.1C multiplying power can reach 215.6mAh/g, the discharge specific capacity at the 1C multiplying power can reach 190.7mAh/g, and the high discharge specific capacity is realized at different multiplying powers. The positive electrode material precursor provided by the invention can be used in lithium ion batteries with high energy density.

Drawings

Fig. 1 is a schematic structural diagram of a positive electrode material precursor provided by the present invention;

FIG. 2 is a graph showing the concentration of the complexing agent in the reaction system of example 1 according to the present invention as a function of the reaction time;

FIG. 3 is a graph showing the concentration of the complexing agent in the reaction system of example 3 according to the present invention as a function of reaction time;

FIG. 4 is an SEM image of a positive electrode material precursor prepared according to example 1 of the present invention;

FIG. 5 is an SEM image of a cut surface of a precursor of a positive electrode material prepared in example 1 of the present invention;

FIG. 6 is an XRD pattern of the core layer of the positive electrode material precursor prepared in example 1 of the present invention;

FIG. 7 is a graph showing the charge and discharge curves of 0.1C of a lithium ion battery assembled from the positive electrode material prepared in example 1 of the present invention;

fig. 8 is a 1C charge-discharge curve of a lithium ion battery assembled from the positive electrode material prepared in example 1 of the present invention.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

The first aspect of the invention provides a positive electrode material precursor, which is a secondary microsphere formed by agglomeration of primary particles; wherein the secondary microsphere comprises an inner core layer, an intermediate layer and an outermost layer from inside to outside, wherein the ratio of the intensities of the (110) and (102) crystal plane diffraction peaks in the X-ray diffraction pattern of the inner core layer is 1-8, preferably 1.5-4, for example, 1.5, 2, 2.5, 3, 3.5, 4 and any value in the range of any two of these values, further preferably1.5-3. The specific surface area of the secondary microsphere is 0.5-15m ² Preferably 1-14m ² /g, e.g. 1m ² /g、2m ² /g、3m ² /g、4m ² /g、5m ² /g、6m ² /g、7m ² /g、8m ² /g、9m ² /g、10m ² /g、11m ² /g、12m ² /g、13m ² /g、14m ² And any value in the range formed by any two of these values.

In the invention, in order to test the X-ray diffraction pattern (XRD) of the inner core layer, the outermost layer and the intermediate layer of the positive electrode material precursor are removed first. The method for removing the outermost layer and the intermediate layer is not particularly limited, and the removal may be preferably performed by an acid washing method. A specific method of pickling is now provided, to which the present invention is not limited. The pickling process preferably comprises: 10g of positive electrode material precursor is added into 400mL of hydrochloric acid solution with the concentration of 0.4mol/L, stirred for 15min, filtered, washed with deionized water for 3 times, and dried and dehydrated in a vacuum drying oven at 120 ℃ for 6h to obtain the inner core layer product.

In the invention, the XRD spectrum of the inner core layer is measured by an X-ray diffractometer of the D8 advanced SS model of Bruce Corp. Diffraction peaks of the inner core layer at positions of 56-61 DEG and 48-54 DEG correspond to a (110) crystal plane and a (102) crystal plane respectively in an XRD spectrum of the inner core layer. (110) And the ratio of the intensities of the (102) crystal plane diffraction peaks means the ratio of the peak height of the (110) crystal plane diffraction peak to the peak height of the (102) crystal plane diffraction peak.

In the invention, the specific surface area of the precursor product is measured by a physical adsorption instrument of the model TriStar 3000 of the company Micromeritics Instrument Corporation in the United states, and the test environment is nitrogen.

The inventor of the invention discovers in the research that the inner core layer of the positive electrode material precursor has the specific diffraction peak structure and the positive electrode material precursor has the specific surface area, which is beneficial to the intercalation and deintercalation of lithium ions, effectively solves the problem that active materials, especially the interior, are difficult to utilize, improves the discharge specific capacity and the multiplying power performance of the materials, and further improves the energy density and the dynamic performance of the lithium ion battery.

In the invention, the inner core layer refers to a first section area extending from the center of the secondary microsphere to the outer surface, the middle layer refers to a second section area wrapping the inner core layer and extending from the outer surface of the inner core layer to the outer surface of the secondary microsphere, the outermost layer refers to a third section area wrapping the middle layer and extending from the outer surface of the middle layer to the outer surface of the secondary microsphere, and the specific structure schematic diagram is shown in figure 1.

In a preferred embodiment of the present invention, the relationship of the degree of densification of the inner core layer, the intermediate layer and the outermost layer is: the middle layer > the core layer > the outermost layer.

In a preferred embodiment of the present invention, the thickness of the inner core layer is 0.1 to 50%, the thickness of the intermediate layer is 40 to 95%, and the thickness of the outermost layer is 0.1 to 20% based on 100% of the radius of the secondary microsphere.

In a preferred embodiment of the present invention, the primary particles have a shape selected from at least one of a sheet, a plate, a needle, and a spindle.

In the invention, the morphology of the positive electrode material precursor is characterized by a Scanning Electron Microscope (SEM), and the model of the adopted scanning electron microscope is ZEISS Merlin (ZEISS company, germany). The SEM images (fig. 4 and 5) of the positive electrode material precursor can observe that the positive electrode material precursor provided by the invention is spherical particles, and the spherical particles are formed by agglomerating primary flaky bodies and comprise a three-layer structure from inside to outside, namely an inner core layer, an intermediate layer and an outermost layer.

Further, the densification of the agglomeration of the inner core layer, the intermediate layer and the outermost layer can also be observed by SEM images of the positive electrode material precursor (see fig. 4, 5), and the thicknesses of the inner core layer, the intermediate layer and the outermost layer can be measured. Specifically, from SEM images of the positive electrode material precursor (fig. 4 and 5), it can be observed that the core layer is formed by one-time sheet-like agglomeration, the core layer is relatively loose in sheet-like agglomeration, the thickness of the core layer is about 1.4 μm, the outermost layer is also formed by one-time sheet-like agglomeration, the outermost layer is more loose than the core layer, the thickness of the outermost layer is about 0.33 μm, the intermediate layer between the core layer and the outermost layer is very dense, and the thickness of the intermediate layer is about 4.6 μm.

The inventor of the invention discovers in the research that the inner core layer has lower density, can further reduce the resistance of lithium ions in the inner core layer to be inserted and extracted, can effectively release and buffer the volume change of the active substance in the charging and discharging process, and can inhibit the cracking and breaking problems of the active substance caused by volume expansion and contraction in the charging and discharging process. The intermediate layer has the highest density, can effectively wrap a core layer structure with high activity, improves the circulation stability of the material, and can effectively improve the volume energy density of the active material. The outermost layer has the lowest density, can quickly embed external lithium ions into a material body phase, effectively reduces the interface resistance of the material, and can improve the rate capability of the active material.

In a preferred embodiment of the present invention, the secondary microspheres have a particle size of 1 to 30. Mu.m, preferably 1 to 20. Mu.m, more preferably 1 to 15. Mu.m.

In the invention, the particle size of the secondary microsphere is the medium particle size D50 of the secondary microsphere, which is measured by a dynamic light scattering technology, and specifically, the secondary microsphere is obtained by a Mastersizer3000 laser particle sizer of the company Malvern Panalytical in the United kingdom.

In a preferred embodiment of the present invention, the positive electrode material precursor has a chemical formula of Ni _x Co _y M _z T _p (OH) _2-q The method comprises the steps of carrying out a first treatment on the surface of the Wherein M is selected from at least one of Cu, nd, mg, W, mo, zn, sn, sr, mn and Al, preferably at least one of Mn, al, sr, nd and Mg; t is selected from at least one of N, P, S; x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, p is more than or equal to 0 and less than or equal to 0.5, preferably, x is more than or equal to 0.5, y is more than or equal to 0 and less than or equal to 0.5, p is more than or equal to 0 and less than or equal to 0.3, wherein at least one of the values of x, y and z is not 0, and the value range of q is determined according to the electric neutral principle.

wherein the total reaction time is expressed as R hours, and the solid content of the precipitation reaction system is not more than 7wt%, preferably not more than 5wt%, for example, 0wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% and any value in the range constituted by any two of these values in the first 1/8R hours at the start of the reaction.

Through intensive researches on the precipitation reaction process, the inventor discovers that the solid content of the precipitation reaction system is controlled within the range of 1/8R hours before the reaction starts, secondary microsphere precursor particles formed by aggregation of primary particles are creatively obtained, the aggregation form of the primary particles is loose due to aggregation of a core layer, the aggregation form of a middle layer is dense, the aggregation of an outermost layer is loose due to aggregation of the middle layer, the core layer can be controlled to present a specific diffraction peak structure and the higher specific surface area of the secondary microspheres, and the positive electrode material precursor material with the characteristics has higher specific discharge capacity and can be used in lithium ion batteries with high energy density.

In a preferred embodiment of the present invention, the precipitation reaction comprises: and simultaneously adding the metal source solution, the precipitant solution and the complexing agent solution into a reaction kettle under the stirring state for reaction.

In a preferred embodiment of the invention, the metal source is selected from at least one of a nickel source, a cobalt source and a M source, M being selected from at least one of Cu, nd, mg, W, mo, zn, sn, sr, mn and Al, preferably Nd, mg, sr, mn and Al.

In the present invention, the kind of the nickel source is not particularly limited, and preferably the nickel source is selected from at least one of sulfate, nitrate, acetate, oxalate and hydrochloride of nickel, and more preferably the nickel source is selected from at least one of nickel sulfate, nickel nitrate, nickel acetate, nickel oxalate and nickel chloride.

In the present invention, the kind of the cobalt source is not particularly limited, and preferably the cobalt source is selected from at least one of sulfate, nitrate, acetate, oxalate and hydrochloride of cobalt, and more preferably the cobalt source is selected from at least one of cobalt sulfate, cobalt nitrate, cobalt acetate and cobalt chloride.

In the present invention, the kind of the M source is not particularly limited, and preferably the M source is selected from at least one of sulfate, nitrate, acetate, oxalate and hydrochloride of M, and more preferably at least one of manganese sulfate, manganese nitrate, manganese acetate, manganese chloride, aluminum nitrate, aluminum chloride, aluminum acetate, aluminum sulfate, zinc sulfate, magnesium sulfate and titanium sulfate.

In a preferred embodiment of the present invention, the molar concentration of the metal source solution is 0.01 to 5mol/L, preferably 0.01 to 4mol/L, more preferably 0.5 to 4mol/L, in terms of metal element.

In a preferred embodiment of the present invention, the precipitation reaction further comprises: and adding a T source into the metal source solution, wherein T is at least one selected from N, P, S.

In a preferred embodiment of the present invention, the molar ratio of the nickel source, cobalt source, M source and T source in terms of metal element in the metal source solution is (0-1): (0-1): (0-0.5), preferably (0.5-0.95): (0-0.5): (0-0.3), wherein at least one of the molar amounts of the nickel source, cobalt source and M source is not 0.

In the present invention, the kind of the precipitant is not particularly limited as long as the metal source is capable of performing a precipitation reaction, and preferably the precipitant is selected from at least one of hydroxide, carbonate and bicarbonate of an alkali metal, and preferably the alkali metal is selected from at least one of Na, K and Li; more preferably, the precipitant is selected from at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, lithium hydroxide, lithium carbonate, and lithium bicarbonate. The embodiment of the invention is exemplified by sodium hydroxide, and the invention is not limited thereto.

In the present invention, the concentration of the precipitant solution is not particularly limited, and preferably the concentration of the precipitant solution is 0.01 to 16mol/L, preferably 2 to 12mol/L.

In the present invention, the kind of the complexing agent is not particularly limited as long as it can form a complex with Ni, co and M in an aqueous solution; preferably, the complexing agent is selected from at least one of an ammonium ion donor, an alcohol amine complexing agent, an aminocarboxylic acid complexing agent, a hydroxyamino carboxylic acid complexing agent, a carboxylate complexing agent, and a thiocyanate complexing agent.

In a preferred embodiment of the present invention, the ammonium ion donor is selected from at least one of ammonia water, ammonium oxalate, ammonium carbonate and ammonium hydroxide. The embodiment of the invention is exemplified by ammonia water, and the invention is not limited thereto.

In a preferred embodiment of the present invention, the alcohol amine complexing agent is selected from at least one of ethanolamine, diethanolamine, 2-dibutylamino ethanol, 2-diethylaminoethanol and N, N-diethylethanolamine.

In a preferred embodiment of the present invention, the aminocarboxylic acid complexing agent is selected from at least one of sodium Nitrilotriacetate (NTA), potassium nitrilotriacetate, ethylenediamine tetraacetic acid and its salts (EDTA) and diethylenetriamine pentaacetic acid (DTPA).

In a preferred embodiment of the present invention, the hydroxyaminocarboxylic acid-based complexing agent is selected from at least one of hydroxyethylenediamine tetraacetic acid (HEDTA) and salts thereof, ethyleneglycol bis (β -diaminoethyl) diethyl ether-N, N, N 'N' -tetraacetic acid (EGTA) and salts thereof, and dihydroxyglycine and salts thereof.

In a preferred embodiment of the present invention, the carboxylate-based complexing agent is selected from at least one of oxalic acid and salts thereof, tartaric acid and salts thereof, citric acid and salts thereof, gluconic acid and salts thereof, carboxymethyl hydroxy malonic acid (CMOM) and salts thereof, carboxymethyl hydroxy succinic acid (CMOS) and salts thereof, and hydroxyethyl amino acetic acid (DHEG) and salts thereof.

In a preferred embodiment of the present invention, the thiocyanate-based complexing agent is at least one selected from the group consisting of sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, calcium thiocyanate, and zinc thiocyanate.

In the present invention, the concentration of the complexing agent solution is not particularly limited, and preferably the concentration of the complexing agent solution is 0.01 to 16mol/L, preferably 2 to 15mol/L.

In a preferred embodiment of the present invention, the base solution is added to the reaction vessel prior to adding the metal source solution, the precipitant solution and the complexing agent solution to the reaction vessel.

In a preferred embodiment of the invention, the base solution is an aqueous solution comprising a complexing agent; the volume of the base liquid is 0-100%, preferably 0-80%, and more preferably 10-60% of the volume of the reaction kettle. The concentration of the complexing agent in the base liquid is 0 to 1.8mol/L, preferably 0.05 to 1.5mol/L, and more preferably 0.1 to 1.0mol/L.

In a preferred embodiment of the invention, the concentration of complexing agent in the base liquid is at least 0.05mol/L, preferably at least 0.1mol/L lower than the concentration of complexing agent at the end of the reaction.

In a preferred embodiment of the present invention, the concentration of the complexing agent in the precipitation reaction system gradually increases, and the concentration change rate of the complexing agent gradually decreases; the concentration change rate of the complexing agent is 1 mol/L.multidot.h or less, preferably 0.001 to 1 mol/L.multidot.h, and more preferably 0.001 to 0.5 mol/L.multidot.h.

In a preferred embodiment of the present invention, the total reaction time is defined as R hours, and the concentration change rate of the complexing agent is not less than 0.021 mol/L.h, preferably 0.021 to 1 mol/L.h, more preferably 0.021 to 0.5 mol/L.h, for example, any value in the range of any two of these values, 0.021 mol/L.h, 0.026 mol/L.h, 0.031 mol/L.h, 0.036 mol/L.h, 0.041 mol/L.h, 0.046 mol/L.h, 0.5, in the first 1/8R hours after the start of the reaction. By adopting the preferable scheme, the discharge capacity, the rate capability and the cycle stability of the prepared positive electrode material precursor can be obviously improved.

In the present invention, the "concentration change rate of the complexing agent" refers to the difference between the final concentration and the initial concentration of the complexing agent in the reaction system in any time period, and the present invention is calculated in each hour. The term "the concentration change rate of the complexing agent in the precipitation reaction system gradually decreases" means that the concentration change rate of the complexing agent in the reaction system (as a whole) shows a tendency to gradually decrease in the whole period of time from the time when the complexing agent is added to the precipitation reaction system to the end of the reaction, but allows one or more local sections to exist; within this local interval, the concentration of complexing agent in the reaction system changes in a different manner (e.g., maintains a constant and/or gradually increasing and/or disordered state). Provided that the presence of such local intervals is unavoidable to the state of the art and does not affect the person skilled in the art in determining the rate of change of the concentration of the complexing agent in the reaction system over said whole period of time as still (overall) exhibiting a gradual decreasing trend. In addition, the presence of such local intervals does not affect the achievement of the intended purpose of the present invention, is acceptable and is also included in the scope of the present invention.

In a preferred embodiment of the present invention, the time from the addition of the complexing agent to the completion of the reaction to the concentration of 80% or more of the complexing agent in the precipitation reaction system is not more than 1/4R hours.

In a preferred embodiment of the invention, the concentration of the complexing agent at the end of the reaction is from 0.05 to 2mol/L, preferably from 0.05 to 1.2mol/L.

In the present invention, in order to promote the sufficient progress of the reaction of the metal source solution, the precipitant solution and the complexing agent solution, the conditions of the precipitation reaction include: the temperature is 20-70deg.C, preferably 45-60deg.C; the pH value is 8-14, preferably 10-12; the reaction time is not less than 10 hours, preferably 12 to 96 hours, more preferably 12 to 48 hours; the precipitation reaction is carried out under stirring conditions at a stirring speed of 50-1200r/min, preferably 600-1200r/min.

It should be understood that the control of the pH may be to control a constant pH during the reaction time, or to vary the pH of the reaction process depending on the product object, but the range of pH variation should be within the above-mentioned reaction system, and in a further preferred embodiment, the pH of the reaction system is kept constant within the above-mentioned range.

In the invention, the solid content of the precipitation reaction system is related to the addition amount of the metal source solution, the complexing agent solution and the precipitant solution, and the addition amount is related to the flow rate and the concentration of each material, so that the solid content of the precipitation reaction system can be regulated and controlled by a person skilled in the art by controlling the flow rate and the concentration of the metal source solution, the complexing agent solution and the precipitant solution.

The invention has wide selection range of the flow rate and the concentration of the metal source solution, the complexing agent solution and the precipitant solution, and the flow rate and the concentration of each material can be controlled by a person skilled in the art according to the requirements. In some preferred embodiments, in the case that the concentrations of the metal source solution, the complexing agent solution and the precipitant solution are determined, the ratio of the initial volumetric flow rates of the metal source and the complexing agent is preferably set to be 1-10, more preferably 2-6, and then the flow rate of the metal source solution is kept unchanged, the concentration of the complexing agent in the precipitation reaction system and the change rate thereof are controlled to be within the above-defined range by controlling the flow rate of the complexing agent solution, and the pH of the precipitation reaction system is controlled to satisfy the above-described range, thereby achieving the regulation of the solid content of the precipitation reaction system.

In the present invention, the solid-liquid separation in the step (2) is not particularly limited as long as the reaction product obtained after the precipitation reaction can be separated, and for example, filtration or centrifugation can be used.

In the present invention, it is preferable that the product obtained by the solid-liquid separation is subjected to a washing treatment, and the washing solvent is preferably water, more preferably hot water, at a temperature of 30 to 90 ℃.

In the present invention, the drying method may be a method conventional in the art, and for example, may be vacuum drying, freeze drying, air drying, or oven drying. The present invention is preferably vacuum heat drying, and the drying temperature and time are not particularly required as long as the washed product can be dried, for example: the vacuum heating and drying temperature is 50-150 ℃ and the time is 4-24h.

In a third aspect, the present invention provides a positive electrode material precursor prepared by the method described in the second aspect. The properties of the positive electrode material precursor have been described in detail in the first aspect, and the description thereof will not be repeated.

In a preferred embodiment of the present invention, the positive electrode material is obtained by mixing a positive electrode material precursor and a lithium source and performing a sintering process.

In the present invention, the mixing method of the positive electrode material precursor and the lithium source is not particularly limited as long as the mixing uniformity can be ensured. Preferably, the mixing can be achieved by a high-speed mixer, ball milling and the like. The mixed materials are sintered in an atmosphere furnace, wherein the sintering atmosphere can be at least one of air, oxygen and inert atmosphere such as nitrogen.

In a preferred embodiment of the invention, the molar ratio of the lithium source to the battery positive electrode material precursor is 0.9-1.3:1, for example 0.9, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.30, and any value in the range consisting of any two of these values, calculated as metal element.

In the present invention, the lithium source may be present in the form of a lithium salt, preferably selected from lithium nitrate (LiNO) ₃ ) Lithium chloride (LiCl), lithium carbonate (Li) ₂ CO ₃ ) Lithium hydroxide (LiOH), lithium oxide (Li) ₂ O), lithium phosphate (Li) ₃ PO ₄ ) Lithium dihydrogen phosphate (LiH) ₂ PO ₄ ) And lithium acetate (CH) ₃ COOLi).

A fifth aspect of the present invention provides a lithium ion battery comprising the positive electrode material according to the fourth aspect. The inventor of the invention discovers in research that the positive electrode material provided by the invention is used in a lithium ion battery, and can improve the discharge specific capacity of the lithium ion battery.

The structure of the lithium ion battery provided by the invention can be known to those skilled in the art, and generally, the lithium ion battery comprises a positive electrode, a negative electrode, an electrolyte and a diaphragm; the positive electrode and the negative electrode may be prepared by coating and drying a composite for forming a positive electrode-containing material and a composite for forming a negative electrode-containing material on respective current collectors.

In the present invention, the positive electrode composite may be prepared by a positive electrode material, a conductive agent, a binder, and a solvent.

In the present invention, the conductive agent used in the positive electrode composite is not particularly limited as long as it has conductivity and remains stable in the charge-discharge range. Preferably, the conductive agent is at least one selected from acetylene black, ketjen black, artificial graphite, natural graphite, carbon tube, graphene, superconducting carbon, carbon nanofiber, carbon dot, aluminum powder, nickel powder, titanium oxide, and conductive polymer.

In the present invention, the binder used in the positive electrode composite is not particularly limited as long as it provides adhesion of the positive electrode material, the conductive agent, and the current collector. Preferably, the binder is selected from at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), aqueous acrylic resin, polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoroethylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic resin.

In the present invention, the positive electrode current collector is not particularly limited as long as it has appropriate conductivity. Preferably, the material of the positive electrode current collector may be aluminum, nickel, copper, titanium, silver, stainless steel or carbon material, and the positive electrode current collector may be processed into various forms such as foil, sheet, film, net, hole, non-woven fabric, etc.

In a preferred embodiment of the present invention, the solvent used in the positive electrode composite may be N-methylpyrrolidone.

In the present invention, the anode composite may be prepared by an anode material, a conductive agent, a binder, and a solvent.

In the present invention, the kind of the negative electrode material is not particularly limited, and one skilled in the art can select according to actual requirements. Preferably, the negative electrode material is selected from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microspheres (MCMB), carbon fiber, lithium metal, silicon oxide, lithium metal alloy, and lithium titanate.

In the present invention, the conductive agent and the binder used in the negative electrode composite are not particularly limited, and preferably, the conductive agent and the binder used in the negative electrode composite may be of the same type and content as those used in the preparation of the positive electrode composite.

In a preferred embodiment of the present invention, the solvent used in the negative electrode composite may be water.

In the present invention, the negative electrode current collector is not particularly limited as long as it has appropriate conductivity. Preferably, the material of the negative electrode current collector may be aluminum, nickel, copper, titanium, silver, stainless steel or carbon material, and the negative electrode current collector may be processed into various forms such as foil, sheet, film, net, hole, non-woven fabric, etc.

In the present invention, the electrolyte may be a solid electrolyte such as a polymer electrolyte, an inorganic solid electrolyte, or the like; or may be a liquid electrolyte containing a lithium salt and a solvent.

In a preferred embodiment of the present invention, the polymer electrolyte is selected from at least one of polyvinyl alcohol, phosphate polymer, polyvinylidene fluoride, polyoxyethylene derivative, polyoxypropylene derivative, polyethylene derivative and polyester sulfide.

In a preferred embodiment of the present invention, the inorganic solid electrolyte is selected from Li ₂ S、Li ₂ S-P ₂ S ₅ 、LiI、Li-La-Zr-O、Li-Ge-V-O、Li ₃ N、Li ₄ SiO ₄ 、LiPON、LISION、Li-Al-Ti-P、Li ₃ PO ₄ -Li ₂ S-SiS ₂ 、LiBH ₄ 、LiBH ₄ -LiX (x=cl, br or I), liBH ₄ -LiNH ₂ 、LiNH ₂ 、Li ₃ AlH ₆ 、Li ₂ NH and Li ₂ O-B ₂ O ₃ -P ₂ O ₅ At least one of them.

In the present invention, the liquid electrolyte is a solution of a lithium salt in a solvent, which may be a nonaqueous solvent, preferably at least one selected from the group consisting of Ethylene Carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), propylene Carbonate (PC), ethylene Propylene Carbonate (EPC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), methyl Formate (MF), ethyl formate (Eft), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), and propyl Butyrate (BP).

In a preferred embodiment of the present invention, the lithium salt is selected from lithium hexafluorophosphate (LiPF) ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium perchlorate (LiClO) ₄ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium bis (fluorosulfonyl) imide (LiLSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium (LiTFS) triflate, lithium (LiDFOB) difluoro (oxalato) borate, lithium bis (oxalato) borate, lithium (LiPO) ₂ F ₂ ) At least one of lithium difluorooxalato phosphate (LiDFOP) and lithium tetrafluorooxalato borate (LiTFOP).

In the invention, in order to improve the performance of the lithium ion battery, additives can be optionally added into the electrolyte. The additive is preferably at least one selected from the group consisting of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), tris (trimethylsilane) phosphate (TMSP), sulfonate cyclic quaternary ammonium salt, ethylene sulfite (DTO), dimethyl sulfite (DMS), 1-propylene-1, 3-sultone (PST), 4-propylethylene sulfate (PEGLST), diethyl sulfite (DES), adiponitrile (ADN), succinonitrile (SN), 1, 3-propane sultone (1, 3-PS), vinyl sulfate (DTD) and 4-methyl ethylene sulfate (PCS).

In the invention, the diaphragm is arranged between the anode and the cathode to isolate the anode from the cathode. The separator may be various separators conventionally used in the art, and preferably, the separator may be polyolefin such as polyethylene, polypropylene, a composite of polyethylene and polypropylene, a sheet formed of glass fiber, nonwoven fabric, or the like. When a solid electrolyte is used, the solid electrolyte may also be used as a separator.

The preparation method of the lithium ion battery is not particularly limited, and can be prepared by adopting a method conventional in the art. Preferably, the preparation method of the lithium ion battery comprises the following steps: uniformly mixing a positive electrode material, a conductive agent, a binder and a solvent, coating on at least one surface of a positive electrode current collector, drying, rolling and slicing to obtain a positive electrode; uniformly mixing a negative electrode material, a conductive agent, a binder and a solvent, coating on at least one surface of a negative electrode current collector, drying, rolling and slicing to obtain a negative electrode; and assembling the positive electrode, the diaphragm and the negative electrode into a laminated or coiled battery cell, placing the battery cell in a shell, injecting electrolyte, and packaging to obtain the lithium ion battery.

In the present invention, the amounts of the positive and negative electrode materials, the conductive agent and the binder are not particularly limited, and preferably, the mass content of the positive electrode material or the negative electrode material is 50 to 99wt%, the mass content of the conductive agent is 0.5 to 25wt%, and the mass content of the binder is 0.5 to 25wt%, based on the solid content of the positive electrode or the negative electrode composite.

The present invention will be described in detail by examples. In the following examples and comparative examples,

Scanning Electron Microscopy (SEM) was obtained by scanning electron microscopy of the ZEISS Merlin model of ZEISS company, ZEISS, germany;

x-ray diffraction pattern (XRD) was measured by an X-ray diffractometer model D8 Advance SS, bruck, germany;

the specific surface area results were measured by a physical adsorption instrument model trisar 3000, company Micromeritics Instrument Corporation, usa;

the medium particle size was obtained by a Mastersizer 3000 laser particle sizer, company Malvern Panalytical, uk.

In the following examples and comparative examples, all the materials involved are commercially available unless otherwise specified.

Example 1

The embodiment is used for explaining the preparation and evaluation methods of the positive electrode material precursor and the positive electrode material.

(1) Preparation of positive electrode material precursor

Preparing a metal source solution with the concentration of 3mol/L by taking metal elements as a reference, wherein the molar ratio of nickel, cobalt and manganese elements in the metal source solution is 8:1:1, and nickel sulfate, cobalt sulfate and manganese sulfate are used in the preparation process; preparing NaOH solution with the concentration of 5 mol/L; preparing complexing agent ammonia water solution, wherein the concentration of ammonia water is 5mol/L.

The prepared metal source solution, naOH solution and complexing agent solution are added into a reaction kettle at the same time under the stirring state to carry out precipitation reaction, and ammonia water solution accounting for 30 percent of the volume of the kettle is added into the reaction kettle in advance, wherein the concentration of the ammonia water is 0.5mol/L. The ratio of the initial volume flow rate of the metal source solution to the complexing agent solution is controlled to be 3, then the flow rate of the metal source solution is kept unchanged, and the feeding flow rate of the complexing agent is controlled, so that the concentration of the complexing agent in the system is gradually increased, the increasing rate of the concentration of the complexing agent is gradually reduced, and the change of the concentration of the complexing agent in the system along with the reaction time is shown in figure 2. The flow rate of the NaOH solution was controlled so that the pH of the reaction system was maintained around 11.6 throughout the reaction. Wherein the solid content of the reaction system in the 6 th hour is 4.5wt%, the concentration of ammonia water in the system is about 1.13mol/L at the end of the reaction, the stirring speed in the reaction process is 800rpm, the reaction temperature is 55 ℃, and the total reaction time is 48 hours. And (3) after the precipitation reaction is ended, naturally cooling, carrying out vacuum suction filtration on the slurry, washing with deionized water for 3 times, and drying and dehydrating in a vacuum drying oven at 120 ℃ for 12 hours to obtain a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

SEM characterization was performed on the positive electrode material precursor prepared as described above, as shown in fig. 4. As can be seen from fig. 4, the preparation method provided by the invention can obtain a positive electrode material precursor with good sphericity, and the positive electrode material precursor is a secondary microsphere formed by agglomerating primary flakes.

In order to further analyze the agglomeration form of the primary sheet body, the precursor of the positive electrode material is subjected to ion beam cutting and then subjected to SEM characterization, and an SEM image of a section of the precursor of the positive electrode material is shown in FIG. 5, and as can be seen from FIG. 5, the precursor of the positive electrode material obtained by the preparation method provided by the invention comprises three layers of structures from inside to outside, namely an inner core layer, an intermediate layer and an outermost layer. The inner core layer is formed by one-time flaky agglomeration, the flaky agglomeration of the inner core layer is relatively loose, the thickness of the inner core layer is about 1.4 mu m, the outermost layer is also formed by flaky agglomeration, the agglomeration of the outermost layer is more loose than that of the inner core layer, the thickness of the outermost layer is about 0.33 mu m, the agglomeration of the intermediate layer between the inner core layer and the outermost layer is very compact, and the thickness of the intermediate layer is about 4.6 mu m.

The intermediate particle size of the positive electrode material precursor prepared in example 1 was tested, and it was shown that the intermediate particle size D50 of the positive electrode material precursor secondary microspheres was 12.4 μm.

The specific surface area of the positive electrode material precursor prepared in example 1 was tested, showing that the specific surface area of the positive electrode material precursor secondary microsphere was 8.53m ² /g。

10g of the prepared positive electrode material precursor is added into 400mL of hydrochloric acid solution with the concentration of 0.4mol/L, stirred for 15min, filtered, washed with deionized water for 3 times, and dried and dehydrated in a vacuum drying oven at 120 ℃ for 6h to obtain a core layer product. The XRD spectrum of the core layer was tested, and as a result, as shown in FIG. 6, it can be seen from FIG. 6 that the ratio of the intensities of the (110) and (102) crystal plane diffraction peaks in the XRD spectrum of the core layer was 2.93.

(3) Preparation and evaluation of cathode Material

Taking the prepared positive electrode material precursor and lithium source LiOH-H ₂ O ball milling is carried out for 30min, the molar ratio of Li (Ni+Co+Mn) is controlled to be 1.05:1, presintering is carried out for 4h at 500 ℃ in oxygen atmosphere, and then solid phase reaction is carried out for 12h at 900 ℃ to obtain the anode material.

Uniformly mixing the prepared anode material, a conductive agent and a binder according to a mass ratio of 90:5:5, coating the mixture on an aluminum foil, drying a solvent, slicing the dried solvent to obtain an anode, wherein the conductive agent is acetylene black, and the binder is polyvinylidene fluoride solution with a mass fraction of 10%; the negative electrode uses lithium metal, the diaphragm uses Celllgard2400 polypropylene diaphragm in the United states, the electrolyte uses liquid electrolyte, the solvent is a mixed solvent of Ethylene Carbonate (EC) and dimethyl carbonate (DMC), the volume ratio of the two is 1:1, and the solute is hexafluorophosphoric acid Lithium LiPF ₆ The molar concentration was 1mol/L. The 2025 type button cell was assembled in an inert atmosphere glove box with moisture and oxygen contents below 0.1ppm.

The electrochemical performance of the positive electrode material was measured under the conditions of a charge-discharge voltage range of 2.5 to 4.3V and an ambient temperature of 25 ℃. The result shows that the initial discharge specific capacity of the 0.1C multiplying power is 215.6mAh/g, and the discharge specific capacity of the 1C multiplying power can also reach 190.7mAh/g, and specific charge and discharge curves are shown in fig. 7 and 8. The discharge specific capacity of different multiplying powers is high.

Example 2

(1) Preparation of positive electrode material precursor

Preparing a metal source solution with the concentration of 2mol/L by taking metal elements as a reference, wherein the molar ratio of nickel, cobalt and aluminum elements in the metal source solution is 8:1.5:0.5, and nickel sulfate, cobalt sulfate and aluminum sulfate are used in the preparation process; preparing NaOH solution with the concentration of 5 mol/L; preparing complexing agent ammonia water solution, wherein the concentration of ammonia water is 4mol/L.

The prepared metal source solution, naOH solution and complexing agent solution are added into a reaction kettle at the same time under the stirring state to carry out precipitation reaction, and ammonia water solution accounting for 30 percent of the volume of the kettle is added into the reaction kettle in advance, wherein the concentration of the ammonia water is 0.5mol/L. The ratio of the initial volumetric flow rates of the metal source solution and the complexing agent solution was controlled to be 4, then the flow rate of the metal source solution was kept unchanged, and the feed flow rate of the complexing agent was controlled so that the concentration of the complexing agent in the system was gradually increased, and the rate of increase in the concentration of the complexing agent was gradually decreased, as in example 1, the concentration of the complexing agent in the system was changed with the reaction time. The flow rate of the NaOH solution was controlled so that the pH of the reaction system was maintained around 11.4 throughout the reaction. Wherein the solid content of the reaction system at the 6 th hour is 4.1wt%, the concentration of ammonia water in the system is about 1.13mol/L at the end of the reaction, the stirring speed in the reaction process is 1000rpm, the reaction temperature is 50 ℃, and the total reaction time is 48 hours. And (3) after the precipitation reaction is ended, naturally cooling, carrying out vacuum suction filtration on the slurry, washing with deionized water for 3 times, and drying and dehydrating in a vacuum drying oven at 120 ℃ for 12 hours to obtain a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

SEM testing was performed on the prepared positive electrode material precursor, and SEM images were similar to those of fig. 4 and 5.

The prepared positive electrode material precursor is subjected to specific surface area test, and the specific surface area of the secondary microsphere is 10.87m ² /g。

XRD testing of the core layer of the prepared positive electrode material precursor was conducted in accordance with the method of example 1, and the result showed that the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.79.

(3) Preparation and evaluation of cathode Material

Positive electrode materials and lithium ion batteries were prepared as described in example 1.

The electrochemical performance of the positive electrode material is measured under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, and the result shows that the initial discharge specific capacity at the 0.1C multiplying power is 215.1mAh/g and the discharge specific capacity at the 1C multiplying power is 190.2mAh/g.

Example 3

(1) Preparation of positive electrode material precursor

Preparing a metal source solution with the concentration of 3mol/L by taking metal elements as a reference, wherein the molar ratio of nickel, cobalt and manganese elements in the metal source solution is 8:1:1, and nickel sulfate, cobalt sulfate and manganese sulfate are used in the preparation process; preparing NaOH solution with the concentration of 8 mol/L; preparing complexing agent ammonia water solution, wherein the concentration of ammonia water is 8mol/L.

The prepared metal source solution, naOH solution and complexing agent solution are added into a reaction kettle at the same time under the stirring state to carry out precipitation reaction, and ammonia water solution accounting for 30 percent of the volume of the kettle is added into the reaction kettle in advance, wherein the concentration of the ammonia water is 0.5mol/L. The ratio of the initial volume flow rate of the metal source solution to the complexing agent solution is controlled to be 6, then the flow rate of the metal source solution is kept unchanged, and the feeding flow rate of the complexing agent is controlled, so that the concentration of the complexing agent in the system is gradually increased, the increasing rate of the concentration of the complexing agent is gradually reduced, and the change of the concentration of the complexing agent in the system along with the reaction time is shown in figure 3. The flow rate of the NaOH solution was controlled so that the pH of the reaction system was maintained around 11 throughout the reaction. Wherein the solid content of the reaction system in the 6 th hour is 6.9wt%, the concentration of ammonia water in the system is about 1.06mol/L at the end of the reaction, the stirring speed in the reaction process is 800rpm, the reaction temperature is 55 ℃, and the total reaction time is 48 hours. And (3) after the precipitation reaction is ended, naturally cooling, carrying out vacuum suction filtration on the slurry, washing with deionized water for 3 times, and drying and dehydrating in a vacuum drying oven at 120 ℃ for 12 hours to obtain a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

The prepared positive electrode material precursor is subjected to specific surface area test, and the specific surface area of the secondary microsphere is 3.53m ² /g。

XRD testing of the core layer of the prepared positive electrode material precursor was conducted in accordance with the method of example 1, and the result showed that the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes in the XRD spectrum of the core layer was 1.87.

(3) Preparation and evaluation of cathode Material

The electrochemical performance of the positive electrode material is measured under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, and the result shows that the initial discharge specific capacity at 0.1C rate is 210.6mAh/g and the discharge specific capacity at 1C rate is 186.8mAh/g.

Example 4

(1) Preparation of positive electrode material precursor

The operation was performed as described in example 1, except that neodymium nitrate was added to the metal source solution, wherein Nd/(ni+co+mn) =1%mol, to obtain a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

The prepared positive electrode material precursor is subjected to specific surface area test, and the specific surface area of the secondary microsphere is 6.67m ² /g。

XRD testing of the core layer of the prepared positive electrode material precursor was conducted in accordance with the method of example 1, and the result showed that the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.64.

(3) Preparation and evaluation of cathode Material

The electrochemical performance of the positive electrode material is measured under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, and the result shows that the initial discharge specific capacity at 0.1C rate is 214.5mAh/g and the discharge specific capacity at 1C rate is 189.5mAh/g.

Example 5

(1) Preparation of positive electrode material precursor

The procedure is as described in example 1, except that MgSO is added to the metal source solution ₄ ·7H ₂ O, wherein Mg/(ni+co+mn) =1%mol, gives a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

The prepared positive electrode material precursor is subjected to specific surface area test, and the specific surface area of the secondary microsphere is 5.19m ² /g。

XRD testing of the core layer of the prepared positive electrode material precursor was conducted in accordance with the method of example 1, and the result showed that the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.59.

(3) Preparation and evaluation of cathode Material

The electrochemical performance of the positive electrode material is measured under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, and the result shows that the initial discharge specific capacity at 0.1C rate is 214.2mAh/g and the discharge specific capacity at 1C rate is 188.9mAh/g.

Example 6

(1) Preparation of positive electrode material precursor

The procedure is as described in example 1, except that H is added to the metal source solution ₃ PO ₄ Wherein P/(ni+co+mn) =1%mol, a positive electrode material precursor is obtained.

(2) Evaluation of the precursor of the cathode Material

The prepared positive electrode material precursor is subjected to specific surface area test, and the specific surface area of the secondary microsphere is 1.37m ² /g。

XRD testing of the core layer of the prepared positive electrode material precursor was conducted in accordance with the method of example 1, and the result showed that the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.24.

(3) Preparation and evaluation of cathode Material

The electrochemical performance of the positive electrode material is measured under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, and the result shows that the initial discharge specific capacity at 0.1C rate is 209.7mAh/g and the discharge specific capacity at 1C rate is 185.4mAh/g.

Example 7

(1) Preparation of positive electrode material precursor

Preparing a metal source solution with the concentration of 0.5mol/L by taking metal elements as a reference, wherein the molar ratio of nickel, cobalt and manganese elements in the metal source solution is 8:1:1, and nickel sulfate, cobalt sulfate and manganese sulfate are used in the preparation process; preparing NaOH solution with the concentration of 10 mol/L; preparing complexing agent ammonia water solution, wherein the concentration of ammonia water is 2mol/L.

The prepared metal source solution, naOH solution and complexing agent solution are added into a reaction kettle at the same time under the stirring state to carry out precipitation reaction, and ammonia water solution accounting for 40 percent of the volume of the kettle is added into the reaction kettle in advance, wherein the concentration of the ammonia water is 0.5mol/L. The ratio of the initial volumetric flow rates of the metal source solution and the complexing agent solution was controlled to be 5, then the flow rate of the metal source solution was kept unchanged, and the feed flow rate of the complexing agent was controlled so that the concentration of the complexing agent in the system was gradually increased, and the rate of increase in the concentration of the complexing agent was gradually decreased, as in example 1, the concentration of the complexing agent in the system was changed with the reaction time. The flow rate of the NaOH solution was controlled so that the pH of the reaction system was maintained around 10 throughout the reaction. Wherein the solid content of the reaction system in the 6 th hour is 3wt%, the concentration of ammonia water in the system is about 1.13mol/L at the end of the reaction, the stirring speed in the reaction process is 1000rpm, the reaction temperature is 50 ℃, and the total reaction time is 48 hours. And (3) after the precipitation reaction is ended, naturally cooling, carrying out vacuum suction filtration on the slurry, washing with deionized water for 3 times, and drying and dehydrating in a vacuum drying oven at 120 ℃ for 12 hours to obtain a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

The prepared positive electrode material precursor is subjected to specific surface area test, and the specific surface area of the secondary microsphere is 13.85m ² /g。

XRD testing of the core layer of the prepared positive electrode material precursor was performed in accordance with the method of example 1, and the result showed that the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes in the XRD spectrum of the core layer was 1.74.

(3) Preparation and evaluation of cathode Material

The electrochemical performance of the positive electrode material is measured under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, and the result shows that the initial discharge specific capacity at the 0.1C multiplying power is 210.8mAh/g and the discharge specific capacity at the 1C multiplying power is 186.9mAh/g.

According to the results, the novel positive electrode material precursor is prepared by the method, the positive electrode material precursor is different from the precursor prepared by the prior art, the positive electrode material precursor is a secondary microsphere formed by agglomeration of primary particles, the secondary microsphere comprises a three-layer structure from inside to outside, namely a core layer, a middle layer and an outermost layer, the core layer has a specific diffraction peak structure, and the secondary microsphere has a higher specific surface area. This particular structure gives the precursor better electrochemical properties, such as higher specific discharge capacity, which can be used in high performance lithium batteries.

Comparative example 1

The prepared metal source solution and NaOH solution are simultaneously added into a reaction kettle under the stirring state to carry out precipitation reaction, and ammonia water solution accounting for 30 percent of the volume of the kettle is added into the reaction kettle in advance, wherein the concentration of the ammonia water is 0.5mol/L. Wherein the flow rate of the metal source solution was the same as in example 1, the flow rate of the NaOH solution was controlled so that the pH of the reaction system was 11. The total amount of ammonia (the total amount of ammonia was the same as in example 1) was added to the reaction system 1h, 10h, 30h after the start of the reaction, respectively, 3 times on average. Wherein the solid content of the reaction system in the 6 th hour is 8.5wt%, the stirring speed in the reaction process is 800rpm, the reaction temperature is 55 ℃, and the total reaction time is 48 hours. And (3) after natural cooling, stopping the precipitation reaction, carrying out vacuum suction filtration on the slurry, washing 3 times by using deionized water, and drying and dehydrating in a vacuum drying oven at 120 ℃ for 12 hours to obtain a positive electrode material precursor.

SEM test is carried out on the prepared positive electrode material precursor, the positive electrode material precursor is an irregular aggregate formed by loose aggregation of nano particles, the sphericity of the particles is poor, and the precursor with the morphology cannot meet the requirement of the battery field on the precursor material.

XRD testing of the core layer of the prepared positive electrode material precursor was conducted in accordance with the method of example 1, and the result showed that the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes in the XRD spectrum of the core layer was 0.64.

The prepared positive electrode material precursor is subjected to specific surface area test, and the specific surface area of the secondary microsphere is 0.48m ² /g。

The positive electrode material precursor prepared in comparative example 1 was prepared and assembled into a lithium ion battery according to the method of example 1. The electrochemical performance of the positive electrode material is measured under the conditions that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, and the result shows that the initial discharge specific capacity at 0.1C rate is 170.2mAh/g and the discharge specific capacity at 1C rate is 158.6mAh/g, which is far lower than the effect of the embodiment of the invention.

In summary, the inner core layer of the positive electrode material precursor prepared by the method provided by the invention has a specific diffraction peak structure, and meanwhile, the positive electrode material precursor has a higher specific surface area, and the positive electrode material prepared by using the positive electrode material precursor is applied to a lithium ion battery, so that the discharge specific capacity of the lithium ion battery is high.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. The positive electrode material precursor is characterized by being secondary microspheres formed by agglomeration of primary particles; wherein the secondary microsphere comprises a core layer and a middle layer from inside to outsideAn interlayer and an outermost layer, wherein the ratio of intensities of (110) and (102) crystal plane diffraction peaks in the X-ray diffraction pattern of the inner core layer is 1-8, preferably 1.5-4; the specific surface area of the secondary microsphere is 0.5-15m ² /g。

2. The positive electrode material precursor according to claim 1, wherein the relationship of the degree of densification of the inner core layer, the intermediate layer, and the outermost layer is: the middle layer > the inner core layer > the outermost layer;

preferably, the thickness of the inner core layer is 0.1-50%, the thickness of the middle layer is 40-95% and the thickness of the outermost layer is 0.1-20% based on the radius of the secondary microsphere being 100%;

Preferably, the secondary microsphere has a particle size of 1-30 μm.

3. The positive electrode material precursor according to claim 1 or 2, wherein the shape of the primary particles is selected from at least one of a sheet, a plate, a needle, and a spindle.

4. The positive electrode material precursor according to any one of claims 1 to 3, wherein the positive electrode material precursor has a chemical formula of Ni _x Co _y M _z T _p (OH) _2-q The method comprises the steps of carrying out a first treatment on the surface of the Wherein M is at least one selected from Cu, nd, mg, W, mo, zn, sn, sr, mn and Al; t is selected from at least one of N, P, S; x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 0.5, wherein at least one of the values of x, y and z is not 0, and the value range of q is determined according to the electric neutral principle.

5. A method of preparing a precursor for a positive electrode material, comprising the steps of:

6. The method according to claim 5, wherein the concentration of the complexing agent in the precipitation reaction system gradually increases and the rate of change of the concentration of the complexing agent gradually decreases;

preferably, the concentration change rate of the complexing agent is 1 mol/L.multidot.h or less, preferably 0.001 to 1 mol/L.multidot.h, and more preferably 0.001 to 0.5 mol/L.multidot.h;

preferably, the concentration change rate of the complexing agent is not less than 0.021 mol/L.h in the first 1/8R hours from the start of the reaction;

preferably, the time from adding the complexing agent to 80% or more of the concentration of the complexing agent at the end of the reaction in the precipitation reaction system is not more than 1/4R hours;

preferably, the concentration of complexing agent at the end of the reaction is from 0.05 to 2mol/L, preferably from 0.05 to 1.2mol/L.

7. The method of claim 5 or 6, wherein the precipitation reaction conditions include: the temperature is 20-70deg.C, preferably 45-60deg.C; the pH value is 8-14, preferably 10-12; the reaction time is not less than 10 hours, preferably 12-96 hours; the stirring speed is 50-1200r/min, preferably 600-1200r/min.

8. The method of any one of claims 5-7, wherein the precipitation reaction comprises: simultaneously adding a metal source solution, a precipitator solution and a complexing agent solution into a reaction kettle under a stirring state for reaction;

Preferably, the base solution is added to the reaction vessel prior to adding the metal source solution, the precipitant solution and the complexing agent solution to the reaction vessel;

preferably, the base solution is an aqueous solution containing a complexing agent; the concentration of the complexing agent in the base solution is 0-1.8mol/L, preferably 0.05-1.5mol/L, and more preferably 0.1-1.0mol/L;

preferably, the concentration of complexing agent in the base fluid is at least 0.05mol/L lower than the concentration of complexing agent at the end of the reaction, preferably at least 0.1mol/L lower;

preferably, the volume of the base liquid is 0-100%, preferably 0-80%, and more preferably 10-60% of the volume of the reaction kettle.

9. The method of any one of claims 5-8, wherein the metal source is selected from at least one of a nickel source, a cobalt source, and an M source, M being selected from at least one of Cu, nd, mg, W, mo, zn, sn, sr, mn and Al;

preferably, the precipitant is selected from at least one of alkali metal hydroxide, carbonate and bicarbonate;

preferably, the alkali metal is selected from at least one of Na, K, and Li;

preferably, the complexing agent is selected from at least one of an ammonium ion donor, an alcohol amine complexing agent, an aminocarboxylic acid complexing agent, a hydroxyamino carboxylic acid complexing agent, a carboxylate complexing agent, and a thiocyanate complexing agent.

10. The method of claim 9, wherein the nickel source is selected from at least one of nickel sulfate, nickel nitrate, nickel acetate, nickel oxalate, and nickel chloride;

preferably, the cobalt source is selected from at least one of cobalt nitrate, cobalt chloride, cobalt acetate and cobalt sulfate;

preferably, the M source is selected from at least one of sulfate, nitrate, acetate and oxalate of M.

11. The method according to any one of claims 5 to 10, wherein the concentration of the metal source solution is 0.01 to 5mol/L, preferably 0.01 to 4mol/L, in terms of metal element;

preferably, the concentration of the precipitant solution is 0.01-16mol/L, preferably 2-12mol/L;

preferably, the concentration of the complexing agent solution is 0.01-16mol/L, preferably 2-15mol/L.

12. The method of any one of claims 9-11, wherein the precipitation reaction further comprises: adding a T source into the metal source solution, wherein T is at least one selected from N, P, S;

preferably, the molar ratio of the nickel source, the cobalt source, the M source and the T source in terms of metal element is (0-1): (0-1): (0-1): (0-0.5), wherein at least one of the molar amounts of the nickel source, the cobalt source and the M source is not 0.

13. A positive electrode material precursor prepared by the method of any one of claims 5-12.

14. A positive electrode material, characterized in that it comprises a lithium source and a positive electrode material precursor according to any one of claims 1-4, 13.

15. A lithium ion battery comprising the positive electrode material of claim 14.