CN117342624A

CN117342624A - High-stability positive electrode material precursor and preparation method and application thereof

Info

Publication number: CN117342624A
Application number: CN202210751978.6A
Authority: CN
Inventors: 张同宝; 汪碧微; 张宇; 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 high-stability positive electrode material precursor, a preparation method and application thereof. The positive electrode material precursor 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, in an X-ray diffraction pattern of the outermost layer, the ratio of the intensities of the diffraction peaks of (110) and (102) crystal faces is 0.1-1.5, and the diameter distance of the secondary microsphere is 0.1-1. 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 product; carrying out solid-liquid separation and drying on the reaction product; wherein the total reaction time is expressed as R hours, and the variation range of the solid content of the reaction system is below 3wt% from 1/12R hours before the end of the reaction to the end of the reaction. The cathode material prepared from the cathode material precursor is applied to a lithium ion battery, and the cycle stability of the cathode material is obviously improved.

Description

High-stability positive electrode material precursor and preparation method and application thereof

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 ternary positive electrode material with the layered structure has the advantage of high energy density, and can meet the use requirements of application terminals such as electric automobiles, notebook computers and the like. With the increase of energy density, the cycling stability of the ternary positive electrode material with a layered structure is reduced, and the problem needs to be solved urgently.

At present, the cycling stability of the material is mainly improved by modifying the ternary positive electrode material. For example, patent application CN109742347a discloses a coating modified high-nickel positive electrode material and a preparation method thereof, wherein a solvent and a phosphate coating precursor capable of being dissolved in the solvent are used to form a phosphate coating layer on the surface of the high-nickel positive electrode material so as to improve the cycle stability of the material. Patent application CN102210045a discloses doping modification using Mg, ti, zr, al and Fe components, improving the cycling stability of Ni, co and Mn based positive electrode active materials under high voltage conditions. Although the modification process improves the cycle stability of the ternary cathode material, the modification process has the problems of complex operation process, high cost, poor controllability and consistency and the like.

The ternary positive electrode material is generally produced by preparing a precursor material through a coprecipitation process and then through a high-temperature solid-phase reaction with lithium salt. The properties of the precursor have great influence on the properties of the final positive electrode material, and the improvement of the performances such as the cycling stability of the ternary positive electrode material through the structural design of the precursor material is a brand new thought.

Disclosure of Invention

The invention aims to solve the problem that a ternary positive electrode material in the prior art has poor cycling stability in the cycling process of a battery, 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 peak to the (102) crystal face diffraction peak in the X-ray diffraction spectrum of the outermost layer is 0.1-1.5, preferably 0.5-1.5; the diameter distance of the secondary microsphere is 0.1-1.

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 variation range of the solid content of the precipitation reaction system is below 3wt% from 1/12R hours before the end of the reaction to the end of the reaction.

Preferably, the solid content of the precipitation reaction system is not less than 9wt% 1/12R hours before the end 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 varies at a rate of less than 0.005 mol/L.h from 1/12R hours before the end of the reaction to the end of the reaction.

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 outermost layer has a specific diffraction peak structure, the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal planes is 0.1-1.5, preferably 0.5-1.5, and the diameter of the secondary microsphere is 0.1-1.

According to the invention, the change range of the solid content of the precipitation reaction system is below 3wt% by controlling 1/12R hours before the reaction is finished to the reaction end, so that the outermost layer of the prepared positive electrode material precursor has a specific diffraction peak structure, the diameter distance of the secondary microspheres is narrower, the consistency of the charge states of different particles in the charge-discharge process is improved while the material interface and the electrolyte side reaction are improved, and the cycling stability of the material is improved.

The positive electrode material prepared by using the positive electrode material precursor is applied to a lithium ion battery, and the lithium ion battery has better cycling stability. As can be seen from the examples, at 1C rate, the first cycle of the lithium ion battery can output an energy density of 674.2Wh/kg based on the mass calculation of the positive electrode material, and the capacity retention rate can reach 101% of the initial capacity of 1C after 200 cycles of charge and discharge. The positive electrode material precursor provided by the invention can be used in a lithium ion battery with high energy density and high stability.

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

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

FIG. 5 is an XRD pattern of the outermost layer of the positive electrode material precursor prepared in example 1 of the present invention;

fig. 6 is a graph showing the cycle result of a lithium ion battery assembled from the positive electrode material prepared in example 1 of the present invention;

fig. 7 is a graph showing the cycle results of a lithium ion battery assembled from the positive electrode material prepared in comparative 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, and the ratio of the intensities of the (110) and (102) crystal plane diffraction peaks in the outermost layer X-ray diffraction pattern is 0.1-1.5, preferably 0.5-1.5, more preferably 0.8-1.3, for example, any value in the range consisting of 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3 and any two of these values. The diameter of the secondary microsphere is 0.1 to 1, preferably 0.3 to 1, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 and any value in the range of any two of these values.

In the present invention, the X-ray diffraction pattern (XRD) of the outermost layer was measured by an X-ray diffractometer of the D8 advanced SS model of Bruce, germany. Diffraction peaks of the outermost layer at positions of 56-61 DEG and 48-54 DEG in the XRD spectrum correspond to the (110) crystal plane and the (102) crystal plane, respectively. (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 present invention, the diameter of the secondary microspheres was measured by a Mastersizer 3000 laser particle sizer, company Malvern Panalytical, uk. The diameter distance of the secondary microsphere is obtained by a formula (D90-D10)/D50, wherein D10 is the particle size corresponding to the particle size distribution reaching 10%, D50 is the particle size corresponding to the particle size distribution reaching 50%, and D90 is the particle size corresponding to the particle size distribution reaching 90%.

The inventor of the invention discovers in the research that the outermost layer of the positive electrode material precursor has the specific diffraction peak structure, the diffraction peak structure has lower activity, which is beneficial to stabilizing the interface of the material, meanwhile, the particle size distribution of the secondary microspheres is narrower, the consistency of the charge states of different particles in the charge and discharge process is good, and the cycling stability of the material is improved.

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 of the positive electrode material precursor (fig. 3 and 4) can be used for observing 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. 3, 4), 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. 3 and 4), it can be observed that the core layer is formed by primary platelet aggregation, the core layer is relatively loose in the form of platelet aggregation, the thickness of the core layer is about 1.1 μm, the outermost layer is also formed by primary platelet aggregation, the outermost layer is more loose than the core layer, the thickness of the outermost layer is about 0.22 μm, the intermediate layer between the core layer and the outermost layer is very dense, and the thickness of the intermediate layer is about 3.8 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, effectively inhibit the cracking and crushing problems of the active substance caused by volume expansion and contraction in the charging and discharging process, and improve the cycling stability of the material. The intermediate layer has the highest density, and can effectively improve the volume energy density of the active material. The outermost layer has the lowest density, and can quickly embed external lithium ions into a material body phase, so that the interfacial resistance of the material is effectively reduced, and the cycling stability of the active material is remarkably improved.

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 Mastersizer 3000 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, ge, mg, W, mo, zn, sn, ce, mn and Al, preferably at least one of Mn, al, zn, ge and Ce; 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 varies from 1/12 of the hour before the end of the reaction to the end of the reaction by not more than 3wt%, for example, 0wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, and any value in the range constituted by any two of these values.

Through intensive researches on the precipitation reaction process, the inventor discovers that the change range of the solid content of the precipitation reaction system is within the range from 1/12R hour before the reaction is finished to the reaction end, the secondary microsphere precursor particles formed by the aggregation of primary particles are creatively obtained, the aggregation form of the primary particles can be controlled, so that the core layer is aggregated more loosely, the middle layer is aggregated more tightly, the outermost layer is aggregated more loosely, the outermost layer can be controlled to present a specific diffraction peak structure and a narrower secondary microsphere size distribution, and the positive electrode material precursor material with the characteristics has better cycling stability and can be used in high-performance lithium ion batteries.

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, ge, mg, W, mo, zn, sn, ce, mn and Al, preferably Ge, ce, zn, 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 lower than 0.005 mol/L.h, preferably 0.001 to 0.005 mol/L.h, for example, 0.001 mol/L.h, 0.0015 mol/L.h, 0.002 mol/L.h, 0.0025 mol/L.h, 0.003 mol/L.h, 0.0035 mol/L.h, 0.004 mol/L.h, 0.0045 mol/L.h, 0.005 mol/L.h, and any value in the range of any two of these values, from 1/12R hours before the end of the reaction to the end of the reaction. By adopting the preferable scheme, the circulation 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 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 a preferred embodiment of the present invention, the solid content of the precipitation reaction system is not less than 9wt%, preferably 9 to 40wt%, further preferably 9 to 20wt%, for example, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, and any value in the range constituted by any two of these values, 1/12R hours before the end of the reaction. By adopting the preferable scheme, the outermost layer with a specific structure can be obtained, and the cycle stability of the prepared positive electrode material precursor is further improved.

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 and the variation range thereof 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 2-5, and then the flow rate of the metal source solution is kept unchanged, the concentration of the complexing agent and the change rate thereof in the precipitation reaction system are controlled to be within the above-defined range by controlling the flow rate of the complexing agent, and the pH of the precipitation reaction system is controlled to satisfy the above-mentioned range by controlling the flow rate of the precipitant solution, so that the solid content of the precipitation reaction system and the change range thereof can be regulated and controlled. If the solid content rate can not meet the requirement in the mode, the solid content rate can be increased to the range through an online concentrator.

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 the research that the cathode material provided by the invention is used in a lithium ion battery, and can improve the cycle stability 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, polyethylene and polypropylene composite, 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 diametral distance 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 2mol/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 6mol/L.

Adding ammonia water solution accounting for 40% of the volume of the reaction kettle, wherein the concentration of the ammonia water is 0.5mol/L, adding a proper amount of NaOH, and adjusting the pH value of the solution to 11.9. The base solution was heated to 50 ℃ and held until the reaction was completed. And simultaneously adding the metal source solution, the NaOH solution and the complexing agent solution into a reaction kettle under the stirring state, wherein the stirring speed is 900rpm. Controlling the ratio of the initial volume flow rate of the metal source solution to the initial volume flow rate of the complexing agent solution to be 4, then keeping the flow rate of the metal source solution unchanged, and controlling the flow rate of the NaOH solution to keep the pH of the reaction system at about 11.9; the flow rate of the complexing agent ammonia water 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, the concentration of the complexing agent in the reaction system is about 0.8mol/L until the reaction is finished, and the concentration of the complexing agent in the reaction system changes with time as shown in figure 2. And (3) in the 8 th hour before the reaction is finished, the solid content of the reaction system is improved to about 12wt% by a thickener, the variation range of the solid content in the reaction system is lower than 1wt% in the 8 th hour before the reaction is finished, and the concentration variation range of the complexing agent in the reaction system is lower than 0.005 mol/L.h. Starting timing by adding a metal source solution, a NaOH solution and a complexing agent solution simultaneously, stopping the reaction after the reaction time reaches 48 hours, performing vacuum suction filtration on the slurry, washing 3 times by deionized water, 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. 3. As can be seen from FIG. 3, the preparation method provided by the invention can be used for obtaining the 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. 4, and as can be seen from fig. 4, 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 1.1 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 0.22 mu m, the agglomeration of the middle layer between the inner core layer and the outermost layer is very compact, and the thickness of the middle layer is about 3.8 mu m.

The positive electrode material precursor prepared in example 1 was subjected to particle size test, and the result showed that the secondary microsphere of the positive electrode material precursor had a medium particle size D50 of 10.2 μm and a diameter distance of 0.46.

The outermost layer of the positive electrode material precursor prepared in example 1 was subjected to X-ray diffraction analysis, and the result is shown in fig. 5. It can be seen from fig. 5 that the outermost layer (102) has a high intensity of the diffraction peak of the crystal face, and the ratio of the intensities of the diffraction peaks of the (110) and (102) crystal faces is 0.86.

(3) Preparation and evaluation of cathode Material

Taking the positive electrode material precursor prepared in example 1 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 520 ℃ in oxygen atmosphere, and then solid phase reaction is carried out for 16h at 800 ℃ 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 lithium hexafluorophosphate LiPF ₆ The molar concentration was 1mol/L. The 2032 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 at 1C rate was measured at a charge-discharge voltage ranging from 2.5 to 4.3V and an ambient temperature of 25C, and the charge-discharge cycle results are shown in fig. 6. From fig. 6, it can be seen that the electrochemical activity of the positive electrode material gradually increases in the circulation process, the first cycle of 1C rate can output energy density 674.2Wh/kg based on the mass calculation of the positive electrode material, the capacity of 200 cycles exceeds the capacity of the first cycle of 1C rate, the capacity retention rate reaches 101%, and the cycle stability is excellent, so that the positive electrode material can be used in a lithium ion battery with high stability.

Example 2

(1) Preparation of positive electrode material precursor

Preparing a metal source solution with the concentration of 4mol/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 10 mol/L; preparing complexing agent ammonia water solution, wherein the concentration of ammonia water is 6mol/L.

Adding 30% ammonia water solution into the reaction kettle, wherein the concentration of the ammonia water is 0.5mol/L, adding a proper amount of NaOH, and adjusting the pH value of the solution to 11.2. The base solution was heated to 60 ℃ and held until the reaction was completed. And simultaneously adding the metal source solution, the NaOH solution and the complexing agent solution into a reaction kettle under the stirring state, wherein the stirring speed is 900rpm. Controlling the ratio of the initial volume flow rate of the metal source solution to the initial volume flow rate of the complexing agent solution to be 4, then keeping the flow rate of the metal source solution unchanged, and controlling the flow rate of the NaOH solution to keep the pH of the reaction system at 11.2; the flow rate of the complexing agent ammonia water 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, the concentration of the complexing agent in the reaction system is about 0.8mol/L until the reaction is finished, and the concentration of the complexing agent in the reaction system changes with time as shown in figure 2. The solid content of the reaction system is controlled to be about 17wt% by a thickener in the 6h before the reaction is finished, the variation range of the solid content in the reaction system is lower than 2wt% and the concentration variation range of the complexing agent in the reaction system is lower than 0.005 mol/L.h. Starting timing by adding a metal source solution, a NaOH solution and a complexing agent solution simultaneously, stopping the reaction after the reaction time reaches 48 hours, performing vacuum suction filtration on the slurry, washing 3 times by deionized water, 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. 3 and 4.

The positive electrode material precursor prepared in example 2 was subjected to particle size measurement, and the result showed that the diameter of the secondary microsphere was 0.58.

XRD test is carried out on the outermost layer of the prepared positive electrode material precursor, and the result shows that the ratio of the intensity of the diffraction peaks of the (110) crystal face to the intensity of the diffraction peaks of the (102) crystal face in the XRD spectrum of the outermost layer is 0.94.

(3) Preparation and evaluation of cathode Material

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

Under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, the electrochemical performance of the positive electrode material under the 1C multiplying power is measured, the first circle of 1C multiplying power is calculated based on the mass of the positive electrode material, the energy density 668.7Wh/kg can be output, and the charge-discharge cycle result shows that the capacity retention rate of 200 circles of cycles is 100.2%.

Example 3

(1) Preparation of positive electrode material precursor

Preparing a metal source solution with the concentration of 4mol/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 10mol/L.

Adding an ammonia water solution accounting for 60 percent of the volume of the reaction kettle, wherein the concentration of the ammonia water is 0.5mol/L, adding a proper amount of NaOH, and adjusting the pH value of the solution to be 10.2. The base solution was heated to 60 ℃ and held until the reaction was completed. And simultaneously adding the metal source solution, the NaOH solution and the complexing agent solution into a reaction kettle under the stirring state, wherein the stirring speed is 700rpm. Controlling the ratio of the initial volume flow rate of the metal source solution to the initial volume flow rate of the complexing agent solution to be 5, then keeping the flow rate of the metal source solution unchanged, and controlling the flow rate of the NaOH solution to keep the pH of the reaction system at 10.2; the flow rate of the complexing agent ammonia water 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, the concentration of the complexing agent in the reaction system is about 0.8mol/L until the reaction is finished, and the concentration of the complexing agent in the reaction system changes with time as shown in figure 2. And (3) at the 5 th hour before the reaction is finished, the solid content of the reaction system is improved to about 19wt% by a thickener, and the variation range of the solid content in the reaction system is lower than 2.8wt% within 5h before the reaction is finished, and the concentration variation range of the complexing agent in the reaction system is lower than 0.005 mol/L.h. Starting timing by adding a metal source solution, a NaOH solution and a complexing agent solution simultaneously, stopping the reaction after the reaction time reaches 48 hours, performing vacuum suction filtration on the slurry, washing 3 times by deionized water, 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 positive electrode material precursor prepared in example 3 was subjected to particle size test, and the result showed that the diameter distance of the secondary microsphere was 0.95.

XRD test is carried out on the outermost layer of the prepared positive electrode material precursor, and the result shows that the ratio of the intensity of the diffraction peaks of the (110) crystal face to the intensity of the diffraction peaks of the (102) crystal face in the XRD spectrum of the outermost layer is 1.24.

(3) Preparation and evaluation of cathode Material

Under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, the electrochemical performance of the positive electrode material under the 1C multiplying power is measured, the first circle of 1C multiplying power is calculated based on the mass of the positive electrode material, the energy density 656.5Wh/kg can be output, and the charge-discharge cycle result shows that the capacity retention rate of 200 circles of cycles is 96.7%.

Example 4

(1) Preparation of positive electrode material precursor

The procedure is as described in example 1, except that ZnSO is added to the metal source solution ₄ Which is provided withMedium Zn/(ni+co+mn) =1%mol, to obtain a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

The positive electrode material precursor prepared in example 4 was subjected to particle size measurement, and the result showed that the diameter of the secondary microsphere was 0.71.

XRD test is carried out on the outermost layer of the prepared positive electrode material precursor, and the result shows that the ratio of the intensity of the diffraction peaks of the (110) crystal face to the intensity of the diffraction peaks of the (102) crystal face in the XRD spectrum of the outermost layer is 1.07.

(3) Preparation and evaluation of cathode Material

Under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, the electrochemical performance of the positive electrode material under the 1C multiplying power is measured, the first circle of 1C multiplying power is calculated based on the mass of the positive electrode material, the energy density 664.6Wh/kg can be output, and the charge-discharge cycle result shows that the capacity retention rate of 200 circles of cycles is 99.5%.

Example 5

(1) Preparation of positive electrode material precursor

The procedure is as described in example 1, except that Ce (NO ₃ ) ₃ ·6H ₂ O, where Ce/(ni+co+mn) =1%mol, gives a positive electrode material precursor.

(2) Evaluation of the precursor of the cathode Material

The positive electrode material precursor prepared in example 5 was subjected to particle size measurement, and the result showed that the diameter distance of the secondary microsphere was 0.63.

XRD test is carried out on the outermost layer of the prepared positive electrode material precursor, and the result shows that the ratio of the intensity of the diffraction peaks of the (110) crystal face to the intensity of the diffraction peaks of the (102) crystal face in the XRD spectrum of the outermost layer is 0.96.

(3) Preparation and evaluation of cathode Material

Under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, the electrochemical performance of the positive electrode material under the 1C multiplying power is measured, the first circle of 1C multiplying power is calculated based on the mass of the positive electrode material, the energy density 667.9Wh/kg can be output, and the charge-discharge cycle result shows that the capacity retention rate of 200 circles of cycles is 99.9%.

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 positive electrode material precursor prepared in example 6 was subjected to particle size test, and the result showed that the diameter distance of the secondary microsphere was 0.84.

XRD test is carried out on the outermost layer of the prepared positive electrode material precursor, and the result shows that the ratio of the intensity of the diffraction peaks of the (110) crystal face to the intensity of the diffraction peaks of the (102) crystal face in the XRD spectrum of the outermost layer is 1.08.

(3) Preparation and evaluation of cathode Material

Under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, the electrochemical performance of the positive electrode material under the 1C multiplying power is measured, the first circle of 1C multiplying power is calculated based on the mass of the positive electrode material, the energy density 663.5Wh/kg can be output, and the charge-discharge cycle result shows that the capacity retention rate of 200 circles of cycles is 99.1%.

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.

Adding 30% ammonia water solution into the reaction kettle, wherein the concentration of the ammonia water is 0.5mol/L, adding a proper amount of NaOH, and adjusting the pH value of the solution to 10.5. The base solution was heated to 55℃and held until the reaction was completed. The metal source solution, the NaOH solution and the complexing agent solution are simultaneously added into the reaction kettle under the stirring state, and the stirring speed is 1000rpm. Controlling the ratio of the initial volume flow rate of the metal source solution to the initial volume flow rate of the complexing agent solution to be 2, then keeping the flow rate of the metal source solution unchanged, and controlling the flow rate of the NaOH solution so as to keep the pH of the reaction system at 10.5; the flow rate of the complexing agent ammonia water 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, the concentration of the complexing agent in the reaction system is about 0.8mol/L until the reaction is finished, and the concentration of the complexing agent in the reaction system changes with time as shown in figure 2. And controlling the solid content of the reaction system to be about 15wt% by a thickener in the 6h before the reaction is finished, wherein the variation range of the solid content in the reaction system is lower than 1.2wt% and the concentration variation range of the complexing agent in the reaction system is lower than 0.005 mol/L.h. Starting timing by adding a metal source solution, a NaOH solution and a complexing agent solution simultaneously, stopping the reaction after the reaction time reaches 48 hours, performing vacuum suction filtration on the slurry, washing 3 times by deionized water, 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 positive electrode material precursor prepared in example 7 was subjected to particle size measurement, and the result showed that the diameter of the secondary microsphere was 0.62.

XRD test is carried out on the outermost layer of the prepared positive electrode material precursor, and the result shows that the ratio of the intensity of the diffraction peaks of the (110) crystal face to the intensity of the diffraction peaks of the (102) crystal face in the XRD spectrum of the outermost layer is 0.97.

(3) Preparation and evaluation of cathode Material

Under the condition that the charge-discharge voltage range is 2.5-4.3V and the ambient temperature is 25 ℃, the electrochemical performance of the positive electrode material under the 1C multiplying power is measured, the first circle of 1C multiplying power is calculated based on the mass of the positive electrode material, the energy density 681.5Wh/kg can be output, and the charge-discharge cycle result shows that the capacity retention rate of 200 circles of cycles is 99.7%.

From the above results, it can be seen that the method of the present invention prepares a novel positive electrode material precursor, which is different from the precursor prepared in the prior art, and the positive electrode material precursor is a secondary microsphere formed by agglomerating primary particles, and the secondary microsphere includes a three-layer structure from inside to outside, i.e., a core layer, a middle layer and an outermost layer, and the outermost layer has a specific diffraction peak structure, and at the same time, the diameter distance of the secondary microsphere is relatively narrow. This particular structure gives the precursor better electrochemical properties, such as better cycling stability, and can be used in high performance lithium ion 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 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. Wherein the flow rate of the metal source solution was the same as in example 1, and the flow rate of the NaOH solution was controlled so that the pH of the reaction system was about 11.9. The total amount of ammonia (the total amount of ammonia was the same as in example 1) was added to the reaction system at 6h, 24h, 45h after the start of the reaction, respectively, 3 times on average. The solid content of the reaction system was about 8.5wt% at 8h before the end of the reaction, and the variation range of the solid content in the reaction system was higher than 3.2wt% within 8h before the end of the reaction. In the reaction process, the stirring speed is controlled to be 900rpm, 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.

XRD test is carried out on the outermost layer of the prepared positive electrode material precursor, and the ratio of the intensity of the diffraction peaks of the (110) crystal face to the intensity of the diffraction peaks of the (102) crystal face in the XRD spectrum is 1.98.

And performing particle size test on the prepared positive electrode material precursor, wherein the result shows that the diameter distance of the precursor is up to 1.97.

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 at 1C rate was measured at a charge-discharge voltage ranging from 2.5 to 4.3V and an ambient temperature of 25C, and the charge-discharge cycle results are shown in fig. 7. The energy density 588.8Wh/kg can be output by calculating the first circle of 1C multiplying power based on the mass of the positive electrode material, and the capacity retention rate of the positive electrode material precursor prepared by adopting the method of comparative example 1 for 200 circles is only 31.0%, which is far lower than the effect of the embodiment of the invention.

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 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 peak to the (102) crystal face diffraction peak in the X-ray diffraction spectrum of the outermost layer is 0.1-1.5, preferably 0.5-1.5; the diameter distance of the secondary microsphere is 0.1-1.

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, ge, mg, W, mo, zn, sn, ce, 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 lower than 0.005 mol/L.h from 1/12R hours before the end of the reaction to the end of the reaction;

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 according to claim 5 or 6, wherein the solid content of the precipitation reaction system is not less than 9wt% 1/12R hours before the end of the reaction.

8. The method of any one of claims 5-7, 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.

9. The method of any one of claims 5-8, 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.

10. The method of any one of claims 5-9, 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, ge, mg, W, mo, zn, sn, ce, 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.

11. The method of claim 10, 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.

12. The method according to any one of claims 5 to 11, 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.

13. The method of any one of claims 10-12, 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.

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

15. 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, 14.

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