CN111682200B - Positive electrode material for lithium ion battery and preparation method thereof - Google Patents

Positive electrode material for lithium ion battery and preparation method thereof Download PDF

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CN111682200B
CN111682200B CN202010676272.9A CN202010676272A CN111682200B CN 111682200 B CN111682200 B CN 111682200B CN 202010676272 A CN202010676272 A CN 202010676272A CN 111682200 B CN111682200 B CN 111682200B
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positive electrode
lini
rare earth
electrode material
ion conductor
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CN111682200A (en
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贺克宝
张洁
刘逸群
陈睿
董林涛
安孝坤
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Wanhua Chemical Group Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a positive electrode material for a lithium ion battery, a preparation method of the positive electrode material, a positive electrode of the lithium ion battery containing the positive electrode material, and the lithium ion battery containing the positive electrode. The positive electrode material is LiNiaCobMncO2A mixture of a rare earth element-containing perovskite oxide and a fast ion conductor, wherein a + b + c is 1, 0.2<a<0.95，0.05<b<0.5, and 0.05<c<0.5; the mixture is granular, and the concentration of the rare earth element-containing perovskite oxide and the fast ion conductor in the granules is in gradient distribution; in addition, in a region where the concentration of the rare earth element-containing perovskite oxide and the concentration of the fast ion conductor are the highest, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0.1-2): (0.1-2). The cathode material has improved conductivity and lithium ion transmission rate, thereby improving the rate performance of the battery.

Description

Positive electrode material for lithium ion battery and preparation method thereof
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a high-rate low-stress anode material with concentration gradient doping for a lithium ion battery and a preparation method thereof.
Background
Along with energy transformation, fuel vehicles are gradually eliminated in the future in the world in response to national emission reduction plans, and hybrid and electric vehicles become mainstream choices in the global automobile field. Therefore, the development of power batteries is a great trend in the industry. The anode of the power battery used in the current power electric automobile market is mainly lithium iron phosphate and ternary materials, the lithium iron phosphate is low in energy storage density although the price is low, and even though the blade battery improves the energy density of a battery pack to a certain extent, the gap between the lithium iron phosphate and the ternary anode lithium ion battery is large, and the lithium iron phosphate is not in line with the development direction of automobile requirements with high driving mileage in the future. Lithium ion batteries based on high nickel ternary anodes have higher energy density and gradually have higher and higher market share, which is the first requirement of many automobile factories at present. On the other hand, electric vehicles need to be able to perform high-power discharge in a short time, which increases the rate capability of lithium ion batteries. Therefore, further improving the rate capability of the lithium ion battery is also a sign of great progress of the industry. However, to improve the rate capability of the lithium ion battery, the cathode material itself needs to have a higher lithium ion conduction rate and electron conduction rate. In addition, the high nickel cathode material can have a relatively serious volume expansion and contraction phenomenon in the charging and discharging processes, so that the internal and external stresses of the material are different, the stable structure of the material is damaged, and the performance of the battery is seriously reduced after long-cycle discharge.
Disclosure of Invention
Technical problem
The invention provides a novel positive electrode material with high rate performance and low stress and a preparation method thereof, aiming at the background that manufacturers of electric automobiles have higher requirements on the rate performance of batteries. In the material, the element concentration is in gradient distribution, so that the conductivity and the lithium ion transmission rate of the battery are improved, and the rate capability of the battery is improved.
Technical scheme
According to a first aspect of the inventionThe positive electrode material for the lithium ion battery is LiNiaCobMncO2A mixture of a perovskite oxide containing rare earth elements and a fast ion conductor,
wherein a + b + c is 1, 0.2< a <0.95, 0.05< b <0.5, and 0.05< c < 0.5; preferably a + b + c is 1, 0.3< a <0.9, 0.05< b <0.35, and 0.05< c < 0.35; more preferably a + b + c is 1, 0.6< a <0.9, 0.05< b <0.2, and 0.05< c <0.2, even more preferably a + b + c is 1, 0.7< a <0.9, 0.05< b <0.15, and 0.05< c < 0.15.
Wherein the mixture is in a granular form, and the concentration of the rare earth element-containing perovskite oxide and the concentration of the fast ion conductor in the mixture granules exhibit a gradient distribution.
In the region where the concentration of the rare earth element-containing perovskite oxide and the fast ion conductor is the greatest, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0.1-2): (0.1-2); preferably 100: (0.2-1.8): (0.2 to 1.8), more preferably 100: (0.3-1.6): (0.3-1.6).
Preferably, the LiNiaCobMncO2Is selected from LiNi0.8Co0.1Mn0.1O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.5Co0.2Mn0.3O2Or LiNi1/3Co1/3Mn1/3O2One or more of (a) or (b),
preferably, the concentration of the rare earth element-containing perovskite-type oxide and the fast ion conductor in the particles gradually decreases from the center to the outside of the particles of the mixture.
Preferably, at the center of the particles of the mixture, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0.1-2): (0.1-2); preferably 100: (0.2-1.8): (0.2E &1.8), more preferably 100: (0.3-1.6): (0.3 to 1.6), and
at the outermost part of the particles of the mixture, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0-1): (0-1); preferably 100: (0-0.8): (0 to 0.8), more preferably 100: (0-0.5): (0 to 0.5).
Preferably, the rare earth element-containing perovskite oxide is preferably RNidCoeMnfO3，
Wherein R represents a rare earth element, preferably selected from lanthanum, cerium, neodymium, ytterbium or europium, more preferably neodymium;
d + e + f is 1, 0.2< d <0.95, 0.05< e <0.5, and 0.05< f < 0.5; preferably d + e + f is 1, 0.3< d <0.9, 0.05< e <0.35, and 0.05< f < 0.35; more preferably d + e + f is 1, 0.6< d <0.9, 0.05< e <0.2, and 0.05< f <0.2, even more preferably d + e + f is 1, 0.7< d <0.9, 0.05< e <0.15, and 0.05< f < 0.15;
preferably, a: b: c-d: e: f;
preferably, the rare earth element-containing perovskite oxide is selected from NdNi0.8Co0.1Mn0.1O3、LaNi0.8Co0.1Mn0.1O3、EuNi0.8Co0.1Mn0.1O3、NdNi0.6Co0.2Mn0.2O3、NdNi0.5Co0.2Mn0.3O3、NdNi1/3Co1/ 3Mn1/3O3One or more of;
the fast ion conductor is selected from Li2WO4、LiAlO2、Li4SiO4、LiNbO3、Li2B4O7Or Li3PO4One or more of (a).
The fast ion conductor is dispersed in the particles of the mixture in the form of nanoparticles, and preferably, the particle size of the fast ion conductor is 10-100 nm, preferably 40-60 nm.
The median particle diameter of the anode material is 3-20 mu m, and the tap density is 2-3 g/cm3Preferably 2.4 to 2.7g/cm3。
According to a second aspect of the present invention, there is provided a method for preparing the positive electrode material, comprising the steps of:
1) preparing a mixed aqueous solution of nickel salt, cobalt salt and manganese salt, wherein the weight ratio of nickel: cobalt: the molar ratio of manganese is a: b: c; preferably, the concentration of nickel ions in the mixed aqueous solution is 0.1 to 3mol/L, more preferably 0.5 to 2.5 mol/L;
2) preparing an aqueous solution of rare earth metal salt, wherein the concentration is preferably 0.01-2 mol/L, and the concentration is more preferably 0.01-0.2 mol/L;
3) preparing an aqueous dispersion of fast ion conductor nanoparticles, preferably at a concentration of 0.01mol/L to 0.2mol/L, more preferably at a concentration of 0.01mol/L to 0.1 mol/L;
4) adding an alkaline water solution with the pH value of 11-14 into a reactor in an inert atmosphere, then adding a complexing agent water solution, and heating to 40-70 ℃, preferably 50-60 ℃; preferably, the concentration of the complexing agent in the reactor is 0.2-2.0 mol/L, preferably 0.4-0.6 mol/L;
5) dropwise adding the mixed aqueous solution of nickel salt, cobalt salt and manganese salt into a reactor at a constant speed, dropwise adding the aqueous solution of rare earth metal salt and the aqueous dispersion of the fast ion conductor into the reactor at a deceleration, dropwise adding a complexing agent and an alkali solution, and controlling the molar ratio, the concentration and the pH value of each component by controlling the feeding speed, wherein the pH value is preferably controlled to be 10-13, preferably 11-12; preferably, the deceleration may be a uniform deceleration or a stepped deceleration;
6) obtaining a reaction product after the reaction is finished, and obtaining a precursor with a concentration gradient doping substance after filter pressing, washing and drying;
7) calcining the precursor for the first time in a gas-in state, wherein the calcining temperature is 400-900 ℃, preferably 400-500 ℃, the calcining time is 1-10 hours, preferably 1-3 hours, and the gas is air or oxygen, preferably oxygen;
8) uniformly mixing the product obtained in the step 7) with a lithium compound, introducing air to calcine the obtained mixture, and obtaining the cathode material LiNi when the calcining temperature is 400-1000 ℃, preferably 750-950 ℃, and the calcining time is 2-15 hours, preferably 10-14aCobMncO2The gas is air or oxygen, preferably oxygen,
wherein a + b + c is 1, 0.2< a <0.95, 0.05< b <0.5, and 0.05< c < 0.5.
Preferably, the nickel, cobalt and manganese salts are each independently selected from the group consisting of sulfate, nitrate or chloride salts;
the rare earth metal salt is selected from sulfate, nitrate or chloride salt; among them, the rare earth metal is preferably selected from lanthanum, cerium, neodymium, ytterbium or europium, and more preferably neodymium;
the fast ion conductor is selected from Li2WO4、LiAlO2、Li4SiO4、LiNbO3、Li2B4O7Or Li3PO4Preferably, the particle size of the fast ion conductor nano particles is 10-100 nm;
the aqueous alkali solution in the step 4) is an aqueous sodium hydroxide solution and/or an aqueous potassium hydroxide solution, and the complexing agent is one or more selected from ammonia, urea, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium sulfate or ammonium acetate, preferably one or more selected from ammonia or urea, and more preferably ammonia;
in step 8), the amount of substance of lithium in the lithium compound is equal to the amount of the total substance of nickel, cobalt and manganese added minus the amount of the substance of the rare earth metal added; the lithium compound is one or more selected from lithium hydroxide or lithium carbonate.
Preferably, the median particle diameter of the cathode material is 3-20 μm, more preferably 6-12 μm, and the tap density is 2-3 g/cm3Preferably 2.4 to 2.7g/cm3。
The water is deoxygenated water.
According to a third aspect of the invention, a positive electrode of a lithium ion battery is provided, which comprises the positive electrode material of the invention.
According to a fourth aspect of the present invention, there is provided a lithium ion battery comprising the positive electrode according to the present invention.
Advantageous effects
The LiNiaCobMncO2The perovskite type oxide is a ternary cathode material, has a stable structure, and can improve the conductivity and reduce the resistance; the fast ion conductor can improve the conduction rate of lithium ions during charge and discharge. In the discharging process of the interior of the anode material, discharging is usually uneven, in order to realize uniform discharging inside and outside the material, the conductivity and the ion conduction rate of the interior are improved in a gradient doping mode, high-rate discharging is realized, internal and external uniform discharging is realized, and the problem that the structure of the electrode material is damaged due to uneven stress caused by the internal and external uniform discharging is solved.
The prepared anode material well utilizes the advantage of good conductivity of the perovskite oxide, and improves the conductivity of the material; meanwhile, the characteristic that the fast ion conductor conducts lithium ions fast is well utilized, and the conduction rate of the lithium ions is improved.
In view of the two advantages, the prepared cathode material can realize good electrochemical performance under high rate;
substances doped in the anode material prepared by the method have a certain concentration gradient, so that the problem of battery failure caused by uneven stress is effectively avoided, and the service life of the battery is well prolonged;
the method for preparing the cathode material is the same as the conventional method for preparing the cathode material, does not have additional steps, and is simple and efficient.
Drawings
Fig. 1 is an XRD spectrum showing the positive electrode materials obtained according to example 1 and comparative example 2.
Detailed Description
The following examples are only for better illustration of the present invention, and the scope of the present invention is not limited to the following examples.
The chemical information applied in the examples is as follows:
nickel sulfate hexahydrate (technical grade), langzhou jinchuan;
cobalt sulfate heptahydrate (industrial grade), check of Zhejiang thoroughfare China cobalt industry;
manganese sulfate monohydrate (industrial grade), which is a new material converged by Guizhou Dalong;
neodymium sulfate octahydrate (technical grade), Hubei Xin Rundji chemical Co., Ltd;
europium sulfate octahydrate (technical grade), Shandong De Sheng New materials Co., Ltd;
lanthanum sulfate nonahydrate (technical grade), boehan, a. professor, a. a, a. professor, a. peru.l.l.l.;
ammonia (analytical grade), alatin;
sodium hydroxide (analytically pure), chinese medicine;
lithium hydroxide monohydrate (technical grade), the Jiangxi lithium industry;
lithium carbonate (technical grade), gan feng li industry;
polyvinylidene fluoride (PVDF) (analytical grade), alatin;
the main device information is as follows:
the reaction kettle is: weihai city Zhenhang chemical machinery, Inc.;
the electrochemical test equipment is a Switzerland Wantong electrochemical workstation Autolab;
the roasting equipment adopts a tube furnace of fertilizer combination crystal, and the model is OTF-1500X;
the X-ray energy spectrometer is purchased from Horiba of Japan and has the model number of Horiba 7021-H;
the X-ray diffractometer was purchased from PANALYtic, the Netherlands, and the model number is X' pert.
Example 1
Preparing a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the molar ratio of Ni to Co to Mn is 8:1:1, the concentration of nickel sulfate is 1.6mol/L, the concentration of cobalt sulfate is 0.2mol/L, and the concentration of manganese sulfate is 0.2 mol/L. 0.05mol/L neodymium sulfate (Nd) is prepared by using dilute sulfuric acid with pH value of 32(SO4)3) And (3) solution. Mixing Li with a particle size of 50nm2B4O7Dispersed in water to prepare a 0.1mol/L dispersion. Preparing ammonia solution with ammonia concentration of 4mol/L for regulating and controlling the ammonia concentration in the reaction process. Preparing a sodium hydroxide solution with the concentration of 12 mol/L. The solutions described above were all prepared using deoxygenated water. Preparing 2L of base solution by using sodium hydroxide, wherein the pH value of the base solution is 12.60(25 ℃), adding the base solution into a reaction kettle, starting stirring, wherein the stirring speed is 800rpm, introducing high-purity nitrogen for 10 minutes, then closing a vent valve, turning off the stirring, adding ammonia water into the reaction kettle to ensure that the ammonia concentration of a system is 0.5mol/L, heating the reaction system to 60 ℃, starting feeding, starting stirring, wherein the stirring speed is 800rpm, the feeding speed of a transition metal salt solution is 400mL/h, and the feeding speed of a neodymium sulfate solution and Li are respectively 400mL/h2B4O7The dispersion was fed at a rate of 40mL/h, and every half hour, the neodymium sulfate solution and Li were added2B4O7The dispersion feed rate was decreased by 1.25mL/h, respectively, while adjusting the ammonia feed rate so that the ammonia concentration in the reactor was kept approximately constant, and the feed rate of the sodium hydroxide solution was adjusted according to the set pH value. After reacting for 16h, taking out the reactant, and carrying out filter pressing, washing and drying. Putting the dried reactant into a tube furnace, introducing oxygen, heating the tube furnace to 500 ℃ for primary calcination, and calcining for 6h to ensure that Nd (OH) is in the precursor3And Ni0.8Co0.1Mn0.1(OH)2Reacting to generate the perovskite type oxide NdNi with concentration gradient0.8Co0.1Mn0.1O3And Li2B4O7The precursor of (1). Weighing LiOH according to the amount of salt obtained by subtracting the amount of the rare earth metal from the total amount of nickel, cobalt and manganese by the amount of the lithium, mixing the LiOH with the precursor, and then placing the mixture into a tubular furnace for secondary calcination at the calcination temperature of 800 ℃ for 10h in the presence of oxygen to obtain the target cathode material. The particle size of the particles was 10.8. mu.m, and the tap density was 2.58g/cm3。
The positive electrode material having a concentration gradient distribution obtained in this way had a central composition of (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) 100:0.5:0.5 (molar ratio), and LiNi as the outermost portion0.8Co0.1Mn0.1O2。
Fig. 1 is an XRD pattern showing the cathode material obtained according to example 1, which can be seen in fig. 1: wherein Li is present in the form of LiNi0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
In addition, when the obtained material particles were measured by X-ray energy spectrum analysis, the Nd content at the center of the particles was about 0.75 wt%, the B content was about 0.28 wt%, and the Nd and B contents at the surface of the particles were not detected, indicating that NdNi0.8Co0.1Mn0.1O3And Li2B4O7Is distributed in a concentration gradient and has a particle center composition of about (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) 100:0.47:0.54 (molar ratio), and LiNi as the outermost portion0.8Co0.1Mn0.1O2Close to the theoretical ratio.
Example 2
A transition metal salt solution, an aqueous ammonia solution, an aqueous sodium hydroxide solution, a base solution, a neodymium sulfate solution and Li were prepared as described in example 12B4O7Dispersion, constant feed rate of transition metal salt, neodymium sulfate solution and Li2B4O7The feed rate of the dispersion was 80mL/h, the feed rates of the dispersion and the neodymium sulfate solution were decreased by 1.25mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 1, whereby a composition having a concentration gradient distribution of the center of the positive electrode material particles was obtained (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) 100:1:1 (molar ratio), at bestThe outer portion is (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.7. mu.m, and the tap density was 2.63g/cm3。
According to the positive electrode material obtained in example 2, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
In addition, by measuring the positive electrode material particles of example 2 by X-ray energy spectrum analysis, the material particles were found to have a central Nd content of about 1.71 wt%, a B content of about 0.49 wt%, and surface Nd and B contents of 0.83 wt% and 0.25 wt%, respectively, indicating NdNi0.8Co0.1Mn0.1O3And Li2B4O7Is distributed in a concentration gradient, and has a composition of about (LiNi) converted into the center of the corresponding positive electrode material particle0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) At 100:1.2:1 (molar ratio), the outermost portion is approximately (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The obtained data were close to theoretical data (molar ratio of 100:0.52: 0.55), indicating that the target cathode material with concentration gradient modification was synthesized.
Example 3
A transition metal salt solution, an aqueous ammonia solution, an aqueous sodium hydroxide solution, a base solution, a neodymium sulfate solution and Li were prepared as described in example 12B4O7Dispersion, constant feed rate of transition metal salt, neodymium sulfate solution and Li2B4O7The dispersion feed rate was 80mL/h, and the dispersion and neodymium sulfate solution feed rates were decreased by 2 every half hour.5mL/h, and the other steps and experimental conditions were the same as in example 1, and the composition having a concentration gradient distribution of the center of the positive electrode material particles thus obtained was (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) At 100:1:1 (molar ratio), the outermost portion is LiNi0.8Co0.1Mn0.1O2. The particle size of the particles was 10.9. mu.m, and the tap density was 2.68g/cm3。
According to the positive electrode material obtained in example 3, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
The positive electrode material particles obtained in example 3 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) At a molar ratio of 100:1:1.1, the outermost portion is LiNi0.8Co0.1Mn0.1O2The obtained data is close to theoretical data, and the synthesis of the target cathode material with concentration gradient modification is illustrated.
Example 4
A transition metal salt solution, an aqueous ammonia solution, a base solution, an aqueous sodium hydroxide solution, a neodymium sulfate solution and Li were prepared as described in example 12B4O7Dispersion, constant feed rate of transition metal salt, neodymium sulfate solution and Li2B4O7The feed rate of the dispersion was 120mL/h, the feed rates of the dispersion and the neodymium sulfate solution were decreased by 3.75mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 1, whereby a composition having a concentration gradient distribution of the center of the positive electrode material particles was obtained (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) At a molar ratio of 100:1.5:1.5, the outermost portion is LiNi0.8Co0.1Mn0.1O2. The particle size of the particles was 10.8. mu.m, and the tap density was 2.63g/cm3。
According to the positive electrode material obtained in example 4, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
The positive electrode material particles obtained in example 4 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) 100:1.4:1.6 (molar ratio), the outermost portion is LiNi0.8Co0.1Mn0.1O2The obtained data is close to theoretical data, and the synthesis of the target cathode material with concentration gradient modification is illustrated.
Example 5
The transition metal salt solution, aqueous ammonia solution, aqueous sodium hydroxide solution, base solution and Li were prepared as described in example 12B4O7A dispersion and lanthanum sulfate (La) at a concentration of 0.05mol/L2(SO4)3) Solution, constant transition metal salt feed rate, lanthanum sulfate solution and Li2B4O7The feed rate of the dispersion was 80mL/h, the feed rates of the dispersion and the lanthanum sulfate solution were decreased by 1.25mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 1, whereby a composition having a concentration gradient distribution of the center of the positive electrode material particles was obtained (LiNi)0.8Co0.1Mn0.1O2)：(LaNi0.8Co0.1Mn0.1O3)：(Li2B4O7) At a molar ratio of 100:1:1, the outermost portion is (LiNi)0.8Co0.1Mn0.1O2)：(LaNi0.8Co0.1Mn0.1O3)：(Li2B4O7) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.9. mu.m, and the tap density was 2.65g/cm3。
According to the positive electrode material obtained in example 5, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2La is present in the form of LaNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
The positive electrode material particles obtained in example 5 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.8Co0.1Mn0.1O2)：(LaNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The outermost composition was about (LiNi) 100:0.9:0.90.8Co0.1Mn0.1O2)：(LaNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The obtained data were close to theoretical data (molar ratio) of 100:0.5:0.5, indicating that the target cathode material with concentration gradient modification was synthesized.
Example 6
The transition metal salt solution, aqueous ammonia solution, aqueous sodium hydroxide solution, base solution and Li were prepared as described in example 12B4O7A dispersion, and europium sulfate (Eu) at a concentration of 0.05mol/L2(SO4)3) With a constant feed rate of the transition metal salt, a europium sulfate solution and Li2B4O7The feed rate of the dispersion was 80mL/h, the feed rates of the dispersion and the europium sulfate solution were decreased by 1.25mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 1, whereby a composition having a concentration gradient distribution of the center of the particles of the positive electrode material (LiNi) was obtained0.8Co0.1Mn0.1O2)：(EuNi0.8Co0.1Mn0.1O3)：(Li2B4O7) At a molar ratio of 100:1:1, the outermost portion is (LiNi)0.8Co0.1Mn0.1O2)：(EuNi0.8Co0.1Mn0.1O3)：(Li2B4O7) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.7 μm and the tap density was 2.64g/cm3。
According to the positive electrode material obtained in example 6, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Eu being present in the form of EuNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
The positive electrode material particles obtained in example 6 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.8Co0.1Mn0.1O2)：(EuNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The outermost composition is about (LiNi) 100:1:1.20.8Co0.1Mn0.1O2)：(EuNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The obtained data were close to theoretical data (molar ratio of 100:0.48: 0.51), indicating that the target cathode material with concentration gradient modification was synthesized.
Example 7
A transition metal salt solution, an aqueous ammonia solution, an aqueous sodium hydroxide solution, a base solution and a neodymium sulfate solution were prepared as described in example 1, and Li having a particle size of 50nm was added2WO4Dispersed in water to prepare a 0.1mol/L dispersion. Constant transition metal salt feed rate, neodymium sulfate solution and Li2WO4The feed rate of the dispersion was 80mL/h, the feed rates of the dispersion and the neodymium sulfate solution were decreased by 1.25mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 1, whereby a composition having a concentration gradient distribution of the center of the positive electrode material particles was obtained (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2WO4) At a molar ratio of 100:1:1, the outermost portion is (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2WO4) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.8. mu.m, and the tap density was 2.60g/cm3。
According to the positive electrode material obtained in example 7, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3W is present in the form of Li2WO4。
The positive electrode material particles obtained in example 7 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2WO4) The outermost composition was about (LiNi) 100:1:0.9 (molar ratio)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2WO4) The obtained data were close to theoretical data (molar ratio of 100:0.53: 0.51), indicating that the target cathode material with concentration gradient modification was synthesized.
Example 8
A transition metal salt solution, an aqueous ammonia solution, a base solution, a neodymium sulfate solution were prepared as described in example 1, and Li having a particle size of 50nm was added3PO4Dispersed in water to prepare a 0.1mol/L dispersion. Constant transition metal salt feed rate, neodymium sulfate solution and Li3PO4The feed rate of the dispersion was 80mL/h, the feed rates of the dispersion and the neodymium sulfate solution were decreased by 1.25mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 1, whereby a composition having a concentration gradient distribution of the center of the particles of the positive electrode material (LiNi) was obtained0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li3PO4) At a molar ratio of 100:1:1, the outermost portion is (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li3PO4) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.8. mu.m, and the tap density was 2.53g/cm3。
According to the positive electrode material obtained in example 8, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3P is present in the form of Li3PO4。
The positive electrode material particles obtained in example 8 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li3PO4) The outermost composition was about (LiNi) 100:0.9:1.1 (molar ratio)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li3PO4) The obtained data were close to theoretical data when the molar ratio was 100:0.47:0.51, indicating that the target cathode material with concentration gradient modification was synthesized.
Example 9
Preparing a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the molar ratio of Ni to Co to Mn is 6:2:2, the concentration of nickel sulfate is 1.2mol/L, the concentration of cobalt sulfate is 0.4mol/L, and the concentration of manganese sulfate is 0.4 mol/L. The same aqueous ammonia solution, base solution, neodymium sulfate solution, and Li as in example 1 were prepared as in example 12B4O7Dispersion, etc., constant transition metal salt feed rate, neodymium sulfate solution and Li2B4O7The feed rate of the dispersion was 80mL/h, and the feed rates of the dispersion and neodymium sulfate solution were decreased by 1.25mL/h every half hour, depending on the species of lithiumLi is weighed out in an amount equal to the total amount of transition metal salt added minus the amount of rare earth metal salt added2CO3And after being mixed with the precursor, the mixture is placed into a tube furnace for secondary calcination, the calcination atmosphere is compressed air, the calcination temperature is 820 ℃, the calcination time is 12 hours, the target cathode material is obtained, the obtained cathode material with concentration gradient distribution has the same other steps and experimental conditions as those of the embodiment 1, and the composition of the particle center of the cathode material with concentration gradient distribution is (LiNi)0.6Co0.2Mn0.2O2)：(NdNi0.6Co0.2Mn0.2O3)：(Li2B4O7) At a molar ratio of 100:1:1, the outermost portion is (LiNi)0.6Co0.2Mn0.2O2)：(NdNi0.6Co0.2Mn0.2O3)：(Li2B4O7) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.8. mu.m, and the tap density was 2.61g/cm3。
According to the positive electrode material obtained in example 9, Li was present in the form of LiNi by XRD analysis0.6Co0.2Mn0.2O2Nd is present in the form of NdNi0.6Co0.2Mn0.2O3B is present in the form of Li2B4O7。
The positive electrode material particles obtained in example 9 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.6Co0.2Mn0.2O2)：(NdNi0.6Co0.2Mn0.2O3)：(Li2B4O7) The outermost composition was about (LiNi) 100:1.1:1.1 (molar ratio)0.6Co0.2Mn0.2O2)：(NdNi0.6Co0.2Mn0.2O3)：(Li2B4O7) The obtained data were close to theoretical data (molar ratio of 100:0.49: 0.52), indicating that the target cathode material with concentration gradient modification was synthesized.
Example 10
Preparing a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the molar ratio of Ni to Co to Mn is 5:2:3, the concentration of nickel sulfate is 1.0mol/L, the concentration of cobalt sulfate is 0.4mol/L, and the concentration of manganese sulfate is 0.6 mol/L. The same aqueous ammonia solution, sodium hydroxide solution, base solution, neodymium sulfate solution and Li as in example 1 were prepared as in example 12B4O7Dispersion, constant feed rate of transition metal salt, neodymium sulfate solution and Li2B4O7The feed rate of the dispersion was 80mL/h, the feed rates of the dispersion and the neodymium sulfate solution were decreased by 1.25mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 9, whereby a composition having a concentration gradient distribution of the center of the positive electrode material particles was obtained (LiNi)0.5Co0.2Mn0.3O2)：(NdNi0.5Co0.2Mn0.3O3)：(Li2B4O7) At a molar ratio of 100:1:1, the outermost portion is (LiNi)0.5Co0.2Mn0.3O2)：(NdNi0.5Co0.2Mn0.3O3)：(Li2B4O7) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.9. mu.m, and the tap density was 2.62g/cm3。
According to the positive electrode material obtained in example 10, Li was present in the form of LiNi by XRD analysis0.5Co0.2Mn0.3O2Nd is present in the form of NdNi0.5Co0.2Mn0.3O3B is present in the form of Li2B4O7。
The positive electrode material particles obtained in example 10 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)0.5Co0.2Mn0.3O2)：(NdNi0.5Co0.2Mn0.3O3)：(Li2B4O7) The outermost composition was about (LiNi) 100:0.9:1.2 (molar ratio)0.5Co0.2Mn0.3O2)：(NdNi0.5Co0.2Mn0.3O3)：(Li2B4O7) The obtained data were close to theoretical data (molar ratio of 100:0.53: 0.47), indicating that the target cathode material with concentration gradient modification was synthesized.
Example 11
Preparing a mixed solution of nickel sulfate, cobalt sulfate and manganese sulfate, wherein the molar ratio of Ni to Co to Mn is 1:1:1, the concentration of nickel sulfate is 2/3mol/L, the concentration of cobalt sulfate is 2/3mol/L, and the concentration of manganese sulfate is 2/3 mol/L. An aqueous ammonia solution, a sodium hydroxide solution, a base solution, a neodymium sulfate solution and Li were prepared as described in example 12B4O7Dispersion, constant feed rate of transition metal salt, neodymium sulfate solution and Li2B4O7The feed rate of the dispersion was 80mL/h, the feed rates of the dispersion and the neodymium sulfate solution were decreased by 1.25mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 9, whereby a composition having a concentration gradient distribution of the center of the positive electrode material particles was obtained (LiNi)1/3Co1/3Mn1/3O2)：(NdNi1/3Co1/3Mn1/3O3)：(Li2B4O7) At a molar ratio of 100:1:1, the outermost portion is (LiNi)1/3Co1/3Mn1/3O2)：(NdNi1/3Co1/3Mn1/3O3)：(Li2B4O7) When the molar ratio is 100:0.5:0.5 (molar ratio). The particle size of the particles was 10.8. mu.m, and the tap density was 2.66g/cm3。
According to the positive electrode material obtained in example 11, Li was present in the form of LiNi by XRD analysis1/3Co1/3Mn1/ 3O2Nd is present in the form of NdNi1/3Co1/3Mn1/3O3B is present in the form of Li2B4O7。
The positive electrode material particles obtained in example 11 were measured by X-ray energy spectrum analysis, and the composition of the center of the positive electrode material particle was about (LiNi)1/3Co1/3Mn1/3O2)：(NdNi1/3Co1/3Mn1/3O3)：(Li2B4O7) The outermost composition was about (LiNi) 100:1.2:0.8 (molar ratio)1/3Co1/3Mn1/3O2)：(NdNi1/3Co1/3Mn1/3O3)：(Li2B4O7) The obtained data are close to theoretical data when the molar ratio is 100:0.48:0.50, which indicates that the target cathode material with concentration gradient modification is synthesized.
Comparative example 1
A transition metal salt solution, an aqueous ammonia solution, a sodium hydroxide solution, a base solution, a neodymium sulfate solution and Li were prepared as described in example 12B4O7Dispersion, constant feed rate of transition metal salt, neodymium sulfate solution and Li2B4O7The dispersion was fed at a rate of 80mL/h and the feed rate was not changed, and the other steps and experimental conditions were the same as those of example 1, whereby the composition of the center and the outermost portion of the positive electrode material particles was (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) 100:1:1 (molar ratio). The particle size of the particles was 10.8. mu.m.
According to the positive electrode material obtained in comparative example 1, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
The positive electrode material particles of comparative example 1 were subjected to X-ray energy spectrum analysis and measurement to obtain a positive electrode material particle having a composition of about the center (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The outermost composition was about (LiNi) 100:1:1.1 (molar ratio)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) When the molar ratio was 100:0.9:1, the composition of the particle center and the outermost portion was consistent, and no concentration gradient was formed, indicating that the target positive electrode material was synthesized.
Comparative example 2
A transition metal salt solution, an aqueous ammonia solution, an aqueous sodium hydroxide solution and a base solution were prepared as described in example 1, except that a neodymium sulfate solution and Li were not added2B4O7The dispersion was subjected to the same experimental conditions as in example 1 without performing the first calcination step, and the composition of the obtained positive electrode material was LiNi0.8Co0.1Mn0.1O2. The particle size of the particles was 10.7. mu.m.
By XRD analysis, according to the positive electrode material obtained in comparative example 2, Li was present in the form of LiNi0.8Co0.1Mn0.1O2。
The positive electrode material particles in comparative example 2 were subjected to X-ray energy spectrum analysis and measurement to obtain positive electrode material particles having a composition of only LiNi at the center thereof0.8Co0.1Mn0.1O2The outermost composition being LiNi only0.8Co0.1Mn0.1O2The synthesis of the target positive electrode material is described.
Comparative example 3
Transition metal salt solution, Li, was formulated as described in example 12B4O7Dispersion, aqueous ammonia solution, aqueous sodium hydroxide solution, base solution, and the like. Without addition of neodymium sulfate solution, without carrying out the first calcination step, Li2B4O7The composition of the center of the positive electrode material particle having a concentration gradient distribution obtained was (LiNi) with the same experimental conditions as in example 1 except that the feed rate of the dispersion was 80mL/h and the feed rate of the dispersion was decreased by 1.25mL/h every half hour at the time of feeding the positive electrode material particle0.8Co0.1Mn0.1O2)：(Li2B4O7) 100:1 (molar ratio), the external composition is (LiNi)0.8Co0.1Mn0.1O2)：(Li2B4O7) 0.5 (molar ratio) to 100. The particle size of the particles was 10.8. mu.m.
By XRD analysis, according to the positive electrode material obtained in comparative example 3, Li was present in the form of LiNi0.8Co0.1Mn0.1O2B is present in the form of Li2B4O7。
The positive electrode material particles of comparative example 3 were subjected to X-ray energy spectrum analysis and measurement to obtain positive electrode material particles having a composition of about the center (LiNi)0.8Co0.1Mn0.1O2)：(Li2B4O7) The outermost composition was about (LiNi) 100:0.9 (molar ratio)0.8Co0.1Mn0.1O2)：(Li2B4O7) The obtained data was close to the theoretical data at 100:0.52 (molar ratio), indicating that the target cathode material was synthesized.
Comparative example 4
A transition metal salt solution, a neodymium sulfate solution, an aqueous ammonia solution, an aqueous sodium hydroxide solution and a base solution were prepared as described in example 1. Without addition of Li2B4O7The composition of the center of the positive electrode material particle having a concentration gradient distribution obtained was (LiNi) in the same manner as in example 1 except that the dispersion was fed at a neodymium sulfate solution feed rate of 80mL/h and the neodymium sulfate solution feed rate was decreased by 1.25mL/h every half hour during feeding, and the other experimental conditions were the same as in example 10.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3) 100:1 (molar ratio), the external composition is (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3) The particle size was 10.9 μm, 100:0.5 (molar ratio).
According to the positive electrode material obtained in comparative example 4, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3。
The positive electrode material particles of comparative example 4 were subjected to X-ray energy spectrum analysis and measurement to obtain positive electrode material particles having a composition of about the center (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3) The outermost composition was about (LiNi) 100:1.1 (molar ratio)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3) The obtained data are close to theoretical data when the molar ratio is 100:0.50, and the synthesis of the target positive electrode material is demonstrated.
Comparative example 5
The same transition metal salt solution, aqueous ammonia solution, aqueous sodium hydroxide solution, base solution, neodymium sulfate solution and Li as in example 1 were prepared as described in example 12B4O7Dispersion, constant feed rate of transition metal salt, neodymium sulfate solution and Li2B4O7The feed rate of the dispersion was 180mL/h, the feed rates of the dispersion and the neodymium sulfate solution were decreased by 2.5mL/h every half hour during feeding, and the other steps and experimental conditions were the same as those in example 1, whereby a composition having a concentration gradient distribution of the center of the positive electrode material particles was obtained (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The outermost composition was (LiNi) 100:2.25:2.25 (molar ratio)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) 100:1:1 (molar ratio). The particle size of the particles was 10.8. mu.m.
According to the positive electrode material obtained in comparative example 5, Li was present in the form of LiNi by XRD analysis0.8Co0.1Mn0.1O2Nd is present in the form of NdNi0.8Co0.1Mn0.1O3B is present in the form of Li2B4O7。
The positive electrode material particles of comparative example 5 were subjected to X-ray energy spectrum analysis and measurement to obtain positive electrode material particles having a composition of about the center (LiNi)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The outermost composition was about (LiNi) 100:2.2:2.3 (molar ratio)0.8Co0.1Mn0.1O2)：(NdNi0.8Co0.1Mn0.1O3)：(Li2B4O7) The obtained data are close to theoretical data (molar ratio) 100:1:1.1, which indicates that the target cathode material with concentration gradient modification is synthesized.
Mixing the positive electrode materials described in examples 1 to 11 and comparative examples 1 to 5 with a conductive agent super P and a binder PVDF in a ratio of 8:1:1, uniformly grinding, coating the ground mixture on an aluminum foil current collector, placing the aluminum foil current collector in a vacuum oven, drying at the temperature of 80 ℃ for 12 hours to prepare a positive electrode plate, cutting the positive electrode plate into a circle with a certain size by using a punch, and using 1mol/L LiPF as an electrolyte6The battery is a button cell assembled by adopting a Clegard model 2400 diaphragm and a lithium sheet as a negative electrode in the solution of EC/DEC/DMC 1:1: 1.
Electrochemical performance test conditions: and performing constant current charge and discharge test on the button cell at the constant temperature of 25 ℃, wherein the voltage range is 2.8-4.3V.
Rate capability: after 5 activations at 0.1C, charge and discharge tests were performed at 0.2C, 0.5C, 2C, 5C, 10C and the discharge capacity after the first cycle was recorded (data in table 1).
TABLE 1 specific discharge capacity under different multiplying power conditions
Figure GDA0003185157170000151
Cycle performance: the charge and discharge tests were carried out at 0.2C, 2C, 10C, and the discharge capacity after 50 cycles was recorded
TABLE 2 specific discharge capacity under different multiplying power conditions after 50 cycles
Figure GDA0003185157170000152
Figure GDA0003185157170000161
Testing the internal resistance of the battery: and performing EIS test on the batteries made of the anode materials obtained in different embodiments, performing fitting analysis, and obtaining the internal resistance of the anode material according to the equivalent circuit. The voltage at the output of the EIS test is 3.5V. Table 3 shows the internal resistance values (Rct/Ω) of the cell materials after 50 cycles at 0.1C and 10C rates.
TABLE 3 internal resistance of battery after 50 cycles of charge and discharge
Figure GDA0003185157170000162
According to the data in tables 1 to 3, comparing examples 1 to 4 with comparative example 1, it can be seen that after 50 cycles, the specific discharge capacity of examples 1 to 4 at different rates is much higher than that of comparative example 1 and the internal resistance of the battery is much lower than that of comparative example 1, which indicates that when the modified material is uniformly distributed, no battery material is far from being in gradient distribution, and the modification effect is good because when the modified material is uniformly distributed, the inside of the battery material needs longer time to realize the de-intercalation and the return of lithium ions, and under the long cycle condition, the internal and external discharge degrees are not consistent, so that the stress of the battery material is not uniform, the stable structure of the battery material is damaged, and the electrochemical performance is seriously reduced. Comparing example 2 with comparative examples 3 and 4, it was found that when only perovskite oxide or fast ion conductor is modified, the electrochemical performance is much smaller than that of the battery material modified by both perovskite oxide and fast ion conductor, indicating that the use of two modified substances to enhance the ionic conductivity and conductivity inside the material is capable of significantly enhancing the electrochemical performance of the material. According to the comparison of the data of examples 1 to 4, the modification effect is best when the modified substances are distributed in a gradient manner in the battery material and part of the modified substances are still present on the surface of the battery material. It can be seen from examples 2 to 8 that the different types of perovskite oxides and fast ion conductors used in the experiments have little difference in the performance of the battery material, and the combination of the perovskite oxides and the fast ion conductors results in the selection of NdNi0.8Co0.1Mn0.1O3And Li2WO4The modified substance is most effective. Comparing examples 1 and 2 with comparative example 5, it can be seen that the electrochemical performance of examples 1 and 2 is much better than that of comparative example 5, because comparative example 5 contains too much modification material, destroying the inherent structure of the positive electrode material to some extent, and thus comparative example 5 has a serious battery performance degradation phenomenon under long cycle conditions.
In conclusion, the internal resistance of the lithium ion battery cathode material modified by the fast ion conductor and the perovskite type oxide concentration gradient after 50 cycles is far smaller than that of the unmodified cathode material, and the discharge capacity of the lithium ion battery cathode material under high-rate long cycles is higher than that of the unmodified cathode material; the cycle performance of the anode material modified by the concentration gradient is far better than that of the anode material uniformly modified inside and outside; the cathode material jointly modified by the fast ion conductor and the perovskite type oxide is superior to the cathode material singly modified by the fast ion conductor or the perovskite type oxide; the proper increase of the content of the modifier is also beneficial to improving the rate and the cycle performance of the battery.

Claims (18)

1. A positive electrode material for a lithium ion battery is LiNiaCobMncO2A mixture of a rare earth element-containing perovskite oxide and a fast ion conductor, wherein a + b + c is 1, 0.2<a<0.95，0.05<b<0.5, and 0.05<c<0.5；
The mixture is in a granular form, and the concentration of the rare earth element-containing perovskite oxide and the fast ion conductor in the granules of the mixture is in a gradient distribution, the concentration of the rare earth element-containing perovskite oxide and the fast ion conductor in the granules gradually decreases from the center to the outside of the granules of the mixture,
and, at the center of the particles of the mixture, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0.1-2): (0.1 to 2) of,
in the mixtureOf the particles of (2), LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0-1): (0 to 1).
2. The positive electrode material according to claim 1, wherein a + b + c is 1, 0.3< a <0.9, 0.05< b <0.35, and 0.05< c < 0.35.
3. The positive electrode material according to claim 1,
at the center of the particles of the mixture, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0.2-1.8): (0.2 to 1.8), and
at the outermost part of the particles of the mixture, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0-0.8): (0 to 0.8).
4. The positive electrode material according to claim 3,
at the center of the particles of the mixture, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0.3-1.6): (0.3 to 1.6), and
at the outermost part of the particles of the mixture, LiNiaCobMncO2The molar ratio of the perovskite oxide containing the rare earth elements to the fast ion conductor is 100: (0-0.5): (0 to 0.5).
5. The positive electrode material according to any one of claims 1 to 4,
the perovskite oxide containing the rare earth element is RNidCoeMnfO3，
Wherein R represents a rare earth element;
d + e + f is 1, 0.2< d <0.95, 0.05< e <0.5, and 0.05< f < 0.5;
the LiNiaCobMncO2Is selected from LiNi0.8Co0.1Mn0.1O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.5Co0.2Mn0.3O2Or LiNi1/3Co1/3Mn1/3O2One or more of (a) or (b),
the fast ion conductor is selected from Li2WO4、LiAlO2、Li4SiO4、LiNbO3、Li2B4O7Or Li3PO4One or more of;
the fast ion conductor is dispersed in the form of nanoparticles in the particles of the mixture.
6. The positive electrode material according to claim 5,
r is selected from lanthanum, cerium, neodymium, ytterbium or europium;
d + e + f is 1, 0.3< d <0.9, 0.05< e <0.35, and 0.05< f < 0.35.
7. The positive electrode material according to claim 5,
the perovskite type oxide containing rare earth elements is selected from NdNi0.8Co0.1Mn0.1O3、LaNi0.8Co0.1Mn0.1O3、EuNi0.8Co0.1Mn0.1O3、NdNi0.6Co0.2Mn0.2O3、NdNi0.5Co0.2Mn0.3O3、NdNi1/3Co1/3Mn1/3O3One or more of (a).
8. The positive electrode material according to claim 5, wherein the particle size of the fast ion conductor is 10 to 100 nm.
9. The positive electrode material according to claim 5, wherein the particle size of the fast ion conductor is 40 to 60 nm.
10. The positive electrode material according to claim 1,
the median particle diameter of the anode material is 3-20 mu m, and the tap density is 2-3 g/cm3。
11. A method for producing the positive electrode material according to any one of claims 1 to 10, comprising the steps of:
1) preparing a mixed aqueous solution of nickel salt, cobalt salt and manganese salt, wherein the weight ratio of nickel: cobalt: the molar ratio of manganese is a: b: c;
2) preparing a water solution of rare earth metal salt;
3) preparing an aqueous dispersion of fast ionic conductor nanoparticles;
4) adding an alkaline water solution with the pH value of 11-14 into a reactor in an inert atmosphere, then adding a complexing agent water solution, and heating to 40-70 ℃;
5) dropwise adding the mixed aqueous solution of nickel salt, cobalt salt and manganese salt into a reactor at a constant speed, dropwise adding the aqueous solution of rare earth metal salt and the aqueous dispersion of the fast ion conductor into the reactor at a deceleration, dropwise adding a complexing agent and an alkali solution, and controlling the molar ratio, the concentration and the pH value of each component by controlling the feeding speed;
6) obtaining a reaction product after the reaction is finished, and obtaining a precursor with a concentration gradient doping substance after filter pressing, washing and drying;
7) calcining the precursor for the first time in a gas-in state, wherein the calcining temperature is 400-900 ℃, the calcining time is 1-10 hours, and the gas is air or oxygen;
8) uniformly mixing the product obtained in the step 7) with a lithium compound, introducing air to calcine the obtained mixture, wherein the calcining temperature is 400-1000 ℃, and the calcining time is 2-15 hours, so as to obtain the cathode material LiNiaCobMncO2The gas is air or oxygen，
Wherein a + b + c is 1, 0.2< a <0.95, 0.05< b <0.5, and 0.05< c < 0.5.
12. The production method according to claim 11, wherein,
in the step 1), the concentration of nickel ions in the mixed aqueous solution of the nickel salt, the cobalt salt and the manganese salt is 0.1-3 mol/L;
in the step 2), the concentration of the aqueous solution of the rare earth metal salt is 0.01-2 mol/L;
in the step 3), the concentration of the aqueous dispersion of the fast ion conductor nano particles is 0.01-0.2 mol/L;
in the step 4), heating to 50-60 ℃; the concentration of a complexing agent in the reactor is 0.2-2 mol/L;
in the step 5), the pH value is controlled to be 10-13;
in the step 7), the calcining temperature is 400-500 ℃, the calcining time is 1-3 hours, and the gas is oxygen;
in the step 8), the calcining temperature is 750-950 ℃, the calcining time is 10-14 hours, and the gas is oxygen.
13. The production method according to claim 11, wherein,
in the step 1), the concentration of nickel ions in the mixed aqueous solution of the nickel salt, the cobalt salt and the manganese salt is 0.5-2.5 mol/L;
in the step 2), the concentration of the aqueous solution of the rare earth metal salt is 0.01-0.2 mol/L;
in the step 3), the concentration of the aqueous dispersion of the fast ion conductor nano particles is 0.01-0.1 mol/L;
in the step 4), the concentration of the complexing agent in the reactor is 0.4-0.6 mol/L;
in the step 5), the pH value is controlled to be 11-12.
14. The production method according to claim 11, wherein,
the nickel salt, the cobalt salt and the manganese salt are respectively and independently selected from sulfate, nitrate or chloride salt;
the rare earth metal salt is selected from sulfate, nitrate or chloride salt;
the fast ion conductor is selected from Li2WO4、LiAlO2、Li4SiO4、LiNbO3、Li2B4O7Or Li3PO4One or more of;
the alkaline aqueous solution in the step 4) is a sodium hydroxide aqueous solution and/or a potassium hydroxide aqueous solution, the complexing agent is one or more selected from ammonia, urea, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium sulfate or ammonium acetate,
the water used for preparing the aqueous solution is deoxygenated water.
15. The production method according to claim 14,
the rare earth metal is selected from lanthanum, cerium, neodymium, ytterbium or europium;
the particle size of the fast ion conductor particles is 10-100 nm;
the complexing agent in the step 4) is one or more selected from ammonia water or urea.
16. The production method according to claim 11, wherein,
in step 8), the amount of substance of lithium in the lithium compound is equal to the amount of the total substance of nickel, cobalt and manganese added minus the amount of the substance of the rare earth metal added; the lithium compound is one or more selected from lithium hydroxide or lithium carbonate.
17. A positive electrode of a lithium ion battery comprising the positive electrode material according to any one of claims 1 to 10.
18. A lithium ion battery comprising the cathode of claim 17.
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