CN114628649B - Preparation method and application of cobalt-supplementing high-nickel low-cobalt ternary cathode material - Google Patents

Preparation method and application of cobalt-supplementing high-nickel low-cobalt ternary cathode material Download PDF

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CN114628649B
CN114628649B CN202110819976.1A CN202110819976A CN114628649B CN 114628649 B CN114628649 B CN 114628649B CN 202110819976 A CN202110819976 A CN 202110819976A CN 114628649 B CN114628649 B CN 114628649B
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cobalt
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CN114628649A (en
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肖彪彪
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Wanxiang A123 Systems Asia 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
    • H01M4/362—Composites
    • 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
    • H01M4/36—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
    • 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 relates to the field of lithium ion batteries, and discloses a preparation method and application of a cobalt-supplementing high-nickel low-cobalt ternary positive electrode material, wherein a compound of nano cobalt and the high-nickel low-cobalt ternary positive electrode material are stirred and mixed and sintered at high temperature to obtain the cobalt-supplementing high-nickel low-cobalt ternary positive electrode material; the high-nickel low-cobalt ternary positive electrode material is Li (Ni x Co y Mn 1‑x‑y )O 2 ，0.7≤x≤0.9，0<y is less than or equal to 0.1; the cobalt occupies Li (Ni x Co y Mn 1‑x‑y )O 2 The mass fraction of (2) is 0.1-0.6%; the cobalt-supplementing high-nickel low-cobalt ternary positive electrode material is prepared by punctiform modification of cobalt compound on Li (Ni) x Co y Mn 1‑x‑y )O 2 A monocrystalline surface. The surface punctiform modification of cobalt in the invention effectively solves the problem of the increase of initial DCR and circulating DCR, further improves the circulating performance of the battery, reduces the internal resistance, and saves the energy consumption and the cost.

Description

Preparation method and application of cobalt-supplementing high-nickel low-cobalt ternary cathode material
Technical Field
The invention relates to the field of lithium ion batteries, in particular to a preparation method and application of a cobalt-supplementing high-nickel low-cobalt ternary positive electrode material.
Background
Lithium nickel cobalt manganese oxide (Li (Ni) x Co y Mn 1-x-y )O 2 ) The positive electrode material, also called as ternary material, has the advantages of high energy density and good cycle performance, and is one of the most promising positive electrode materials of lithium ion batteries at present. The cobalt element in the material can stabilize the layered structure of the material, co 3+ The existence of the lithium ion battery reduces the mixing and discharging of cations and is convenient for the transmission of lithium ions and electrons, thereby playing the roles of improving the capacity, enhancing the cycle performance and the multiplying power performance and reducing the internal resistance of the battery on the battery level.
The continuous rising price of cobalt raw materials is caused by the relatively low stock of the global cobalt ores, the large exploitation difficulty and the uneven distribution and the great demand of the lithium battery industry for cobalt. In order to reduce the cost and the dependence on scarce cobalt resources, the trend of the ternary materials to lower cobalt is more and more evident.
At present, the low-cobalt route mostly reduces the cobalt content at the end of a precursor (nickel cobalt manganese hydroxide), and then the defects of poor battery cycle performance and high internal resistance caused by low-cobalt materials are overcome by bulk doping (such as Zr doping) and surface modification (such as Al cladding) of other elements at the later stage. However, the method can only make up for the limitThe recycling problem caused by low cobalt (especially low temperature recycling) and the high internal resistance problem are still high in comprehensive cost (yuan/watt hour). Therefore, a strategy of late cobalt supplementation in low cobalt materials is formed, and Chinese patent publication No. CN106532006A discloses a preparation method of a cobalt oxide coated ternary positive electrode material, wherein the chemical general formula of the positive electrode material is Li (Ni x Co y Mn 1-x-y )O 2 ，0.5≤x≤0.9，0<y≤0.3，0<The mixing mole ratio of the cobalt coating is Co, wherein 1-x-y is less than or equal to 0.2: li (Ni) x Co y Mn 1-x-y )O 2 The method comprises the steps of synthesizing a ternary positive electrode material precursor through coprecipitation, preparing the ternary positive electrode material through high-temperature sintering, coating a nano cobalt oxide solid phase and the like. The method has the defects that the cobalt content of the used ternary positive electrode material is high, the molar ratio of cobalt coating is also high, the energy conservation and the cost saving are not facilitated, and the performance of the ternary positive electrode material is affected by the excessive coating amount.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method and application of a cobalt-supplementing high-nickel low-cobalt ternary positive electrode material, wherein the surface punctiform modification of a cobalt compound keeps the original high energy density and capacity of the positive electrode active material, so that the circulation problem and the high internal resistance problem caused by the high-nickel low-cobalt ternary positive electrode material are overcome, and the energy conservation and the cost conservation are facilitated.
The specific technical scheme of the invention is as follows:
in a first aspect, the invention provides a preparation method of a surface punctiform modification cobalt-supplementing high-nickel low-cobalt ternary positive electrode material, which comprises the following steps:
stirring and mixing a mixture of a compound of nano cobalt and a compound of nano aluminum or a compound of nano cobalt and a ternary positive electrode material of high nickel and low cobalt, and sintering at a high temperature of 600-900 ℃ to obtain a ternary positive electrode material of high nickel and low cobalt of cobalt supplementing type;
the high-nickel low-cobalt ternary positive electrode material is Li (Ni x Co y Mn 1-x-y )O 2 ，0.7≤x≤0.9，0<y≤0.1；
The cobalt occupies Li (Ni x Co y Mn 1-x-y )O 2 The mass fraction of (2) is 0.1-0.6%;
the aluminum occupies Li (Ni x Co y Mn 1-x-y )O 2 The mass fraction of (2) is 0.05-0.13%;
the cobalt-supplementing high-nickel low-cobalt ternary positive electrode material is prepared by modifying cobalt compound and aluminum or cobalt compound in a dot form in Li (Ni x Co y Mn 1-x-y )O 2 A monocrystalline surface.
The high-nickel low-cobalt ternary positive electrode material is a lithium nickel cobalt manganese oxide positive electrode material with extremely low cobalt content, and a high-temperature sintering method is adopted to compensate a very small amount of cobalt element, so that a ternary single crystal material with punctiform surface modification is formed. The surface punctiform modification of the nano cobalt compound can effectively solve the problem of increase of initial direct current internal resistance (DCR) and circulating direct current internal resistance (DCR), and overcome the defect that bulk doping of other elements (such as W, ti, zr and Sr elements) cannot solve the DCR problem of the low cobalt material. The dot-shaped modification is realized by changing the surface energy distribution of the high-nickel low-cobalt ternary positive electrode material and forming a fast ion conductor and a protective layer on the surface of the material, so that the transmission of lithium ions and electrons is easier, the cycle performance is better, the internal resistance is lower, and the structure can further enhance the structural stability of the material. Meanwhile, compared with a structure with the surface completely coated, the punctiform modification of the surface of the nano cobalt compound does not reduce the duty ratio of the positive electrode active material, and keeps the original high energy density and capacity exertion of the high-nickel low-cobalt ternary positive electrode material. And finally, the comprehensive performance of the high-nickel low-cobalt ternary positive electrode material is improved, the energy consumption and the cost are reduced, and the effect of the high-nickel low-cobalt ternary positive electrode material in a power battery is enlarged.
The cobalt-supplementing high-nickel low-cobalt ternary positive electrode material obtained by punctiform modification of the common surfaces of the cobalt compound and the aluminum compound has better comprehensive performance, mainly because an Li-Al-Co-O protective layer is formed on the surface of the material by the aluminum element and the cobalt element during operation, the protective layer can resist corrosion of HF on the active material, effectively prevent metal ions in the material from being dissolved in electrolyte, improve the structural stability of the material under high voltage and improve the cycle performance of a battery.
Preferably, the high-nickel low-cobalt ternary positive electrode material is Li (Ni 0.75 Co 0.05 Mn 0.2 )O 2 。
Li(Ni 0.75 Co 0.05 Mn 0.2 )O 2 The cobalt content of the cobalt can lead the surface punctiform modification effect of the subsequent cobalt compound to be better, and the method is more in line with the trend of low cobalt, and reduces the dependence on scarce cobalt resources on the premise of not influencing the performance.
Preferably, the cobalt occupies Li (Ni x Co y Mn 1-x-y )O 2 Is 0.3% by mass, and the aluminum occupies Li (Ni x Co y Mn 1-x-y )O 2 Is 0.1% by mass.
Cobalt to Li (Ni) x Co y Mn 1-x-y )O 2 When the mass fraction of the cobalt is 0.3%, the punctiform modification effect of the cobalt compound on the surface of the high-nickel low-cobalt ternary cathode material is better, and the problem of the increase of the initial DCR and the circulating DCR can be effectively solved. Too large mass fraction of cobalt causes excessive modification, but reduces the duty ratio of the positive electrode active material, and too small mass fraction of cobalt causes too little modification, which is insufficient to remarkably improve internal resistance and cycle performance.
Preferably, the cobalt compound is one or more of cobaltosic oxide, cobalt hydroxide and cobalt oxide. Tricobalt tetraoxide is preferred.
Preferably, the cobaltosic oxide is used as a reactant, and the high-nickel low-cobalt ternary positive electrode material and the cobaltosic oxide are subjected to contact interface reaction by high-temperature sintering to generate lithium cobaltate, so that the cobaltosic oxide can form firm combination with the lithium nickel cobalt manganese oxide. Although cobalt hydroxide decomposes to tricobalt tetraoxide during sintering, it is less efficient to produce lithium cobaltate during high temperature sintering, as is cobalt oxide, resulting in lower binding rates with high nickel low cobalt ternary cathode materials.
Preferably, the aluminum compound is one of aluminum oxide and aluminum hydroxide. Preferably alumina.
The alumina has high temperature resistance, better structural stability and better heat absorption performance, and can improve the cycle performance and the safety performance of the anode material in the working process.
Preferably, the uniform stirring and mixing are secondary stirring, wherein the stirring speed of the first time is 400-600 r/min, the stirring time is 6-8 min, the stirring speed of the second time is 1400-1600 r/min, and the stirring time is 8-12 min; the sintering time at the high temperature is 4-8 h. The preferred first stirring rate is 500r/min for 7min, and the second stirring rate is 1500r/min for 10min.
The first stirring is low-speed stirring, so as to ensure that the materials are primarily mixed and prevent particle agglomeration; the second stirring is high-speed stirring, so that the particles can be fully mixed, and the reaction efficiency is improved.
The invention also provides a solid lithium battery, which comprises a positive electrode and a negative electrode, and is characterized in that the positive electrode comprises the positive electrode material prepared by the preparation method of the dot-shaped modified cobalt-supplementing high-nickel low-cobalt ternary positive electrode material in any one of claims 1-6; the negative electrode comprises nano silicon composite particles and LATP; the nano silicon composite particles are N-P-COF-GO modified nano silicon composite particles, COF and GO are loaded on the surfaces of the silicon nano particles, and N and P are co-doped in the COF and GO.
The Covalent Organic Framework (COF) is a stable and ordered porous framework structure, and after being compounded with the nano silicon particles, the Covalent Organic Framework (COF) relieves and inhibits the severe volume change of the nano silicon particles, reduces the generation of a surface SEI film, and meanwhile, a large number of redox active centers and long-range ordered open channels exist in the COF, so that the diffusion path of lithium ions is more convenient, and the electrochemical performance of the battery is more excellent.
Meanwhile, graphene Oxide (GO) has excellent lithium ion transmission performance, and the addition of graphene oxide can also increase the conductivity of silicon particles. COF possesses high mechanical strength because of its orderly porous skeleton, and GO mechanical strength is lower, and the compound of COF and GO has formed the lithium ion transmission passageway of just gentle combination, can realize lithium ion's quick transmission and storage under the circumstances that does not have big volume variation. The addition of COF and GO can also buffer particle pulverization and SEI film continuous growth caused by the volume expansion of silicon particles, prolong the service life and improve the structure and chemical stability of the material.
Doping of the nitrogen source material (N) and the phosphorus source material (P) endows the COF and the GO with more topological defects and larger interlayer spacing, and further enhances the transmission performance of electrons and ions. Therefore, the solid lithium battery corresponding to the N-P-COF-GO modified nano silicon particles has lower alternating current impedance and higher discharge capacity and cycle performance.
Preferably, the preparation method of the negative electrode comprises the following steps:
dispersing silicon nano particles, a phosphorus source material, a nitrogen source material and graphene oxide in an organic solvent, and performing ultrasonic treatment at normal temperature; adding the obtained mixed solution into a Pyrex tube, adjusting the pH to 5-6, carrying out ultrasonic mixing again at normal temperature, then quickly freezing in liquid nitrogen, and degassing through thawing circulation; heating the Pyrex tube, filtering, washing the precipitate, removing impurities on the surface, and then carrying out vacuum drying and vacuum sintering; after cooling to room temperature, ball milling the obtained powder to obtain the nano silicon composite particles; and ball milling and pressing the nano silicon composite particles and the LATP again to obtain the negative electrode.
Preferably, the particle size of the silicon nanoparticle is 50-500 nm; the mass ratio of the silicon nano particles to the phosphorus source material to the nitrogen source material to the graphene oxide is (30-40): (0.001-0.003): (0.001-0.003): (0.5-2.0); the organic solvent comprises a solvent a and a solvent b, wherein the volume ratio of the solvent a to the solvent b is 2-3: 0.5 to 1; the ultrasonic duration at the normal temperature is 40-60 minutes; the solvent used for regulating the pH value to be 5-6 is one of acetic acid, citric acid, tartaric acid and malic acid; the ultrasonic mixing time is 20-40 minutes at normal temperature after the pH is regulated; the heating temperature in the Pyrex tube is 80-120 ℃ and the heating time is 24-60 hours; the filtered washing solvent is deionized water and ethanol; the vacuum drying temperature is 60 ℃, the vacuum drying time is 4-6 hours, the vacuum sintering temperature is 300-400 ℃, and the vacuum sintering time is 8-12 hours; the ball milling time is 10-30 minutes; the mass ratio of the nano silicon composite particles to the LATP is 8-10: 1.0 to 2.0; the ball milling time is 10-20 minutes again; the pressing condition is 50-200 standard atmospheric pressures.
As a further preference, the particle size of the silicon nanoparticle is 200nm; the mass ratio of the silicon nano particles to the phosphorus source material to the nitrogen source material to the graphene oxide is 35:0.002:0.002:0.7; the organic solvent comprises a solvent a and a solvent b, and the volume ratio of the solvent a to the solvent b is 2.5:0.7; the ultrasonic duration at the normal temperature is 50 minutes; the solvent used for adjusting the pH value to 5-6 is acetic acid; the ultrasonic mixing time is 30 minutes at normal temperature after the pH is adjusted; the heating temperature in the Pyrex tube is 1000 ℃ and the heating time is 45 hours; the filtered washing solvent is deionized water and ethanol; the vacuum drying temperature is 60 ℃, the vacuum drying time is 5 hours, the vacuum sintering temperature is 50 ℃, and the vacuum sintering time is 10 hours; the ball milling time is 20 minutes; the mass ratio of the nano silicon composite particles to the LATP is 9:1.5; the ball milling time is 15 minutes again; the pressing conditions were 150 atmospheres gauge.
Preferably, the phosphorus source material is phosphoenone pyruvic acid; the nitrogen source material is acrylamide; the solvent a is dioxane, and the solvent b is trimethylbenzene.
Acrylamide reacts for a long time (heating for 24-60 hours in the range of 80-120 ℃) in a high-temperature Pyrex tube to generate COF microcrystalline aggregates, and the acrylamide can form COF or be used as a nitrogen source to be doped in COF and GO. Acrylamide is used as a nitrogen source, ketene phosphate pyruvic acid is used as a phosphorus source, and a COF porous structure and a GO layered structure are doped in the vacuum sintering process at 300-400 ℃ to form a structure in which N and P are co-doped in COF and GO.
Compared with the prior art, the invention has the following technical effects:
(1) The surface of the cobalt compound is punctuated and modified on the high-nickel low-cobalt ternary positive electrode material, so that the problem of the increase of initial DCR and circulating DCR can be effectively solved, the transmission of lithium ions and electrons is easier by changing the surface energy distribution of the high-nickel low-cobalt ternary positive electrode material, and the original high energy density and capacity exertion of the high-nickel low-cobalt ternary positive electrode material are maintained;
(2) The common surface point of the cobalt compound and the aluminum compound is modified on the high-nickel low-cobalt ternary positive electrode material, so that the comprehensive performance is better, the structural stability of the material under high voltage can be improved, and the cycle performance of the battery is improved;
(3) Saving energy consumption and cost, simple operation and being capable of realizing industrial production.
Drawings
FIG. 1 is an SEM image of NCM7205-Co-800℃in example 1;
FIG. 2 is an SEM image of NCM7205-AlCo-800℃in example 2;
FIG. 3 is an SEM image of NCM7205-Al-700℃for comparative example 3;
FIG. 4 is an SEM image of nanoscale tricobalt tetraoxide;
fig. 5 is an SEM image of nano-scale alumina.
Detailed Description
The technical scheme of the present invention is described below by using specific examples, but the scope of the present invention is not limited thereto:
example 1
1. Precursor (Ni) 0.75 Co 0.05 Mn 0.2 )(OH) 2 Is prepared from
Adding 5L of deionized water and 1L of strong ammonia water into a reaction kettle, heating and stirring at 60 ℃, wherein the stirring speed is 700r/min; preparing a nickel-cobalt-manganese mixed salt solution to enable NiSO 4 、CoSO 4 And MnSO 4 Ni in the mixed solution: co: the molar ratio of Mn is 7.5:0.5:2; continuously pumping 2mol/L nickel-cobalt-manganese mixed salt solution, 2mol/L NaOH solution and concentrated ammonia water into a reaction kettle, wherein the feeding speeds of the nickel-cobalt-manganese mixed salt solution and the NaOH solution are respectively 0.25mL/min and 0.5mL/min, the pH value is set to be 11.2, and the nickel-cobalt-manganese mixed salt solution and the NaOH solution react under the nitrogen atmosphere; after the reaction is finished, the reaction solution continuously flows into an aging reaction kettle from an overflow port, and is washed by a suction filter and dried by a blast drying oven at 90 ℃ to obtain a precursor (Ni) 0.75 Co 0.05 Mn 0.2 )(OH) 2 A material.
2.Li(Ni 0.75 Co 0.05 Mn 0.2 )O 2 Is prepared from
Weighing 10000g of the precursor material prepared in the step 1 and a certain proportion of LiOH H 2 O, lithium metal ratio Li/Me of 1.05:1, mixing for 6 hours by a three-dimensional mixer; calcining the mixture in a tube furnace in an oxygen-enriched atmosphere, wherein the heating rate is 5 ℃/min, and calcining at the constant temperature of 900 ℃ for 9 hours to prepare the high-nickel low-cobalt ternary anode material Li (Ni) 0.75 Co 0.05 Mn 0.2 )O 2 。
3. Surface punctiform modification of cobalt compounds
1000g of Li (Ni 0.75 Co 0.05 Mn 0.2 )O 2 The material and the nano-scale cobaltosic oxide are shown in a surface topography diagram of the nano-scale cobaltosic oxide in FIG. 4, and the mass fraction of the cobaltosic oxide is 0.3%; uniformly stirring and mixing the mixture, wherein the stirring speed of the first time is 500r/min, the stirring time is 7min, and the stirring speed of the second time is 1500r/min, and the stirring time is 10min; then sintering for 6 hours at 800 ℃ to obtain the cobalt-supplementing high-nickel low-cobalt ternary positive electrode material (NCM 7205-Co-800 ℃). As shown in FIG. 1, the SEM image of the NCM7205-Co-800 ℃ material shows that nano-scale cobaltosic oxide is punctiform modified on the single crystal surface of the high-nickel low-cobalt ternary cathode material.
4. Testing positive electrode of solid-state lithium battery: the method comprises the following steps of preparing the cobalt-supplementing high-nickel low-cobalt ternary positive electrode material, acetylene black and PVDF in the step 3, wherein the mass ratio is 90:5:5.
And (3) a negative electrode: dispersing silicon nanoparticles, phosphoenolpyruvic acid, acrylamide and graphene oxide in an organic solvent, wherein the particle size of the silicon nanoparticles is 50nm (the purity is more than 99%), and the mass ratio of the silicon nanoparticles to the phosphoenolpyruvic acid to the acrylamide to the graphene oxide is 33:0.002:0.002:1.5, the volume ratio of the dioxane to the trimethylbenzene is 3: 1. And (3) carrying out ultrasonic treatment on the mixture at normal temperature for 60 minutes, adding the obtained mixed solution into a Pyrex tube, adjusting the pH to 5-6 by using acetic acid, wherein the concentration of the acetic acid is 5mol/L, and the molar ratio of the acetic acid to silicon is 20:3. Then, the mixture was sonicated at room temperature for 40 minutes, rapidly frozen in liquid nitrogen, and deaerated by a freeze pump thawing cycle. Heating the Pyrex tube at 90 ℃ for 45 hours, filtering, washing the precipitate with deionized water and ethanol, and removing impurities on the surface. Vacuum drying at 60 deg.c for 6 hr, and vacuum sintering at 300 deg.c for 12 hr. And after sintering, cooling to room temperature, putting the obtained powder into a high-energy vibration ball mill, and ball milling for 30 minutes at normal temperature to obtain the nano silicon composite particles. The mass ratio is 9: the 1.5 nanometer silicon composite particles and LATP are ball milled again for 15 minutes, and then pressed under 150 standard atmospheric pressures to obtain the negative electrode.
The positive and negative poles are installed into button cells for testing, and the electrolyte used is LiPF with the concentration of 1mol/L 6 The mass ratio of the components dissolved in the water is 1:1:1, and the test voltage is 2.7-4.25V in a mixed solution of Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and dimethyl carbonate.
Example 2
And (3) replacing nano cobaltosic oxide with nano cobalt oxide in the step (3), and preparing the cobalt-supplementing high-nickel low-cobalt ternary positive electrode material (NCM 7205-Co-600 ℃) at the high-temperature sintering temperature of 600 ℃ for 8 hours. The other conditions were the same as in example 1.
Example 3
And (3) replacing nano cobaltosic oxide with nano cobalt hydroxide in the step (3), wherein the high-temperature sintering temperature is 900 ℃ and the time is 4 hours, and preparing the cobalt-supplementing high-nickel low-cobalt ternary positive electrode material (NCM 7205-Co-900 ℃). The other conditions were the same as in example 1.
Example 4
The common surface point modification of the cobalt compound and the aluminum compound in the step 3 is changed into that of cobaltosic oxide and aluminum oxide, wherein the material is cobaltosic oxide and aluminum oxide, the mass fraction of the cobaltosic oxide is 0.3%, the mass fraction of the aluminum oxide is 0.1%, and the high-temperature sintering temperature is 800 ℃ and the time is 6 hours. The cobalt-supplementing high-nickel low-cobalt ternary positive electrode material (NCM 7205-AlCo-800 ℃) is prepared. The other conditions were the same as in example 1. As shown in FIG. 2, the SEM image of the NCM7205-AlCo-800 ℃ material shows that nano-scale cobaltosic oxide and aluminum oxide are commonly and punctiform modified on the single crystal surface of the high-nickel low-cobalt ternary cathode material.
Example 5
The common surface point modification of the cobalt compound and the aluminum compound in the step 3 is changed into that of cobaltosic oxide and aluminum oxide, wherein the material is cobaltosic oxide and aluminum oxide, the mass fraction of the cobaltosic oxide is 0.3%, the mass fraction of the aluminum oxide is 0.1%, and the high-temperature sintering temperature is 700 ℃ and the time is 6 hours. The cobalt-supplementing high-nickel low-cobalt ternary positive electrode material (NCM 7205-AlCo-700 ℃) is prepared. The other conditions were the same as in example 1.
Comparative example 1
In step 3, no cobalt compound or aluminum compound is added. Preparing the high-nickel low-cobalt ternary positive electrode material (NCM 7205-800 ℃). The other conditions were the same as in example 1.
Comparative example 2
In the step 3, no cobalt compound or aluminum compound is added, and the high-temperature sintering temperature is 700 ℃. The high nickel low cobalt ternary positive electrode material (NCM 7205-700 ℃) is prepared. The other conditions were the same as in example 1.
Comparative example 3
The surface punctiform modification of the compound changed from the step 3 into aluminum adopts nano-scale aluminum oxide, and the nano-scale aluminum oxide is shown in a surface topography diagram of the nano-scale aluminum oxide in a figure 5, wherein the mass fraction of the aluminum oxide is 0.1%, the high-temperature sintering temperature is 700 ℃, and the time is 6 hours. The aluminum-supplementing high-nickel low-cobalt ternary anode material (NCM 7205-Al-700 ℃) is prepared. The other conditions were the same as in example 1. As shown in FIG. 3, the SEM image of the NCM7205-Al-700 ℃ material shows that nano-scale alumina is punctiform modified on the single crystal surface of the high-nickel low-cobalt ternary cathode material.
Comparative example 4
In step 1, a precursor (Ni 0.7 Co 0.1 Mn 0.2 )(OH) 2 Preparing a nickel-cobalt-manganese mixed salt solution, and enabling Ni in a NiSO4, coSO4 and MnSO4 mixed solution to be: co: the molar ratio of Mn is 7:1:2; in step 2, li (Ni 0.7 Co 0.1 Mn 0.2 )O 2 Is prepared by the steps of (1); in step 3, no cobalt compound or aluminum compound is added. The high-nickel low-cobalt ternary positive electrode material (NCM 712-800 ℃) is prepared. The other conditions were the same as in example 1.
Comparative example 5
In step 1, a precursor (Ni 0.7 Co 0.1 Mn 0.2 )(OH) 2 Preparing a nickel-cobalt-manganese mixed salt solution to prepare NiSO 4 、CoSO 4 And MnS O4 Ni in the mixed solution: co: the molar ratio of Mn is 7:1:2; in step 2, li (Ni 0.7 Co 0.1 Mn 0.2 )O 2 Is prepared by the steps of (1); in the step 3, no cobalt compound or aluminum compound is added, and the high-temperature sintering temperature is 700 ℃. The high-nickel low-cobalt ternary positive electrode material (NCM 712-700 ℃) is prepared. The other conditions were the same as in example 1.
Comparative example 6
And (3) changing the cathode of the battery in the step (4) into a lithium sheet. The high-nickel low-cobalt ternary positive electrode material (NCM 7205-Co-800 ℃ (the negative electrode is a lithium sheet)) is prepared. The other conditions were the same as in example 1.
TABLE 1 Performance comparison of high Nickel Low cobalt ternary cathode materials prepared under different conditions
In the table 1, the contents of the components,
FDC@0.2C: a First Discharge Capacity (FDC) at a discharge rate of 0.2C (40 mA);
cyclic test conditions: the charge-discharge multiplying power is 0.5C (100 mA), and the cycle number is the number of turns when the capacity is attenuated to 80%;
initial discharge DCR (direct current internal resistance) test conditions: 50% SOC (state of capacity, capacity state), 5C (1000 mA) discharge rate discharge for 10s;
the cost calculation formula: cost=m (Li (OH) ·h 2 O)*P(Li(OH)·H 2 O)/a+m(NiSO 4 ·6(H 2 O))*P(NiSO 4 ·6(H 2 O))/a/b+m(CoSO 4 ·7(H2O))*P(CoSO 4 ·7(H 2 O))/a/b+m(MnSO 4 ·H 2 O)*P(MnSO 4 ·H 2 O)/a/b+P+Q; wherein m (X) represents the mass of X in 1kg of the final material, P (X) represents the unit price of X, a is the raw material utilization rate of the precursor end, a=97%, b is the raw material utilization rate of the sintering stage, and b=98%; p is the price of the coating agent, Q is the processing cost, q=45 yuan; the raw material price comes from the color screen 2021 of Shanghai, 5 month and 16 daysIs a price of (2); as shown in table 2.
TABLE 2 prices of different raw materials
Specific results are shown in table 1, and in combination with examples 1-3 and comparative examples 1-5, compared with the pure high-nickel low-cobalt ternary cathode material and the material subjected to surface punctiform modification by using only an aluminum compound, the surface punctiform modification of the cobalt compound can remarkably reduce internal resistance and can also improve discharge capacity, but the cost only has a small increase. The method is characterized in that the surface of the cobalt compound is punctiform modified on the high-nickel low-cobalt ternary cathode material, so that the problem of the increase of initial DCR and circulating DCR can be effectively solved, the circulating performance is improved, and the internal resistance is reduced. It is known from the combination of examples 1 and examples 4 to 5 that the common surface punctiform modification of the cobalt and aluminum compounds can further improve the cycle performance, and the combination performance of the ternary cathode material is better. Meanwhile, as can be seen from the combination of examples 1 to 5 and comparative example 1, the negative electrode prepared using the nano-silicon composite particles and the LATP can provide the corresponding solid lithium battery with lower alternating current resistance, higher discharge capacity and cycle performance.
The result shows that the method provided by the invention can be used for preparing the low-cost and high-performance cobalt-supplementing high-nickel low-cobalt ternary positive electrode material, finding out proper cobalt supplementing amount and sintering temperature, and solving the circulation problem and the internal resistance problem of the low-cobalt ternary single crystal material by coating with trace cobalt, and can be applied to the field of high-energy density automobile power batteries.
The raw materials and equipment used in the invention are common raw materials and equipment in the field unless specified otherwise; the methods used in the present invention are conventional in the art unless otherwise specified.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent transformation of the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

Claims (3)

1. The solid lithium battery comprises a positive electrode and a negative electrode, and is characterized in that the positive electrode comprises a dot-shaped modified cobalt-supplementing high-nickel low-cobalt ternary positive electrode material; the negative electrode comprises nano silicon composite particles and LATP; the nano silicon composite particles are N-P-COF-GO modified nano silicon composite particles, COF and GO are loaded on the surfaces of the silicon nano particles, and N and P are co-doped in the COF and GO;
the preparation method of the negative electrode comprises the following steps:
dispersing silicon nano particles, a phosphorus source material, a nitrogen source material and graphene oxide in an organic solvent, and performing ultrasonic treatment at normal temperature; adding the obtained mixed solution into a Pyrex tube, adjusting the pH to 5-6, carrying out ultrasonic mixing again at normal temperature, then quickly freezing in liquid nitrogen, and degassing through thawing circulation; heating the Pyrex tube, filtering, washing the precipitate, removing impurities on the surface, and then carrying out vacuum drying and vacuum sintering; after cooling to room temperature, ball milling the obtained powder to obtain the nano silicon composite particles; and ball milling and pressing the nano silicon composite particles and the LATP again to obtain the negative electrode.
2. A solid state lithium battery according to claim 1, wherein,
the particle size of the silicon nano particles is 50-500 nm;
the mass ratio of the silicon nano particles to the phosphorus source material to the nitrogen source material to the graphene oxide is (30-40): (0.001-0.003): (0.001-0.003): (0.5-2.0);
the organic solvent comprises a solvent a and a solvent b, wherein the volume ratio of the solvent a to the solvent b is 2-3: 0.5 to 1;
the ultrasonic duration at the normal temperature is 40-60 minutes;
the solvent used for regulating the pH value to be 5-6 is one of acetic acid, citric acid, tartaric acid and malic acid;
the ultrasonic mixing time is 20-40 minutes at normal temperature after the pH is regulated;
the heating temperature in the Pyrex tube is 80-120 ℃ and the heating time is 24-60 hours;
the filtered washing solvent is deionized water and ethanol;
the vacuum drying temperature is 60 ℃, the vacuum drying time is 4-6 hours, the vacuum sintering temperature is 300-400 ℃, and the vacuum sintering time is 8-12 hours;
the ball milling time is 10-30 minutes;
the mass ratio of the nano silicon composite particles to the LATP is 8-10: 1.0 to 2.0;
the ball milling time is 10-20 minutes again;
the pressing condition is 50-200 standard atmospheric pressures.
3. A solid state lithium battery according to claim 2, wherein,
the phosphorus source material is phosphoenone pyruvic acid;
the nitrogen source material is acrylamide;
the solvent a is dioxane, and the solvent b is trimethylbenzene.
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