CN113104905A - Preparation method of lithium-rich manganese-based composite material, positive electrode material and lithium ion battery - Google Patents

Preparation method of lithium-rich manganese-based composite material, positive electrode material and lithium ion battery Download PDF

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CN113104905A
CN113104905A CN202110375235.9A CN202110375235A CN113104905A CN 113104905 A CN113104905 A CN 113104905A CN 202110375235 A CN202110375235 A CN 202110375235A CN 113104905 A CN113104905 A CN 113104905A
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lithium
precursor
manganese
based composite
cobalt
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邓城
李冰
程中原
郑田瑞
胡梦菲
梁世硕
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Kunshan Bao Innovative Energy Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention relates to a preparation method of a lithium-rich manganese-based composite material, a positive electrode material and a lithium ion battery, wherein the preparation method of the lithium-rich manganese-based composite material comprises the following steps: obtaining a nickel-cobalt-manganese precursor; reacting the nickel-cobalt-manganese precursor with a boron-containing compound solution to obtain a mixed precursor; and pre-burning the mixed precursor, cooling, mixing the obtained powder with a lithium salt, and sintering at a high temperature to obtain the lithium-rich manganese-based composite material. The mixed precursor is presintered to form a more uniform coating layer and promote the high-temperature sintering of the precursor, and the lithium-rich manganese-based composite material prepared by the method is applied to a positive electrode material and a lithium ion battery, so that the first coulombic efficiency, the rate capability, the cycling stability and the safety of the battery can be obviously improved, and the service life is greatly prolonged. And the preparation method of the lithium-rich manganese-based composite material is simple, the material cost is low, and the lithium-rich manganese-based composite material has good industrial production value.

Description

Preparation method of lithium-rich manganese-based composite material, positive electrode material and lithium ion battery
Technical Field
The invention belongs to the field of composite materials, and particularly relates to a preparation method of a lithium-rich manganese-based composite material, a positive electrode material and a lithium ion battery.
Background
The lithium ion battery has the characteristics of high specific energy, no memory effect, long service life, environmental friendliness and the like, and has wide application prospects in the fields of 3C consumer products and power automobiles. Lithium ion batteries are still in a vigorous development period at present, and have a great space for improvement in terms of energy density, safety, cost and the like. In the lithium ion battery, the positive electrode material occupies 35-40% of the cost of the whole battery cell, so that the search for the positive electrode material with high specific capacity, high voltage and low cost has important significance for further improving the performance of the battery cell. The lithium-rich manganese-based positive electrode material is praised by researchers at home and abroad as one of the most promising positive electrode materials of the next generation, and is one of the key materials for realizing the 350Wh/kg target of the single battery cell in 2025. However, the lithium-rich manganese-based positive electrode material also has the problems of low first efficiency, poor multiplication rate, voltage attenuation and the like, and needs to be improved and optimized in material aspect, battery core and PACK aspect.
In the related technology, some methods add boron compounds during precursor synthesis, the method is easy to form impurity phases, and boron is not easy to be co-precipitated with nickel, cobalt and manganese and enter crystal lattices to deteriorate electrochemical properties. In addition, a nickel-cobalt-manganese precursor is synthesized firstly, and then the precursor, lithium salt and a boron-containing compound are ground, mixed and sintered, the method adopts a physical dry mixing mode of mechanical grinding, so that the mixing is not uniform easily, and the material obtained after sintering is not uniformly doped, so that the electrochemical performance is not stable.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a preparation method of the lithium-rich manganese-based composite material, and the lithium-rich manganese-based composite material prepared by the method can be applied to the anode material and the lithium ion battery, so that the first coulombic efficiency, the rate capability, the cycling stability and the safety of the battery can be obviously improved, and the service life can be greatly prolonged.
The second aspect of the present invention provides a positive electrode material.
The third aspect of the invention also provides a lithium ion battery.
According to a first aspect of the invention, a preparation method of a lithium-rich manganese-based composite material is provided, which comprises the following steps: obtaining a nickel-cobalt-manganese precursor; reacting the nickel-cobalt-manganese precursor with a boron-containing compound solution to obtain a mixed precursor; and pre-burning the mixed precursor, cooling, mixing the obtained powder with a lithium salt, and sintering at a high temperature to obtain the lithium-rich manganese-based composite material.
The preparation method of the lithium-rich manganese-based composite material provided by the embodiment of the invention at least has the following beneficial effects: the boron-containing compound solution is reacted with the nickel-cobalt-manganese precursor to obtain a boron-modified mixed precursor, and the boron-containing compound is subjected to mixed reaction by a liquid phase method, so that a more uniform coating layer can be formed on the surface of the nickel-cobalt-manganese substrate material. The mixed precursor is pre-sintered, the obtained powder is mixed with lithium salt after cooling, and the molten boron-containing compound permeates to the surface of primary particles to form a more uniform and complete coating layer and promote the high-temperature sintering of the mixed precursor due to the lower melting point and better fluidity and wettability of the boron-containing compound. Because no lithium salt is added in the presintering stage, the mutual competition of the lithium salt and a boron-containing compound is avoided, a good coating layer can be formed in the presintering stage, and finally the boron-modified nickel-cobalt-manganese-based composite material with more uniformity and better consistency is obtained. In addition, the lithium-rich manganese-based composite material is simple in preparation method, low in material cost and high in industrial production value.
It should be noted that the preparation method of the obtained nickel-cobalt-manganese precursor includes various methods, such as a coprecipitation method, a sol-gel method, a solid phase method, a hydrothermal method, and the like, and different preparation methods can be used according to different application scenarios, while the coprecipitation method is generally adopted in current industrial production.
According to some embodiments of the present invention, the nickel-cobalt-manganese precursor is prepared by a coprecipitation method, including the following steps: dissolving metal salt containing nickel, cobalt and manganese in a first solvent to prepare a metal mixed solution; and mixing the metal mixed solution and the precipitant solution, carrying out coprecipitation reaction, and aging, separating and drying to obtain the nickel-cobalt-manganese precursor.
According to some embodiments of the invention, the metal salt of nickel comprises at least one of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate, the metal salt of cobalt comprises cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate, and the metal salt of manganese comprises at least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate.
According to some embodiments of the invention, the precipitant in the precipitant solution comprises at least one of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate.
According to some embodiments of the invention, the first solvent is at least one of deionized water, ethanol, ethylene glycol, propanol, isopropanol, butanetriol, acetone.
According to some embodiments of the invention, the precipitant solution may be formed by dissolving the precipitant in a second solvent. Further, the second solvent may be at least one of deionized water, ethanol, ethylene glycol, propanol, isopropanol, butanetriol and acetone.
According to some embodiments of the present invention, in the coprecipitation reaction, the pH of the solution is adjusted to 7.5 to 11.5, and the coprecipitation reaction is performed at 40 to 75 ℃ in a protective atmosphere.
According to some embodiments of the invention, the protective atmosphere comprises at least one of argon, nitrogen, helium, neon.
According to some embodiments of the invention, the nickel cobalt manganese precursor is reacted with a boron containing compound solution to obtain a mixed precursor, comprising the steps of: and adding the precursor into a first dispersing agent to form a suspension, adding a boron-containing compound into a second dispersing agent to form a boron-containing solution, dropwise adding the boron-containing solution into the suspension, stirring for reaction, evaporating to dryness and baking to obtain the mixed precursor.
In the reaction process, compared with one-time direct pouring, the boron-containing solution is added into the suspension in a dropwise manner, so that the phenomenon that the local concentration of the boron-containing compound in the nickel-cobalt-manganese precursor is too high and the boron-containing compound is not favorably dispersed can be avoided, and the uniformity of mixing is favorably realized by adopting a gradual dropwise manner. In addition, after the stirring reaction, the powder can be dried quickly by combining the drying by distillation and baking modes, and the drying efficiency is improved.
According to some embodiments of the invention, the first and/or second dispersant is at least one of deionized water, ethanol, ethylene glycol, acetone. The first dispersant and the second dispersant may be the same or different.
According to some embodiments of the invention, the boron-containing compound comprises at least one of boric acid, sodium borate, potassium borate, ammonium borate, boron oxide.
According to some embodiments of the invention, the molar ratio of the nickel cobalt manganese precursor to the boron containing compound is 100 (0.1-10); and/or the stirring reaction time is 0.5-12 h; and/or the evaporation temperature is 50-95 ℃; and/or the baking temperature is 60-120 ℃.
In some embodiments, the molar ratio of the nickel-cobalt-manganese precursor to the boron-containing compound may be any one of 100:0.1, 100:1.5, 100:2, 100:2.5, 100:3, 100:5, 100:6.5, 100:8, 100:9, 100:9.5, or 100:10, etc.
It should be noted that the molar ratio of the nickel-cobalt-manganese precursor to the boron-containing compound is controlled to be 100 (0.1-10), which belongs to a key control parameter in the preparation method of the lithium-rich manganese-based composite material of the present invention, if the ratio is too high, the coating layer may be incomplete or too poor in uniformity, such that the modification effect is not obvious, if the ratio is too low, the coating layer may be too thick, the electrolyte may not well infiltrate primary particles, which may affect the exertion of the specific capacity of the material, and too much boron-containing compound may cause excessive sintering, such that the particle size of the primary particles is too large, and the electrochemical performance is deteriorated.
According to some embodiments of the invention, the pre-sintering temperature is 300-650 ℃, the heating rate is 1-10 ℃, and the pre-sintering time is 2-8 h; preferably, the pre-sintering temperature is 400-500 ℃, the temperature rising rate is 3-6 ℃, and the pre-sintering time is 4-6 hours.
In some embodiments, the temperature of the pre-firing may be any one of 300 ℃, 400 ℃, 500 ℃, 520 ℃, 550 ℃, 600 ℃ or 650 ℃.
The pre-sintering process is controlled within the range, so that the composite material can form a good coating layer in the pre-sintering stage, and finally the boron-modified nickel-cobalt-manganese-based composite material with more uniformity and better consistency is obtained.
According to some embodiments of the invention, the high-temperature sintering is divided into two sections, the first section sintering temperature is 350-650 ℃, the heating rate is 1-10 ℃/min, the sintering time is 2-8 h, the second section sintering temperature is 750-1000 ℃, the heating rate is 1-10 ℃/min, and the sintering time is 6-24 h.
It should be noted that, because the special calcination scheme adopted in the present invention is to pre-calcine the mixed precursor obtained by reacting the boron-containing compound with the nickel-cobalt-manganese precursor, in this process, the boron-containing compound has better fluidity and wettability, and the molten boron-containing compound permeates to the surface of the primary particles to form a more uniform and complete coating layer, and can promote the sintering of the mixed precursor. In addition, because no lithium salt is added in the pre-sintering stage, the mutual competition between the lithium salt and the boron-containing compound is eliminated, a relatively complete coating layer can be formed in the pre-sintering stage, and then the coating layers on the surfaces of the secondary particles and the surfaces of the primary particles in the secondary particles tend to be more uniform and complete through a subsequent two-step high-temperature calcining method, so that the exposed uncoated surfaces or the surfaces with over-thick coating can be effectively reduced.
According to some embodiments of the invention, the molar concentration of the total metal of nickel, cobalt and manganese in the metal mixed solution is 0.5-3 mol/L; and/or the molar concentration of the precipitant in the precipitant solution is 0.5-4 mol/L; and/or the molar ratio of the lithium ions in the lithium salt to the total metal concentration in the mixed precursor is (1-2): 1.
it is understood that the ratio of the lithium ions in the lithium salt to the total metal concentration in the mixed precursor is one of the core control steps in the preparation of the lithium-rich manganese-based composite material, and if the lithium ion content is too low, a good lithium-rich layered structure cannot be formed, and if the ratio is too high, the first coulombic efficiency and other electrochemical properties are deteriorated.
According to some embodiments of the invention, the lithium salt comprises at least one of lithium hydroxide, lithium carbonate, lithium acetate, lithium nitrate, lithium ethoxide.
In a second aspect of the invention, a positive electrode material is provided, which comprises the lithium-rich manganese-based composite material prepared by the preparation method of the lithium-rich manganese-based composite material.
According to the positive electrode material provided by the embodiment of the invention, the boron-modified nickel-cobalt-manganese-based composite material is adopted, boron enters a material lattice after the boron-containing compound is modified, the structure of the nickel-cobalt-manganese-based material can be stabilized, the cycle stability of the lithium-rich manganese-based composite material as the positive electrode material is improved, the oxygen release is reduced, a lithium borate coating layer can be formed on the surface of the lithium-nickel-cobalt-manganese material, and the lithium-rich manganese-based composite material is used in the positive electrode, so that the first efficiency, the rate capability and the cycle stability of the positive electrode material can be improved, and the oxygen precipitation and the voltage attenuation of the structure can be inhibited.
In a third aspect of the present invention, there is provided a lithium ion battery comprising a positive electrode, a negative electrode and a separator, wherein the positive electrode comprises the positive electrode material described above.
According to the lithium ion battery provided by the embodiment of the invention, due to the adoption of the lithium-rich manganese-based composite material, the rate performance of the battery can be enhanced, and the lithium borate coating layer in the composite material can reduce the corrosion of electrolyte to a matrix material, so that the cycle stability of the lithium ion battery is improved.
Drawings
The invention is further described with reference to the following figures and examples, in which:
FIG. 1 is a graph of battery rate performance for examples 1-2 of the present invention and comparative example 1;
FIG. 2 is a graph showing the cycle characteristics of the batteries of examples 1-2 of the present invention and comparative examples 1-2;
fig. 3 is SEM images of lithium-rich manganese-based composites of comparative example 1 and example 3 according to the present invention, wherein a is the SEM image of the lithium-rich manganese-based composite of comparative example 1, and b is the SEM image of the lithium-rich manganese-based composite of example 3.
Detailed Description
The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.
In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Specific examples of the present invention are described in detail below.
Example 1
The preparation process of the lithium-rich manganese-based composite positive electrode material comprises the following steps:
(1) according to a molar ratio of 1: 1: 4 weighing nickel sulfate, cobalt sulfate and manganese sulfate, dissolving in deionized water to prepare a 2mol/L metal salt mixed solution, and dissolving a sodium carbonate precipitator in the deionized water to form a 2mol/L sodium carbonate solution;
(2) pumping the metal salt mixed solution and a sodium carbonate solution into a reaction base solution, adjusting the pH of the solution to 8.5 by using ammonia water, carrying out coprecipitation reaction under the protection of argon atmosphere, wherein the reaction temperature is 55 ℃, the reaction time is 24 hours, and after the reaction is finished, carrying out aging, solid-liquid separation and drying treatment to obtain Ni1/6Co1/6Mn4/6CO3A precursor;
(3) adding the precursor into ethanol to form a suspension, adding boric acid into deionized water to form a solution, wherein the molar ratio of the precursor to the boric acid is 100:2, dropwise adding a boric acid solution into the precursor suspension, stirring and reacting for 1h, evaporating to dryness in a water bath at 80 ℃ and baking at 90 ℃ to obtain modified mixed precursor powder;
(4) heating the modified mixed precursor powder to 500 ℃ at the speed of 3 ℃/min, preserving heat for 3h, cooling along with the furnace, and mixing with lithium hydroxide according to the molar ratio of 1: 1.55 grinding and mixing, heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 5h, heating to 850 ℃ at the speed of 5 ℃/min, preserving heat for 10h, and obtaining the modified lithium-rich manganese-based composite anode material.
The preparation process of the button type lithium ion battery comprises the following steps:
and (2) taking NMP (N-methyl pyrrolidone) as a solvent, homogenizing the prepared lithium-rich manganese-based composite positive electrode material, PVDF (polyvinylidene fluoride) and SP (conductive carbon black) according to a mass ratio of 90:5:5, coating the obtained mixture on a current collector Al foil, drying to obtain a positive electrode piece, assembling the positive electrode piece and a metal lithium piece into a button cell, and testing the electrochemical performance of the button cell.
In addition, the prepared lithium-rich manganese-based composite positive electrode material, a negative electrode, an electrolyte, a diaphragm, an aluminum plastic film and a lug can be assembled into a full cell according to a certain process, and finally the full cell can be applied to an electric automobile.
Example 2
The preparation process of the lithium-rich manganese-based composite positive electrode material comprises the following steps:
(1) according to a molar ratio of 1: 1: 4 weighing nickel sulfate, cobalt sulfate and manganese sulfate, dissolving in deionized water to prepare a 2mol/L metal salt mixed solution, and dissolving a sodium carbonate precipitator in the deionized water to form a 2mol/L sodium carbonate solution;
(2) pumping the metal salt mixed solution and a sodium carbonate solution into a reaction base solution, adjusting the pH of the solution to 8.5 by using ammonia water, carrying out coprecipitation reaction under the protection of argon atmosphere, wherein the reaction temperature is 55 ℃, the reaction time is 24 hours, and after the reaction is finished, carrying out aging, solid-liquid separation and drying treatment to obtain Ni1/6Co1/6Mn4/6CO3A precursor;
(3) adding the precursor into ethanol to form a suspension, adding boric acid into deionized water to form a solution, wherein the molar ratio of the precursor to the boric acid is 100:1.5, dropwise adding a boric acid solution into the precursor suspension, stirring and reacting for 0.5h, evaporating to dryness in a water bath at 80 ℃ and baking at 90 ℃ to obtain modified mixed precursor powder;
(4) heating the modified mixed precursor powder to 520 ℃ at the speed of 3 ℃/min, preserving heat for 3h, cooling along with the furnace, and mixing with lithium hydroxide according to the molar ratio of 1: 1.55 grinding and mixing, heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 5h, then heating to 875 ℃ at the speed of 5 ℃/min, preserving heat for 12h, and obtaining the modified lithium-rich manganese-based composite anode material.
The preparation process of the button type lithium ion battery comprises the following steps:
and (2) taking NMP as a solvent, homogenizing the prepared lithium-rich manganese-based composite positive electrode material, PVDF and SP according to the mass ratio of 90:5:5, coating the obtained mixture on a current collector Al foil, drying to obtain a positive electrode piece, assembling the positive electrode piece and a metal lithium piece into a button cell, and testing the electrochemical performance of the button cell.
In addition, the prepared lithium-rich manganese-based composite positive electrode material, a negative electrode, an electrolyte, a diaphragm, an aluminum-plastic film and a lug can be assembled into a full cell according to a certain process, and the full cell can be finally applied to an electric automobile.
Example 3
The preparation process of the lithium-rich manganese-based composite positive electrode material comprises the following steps:
(1) according to a molar ratio of 1: 1: 4 weighing nickel sulfate, cobalt sulfate and manganese sulfate, dissolving in deionized water to prepare a 2mol/L metal salt mixed solution, and dissolving a sodium carbonate precipitator in the deionized water to form a 2mol/L sodium carbonate solution;
(2) pumping the metal salt mixed solution and a sodium carbonate solution into a reaction base solution, adjusting the pH of the solution to 8.5 by using ammonia water, carrying out coprecipitation reaction under the protection of argon atmosphere, wherein the reaction temperature is 55 ℃, the reaction time is 24 hours, and after the reaction is finished, carrying out aging, solid-liquid separation and drying treatment to obtain Ni1/6Co1/6Mn4/6CO3A precursor;
(3) adding the precursor into ethanol to form a suspension, adding boric acid into deionized water to form a solution, wherein the molar ratio of the precursor to the boric acid is 100:2.5, dropwise adding the boric acid solution into the precursor suspension, stirring and reacting for 1.5h, evaporating to dryness in a water bath at 85 ℃, and baking at 95 ℃ to obtain modified mixed precursor powder;
(4) heating the modified mixed precursor powder to 520 ℃ at the speed of 3 ℃/min, preserving heat for 3h, cooling along with the furnace, and mixing with lithium hydroxide according to the molar ratio of 1: 1.55 grinding and mixing, heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 5h, heating to 850 ℃ at the speed of 5 ℃/min, preserving heat for 15h, and obtaining the modified lithium-rich manganese-based composite anode material.
The preparation process of the button type lithium ion battery comprises the following steps:
and (2) taking NMP (N-methyl pyrrolidone) as a solvent, homogenizing the prepared lithium-rich manganese-based composite positive electrode material, PVDF (polyvinylidene fluoride) and SP (conductive carbon black) according to a mass ratio of 90:5:5, coating the obtained mixture on a current collector Al foil, drying to obtain a positive electrode piece, assembling the positive electrode piece and a metal lithium piece into a button cell, and testing the electrochemical performance of the button cell. The modified SEM image of example 3 is shown in FIG. 3.
In addition, the prepared lithium-rich manganese-based composite positive electrode material, a negative electrode, an electrolyte, a diaphragm, an aluminum-plastic film and a lug can be assembled into a full cell according to a certain process, and the full cell can be finally applied to an electric automobile.
Comparative example 1
The preparation process of the lithium-rich manganese-based composite positive electrode material comprises the following steps:
(1) according to a molar ratio of 1: 1: 4 weighing nickel sulfate, cobalt sulfate and manganese sulfate, dissolving in deionized water to prepare a 2mol/L metal salt mixed solution, and dissolving a sodium carbonate precipitator in the deionized water to form a 2mol/L sodium carbonate solution;
(2) pumping the metal salt mixed solution and a sodium carbonate solution into a reaction base solution, adjusting the pH of the solution to 8.5 by using ammonia water, carrying out coprecipitation reaction under the protection of argon atmosphere, wherein the reaction temperature is 55 ℃, the reaction time is 24 hours, and after the reaction is finished, carrying out aging, solid-liquid separation and drying treatment to obtain Ni1/6Co1/6Mn4/6CO3A precursor;
(3) mixing the precursor powder and lithium hydroxide according to a molar ratio of 1: 1.55 grinding and mixing, heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 5h, then heating to 850 ℃ at the speed of 5 ℃/min, preserving heat for 10h, and obtaining the modified lithium-rich manganese-based composite cathode material.
The preparation process of the button type lithium ion battery comprises the following steps:
and (2) taking NMP as a solvent, homogenizing the prepared lithium-rich manganese-based composite positive electrode material, PVDF and SP according to the mass ratio of 90:5:5, coating the obtained mixture on a current collector Al foil, drying to obtain a positive electrode piece, assembling the positive electrode piece and a metal lithium piece into a button cell, and testing the electrochemical performance of the button cell.
In addition, the prepared lithium-rich manganese-based composite positive electrode material, a negative electrode, an electrolyte, a diaphragm, an aluminum-plastic film and a lug can be assembled into a full cell according to a certain process, and the full cell can be finally applied to an electric automobile.
Comparative example 2
(1) According to a molar ratio of 1: 1: 4 weighing nickel sulfate, cobalt sulfate and manganese sulfate, dissolving in deionized water to prepare a 2mol/L metal salt mixed solution, and dissolving a sodium carbonate precipitator in the deionized water to form a 2mol/L solution;
(2) pumping the metal salt mixed solution and sodium carbonate solution into reaction base solution, adjusting the pH of the solution to 8.5 by using ammonia water, and carrying out co-reaction under the protection of argon atmospherePrecipitation reaction at 55 deg.c for 24 hr, ageing, solid-liquid separation and drying to obtain Ni1/6Co1/6Mn4/6CO3A precursor;
(3) adding the precursor into ethanol to form a suspension, adding boric acid into deionized water to form a solution, wherein the molar ratio of the precursor to boron oxide is 100:2.5, dropwise adding the boric acid solution into the precursor suspension, stirring and reacting for 1.5h, evaporating to dryness in a water bath at 85 ℃, and baking at 95 ℃ to obtain modified precursor powder;
(4) mixing the modified precursor powder and lithium hydroxide according to a molar ratio of 1: 1.55 grinding and mixing, heating to 550 ℃ at the speed of 3 ℃/min, preserving heat for 5h, then heating to 850 ℃ at the speed of 5 ℃/min, preserving heat for 10h, and obtaining the modified lithium-rich manganese-based composite cathode material.
The preparation process of the button type lithium ion battery comprises the following steps:
and (2) taking NMP as a solvent, homogenizing the prepared lithium-rich manganese-based composite positive electrode material, PVDF and SP according to the mass ratio of 90:5:5, coating the obtained mixture on a current collector Al foil, drying to obtain a positive electrode piece, assembling the positive electrode piece and a metal lithium piece into a button cell, and testing the electrochemical performance of the button cell.
In addition, the prepared lithium-rich manganese-based composite positive electrode material, a negative electrode, an electrolyte, a diaphragm, an aluminum-plastic film and a lug can be assembled into a full cell according to a certain process, and the full cell can be finally applied to an electric automobile.
The rate performance of the button cells prepared in examples 1-2 and comparative example 1 is shown in fig. 1 and 2, and it can be seen from the figure that the rate performance of the button cells prepared in examples 1 and 2 is obviously better than that of comparative example 1 at 0.1C, 0.2C, 0.5C, 1C, 2C and 5C, and especially the difference is more obvious at 5C large rate. In example 1, the capacity retention rate after 50 weeks of 1C cycle was 96.37%, which is 10.39% higher than 87.30% of comparative example 1. In example 2, the capacity retention rate after 50 weeks of 1C cycle was 94.05%, which is 7.73% higher than 87.30% of comparative example 1. The lithium-rich manganese-based composite material disclosed by the invention is modified by boron, and a lithium borate coating layer formed on the surface of lithium nickel cobalt manganese has a three-dimensional ion channel, so that the lithium-rich manganese-based composite material is beneficial to lithium ion migration, and the rate capability of a battery can be obviously improved.
The cycle performance at 1C of comparative example 2 is shown in fig. 2, and compared to comparative example 1 in which boron is not modified, the cycle stability of comparative example 2 modified with a boron-containing compound is significantly better than that of comparative example 1, and in comparative example 2, the 1C cycle capacity retention rate is increased from 87.3% in which boron is not modified to 93.2%, but compared to examples 1 and 2 in which pre-firing is employed, the precursor of comparative example 2 is not subjected to the pre-firing process before being mixed with a lithium salt, and the capacity retention rate is relatively low. The fact that the pre-sintering treatment is carried out before the lithium salt is mixed with the lithium salt shows that the mutual competition between the lithium salt and the boron-containing compound can be avoided, a good coating layer can be formed in the pre-sintering stage, a lithium-rich manganese-based composite material which is more uniform and more consistent can be obtained, and the cycle performance of the battery can be improved when the lithium-rich manganese-based composite material is used as a lithium ion battery anode material.
Fig. 3 shows SEM images of the unmodified lithium-rich manganese-based composite material of comparative example 1 and the boron-modified lithium-rich manganese-based composite material of example 3, and it can be seen that a uniform lithium borate coating layer is formed on the surface of the lithium nickel cobalt manganese material after modification with the boron-containing compound. The coating layer can reduce the erosion of electrolyte to a matrix material, improve the first-time efficiency and the circulation stability, is favorable for improving the rate performance of the material, particularly the 5C high-rate discharge performance, and provides a good performance effect for the lithium-rich manganese-based composite material as a battery electrode material.
TABLE 1 electrochemical data for each of the examples and comparative examples
Figure BDA0003010900230000111
Table 1 shows the electrochemical properties of examples 1 to 3 and comparative examples 1 to 2, and it can be seen that the initial discharge specific capacity and the coulombic efficiency of examples 1 to 3 after boron modification are improved to different degrees compared with the unmodified comparative example 1, and the discharge voltage-sharing retention rate after 100 cycles is improved, and compared with comparative example 2, the initial discharge specific capacity and the discharge voltage-sharing retention rate after 100 cycles of examples 1 to 3 are significantly better, and the improvement of the discharge voltage-sharing retention rate can indicate that the cycle stability of the modified material is better, so that the safety and the service life of the material can be improved. It is fully shown that the way of using the pre-firing and high-temperature firing regimes of the present invention has a more prominent performance improvement effect.
While the embodiments of the present invention have been described in detail with reference to the specific embodiments, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

Claims (10)

1. The preparation method of the lithium-rich manganese-based composite material is characterized by comprising the following steps of:
obtaining a nickel-cobalt-manganese precursor;
reacting the nickel-cobalt-manganese precursor with a boron-containing compound solution to obtain a mixed precursor;
and pre-burning the mixed precursor, cooling, mixing the obtained powder with a lithium salt, and sintering at a high temperature to obtain the lithium-rich manganese-based composite material.
2. The preparation method of claim 1, wherein the nickel-cobalt-manganese precursor is prepared by a coprecipitation method, and the coprecipitation method comprises the following steps:
dissolving metal salt containing nickel, cobalt and manganese in a first solvent to prepare a metal mixed solution;
and mixing the metal mixed solution and the precipitant solution, carrying out coprecipitation reaction, and aging, separating and drying to obtain the nickel-cobalt-manganese precursor.
3. The preparation method according to claim 2, wherein in the coprecipitation reaction, the solution is adjusted to a pH of 7.5 to 11.5, and the coprecipitation reaction is performed at 40 to 75 ℃ in a protective atmosphere.
4. The preparation method according to claim 1, wherein the nickel-cobalt-manganese precursor is reacted with a boron-containing compound solution to obtain a mixed precursor, comprising the steps of:
and adding the precursor into a first dispersing agent to form a suspension, adding a boron-containing compound into a second dispersing agent to form a boron-containing solution, dropwise adding the boron-containing solution into the suspension, stirring for reaction, evaporating to dryness and baking to obtain the mixed precursor.
5. The method of claim 4, wherein the molar ratio of the nickel-cobalt-manganese precursor to the boron-containing compound is 100 (0.1-10); and/or the stirring reaction time is 0.5-12 h; and/or the evaporation temperature is 50-95 ℃; and/or the baking temperature is 60-120 ℃.
6. The preparation method according to any one of claims 1 to 5, wherein the pre-sintering temperature is 300 to 650 ℃, the temperature rise rate is 1 to 10 ℃, and the pre-sintering time is 2 to 8 hours; preferably, the pre-sintering temperature is 400-500 ℃, the temperature rising rate is 3-6 ℃, and the pre-sintering time is 4-6 hours.
7. The method according to any one of claims 1 to 5, wherein the high-temperature sintering is divided into two stages, the first stage sintering temperature is 350 to 650 ℃, the temperature rise rate is 1 to 10 ℃/min, the sintering time is 2 to 8 hours, the second stage sintering temperature is 750 to 1000 ℃, the temperature rise rate is 1 to 10 ℃/min, and the sintering time is 6 to 24 hours.
8. The preparation method according to claim 2, wherein the molar concentration of the total metal of nickel, cobalt and manganese in the metal mixed solution is 0.5-3 mol/L; and/or the molar concentration of the precipitant in the precipitant solution is 0.5-4 mol/L; and/or the molar ratio of the lithium ions in the lithium salt to the total metal concentration in the mixed precursor is (1-2): 1.
9. A positive electrode material comprising the lithium-rich manganese-based composite material obtained by the method for producing a lithium-rich manganese-based composite material according to any one of claims 1 to 8.
10. A lithium ion battery comprising a positive electrode, a negative electrode, and a separator, wherein the positive electrode comprises the positive electrode material according to claim 9.
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