Modified lithium-rich manganese-based positive electrode material, preparation method thereof and lithium ion battery
Through the synergistic combination of dual ion doping of aluminum and boron and a boron oxide coating, the problems of rapid capacity decay and structural distortion of lithium-rich manganese-based positive electrode materials are solved, and the electrochemical performance and structural stability of the materials are improved.
Patent Information
- Application Number
- CN202510881777.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-27
- Publication Date
- 2025-09-26
AI Technical Summary
Lithium-rich manganese-based positive electrode materials experience rapid capacity decay and voltage decay during long-term operation. Anion redox reactions lead to irreversible oxygen evolution, interfacial side reactions and structural distortion, resulting in low first coulombic efficiency, poor cycle performance and poor rate performance.
By adopting the synergistic combination of dual ion doping of aluminum and boron and a boron oxide coating, aluminum is evenly dispersed in the bulk phase of the lithium-rich manganese-based base material, and boron is located at the interstitial sites to form BO bonds, inhibiting cation migration and stabilizing the layered structure. The boron oxide coating prevents direct contact with the electrolyte and reduces the interface resistance.
The initial coulombic efficiency, cycle performance and rate performance of lithium-rich manganese-based positive electrode materials have been improved, the layered structure of the materials has been stabilized, the transition metal loss and interface resistance have been reduced, and the capacity retention rate has been improved.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium ion batteries and relates to a modified lithium-rich manganese-based positive electrode material and a preparation method thereof, and a lithium ion battery. Background Art
[0002] With the widespread adoption of lithium-ion batteries in electric vehicles, higher demands are being placed on the energy density of power batteries. Commercially available cathode materials, such as lithium iron phosphate, ternary materials, lithium manganese oxide, and lithium cobalt oxide, have low energy densities, making them difficult to meet future demand for high-energy-density batteries. This significantly limits the application of lithium-ion batteries in new energy vehicles. The discharge capacity of commercially available graphite anode materials exceeds 350 mAh / g, while the discharge capacity of commercially available lithium battery cathode materials does not exceed 200 mAh / g. Clearly, cathode materials have become a bottleneck restricting the development of lithium-ion batteries, necessitating the development of cathode materials with higher energy densities.
[0003] Lithium-rich manganese-based cathode materials have attracted much attention due to their unique advantages, such as high discharge specific capacity (≥250mAh / g) and high discharge voltage platform (≥3.5V). In addition, lithium-rich manganese-based cathode materials also have the advantages of low pollution and low cost, and are considered to be one of the most promising lithium-ion battery cathode materials, which will meet the high energy density requirements of electric vehicles. However, the rapid capacity decay and voltage decay during long-term operation hinder the practical application of lithium-rich manganese-based materials. In addition, the anion redox reaction under high pressure can also lead to irreversible oxygen evolution, which will aggravate the side reactions at the electrode / electrolyte interface and consume more active lithium. Irreversible phase change, the formation of by-products and Li + The increase in the ion diffusion barrier limits the electrochemical reversibility of Li+, and the reduction in the initial Coulombic efficiency (ICE) leads to a decrease in reversible capacity and rate performance. Lithium-rich manganese-based cathode materials have inherent defects such as low initial Coulombic efficiency, poor cycling performance, and poor rate performance, caused by irreversible loss of lattice oxygen, interfacial side reactions, and structural distortion.
[0004] To address these challenges, researchers have used strategies such as defect design, ion doping, surface coating, and single crystal structure design to inhibit lattice oxygen loss, improve the electronic and ionic conductivity of materials, inhibit electrolyte corrosion, and inhibit material structural phase transitions. However, the above issues still need further exploration. Summary of the Invention
[0005] In response to the shortcomings of the prior art, the present invention aims to provide a modified lithium-rich manganese-based cathode material, a preparation method thereof, and a lithium-ion battery. The modified lithium-rich manganese-based cathode material provided by the present invention utilizes dual ion doping with aluminum and boron, synergistically combined with boron oxide coating, to improve the problems of irreversible lattice oxygen loss, interfacial side reactions, and structural distortion that often occur in lithium-rich manganese-based materials, thereby improving the cathode material's initial coulombic efficiency, cycle performance, and rate capability.
[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:
[0007] In a first aspect, the present invention provides a modified lithium-rich manganese-based positive electrode material, wherein the modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material core and a boron oxide coating layer coated on the surface of the lithium-rich manganese-based material core;
[0008] The lithium-rich manganese-based material core includes a lithium-rich manganese-based base material and aluminum and boron doped in the lithium-rich manganese-based base material.
[0009] In the modified lithium-rich manganese-based positive electrode material of the present invention, the ion doping of aluminum and boron in the core and the coating of the boron oxide coating layer cooperate and work together, wherein aluminum is uniformly dispersed in the bulk phase of the lithium-rich manganese-based base material, which can enhance the stability of TM-O and inhibit cation migration, thereby inhibiting the transformation of the material from a layered phase to a spinel phase, while boron is located in the interstitial sites of the lithium-rich manganese-based base material, forming a BO bond, so that there are more negative charges in oxygen, thereby reducing the transition oxidation of oxygen and inhibiting irreversible structural changes during the cycle, further stabilizing the layered structure of the material, in addition, B doping can further effectively hinder the migration of cations; and the boron oxide coating layer makes the cycle performance of the lithium-rich manganese-based positive electrode material stable and has a high coulombic efficiency. The presence of B2O3 can also improve the capacity retention rate, prevent direct physical contact with the electrolyte, reduce the dissolution of Mn, and thus reduce the loss of transition metals from the cathode structure. It can also reduce the interfacial resistance, thereby facilitating the transfer of lithium ions. The synergistic cooperation of specific dual-ion doping and coating has improved the problems of irreversible lattice oxygen loss, interface side reactions and structural distortion caused by lithium-rich manganese-based basic materials, thereby improving the first coulombic efficiency, cycle performance and rate performance of the positive electrode material.
[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.
[0011] Preferably, the general chemical formula of the lithium-rich manganese-based basic material is Li 1+a (Ni x Co y Mn z) 1-a O2, 0<a<1, x>0, y≥0, z>x, and x+y+z=1.
[0012] For example, a may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, x may be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4, y may be 0, 0.05, 0.1, 0.15, 0.2, 0.25 or 0.3, y may be 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0013] Preferably, the Li 1+a (Ni x Co y Mn z ) 1-a In O2, 0.1≤a≤0.3, for example, 0.1, 0.15, 0.2, 0.25 or 0.3, and 0.5≤z≤0.9, for example, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85 or 0.9, etc.
[0014] Preferably, the molar proportion of aluminum in the lithium-rich manganese-based base material is 0.1% to 0.3%, for example, 0.1%, 0.13%, 0.15%, 0.18%, 0.2%, 0.23%, 0.25%, 0.28% or 0.3%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0015] Preferably, the boron doping mass in the lithium-rich manganese-based material core is 1 to 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0016] In the core of the present invention, regulating the molar proportion of aluminum in the lithium-rich manganese-based base material to 0.1% to 0.3% and / or the boron doping mass to 1 to 5% can better inhibit cation migration and thus stabilize the layered structure of the material.
[0017] Preferably, based on the mass of the lithium-rich manganese-based material core as 100%, the coating amount of the boron oxide coating layer is 2% to 6%, for example, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% or 6%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0018] In the present invention, the coating amount of the boron oxide coating layer is 2% to 6%, which is more conducive to achieving uniform coating, and is also beneficial to preventing direct physical contact between the material and the electrolyte, reducing the dissolution of Mn and reducing the interface resistance.
[0019] In a second aspect, the present invention provides a method for preparing the modified lithium-rich manganese-based positive electrode material as described in the first aspect, the preparation method comprising the following steps:
[0020] (1) mixing a manganese-based main metal element solution, an aluminum salt solution, a precipitant solution, and a complexing agent solution to perform a coprecipitation reaction to obtain an aluminum-doped lithium-rich manganese-based carbonate precursor material;
[0021] (2) performing a first sintering on the aluminum-doped lithium-rich manganese-based carbonate precursor material to obtain an oxide precursor; mixing a lithium source with the oxide precursor and performing a second sintering to obtain an intermediate phase material;
[0022] (3) mixing the intermediate phase material with a boron source and performing oxygen-free sintering to obtain the modified lithium-rich manganese-based positive electrode material.
[0023] In the present invention, a certain amount of Al element is first in-situ doped into the lithium-rich manganese-based carbonate precursor, and the Al salt is added separately, which is beneficial to improving the doping accuracy and reducing side reactions. The co-precipitation reaction of the carbonate system has better reaction control ability, lower temperature treatment requirements and more uniform component distribution. The bulk doping of Al in the lithium-rich manganese-based carbonate precursor enhances the stability of the TM-O bond and inhibits cation migration, thereby effectively inhibiting the transformation of the material from the layered phase to the spinel phase, improving the structural stability of the material, and thus improving the capacity retention rate and voltage retention rate of the material to a certain extent. Next, a bulk-doped aluminum lithium-rich manganese-based base material (intermediate phase material) is obtained by a first sintering and a second sintering with lithium, and then the intermediate phase material powder is ball milled and oxygen-free sintered with boric acid, so that B is successfully doped in the interstitial sites of the lithium-rich manganese-based base material and a thin amorphous B2O3 coating is formed on the surface of the material, which not only further stabilizes the layered structure of the material and effectively hinders the migration of cations, but also reduces the loss of transition metals from the cathode structure, reduces the interface resistance, and facilitates the transfer of lithium ions.
[0024] In the present invention, the co-precipitation reaction of the carbonate system, the first sintering, the second sintering and the oxygen-free sintering after mixing the boron source are all indispensable. If the co-precipitation reaction of the hydroxide system is adopted, problems such as product crystal structure defects or uneven element distribution will occur; and if the boron source is added and sintered in an oxygen-containing atmosphere, key properties such as the target phase purity, stable core-shell structure and expected lithium ion mobility cannot be obtained.
[0025] Preferably, the concentration of the manganese-based main metal element solution in step (1) is 0.5 to 2 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values, and other values not listed within this numerical range are also applicable.
[0026] Preferably, the concentration of the aluminum salt solution in step (1) is 1 to 3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0027] Preferably, the precipitant in step (1) comprises a carbonate precipitant.
[0028] It should be noted that the present invention does not specifically limit the specific type of carbonate precipitant. The present invention is applicable to any type of conventional carbonate positive electrode precursor material. For example, the precipitant includes but is not limited to at least one of sodium carbonate, sodium bicarbonate, ammonium carbonate or ammonium bicarbonate.
[0029] Preferably, the complexing agent comprises aqueous ammonia.
[0030] Preferably, the temperature of the coprecipitation reaction in step (1) is 40-60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0031] Preferably, the pH value of the coprecipitation reaction in step (1) is 7 to 9, for example, 7, 7.3, 7.5, 7.8, 8, 8.3, 8.5, 8.8 or 9, but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0032] Preferably, the coprecipitation reaction in step (1) is carried out at a rotation speed of 500 to 1000 rpm, for example, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.
[0033] It is understandable that, in the coprecipitation reaction process of the present invention, except for the above-mentioned characteristic limitations, the remaining preparation details and preparation processes are conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments based on actual needs.
[0034] Optionally, each raw material can be added to the reaction base liquid in parallel, and the reaction base liquid is selected according to conventional technology. The reaction base liquid includes water, a complexing agent and a precipitant, etc., and the pH value of the reaction base liquid can be 7-9.
[0035] Optionally, the feed amount of each raw material during the co-precipitation reaction can be adaptively adjusted according to the target doping amount of Al and the corresponding reaction pH value.
[0036] Optionally, after the coprecipitation reaction is completed, conventional aging, washing and drying treatments are performed in sequence.
[0037] Preferably, in step (1), the molar amount of aluminum doping in the lithium-rich manganese-based carbonate precursor material is 0.1% to 0.3%, for example, 0.1%, 0.13%, 0.15%, 0.18%, 0.2%, 0.23%, 0.25%, 0.28% or 0.3%, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0038] Preferably, in step (2), both the first sintering and the second sintering are performed in an oxygen-containing atmosphere.
[0039] It is understood that the oxygen-containing atmosphere described in the present invention is an atmosphere in which oxygen exists, for example, it can be an air atmosphere, a pure oxygen atmosphere, or a mixed atmosphere in which oxygen and a protective gas coexist, etc. Those skilled in the art can make adaptive selections and adjustments based on actual needs.
[0040] Preferably, the sintering temperature of the first sintering in step (2) is 300-500°C, for example, 300°C, 350°C, 400°C, 450°C or 500°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0041] Preferably, the sintering time of the first sintering in step (2) is 1 to 10 hours, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0042] Furthermore, the molar amount of lithium in the lithium source is based on Li 1+a (Ni x Co y Mn z ) 1-aO2 can be adaptively selected; and the lithium source includes but is not limited to at least one of lithium hydroxide, lithium carbonate, lithium nitrate or lithium acetate.
[0043] Preferably, the sintering temperature of the second sintering in step (2) is 800-1200°C, for example, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C or 1200°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0044] Preferably, the sintering time of the second sintering in step (2) is 8 to 24 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours or 24 hours, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.
[0045] Preferably, the boron source in step (3) comprises boric acid.
[0046] Preferably, the oxygen-free sintering in step (3) includes vacuum sintering and / or protective atmosphere sintering, preferably vacuum sintering.
[0047] In the present invention, the oxygen-free sintering can be carried out in a vacuum environment or in a protective atmosphere. Preferably, the sintering is carried out in a vacuum state, which can better eliminate the interference of residual oxygen on the reaction activity of the boron source.
[0048] Specifically, the vacuum sintering includes: using protective gas to replace the air in the reaction container, and then performing vacuum treatment to achieve a vacuum state in the reaction container.
[0049] Preferably, the mixing method in step (3) includes ball milling under a protective atmosphere, and the rotation speed of the ball milling is 50 to 300 rpm, for example, 50 rpm, 80 rpm, 100 rpm, 130 rpm, 150 rpm, 180 rpm, 200 rpm, 230 rpm, 250 rpm, 280 rpm or 300 rpm, etc., but is not limited to the listed values, and other values not listed within this numerical range are also applicable.
[0050] Preferably, the sintering temperature of the oxygen-free sintering in step (3) is 250-400°C, such as 250°C, 300°C, 350°C or 400°C, but is not limited to the listed values. Other values not listed within the numerical range are also applicable.
[0051] In the present invention, the sintering temperature of the oxygen-free sintering in step (3) is regulated to be 250-400° C., thereby further improving the ionic conductivity and interface stability.
[0052] Preferably, the sintering time of the oxygen-free sintering in step (3) is 2 to 8 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.
[0053] In a third aspect, the present invention further provides a lithium-ion battery, comprising the modified lithium-rich manganese-based positive electrode material as described in the first aspect or the modified lithium-rich manganese-based positive electrode material prepared by the preparation method as described in the second aspect.
[0054] Compared with the prior art, the present invention has the following beneficial effects:
[0055] (1) In the modified lithium-rich manganese-based positive electrode material of the present invention, the ion doping of aluminum and boron in the core and the coating of the boron oxide coating layer cooperate and work together, wherein aluminum is uniformly dispersed in the bulk phase of the lithium-rich manganese-based base material, which can enhance the stability of TM-O and inhibit the migration of cations, thereby inhibiting the transformation of the material from the layered phase to the spinel phase, while boron is located in the interstitial sites of the lithium-rich manganese-based base material to form BO bonds, so that there are more negative charges in oxygen, thereby reducing the transition oxidation of oxygen and inhibiting the irreversible structural changes during the cycle, further stabilizing the layered structure of the material, in addition, B doping can further effectively hinder the migration of cations; and the boron oxide coating layer makes the cycle performance of the lithium-rich manganese-based positive electrode material stable and has a high coulombic efficiency. The presence of B2O3 can also improve the capacity retention rate, prevent direct physical contact with the electrolyte, reduce the dissolution of Mn, and thus reduce the loss of transition metals from the cathode structure. It can also reduce the interface resistance, thereby facilitating the transfer of lithium ions. The synergistic cooperation of specific dual-ion doping and coating has improved the problems of irreversible lattice oxygen loss, interface side reactions and structural distortion caused by lithium-rich manganese-based basic materials, thereby improving the first coulombic efficiency, cycle performance and rate performance of the positive electrode material.
[0056] (2) In the present invention, a certain amount of Al element is first in situ doped into the lithium-rich manganese-based carbonate precursor, and Al salt is added separately, which is beneficial to improving the doping accuracy and reducing side reactions. The co-precipitation reaction of the carbonate system has better reaction control ability, lower temperature treatment requirements and more uniform component distribution. The bulk doping of Al in the lithium-rich manganese-based carbonate precursor enhances the stability of the TM-O bond and inhibits cation migration, thereby effectively inhibiting the transformation of the material from the layered phase to the spinel phase, improving the structural stability of the material, and thus making the capacity retention rate of the material , the voltage holding rate is improved to a certain extent, and then through the first sintering and the second sintering with lithium, a lithium-rich manganese-based basic material (intermediate phase material) doped with aluminum in the bulk phase is obtained, and then the intermediate phase material powder is ball-milled and sintered in the absence of oxygen with boric acid, so that B is successfully doped in the interstitial sites of the lithium-rich manganese-based basic material and a thin amorphous B2O3 coating is formed on the surface of the material, which not only further stabilizes the layered structure of the material and effectively hinders the migration of cations, but also reduces the loss of transition metals from the cathode structure, reduces the interface resistance, and is beneficial to the transfer of lithium ions. DETAILED DESCRIPTION
[0057] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.
[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.
[0059] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.
[0060] Example 1
[0061] This embodiment provides a modified lithium-rich manganese-based positive electrode material, wherein the modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material core and a boron oxide Bi2O3 coating layer coated on the surface of the lithium-rich manganese-based material core;
[0062] The lithium-rich manganese-based material core includes a lithium-rich manganese-based basic material Li 1.2 (Ni 1 / 6 Co1 / 6 Mn 4 / 6 ) 0.8 O2, and aluminum and boron doped in the lithium-rich manganese-based base material;
[0063] The molar proportion of aluminum in the lithium-rich manganese-based base material is 0.2%, and the doping mass of boron in the lithium-rich manganese-based core is 3%;
[0064] Based on the mass of the lithium-rich manganese-based material core being 100%, the coating amount of the boron oxide coating layer is 4%.
[0065] The preparation method of the modified lithium-rich manganese-based positive electrode material is as follows:
[0066] Step S1: dissolving a certain amount of nickel sulfate (Ni2SO4·6H2O), cobalt sulfate (CoSO4·7H2O) and manganese sulfate (MnSO4·H2O) in deionized water, wherein the molar ratio of Ni:Co:Mn is 1:1:4, and finally obtaining a mixed ternary liquid A with a concentration of 2 mol / L; dissolving a certain amount of aluminum sulfate (Al2(SO4)3·18H2O) in deionized water and stirring thoroughly to obtain an aluminum salt solution B with a concentration of 3 mol / L, preparing a precipitant Na2CO3 aqueous solution C with a concentration of 2 mol / L, preparing a complexing agent ammonia aqueous solution D with a mass fraction of 20%, and preparing a reaction base solution, wherein the concentration of ammonia in the base solution is 5 g / L;
[0067] Then, solutions A, B, C and D were added to the reaction base liquid in parallel by a peristaltic pump for co-precipitation reaction. During this process, nitrogen was continuously introduced as a protective gas to prevent oxidation of the reaction. The reaction temperature was 50 ° C, the stirring speed was 800 r / min, the pH was controlled at 8.0 ± 0.2, and the reaction was carried out for 15 h. After the reaction was completed, the reaction slurry was aged. After aging, the co-precipitated particles were filtered and washed with deionized water and ethanol 5 times until SO4 2- The precipitate was separated, dried in an oven at 80°C for 24 h, and finally sieved to obtain an aluminum-doped lithium-rich manganese-based carbonate precursor;
[0068] Step S2: The aluminum-doped lithium-rich manganese-based carbonate precursor powder obtained above (step S1) is heated to 500°C in an air atmosphere at a heating rate of 5°C / min and subjected to a first sintering for 6 hours to obtain an oxide precursor, and then the oxide precursor powder is uniformly mixed with Li2CO3 at a molar ratio of 1:0.6, and the above mixed material is heated to 900°C at a heating rate of 5°C / min and subjected to a second sintering for 10 hours to obtain an intermediate phase material, wherein the intermediate material is a lithium-rich manganese-based base material doped with aluminum;
[0069] Step S3: The intermediate phase material (step S2) was ball-milled with boric acid (H3BO3) at a speed of 100 rpm for 1.5 h using a planetary ball mill under an Ar atmosphere. The ball-milled powder was then heated to 300°C under vacuum for a third sintering for 5 h to achieve B doping and boron oxide coating, thereby obtaining the modified lithium-rich manganese-based positive electrode material.
[0070] Example 2
[0071] This embodiment provides a modified lithium-rich manganese-based positive electrode material, wherein the modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material core and a boron oxide Bi2O3 coating layer coated on the surface of the lithium-rich manganese-based material core;
[0072] The lithium-rich manganese-based material core includes a lithium-rich manganese-based basic material Li 1.2 (Ni 1 / 6 Co 1 / 6 Mn 4 / 6 ) 0.8 O2, and aluminum and boron doped in the lithium-rich manganese-based base material;
[0073] The molar proportion of aluminum in the lithium-rich manganese-based base material is 0.1%, and the doping mass of boron in the lithium-rich manganese-based core is 5%;
[0074] Based on the mass of the lithium-rich manganese-based material core being 100%, the coating amount of the boron oxide coating layer is 2%.
[0075] The preparation method of the modified lithium-rich manganese-based positive electrode material is as follows:
[0076] Step S1: dissolving a certain amount of nickel sulfate (Ni2SO4·6H2O), cobalt sulfate (CoSO4·7H2O) and manganese sulfate (MnSO4·H2O) in deionized water, wherein the molar ratio of Ni:Co:Mn is 1:1:4, and finally obtaining a mixed ternary liquid A with a concentration of 1.5 mol / L; dissolving a certain amount of aluminum sulfate (Al2(SO4)3·18H2O) in deionized water and stirring thoroughly to obtain an aluminum salt solution B with a concentration of 2 mol / L, preparing a precipitant Na2CO3 aqueous solution C with a concentration of 1.5 mol / L, preparing a complexing agent ammonia aqueous solution D with a mass fraction of 20%, and preparing a reaction base solution, wherein the concentration of ammonia in the base solution is 5 g / L;
[0077] Then, solutions A, B, C and D were added to the reaction base solution in parallel by a peristaltic pump for co-precipitation reaction. During this process, nitrogen was continuously introduced as a protective gas to prevent oxidation of the reaction. The reaction temperature was 40 ° C, the stirring speed was 600 r / min, the pH was controlled at 7.5 ± 0.2, and the reaction was carried out for 10 h. After the reaction was completed, the reaction slurry was aged. After aging, the co-precipitated particles were filtered and washed with deionized water and ethanol 5 times until SO4 2- The precipitate was separated, dried in an oven at 80°C for 24 h, and finally sieved to obtain an aluminum-doped lithium-rich manganese-based carbonate precursor;
[0078] Step S2: The aluminum-doped lithium-rich manganese-based carbonate precursor powder obtained above (step S1) is heated to 300°C in an air atmosphere at a heating rate of 5°C / min and sintered for 10 hours to obtain an oxide precursor, and then the oxide precursor powder is mixed with Li2CO3 at a molar ratio of 1:0.6. The mixed material is heated to 1100°C at a heating rate of 5°C / min and sintered for a second time for 8 hours to obtain an intermediate phase material, wherein the intermediate material is a lithium-rich manganese-based base material doped with aluminum;
[0079] Step S3: The intermediate phase material (step S2) was ball-milled with boric acid (H3BO3) at a speed of 200 rpm for 1.5 h using a planetary ball mill under an Ar atmosphere. The ball-milled powder was then heated to 400°C under vacuum for a third sintering for 5 h to achieve B doping and boron oxide coating, thereby obtaining the modified lithium-rich manganese-based positive electrode material.
[0080] Example 3
[0081] This embodiment provides a modified lithium-rich manganese-based positive electrode material, wherein the modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material core and a boron oxide Bi2O3 coating layer coated on the surface of the lithium-rich manganese-based material core;
[0082] The lithium-rich manganese-based material core includes a lithium-rich manganese-based basic material Li 1.2 (Ni 1 / 6 Co 1 / 6 Mn 4 / 6 ) 0.8 O2, and aluminum and boron doped in the lithium-rich manganese-based base material;
[0083] The molar proportion of aluminum in the lithium-rich manganese-based base material is 0.3%, and the doping mass of boron in the lithium-rich manganese-based core is 1%;
[0084] Based on the mass of the lithium-rich manganese-based material core being 100%, the coating amount of the boron oxide coating layer is 2%.
[0085] The preparation method of the modified lithium-rich manganese-based positive electrode material is as follows:
[0086] Step S1: dissolving a certain amount of nickel sulfate (Ni2SO4·6H2O), cobalt sulfate (CoSO4·7H2O) and manganese sulfate (MnSO4·H2O) in deionized water, wherein the molar ratio of Ni:Co:Mn is 1:1:4, and finally obtaining a mixed ternary liquid A with a concentration of 2 mol / L; dissolving a certain amount of aluminum sulfate (Al2(SO4)3·18H2O) in deionized water and stirring thoroughly to obtain an aluminum salt solution B with a concentration of 3 mol / L, preparing a precipitant Na2CO3 aqueous solution C with a concentration of 2 mol / L, preparing a complexing agent ammonia aqueous solution D with a mass fraction of 20%, and preparing a reaction base solution, wherein the concentration of ammonia in the base solution is 5 g / L;
[0087] Then, solutions A, B, C and D were added to the reaction base solution in parallel by a peristaltic pump for co-precipitation reaction. During this process, nitrogen was continuously introduced as a protective gas to prevent oxidation of the reaction. The reaction temperature was 50 ° C, the stirring speed was 800 r / min, the pH was controlled at 8.0 ± 0.2, and the reaction was carried out for 15 h. After the reaction was completed, the reaction slurry was aged. After aging, the co-precipitated particles were filtered and washed with deionized water and ethanol 5 times until SO4 2- The precipitate was separated, dried in an oven at 80°C for 24 h, and finally sieved to obtain an aluminum-doped lithium-rich manganese-based carbonate precursor;
[0088] Step S2: The aluminum-doped lithium-rich manganese-based carbonate precursor powder obtained above (step S1) is heated to 400°C in an air atmosphere at a heating rate of 5°C / min and subjected to a first sintering for 10 hours to obtain an oxide precursor, and then the oxide precursor powder is uniformly mixed with Li2CO3 at a molar ratio of 1:0.6, and the above mixed material is heated to 800°C at a heating rate of 5°C / min and subjected to a second sintering for 15 hours to obtain an intermediate phase material, wherein the intermediate material is a lithium-rich manganese-based base material doped with aluminum;
[0089] Step S3: The intermediate phase material (step S2) was ball-milled with boric acid (H3BO3) at a speed of 100 rpm for 1.5 h using a planetary ball mill under an Ar atmosphere. The ball-milled powder was then heated to 250°C under vacuum for a third sintering for 8 h to achieve B doping and boron oxide coating, thereby obtaining the modified lithium-rich manganese-based positive electrode material.
[0090] Example 4
[0091] The difference between this embodiment and embodiment 1 is that the chemical formula of the lithium-rich manganese-based basic material in this embodiment is Li 1.2 (Ni 0.2 Co 0.2 Mn0.6 ) 0.8 O2.
[0092] In the preparation method, the molar ratio of Ni:Co:Mn in the mixed ternary liquid A is adaptively adjusted to 1:1:3.
[0093] The rest of the preparation methods and parameters were the same as those in Example 1.
[0094] Example 5
[0095] The difference between this embodiment and embodiment 1 is that in this embodiment, the molar proportion of aluminum in the lithium-rich manganese-based base material is 0.5%.
[0096] In the preparation method, the amount of aluminum salt added is adaptively adjusted.
[0097] The rest of the preparation methods and parameters were the same as those in Example 1.
[0098] Example 6
[0099] The difference between this embodiment and embodiment 1 is that the boron doping mass in the lithium-rich manganese-based core in this embodiment is 6%.
[0100] In the preparation method, the amount of boric acid added is adaptively adjusted.
[0101] The rest of the preparation methods and parameters were the same as those in Example 1.
[0102] Example 7
[0103] The difference between this embodiment and embodiment 1 is that in this embodiment, the mass of the lithium-rich manganese-based material core is 100%, and the coating amount of the boron oxide coating layer is 1%.
[0104] In the preparation method, the amount of boric acid added is adaptively adjusted.
[0105] The rest of the preparation methods and parameters were the same as those in Example 1.
[0106] Example 8
[0107] The difference between this embodiment and embodiment 1 is that in this embodiment, the mass of the lithium-rich manganese-based material core is 100%, and the coating amount of the boron oxide coating layer is 8%.
[0108] In the preparation method, the amount of boric acid added is adaptively adjusted.
[0109] The rest of the preparation methods and parameters were the same as those in Example 1.
[0110] Example 9
[0111] The difference between this embodiment and embodiment 1 is that the third sintering in step S3 of this embodiment is performed under a nitrogen atmosphere.
[0112] The rest of the preparation methods and parameters were the same as those in Example 1.
[0113] Example 10
[0114] The difference between this embodiment and embodiment 1 is that in step S3 of this embodiment, the temperature of the third sintering is 200°C.
[0115] The rest of the preparation methods and parameters were the same as those in Example 1.
[0116] Example 11
[0117] The difference between this embodiment and embodiment 1 is that in step S3 of this embodiment, the temperature of the third sintering is 500°C.
[0118] The rest of the preparation methods and parameters were the same as those in Example 1.
[0119] Comparative Example 1
[0120] The difference between this comparative example and Example 1 is that the modified lithium-rich manganese-based positive electrode material in this comparative example is not doped with aluminum.
[0121] In step S1 of the preparation method, no aluminum salt is added.
[0122] The rest of the preparation methods and parameters were the same as those in Example 1.
[0123] Comparative Example 2
[0124] The difference between this comparative example and Example 1 is that the modified lithium-rich manganese-based positive electrode material in this comparative example is not doped with boron and not coated with boron oxide.
[0125] In the preparation method, step S3 is not performed.
[0126] The rest of the preparation methods and parameters were the same as those in Example 1.
[0127] Comparative Example 3
[0128] The difference between this comparative example and Example 1 is that the sintering in step S3 of this comparative example is carried out in an air atmosphere, and the obtained product irreversibly generates Li2O, which completely destroys the electrochemical activity of the material.
[0129] The rest of the preparation methods and parameters were the same as those in Example 1.
[0130] Comparative Example 4
[0131] The difference between this comparative example and Example 1 is that the lithium-rich manganese-based positive electrode material of this comparative example is not doped with aluminum and boron, and does not contain a boron oxide coating layer.
[0132] In the preparation method, in step S1, no aluminum salt is added, and step S3 is not performed.
[0133] [Battery preparation and performance testing]
[0134] I. Battery Preparation
[0135] The modified lithium-rich manganese-based positive electrode materials provided in Examples 1-11 and Comparative Examples 1-4, acetylene black, and PVDF were mixed uniformly in a mass ratio of 8:1:1, dissolved in N-methylpyrrolidone, stirred uniformly, and coated on aluminum foil to prepare a positive electrode sheet;
[0136] The positive electrode sheet, polypropylene separator (Celgrad2400), lithium sheet and electrolyte (1 mol / L LiPF6 dissolved in EC:DEC:EMC (mixed solvent) with a volume ratio of 1:1:1) were assembled in a glove box filled with high-purity argon to obtain a CR2032 button-type lithium-ion battery.
[0137] II Performance Test
[0138] The battery performance tests provided by Examples 1-11 and Comparative Examples 1-4 were conducted under the following conditions:
[0139] (a) First coulombic efficiency: At room temperature of 25°C, the battery charge and discharge voltage range is 2.5-4.6V (vs. Li / Li + ), and the first charge and discharge test was carried out at a rate of 0.1C.
[0140] (b) Cyclic performance test: The battery was tested at room temperature (25°C) in the voltage range of 2.5 to 4.6 V at a charge and discharge rate of 1 C for 200 cycles.
[0141] The test results of the above tests are shown in Table 1.
[0142] Table 1
[0143]
[0144] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.
Claims
1. A modified lithium-rich manganese-based positive electrode material, characterized in that: The modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material core and a boron oxide coating layer coated on the surface of the lithium-rich manganese-based material core; The lithium-rich manganese-based material core includes a lithium-rich manganese-based base material and aluminum and boron doped in the lithium-rich manganese-based base material.
2. The modified lithium-rich manganese-based positive electrode material according to claim 1, characterized in that The general chemical formula of the lithium-rich manganese-based basic material is Li 1+a (Ni x Co y Mn z ) 1-a O2, 0<a<1, x>0, y≥0, z>x, and x+y+z=1; Preferably, the Li 1+a (Ni x Co y Mn z ) 1-a In O2, 0.1≤a≤0.3, 0.5≤z≤0.
9.
3. The modified lithium-rich manganese-based positive electrode material according to claim 1 or 2, characterized in that: The molar proportion of aluminum in the lithium-rich manganese-based base material is 0.1% to 0.3%; Preferably, the boron doping mass in the lithium-rich manganese-based material core is 1-5%.
4. The modified lithium-rich manganese-based positive electrode material according to claim 1 or 2, characterized in that: Taking the mass of the lithium-rich manganese-based material core as 100%, the coating amount of the boron oxide coating layer is 2% to 6%.
5. A method for preparing a modified lithium-rich manganese-based positive electrode material according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) mixing a manganese-based main metal element solution, an aluminum salt solution, a precipitant solution, and a complexing agent solution to perform a coprecipitation reaction to obtain an aluminum-doped lithium-rich manganese-based carbonate precursor material; (2) performing a first sintering on the aluminum-doped lithium-rich manganese-based carbonate precursor material to obtain an oxide precursor; mixing a lithium source with the oxide precursor and performing a second sintering to obtain an intermediate phase material; (3) mixing the intermediate phase material with a boron source and performing oxygen-free sintering to obtain the modified lithium-rich manganese-based positive electrode material.
6. The preparation method according to claim 5, characterized in that The concentration of the manganese-based main metal element solution in step (1) is 0.5 to 2 mol / L; Preferably, the concentration of the aluminum salt solution in step (1) is 1 to 3 mol / L; Preferably, the precipitant in step (1) comprises a carbonate precipitant; Preferably, the temperature of the coprecipitation reaction in step (1) is 40-60° C., the pH value of the coprecipitation reaction is 7-9, and the coprecipitation reaction is carried out at a rotation speed of 500-1000 rpm; Preferably, in step (1), the molar amount of aluminum doped in the lithium-rich manganese-based carbonate precursor material is 0.1% to 0.3%.
7. The preparation method according to claim 5, characterized in that Step (2) both the first sintering and the second sintering are performed in an oxygen-containing atmosphere; Preferably, the sintering temperature of the first sintering in step (2) is 300-500° C., and the sintering time of the first sintering is 1-10 hours; Preferably, the sintering temperature of the second sintering in step (2) is 800-1200° C., and the sintering time of the second sintering is 8-24 hours.
8. The preparation method according to claim 5, characterized in that The boron source in step (3) includes boric acid.
9. The preparation method according to claim 5 or 8, characterized in that: The oxygen-free sintering in step (3) includes vacuum sintering and / or protective atmosphere sintering, preferably vacuum sintering; Preferably, the mixing method in step (3) comprises ball milling under a protective atmosphere, and the rotation speed of the ball milling is 50 to 300 rpm; Preferably, the sintering temperature of the oxygen-free sintering in step (3) is 250-400° C., and the sintering time of the oxygen-free sintering is 2-8 hours.
10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the modified lithium-rich manganese-based positive electrode material according to any one of claims 1 to 4 or the modified lithium-rich manganese-based positive electrode material prepared by the preparation method according to any one of claims 5 to 9.