Lithium-rich manganese-based positive electrode material with in-situ spinel phase and preparation method of lithium-rich manganese-based positive electrode material

Abstract

The invention discloses a lithium-rich manganese-based positive electrode material with an in-situ spinel phase and a preparation method of the lithium-rich manganese-based positive electrode material, and belongs to the technical field of synthesis of lithium-rich manganese-based materials, the material has a layered-spinel integrated structure generated in situ in a layered structure matrix, and the spinel phase is uniformly distributed in a layered lattice and forms a coherent interface with a layered phase; the molar ratio of Mn < 3 + > to Mn < 4 + > in the material is 0.05-0.20; the D50 particle size of the material is 2-10 [mu] m, and the particles are spherical or sphere-like. According to the method, the uniformly distributed spinel phase can be generated in situ in the layered matrix, and a coherent interface is formed, so that the dynamic performance and the rate capability are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-rich manganese-based material synthesis technology, specifically to a lithium-rich manganese-based cathode material with an in-situ spinel phase and its preparation method. Background Technology

[0002] Lithium-rich manganese-based cathode materials (generally of the formula (1-xy)Li2MnO3·xLiNi0.5Mn0.5O2·yLiNiO2) are considered as candidate materials for next-generation high-energy-density lithium-ion batteries due to their high specific capacity (>250mAh / g) and low cost. However, they still face three major bottlenecks in practical applications: (1) low initial coulombic efficiency (usually <80%), which is due to irreversible oxygen evolution; (2) continuous decay of the voltage plateau during cycling, which leads to a rapid decrease in energy density; and (3) poor rate performance, which limits their application in fast charging scenarios.

[0003] Therefore, there is an urgent need for a lithium-rich manganese-based cathode material and method that can precisely control the content and distribution of spinel phase while suppressing oxygen loss and voltage decay. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, one of the objectives of the present invention is to provide a lithium-rich manganese-based cathode material with an in-situ spinel phase, which significantly improves kinetic performance and rate performance by generating a uniformly distributed spinel phase in situ in a layered matrix and forming a coherent interface.

[0005] The second objective of this invention is to provide a method for preparing lithium-rich manganese-based materials by in-situ construction of a uniform spinel phase, which can construct a uniform spinel phase in situ.

[0006] One of the objectives of this invention is achieved through the following technical solution: A lithium-rich manganese-based cathode material with an in-situ spinel phase, the material having an in-situ layered-spinel integrated structure generated in a layered matrix, wherein: the spinel phase is uniformly distributed inside the layered lattice and forms a coherent interface with the layered phase; Mn in the material 3+ With Mn 4+ The molar ratio is 0.05-0.20; The material has a D50 particle size of 2-10 μm, and the particles are spherical or near-spherical.

[0007] Furthermore, the material also contains Co, with a Co doping amount of 0.1–5.0 wt% of the total mass of the material, and Co is present in the form of Co... 3+ The form exists in the transition metal layer.

[0008] Furthermore, the material also contains Sn, with the Sn doping amount being 0.1–0.5 wt% of the total mass of the material, and Sn is present in the form of Sn... 4+ The form forms Sn–O bonds with oxygen and embeds itself in the crystal lattice.

[0009] The second objective of this invention is achieved by the following technical solution: A method for preparing lithium-rich manganese-based materials by in-situ construction of a uniform spinel phase includes the following steps: S1. Provides lithium-rich manganese-based materials; S2. The lithium-rich manganese-based material is mixed with a carbon source, wherein the carbon source is selected from sucrose or glucose, and the amount added is 0.1-1.0 wt% of the mass of the lithium-rich manganese-based material. S3. The mixture obtained in step S2 is subjected to wet sand milling in a sand mill to uniformly mix the carbon source and the lithium-rich manganese-based material. The D90 of the slurry after sand milling is ≤500nm. S4. Spray dry the slurry after sand milling to obtain granulated powder with D50 of 2-10μm; S5. The granulated powder is heat-treated at 400-800℃ for 2-10 hours under a nitrogen atmosphere, so that the carbon source and the lithium-rich manganese-based material undergo a redox reaction, thereby removing some of the Mn. 4+ Restored to Mn 3+ In situ, a uniformly distributed spinel phase is generated to obtain a lithium-rich manganese-based material with an in situ constructed uniform spinel phase, namely, the lithium-rich manganese-based cathode material with an in situ spinel phase.

[0010] Furthermore, in step S2, a metal oxide or metal hydroxide is added, wherein the metal oxide or metal hydroxide is Co(OH)2 or SnO, wherein the amount of Co(OH)2 added is 0.1-5 wt% of the mass of the lithium-rich manganese-based material, and the amount of SnO added is 0.1-0.5 wt% of the mass of the lithium-rich manganese-based material.

[0011] Furthermore, the general chemical formula of the lithium-rich manganese-based material matrix is ​​(1-xy)Li₂MnO₃·xLiNi. 0.5 Mn 0.5 O2·yLiNiO2.

[0012] Furthermore, the grinding process uses zirconia balls with a ball-to-material ratio of (2-5):1 and a grinding time of 2-6 hours.

[0013] Furthermore, in step S2, a fluorine-containing compound or a sulfur-containing compound is added. The fluorine-containing compound is selected from NH4F and LiF, and the amount added is 0.1-1.0 wt%. The sulfur-containing compound is selected from (NH4)2S2O8, and the amount added is 0.05-0.3 wt%.

[0014] Furthermore, F⁻ or S²⁻ is doped into oxygen sites in the material, and the O / F or O / S molar ratio is (0.95-0.99):0.01-0.05.

[0015] Furthermore, in step S2, a conductive polymer monomer is added, the monomer being selected from pyrrole or aniline, and the amount added is 0.5-2.0 wt% of the mass of the lithium-rich manganese-based material. After sand milling, an oxidant is introduced to initiate in-situ polymerization, forming a polypyrrole or polyaniline conductive layer coated on the surface of the particles.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing lithium-rich manganese-based materials by in-situ construction of a uniform spinel phase. The spinel phase is generated in-situ within a layered lattice, forming a coherent interface with the layered phase (verifiable by HRTEM and FFT). This effectively suppresses the uncontrollable phase transition from the layered phase to the spinel phase and the propagation of microcracks during cycling, thereby significantly reducing the voltage decay rate (≤0.5mV / cycle). The uniform spinel phase provides a three-dimensional lithium-ion diffusion channel, improving ionic conductivity. Co doping is known to improve conductivity and electronic conductivity, thus significantly enhancing kinetic performance and rate performance. By precisely controlling Mn... 3+ / Mn 4+ A molar ratio of 0.05-0.20, while activating the Li₂MnO₃ component, avoids / Mn 4+ Excess oxygen evolution reduces the initial irreversible capacity loss, increasing the initial coulombic efficiency to over 85%. The material also contains Sn, with a Sn doping amount of 0.1–0.5 wt% of the total material mass. 4+ The form forms Sn–O bonds with oxygen and is embedded in the lattice to suppress oxygen release and improve cycle stability; the conductive polymer coating (such as polypyrrole) further reduces the interfacial impedance and the 5C capacity retention is ≥80%.

[0017] (2) The present invention provides a method for preparing lithium-rich manganese-based materials by in-situ construction of a uniform spinel phase. The spherical particles (D50=2–10μm) and the spray drying granulation structure ensure the electrode compaction density, so that the carbon source and the lithium-rich manganese-based material are uniformly mixed. After sand milling, the D90 of the slurry is ≤500nm, which shortens the lithium-ion diffusion path and reduces the interface impedance. In step S2, a conductive polymer monomer is also added. The monomer is selected from pyrrole or aniline. The amount added is 0.5-2.0wt% of the mass of the lithium-rich manganese-based material. After sand milling, an oxidant (such as FeCl3) is introduced to initiate in-situ polymerization, forming a polypyrrole or polyaniline conductive layer coated on the particle surface. A continuous conductive network is formed on the particle surface, which improves electron conduction. The 2C / 0.1C capacity retention rate can be ≥80%, which is significantly better than traditional lithium-rich materials (usually <60%). In step S2, a fluorine-containing compound or a sulfur-containing compound is added. The fluorine-containing compound is selected from NH4F and LiF, and the amount added is 0.1-1.0 wt%. The sulfur-containing compound is selected from (NH4)2S2O8, and the amount added is 0.05-0.3 wt%. F / S doping strengthens the M–O bond and suppresses oxygen loss. Detailed Implementation

[0018] The present invention will now be further described in conjunction with specific embodiments. It should be noted that, without conflict, the embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0019] 'In-situ spinel phase' refers to the formation of spinel phase within the layered lattice of lithium-rich manganese-based materials through Mn... 4 The spinel structure formed by the partial reduction of ⁺ to Mn³⁺ and the local transformation has a crystallographic orientation relationship with the layered phase, rather than being an externally added spinel material through physical mixing.

[0020] Example 1

[0021] This embodiment provides a lithium-rich manganese-based cathode material with an in-situ spinel phase. The material has an in-situ layered-spinel integrated structure generated in a layered matrix, wherein the spinel phase is uniformly distributed inside the layered lattice and forms a coherent interface with the layered phase. Mn in the material 3+ With Mn 4+ The molar ratio is 0.20; The material has a D50 particle size of 2 μm and the particles are spherical or near-spherical.

[0022] This embodiment provides a method for preparing lithium-rich manganese-based materials by in-situ construction of a uniform spinel phase, including the following steps: S1. Raw material preparation: Take the chemical formula 0.7Li₂MnO₃·0.3LiNi 0.5 Mn 0.5O2-rich lithium manganese-based material (D50=5μm).

[0023] S2. Carbon source mixing: Weigh 100g of the above materials, add 0.5g of sucrose (0.5wt%), and mix well; S3, Wet sand milling: Add deionized water to prepare a slurry with a solid content of 40%, and mill with zirconia balls (ball-to-material ratio 3:1) for 4 hours, D90=420nm; S4. Spray drying: Inlet air temperature 250℃, outlet air temperature 100℃, to obtain spherical granulated powder with D50=6μm; S5. Heat treatment: Hold at 600℃ for 6 hours under N2 atmosphere, then allow to cool naturally, causing a redox reaction between the carbon source and the lithium-rich manganese-based material, removing some of the Mn. 4+ Restored to Mn 3+ In situ, a uniformly distributed spinel phase is generated to obtain a modified lithium-rich manganese-based cathode material, namely, a lithium-rich manganese-based material with a uniform spinel phase constructed in situ.

[0024] In this embodiment, performance testing (CR2032 button cell, 0.1C, 2.0–4.8V): Initial discharge capacity: 268mAh / g; First-time Coulomb efficiency: 86.2%; 200-cycle capacity retention: 78.6%; Voltage decay rate: 0.42mV / cycle; HRTEM showed that the spinel phase (~10 nm) was uniformly distributed and coherent with the layered phase; Rietveld refined the spinel phase to 12.3% by volume. XPS measured Mn 3+ / Mn 4+ =0.38; Capacity retention at 2C / 0.1C rate: 72.1%.

[0025] In this embodiment, the general chemical formula of the lithium-rich manganese-based material matrix is ​​(1-xy)Li2MnO3·xLiNi0.5Mn0.5O2·yLiNiO2.

[0026] In this embodiment, zirconia balls are used for sand milling, the ball-to-material ratio is 2:1, and the sand milling time is 6 hours.

[0027] Example 2

[0028] This embodiment provides a lithium-rich manganese-based cathode material with an in-situ spinel phase. The material has an in-situ layered-spinel integrated structure generated in a layered matrix, wherein the spinel phase is uniformly distributed inside the layered lattice and forms a coherent interface with the layered phase. Mn in the material 3+ With Mn 4+ The molar ratio is 0.15; The material has a D50 particle size of 10 μm and the particles are spherical or near-spherical.

[0029] This embodiment provides a method for preparing lithium-rich manganese-based materials by in-situ construction of a uniform spinel phase, including the following steps: S1. Raw material preparation: Take the chemical formula 0.7Li₂MnO₃·0.3LiNi 0.5 Mn 0.5 O2-rich lithium-manganese-based materials (D50=5μm); S2. Carbon source mixing: Weigh 100g of the above materials, add 0.5g of sucrose (0.5wt%), and mix well; S3, Wet sand milling: Add deionized water to prepare a slurry with a solid content of 40%, and mill with zirconia balls (ball-to-material ratio 3:1) for 4 hours, D90=420nm; S4. Spray drying: Inlet air temperature 250℃, outlet air temperature 100℃, to obtain spherical granulated powder with D50=6μm; S5. Heat treatment: Hold at 600℃ for 6 hours under N2 atmosphere, then allow to cool naturally, causing a redox reaction between the carbon source and the lithium-rich manganese-based material, removing some of the Mn. 4+ Restored to Mn 3+ In situ, a uniformly distributed spinel phase is generated to obtain a modified lithium-rich manganese-based cathode material, namely, a lithium-rich manganese-based material with a uniform spinel phase constructed in situ.

[0030] In this embodiment, a metal hydroxide, Co(OH)2, is added in step S2. The amount of Co(OH)2 added is 0.1 wt% of the mass of the lithium-rich manganese-based material.

[0031] In this embodiment, zirconia balls are used for sand milling, the ball-to-material ratio is 3:1, and the sand milling time is 2 hours.

[0032] Example 3

[0033] This embodiment provides a lithium-rich manganese-based cathode material with an in-situ spinel phase. The material has an in-situ layered-spinel integrated structure generated in a layered matrix, wherein the spinel phase is uniformly distributed inside the layered lattice and forms a coherent interface with the layered phase. Mn in the material 3+ With Mn 4+ The molar ratio is 0.05; The material has a D50 particle size of 8 μm and the particles are spherical or near-spherical.

[0034] This embodiment provides a method for preparing lithium-rich manganese-based materials by in-situ construction of a uniform spinel phase, including the following steps: S1. Raw material preparation: Take the chemical formula 0.7Li₂MnO₃·0.3LiNi 0.5 Mn 0.5 O2-rich lithium manganese-based material (D50=5μm).

[0035] S2. Carbon source mixing: Weigh 100g of the above materials, add 0.5g of sucrose (0.5wt%), and mix well; S3, Wet sand milling: Add deionized water to prepare a slurry with a solid content of 40%, and mill with zirconia balls (ball-to-material ratio 3:1) for 4 hours, D90=420nm; S4. Spray drying: Inlet air temperature 250℃, outlet air temperature 100℃, to obtain spherical granulated powder with D50=6μm; S5. Heat treatment: Hold at 600℃ for 6 hours under N2 atmosphere, then allow to cool naturally, causing a redox reaction between the carbon source and the lithium-rich manganese-based material, removing some of the Mn. 4+ Restored to Mn 3+ In situ, a uniformly distributed spinel phase is generated to obtain a modified lithium-rich manganese-based cathode material, namely, a lithium-rich manganese-based material with a uniform spinel phase constructed in situ.

[0036] In this embodiment, a metal hydroxide, namely Co(OH)2, is added in step S2. The amount of Co(OH)2 added is 5 wt% of the mass of the lithium-rich manganese-based material.

[0037] In this embodiment, zirconia balls are used for sand milling, the ball-to-material ratio is 5:1, and the sand milling time is 3 hours.

[0038] Example 4

[0039] Co-doping + F-doping synergistic effect Based on Example 1, in step S2, the metal oxide SnO and 0.5wt% NH4F are added. The amount of SnO added is 0.1-0.5wt% of the mass of the lithium-rich manganese-based material, and the other conditions remain unchanged.

[0040] Performance improvements: The initial efficacy has been improved to 88.1% (Sn is used to inhibit oxygen release, and F inhibits oxygen evolution). The capacity retention rate after 200 weeks was 85.3%, which is higher than that of Example 1; XPS display surface Mn 3+ The content is reduced, and the interface is more stable.

[0041] Example 5

[0042] Conductive polymer coating In step 2 of Example 1, 1.0 wt% pyrrole was added, and after sand milling, 0.1 M FeCl3 solution was added dropwise to initiate polymerization. The mixture was stirred at 60°C for 2 hours, filtered and dried, and then proceeded to steps 4-5.

[0043] Performance improvements: Capacity retention at 2C / 0.1C rate: 83.7%, higher than in Example 1; EIS showed a 40% reduction in charge transfer impedance Rct.

[0044] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A lithium-rich manganese-based cathode material with an in-situ spinel phase, characterized in that, The material has an in-situ generated layered-spinel integrated structure in a layered matrix, wherein the spinel phase is uniformly distributed inside the layered lattice and forms a coherent interface with the layered phase. Mn in the material 3+ With Mn 4+ The molar ratio is 0.05-0.20; The material has a D50 particle size of 2-10 μm, and the particles are spherical or near-spherical.

2. The lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 1, characterized in that, The material also contains Co, with a Co doping amount of 0.1–5.0 wt% of the total mass of the material. 3+ The form exists in the transition metal layer.

3. The lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 1, characterized in that, The material also contains Sn, with a Sn doping amount of 0.1–0.5 wt% of the total mass of the material. 4+ The form forms Sn–O bonds with oxygen and embeds itself in the crystal lattice.

4. A method for preparing a lithium-rich manganese-based cathode material with an in-situ spinel phase as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Provides lithium-rich manganese-based materials; S2. The lithium-rich manganese-based material is mixed with a carbon source, wherein the carbon source is selected from sucrose or glucose, and the amount added is 0.1-1.0 wt% of the mass of the lithium-rich manganese-based material. S3. The mixture obtained in step S2 is subjected to wet sand milling in a sand mill to make the carbon source and the lithium-rich manganese-based material uniformly mixed. The D90 of the slurry after sand milling is ≤500nm. S4. Spray dry the slurry after sand milling to obtain granulated powder with D50 of 2-10μm; S5. The granulated powder is heat-treated at 400-800℃ for 2-10 hours under a nitrogen atmosphere, so that the carbon source and the lithium-rich manganese-based material undergo a redox reaction, thereby removing some of the Mn. 4+ Restored to Mn 3+ In situ, a uniformly distributed spinel phase is generated to obtain a lithium-rich manganese-based material with an in situ constructed uniform spinel phase, namely, the lithium-rich manganese-based cathode material with an in situ spinel phase.

5. The method for preparing a lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 4, characterized in that, In step S2, a metal oxide or metal hydroxide is added, wherein the metal oxide or metal hydroxide is Co(OH)2 or SnO, wherein the amount of Co(OH)2 added is 0.1-5 wt% of the mass of the lithium-rich manganese-based material, and the amount of SnO added is 0.1-0.5 wt% of the mass of the lithium-rich manganese-based material.

6. The method for preparing a lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 4, characterized in that, The general chemical formula of the lithium-rich manganese-based material matrix is ​​(1-xy)Li₂MnO₃·xLiNi. 0.5 Mn 0.5 O2·yLiNiO2.

7. The method for preparing a lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 6, characterized in that, The grinding process uses zirconia balls with a ball-to-material ratio of (2-5):1 and a grinding time of 2-6 hours.

8. The method for preparing a lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 4, characterized in that, In step S2, a fluorine-containing compound or a sulfur-containing compound is added. The fluorine-containing compound is selected from NH4F and LiF, and the amount added is 0.1-1.0 wt%. The sulfur-containing compound is selected from (NH4)2S2O8, and the amount added is 0.05-0.3 wt%.

9. The method for preparing a lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 6, characterized in that, The material is doped with F⁻ or S²⁻ at oxygen sites, and the O / F or O / S molar ratio is (0.95-0.99):0.01-0.

05.

10. The method for preparing a lithium-rich manganese-based cathode material with an in-situ spinel phase as described in claim 6, characterized in that, In step S2, a conductive polymer monomer is added, which is selected from pyrrole or aniline. The amount added is 0.5-2.0 wt% of the mass of the lithium-rich manganese-based material. After sand milling, an oxidant is introduced to initiate in-situ polymerization to form a polypyrrole or polyaniline conductive layer coated on the surface of the particles.