High-concentration anti-site defect lithium iron manganese phosphate material and preparation method thereof
By introducing the surfactant tetraethylene glycol during the synthesis of lithium manganese iron phosphate, the formation of two-dimensional or three-dimensional diffusion channels by controlling the growth of crystal faces can be achieved. This solves the problem of lithium-ion diffusion path blockage caused by Li+/Fe2+ antisite defects and improves the electrical conductivity and electrochemical performance of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2024-04-08
- Publication Date
- 2026-06-23
Smart Images
Figure CN118206095B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a lithium manganese iron phosphate and its preparation method. Background Technology
[0002] In recent years, the lithium-ion battery industry, as a major category under the new energy industry, has undergone a complete transformation of the battery industry thanks to its high energy density, high specific capacity, and good cycle performance, under the long-term support of policies. With technological breakthroughs in structure such as CTP and blade batteries, the system integration efficiency of lithium iron phosphate batteries has been continuously improved, and the energy density has been enhanced. In addition, the sharp rise in the price of upstream raw materials for ternary batteries since 2021 has contributed to a significant increase in the installed capacity of lithium iron phosphate batteries.
[0003] Lithium manganese phosphate and lithium iron phosphate have similar structures, both being olivine structures. They have the same specific capacity, higher operating voltage (4.1V) and specific energy (701Wh / kg), and lower cost. However, they have greater internal lattice resistance, slower lithium-ion diffusion rates, and lower intrinsic conductivity (<10). -10 The manganese-induced Jahn-Teller effect (S / cm) during cycling can easily lead to structural degradation, affecting the electrochemical performance of the material. The electron diffusion bandgap in lithium manganese phosphate is as high as 2 eV, classifying it as an insulator. Combining lithium manganese phosphate and lithium iron phosphate to form lithium manganese iron phosphate (LFP) can achieve a higher voltage platform than LFP while maintaining material safety, thus improving energy density. Therefore, it is expected to gradually replace LFP in the continuously developing power battery and low-cost consumer battery markets.
[0004] Currently, the main methods for synthesizing lithium manganese iron phosphate include high-temperature solid-state synthesis, hydrothermal synthesis, and sol-gel synthesis. However, all of these methods inevitably induce a certain degree of Li₂ oxidation. + / Fe 2+ Inversion defects. Since, theoretically, the diffusion channels for lithium ions in the olivine structure are one-dimensional tubular structures, it is generally believed that Li... + / Fe 2+ Antisite defects can block lithium-ion diffusion pathways, degrading material properties. Numerous studies have attempted to reduce Li-ion diffusion during synthesis. + / Fe 2+ The generation of antisite defects, such as through fluorine or nitrogen doping during synthesis, adjustment of reaction parameters during hydrothermal synthesis, and subsequent calcination, can effectively improve the electrochemical performance of lithium iron phosphate materials. Recent studies have shown that, at appropriate concentrations, these antisite defects can interconnect partially blocked one-dimensional lithium-ion diffusion channels, forming two-dimensional or three-dimensional lithium-ion diffusion channels. This effectively promotes lithium-ion diffusion along the
[100] and
[001] directions, thereby increasing the intrinsic conductivity of lithium manganese iron phosphate and improving the material's cycle stability. Summary of the Invention
[0005] To address the Li-induced oxidation during the synthesis of lithium manganese iron phosphate + / Fe 2+ To address the performance degradation caused by antisite defects, this invention presents a high-concentration antisite defect lithium manganese iron phosphate material and its preparation method. By utilizing the inhibitory effect of the surfactant tetraethylene glycol on the growth of different crystal planes to varying degrees, the synthesis process kinetics are influenced, thereby achieving the desired performance degradation of Li. + / Fe 2+ By rationally controlling the properties and concentration of antisite defects, the intrinsic conductivity of the material can be improved, thereby further optimizing the electrochemical performance of lithium manganese iron phosphate materials.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] In a first aspect, the present invention provides a method for preparing a high-concentration anti-site defect lithium manganese iron phosphate material, the preparation method comprising the following steps:
[0008] (1) First, prepare manganese salt solution, iron salt solution and phosphorus salt solution of a certain concentration. Mix manganese salt, iron salt, phosphorus salt and lithium salt solution of a certain concentration range and antioxidant in a certain order into surfactant tetraethylene glycol and disperse evenly. Pour into high pressure vessel for hydrothermal reaction, wash, and obtain high concentration of antisite defect lithium manganese iron phosphate.
[0009] (2) The obtained product is mixed into a certain proportion of alcohol and aqueous solution, and phenolic compounds and ester compounds are added in a certain order to react. After filtration, washing, drying, and calcination in an inert atmosphere, a high-concentration anti-site defect lithium manganese iron phosphate material is obtained.
[0010] Preferably, the lithium source in step (1) includes any one or a combination of two or more of lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, or lithium acetate, and the concentration of the lithium salt solution is 0.7 to 3.0 M.
[0011] Preferably, the manganese source in step (1) includes any one or a combination of two or more of manganese sulfate, manganese nitrate, manganese oxalate, or manganese acetate, and the concentration of the manganese salt solution is 0.2 to 1.0 M.
[0012] Preferably, the iron source in step (1) includes any one or a combination of two or more of ferric sulfate, ferric nitrate, ferrous nitrate, ferric oxalate, or ferrous oxalate, and the concentration of the iron salt solution is 0.2 to 1.0 M.
[0013] Preferably, the phosphorus source in step (1) includes any one or a combination of phosphate or phosphoric acid; preferably, the phosphate includes any one or a combination of ammonium dihydrogen phosphate or lithium dihydrogen phosphate, and the concentration of the phosphate solution is 1.0 to 4.0 M.
[0014] Preferably, the antioxidant in step (1) includes any one or a combination of two of ascorbic acid or citric acid;
[0015] Preferably, the surfactant in step (1) includes tetraethylene glycol, the amount of tetraethylene glycol used is 1 to 10 wt. of the lithium manganese iron phosphate production, and the volume of the tetraethylene glycol solution accounts for 20% to 80% of the total solution volume;
[0016] Preferably, the organic dispersant in step (1) includes any one or a combination of two or more of ethanol, ethylene glycol, polyethylene glycol, or polyvinyl alcohol;
[0017] Preferably, in step (1), the order of adding manganese salt, iron salt, phosphate salt, lithium salt solution and antioxidant to tetraethylene glycol is manganese salt solution, iron salt solution, phosphate salt solution, lithium salt solution and antioxidant;
[0018] Preferably, the temperature of the hydrothermal reaction in step (1) is 150-250°C, and the hydrothermal reaction time is 8-16 hours.
[0019] Preferably, the phenolic compound in step (2) includes any one of phenol, resorcinol, or cresol;
[0020] Preferably, the aldehyde compounds in step (2) include any one of formaldehyde, acetaldehyde, and furfural;
[0021] Preferably, the dispersant in step (2) includes any one of cetyltrimethylammonium bromide, sodium sulfonated hydroxymethylpropane sulfonate, or sodium alkylbenzene sulfonate;
[0022] Preferably, the catalyst in step (2) is any one or more of ammonia, sulfuric acid, sodium hydroxide, or hydrochloric acid.
[0023] Preferably, in step (2), the order of adding phenolic compounds, aldehyde compounds, dispersants and catalysts is phenolic compounds, dispersants, catalysts and aldehyde compounds; preferably, the aldehyde compounds need to be stirred and ultrasonically dispersed for 0.5 to 2 hours before being added.
[0024] Preferably, the phenolic polymerization reaction time in step (2) is 8–15 h;
[0025] Preferably, the inert atmosphere in the roasting process in step (2) is generated by argon or nitrogen;
[0026] Preferably, the roasting temperature in step (2) is 650–750°C; the roasting time is 8–15 h.
[0027] In a second aspect, the present invention provides a high-concentration anti-site defect lithium manganese iron phosphate material, wherein the high-concentration anti-site defect lithium manganese iron phosphate material is obtained by the preparation method described in the first aspect:
[0028] Preferably, the lithium manganese iron phosphate material comprises lithium manganese iron phosphate with a certain concentration of antisite defects and a surface carbon coating layer;
[0029] Preferably, the primary particle size of the lithium manganese iron phosphate material is 20–900 nm;
[0030] Preferably, the carbon layer thickness on the surface of the lithium manganese iron phosphate material is 3–10 nm.
[0031] Preferably, Li in lithium manganese iron phosphate + Position and Mn 2+ / Fe 2+ The antisite defect concentration is 0%, meaning no antisite occurs at all. The high-concentration antisite defect lithium manganese iron phosphate material has an antisite defect concentration between 3.0% and 7.0%. Preferably, the synthesized high-concentration lithium manganese iron phosphate material has the chemical formula LiMn. x Fe y PO4, where 0.3≤x≤0.7, 0.3≤y≤0.7, and x+y=1.
[0032] The beneficial effects of this invention are as follows: This invention introduces the surfactant tetraethylene glycol to control the growth of each crystal facet of lithium manganese iron phosphate during hydrothermal synthesis, thereby adjusting the cell parameters of the material and inducing Li + / Fe 2+ The formation of inversion defects will partially block the one-dimensional Li + The diffusion channels are interconnected, forming two-dimensional or three-dimensional Li + Diffusion channels effectively promote Li + Diffusion along the
[100] and
[001] directions improves the intrinsic conductivity of lithium manganese iron phosphate, thereby obtaining a cathode material with high specific capacity, excellent rate performance and cycle performance. Attached Figure Description
[0033] Figure 1 Scanning electron microscope image of the lithium manganese iron phosphate composite material provided in Example 1 Detailed Implementation
[0034] Example 1
[0035] This embodiment provides a lithium manganese iron phosphate material with a high concentration of antisite defects.
[0036] In terms of molar number, the molar ratio of (Fe+Mn) / P in the lithium manganese iron phosphate is 1, and the molar ratio of Li /
[0037] The molar ratio of (Fe+Mn) is 3, the molar ratio of Mn / P is 0.6, and the Li in the lithium manganese iron phosphate is... + / Fe 2+ The concentration of inversion defects was 5.27%.
[0038] The high-concentration antisite defect lithium manganese iron phosphate material was prepared by the following method:
[0039] (1) Manganese salt solution, iron salt solution, phosphate salt solution and lithium salt solution of a certain concentration were prepared by using manganese sulfate, ferric sulfate, ammonium dihydrogen phosphate and lithium hydroxide respectively. The solutions were ultrasonically dispersed and stirred to obtain a homogeneous solution. The concentration of the manganese salt solution was 0.5M, the concentration of the iron salt solution was 0.5M, the concentration of the phosphate salt solution was 1.0M and the concentration of the lithium salt solution was 1.0M.
[0040] (2) First, the manganese salt solution, iron salt solution, and ascorbic acid are mixed into the tetraethylene glycol solution and ultrasonically dispersed and stirred for 0.5 h. The molar ratio of manganese, iron, and ascorbic acid is 3:2:0.025, and the amount of tetraethylene glycol used is 5 wt.% of the theoretical lithium manganese iron phosphate yield. Then, lithium salt solution and phosphate solution are gradually added, and ultrasonic dispersion and stirring are continued for 0.5 h. The molar ratio of manganese, iron, lithium, and phosphorus is 3:2:15:5.1. The mixed and dispersed solution is poured into a polytetrafluoroethylene-lined reactor and reacted at 200 °C for 10 h.
[0041] (3) The solution after the reaction was completed was separated in a centrifuge to obtain lithium iron manganese phosphate. The lithium iron manganese phosphate obtained by centrifugation was mixed into a mixed solvent of water and alcohol (volume ratio of 14:6) and ultrasonically stirred for 0.5 h. Then, hexadecyltrimethylammonium bromide, resorcinol and ammonia monohydrate were added, wherein the molar ratio of lithium iron manganese phosphate, hexadecyltrimethylammonium bromide, resorcinol and ammonia monohydrate was 1:0.05:0.025:0.01. Ultrasonic stirring was continued for 0.5 h. Finally, formaldehyde was added and the reaction was stirred for 12 h. Phenolic resin coated lithium iron manganese phosphate was obtained by centrifugation and dried in a vacuum oven at 90 °C for 6 h.
[0042] (4) The dried lithium manganese iron phosphate material was reacted at 700°C for 10 h under an argon atmosphere to obtain the high-concentration antisite defect lithium manganese iron phosphate material.
[0043] Example 2
[0044] In terms of molar number, the molar ratio of (Fe+Mn) / P in the lithium manganese iron phosphate is 1, and the molar ratio of Li /
[0045] The molar ratio of (Fe+Mn) is 3, the molar ratio of Mn / P is 0.5, and the Li in the lithium manganese iron phosphate is... + / Fe 2+ The concentration of inversion defects was 4.47%.
[0046] The high-concentration antisite defect lithium manganese iron phosphate material was prepared by the following method:
[0047] (1) Manganese salt solution, iron salt solution, phosphate salt solution and lithium salt solution of a certain concentration were prepared by using manganese sulfate, ferric sulfate, ammonium dihydrogen phosphate and lithium hydroxide respectively. The solutions were ultrasonically dispersed and stirred to obtain a homogeneous solution. The concentration of the manganese salt solution was 0.5M, the concentration of the iron salt solution was 0.5M, the concentration of the phosphate salt solution was 1.0M and the concentration of the lithium salt solution was 1.0M.
[0048] (2) First, the manganese salt solution, iron salt solution, and ascorbic acid are mixed into the tetraethylene glycol solution and ultrasonically dispersed and stirred for 0.5 h. The molar ratio of manganese, iron, and ascorbic acid is 1:1:0.01, and the amount of tetraethylene glycol used is 3 wt.% of the theoretical production of lithium manganese iron phosphate. Then, lithium salt solution and phosphate solution are gradually added, and ultrasonic dispersion and stirring are continued for 0.5 h. The molar ratio of manganese, iron, lithium, and phosphorus is 1:1:6:2.05. The mixed and dispersed solution is poured into a polytetrafluoroethylene-lined reactor and reacted at 200 °C for 10 h.
[0049] (3) The solution after the reaction was completed was separated in a centrifuge to obtain lithium iron manganese phosphate. The lithium iron manganese phosphate obtained by centrifugation was mixed into a mixed solvent of water and alcohol (volume ratio of 14:6) and ultrasonically stirred for 0.5 h. Then, hexadecyltrimethylammonium bromide, resorcinol and ammonia monohydrate were added, wherein the molar ratio of lithium iron manganese phosphate, hexadecyltrimethylammonium bromide, resorcinol and ammonia monohydrate was 1:0.05:0.025:0.01. Ultrasonic stirring was continued for 0.5 h. Finally, formaldehyde was added and the reaction was stirred for 12 h. Phenolic resin coated lithium iron manganese phosphate was obtained by centrifugation and dried in a vacuum oven at 90 °C for 6 h.
[0050] (4) The dried lithium manganese iron phosphate material was reacted at 700°C for 10 h under an argon atmosphere to obtain the high-concentration antisite defect lithium manganese iron phosphate material.
Claims
1. A high-concentration anti-site defect lithium manganese iron phosphate material, comprising a high-concentration anti-site defect lithium manganese iron phosphate material body and a surface carbon coating layer, characterized in that, The high-concentration antisite defect lithium manganese iron phosphate material has a bulk particle size of 100–600 nm; with Li in lithium manganese iron phosphate + Position and Mn 2+ / Fe 2+ The antisite defect concentration is 0%, meaning that no antisite defects occur at all, and the antisite defect concentration in the high-concentration antisite defect lithium manganese iron phosphate material body is between 3.0% and 7.0%. The synthesized high-concentration lithium manganese iron phosphate material has the chemical formula LiMn x Fe y PO4, where 0.3≤x≤0.7, 0.3≤y≤0.7, and x+y=1; The preparation method of the high-concentration anti-site defect lithium manganese iron phosphate material includes the following steps: (1) First, prepare manganese salt solution, iron salt solution and phosphorus salt solution of a certain concentration. Mix manganese salt solution, iron salt solution, phosphorus salt solution, lithium salt solution and antioxidant of a certain concentration range into tetraethylene glycol solution and disperse evenly. Pour into high pressure vessel for hydrothermal reaction, wash, and obtain high concentration of antisite defect lithium manganese iron phosphate. (2) The high-concentration anti-site defect lithium manganese iron phosphate obtained in step (1) is mixed into a certain proportion of alcohol and aqueous solution, phenolic compounds, aldehyde compounds, dispersants and catalysts are added and stirred to react, filtered, washed, dried and then calcined in an inert atmosphere to obtain carbon-coated high-concentration anti-site defect lithium manganese iron phosphate material.
2. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, The lithium salt solution includes any one or a combination of two or more of lithium hydroxide solution, lithium carbonate solution, lithium dihydrogen phosphate solution, and lithium acetate solution; The manganese salt solution includes any one or a combination of two or more of manganese sulfate solution, manganese nitrate solution, manganese oxalate solution, and manganese acetate solution. The iron salt solution includes any one or a combination of two or more of the following: ferric sulfate solution, ferric nitrate solution, ferrous nitrate solution, ferric oxalate solution, and ferrous oxalate solution. The phosphate salt solution includes any one or a combination of two of the following: ammonium dihydrogen phosphate solution and lithium dihydrogen phosphate solution. Antioxidants include any one or a combination of two of ascorbic acid and citric acid.
3. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, In step (1), the concentration of the manganese salt solution is 0.2–1.0 M; the concentration of the iron salt solution is 0.2–1.0 M; the concentration of the phosphate salt solution is 1.0–4.0 M; and the concentration of the lithium salt solution is 0.7–3.0 M. The molar ratio of phosphate, lithium, manganese and iron salts is 1:3:x:y, where 0.3≤x≤0.7, 0.3≤y≤0.7, and x+y=1.
4. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, In step (1), the amount of tetraethylene glycol used is 1 to 10 wt. of the production of lithium manganese iron phosphate, and the volume of the tetraethylene glycol solution accounts for 20% to 80% of the total solution volume.
5. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, In step (1), the temperature of the hydrothermal reaction is 150-250°C and the hydrothermal reaction time is 8-16 hours.
6. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, In step (2), the volume ratio of alcohol to water is 1:1.5 to 9.
7. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, In step (2), the phenolic compounds include any one of phenol, resorcinol, and cresol; Aldehydes include any one of formaldehyde, acetaldehyde, or furfural; The dispersant includes any one of hexadecyltrimethylammonium bromide, sodium sulfonated hydroxymethylpropane sulfonate, and sodium alkylbenzene sulfonate; the catalyst is any one or more of ammonia, sulfuric acid, sodium hydroxide, and hydrochloric acid.
8. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, In step (2), the order of addition of phenolic compounds, aldehyde compounds, dispersants and catalysts is phenolic compounds, dispersants, catalysts and aldehyde compounds, respectively; before adding aldehyde compounds, they need to be stirred and ultrasonically dispersed for 0.5 to 2 hours; the phenol-aldehyde polymerization reaction time is 8 to 15 hours.
9. The high-concentration anti-site defect lithium manganese iron phosphate material according to claim 1, characterized in that, In step (2), the inert atmosphere during the roasting process is generated by argon or nitrogen; the roasting temperature is 650-750℃; and the roasting time is 8-15h.