Method for regulating and controlling highly exposed {010} crystal face of manganese-rich phosphate-based positive electrode material
By using a solid-state synthesis route and inducing the growth of lithium manganese iron phosphate crystals along the {010} crystal plane using sulfate additives, the problems of complex equipment, high cost, and high pollution in existing technologies have been solved, and the industrial production and performance improvement of materials with high exposure {010} crystal planes have been realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LANZHOU UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2026-01-16
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods for preparing high-exposure {010} crystal-faceted lithium manganese iron phosphate materials suffer from problems such as complex equipment, high cost, significant pollution, and difficulty in industrialization.
A solid-state synthesis route was adopted, and by introducing sulfate additives, LiMnFePO4 crystals were induced to grow along the {010} crystal plane during the high-temperature sintering and lithiation process of the material, thus preparing a lithium iron manganese phosphate cathode material with high exposure of the {010} crystal plane.
It significantly improves the diffusion path of lithium ions in the bulk phase, enhances the high-rate electrochemical performance of the material, and features a simple, environmentally friendly, and low-cost process suitable for industrial production.
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Figure CN122010076A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery cathode material preparation technology, specifically a method for controlling the high exposure of {010} crystal planes in manganese-rich phosphate-based cathode materials. Background Technology
[0002] Olivine-type phosphate-based cathode materials, especially lithium manganese iron phosphate (LiMnFePO4, or LMFP), are considered ideal cathode materials for next-generation high-energy-density lithium-ion batteries due to their high theoretical specific capacity (approximately 170 mAh / g), good structural stability, high safety, low cost, and environmental friendliness. However, two inherent defects in LiMnFePO4 materials severely limit their electrochemical performance, especially in high-rate applications: one is its extremely low electronic conductivity (approximately 10⁻⁻¹). 9 ~10⁻¹ 0 The first factor is that lithium ions diffuse primarily along the b-axis in the crystal structure, resulting in slow diffusion kinetics. These two factors combined contribute to the material's poor rate performance.
[0003] Currently, the main strategies for improving the rate performance of LiMnFePO4 materials include: Carbon coating: Coating the material surface with a conductive carbon layer to improve electronic conductivity. However, an excessively thick carbon layer will reduce the material's tap density and volumetric energy density, and since carbon itself does not contribute to capacity, it may lead to a decrease in overall specific capacity (refer to patent CN119349534A). Nanoparticle size reduction: Reducing the material particle size to the nanoscale shortens the lithium-ion diffusion path. However, this leads to a decrease in the material's tap density, deterioration of electrode processing performance, and easy agglomeration of nanoparticles (refer to patent CN118289728A). Ion doping: Introducing heterovalent cations into the crystal lattice may improve intrinsic conductivity. However, doping may introduce an electrochemically inert phase, reducing the content of active material, and excessive doping may even block lithium-ion diffusion channels (refer to patent CN119503892A). Crystal facet manipulation: By controlling crystal growth, more specific crystal faces that are conducive to rapid lithium-ion transport are exposed. Among them, the {010} crystal plane is the main channel surface for lithium ion diffusion along the b-axis in LiMnFePO4. The highly exposed {010} crystal plane can effectively shorten the diffusion distance of lithium ions in the bulk phase, thereby significantly improving the rate performance.
[0004] Currently, the mainstream methods for achieving {010} crystal facet control are solvothermal or hydrothermal methods. These methods typically utilize organic molecules such as alcohols and surfactants as morphology inducers under high temperature and pressure to control crystal growth along specific directions. For example, patent CN116873893A discloses a method for preparing lithium manganese iron phosphate with highly exposed {010} crystal faces, but this method is a typical liquid-phase method. The solvothermal method has the following significant drawbacks: expensive and demanding reaction equipment; the use of large amounts of organic solvents, posing safety and environmental risks; the need for solvent recycling, increasing process complexity and cost; and difficulty in achieving continuous, large-scale production, limiting its industrial application prospects.
[0005] Therefore, developing a simple, low-cost, environmentally friendly, and easily scalable method for preparing high-exposed {010} crystal-plane LiMnFePO4 materials is of great significance for promoting the practical application of this material in high-performance lithium-ion batteries. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of existing technologies that use solvothermal methods to prepare lithium manganese iron phosphate materials with high exposure {010} crystal planes, such as complex equipment, high cost, significant pollution, and difficulty in industrialization. This invention provides a method for controlling the high exposure of {010} crystal planes in manganese-rich phosphate-based cathode materials. Based on a solid-state synthesis route, this method introduces sulfate additives to induce the preferential growth of LiMnFePO4 crystals along the {010} crystal plane direction during the high-temperature sintering and lithiation process, thereby preparing olivine-type lithium manganese iron phosphate cathode materials with high exposure of {010} crystal planes. This method is simple, has mild reaction conditions, requires no complex post-treatment, and does not generate harmful waste liquid, making it highly promising for industrial application.
[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for controlling the high exposure of {010} crystal planes in manganese-rich phosphate-based cathode materials, such as... Figure 1 As shown, it includes the following steps: S1. Weigh out manganese salts (MnO2, MnC2O4·2H2O, MnCO3, Mn(H2PO4)2, MnC4H6O4·4H2O, etc.), iron salts (FeSO4·7H2O, Fe2O3, FePO4, etc.), lithium salts (LiOH, Li2CO3, CH3COOLi, LiH2PO4, etc.), phosphates (NH4H2PO4), and sulfates (MgSO4, NaSO4, FeSO4·7H2O, etc.) according to the molar ratio of (1-n):n:1:1:0.01, (n=0.4,0.5,0.6,0.7), then add 10~50% (mass fraction) of organic carbon (glucose, sucrose, citric acid, etc.), ball mill them in anhydrous ethanol medium, and dry them at 80~110℃ to obtain the precursor; S2. Place the precursor in a tube furnace and pre-sinter it at 300°C in an argon atmosphere for 2-5 hours, then anneal it naturally. S3. The temperature is then raised to 700℃ and sintered in an argon atmosphere for 6-10 hours, followed by natural annealing to obtain lithium manganese iron phosphate cathode material with highly exposed {010} crystal planes.
[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) To address the problem of slow one-dimensional diffusion of lithium ions along the b-axis and insufficient rate performance in lithium manganese iron phosphate (LiMnFePO4) materials due to crystal structure limitations, this invention induces preferential growth of crystals along the {010} crystal plane during solid-phase synthesis by sulfate ions, significantly increasing the exposure ratio of this crystal plane. Since the {010} crystal plane is the main channel surface for lithium ion diffusion along the b-axis, its high exposure effectively shortens the diffusion path of lithium ions in the bulk phase, thereby fundamentally improving the ion transport kinetics of the material and enhancing its electrochemical performance at high rates.
[0009] (2) Compared with the liquid phase crystal surface control methods such as solvothermal and hydrothermal methods commonly used in the prior art, the present invention adopts a completely solid phase synthesis route. This method does not require the use of large amounts of organic solvents or surfactants, thus avoiding the generation of waste liquid and subsequent treatment problems from the source, and the process is more green and environmentally friendly. At the same time, the solid phase method has low equipment requirements, simple process flow, and significantly reduced energy consumption and cost, which is more in line with the requirements of large-scale industrial production for economy, safety and operability.
[0010] (3) Compared with other strategies for improving the performance of lithium manganese iron phosphate, the crystal plane control method of the present invention has unique advantages: compared with carbon coating, it improves conductivity without sacrificing the intrinsic specific capacity of the material; compared with nano-sizing, it optimizes ion diffusion while maintaining a suitable particle size and compaction density; compared with element doping, it improves performance by controlling the crystal growth habit rather than changing the lattice composition, avoiding the risk of introducing impurity phases or blocking lithium ion channels. The present invention provides a more direct, efficient and less side-effect-prone performance optimization approach.
[0011] (4) The significant effects of the present invention have been confirmed by data from specific embodiments: the high-exposure {010} crystal plane material LiMn prepared by the method of the present invention 0.6 Fe 0.4 After 300 cycles at a high rate of 5C, PO4 maintained a discharge capacity retention rate of 95.7%, far exceeding the 50.4% of the unmodified control sample. This not only demonstrates the remarkable effectiveness of this method in improving the cycling stability of materials, but also reflects its comprehensive advantages in enhancing discharge capacity and rate performance, providing a reliable solution for preparing high-performance lithium manganese iron phosphate cathode materials. Attached Figure Description
[0012] Figure 1 This is a flowchart of the present invention; Figure 2 LiMn in this invention 0.6 Fe 0.4 PO4{010} and LiMn 0.6 Fe 0.4 XRD pattern of PO4; Figure 3 LiMn in this invention 0.6 Fe 0.4 PO4{010}(a) and LiMn 0.6 Fe 0.4 SEM image of PO4(b); Figure 4 LiMn in this invention 0.6 Fe 0.4 PO4{010} and LiMn 0.6 Fe 0.4 Long cycle graph at PO4 5C. Detailed Implementation
[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0014] Example 1
[0015] A method for controlling the high exposure of {010} crystal planes in lithium manganese iron phosphate cathode materials includes the following steps: (1) Weigh manganese salt, iron salt, lithium salt, phosphate and sulfate according to the molar ratio of (1-n):n:1:1:0.01, (n=0.4), and add 10~50% (mass fraction) of organic carbon. Ball mill them in anhydrous ethanol medium and dry them at 80~110℃ to obtain the precursor.
[0016] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0017] (3) The temperature was raised to 700℃ and sintered in an argon atmosphere for 6-10 hours, followed by natural annealing to obtain a cathode material LiMn with highly exposed {010} crystal planes. 0.6 Fe 0.4 PO4.
[0018] Example 2
[0019] A method for controlling the high exposure of {010} crystal planes in lithium manganese iron phosphate cathode materials includes the following steps: (1) Weigh manganese salt, iron salt, lithium salt, phosphate and sulfate according to the molar ratio of (1-n):n:1:1:0.01, (n=0.5), and add 10~50% (mass fraction) of organic carbon. Ball mill them in anhydrous ethanol medium and dry them at 80~110℃ to obtain the precursor.
[0020] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0021] (3) The temperature was raised to 700℃ and sintered in an argon atmosphere for 6-10 hours, followed by natural annealing to obtain LiMn with highly exposed {010} crystal planes. 0.5 Fe 0.5 PO4.
[0022] Example 3
[0023] A method for controlling the high exposure of {010} crystal planes in lithium manganese iron phosphate cathode materials includes the following steps: Manganese salt, iron salt, lithium salt, phosphate, and sulfate were weighed according to the molar ratio of (1-n):n:1:1:0.01 (n=0.6), and 10-50% (mass fraction) of organic carbon was added. They were ball-milled in anhydrous ethanol medium and dried at 80-110℃ to obtain the precursor.
[0024] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0025] (3) The temperature was raised to 700℃ and sintered in an argon atmosphere for 6-10 hours, followed by natural annealing to obtain LiMn with highly exposed {010} crystal planes. 0.4 Fe 0.6 PO4.
[0026] Example 4
[0027] A method for controlling the high exposure of {010} crystal planes in lithium manganese iron phosphate cathode materials includes the following steps: (1) Weigh manganese salt, iron salt, lithium salt, phosphate and sulfate according to the molar ratio of (1-n):n:1:1:0.01, (n=0.7), and add 10~50% (mass fraction) of organic carbon. Ball mill them in anhydrous ethanol medium and dry them at 80~110℃ to obtain the precursor.
[0028] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0029] (3) The temperature was raised to 700℃ and sintered in an argon atmosphere for 6-10 hours, followed by natural annealing to obtain LiMn with highly exposed {010} crystal planes. 0.3 Fe 0.7 PO4.
[0030] Comparative Example 1 The preparation method of lithium manganese iron phosphate cathode material includes the following steps: Manganese salt, iron salt, lithium salt, and phosphate were weighed according to a molar ratio of (1-n):n:1:1 (n=0.4), and 10-50% (mass fraction) of organic carbon was added. They were ball-milled in anhydrous ethanol medium and dried at 80-110℃ to obtain the precursor.
[0031] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0032] (3) After sintering in an argon atmosphere at 700℃ for 6-10 h, LiMn can be obtained by natural annealing. 0.6 Fe0.4 PO4.
[0033] Comparative Example 2 The preparation method of lithium manganese iron phosphate cathode material includes the following steps: Weigh manganese salt, iron salt, lithium salt, and phosphate according to the molar ratio of (1-n):n:1:1 (n=0.5), then add 10~50% (mass fraction) of organic carbon, ball mill them in anhydrous ethanol medium, and dry them at 80~110℃ to obtain the precursor.
[0034] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0035] (3) The temperature is raised to 700℃, and after sintering in an argon atmosphere for 6-10 hours, natural annealing is performed to obtain LiMn. 0.5 Fe 0.5 PO4.
[0036] Comparative Example 3 The preparation method of lithium manganese iron phosphate cathode material includes the following steps: (1) Weigh manganese salt, iron salt, lithium salt and phosphate according to the molar ratio of (1-n):n:1:1, (n=0.6), add 10~50% (mass fraction) of organic carbon, ball mill them in anhydrous ethanol medium, and dry them at 80~110℃ to obtain the precursor.
[0037] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0038] (3) The temperature is raised to 700℃, and after sintering in an argon atmosphere for 6-10 hours, natural annealing is performed to obtain LiMn. 0.4 Fe 0.6 PO4.
[0039] Comparative Example 4 The preparation method of lithium manganese iron phosphate cathode material includes the following steps: (1) Weigh manganese salt, iron salt, lithium salt and phosphate according to the molar ratio of (1-n):n:1:1, (n=0.7), add 10~50% (mass fraction) of organic carbon, ball mill them in anhydrous ethanol medium, and dry them at 80~110℃ to obtain the precursor.
[0040] (2) Place the precursor into a tube furnace and pre-sinter it in an argon atmosphere at 300°C for 2-5 hours, then anneal it naturally.
[0041] (3) The temperature is raised to 700℃, and after sintering in an argon atmosphere for 6-10 hours, natural annealing is performed to obtain LiMn.0.3 Fe 0.7 PO4.
[0042] like Figure 2 As shown, XRD tests were performed on LMFP{010} and LMFP. The intensity ratios of I(020) / I(200) of LMFP{010} and LMFP reached 2.2 and 1.9, respectively, which means that LMFP{010} has a highly exposed {010} crystal plane; and the cathode material has characteristic peaks of typical olivine structure. The fine and narrow characteristic peaks indicate that the material has good crystallinity.
[0043] like Figure 3 As shown, SEM tests were performed on LMFP{010} and LMFP, and it can be seen that LMFP{010} has a more uniform particle size.
[0044] like Figure 4 As shown, for LiMn 0.6 Fe 0.4 PO4{010} and LiMn 0.6 Fe 0.4 Electrochemical performance tests were conducted on the PO4 cathode material at 25℃ and a 5C rate, showing the performance of LiMn. 0.6 Fe 0.4 The initial discharge specific capacity of PO4{010} is 127.1 mAh g. -1 After 300 cycles, the discharge specific capacity is 121.7 mAh g. -1 The capacity retention rate was 95.7%; at 25℃ and 5C, LiMn 0.6 Fe 0.4 The first discharge specific capacity of PO4 is 83.1 mAh g. -1 After 300 cycles, the discharge specific capacity is 41.9 mAh g. -1 The capacity retention rate was 50.4%. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.
Claims
1. A method for controlling the high exposure of {010} crystal planes in a manganese-rich phosphate-based cathode material, characterized in that, Includes the following steps: S1. Precursor preparation: Weigh the raw materials according to the molar ratio of manganese salt, iron salt, lithium salt, phosphate and sulfate in the form of (1-n): n: 1: 1:0.01, where n is in the range of 0.4, 0.5, 0.6 or 0.7; add 10% to 50% of the total mass of the raw materials with an organic carbon source; mix the weighed raw materials and organic carbon source in anhydrous ethanol medium and ball mill them, then dry them at a temperature of 80°C to 110°C to obtain the precursor; S2. Pre-sintering: The precursor is pre-sintered in an argon atmosphere at 300°C for 2 to 5 hours, followed by natural cooling. S3. High-temperature sintering and crystallization: The pre-sintered and cooled material is heated to 700°C in an argon atmosphere for sintering, and the holding time is 6 to 10 hours. Then it is naturally cooled to obtain lithium manganese iron phosphate cathode material with high exposure of {010} crystal plane.
2. The method according to claim 1, characterized in that, The manganese salt is selected from at least one of MnO2, MnC2O4·2H2O, MnCO3, Mn(H2PO4)2 and MnC4H6O4·4H2O.
3. The method according to claim 1, characterized in that, The iron salt is selected from at least one of FeSO4·7H2O, Fe2O3 and FePO4.
4. The method according to claim 1, characterized in that, The lithium salt is selected from at least one of LiOH, Li2CO3, CH2COOLi and LiH2PO4.
5. The method according to claim 1, characterized in that, The phosphate is NH4H2PO4.
6. The method according to claim 1, characterized in that, The sulfate is selected from at least one of MgSO4, Na2SO4 and FeSO4·7H2O.
7. The method according to claim 1, characterized in that, The organic carbon source is selected from at least one of glucose, sucrose, and citric acid.
8. The lithium manganese iron phosphate cathode material prepared by the method according to any one of claims 1-7, characterized in that, The cathode material has a highly exposed {010} crystal plane, and the ratio of the diffraction peak intensity of the (020) crystal plane to that of the (200) crystal plane in its X-ray diffraction pattern is 2.2, which is greater than the peak intensity ratio of the unmodified control sample.
9. A lithium-ion battery positive electrode, characterized in that, It includes the lithium manganese iron phosphate cathode material as described in claim 8.
10. A lithium-ion battery, characterized in that, It includes the positive electrode as described in claim 9.