Diameter-controllable one-dimensional lithium manganate nanorods, preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion battery electrode materials, and specifically discloses a one-dimensional lithium manganate nanorod with controllable diameter and a preparation method and application thereof. The application disperses manganese sulfate, potassium permanganate, a structure directing agent and a surfactant into a solvent, carries out a hydrothermal reaction, and obtains black precipitate; then the black precipitate is sintered to obtain manganese dioxide nanorods; the manganese dioxide nanorods are mixed with lithium hydroxide, and two-stage sintering is carried out to obtain one-dimensional lithium manganate nanorods. The one-dimensional lithium manganate nanorods are uniform in thickness and have very small surface energy, when used as a positive electrode material, can effectively shorten the transmission path of lithium ions, are not prone to agglomeration and have good flexibility, can maintain the integrity of the structure during long-time service under a large current, and are beneficial to improving the rate and cycle performance of the electrode. In addition, by adjusting the concentration of potassium permanganate and the hydrothermal reaction temperature, the diameter of the manganese dioxide can be accurately adjusted, and the controllable preparation of the one-dimensional lithium manganate can be realized.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrode materials technology, and in particular to a one-dimensional lithium manganese oxide nanorod with controllable diameter, its preparation method and application. Background Technology

[0002] Lithium-ion batteries are not only important electrochemical energy storage devices, but are also widely used in electric vehicles, hybrid vehicles, energy storage facilities, and consumer electronics components. Among them, spinel-type LiMn2O4 cathode materials have broad application prospects as an alternative to commercial cobalt-based and nickel-based cathode materials in the fields of 3C electronic products and low-speed electric vehicle batteries due to their relatively stable charge-discharge platform, excellent thermal stability, low production cost, and environmental friendliness.

[0003] However, commercially available spinel-type LiMn2O4 cathode materials are all composed of micron-sized or larger aggregates, resulting in long lithium-ion diffusion and electron transport paths during charging and discharging, which limits their further commercial application. Compared to micron-sized materials, one-dimensional spinel LiMn2O4 materials (such as nanowires, nanorods, and nanotubes) can effectively shorten the LiMn2O4 cathode material path. + The material exhibits excellent diffusion and electron transport distances, along with resistance to aggregation and good flexibility, allowing it to maintain structural integrity during long-term operation under high current. This results in superior electrochemical performance and promising application prospects. However, traditional fabrication methods struggle to precisely control the diameter of one-dimensional materials, making it difficult to meet the specific requirements of batteries.

[0004] Therefore, how to provide a one-dimensional lithium manganese oxide nanorod with controllable diameter, its preparation method, and its application are urgent problems to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a one-dimensional lithium manganese oxide nanorod with controllable diameter, its preparation method and application, which solves the problems of difficulty in controlling the size of one-dimensional lithium manganese oxide and uneven size in traditional methods.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing one-dimensional lithium manganese oxide nanorods with controllable diameter includes the following steps:

[0008] 1) Manganese sulfate, potassium permanganate, structure-directing agent and surfactant are dispersed in a solvent and subjected to a hydrothermal reaction to obtain a black precipitate;

[0009] 2) The black precipitate was sintered to obtain manganese dioxide nanorods;

[0010] 3) Manganese dioxide nanorods were mixed with lithium hydroxide and sintered in two stages to obtain one-dimensional lithium manganate nanorods.

[0011] In the hydrothermal reaction system described in step 1), the molar concentration of potassium permanganate is 0.06–0.15 mmol / L, and the hydrothermal reaction temperature is 120–160 °C.

[0012] The structure-directing agent includes polyethylene glycol.

[0013] Preferably, the molar ratio of manganese sulfate to potassium permanganate is 1:0.5 to 2;

[0014] The molar volume ratio of potassium permanganate to the structure-directing agent and surfactant is 0.06–0.15 mmol: 5–10 mL: 5–10 mL.

[0015] Preferably, the surfactant includes one or more of ethanol, isopropanol, isobutanol, and n-pentanol;

[0016] The solvent is water.

[0017] Preferably, the hydrothermal reaction time in step 1) is 8 to 12 hours.

[0018] Preferably, the sintering temperature in step 2) is 400-500°C and the sintering time is 2-4 hours.

[0019] Preferably, the molar ratio of manganese dioxide nanorods to lithium hydroxide in step 3) is 2:1 to 1.05.

[0020] Preferably, the two-stage sintering includes a first sintering and a second sintering;

[0021] The temperature for the first sintering is 400–500℃, and the sintering time is 4–6 hours.

[0022] The second sintering temperature is 650-750℃, and the sintering time is 10-12 hours.

[0023] Another object of the present invention is to provide a one-dimensional lithium manganese oxide nanorod prepared by the preparation method described above, wherein the one-dimensional lithium manganese oxide nanorod has a diameter of 30-500 nm and a length of 2-6 μm.

[0024] Another object of the present invention is to provide an application of one-dimensional lithium manganese oxide nanorods as a cathode material.

[0025] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The one-dimensional lithium manganese oxide nanorods prepared by this invention have uniform thickness and very low surface energy. Different concentrations of manganese salts first form [MnO] under hydrothermal conditions. x The structural unit, under the hydrothermal reaction temperature and the action of the structural guiding agent defined in this invention, produces stable directional curling, which can yield manganese dioxide with a uniform cross-sectional diameter.

[0027] 2. By adjusting the concentration of potassium permanganate and the hydrothermal reaction temperature, the interface diameter of manganese dioxide can be accurately adjusted, enabling the controllable preparation of one-dimensional lithium manganese oxide.

[0028] 3. The one-dimensional lithium manganese oxide nanorods prepared by the method of the present invention have a smooth surface and uniform size. When used as a positive electrode material, they can effectively shorten the lithium ion transport path, are not prone to agglomeration and have good flexibility. They can maintain the integrity of their structure during long-term service at high current, which is beneficial to improving the rate capability and cycle performance of the electrode.

[0029] 4. The LiMn2O4 cathode material prepared using the method described in this invention exhibits minimal capacity decay after 100 cycles at room temperature under 3.0V–4.3V and 1C charge-discharge conditions, and retains over 90% of its capacity after 100 cycles at 55℃. This invention requires minimal synthesis equipment, is simple to operate, has no special requirements for the sintering process, and is environmentally friendly. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0031] Figure 1 The XRD patterns of one-dimensional lithium manganese oxide nanorods prepared in Examples 1-4 of this invention;

[0032] Figure 2 The images show the SEM images of one-dimensional lithium manganese oxide nanorods prepared in Examples 1-4 of this invention. Figure 2 Image (a) is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 1. Figure 2 Image (b) is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 2. Figure 2 Image (c) in the image is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 3. Figure 2 (d) is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 4;

[0033] Figure 3Electrochemical performance curves of batteries assembled from one-dimensional lithium manganese oxide nanorods prepared in Examples 1-4 of this invention under different rate cycles. Detailed Implementation

[0034] This invention provides a method for preparing one-dimensional lithium manganese oxide nanorods with controllable diameter, comprising the following steps:

[0035] 1) Manganese sulfate, potassium permanganate, structure-directing agent and surfactant are dispersed in a solvent and subjected to a hydrothermal reaction to obtain a black precipitate;

[0036] 2) The black precipitate was sintered to obtain manganese dioxide nanorods;

[0037] 3) Manganese dioxide nanorods were mixed with lithium hydroxide and sintered in two stages to obtain one-dimensional lithium manganate nanorods.

[0038] In this invention, in the hydrothermal reaction system described in step 1), the molar concentration of potassium permanganate is 0.06–0.15 mmol / L, specifically 0.08 mmol / L, 0.1 mmol / L, 0.11 mmol / L, 0.12 mmol / L, 0.13 mmol / L, or 0.14 mmol / L; the hydrothermal reaction temperature is 120–160°C, specifically 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, or 155°C.

[0039] In this invention, the diameter of the one-dimensional lithium manganese oxide nanorods increases with increasing hydrothermal reaction temperature and with increasing potassium permanganate concentration. The diameters of the one-dimensional lithium manganese oxide nanorods under different hydrothermal reaction temperatures and potassium permanganate concentrations are shown in Table 1.

[0040] Table 1. Diameter of one-dimensional lithium manganese oxide nanorods at different temperatures and concentrations.

[0041]

[0042] In this invention, the structure-directing agent comprises polyethylene glycol.

[0043] In this invention, the molar ratio of manganese sulfate to potassium permanganate is 1:0.5 to 2, preferably 1:0.8 to 1.5, and more preferably 1:1.

[0044] In this invention, the molar volume ratio of potassium permanganate to structure directing agent and surfactant is 0.06-0.15 mmol: 5-10 mL: 5-10 mL, preferably 0.1-0.14 mmol: 6-9 mL: 6-9 mL, and more preferably 0.12 mmol: 8 mL: 8 mL.

[0045] In this invention, the surfactant includes one or more of ethanol, isopropanol, isobutanol and n-pentanol; the solvent is water.

[0046] In this invention, the hydrothermal reaction time in step 1) is 8 to 12 hours, specifically 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours.

[0047] In this invention, the black precipitate is further subjected to sequential washing, filtration and freeze-drying steps before sintering.

[0048] In this invention, the sintering temperature in step 2) is 400-500℃, specifically 420℃, 440℃, 450℃, 460℃, or 480℃; the sintering time is 2-4h, specifically 2.2h, 2.5h, 2.8h, 3h, 3.2h, 3.5h, or 3.8h.

[0049] In this invention, the molar ratio of manganese dioxide nanorods to lithium hydroxide in step 3) is 2:1 to 1.05, preferably 2:1.01 to 1.04, and more preferably 2:1.02.

[0050] In this invention, the two-stage sintering includes a first sintering and a second sintering.

[0051] In this invention, the temperature of the first sintering is 400-500℃, specifically 420℃, 440℃, 450℃, 460℃, or 480℃; the sintering time is 4-6 hours, specifically 4.2 hours, 4.5 hours, 4.8 hours, 5 hours, 5.2 hours, 5.5 hours, or 5.8 hours; the temperature of the second sintering is 650-750℃, specifically 660℃, 680℃, 700℃, 720℃, or 740℃; the sintering time is 10-12 hours, specifically 10 hours, 10.5 hours, 11 hours, 11.5 hours, or 12 hours.

[0052] The present invention also provides a one-dimensional lithium manganese oxide nanorod prepared by the preparation method described above. The diameter of the one-dimensional lithium manganese oxide nanorod is 30-500 nm, specifically 40 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, and 450 nm; the length is 2-6 μm, specifically 2 μm, 3 μm, 4 μm, 5 μm, and 6 μm.

[0053] This invention also provides an application of one-dimensional lithium manganese oxide nanorods as a cathode material.

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Example 1

[0056] Weigh out 0.006 mmol of KMnO4 and 0.008 mmol of MnSO4·H2O according to the molar ratio and add them to a beaker. Then pour 100 mL of water into the beaker, followed by 0.5 mL of polyethylene glycol and 0.5 mL of isopropanol (the molar concentration of KMnO4 is 0.06 mmol / L). Place the beaker on a stirrer and stir until the solids are completely dissolved. Transfer the well-mixed solution to a reaction vessel, tighten the reaction vessel, and place it in a forced-air drying oven. Set the temperature to 160℃ and the hydrothermal time to 8 h. After the hydrothermal treatment, wash and filter the resulting black precipitate with deionized water and ethanol, respectively. Then, place the sample in a freeze dryer to dry. Place the obtained black powder in a muffle furnace and heat it to 400℃ at a rate of 5℃ / min. Hold it at this temperature for 2 h, and then remove it after cooling with the furnace to obtain manganese dioxide nanorods. The obtained manganese dioxide nanorods were thoroughly mixed with lithium hydroxide at a molar ratio of 2:1.05 and then sintered in a muffle furnace in two stages at 5 °C / min. First, the sintering temperature was increased to 450 °C for 4 h, and then the sintering temperature was increased to 750 °C for 12 h. After cooling in the furnace, the nanorods were removed to obtain one-dimensional lithium manganese oxide nanorods, denoted as LMO-1.

[0057] Example 2

[0058] Weigh out 0.009 mmol of KMnO4 and 0.008 mmol of MnSO4·H2O according to the molar ratio and add them to a beaker. Then pour 100 mL of water into the beaker, followed by 0.5 mL of polyethylene glycol and 0.5 mL of isopropanol (the molar concentration of KMnO4 is 0.09 mmol / L). Place the beaker on a stirrer and stir until the solids are completely dissolved. Transfer the well-mixed solution to a reaction vessel, tighten the reaction vessel, and place it in a forced-air drying oven. Set the temperature to 160℃ and the hydrothermal time to 8 h. After the hydrothermal treatment, wash and filter the resulting black precipitate with deionized water and ethanol, respectively. Then, place the sample in a freeze dryer for drying. Place the obtained black powder in a muffle furnace and heat it to 400℃ at a rate of 2℃ / min. Hold it at this temperature for 2 h, and then remove it after cooling with the furnace to obtain manganese dioxide nanorods. The obtained manganese dioxide nanorods were thoroughly mixed with lithium hydroxide at a molar ratio of 2:1.05 and then sintered in a muffle furnace in two stages at 5 °C / min. First, the sintering temperature was increased to 400 °C for 5 h, and then the sintering temperature was increased to 700 °C for 10 h. After cooling in the furnace, the nanorods were removed to obtain one-dimensional lithium manganese oxide nanorods, denoted as LMO-2.

[0059] Example 3

[0060] Weigh out 0.012 mmol of KMnO4 and 0.008 mmol of MnSO4·H2O according to the molar ratio and add them to a beaker. Then pour 100 mL of water into the beaker, followed by 0.5 mL of polyethylene glycol and 0.5 mL of isopropanol (the molar concentration of KMnO4 is 0.12 mmol / L). Place the beaker on a stirrer and stir until the solids are completely dissolved. Transfer the well-mixed solution to a reaction vessel, tighten the reaction vessel, and place it in a forced-air drying oven. Set the temperature to 120℃ and the hydrothermal time to 12 h. After the hydrothermal treatment, wash and filter the resulting black precipitate with deionized water and ethanol, respectively. Then, place the sample in a freeze dryer for drying. Place the obtained black powder in a muffle furnace and heat it to 450℃ at a rate of 4℃ / min. Hold it at this temperature for 2 h, and then remove it after cooling with the furnace to obtain manganese dioxide nanorods. The obtained manganese dioxide nanorods were thoroughly mixed with lithium hydroxide at a molar ratio of 2:1.05 and then sintered in a muffle furnace in two stages at 4 °C / min. First, the sintering temperature was increased to 500 °C for 6 h, and then the sintering temperature was increased to 650 °C for 12 h. After cooling in the furnace, the nanorods were removed to obtain one-dimensional lithium manganese oxide nanorods, denoted as LMO-3.

[0061] Example 4

[0062] Weigh out 0.015 mmol of KMnO4 and 0.008 mmol of MnSO4·H2O according to the molar ratio and add them to a beaker. Then pour 100 mL of water into the beaker, followed by 0.5 mL of polyethylene glycol and 0.5 mL of isopropanol (the molar concentration of KMnO4 is 0.15 mmol / L). Place the beaker on a stirrer and stir until the solids are completely dissolved. Transfer the well-mixed solution to a reaction vessel, tighten the reaction vessel, and place it in a forced-air drying oven. Set the temperature to 140℃ and the hydrothermal time to 10 h. After the hydrothermal treatment, wash and filter the resulting black precipitate with deionized water and ethanol, respectively. Then, place the sample in a freeze dryer for drying. Place the obtained black powder in a muffle furnace and heat it to 500℃ at a rate of 3℃ / min. Hold it at this temperature for 3 h, and then remove it after cooling with the furnace to obtain manganese dioxide nanorods. The obtained manganese dioxide nanorods were thoroughly mixed with lithium hydroxide at a molar ratio of 2:1.05 and then sintered in a muffle furnace in two stages at 3 °C / min. First, the sintering temperature was increased to 400 °C for 6 h, and then the sintering temperature was increased to 700 °C for 10 h. After cooling in the furnace, the nanorods were removed to obtain one-dimensional lithium manganese oxide nanorods, denoted as LMO-4.

[0063] The XRD patterns of the one-dimensional lithium manganese oxide nanorods prepared in Examples 1-4 are shown below. Figure 1 As shown, through Figure 1 It can be seen that the diffraction peaks of all cathode materials correspond to LiMn2O4 (standard card number: PDF#35.0782) and have the Fd3m space group, indicating that the sample is high-purity LiMn2O4.

[0064] SEM image as follows Figure 2 As shown, where, Figure 2 Image (a) is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 1. Figure 2 Image (b) is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 2. Figure 2 Image (c) in the image is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 3. Figure 2 Image (d) in the image is a SEM image of the one-dimensional lithium manganese oxide nanorods prepared in Example 4. Figure 2 It can be seen that all samples exhibit typical one-dimensional nanorod morphology. The average diameters of the samples prepared in Examples 1-4 are approximately 30-60 nm, 60-100 nm, 100-140 nm, and 140-180 nm, respectively. They are uniform in diameter, have smooth surfaces, and an aspect ratio greater than 20:1.

[0065] The one-dimensional lithium manganese oxide nanorods prepared in Examples 1-4 were used as positive electrode materials for battery assembly. The assembly method was as follows: a 2025-type button cell was used as the battery performance testing carrier; LiMn2O4 coated on an aluminum foil disc was used as the positive electrode; a lithium metal sheet was used as the negative electrode; and 1 mol / L LiPF6 (dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1) was used as the electrolyte. The button cell was assembled in an argon-filled glove box in the following order: negative electrode shell, gasket, lithium sheet, separator, positive electrode sheet, gasket, spring sheet, and positive electrode shell. The assembly was then compacted and sealed using a hydraulic button cell packaging machine to obtain the 2025-type button cell. The testing method was as follows: The battery performance was tested using a Xinwei CT3008 battery tester. The test voltage range was 3.0–4.5V. The charge and discharge currents were set according to different test requirements. During the current setting process, the current density corresponding to the 1C rate of LiMn2O4 was 148 mAh·g. -1 When testing rate performance, the circuit was cycled five times each at current densities of 0.1C, 1C, 2C, 5C, 10C, 20C, and 0.1C. The test results are as follows: Figure 3 As shown, through Figure 3 It can be seen that different one-dimensional lithium manganese oxide nanorods all exhibit good rate performance and cycle stability at high current densities. Among them, the LMO-2 sample still has a discharge capacity of up to 62 mAh·g even at a high current density of 20C. -1 .

[0066] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0067] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a one-dimensional LiMnO3 nanorod with controllable diameter, characterized in that, The method comprises the following steps: 1) dispersing manganese sulfate, potassium permanganate, a structure directing agent and a surfactant into a solvent, performing a hydrothermal reaction to obtain a black precipitate; 2) sintering the black precipitate to obtain manganese dioxide nanorods; 3) mixing the manganese dioxide nanorods with lithium hydroxide, and performing two-stage sintering to obtain one-dimensional lithium manganate nanorods; In the hydrothermal reaction system in step 1), the molar concentration of potassium permanganate is 0.06-0.15 mmol / L, and the temperature of the hydrothermal reaction is 120-160 ℃; The structure directing agent comprises polyethylene glycol; The surfactant comprises one or more of ethanol, isopropyl alcohol, isobutyl alcohol and n-pentyl alcohol; The two-stage sintering comprises first-stage sintering and second-stage sintering; The temperature of the first-stage sintering is 400-500 ℃, and the sintering time is 4-6 h; The temperature of the second-stage sintering is 650-750 ℃, and the sintering time is 10-12 h.

2. The method for preparing a one-dimensional lithium manganese oxide nanorod with controllable diameter according to claim 1, characterized in that, The molar ratio of the manganese sulfate to the potassium permanganate is 1:0.5-2; The molar volume ratio of the potassium permanganate to the structure directing agent and the surfactant is 0.06-0.15 mmol:5-10 mL:5-10 mL.

3. The method for preparing a one-dimensional lithium manganese oxide nanorod with controllable diameter according to claim 2, characterized in that, The solvent is water.

4. The method of claim 1-3, wherein the method is characterized by, The time of the hydrothermal reaction in step 1) is 8-12 h.

5. The method for preparing a one-dimensional lithium manganese oxide nanorod with controllable diameter according to claim 4, characterized in that, The sintering temperature in step 2) is 400-500 ℃, and the sintering time is 2-4 h.

6. The method for preparing a one-dimensional lithium manganese oxide nanorod with controllable diameter according to claim 5, characterized in that, In step 3), the molar ratio of the manganese dioxide nanorods to lithium hydroxide is 2:1-1.

05.

7. The one-dimensional lithium manganate nanorods prepared by the method of any one of claims 1 to 6, characterized in that, The diameter of the one-dimensional lithium manganate nanorods is 30-500 nm, and the length is 2-6 μm.

8. Application of the one-dimensional lithium manganate nanorods in claim 7 as a positive electrode material.

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