A rare earth nanoparticle-loaded biosilica negative electrode material and its preparation and application

Abstract

The present invention discloses a rare earth nanoparticle-loaded biosilica anode material, its preparation, and application. The preparation method comprises cultivating diatoms using at least one of LaCl3 and YCl3 as an additive to a diatom growth medium. After the cultivation period, the algae liquid is collected and the cultured diatoms are subjected to simple impurity removal, washing, and calcination to obtain a rare earth nanoparticle-loaded biosilica anode material. This composite material is then prepared as an active anode material for lithium-ion batteries, exhibiting excellent electrochemical performance. The method is simple, easy to implement, environmentally friendly, and highly efficient, and is of great significance to the development of lithium-ion battery anode materials and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of rare earth application and lithium ion battery negative electrode materials, and specifically relates to a rare earth nanoparticle-loaded bio-silica negative electrode material and its preparation and application. Background Art

[0002] Traditional graphite anode materials for lithium-ion batteries have difficulty meeting the needs of the current energy market due to their low theoretical specific capacity. Therefore, there is an urgent need to develop new and more efficient alternative anode materials. As a result, many alternative anode materials have emerged, such as alloy compounds, silicon, silicon dioxide, and transition metal oxides. Among these alternative anode materials, silicon dioxide has become a highly promising lithium-ion battery anode material due to its high theoretical specific capacity, abundance, and extremely abundant reserves on Earth. However, due to its low conductivity and certain volume expansion, large-scale commercial application has not yet been achieved. Among the many sources of silicon dioxide, diatoms are a natural, green, and abundant source of silicon dioxide.

[0003] Since diatoms were reported to be a source of active negative electrode materials for lithium-ion batteries, they have attracted great attention. This is because diatoms have a hollow and porous silica shell structure. Compared with general silica sources, diatom biosilica significantly alleviates the volume expansion of silica during the cycle, which has a significant effect on improving the performance of silica negative electrode materials. Therefore, most research focuses on the in vitro modification of diatom-based biosilica to improve the conductivity of silica. Common modification methods include combining diatom-based biosilica with conductive carbon precursors or metal ions to improve the intrinsic conductivity of silica negative electrode materials. However, most in vitro modification methods have problems such as low efficiency and easy detachment of the loaded conductive phase. In addition, the conductivity of the loaded metal itself will also have a significant impact on the performance of the electrode material. Research on in vivo modification of diatoms to achieve performance improvement of diatom-based biosilica negative electrode materials is still relatively lacking. Therefore, seeking a simpler and more efficient technology for in vivo modification of diatoms to improve silica conductivity is an urgent need in this field.

[0004] Research on rare earth elements (REEs) in the energy storage field has attracted significant attention, particularly in lithium-ion batteries. Notably, most studies have focused on improving the properties of rare earth element-doped cathode materials. For example, Zhang et al. (https: / / doi.org / 10.1007 / s10853-023-08542-z) prepared La- and Y-doped LiFePO4 cathode materials via a one-step hydrothermal method, demonstrating that La and Y can expand the LiFePO4 lattice fringes, improve ion diffusion efficiency, and enhance the material's electronic conductivity, positively impacting the electrochemical performance of the cathode material. However, this method suffers from complex preparation methods, difficulty controlling the content of the doped REE, and the inability to observe a clear distribution of the REEs within the composite material.

[0005] After searching the literature on the prior art, it was found that Chinese patent CN202311770215.7 discloses a modified diatom material, its preparation method, and application. By preparing an ionic rare earth ore extract or wrapping the ionic rare earth ore with a semipermeable membrane to co-cultivate diatoms, a rare earth co-cultivated modified diatom material was obtained. The prepared lithium-ion battery has a capacity of about 820 mAh·g after 35 cycles. -1 The discharge specific capacity of the invention is that the composition of the ionic rare earth ore used is unclear, the rare earth loading is low, and no obvious rare earth nanoparticles are observed on the diatom shell, indicating that the rare earth ore or rare earth ore extract cannot be well utilized during the growth of diatoms. Summary of the Invention

[0006] The present invention aims to combine existing research and exploration to provide a rare earth nanoparticle-loaded biosilica material, its preparation method, and its application, in order to develop a lithium-ion battery negative electrode material with high energy density and long cycle life. The specific technical solution is as follows:

[0007] The present invention is achieved in the following ways:

[0008] A rare earth nanoparticle-loaded biosilica negative electrode material is obtained by utilizing the biomineralization of diatoms to absorb rare earth elements into diatom cells by adding at least one of LaCl3 and YCl3 as an additive to diatom growth medium and processing the rare earth elements into rare earth nanoparticles, which are then calcined under an inert atmosphere.

[0009] The method for preparing the rare earth nanoparticle-loaded bio-silica negative electrode material comprises the following steps:

[0010] 1) Loading diatoms with rare earth nanoparticles: Add rare earth ion solution to diatom culture medium and inoculate diatoms for co-cultivation;

[0011] 2) Diatom collection and pretreatment: After the incubation period, the algae solution is filtered or centrifuged to obtain a diatom precipitate, which is then washed with at least one of hydrochloric acid or sulfuric acid. The acid-washed diatom solution is separated into solid and liquid, and the precipitate is collected and washed with at least one of methanol or ethanol. After solid-liquid separation, the diatom precipitate is collected;

[0012] 3) The diatom precipitate loaded with rare earth nanoparticles is freeze-dried and calcined at high temperature to obtain a rare earth nanoparticle-loaded bio-silica composite material.

[0013] Step 1) preparing a solution of at least one of LaCl3 and YCl3 with a concentration of 0.1 g / L to 1 g / L.

[0014] Step 1) Add 5-20 mL of rare earth compound solution to 1-2 L of diatom culture medium and inoculate 100-200 mL of diatom seed solution.

[0015] Step 1) The diatom culture period is 10 days to 14 days, the culture temperature is 22°C to 25°C, and the light intensity is 2000 Lux to 4000 Lux. The diatom is cultured statically in a light incubator.

[0016] Step 2) Collecting the cultured algal liquid for acid washing; Specifically, the enriched algal liquid is acid washed with 2%-5% dilute hydrochloric acid; After acid washing, the mixture is centrifuged at 8000-10000 rpm for at least 10 minutes to separate the solid and liquid and collect the precipitate; The acid washed precipitate is washed with ethanol 1-2 times until the washing solution is colorless and transparent.

[0017] Step 3) Freeze-dry the diatom pellet at -70°C for at least 24 h.

[0018] Step 3) The dried diatom mixture is heated to 600-900°C at a rate of 5-10°C / min under an argon atmosphere and kept at this temperature for 1-3 hours.

[0019] The preferred heating rate is 5 °C / min, the calcination temperature is 600 °C, and the holding time is 3 h.

[0020] The present invention also provides the use of the rare earth nanoparticle-loaded biosilica in lithium-ion battery negative electrode materials.

[0021] Furthermore, it is used for the preparation of negative electrode materials for lithium-ion batteries.

[0022] The active material prepared in this invention is mixed with Super P and PVDF in a mass ratio of 7:2:1 or 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) is added and ball milled at 300-450 rpm for 1-3 hours to obtain a uniformly mixed electrode slurry. The slurry is then coated onto copper foil at a thickness of 25-300 μm, dried under vacuum at 80°C, and cut to obtain electrode sheets. A preferred ratio of active material: Super P: PVDF is 7:2:1. Ball milling is performed at 300 rpm for 3 hours, and the slurry is coated to a thickness of 50 μm.

[0023] Continue to place the cut electrode sheets on the battery bottom shell in the argon-filled glove box, add 1 to 2 drops of electrolyte on the surface of the electrode sheets, place the diaphragm, add 1 to 2 drops of electrolyte, and finally put in the lithium sheet, cover the battery cover, and seal it on the button battery packaging machine to complete the battery assembly.

[0024] During the drying and calcination process, calcination under argon gas converts the remaining cytoplasm in the diatom cells into a carbon layer to obtain an ideal La / Y / C@SiO2 material. The above method is fast and simple, and can be commercialized by expanding experiments, designing a reasonable process flow, and ultimately achieving marketization.

[0025] The present invention differs from methods disclosed in the prior art in that it uses rare earth chloride as a modifier for diatom culture medium, leveraging the biomineralization process during diatom growth and metabolism to enrich La and Y within the diatom shell structure. This achieves biological self-assembly of rare earth nanoparticles on the diatom shell, unlike traditional methods that involve solid-phase self-assembly of existing diatom raw materials with other substances. This also overcomes the drawback of prior art methods that prevent the effective utilization of rare earth ores or rare earth ore extracts during diatom growth. Furthermore, the entire process is simple and easy to implement, highly safe, economically inexpensive, and uses readily available raw materials, making it eco-friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The XRD patterns of Example 1, Example 2, Example 3, Example 4, Comparative Example 1 and Comparative Example 2 of the present invention are shown.

[0027] Figure 2 These are transmission electron microscopy and scanning electron microscopy images of Comparative Example 1(a), Comparative Example 2(b), Example 2(c), and Example 4(d) of the present invention. In the transmission electron microscopy images of Comparative Example 1 and Comparative Example 2, the surface of the diatom shell is smooth and unloaded. In the transmission electron microscopy and scanning electron microscopy images of Example 2 and Example 4, La and Y nanoparticles distributed on the surface of the diatom shell can be observed.

[0028] Figure 3The results of Example 1, Example 2, Example 3, Example 4, Comparative Example 1 and Comparative Example 2 of the present invention are shown in Figure 1 at 100 mA·g. -1 Long cycle performance curve under different current densities.

[0029] Figure 4 These are the cyclic voltammetry test curves of Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, and Example 4 of the present invention.

[0030] Figure 5 These are the rate performance curves of Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, and Example 4 of the present invention.

[0031] Figure 6 These are the electrochemical impedance spectroscopy test graphs of Comparative Example 1, Comparative Example 2, Example 1, Example 2, Example 3, and Example 4 of the present invention.

[0032] Figure 7 These are soft X-ray nano-CT images of Example 2 of the present invention, where (a) is a 3D structural diagram of the original diatom, and (b) is a three-dimensional distribution diagram of La nanoparticles in the diatom shell. DETAILED DESCRIPTION

[0033] In order to explain in detail the preparation method of the material of the present invention and its application in the negative electrode material of lithium ion batteries, further description will be given below in conjunction with specific embodiments and accompanying drawings.

[0034] Example 1

[0035] (1) Prepare a 1 g / L lanthanum chloride solution. Add 2 mL of 1 g / L lanthanum chloride solution to 2 L of diatom culture medium. Shake well and inoculate 200 mL of diatom seed solution. Place the culture medium in a light incubator and culture for 10 days. The culture temperature is 25°C and the light intensity is 4000 Lux.

[0036] (2) Filter the cultured algae solution to obtain enriched algae solution, add 5% hydrochloric acid to the enriched algae solution in (1), and let it stand for 3 hours to allow the hydrochloric acid and carbonate to fully react and remove impurities, thereby obtaining a hydrochloric acid diatom mixed solution;

[0037] (3) Centrifuge the HCl diatom mixture in (2) at 8000 rpm for 10 min, remove the supernatant, and obtain the diatom precipitate treated with hydrochloric acid;

[0038] (4) adding ethanol to the diatom precipitate after acid washing with HCl solution in (3) to extract the pigments and impurity ions in the diatom cells to obtain an ethanol mixture;

[0039] Dosage: Add 50 mL of ethanol to the diatom precipitate obtained in step (4).

[0040] (5) Centrifuge the ethanol mixture in (4) at 5000 rpm for 10 min, remove the supernatant, and obtain the diatom precipitate treated with ethanol;

[0041] (6) freeze-drying the diatom precipitate obtained in (5) at -70°C to obtain the modified diatom material;

[0042] (7) The modified diatom material in (6) was heated to 600°C at a rate of 5°C / min under an argon atmosphere and calcined at high temperature for 3 h. The La nanoparticle-loaded bio-silica anode material (DBS@C-La-1) was prepared.

[0043] (8) The active material prepared in the present invention was mixed with Super P and PVDF in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) was added and ball milled at 500 r / min for 3 h to obtain a uniformly mixed electrode slurry. The slurry was coated on copper foil with a thickness of 50 μm, dried in a vacuum at 80°C, and cut to obtain electrode sheets. After cutting, circular electrode sheets with a diameter of 12 mm were obtained.

[0044] (9) Place the cut electrode sheet on the lower shell of the battery in an argon-filled glove box, add 1 drop of electrolyte on the surface of the electrode sheet, place the diaphragm, add another drop of electrolyte, and finally put the lithium sheet in. Cover the battery cover and seal it on a button battery packaging machine to complete the battery assembly.

[0045] (10) The assembled battery was subjected to impedance spectroscopy testing on a Gamry electrochemical workstation with a test frequency range of 100 kHz to 0.01 Hz. The impedance spectroscopy results are as follows: Figure 6 As shown, the charge transfer impedance is small. The assembled batteries were subjected to constant current charge and discharge tests on the LAND battery charge and discharge test system, with the test voltage range of 0.001 ~ 3.0 V (vs. Li / Li + ), the current density is 100 mA·g -1 , the long cycle performance curve is as follows Figure 3 As shown, the electrode obtained ~ 782 mAh g after 150 cycles. -1 The assembled battery was subjected to cyclic voltammetry test on an electrochemical workstation with a test voltage range of 0.001 ~ 3.0 V (vs. Li / Li + ), the cyclic voltammetry curve is as follows Figure 4 As shown in c, additional redox peaks can be observed in the cyclic voltammetry curve, indicating that La participates in the redox reaction of the electrochemical system and improves the discharge capacity. Figure 5 As shown, the rate performance is good.

[0046] Example 2: The only difference from Example 1 is that:

[0047] Prepare a 1 g / L lanthanum chloride solution and add 20 mL of 1 g / L lanthanum chloride solution to 2 L of diatom culture medium. The remaining steps are the same to prepare the La nanoparticle-loaded diatom biogenic silica electrode material (DBS@C-La-10).

[0048] The assembled battery was tested on a Gamry electrochemical workstation with an impedance spectroscopy test in the frequency range of 100kHz to 0.01Hz. The impedance spectroscopy results are as follows: Figure 6 As shown, the charge transfer impedance is small. The assembled battery was subjected to cyclic charge and discharge tests on the LAND battery charge and discharge test system, with the test voltage range of 0.001 ~ 3.0 V (vs. Li / Li + ), the current density is 100 mA·g -1 , the long cycle curve is as follows Figure 3 As shown in Figure 2, the electrode obtained ~843 mAh·g after 150 cycles. -1 The assembled battery was subjected to cyclic voltammetry test on an electrochemical workstation with a test voltage range of 0.001 ~ 3.0 V (vs. Li / Li + ), the cyclic voltammetry curve is as follows Figure 4 d, the rate performance is as follows Figure 6 As shown, the magnification performance is good. Through transmission electron microscopy, obvious La nanoparticles can be observed on the surface of diatom shells. Figure 7 It can be seen that La exists not only on the surface of the diatom shell, but also inside the shell, realizing the in vivo and in vitro modification of the diatom shell by La nanoparticles.

[0049] Example 3: The only difference from Example 1 is that:

[0050] The rare earth element configured was yttrium chloride with a concentration of 1 g / L. 2 mL of 1 g / L yttrium chloride solution was added to 2 L of diatom culture medium. The remaining steps were the same as in Example 1 to prepare a Y nanoparticle-loaded diatom biogenic silica electrode material (DBS@CY-1).

[0051] The assembled battery was tested on a Gamry electrochemical workstation with an impedance spectroscopy test in the frequency range of 100kHz to 0.01Hz. The impedance spectroscopy results are as follows: Figure 6 As shown; the assembled battery was subjected to cycle charge and discharge test on the LAND battery charge and discharge test system, with the test voltage range of 0.001 ~ 3.0 V (vs. Li / Li +), the current density is 100 mA·g -1 , the long cycle curve is as follows Figure 3 As shown in Figure 2, the electrode achieved ~707 mAh·g after 150 cycles. -1 The assembled battery was subjected to cyclic voltammetry test on an electrochemical workstation with a test voltage range of 0.001 ~3.0 V (vs. Li / Li + ), the cyclic voltammetry curve is as follows Figure 4 As shown in e, the rate performance curve is Figure 5 As shown, the rate performance is good.

[0052] Example 4: The only difference from Example 1 is that:

[0053] The rare earth element used was yttrium chloride at a concentration of 1 g / L. 20 mL of 1 g / L yttrium chloride solution was added to 2 L of diatom culture medium. The remaining steps were the same to prepare the Y nanoparticle-loaded diatom biosilica negative electrode material (DBS@CY-10).

[0054] The assembled battery was tested on a Gamry electrochemical workstation with an impedance spectroscopy test in the frequency range of 100kHz to 0.01Hz. The impedance spectroscopy results are as follows: Figure 6 As shown; the assembled battery was subjected to cycle charge and discharge test on the LAND battery charge and discharge test system, with the test voltage range of 0.001 ~ 3.0 V (vs. Li / Li + ), the current density is 100 mA·g -1 , the long cycle curve is as follows Figure 3 As shown, the electrode obtained ~ 743 mAh·g after 150 cycles. -1 The assembled battery was subjected to cyclic voltammetry test on an electrochemical workstation with a test voltage range of 0.001 ~3.0 V (vs. Li / Li + ), the cyclic voltammetry curve is as follows Figure 4 f, the rate performance curve is as follows Figure 5 As shown in Figure 2, transmission electron microscopy (TEM) reveals that distinct Y nanoparticles can be observed on the surface of diatom shells.

[0055] Comparative Example 1:

[0056] This comparative example provides an untreated diatom material, which differs from the embodiment only in that:

[0057] No rare earth compound solution was added during the culture step, and the remaining steps remained unchanged.

[0058] The diatom material (DBS@C) obtained in Comparative Example 1 showed a relatively smooth surface and no nanoparticle loading as observed by transmission electron microscopy and scanning electron microscopy. Its capacity was lower than that of the modified diatom materials described in Examples 1, 2, 3, and 4, with poor capacity and cycling stability and high impedance. After 150 cycles, the discharge capacity was 304 mAh·g -1 , the cyclic voltammetry test curve is as follows Figure 4 As shown in a, the rate performance curve is as follows Figure 6 As shown, the rate performance is poor.

[0059] Comparative Example 2:

[0060] This comparative example provides a modified diatom material obtained by culturing diatoms using a semipermeable membrane-wrapped ionic rare earth ore. The difference from Example 1 is that lanthanum chloride or yttrium chloride is not used in the culturing step, and an ionic rare earth ore wrapped with a semipermeable membrane is added to the diatom culture medium for culturing. The specific steps are as follows:

[0061] Weigh 2.0 g of ionic rare earth ore from Jianghua, Hunan. This ionic rare earth ore contains 16 rare earth elements (lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium) as well as silicon and aluminum. Wrap it with a semipermeable membrane with a molecular weight cutoff of 8000 Da and place it in 2 L of culture medium for co-cultivation with diatoms. The initial total rare earth ion content of the culture system is approximately 10.4 mg.

[0062] The remaining steps remained unchanged. The obtained semipermeable membrane wrapped cultured diatom composite material was named DBS@C-REE-2.0. Scanning electron microscopy and transmission electron microscopy showed that the diatom surface was smooth and had no rare earth nanoparticles loaded. The cyclic voltammetry test curve was as follows: Figure 4 As shown in b, the rate performance is poor. Compared with the modified diatom materials described in Examples 1, 2, 3, and 4, the electrode material in Comparative Example 2 has poor capacity and cycle stability, and a large charge transfer impedance. After 150 cycles, the discharge capacity is 380 mAh·g -1 , the rare earth nanoparticle-loaded diatom biosilica material exhibited excellent electrochemical performance in the battery test procedure, demonstrating the effectiveness of this modification method.

Claims

1. A rare earth nanoparticle-loaded bio-silica negative electrode material, characterized by: The biomineralization of diatoms is utilized to add at least one of LaCl3 and YCl3 as an additive to the diatom growth medium, so that rare earth elements are absorbed into diatom cells and processed into rare earth nanoparticles, which are then calcined under an inert atmosphere to obtain the obtained rare earth nanoparticles.

2. The method for preparing the rare earth nanoparticle-loaded biosilica negative electrode material according to claim 1, comprising the following steps: 1) Loading diatoms with rare earth nanoparticles: Adding rare earth ion solution to diatom culture medium, inoculating diatoms for cultivation; 2) Diatom collection and pretreatment: After the incubation period, the algae solution is filtered or centrifuged to obtain a diatom precipitate, which is then washed with at least one of hydrochloric acid or sulfuric acid. The acid-washed diatom solution is separated into solid and liquid, and the precipitate is collected and washed with at least one of methanol or ethanol. After solid-liquid separation, the diatom precipitate is collected; 3) The diatom precipitate loaded with rare earth nanoparticles is freeze-dried and calcined at high temperature to obtain a rare earth nanoparticle-loaded bio-silica composite material.

3. The method according to claim 2, wherein: Step 1) preparing a solution of at least one of LaCl3 and YCl3 with a concentration of 0.1 g / L to 1 g / L.

4. The method according to claim 2 or 3, wherein: Step 1) Add 5-20 mL of rare earth compound solution to 1-2 L of diatom culture medium and inoculate 100-200 mL of diatom seed solution.

5. The method according to claim 2, 3 or 4, characterized in that: Step 1) The diatom culture period is 10-14 days, the culture temperature is 22°C-25°C, and the light intensity is 2000 Lx-4000 Lx.

6. The method according to claim 2 or 3, wherein: Step 2) Collecting the cultured algal liquid for acid washing; Specifically, the enriched algal liquid is acid washed with 2%-5% dilute hydrochloric acid; After acid washing, the mixture is centrifuged at 8000-10000 rpm for at least 10 minutes to separate the solid and liquid and collect the precipitate; The acid washed precipitate is washed with ethanol 1-2 times until the washing solution is colorless and transparent.

7. The method according to claim 2 or 3, wherein: Step 3) Freeze-dry the diatom pellet at -70°C for at least 24 h.

8. The method according to claim 3 or 4, characterized in that Step 3) The dried diatom mixture is heated to 600-900°C at a rate of 5-10°C / min under an argon atmosphere and kept at this temperature for 1-3 hours.

9. Use of the negative electrode material according to claim 1 or the rare earth nanoparticle-loaded biosilica negative electrode material obtained by the method according to any one of claims 2 to 8, characterized in that: Used for the preparation of negative electrode materials for lithium-ion batteries.

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