Preparation method of high-density lithium super ionic conductor for lithium extraction from salt lake

Abstract

The application provides a preparation method of high-density lithium super ionic conductor for lithium extraction from salt lake. The method is as follows: oxide lithium super ionic conductor powder and low-melting-point metal powder are ball-mixed according to a mass ratio, the mixed material after ball-milling is pressed into a sheet and sintered to obtain high-density lithium super ionic conductor, and the high-density lithium super ionic conductor is applied to the lithium extraction process from salt lake by electrodialysis. The method utilizes the spontaneous filling of low-melting-point metal into the micro-cracks in the lithium super ionic conductor during the sintering process of the lithium super ionic conductor, improves the stability of the lithium super ionic conductor in the lithium extraction process from salt lake, and meanwhile, the metal material has good lithium conduction effect, so that the lithium extraction rate of the lithium super ionic conductor can be further improved.

Description

Technical Field

[0001] This invention belongs to the field of materials science, specifically relating to a method for preparing a high-density lithium superionic conductor for lithium extraction from salt lakes. Background Technology

[0002] Using lithium superion conductors for lithium extraction from salt lakes offers advantages such as high extraction efficiency and low energy consumption. However, structural defects such as internal microcracks result in low material density. During long-term lithium extraction, brine from the salt lake can easily penetrate the bulk phase of the material through these surface microcracks, exacerbating crack propagation and leading to structural failure of the lithium superion conductor. This significantly impacts the lifespan of the superion conductor in lithium extraction production. Existing methods to improve the density of lithium superion conductors mainly involve filling them with low-hardness, non-electronic conductor inorganic or organic materials to construct composite materials. These materials, with their low Young's modulus, fill the microcracks in the lithium superion conductor. However, this method increases the amount of ineffective lithium-conducting components and reduces the proportion of lithium superion conductors with lithium-conducting effects. While this method is widely used in all-solid-state lithium-ion batteries, in the field of lithium extraction from salt lakes, the solution system is more difficult to conduct lithium ions than the solid-phase battery system. Applying this method to modify the lithium superion conductor will significantly sacrifice the lithium extraction efficiency, greatly affecting the extraction cost and efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a high-density lithium superionic conductor for lithium extraction from salt lakes. The method aims to spontaneously fill the microcracks inside the lithium superionic conductor with a low-melting-point metal during the sintering process, thereby improving the stability of the ionic conductor during lithium extraction from salt lakes. At the same time, the metal material has good lithium conduction properties, which can further improve the lithium extraction rate of the ionic conductor.

[0004] To achieve the above objectives, this invention proposes a method for preparing a high-density lithium superionic conductor for lithium extraction from salt lakes, comprising the following steps:

[0005] 1) The lithium oxide superionic conductor powder and the low melting point metal powder were ball-milled and mixed at a mass ratio;

[0006] 2) The ball-milled mixture is pressed into sheets and sintered to obtain a high-density lithium superion conductor, wherein the sintering temperature is higher than the melting point of the metal added in step 1).

[0007] 3) The prepared high-density lithium superionic conductor was applied to the lithium extraction process from salt lakes by electrodialysis.

[0008] Preferably, the lithium oxide superionic conductor is Li. 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x(PO4)3, Garnet-type Li7La3Zr2O 12 Perovskite-type Li 3y La 2 / 3–y One or more of the following ionic conductors are obtained by doping TiO3 and above with other elements, wherein 0≤x≤0.5 and 0.04<y<0.17.

[0009] Preferably, the metal powder in step 1) is one or more of aluminum, zinc, germanium, gold, silver, tin, and indium.

[0010] Preferably, the mass ratio of lithium oxide superionic conductor powder to metal powder is 1:1 to 100:1.

[0011] Preferably, the particle size of the lithium oxide superionic conductor powder and the metal powder is 10 nm-50 μm.

[0012] Preferably, the Li in the salt lake brine + Concentrations of 0.1 g / L - 2 g / L, Mg 2+ Concentration / Li + The concentration is 1-2000, and the applied voltage for electrodialysis is ≤1.2V.

[0013] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0014] (1) In this invention, low melting point metals are used to fill the microcracks inside the lithium superion conductor, which greatly improves the structural stability of the ion conductor in brine and extends its working life.

[0015] (2) The present invention utilizes a metal with lithium-conducting properties as a filler to provide a second channel for lithium ions to pass through the ion conductor, thereby improving the lithium extraction rate of the ion conductor.

[0016] (3) The high-density lithium superion conductor prepared by the present invention has good recyclability and can be re-sintered after failure by ball milling, adding elements. Attached Figure Description

[0017] Figure 1 The XRD diffraction pattern of the lithium superionic conductor LATP-5% Ag prepared in Example 1 of this invention;

[0018] Figure 2 The Li in the extract obtained in Example 1 of this invention + / Mg 2+ A graph showing the relationship over time, where the arrows indicate the vertical axis of the lines;

[0019] Figure 3This is a graph showing the relationship between the separation coefficient and lithium recovery rate of the device obtained in Example 1 of the present invention and time. The arrows indicate the vertical axis of the line. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it.

[0021] Example 1:

[0022] 1μm Li 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP) ionic conductor powder and 1μm Ag powder were ball-milled at a mass ratio of 20:1. The ball-milled mixture was then pressed into tablets and sintered at 850℃ to obtain the lithium superionic conductor LATP-5% Ag. This ionic conductor was applied to the electrodialysis extraction of Li. + The concentration is 0.16 g / L, Mg 2+ Concentration / Li + Salt lake brine with a concentration (Mg / Li) of 500 (both brine and extract volumes were 50 ml) was used, and the electrodialysis voltage was 1.0 V. The Li content in the extract was measured at 1 h, 3 h, 6 h, and 10 h. + Mg 2+ concentration.

[0023] Figure 1 SEM image of the LATP-5% Ag ion conductor prepared after sintering. Li in the extract. + Mg 2+ The concentrations are shown in Table 1. Figure 3 Table 2 shows the relationship between the separation coefficient and lithium recovery rate obtained in Example 1 of this invention over time. Table 2 displays the device separation coefficient (the ratio of initial raw halogen Mg / Li to extract Mg / Li), used to determine the device's ability to recover Li. + Selectivity is important, and a higher separation coefficient is better. Table 3 shows the relationship between lithium recovery rate and time (Li in the extract). + Mass and Li in the initial raw brine + The mass ratio can also be used when the volumes of the extract and the original brine are equal, using the corresponding Li. + (Concentration ratio) is used to determine the device's effect on Li + The higher the throughput and recovery rate, the better.

[0024] Table 1 Ion concentrations in the extract

[0025]

[0026] Table 2 Separation coefficients

[0027] Separation coefficient 7200 11554 11727 11951

[0028] Table 3 Device for Li + recovery rate

[0029] Recovery rate % 1.35 5.34 8.06 10.76

[0030] Example 2:

[0031] 100nm Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP) ionic conductor powder and 100 nm Sn powder were ball-milled at a mass ratio of 10:1. The ball-milled mixture was then pressed into tablets and sintered at 875 °C to obtain the lithium superionic conductor LAGP-10% Sn. Li was extracted from this ionic conductor using electrodialysis. + The concentration is 0.1 g / L, Mg 2+ Concentration / Li + Salt lake brine with a concentration (Mg / Li) of 100 (50 ml brine volume, 80 ml extract volume) was extracted using electrodialysis at a voltage of 1.2 V for 15 h. The Li / Mg ratio in the extract was 112.55, the separation coefficient was 11255, and the lithium recovery rate was greater than 14.1%.

[0032] Example 3:

[0033] 500nm Li7La3Zr2O 12 (LLZO) ionic conductor powder and 200 nm Zn powder were ball-milled at a mass ratio of 25:1. The ball-milled mixture was then pressed into tablets and sintered at 1175 °C to obtain the lithium superionic conductor LLZO-4% Zn. Li was extracted from this ionic conductor using electrodialysis. + The concentration is 0.15 g / L, Mg 2+ Concentration / Li + Salt lake brine with a concentration (Mg / Li) of 300 (50 ml brine volume, 75 ml extract volume) was extracted using electrodialysis at a voltage of 0.9 V for 20 h. The Li / Mg ratio in the extract was 32.42, the separation coefficient was 9726, and the lithium recovery rate was 16.7%.

[0034] Example 4:

[0035] 10μm Li 0.35 La 0.55 TiO3 (LLTO) ionic conductor powder and 500 nm Au powder were ball-milled at a mass ratio of 50:1. The ball-milled mixture was then pressed into tablets and sintered at 1100 °C to obtain the lithium superionic conductor LLTO-2% Au. Li was extracted from this ionic conductor using electrodialysis.+ The concentration is 0.1 g / L, Mg 2+ Concentration / Li + Salt lake brine with a Mg / Li ratio of 150 (both brine and extract volumes were 50 ml) was extracted using an electrodialysis voltage of 0.8 V. After 50 h of extraction, the Li / Mg ratio in the extract was 48.06, the separation coefficient was 7210, and the lithium recovery rate was 37.9%.

Claims

1. A method for preparing a high-density lithium superionic conductor for lithium extraction from salt lakes, characterized in that, The method includes the following steps: 1) The lithium oxide superionic conductor powder and the low melting point metal powder are ball-milled and mixed at a mass ratio of 1:1 to 100:

1. 2) The ball-milled mixture is pressed into sheets and sintered to obtain a high-density lithium superion conductor, wherein the sintering temperature is higher than the melting point of the metal added in step 1); 3) The prepared high-density lithium superionic conductor was applied to the lithium extraction process from salt lakes by electrodialysis.

2. The method as described in claim 1, characterized in that, Lithium oxide superionic conductor is Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Garnet-type Li7La3Zr2O 12 Perovskite-type Li 3y La 2 / 3–y One or more of the following ionic conductors are obtained by doping TiO3 and higher substances with other elements, wherein 0 ≤ x ≤0.5, 0.04< y <0.

17.

3. The method as described in claim 1, characterized in that, The metal powder in step 1) is one or more of aluminum, zinc, germanium, gold, silver, tin, and indium.

4. The method as described in claim 1, characterized in that, The particle size of lithium oxide superionic conductor powder and metal powder is 10 nm-50 μm.

5. The method as described in claim 1, characterized in that, Li of salt lake brine + Concentrations of 0.1 g / L-2 g / L, Mg 2+ Concentration / Li + The concentration is 1-2000, and the applied voltage for electrodialysis is ≤1.2 V.

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