Solid-state lithium super-ion conductor sheet for lithium isotope separation as well as preparation method and application of solid-state lithium super-ion conductor sheet

Abstract

The invention belongs to the technical field of isotope separation, and particularly discloses a solid-state lithium super-ion conductor for electrochemical separation of lithium isotopes and a preparation method and separation application of the solid-state lithium super-ion conductor. The method comprises the following steps: performing centrifugal oscillation on oxide electrolyte powder and a binder, fully mixing, compacting, cutting into oxide electrolyte and binder sheets with fixed areas, and performing high-temperature sintering to prepare the lithium super-ion conductor sheet for lithium isotope separation. The lithium isotope-enriched lithium super-ion conductor sheet prepared by the invention can enable 6Li < + > and 7Li < + > to pass differently, and meanwhile, an electromigration technology and a similar element separation technology are combined, so that the separation coefficient of the 6Li < + > / 7Li < + > is improved, and effective separation and enrichment of the lithium isotope are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of isotope separation, and in particular relates to a solid lithium superionic conductor sheet for lithium isotope separation, and a preparation method and application thereof. Background Art

[0002] Energy is the cornerstone of modern social development and is related to human life and economy. Traditional fossil fuels such as coal and oil have brought environmental problems, prompting people to rethink the way of energy development. Clean energy has become the focus of attention, among which nuclear energy has received attention from the government, and nuclear fusion is considered an ideal choice. Compared with nuclear fission, nuclear fusion has more abundant raw materials, higher energy output and less radioactive waste. Nuclear fusion requires deuterium and tritium. Deuterium is abundant in seawater, while tritium is scarce and can be obtained through 6 Li and slow neutron bombardment. Therefore, 6 Li, as a tritium multiplier, is a key material for nuclear fusion. 6 Li and 7 Li accounts for 7.59% and 92.41% respectively.

[0003] With the continuous advancement and maturity of fission reactor technology and fusion reactor technology, the global demand for high-abundance lithium (Li) and tritium (T) continues to increase. The existing lithium isotope production capacity is difficult to meet the needs of the future nuclear industry, and the gap between supply and demand is huge. 6 Although the lithium amalgam method can achieve a good separation factor (1.03–1.06) and keep the cost low, it also causes environmental pollution. Therefore, it is urgent to develop new alternative lithium isotope separation methods. Summary of the invention

[0004] The main purpose of the present invention is to provide a solid lithium superionic conductor for electrochemical separation of lithium isotopes and its preparation method and separation application, so as to overcome the shortcomings of the prior art.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0006] The oxide electrolyte powder and the binder are centrifugally shaken to be fully mixed, compacted, and cut into oxide electrolyte@binder sheets of a fixed area, and then sintered at a high temperature to obtain lithium superion conductor sheets for lithium isotope separation.

[0007] Preferably, the oxide electrolyte comprises Li 1+x Al x Ti 2-x (PO4)3、Li 1+x Al x Ge 2-x (PO4)3, garnet-type Li7La3Zr2O12 , Perovskite-type Li 3y La 2 / 3–y One or more of the electrolytes obtained by doping TiO3 and above substances with other elements, wherein 0<x<1, 0.04<y<0.17.

[0008] Preferably, the binder includes one or more of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethyleneimine (PEI) and polytetrafluoroethylene (PTFE); wherein polytetrafluoroethylene has a structure as shown below:

[0009]

[0010] Preferably, the mass ratio of the oxide electrolyte powder to the binder is (4-500):1.

[0011] Preferably, the compaction pressure of the oxide electrolyte@binder sheet is 10 to 500 MPa, and the compaction thickness is 0.5 to 5 mm.

[0012] Preferably, when the oxide electrolyte @ binder sheet is sintered by a conventional sintering method, the sintering temperature during the sintering process is 800-1400°C, and the insulation time is 1-15 hours to obtain a lithium superion conductor sheet; when the oxide electrolyte @ binder sheet is sintered by a vacuum hot pressing method, the sintering temperature during the sintering process is 800-1400°C, and the sintering time is 120-300 seconds.

[0013] The present invention also provides a lithium superion conductor sheet for lithium isotope separation, which is prepared according to any one of the preparation methods described above.

[0014] The present invention also provides the lithium superion conductor sheet for separation and enrichment of lithium isotopes. 6 The uses of Li include:

[0015] The anode, cathode, anolyte, cathode liquid and lithium super ion conductor sheet together constitute an electromigration system; wherein the anolyte is arranged in the anode chamber, the cathode liquid is arranged in the cathode chamber, the lithium super ion conductor sheet is arranged between the anode chamber and the cathode chamber as a permeation medium, and the selective separation and enrichment 6 The lithium superion conductor sheet of Li is the lithium superion conductor sheet for lithium isotope separation as described above;

[0016] The electromigration system is energized to obtain enrichment in the cathode chamber. 6 Li cathode aqueous solution.

[0017] Preferably, the anolyte is a lithium salt solution, and the lithium salt contained in the lithium salt solution includes any one or a combination of two or more of lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium acetate, lithium sulfate, lithium nitrate, lithium perchlorate, lithium trifluoroacetate, and lithium bis(trifluoromethanesulfonyl)imide.

[0018] Preferably, the concentration of lithium ions in the lithium salt solution is 0.1 to 20 mol / L.

[0019] Preferably, the cathode liquid is one or more of pure water, NaCl, KCl, NH4Cl, Na2SO4, K2SO4, (NH4)2SO4, NaNO3, KNO3 and NH4NO3 aqueous solution.

[0020] Preferably, the anode material is graphite, copper, nickel or stainless steel, and the cathode material is graphite, copper, nickel or tin.

[0021] Preferably, the amount of the cathode liquid added is 1.5 times that of the anode liquid. Specifically, the amount of the anode liquid added is 10 ml to 1000 ml.

[0022] Preferably, the voltage applied during powering on the electromigration system is in the range of 0.1V to 10V.

[0023] Preferably, the power-on time is 15 to 1440 minutes.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The method for preparing lithium superion conductor flakes proposed in the present invention realizes the dry-process preparation of lithium superion conductor flakes with feasibility and effectiveness, and provides a technical entry point for realizing the large-scale preparation of lithium superion conductor flakes with high efficiency and low cost. At the same time, it actively develops the advantages of interdisciplinary fields, applies the cutting-edge technology in the field of new energy materials and devices to the field of similar element enrichment, and promotes the integration and promotion of disciplines. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0027] Figure 1 The present invention is a flow chart for preparing the lithium superion conductor sheet;

[0028] Figure 2 This is an optical photograph of the lithium superion conductor of the present invention;

[0029] Figure 3 This is a microscopic morphology diagram of the lithium superion conductor of the present invention;

[0030] Figure 4 The schematic diagram is a principle diagram of using the lithium superion conductor sheet of the present invention for lithium isotope separation. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0032] Example 1

[0033] A lithium super ion conductor sheet comprises the following components by mass percentage: 1% binder (PTFE) and 99% oxide electrolyte powder (Li 1.3 Al 0.3 Ti 1.7 (PO4)3). The compaction pressure of the lithium superion conductor sheet is 240MPa; the sintering temperature is 850℃, and the holding time is 360min; the area after sintering is 2.1cm×2.1cm, and the thickness is 0.52mm. The sintered lithium superion conductor sheet is fixed on the separator, and the separator is separated by physical methods to form an anode chamber and a cathode chamber. 50ml of 0.2g·L -1 LiCl solution (initial 6 Li / 7 Li is 0.0719), 75ml of pure water is added to the cathode chamber, the anode electrode is a nickel sheet, and the cathode electrode is a tin sheet. The electrode voltage is set to 0.8V. After power is turned on, the cathode aqueous solution is taken once in the cathode chamber at 10, 15, 20, 30, and 60 minutes for isotope testing. Table 1 shows the separation coefficient at different times. In the long-term separation process, the performance of the solid electrolyte in the solution system will decrease significantly, resulting in a decrease in the separation factor. Although the separation factor increases at 30 minutes, it is an accidental phenomenon. Overall, the separation factor still shows a downward trend. More than 10% can be achieved in about 60 minutes. 6 Li enrichment while maintaining a relatively high separation factor.

[0034] Table 1 Separation coefficient changes with time

[0035] Time (min) 10 15 20 30 60 Separation factor 1.206 1.169 1.096 1.112 1.048

[0036] Example 2

[0037] A lithium super ion conductor sheet comprises the following components by weight: 4% binder (PTFE) and 96% oxide electrolyte powder (Li 1.3 Al 0.3 Ti 1.7(PO4)3). The compaction pressure of the lithium superion conductor sheet is 240MPa; the sintering temperature is 850℃, and the holding time is 360min; the area after sintering is 2.1cm×2.1cm, and the thickness is 0.73mm. The sintered lithium superion conductor sheet is fixed on the separator, and the separator is separated by physical methods to form an anode chamber and a cathode chamber. 50ml of 0.2g·L -1 LiCl solution (initial 6 Li / 7 Li is 0.0719), 75 ml of pure water is added to the cathode chamber, the anode electrode is a nickel sheet, and the cathode electrode is a tin sheet. The electrode voltage is set to 0.8 V. After 60 minutes of power on, the separation coefficient is 1.018.

[0038] Example 3

[0039] A lithium super ion conductor sheet comprises the following components by mass percentage: 0.5% binder (PTFE) and 99.5% oxide electrolyte powder (Li 1.3 Al 0.3 Ti 1.7 (PO4)3). The compaction pressure of the lithium superion conductor sheet is 240MPa; the sintering temperature is 850℃, and the holding time is 360min; the area after sintering is 2.1cm×2.1cm, and the thickness is 0.71mm. The sintered lithium superion conductor sheet is fixed on the separator, and the separator is separated by physical methods to form an anode chamber and a cathode chamber. 50ml of 0.2g·L -1 LiCl solution (initial 6 Li / 7 Li is 0.0719), 75 ml of pure water is added to the cathode chamber, the anode electrode is a nickel sheet, and the cathode electrode is a tin sheet. The electrode voltage is set to 0.8 V. After 60 minutes of power on, the separation coefficient is 1.030.

[0040] By comparing the addition of 0.5%, 1% and 4% PTFE, the support structure formed by a small amount of addition is poor, which affects the structure after sintering. The excessive addition of the binder occupies too much volume, which increases the pores formed after sintering and affects the performance of the solid electrolyte. Overall, the 1% addition is relatively optimal.

[0041] Example 4

[0042] A lithium super ion conductor sheet comprises the following components by mass percentage: 1% binder (PTFE) and 99% oxide electrolyte powder (Li 1.3 Al 0.3 Ti 1.7(PO4)3). The compaction pressure of the lithium superion conductor sheet is 160MPa; the sintering temperature is 950℃, and the holding time is 360min; the area after sintering is 2.1cm×2.1cm, and the thickness is 0.58mm. The sintered lithium superion conductor sheet is fixed on the separator, and the separator is separated by physical methods to form an anode chamber and a cathode chamber. 40ml of 0.2g·L -1 LiCl solution (initial 6 Li / 7 Li is 0.0719), 60 ml of pure water is added to the cathode chamber, the anode electrode is a nickel sheet, and the cathode electrode is a tin sheet. The electrode voltage is set to 0.8 V. After power is turned on, the cathode aqueous solution is taken from the cathode chamber for isotope testing at 10, 15, 20, 30, and 60 minutes. After power is turned on for 60 minutes, the separation coefficient is 1.026.

[0043] Example 5

[0044] The sintering temperature in Example 4 was changed to 800°C, 850°C, 900°C, and 1000°C, and the other steps remained unchanged. The thickness difference after sintering was within 2%. Isotope test was carried out, and after 60 minutes of power-on, the separation coefficient obtained was shown in Table 2. It can be seen from Table 2 that the change in the separation coefficient first increased and then decreased. The reason is that the solid electrolyte grains at a lower sintering temperature do not grow sufficiently, and there are obvious gaps and poor contact inside, resulting in a relatively low separation coefficient; when the temperature rises, the grains continue to grow, and when it rises to a certain temperature, the large grains are covered and disappear, and the stacking phenomenon between the grains disappears, forming a good conduction channel and interface relationship, and the separation coefficient increases accordingly; but too high a temperature will cause lithium to volatilize, destroying normal ion conduction, resulting in a decrease in the separation coefficient during the separation process.

[0045] Table 2 Separation coefficient at different sintering temperatures

[0046] Sintering temperature(℃) 800 850 900 950 1000 Separation factor 1.020 1.048 1.036 1.026 1.010

[0047] Example 6

[0048] A lithium super ion conductor sheet comprises the following components by mass percentage: 1% binder (PTFE) and 99% oxide electrolyte powder (Li 6.75 Ln3Z 1.75 Ta 0.25 O 12 ). The compaction pressure of the lithium superion conductor sheet is 240MPa; the sintering temperature is 1300℃, and the holding time is 360min; the area after sintering is 2.1cm×2.1cm, and the thickness is 0.54mm. The sintered lithium superion conductor sheet is fixed on the separator, and the separator is separated by physical methods to form an anode chamber and a cathode chamber. 50ml of 0.2g·L -1LiCl solution (initial 6 Li / 7 Li is 0.0719), 75 ml of pure water is added to the cathode chamber, the anode electrode is a nickel sheet, and the cathode electrode is a tin sheet. The electrode voltage is set to 0.8 V. After 15 minutes of power on, the cathode aqueous solution is taken once in the cathode chamber for isotope testing, and the separation coefficient is 1.020.

Claims

1. A dry method for preparing a lithium superion conductor sheet for separation of lithium isotopes, wherein the lithium isotopes include 6 Li and 7 Li two stable lithium isotopes, characterized in that, The method comprises: fully mixing oxide electrolyte powder and a binder by centrifugal shaking, compacting and cutting into oxide electrolyte@binder sheets of fixed area, and then sintering at high temperature to obtain lithium superion conductor sheets for lithium isotope separation.

2. The preparation method according to claim 1, characterized in that: The oxide electrolyte includes 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 electrolytes obtained by doping TiO3 and above with other elements, wherein 0<x<1, 0.04<y<0.17; the binder comprises one or more of polyvinylidene fluoride, polyacrylic acid, polyvinyl alcohol, polyethylene fluoride and polytetrafluoroethylene; wherein polytetrafluoroethylene has a structure as shown below:

3. The preparation method according to claim 1, characterized in that: The mass ratio of the oxide electrolyte powder to the binder is (4-500):

1.

4. The preparation method according to claim 1, characterized in that: The oxide electrolyte@binder sheet is compacted by a moldless static pressing method or an isostatic pressing method. The compaction pressure of the oxide electrolyte@binder sheet is 10 to 500 MPa, and the compaction thickness is 0.5 to 5 mm.

5. The preparation method according to claim 1, characterized in that: When the oxide electrolyte @ binder sheet is sintered by a conventional sintering method, the sintering temperature during the sintering process is 800-1400°C, and the insulation time is 1-15 hours to obtain a lithium superion conductor sheet; when the oxide electrolyte @ binder sheet is sintered by a vacuum hot pressing method, the sintering temperature during the sintering process is 800-1400°C, and the sintering time is 120-300 seconds.

6. A lithium superion conductor sheet for lithium isotope separation prepared by the preparation method according to any one of claims 1 to 5.

7. A method for separating lithium isotopes, characterized in that: include: The anode, cathode, anolyte, cathode liquid and lithium super ion conductor sheet together constitute an electromigration system; wherein the anolyte is arranged in the anode chamber, the cathode liquid is arranged in the cathode chamber, the lithium super ion conductor sheet is arranged between the anode chamber and the cathode chamber as a permeation medium, and the selective separation and enrichment 6 The lithium superion conductor sheet of Li is the lithium superion conductor sheet for lithium isotope separation as claimed in claim 6; The electromigration system is energized to obtain enrichment in the cathode chamber. 6 Li cathode aqueous solution.

8. The method according to claim 7, characterized in that: The anolyte is a lithium salt solution, wherein the lithium salt contained in the lithium salt solution includes any one or a combination of two or more of lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium acetate, lithium sulfate, lithium nitrate, lithium perchlorate, lithium trifluoroacetate, and lithium bis(trifluoromethanesulfonyl)imide, and the concentration of lithium ions in the lithium salt solution is 0.1 to 20 mol / L; the cathode liquid is one or more of pure water, NaCl, KCl, NH4Cl, Na2SO4, K2SO4, (NH4)2SO4, NaNO3, KNO3 and NH4NO3 aqueous solution; the anode material is graphite, copper, nickel or stainless steel, and the cathode material is graphite, copper, nickel or tin.

9. The method according to claim 7, characterized in that: The amount of the cathode liquid added is 1.5 times that of the anode liquid.

10. The method according to claim 7, characterized in that: The voltage range of the electromigration system is 0.1V to 10V, and the electromigration time is 15 to 1440 minutes.

Images