Method for separating hydrogen isotope through charge-discharge cycle of lithium-hydrogen battery

Abstract

The invention discloses a method for separating hydrogen isotope through lithium-hydrogen battery charge-discharge cycle. The method for separating the hydrogen isotope comprises the following steps: step 1, taking a catalyst as a positive electrode, taking lithium metal as a negative electrode, taking lithium-rich organic electrolyte as electrolyte, and preferentially carrying out reduction reaction on H2 in a mixed atmosphere of D2 and H2 under the action of the catalyst under a continuous discharge condition to generate H <->; 2, under the continuous discharge condition, Li < + > ions in the electrolyte are combined with H <-> obtained through the reaction in the first step to generate LiH; step 3, collecting D2 gas which does not participate in the reaction; step 4, under a charging condition, decomposing the LiH prepared in the step 2 under the action of the catalyst to obtain H2 and Li < + > ions; and 5, collecting H2 prepared in the step 4 so as to realize separation of hydrogen isotopes. The hydrogen isotope can be efficiently separated at normal temperature and normal pressure, the process is simple, and energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical separation of hydrogen isotopes, and in particular to a method for separating hydrogen isotopes through charge and discharge cycles of a lithium-hydrogen battery. Background Art

[0002] Hydrogen isotopes, especially deuterium (D), have a wide range of application values ​​in modern industry, energy and nuclear energy. Deuterium is the main fuel for nuclear fusion reactors and plays an important role in technologies such as isotope tracing, neutron scattering and proton nuclear magnetic resonance spectroscopy. In view of the severity of the current global energy situation, nuclear fusion reactors are regarded as the energy system with the most development potential due to their high energy output and low environmental pollution. However, the utilization rate of deuterium fuel in nuclear fusion reactors is currently less than 10%, and most of the fuel is discharged without being consumed. In order to improve the economy and environmental safety of nuclear fusion reactors, it is particularly important to recover the fuel discharged from the plasma chamber that does not participate in nuclear fusion. The effective separation of hydrogen isotopes is the key technology in this process, but an effective method that meets industrial needs has not yet been found.

[0003] Deuterium is a stable isotope of hydrogen, and has extremely similar molecular shape, size and thermodynamic properties to hydrogen. Therefore, it is a challenging technology to separate, purify and concentrate single isotope gas from hydrogen isotope mixture. At present, the main industrial technologies for hydrogen isotope separation include cryogenic distillation technology and heavy water electrolysis technology. Cryogenic distillation technology uses the different boiling points of deuterium and hydrogen at around 20K to achieve separation. Heavy water electrolysis technology produces deuterium by electrolyzing heavy water, but due to the similarity between hydrogen isotopes, deuterium gas often contains a large amount of protium gas, which needs to be further separated and purified. In addition, the presence of water vapor may cause condensation and blockage of equipment, increasing the cost of equipment maintenance. Therefore, the current hydrogen isotope separation technology faces problems such as low separation temperature, complex processing equipment, low separation efficiency, and high energy consumption.

[0004] In summary, in order to meet the needs of industrial production, it is urgent to develop a new and efficient method for hydrogen isotope separation. So far, there has been no report on the method of separating hydrogen isotopes using the charge and discharge cycle of lithium-hydrogen batteries, which provides a new direction and possibility for future hydrogen isotope separation research. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for separating hydrogen isotopes, the method comprising the following steps:

[0006] In the first step, the catalyst is used as the positive electrode, the lithium metal is used as the negative electrode, and the lithium-rich organic electrolyte is used as the electrolyte. Under the condition of continuous discharge, the H2 in the mixed atmosphere of D2 and H2 is preferentially reduced under the action of the catalyst to generate H- ;

[0007] In the second step, under continuous discharge conditions, Li + ions react with the H - Combine to form LiH;

[0008] The third step is to collect the D2 gas that does not participate in the reaction;

[0009] In the fourth step, under charging conditions, the LiH prepared in the second step is decomposed under the action of the catalyst to obtain H2 and Li + ion;

[0010] The fifth step is to collect the H2 prepared in the fourth step, thereby achieving the separation of hydrogen isotopes (such as D2 and H2).

[0011] According to an embodiment of the present invention, the method is preferably carried out in an anhydrous and oxygen-free closed environment. Exemplarily, the method is carried out in an anhydrous and oxygen-free closed reaction tank.

[0012] According to an embodiment of the present invention, the anhydrous and oxygen-free environment refers to a water content of less than 0.1 ppm and an oxygen content of less than 0.1 ppm.

[0013] According to an embodiment of the present invention, the method can be carried out using a device known in the art, as long as it can provide the required potential, such as Figure 1 shown.

[0014] According to an embodiment of the present invention, in the first step, H - The reaction is shown in the following formula 1:

[0015]

[0016] According to an embodiment of the present invention, in the first step, the H - The preparation method specifically includes: in an environment without water and oxygen, using a catalyst as the positive electrode and lithium metal as the negative electrode, injecting a lithium-rich organic electrolyte, introducing a mixed gas of D2 and H2 into the positive electrode side, standing for a period of time, and discharging from an open circuit voltage to a low potential at a certain current density to generate H - .

[0017] According to an embodiment of the present invention, the open circuit voltage is, for example, not less than 0.8V.

[0018] According to an embodiment of the present invention, during discharge, the current density is 0.01-0.5 mA cm -2 , preferably 0.1-0.5 mA cm -2 .

[0019] According to an embodiment of the present invention, in the first step, the low potential refers to a discharge cut-off voltage of 0.1-0.5 V, preferably 0.2-0.4 V, for example 0.3 V. D2 is almost insoluble in the lithium-rich electrolyte, and controlling the discharge cut-off voltage within the range of the present invention can prevent deuterium from participating in the reaction, while hydrogen is completely reduced.

[0020] According to an embodiment of the present invention, in the first step, the continuous discharge time is 1 to 100 hours, preferably 10 to 50 hours.

[0021] According to the embodiment of the present invention, in the first step, the inventors found that when the discharge cut-off voltage is 0.2-0.4V and the discharge current density is 0.1-0.5mA cm -2 When the continuous discharge time is 10-50h, lithium metal and H2 form a Li-H2 battery, while D2 does not participate in the reaction.

[0022] According to an embodiment of the present invention, in the first step, the standing for a period of time refers to a standing time of 1-10 hours, illustratively, the standing time is 2 hours, 4 hours, 6 hours, 8 hours or 10 hours.

[0023] According to an embodiment of the present invention, a separator is further disposed between the positive electrode and the negative electrode. Preferably, the separator can be a separator known in the art, such as a polypropylene separator or a Celgard 2400 microporous membrane.

[0024] According to an embodiment of the present invention, the catalyst is selected from metal catalysts.

[0025] Preferably, the metal catalyst is selected from at least one of Au, Ru, Pd and Pt, preferably Ru. According to an embodiment of the present invention, the lithium-rich organic electrolyte comprises a lithium salt and an organic solvent.

[0026] According to an embodiment of the present invention, the concentration of lithium salt in the lithium-rich electrolyte is 0.1-2.0 mol L -1 , for example 0.5mol / L, 1mol / L, 1.5mol / L.

[0027] According to an embodiment of the present invention, the organic solvent is selected from at least one of propylene carbonate, ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate, cyclopentane, 1,3-dioxolane (DOL), ethylene glycol dimethyl ether (DME), and tetraethylene glycol dimethyl ether (TEGDME). Exemplarily, in the present invention, it is tetraethylene glycol dimethyl ether (TEGDME).

[0028] According to an embodiment of the present invention, the lithium salt may be an organic lithium salt and / or an inorganic lithium salt. Exemplarily, the lithium salt may be one or more combinations of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonyl imide, etc., preferably lithium bistrifluoromethanesulfonyl imide.

[0029] According to an embodiment of the present invention, the reaction in the second step is shown in Formula 2 below:

[0030] H - +Li + →LiH Formula 2;

[0031] According to an embodiment of the present invention, in the second step, the preparation method of LiH specifically comprises: after the first step is completed, in a closed environment without water and oxygen, Li and H - A chemical reaction occurs to generate LiH.

[0032] According to an embodiment of the present invention, in the second step, lithium metal and H2 constitute a Li-H2 battery.

[0033] According to an embodiment of the present invention, in the third step, the collecting refers to collecting the D2 gas that does not participate in the reaction into a container through a vacuum system, for example, a container known in the art such as a high-pressure cylinder.

[0034] According to an embodiment of the present invention, the vacuum system may be at least one of an oil pump and a molecular pump, preferably a molecular pump.

[0035] According to an embodiment of the present invention, in the third step, the vacuum system needs to make the closed environment reach a relatively high vacuum degree, for example, 1-100Pa. Exemplarily, the vacuum degree is 1Pa, 10Pa, 50Pa or 100Pa.

[0036] According to an embodiment of the present invention, in the fourth step, the reaction for generating H2 is shown in the following formula 3:

[0037]

[0038] According to an embodiment of the present invention, in the fourth step, the catalyst is the same as the catalyst described in the first step.

[0039] According to the embodiment of the present invention, in the fourth step, under charging conditions, the prepared LiH is charged from the open circuit voltage to a high potential at a certain current density, and the prepared LiH is decomposed under the action of the positive electrode catalyst to obtain H2 and Li + ion.

[0040] According to the embodiment of the present invention, during charging, the charging current density is 0.01-0.5 mA cm -2 , preferably 0.1-0.5 mA cm-2 , for example 0.2 mA cm -2 , 0.3 mA cm -2 , 0.4 mA cm -2 .

[0041] According to an embodiment of the present invention, in the fourth step, the high potential is 3.5-5V, preferably 3.5-4V.

[0042] According to an embodiment of the present invention, in the fifth step, the collecting refers to collecting the prepared H2 gas into a container through a vacuum system, for example, a container known in the art such as a high-pressure steel cylinder.

[0043] According to an embodiment of the present invention, in the fifth step, the vacuum system has the meaning as described above, and can be at least one of a vacuum oil pump and a molecular pump, preferably a molecular pump.

[0044] According to an embodiment of the present invention, in the fifth step, the vacuum system needs to make the closed environment reach a relatively high vacuum degree, for example, 1-100Pa. Exemplarily, the vacuum degree is 1Pa, 10Pa, 50Pa or 100Pa.

[0045] According to an exemplary embodiment of the present invention, the method for separating hydrogen isotopes comprises the following steps:

[0046] 1) In an environment without water and oxygen, the catalyst is used as the positive electrode and the lithium metal is used as the negative electrode. After injecting a lithium-rich organic electrolyte, a mixed gas of D2 and H2 is introduced into the positive electrode side. After standing for a period of time, the discharge cut-off voltage is 0.2-0.4V from the open circuit voltage at a certain current density. The lithium metal preferentially reacts with H2 to form a Li-H2 battery, and H2 is reduced to H under the action of the catalyst. - ion;

[0047] 2) H - Ions and Li in the electrolyte + The ions react chemically spontaneously to produce LiH on the positive electrode side;

[0048] 3) Use a molecular pump to collect the D2 that does not participate in the reaction into a high-pressure cylinder;

[0049] 4) Subsequently, under charging conditions, the catalyst is used as the positive electrode and the lithium metal is used as the negative electrode. During the process of charging from the open circuit voltage to a high potential of 3.5 to 4 V, the LiH obtained in step 2) is oxidized and decomposed under the action of the catalyst to obtain H2 and Li + ;

[0050] 5) The H2 generated in step 4) is collected in a high-pressure cylinder using a molecular pump, thereby achieving the separation of nitrogen isotopes D2 and H2.

[0051] Beneficial Effects of the Invention

[0052] 1. The present invention adopts a Li-H2 battery system, which can quickly and easily separate hydrogen isotopes by electrochemical hydrogen reduction under low potential conditions.

[0053] 2. The present invention selectively reduces H2 during the discharge process through the Li-H2 battery system and fixes it on the catalytic positive electrode in the form of LiH, and then decomposes LiH into H2 during the charging process, thereby realizing hydrogen isotope separation and catalyst recycling at room temperature and pressure.

[0054] 3. The present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic diagram of the Li-H2 battery device of the present invention.

[0056] Figure 2 The D2 content in the positive electrode chamber at the end of discharge of Example 1 and Comparative Examples 1-3, and the H2 content in the positive electrode chamber at the end of charge are shown. DETAILED DESCRIPTION

[0057] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0058] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0059] Experimental drugs and equipment: high-purity deuterium gas, high-purity hydrogen gas, hydrogen / deuterium mixed gas (the volume ratio of H2 and D2 is 70%:30%), Pt mesh, lithium foil, lithium-rich electrolyte, Celgard 2400 microporous membrane, electrochemical workstation CHI 660E (Shanghai Chenhua), Blue Electric Battery Testing System (CT 2001A).

[0060] Example 1

[0061] The method for electrochemical separation of hydrogen isotopes is as follows:

[0062] 1. The Li-H2 battery consists of a 1*1cm Ru mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is an organic mixed solution of 1M lithium bis(trifluoromethylsulfonyl)imide dissolved in tetraethylene glycol dimethyl ether (TEGDME);

[0063] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 hours, the open circuit voltage (0.8 V) increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0064] 3. The discharge lasts for 1-100 hours. During the discharge, the H2 / D2 content ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until the H2 in the positive electrode chamber is completely reduced and fixed on the positive electrode side. At this time, the D2 content in the gas in the positive electrode chamber is 98.9%;

[0065] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction from the reaction pool and collect it in a high-pressure cylinder;

[0066] 5. After the discharge is completed, the Li-H2 battery continues to increase from the open circuit voltage to 0.2 mA / cm 2 The battery was charged to 3.5 V with a current density of 1000 MHz. During this time, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the content of H2 in the gas in the positive electrode chamber reached 99.9%, charging was stopped.

[0067] 6. The H2 generated during the charging process is discharged from the positive electrode chamber by a molecular pump and collected in a high-pressure cylinder, thereby separating the hydrogen isotopes H2 and D2.

[0068] After separation by the above method, H2 (purity of 99.9%) and D2 (purity of 98.9%) are obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0069] In addition, the change of D2 content in the positive electrode compartment under different discharge cut-off voltage, current density, discharge time and other conditions was also studied during the discharge experiment. Specifically,

[0070] 1) Under the condition of constant current density and constant discharge time, the D2 content in the positive electrode compartment is different when the discharge is to different low potentials. -2 And keep the condition for 20h, discharge to different low potentials, the D2 content in the positive electrode chamber is shown in Table 1:

[0071] Table 1 D2 content in the positive electrode compartment when discharged to different low potentials

[0072] Voltage / V 0.7 0.5 0.3 0.2 0.1 <![CDATA[D2 content / %]]> 81.5 95.2 98.9 82.6 76.5

[0073] 2) Under the conditions of constant discharge voltage and constant discharge time, the D2 content in the positive electrode compartment is different with different discharge current densities. Under the conditions of discharge cut-off voltage of 0.3V and holding for 20h, the D2 content in the positive electrode compartment is shown in Table 2 when discharged at different current densities:

[0074] Table 2 D2 content in the positive electrode compartment at different discharge current densities

[0075] <![CDATA[Current density / mA cm -2 > 0.05 0.1 0.2 0.3 0.5 <![CDATA[D2 content / %]]> 78.9 85.6 98.9 96.5 88.5

[0076] 3) When the discharge current density is constant, the time the battery maintains at 0.5V is different, and the content of D2 in the positive electrode chamber is also different. -2 , the discharge time is different, and the content of D2 in the positive electrode chamber is shown in Table 3:

[0077] Table 3 D2 content in the positive electrode chamber at different discharge times

[0078] Discharge time / h 1 5 20 50 100 <![CDATA[D2 content / %]]> 60.5 72.6 98.9 85.6 58.6

[0079] Example 2

[0080] The method for electrochemical separation of hydrogen isotopes is as follows:

[0081] 1. The Li-H2 battery consists of a 1*1cm Pt mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is 1M lithium bis(trifluoromethylsulfonyl)imide dissolved in an organic mixed solution of tetraethylene glycol dimethyl ether (TEGDME).

[0082] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 hours, the open circuit voltage (0.8 V) increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0083] 3. The discharge lasts for 1-100 hours, during which the H2 / D2 ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until H2 is completely reduced and fixed on the positive electrode side; at this time, the D2 content in the gas in the positive electrode chamber is 98%;

[0084] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction in the Li-H2 battery from the reaction pool and collect it in a high-pressure cylinder;

[0085] 5. After the discharge is completed, the Li-H2 battery changes from an open circuit voltage of 0.2 mA cm -2The battery was charged to 3.5 V at a current density of 1000 MHz. During this time, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the H2 content in the gas in the positive electrode chamber reached 98.6%, charging was stopped.

[0086] 6. Use a molecular pump to discharge the H2 generated during the charging process from the positive electrode chamber and collect it in a high-pressure cylinder.

[0087] After separation by the above method, H2 (purity of 98.6%) and D2 (purity of 98%) are obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0088] Example 3

[0089] The method for electrochemical separation of hydrogen isotopes is as follows:

[0090] 1. The Li-H2 battery consists of a 1*1cm Pd mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is 1M lithium bis(trifluoromethylsulfonyl)imide dissolved in an organic mixed solution of tetraethylene glycol dimethyl ether (TEGDME).

[0091] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 h, the open circuit voltage (0.8 V) was increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0092] 3. The discharge lasts for 1-100 hours, during which the H2 / D2 ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until H2 is completely reduced and fixed on the positive electrode side; at this time, the D2 content in the gas in the positive electrode chamber is 97.2%;

[0093] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction in the Li-H2 battery from the reaction pool and collect it in a high-pressure cylinder;

[0094] 5. After the discharge is completed, the Li-H2 battery changes from an open circuit voltage of 0.2 mA / cm 2 The battery was charged to 3.5 V with a current density of 1000 MHz. During this time, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the H2 content in the gas in the positive electrode chamber reached 96.9%, charging was stopped.

[0095] 6. Use a molecular pump to discharge the H2 generated during the charging process from the positive electrode chamber and collect it in a high-pressure cylinder.

[0096] After separation by the above method, H2 (purity of 96.9%) and D2 (purity of 97.2%) were obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0097] Example 4

[0098] The method for electrochemical separation of hydrogen isotopes is as follows:

[0099] 1. The Li-H2 battery consists of a 1*1cm Au mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is 1M lithium bis(trifluoromethylsulfonyl)imide dissolved in an organic mixed solution of tetraethylene glycol dimethyl ether (TEGDME).

[0100] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 hours, the open circuit voltage (0.8 V) increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0101] 3. The discharge lasts for 1-100 hours, during which the H2 / D2 ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until H2 is completely reduced and fixed on the positive electrode side; at this time, the D2 content in the gas in the positive electrode chamber is 95.3%;

[0102] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction in the Li-H2 battery from the reaction pool and collect it in a high-pressure cylinder;

[0103] 5. After the discharge is completed, the Li-H2 battery changes from an open circuit voltage of 0.2 mA / cm 2 The battery was charged to 3.5 V with a current density of 1000 MHz. During this time, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the content of H2 in the gas in the positive electrode chamber reached 96.5%, charging was stopped.

[0104] 6. Use a molecular pump to discharge the H2 generated during the charging process from the positive electrode chamber and collect it in a high-pressure cylinder.

[0105] After separation by the above method, H2 (purity of 96.5%) and D2 (purity of 95.3%) were obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0106] Example 5

[0107] The method for electrochemical separation of hydrogen isotopes is as follows:

[0108] 1. The Li-H2 battery consists of a 1*1cm Ru mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is 1M lithium bis(trifluoromethylsulfonyl)imide dissolved in an organic mixed solution of 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) (volume ratio of 1:1).

[0109] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 hours, the open circuit voltage (0.8 V) increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0110] 3. The discharge lasts for 1-100 hours, during which the H2 / D2 ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until H2 is completely reduced and fixed on the positive electrode side; at this time, the D2 content in the gas in the positive electrode chamber is 98.6%;

[0111] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction in the Li-H2 battery from the reaction pool and collect it in a high-pressure cylinder;

[0112] 5. After the discharge is completed, the Li-H2 battery changes from an open circuit voltage of 0.2 mA cm -2 The battery was charged to 3.5 V at a current density of 1000 rpm. During this time, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the H2 content in the gas in the positive electrode chamber reached 92%, charging was stopped.

[0113] 6. Use a molecular pump to discharge the H2 generated during the charging process from the positive electrode chamber and collect it in a high-pressure cylinder.

[0114] After separation by the above method, H2 (purity of 92%) and D2 (purity of 98.6%) were obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0115] Example 6

[0116] The method for electrochemical separation of hydrogen isotopes is as follows:

[0117] 1. The Li-H2 battery consists of a 1*1cm Ru mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is 1M lithium bis(trifluoromethylsulfonyl)imide dissolved in an organic mixed solution of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) (volume ratio of 1:1:1).

[0118] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 hours, the open circuit voltage (0.8 V) increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0119] 3. The discharge lasts for 1-100 hours, during which the H2 / D2 ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until H2 is completely reduced and fixed on the positive electrode side; at this time, the D2 content in the gas in the positive electrode chamber is 98.3%;

[0120] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction in the Li-H2 battery from the reaction pool and collect it in a high-pressure cylinder;

[0121] 5. After the discharge is completed, the Li-H2 battery changes from an open circuit voltage of 0.2 mA / cm 2 The battery was charged to 3.5 V at a current density of 1000 Nm. During this period, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the H2 content in the gas in the positive electrode chamber reached 98.2%, charging was stopped.

[0122] 6. Use a molecular pump to discharge the H2 generated during the charging process from the positive electrode chamber and collect it in a high-pressure cylinder.

[0123] After separation by the above method, H2 (purity of 98.2%) and D2 (purity of 98.3%) are obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0124] Example 7

[0125] The method for electrochemical separation of hydrogen isotopes is as follows:

[0126] 1. The Li-H2 battery consists of a 1*1cm Ru mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is a 1M lithium trifluoromethanesulfonate dissolved in an organic mixed solution of tetraethylene glycol dimethyl ether (TEGDME).

[0127] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 hours, the open circuit voltage (0.8 V) increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0128] 3. The discharge lasts for 1-100 hours, during which the H2 / D2 ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until H2 is completely reduced and fixed on the positive electrode side; at this time, the D2 content in the gas in the positive electrode chamber is 89.6%;

[0129] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction in the Li-H2 battery from the reaction pool and collect it in a high-pressure cylinder;

[0130] 5. After the discharge is completed, the Li-H2 battery changes from an open circuit voltage of 0.2 mA cm -2 The battery was charged to 3.5 V at a current density of 1000 Nm. During this time, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the H2 content in the gas in the positive electrode chamber reached 91.3%, charging was stopped.

[0131] 6. Use a molecular pump to discharge the H2 generated during the charging process from the positive electrode chamber and collect it in a high-pressure cylinder.

[0132] After separation by the above method, H2 (purity of 91.3%) and D2 (purity of 89.6%) were obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0133] Example 8

[0134] The method for electrochemical separation of hydrogen isotopes is as follows:

[0135] 1. The Li-H2 battery consists of a 1*1cm Ru mesh as a catalyst and cathode current collector, a polypropylene separator (Celgard2400) and a lithium foil. The electrolyte is a 1M lithium tetrafluoroborate dissolved in an organic mixed solution of tetraethylene glycol dimethyl ether (TEGDME).

[0136] 2. In an environment without water and oxygen, H2 / D2 mixed gas was continuously introduced into the positive electrode at a flow rate of 10 sccm for 50 min (wherein the volume ratio of H2 to D2 was 70%:30%) to form a Li-H2 battery. After standing for 10 hours, the open circuit voltage (0.8 V) increased to 0.2 mA cm -2 The current density is discharged to 0.3V to generate lithium hydride (LiH);

[0137] 3. The discharge lasts for 1-100 hours, during which the H2 / D2 ratio of the mixed gas in the positive electrode chamber is detected by gas chromatography-mass spectrometry until H2 is completely reduced and fixed on the positive electrode side; at this time, the D2 content in the gas in the positive electrode chamber is 86.5%;

[0138] 4. Use a molecular pump to discharge the D2 that does not participate in the reaction in the Li-H2 battery from the reaction pool and collect it in a high-pressure cylinder;

[0139] 5. After the discharge is completed, the Li-H2 battery changes from an open circuit voltage of 0.2 mA cm -2 The battery was charged to 3.5 V at a current density of 1000 Nm. During this period, the concentration of H2 in the positive electrode chamber was detected by gas chromatography-mass spectrometry. When the H2 content in the gas in the positive electrode chamber was 87.3%, charging was stopped.

[0140] 6. Use a molecular pump to discharge the H2 generated during the charging process from the positive electrode chamber and collect it in a high-pressure cylinder.

[0141] After separation by the above method, H2 (purity of 87.3%) and D2 (purity of 86.5%) were obtained respectively. It can be seen that the method of the present invention can efficiently separate hydrogen isotopes at normal temperature and pressure, with a simple process and reduced energy consumption.

[0142] Comparative Example 1

[0143] The method for electrochemical separation of hydrogen isotopes is basically the same as that in Example 1, except that:

[0144] In step 2, the open circuit voltage (0.8 V) was increased to 0.2 mA cm -2 The current density was discharged to 0.05 V. At this time, when the gas in the positive electrode chamber was detected, it was found that the content of D2 was 76.5%.

[0145] It can be seen that when the discharge cut-off voltage is less than 0.1V, D2 participates in the reaction with Li + reaction.

[0146] Comparative Example 2

[0147] The method for electrochemical separation of hydrogen isotopes is basically the same as that in Example 1, except that:

[0148] In step 2, the Li-H2 battery is heated from an open circuit voltage of 0.6 mA cm -2 The current density was discharged to 0.3 V. At this time, the content of D2 in the positive electrode chamber was detected to be 72%.

[0149] It can be seen that when the discharge current density is greater than 0.5 mA cm -2 When H2 is not reduced or reduced incompletely.

[0150] Comparative Example 3

[0151] The method for electrochemical separation of hydrogen isotopes is basically the same as that in Example 1, except that:

[0152] In step 5, the Li-H2 battery is heated from an open circuit voltage of 0.2 mA cm -2 The current density was charged to 3 V. At this time, the H2 content in the positive electrode chamber was detected to be 70.5%.

[0153] It can be seen that when the charging voltage is less than 3.5V, LiH cannot be completely decomposed.

[0154] The above is a description of the exemplary embodiments of the present invention. However, the protection scope of the present application is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for separating hydrogen isotopes, characterized in that: The method comprises the following steps: In the first step, the catalyst is used as the positive electrode, the lithium metal is used as the negative electrode, and the lithium-rich organic electrolyte is used as the electrolyte. Under the condition of continuous discharge, the H2 in the mixed atmosphere of D2 and H2 is preferentially reduced under the action of the catalyst to generate H - ; In the second step, under continuous discharge conditions, Li + ions react with the H - Combine to form LiH; The third step is to collect the D2 gas that does not participate in the reaction; In the fourth step, under charging conditions, the LiH prepared in the second step is decomposed under the action of the catalyst to obtain H2 and Li + ion; The fifth step is to collect the H2 prepared in the fourth step to achieve the separation of hydrogen isotopes.

2. The method according to claim 1, characterized in that The method is carried out in a closed environment without water or oxygen; And / or, the anhydrous and oxygen-free environment refers to a water content of less than 0.1 ppm and an oxygen content of less than 0.1 ppm.

3. The method according to claim 1, characterized in that: In the first step, H is generated - The reaction is shown in the following formula 1: And / or, in the first step, the H - The preparation method specifically includes: in an environment without water and oxygen, using a catalyst as the positive electrode and lithium metal as the negative electrode, injecting a lithium-rich organic electrolyte, introducing a mixed gas of D2 and H2 into the positive electrode side, standing for a period of time, and discharging from an open circuit voltage to a low potential at a certain current density to generate H - .

4. The method according to claim 1, characterized in that: The open circuit voltage is, for example, not less than 0.8 V; And / or, during discharge, the current density is 0.01-0.5 mA cm -2 ; And / or, in the first step, the low potential refers to a discharge cut-off voltage of 0.1-0.5V; And / or, in the first step, the continuous discharge time is 1-100 hours; And / or, in the first step, the standing for a period of time refers to a standing time of 1-10 hours.

5. The method according to claim 1, characterized in that A separator is also arranged between the positive electrode and the negative electrode; And / or, the catalyst is selected from metal catalysts; And / or, the metal catalyst is selected from at least one of Au, Ru, Pd and Pt; And / or, the lithium-rich organic electrolyte comprises a lithium salt and an organic solvent.

6. The method according to claim 1, characterized in that The reaction in the second step is shown in the following formula 2: And / or, in the second step, the preparation method of LiH specifically comprises: after the first step is completed, in a closed environment without water and oxygen, Li and H - A chemical reaction occurs to generate LiH; And / or, in a second step, lithium metal and H2 form a Li-H2 battery.

7. The method according to claim 1, characterized in that In the third step, the collection refers to collecting the D2 gas that does not participate in the reaction into a container through a vacuum system, such as a container known in the art such as a high-pressure cylinder; And / or, in the third step, the vacuum system needs to make the closed environment reach a vacuum degree of 1-100Pa.

8. The method according to claim 1, characterized in that: In the fourth step, the reaction to generate H2 is shown in the following formula 3: In the fourth step, the catalyst is the same as that described in the first step.

9. The method according to claim 1, characterized in that: And / or, in the fourth step, under charging conditions, charging is performed from the open circuit voltage to a high potential at a certain current density, and the prepared LiH is decomposed under the action of the positive electrode catalyst to obtain H2 and Li + ion; and / or, during charging, the charging current density is 0.01-0.5 mA cm -2 ; And / or, in the fourth step, the high potential is 3.5-5V.

10. The method according to claim 1, characterized in that In the fifth step, the collecting means collecting the prepared H2 gas into a container through a vacuum system; And / or, in the fifth step, the vacuum system needs to make the closed environment reach a vacuum degree of 1-100Pa.

Images