A temperature-adjustable thermal battery electrolyte and its preparation method and application

Abstract

The present invention belongs to the field of electrochemistry, and specifically relates to a temperature-adjustable thermal battery electrolyte and a preparation method and application thereof. The present invention discloses a thermal battery electrolyte, which utilizes the phase change of a polymer or an organic matter to realize the activation of the thermal battery. Before the phase change, since the mixed system composed of a metal salt and a polymer is in a solid phase and has no ion conductivity, there is no ion path inside the battery, and the battery cannot realize discharge. After the phase change, the polymer or organic matter is in a molten state, and the metal salt dissolves therein to realize internal ion conduction, and the battery is activated to realize normal discharge.

Description

Technical Field

[0001] The invention belongs to the field of electrochemistry, and in particular relates to a temperature-adjustable thermal battery electrolyte and a preparation method and application thereof. Background Art

[0002] Thermal (heat-activated) batteries are an important type of reserve battery. When stored, the electrolyte is a non-conductive solid. When used, the heating agent inside is ignited, causing the electrolyte to melt and become an ion conductor and be activated. Thermal batteries have high specific energy and specific power, long storage time, and can work normally in various harsh environments. Therefore, they can be used as power sources in the fields of missiles and rockets, and are also widely used in non-military equipment such as aircraft emergency power supplies and underground high-temperature prospecting power supplies.

[0003] However, the melting point of the eutectic salt composed of common halide salts is relatively high, so that the activation temperature and operating temperature of the battery are mostly above 400°C. Such high activation temperature and operating temperature have many adverse effects on the cost, electrochemical performance and safety of the battery. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art, provide a temperature-adjustable thermal battery electrolyte and a preparation method and application thereof, and solve the problem of excessively high thermal activation temperature and operating temperature of thermal batteries in the prior art.

[0005] One of the technical solutions adopted by the present invention to solve its technical problems is to provide a temperature-adjustable thermal battery electrolyte: the electrolyte is a mixture of metal salts and polymers or organic matter; the polymers or organic matter are solid at room temperature and can be transformed from solid phase to liquid phase under heating conditions below 300°C; the metal salt is soluble in the polymers or organic matter in a molten state.

[0006] In a preferred embodiment, the mixture of the metal salt and the polymer or organic matter has no ionic conductivity in a solid state.

[0007] In a recommended embodiment, the metal salt is one of a lithium salt, a magnesium salt and a potassium salt.

[0008] In a recommended embodiment, the metal salt is one of LiCl, LiI, LiF, LiBr, LiNO3, LiClO4, LiTFSi, LiDFOB, LiPF6, LiBF4, LiAsF6, KF, KBr, KCl, KNO3, LiSbF6, LiCF3SO3, LiCF3CO2 and LiC2F4(SO3)2.

[0009] In a recommended embodiment, the polymer is one of PE (polyethylene), PP (polypropylene), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene, polyisobutylene, polyphosphate, polyvinyl chloride, polyimide, polyvinylidene chloride, polyethylene terephthalate (PET), polymethylpentene, polymethyl methacrylate, polyvinyl butyral (PVB), polyurethane (PU), and polyether sulfone.

[0010] In a recommended embodiment, the organic substance is one of vinyl acetate (EC), paraffin, and phenol.

[0011] A temperature-adjustable thermal battery comprises the thermal battery electrolyte described in any one of the above.

[0012] The second technical solution adopted by the present invention to solve the technical problem is to provide a method for preparing a temperature-adjustable thermal battery electrolyte, comprising the following steps:

[0013] (1) adding a metal salt to a molten polymer or organic matter, uniformly mixing the mixture, and cooling the mixture to obtain a mixture containing a metal salt;

[0014] (2) dissolving the mixture prepared above in an organic solvent or heating it to a molten state and placing it in a mold;

[0015] (3) After the mixture has been dissolved in step (2), the solvent is removed and then demolded to obtain a solid electrolyte membrane; after the mixture has been heated and melted in step (2), it is pressed into shape and then cooled and then demolded to obtain an electrolyte membrane.

[0016] In a recommended embodiment, the mold in step (2) is a polytetrafluoroethylene mold.

[0017] In a recommended embodiment, the compression molding in step (3) uses a pressure of 5-20 MPa.

[0018] The present invention has the following beneficial effects:

[0019] 1. At room temperature, the electrolyte is in a solid phase with no ionic conductivity, and the battery cannot self-discharge, which is beneficial to the storage of the battery; after heating, the polymer or organic matter changes from a solid phase to a liquid phase, and the metal salt dissolves in the molten polymer or organic matter, thereby realizing internal ion conduction, and the battery is activated to achieve normal discharge.

[0020] 2. The melting point of the polymer can be adjusted by the molecular weight, so the activation temperature of the thermally activated battery composed of the polymer electrolyte can be continuously adjusted;

[0021] 3. There are many types of polymers with melting points below 200°C. By replacing different types of polymers, the thermal battery can be activated at a lower temperature and the battery can be operated below 200°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the thermal activation mechanism of the electrolyte.

[0023] Figure 2 This is the thermal analysis diagram of PVDF in Example 8. DETAILED DESCRIPTION

[0024] The present invention will be described in more detail below by way of examples. In the following specific examples, a large number of specific details are given to facilitate a deeper understanding of the present invention, but the protection scope of the present invention is not limited to these examples.

[0025] Example 1

[0026] Preparation of temperature-adjustable heat-activated organic electrolyte for batteries: LiDFOB is added to molten PVDF and mixed evenly, and then cooled to obtain a LiDFOB / PVDF mixture with a concentration of 1 mol / L; 9 times the mass of solvent NMP (N-methylpyrrolidone) is added to the obtained mixture, and the mixture is dissolved in NMP. The obtained solution is poured into a square polytetrafluoroethylene mold, and then the mold is transferred to a vacuum oven at 80°C to remove NMP, and the electrolyte membrane is demolded to obtain the electrolyte membrane, and finally the electrolyte membrane is cut into the size for the battery.

[0027] Example 2

[0028] Preparation of temperature-adjustable heat-activated organic electrolyte for batteries: LiTFSi is added to molten PMMA and mixed evenly to obtain a LiTFSi / PMMA mixture with a concentration of 1 mol / l; 9 times the mass of acetone is added to the obtained mixture, and the obtained solution is cast in a square polytetrafluoroethylene mold, and then the mold is transferred to a vacuum oven at 80°C to remove the acetone, and the electrolyte membrane is demolded to obtain the electrolyte membrane, and finally the electrolyte membrane is cut into the size for the battery.

[0029] Example 3

[0030] Preparation of temperature-adjustable heat-activated organic electrolyte for batteries: Add LiTFSi into molten PE and mix evenly, cool to obtain a LiTFSi / PE mixture with a concentration of 1 mol / l for use; heat the mixture to 200°C and keep it warm to make the mixture molten, then pour the obtained molten mixture into a square polytetrafluoroethylene mold and press it into shape with a pressure of 10 MPa, demold it after cooling to obtain an electrolyte membrane, and finally cut the electrolyte membrane into the size for the battery.

[0031] Example 4

[0032] A conductivity test device is provided, wherein the electrolyte membrane obtained in Example 1 is sandwiched between two steel sheets, and the test device is placed in an oven, and the temperature is raised to 180°C at a rate of 5°C / min, and the conductivity of the new electrolyte system at different temperatures is tested, and the results are shown in Table 1. It can be seen from Table 1 that the conductivity is not measured from room temperature to 150°C, and when the temperature is raised to above the melting point of PVDF, PVDF undergoes a transition from a solid phase to a liquid phase to present a molten state, and LiDFOB dissolves in the molten PVDF, and the ionic conductivity is connected, so that the conductivity can be measured.

[0033] Table 1 Conductivity of electrolyte in Example 4 at different temperatures

[0034] Temperature(℃) 25 50 100 150 168 180 Voltage (V) 0.020 0.020 0.020 0.020 3.37 3.37

[0035] Example 5

[0036] A thermally activated battery, wherein the positive electrode material is mainly V2O5, the negative electrode material is mainly Li foil, and the electrolyte membrane prepared in Example 1 is placed between the positive electrode material and the negative electrode material. The battery is placed in an oven and heated to 200°C at 5°C / min and kept warm, and the open circuit voltage of the battery during the heating process is recorded with a multimeter. The results are shown in Table 2.

[0037] Table 2 Open circuit voltage of thermally activated battery at different temperatures in Example 5

[0038] Temperature(℃) 25 50 100 152 170 180 Voltage (V) 0.020 0.020 0.020 3.37 3.37 3.37

[0039] Example 6

[0040] A thermally activated battery, wherein the positive electrode material is mainly V2O5, the negative electrode material is mainly Li foil, and the electrolyte membrane prepared in Example 2 is placed between the positive electrode material and the negative electrode material. The battery is placed in an oven and heated to 200°C at 5°C / min, and the open circuit voltage of the battery during the heating process is recorded with a multimeter. The results are shown in Table 3.

[0041] Table 3 Open circuit voltage of thermally activated battery at different temperatures in Example 6

[0042] Temperature(℃) 25 50 100 152 170 180 Voltage (V) 0.020 0.020 0.020 3.37 3.37 3.37

[0043] Example 7

[0044] A thermally activated battery, wherein the positive electrode material is mainly V2O5, the negative electrode material is mainly Li foil, and the electrolyte membrane obtained in Example 3 is provided between the positive electrode material and the negative electrode material. The battery is placed in an oven and heated to 200°C at 5°C / min, and the open circuit voltage of the battery during the heating process is recorded with a multimeter. The results are shown in Table 4.

[0045] Table 4 Open circuit voltage of thermally activated battery at different temperatures in Example 7

[0046] Temperature(℃) 25 50 100 133 170 180 Voltage (V) 0.020 0.020 0.020 3.37 3.37 3.37

[0047] It can be seen from Tables 2, 3 and 4 that the above systems can achieve that the battery at room temperature does not display voltage in an unactivated state, and the battery is activated above the polymer phase change temperature and begins to display a normal voltage; and different systems have different activation temperatures, and the electrolyte activation temperature in the embodiments is all below 200°C.

[0048] Example 8

[0049] A thermally activated battery, wherein the positive electrode material is mainly FeS2, the negative electrode material is mainly Li(B) alloy, and the electrolyte membrane obtained in Example 1 is disposed between the positive electrode material and the negative electrode material. The battery is placed in an oven and heated to 140°C at 5°C / min, and the open circuit voltage of the battery is recorded with a multimeter during the heating process.

[0050] Example 9

[0051] The PVDF used in Example 1 was subjected to thermal analysis, and the results are as follows: Figure 2 As shown. Figure 2 From the thermal analysis diagram, it can be seen that the melting point (phase transition temperature) of PVDF is 159°C. It is in a non-ion-conducting solid state at room temperature and melts into a liquid state when the temperature is higher than the melting point.

[0052] Table 5 shows the melting point ranges of several polymers used to dissolve metal salts in the present invention. Different polymers have different melting points (phase transition temperatures). Therefore, the electrolyte system containing the polymer can flexibly adjust the activation temperature and operating temperature of the battery by changing the type of polymer.

[0053] Table 5 Melting point range of different polymers

[0054] Polymer Type PE PP PVDF PMMA PA PET Melting point(℃) 120-136 148-176 156-170 130-140 215-260 225-260

[0055] The above description is for illustrative purposes only and therefore cannot be used to limit the scope of implementation of the present invention. That is, any modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A temperature-adjustable thermal battery electrolyte, characterized in that: The electrolyte is a mixture of metal salt and polymer or organic matter; the polymer or organic matter is solid at room temperature and can be transformed from solid phase to liquid phase under heating conditions below 300°C; the metal salt is soluble in the polymer or organic matter in a molten state; the polymer is one of polyethylene, polypropylene, polyvinylidene fluoride, polyamide, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polyisobutylene, polyphosphate, polyvinyl chloride, polyimide, polyvinylidene chloride, polyethylene terephthalate, polymethylpentene, polymethyl methacrylate, polyvinyl butyral, polyurethane, and polyether sulfone; the organic matter is one of vinyl ester, paraffin, and phenol; the mixture of metal salt and polymer or organic matter has no ionic conductivity when in solid state.

2. A temperature-adjustable thermal battery electrolyte according to claim 1, characterized in that: The metal salt is one of lithium salt, magnesium salt and potassium salt.

3. A temperature-adjustable thermal battery electrolyte according to claim 1 or 2, characterized in that: The metal salt is one of LiCl, LiI, LiF, LiBr, LiNO3, LiClO4, LiTFSi, LiDFOB, LiPF6, LiBF4, LiAsF6, KF, KBr, KCl, KNO3, LiSbF6, LiCF3SO3, LiCF3CO2 and LiC2F4(SO3)2.

4. A temperature-adjustable thermal battery, comprising the thermal battery electrolyte according to any one of claims 1 to 3.

5. A method for preparing a temperature-adjustable thermal battery electrolyte according to any one of claims 1 to 3, characterized in that: The steps include: (1) dissolving a metal salt in a molten polymer or organic matter, and cooling the mixture to obtain a mixture containing a metal salt; (2) dissolving the mixture prepared above in an organic solvent or heating it to a molten state and placing it in a mold; (3) removing the solvent from the mixture after the dissolution treatment in step (2) and demolding to obtain a solid electrolyte; pressing the mixture after the heating and melting treatment in step (2) and demolding to obtain a solid electrolyte after cooling.

6. The method for preparing a temperature-adjustable thermal battery electrolyte according to claim 5, characterized in that: The mold in step (2) is a polytetrafluoroethylene mold.

7. The method for preparing a temperature-adjustable thermal battery electrolyte according to claim 5, characterized in that: The compression molding in step (3) adopts a pressure of 5-20MPa.

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