A high specific energy and high thermal stability cathode material for thermal batteries and its preparation method

Abstract

This solution discloses a high specific energy and high thermal stability cathode material for thermal batteries in the field of thermal battery technology, which is mainly prepared by mixing Ni-NiO, lithium sulfide, electrolyte and magnesium oxide. The Ni-NiO used in the present invention is a composite material obtained by calcining nickel powder in an oxygen atmosphere at 600-800 °C for 2-10 h and then cooling it by introducing nitrogen. Its thermal stability is greater than 1000 °C, with high thermal stability and high specific capacity, which can meet the requirements of high specific characteristics and long-time thermal batteries, and has the advantages of good electrochemical performance, high thermal stability, high safety, etc., and can be well matched with the thermal battery system. Mixing it with the other several components in the present invention and using it as the cathode material of the thermal battery, the capacity of the battery is increased by more than 100% compared with sulfides within the same voltage accuracy range.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal batteries, and particularly relates to a high specific energy and high thermal stability cathode material for thermal batteries and a preparation method thereof. Background Art

[0002] A thermal battery is a thermally activated reserve battery that relies on its own heating system to heat and melt a non-conductive solid-state salt electrolyte into an ionic conductor, thereby entering the working state. Thermal batteries have the characteristics of being activated at any angle, fast activation speed, long storage time, and strong ability to withstand environmental mechanical conditions, and have been widely used in weaponry. In addition, the application of thermal batteries in the civilian field has also received attention. At present, there have been research reports on their use as emergency power sources for aircraft, fire alarm power sources, and underground high-temperature prospecting power sources.

[0003] With the continuous development and update of military equipment, the requirements for the performance of thermal batteries are getting higher and higher. For example, it is required to have a longer working time, higher output power, more prominent high specific characteristics, and faster activation time. A thermal battery mainly consists of a substrate, a positive electrode sheet, a negative electrode sheet, an electrolyte sheet (or separator sheet), a sheet-shaped current collector, a heating system (an electric ignition head or a fire cap, ignition paper, a heating sheet), a heat-insulating gasket, a battery case, and a battery cover with a terminal. Among them, the electrode materials of the thermal battery have the most crucial influence on its electrochemical properties such as output capacity and working time. According to the working principle of the thermal battery, the thermal battery mainly relies on an automatic activation mechanism to ignite the heat source, melt and activate the electrolyte, and then enter the working state. Therefore, during the activation and working process of the thermal battery, it is necessary to keep the electrolyte in a molten state. The internal temperature of the battery reaches above 800 °C instantaneously during activation, which also causes some cathode materials to decompose, resulting in a certain degree of attenuation of the effective capacity and working time of the battery over a long period. Summary of the Invention

[0004] The present invention aims to overcome the deficiencies existing in the prior art and provides a high specific energy and high thermal stability cathode material, which has many advantages such as improving the high specific characteristics of the thermal battery and extending the working time of the battery.

[0005] A high specific energy and high thermal stability cathode material for a thermal battery in this solution is mainly prepared by mixing Ni-NiO, lithium sulfide, an electrolyte, and magnesium oxide. The Ni-NiO is obtained by calcining nickel powder in an oxygen atmosphere at 600-800 °C for 2-10 hours and then cooling it by introducing nitrogen.

[0006] Further, the weight ratios of Ni-NiO, lithium sulfide, the electrolyte, and magnesium oxide are respectively: 70%-95% of Ni-NiO, 0.1%-5% of lithium sulfide, 2%-15% of the electrolyte, and 3%-10% of magnesium oxide.

[0007] Further, the nickel powder is flaky, with a thickness of 1-5 μm, a thickness-to-diameter ratio of 10:1-30:1, and a purity > 99.5%.

[0008] Further, the lithium sulfide, electrolyte, and magnesium oxide are all powders with a particle size of 50 nm - 50 μm and a purity > 99.5%.

[0009] Further, the electrolyte is a LiCl-KCl eutectic salt.

[0010] The present invention also provides a method for preparing the high specific energy and high thermal stability cathode material for a thermal battery, comprising the following steps:

[0011] 1) First, dry the raw materials of lithium sulfide, electrolyte, and magnesium oxide under an inert atmosphere or vacuum condition at 40 - 300 °C for later use;

[0012] 2) Calcinate the nickel powder in an oxygen atmosphere at 600 - 800 °C for 2 - 10 h, and then introduce nitrogen to cool it to room temperature to obtain Ni-NiO;

[0013] 3) Weigh the Ni-NiO, lithium sulfide, electrolyte, and magnesium oxide materials processed in the above steps according to the weight ratio, mix them evenly, transfer them to an inert atmosphere or vacuum condition at 350 - 500 °C for drying and lithiation for 2 - 48 h, take out the sample and cool it, and use mechanical crushing and sieving to retain the powder with a mesh size of 60 - 200 for later use;

[0014] 4) Finally, transfer the powder to a vacuum condition and dry it at 175 - 200 °C.

[0015] Further, the drying temperature in step 1) is 175 - 200 °C; the calcination temperature in step 2) is 700 °C and the time is 4 h; the drying temperature in step 3) is 450 °C and the time is 8 h; the drying temperature in step 4) is 200 °C and the time is 6 h.

[0016] Further, retain the powder with a mesh size of 120 in step 3).

[0017] Preferably, the inert atmosphere in the present invention is one of argon and helium; the preparation process of all material tests is completed in a drying room with a humidity less than 3%.

[0018] The beneficial technical effects of the present invention are:

[0019] 1. The Ni-NiO used in the present invention is a composite material obtained by calcining nickel powder in an oxygen atmosphere at 600-800 °C for 2-10 h and then cooling it by introducing nitrogen. Its thermal stability is greater than 1000 °C, and it has high thermal stability and high specific capacity, meeting the requirements of high specific characteristics and long-time thermal batteries. It has the advantages of good electrochemical performance, high thermal stability, and high safety, and can be well matched with the thermal battery system. When it is mixed with several other components in the present invention and used as the positive electrode material of the thermal battery, the capacity of the battery is increased by more than 100% compared with sulfide within the same voltage accuracy range.

[0020] 2. Nickel raw materials are easily obtained and are more economical in price compared with sulfides.

[0021] 3. Compared with conventional positive electrode materials, the reaction product of Ni-NiO in the present invention is metallic nickel with good conductivity, which can improve the power performance of long-time thermal batteries in the later stage; Ni-NiO has a high theoretical specific capacity, which can improve the specific energy of the battery; the thermal stability of Ni-NiO is greater than 1000 °C, while that of sulfide positive electrode materials is about 600 °C. Ni-NiO is suitable for long-time working thermal batteries, and at the same time has high safety and good thermal stability. The discharge time reaches twice that of sulfide positive electrodes within a limited voltage accuracy range. Description of the Drawings

[0022] Figure 1 : Discharge comparison between the high specific energy and high thermal stability positive electrode material of Example 1 and the conventional sulfide positive electrode material;

[0023] Figure 2 : Physical picture of the high specific energy and high thermal stability positive electrode material of Example 1;

[0024] Figure 3 : Discharge comparison of the high specific energy and high thermal stability positive electrode materials of Example 1, Example 2, Example 3, Example 4, and Example 5. Detailed Embodiments

[0025] The following is a further detailed description through specific embodiments:

[0026] Example 1. A preparation method of a high specific energy and high thermal stability positive electrode material for a thermal battery, comprising the following steps:

[0027] 1) First, put lithium sulfide, electrolyte, and magnesium oxide raw materials into an inert drying oven or a vacuum drying oven at 175 °C to remove water for standby;

[0028] 2) Put flaky nickel powder into a muffle furnace and calcine it at 700 °C for 4 h in an oxygen atmosphere, and then cool it to room temperature by introducing nitrogen to obtain Ni-NiO;

[0029] 3) Weigh 200 g of Ni-NiO, 2 g of lithium sulfide, 20 g of LiCl-KCl eutectic salt, and 10 g of magnesium oxide separately, put them into a high-speed powder mixer and mix evenly. Then transfer them to an inert drying oven at 450 °C for 8 h. Take out the sample and cool it, and then use mechanical crushing and screen it through a 120-mesh sieve to prepare the Ni-NiO composite cathode material;

[0030] 4) Finally, dry the powder prepared in the third step in a vacuum drying oven at 200 °C for 6 hours.

[0031] The inert gas is one of argon and helium; the synthesis process of all material tests is completed in a drying room with a humidity less than 3%.

[0032] Example 2. A preparation method of a high specific energy and high thermal stability cathode material for thermal batteries, comprising the following steps:

[0033] 1) First, put the raw materials of lithium sulfide, electrolyte, and magnesium oxide into an inert drying oven or a vacuum drying oven at 175 °C to remove water for standby;

[0034] 2) Put the flaky nickel powder into a muffle furnace and calcine it at 600 °C for 4 h in an oxygen atmosphere, and then introduce nitrogen to cool it to room temperature to obtain Ni-NiO;

[0035] 3) Weigh 200 g of Ni-NiO, 5 g of lithium sulfide, 10 g of LiCl-KCl eutectic salt, and 20 g of magnesium oxide separately, put them into a high-speed powder mixer and mix evenly. Then transfer them to an inert drying oven at 450 °C for 8 h. Take out the sample and cool it, and then use mechanical crushing and screen it through a 120-mesh sieve to prepare the Ni-NiO composite cathode material;

[0036] 4) Finally, dry the powder prepared in the third step in a vacuum drying oven at 200 °C for 6 hours.

[0037] The inert gas is one of argon and helium; the synthesis process of all material tests is completed in a drying room with a humidity less than 3%.

[0038] Example 3. A preparation method of a high specific energy and high thermal stability cathode material for thermal batteries, comprising the following steps:

[0039] 1) First, put the raw materials of lithium sulfide, electrolyte, and magnesium oxide into an inert drying oven or a vacuum drying oven at 175 °C to remove water for standby;

[0040] 2) Put the flaky nickel powder into a muffle furnace and calcine it at 700 °C for 4 h in an oxygen atmosphere, and then introduce nitrogen to cool it to room temperature to obtain Ni-NiO;

[0041] 3) Weigh 200 g of Ni-NiO, 4 g of lithium sulfide, 5 g of LiCl-KCl eutectic salt, and 20 g of magnesium oxide separately, put them into a high-speed powder mixer and mix evenly. Then transfer them to an inert drying oven at 450 °C for 8 h. Take out the sample and cool it. Use mechanical crushing and screen it through a 120-mesh sieve to prepare the Ni-NiO composite cathode material;

[0042] 4) Finally, dry the powder prepared in the third step in a vacuum drying oven at 200 °C for 6 hours.

[0043] The inert gas is one of argon and helium; the synthesis process of all material tests is completed in a drying room with a humidity less than 3%.

[0044] Example 4. A preparation method of a high specific energy and high thermal stability cathode material for thermal batteries, comprising the following steps:

[0045] 1) First, put the raw materials of lithium sulfide, electrolyte, and magnesium oxide into an inert drying oven or a vacuum drying oven at 175 °C to remove water for standby;

[0046] 2) Put the flaky nickel powder into a muffle furnace and calcine it at 700 °C for 4 h in an oxygen atmosphere. Then introduce nitrogen gas to cool it to room temperature to obtain Ni-NiO;

[0047] 3) Weigh 200 g of Ni-NiO, 4 g of lithium sulfide, 15 g of LiCl-KCl eutectic salt, and 15 g of magnesium oxide separately, put them into a high-speed powder mixer and mix evenly. Then transfer them to an inert drying oven at 450 °C for 8 h. Take out the sample and cool it. Use mechanical crushing and screen it through a 120-mesh sieve to prepare the Ni-NiO composite cathode material;

[0048] 4) Finally, dry the powder prepared in the third step in a vacuum drying oven at 200 °C for 6 hours.

[0049] Example 5. A preparation method of a high specific energy and high thermal stability cathode material for thermal batteries, comprising the following steps:

[0050] 1) First, put the raw materials of lithium sulfide, electrolyte, and magnesium oxide into an inert drying oven or a vacuum drying oven at 175 °C to remove water for standby;

[0051] 2) Put the flaky nickel powder into a muffle furnace and calcine it at 700 °C for 4 h in an oxygen atmosphere. Then introduce nitrogen gas to cool it to room temperature to obtain Ni-NiO;

[0052] 3) Weigh 200 g of Ni-NiO, 4 g of lithium sulfide, 16 g of LiCl-KCl eutectic salt, and 20 g of magnesium oxide and put them into a high-speed powder mixer and mix evenly. Then transfer them to an inert drying oven at 450 °C for 8 h. Take out the sample and cool it. Use mechanical crushing and screen it through a 120-mesh sieve to prepare the Ni-NiO composite cathode material;

[0053] 4) Finally, the powder prepared in the third step is dried in a vacuum drying oven at 200 °C for 6 hours. Composite cathode material

[0054] Comparative example: Conventional sulfide cathode material: Fe-Co-S2 composite cathode material.

[0055] Test example 1

[0056] The physical states of the high specific energy and high thermal stability cathode materials prepared by the method of the present invention are the same as those in Example 1. For the prepared high specific energy and high thermal stability cathode materials, high specific energy and high thermal stability cathode materials are prepared according to Example 1, Example 2, Example 3, Example 4, Example 5 and the comparative example. At the same time, the high specific energy and high thermal stability cathode materials are pressed into sheets and assembled into 16 single-cell series unit cells for electrical performance testing. The comparative test results between Example 1 and the comparative example are as Figure 1 and Figure 3 shown. From the figure, the unit thermal battery has less thermal shock, good thermal stability, a stable discharge platform, excellent discharge performance, and the discharge time reaches twice that of the sulfide cathode within the limited voltage accuracy range; the effective capacity of the battery is increased by more than 100% compared with the capacity of the sulfide cathode material.

Claims

1. A high specific energy and high thermal stability cathode material for thermal batteries, characterized in that: It is mainly obtained by processing Ni-NiO, lithium sulfide, electrolyte and magnesium oxide according to the following preparation method. The Ni-NiO is obtained by calcining nickel powder in an oxygen atmosphere at 600-800 °C for 2-10 h and then cooling it by introducing nitrogen. The weight ratios of Ni-NiO, lithium sulfide, electrolyte and magnesium oxide are respectively: 70%-95% of Ni-NiO, 0.1%-5% of lithium sulfide, 2%-15% of electrolyte, and 3%-10% of magnesium oxide. The preparation method includes the following steps: 1) First, dry the raw materials of lithium sulfide, electrolyte and magnesium oxide in an inert atmosphere or under vacuum at 40-300 °C for later use; 2) Calcine the nickel powder in an oxygen atmosphere at 600-800 °C for 2-10 h, and then cool it to room temperature by introducing nitrogen to obtain Ni-NiO; 3) Weigh the Ni-NiO, lithium sulfide, electrolyte and magnesium oxide materials treated in the above steps according to the weight ratio, mix them evenly, transfer them to an inert atmosphere or under vacuum at 350-500 °C for drying and lithiation for 2-48 h, take out the sample and cool it, use mechanical crushing and sieving, and retain the powder with a mesh size of 60-200 for later use; 4) Finally, dry the powder under vacuum at 175-200 °C.

2. The high specific energy and high thermal stability cathode material for thermal battery according to claim 1, wherein: The nickel powder is flaky, with a thickness of 1-5 μm, a thickness-to-diameter ratio of 10:1-30:1, and a purity > 99.5%.

3. The high specific energy and high thermal stability cathode material for thermal battery according to claim 2, wherein: The lithium sulfide, electrolyte and magnesium oxide are all powders with a particle size of 50 nm-50 μm and a purity > 99.5%.

4. A high specific energy and high thermal stability cathode material for thermal batteries according to any one of claims 1 to 3, characterized in that: The electrolyte is a LiCl-KCl eutectic salt.

5. The preparation method of a high specific energy and high thermal stability cathode material for a thermal battery according to claim 4, characterized in that, It includes the following steps: 1) First, dry the raw materials of lithium sulfide, electrolyte and magnesium oxide in an inert atmosphere or under vacuum at 40-300 °C for later use; 2) Calcine the nickel powder in an oxygen atmosphere at 600-800 °C for 2-10 h, and then cool it to room temperature by introducing nitrogen to obtain Ni-NiO; 3) Weigh the Ni-NiO, lithium sulfide, electrolyte and magnesium oxide materials treated in the above steps according to the weight ratio, mix them evenly, transfer them to an inert atmosphere or under vacuum at 350-500 °C for drying and lithiation for 2-48 h, take out the sample and cool it, use mechanical crushing and sieving, and retain the powder with a mesh size of 60-200 for later use; 4) Finally, dry the powder under vacuum at 175-200 °C.

6. The preparation method of a high specific energy and high thermal stability cathode material for a thermal battery according to claim 5, characterized in that: The drying temperature in 1) is 175-200 °C; the calcination temperature in 2) is 700 °C and the time is 4 h; the drying temperature in 3) is 450 °C and the time is 8 h; the drying temperature in 4) is 200 °C and the time is 6 h.

7. The preparation method of a high specific energy and high thermal stability cathode material for a thermal battery according to claim 6, wherein: Retain the powder with a mesh size of 120 in 3).

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