A high specific capacity composite cathode material with electrically conductive self-reinforcement for thermal batteries and a preparation method thereof

Abstract

The application belongs to the technical field of thermal batteries, and particularly relates to a conductive self-reinforced high specific capacity composite positive electrode material for thermal batteries and a preparation method thereof. The conductive self-reinforced high specific capacity composite positive electrode material contains the following components in percentage by weight: nickel-based oxide 24-40%, transition metal sulfide 40-56%, electrolyte 5-18%, lithiation agent 1-3%, and high-conductivity conductive agent 0.5-2%. In the scheme, the nickel-based oxide has a theoretical capacity of 2500 A.s or more, which is more than twice the capacity of the sulfide positive electrode material, and is immediately electrochemically reduced to nano nickel powder during discharge, thereby significantly improving the conductivity of the positive electrode material. Meanwhile, the high potential characteristics of the transition metal sulfide are utilized to effectively improve the working voltage. The scheme has significant advantages for high specific capacity and large current pulse type thermal batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal batteries, and in particular relates to a conductive self-reinforced high-capacity composite positive electrode material for thermal batteries and a preparation method thereof. Background Art

[0002] Thermal batteries, also known as heat-activated batteries, are primary storage batteries that use molten salt as an electrolyte and are activated by melting it with a heat source. They offer advantages such as high specific energy and power, a wide operating temperature range, long storage life, rapid and reliable activation, excellent mechanical properties, and a maintenance-free design. They are ideal military power sources and are widely used as power sources for artillery shells, missiles, and underwater weapons.

[0003] The rapid development of high-tech defense equipment requires supporting thermal batteries with high specific energy, long operating times, and resistance to high ambient temperatures. High-specific-energy thermal batteries must rely on high-performance electrode materials. Compared to high-performance LiB alloy anode materials, cathode materials have become a bottleneck restricting the improvement of thermal battery electrical performance.

[0004] Transition metal oxides typically possess high potentials and excellent thermal stability. Chromium oxides, vanadium oxides, and manganese oxides are the most widely studied cathode materials for thermal batteries. Compared to transition metal sulfides, which exhibit semiconductor properties, the covalent bond formed between oxygen and transition metals is much stronger than that between sulfur and oxygen. This results in extremely low electrical conductivity in transition metal oxides, making them unsuitable for high-power output applications.

[0005] Traditional transition metal sulfide cathode materials (such as FeS2, NiS2, and CoS2) are no longer able to meet the long-term operation requirements of thermal batteries and the high specific energy output at high ambient temperatures due to their limited specific capacity and poor thermal stability. For example, iron disulfide has a high potential, but a low decomposition temperature (550°C) and high internal resistance, making it unsuitable for long-term thermal batteries. Cobalt disulfide has a high thermal decomposition temperature (650°C), but its voltage and discharge capacity are not high, making it unsuitable for high-specific energy thermal batteries. Nickel disulfide has a decomposition temperature, internal resistance, and potential that are between those of FeS2 and CoS2. Furthermore, due to the strict voltage accuracy requirements of thermal batteries, transition metal sulfides typically only utilize the first stage of their electrochemical reduction process. The intermediate phase formed by the first-stage discharge platform reaction of transition metal sulfides is non-conductive or has very poor conductivity.

[0006] CN 102339979A discloses a preparation method of a thermal battery thin film positive electrode, which can prepare positive electrode materials such as FeS2; CN102544482A discloses a formula of a CoS2 positive electrode material of a thermal battery and a processing technology thereof; CN 114349080 A discloses a nano nickel disulfide and a preparation method and application thereof; CN 108039468 A discloses a composite positive electrode material suitable for long-time end-stage large-current discharge thermal batteries, that is, CoS2 and NiS2 are mixed in a certain proportion to exert the respective advantages of the two. However, in general, the above-mentioned patents cannot get rid of the performance defects of transition metal sulfides. Therefore, how to prepare a thermal battery positive electrode with high capacity, high thermal stability and high electrical conductivity is an urgent problem to be solved. SUMMARY

[0007] The present application aims to provide a conductive self-reinforced high specific capacity composite positive electrode material for thermal batteries, so as to significantly improve the specific capacity, electrical conductivity and thermal stability of the positive electrode material of the thermal battery.

[0008] The conductive self-reinforced high specific capacity composite positive electrode material for thermal batteries in the present application comprises components of nickel-based oxide, transition metal sulfide, electrolyte, lithiation agent and high electrical conductivity conductive agent.

[0009] Preferably, the weight percentage of each of the components is: nickel-based oxide 24% to 40%, transition metal sulfide 40% to 56%, electrolyte 5% to 18%, lithiation agent 1% to 3%, and high electrical conductivity conductive agent 0.5% to 2%.

[0010] The working principle and beneficial effects of the present application are as follows: the nickel-based oxide, as a transition metal oxide, has excellent thermal stability, a thermal decomposition temperature greater than 1000℃, and a theoretical capacity as high as 2500A·sg －1 Above all, it has significant advantages in terms of thermal stability and specific capacity characteristics. However, its defects are also very obvious, such as low lithium potential (about 1.45V) and poor self-conductivity. Therefore, for a long time, it has not been regarded by researchers as a positive electrode material with potential prospects for thermal batteries. The transition metal sulfide (such as FeS2, NiS2, CoS2) positive electrode material generally has good electrical conductivity and moderate potential (about 2.0V or so), but the thermal stability is relatively poor.

[0011] The conductive, self-reinforced, high-specific-capacity composite cathode material prepared by this invention, for the first time, discloses a method for preparing it using a nickel-based oxide composite transition metal sulfide architecture. This approach aims to leverage the high specific capacity and thermal stability of nickel-based oxides to enhance the specific capacity and thermal stability of thermal battery cathode materials, laying the foundation for high specific energy and long-term output. Furthermore, during discharge, the nickel-based oxide is immediately electrochemically reduced to nano-nickel powder, which spontaneously and significantly enhances the electronic conductivity of the composite cathode material. The combination of nickel-based oxide and transition metal sulfide achieves a perfect combination of the high conductivity of transition metal sulfide in the early stages of discharge and the high conductivity of nickel-based oxide in the middle and late stages of discharge. Finally, the high potential characteristics of transition metal sulfide completely alter the discharge voltage platform of nickel-based oxide. Ultimately, the prepared composite cathode combines the comprehensive properties of high specific capacity, high thermal stability, and high conductivity, while significantly reducing the amount of inactive materials (lithiation agents and electronic conductive agents) used in thermal battery cathode materials. This makes it an ideal cathode material for the development of thermal batteries with high specific energy, long-term, and high-power output.

[0012] The conductive self-enhanced high specific capacity composite positive electrode material provided by the present invention has an actual discharge specific capacity of up to 1500A·sg －1 Above, much higher than FeS2(1206A·sg －1 )、CoS2(1045A·sg －1 )’s theoretical specific capacity; at the same time, it has excellent high-power pulse carrying capacity and excellent resistance to high-temperature thermal decomposition.

[0013] Furthermore, the nickel-based oxide comprises components of nickel oxide NiO and defective nickel oxide Ni 1-X O, the nickel-based oxide is a powder with a particle size of 20um to 50um.

[0014] Furthermore, the transition metal sulfide is a mixture of one or more of FeS2, CoS2, and NiS2.

[0015] Furthermore, the electrolyte is selected from any one of LiCl-KCl, LiF-LiCl-LiBr, and LiCl-LiBr-KBr eutectic molten salts.

[0016] Furthermore, the lithiating agent is a mixture of one or more of lithium oxide and lithium sulfide.

[0017] Furthermore, the high-conductivity conductive agent is a mixture of one or more of carbon nanotubes, graphene, and conductive graphite.

[0018] At the same time, the present invention also provides a method for preparing the conductive self-reinforced high-specific-capacity composite positive electrode material for the thermal battery, which is specifically prepared according to the following steps:

[0019] Step one, water removal: nickel-based oxide, transition metal sulfide, electrolyte, lithiation agent, high conductivity conductive agent raw materials are respectively put into a vacuum drying oven at 80℃-200℃ to remove water for standby;

[0020] Step two, mixing: the nickel-based oxide, transition metal sulfide, electrolyte, and lithiation agent are weighed according to the proportions in claim 2 and mixed uniformly;

[0021] Step three, melting: the uniformly mixed material in step two is placed in an inert atmosphere protection sintering furnace or vacuum sintering furnace at 400℃-550℃ and sintered for 6h-12h. The electrolyte changes from solid to liquid, and the nickel-based oxide and transition metal sulfide are infiltrated and filled;

[0022] Step four, crushing: after the molten material in step three cools and solidifies, it is crushed and sieved to obtain a powder with a particle size of 80-200 mesh;

[0023] Step five, mixing the powder prepared in step four with the high conductivity conductive agent weighed according to the proportions in claim 2 to obtain the conductive self-reinforced high specific capacity composite positive electrode material for thermal batteries.

[0024] The above materials are obtained after experimental verification. The nickel-based oxide mainly provides high specific capacity, high thermal stability, and high conductivity in the middle / late stage of discharge, and the transition metal sulfide mainly maintains high voltage and high conductivity in the initial stage of discharge. The performance of the two is coordinated and unified. The proportion of nickel-based oxide and transition metal sulfide provided by the present application can be freely adjusted according to the discharge conditions to meet the power supply needs under different discharge conditions. The electrolyte uses LiCl-KCl, LiF-LiCl-LiBr, and LiCl-LiBr-KBr. The appropriate electrolyte is selected according to the specific power consumption conditions to improve its output characteristics. The electronic conductive agent includes carbon nanotubes, graphene, and conductive graphite, which are added in a small amount to improve the electronic conductivity of the positive electrode material in the initial stage of discharge.

[0025] Further, the planetary gravity dispersion machine is used for mixing in step two and step five, and the dispersion speed of the planetary gravity dispersion machine is 400r / min-1200r / min, and the dispersion time is 1min-3min.

[0026] Further, the inert gas in the inert atmosphere protection sintering in step three is high-purity argon, which is purified by removing water, and the water content is ≤50ppm. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Figure 1 is a discharge curve comparison diagram of the conductive self-reinforced high specific capacity composite positive electrode material for thermal batteries in embodiment one of the present application and the NiS2 positive electrode. DETAILED DESCRIPTION

[0028] The following is further described in detail through specific embodiments:

[0029] The following method embodiment prepares a high specific capacity composite positive electrode material for thermal batteries, which is mainly composed of nickel-based oxide, transition metal sulfide, electrolyte, lithiation agent and high conductivity conductive agent. The preparation method of the high specific capacity composite positive electrode material for thermal batteries is described in detail below in combination with the content of each component. The present application includes but is not limited to the following embodiments. The nickel-based oxide includes components of nickel oxide NiO and defect type nickel oxide Ni 1-X O, each component is a powder with a particle size of 20um-50um, and the percentage content of defect type nickel oxide Ni 1-X O in the nickel-based oxide is between 5% and 30%.

[0030] Example one

[0031] The preparation method of the high specific capacity composite positive electrode material for thermal batteries provided in this embodiment is as follows:

[0032] Step one. Water removal: Put the nickel-based oxide, NiS2, LiCl-KCl, lithium sulfide and carbon nanotubes into a vacuum drying oven at 170℃ for water removal;

[0033] Step two. Mixing: Add the nickel-based oxide, NiS2, LiCl-KCl and lithium sulfide according to a mass ratio of 24:56:17:2, and mix them uniformly in a planetary gravity disperser with a rotation speed of 900r / min for 1min;

[0034] Step three. Melting: Put the uniformly mixed material in step two into a sintering furnace at 500℃ under argon atmosphere protection for 8h, so that the electrolyte LiCl-KCl changes from solid state to liquid state, and the nickel oxide NiO / defect type nickel oxide Ni 1-X O and NiS2 of the thermal battery positive electrode active material are infiltrated and filled;

[0035] Step four. Crushing: After the molten material in step three cools and solidifies, use a crusher to crush the material and pass it through a 100 mesh sieve;

[0036] Step five. Add the powder prepared in step four and carbon nanotubes according to a mass ratio of 99:1, mix them uniformly in a planetary gravity disperser with a rotation speed of 600r / min for 2min, and obtain the high specific capacity composite positive electrode material for thermal batteries.

[0037] The present embodiment provides a discharge performance of a conductive self-reinforced high-specific-capacity composite positive electrode material for a thermal battery. Specifically, 2.5 g of the above-mentioned conductive self-reinforced high-specific-capacity composite positive electrode material is taken; in terms of weight percentage, the diaphragm is composed of LiF-LiCl-LiBr:MgO=50:50, with a mass of 1.8 g; the negative electrode is a 0.5 mm thick LiB alloy sheet, and the three are placed in a 48 mm diameter mold and punched into a sheet-shaped monomer with a total mass of 5.0 g. The single cell is placed in a thermal battery single cell test device, quickly heated to 500°C to make the single cell work at a constant temperature, discharged at a constant current of 5.4 A, and a pulse current of 36 A with a pulse width of 100 ms is loaded once at the 20th, 120th, 220th, and 320th seconds of the battery operation. The discharge curve of this embodiment is shown in the figure below. Figure 1 As shown (the positive electrode of the comparison battery is NiS2 positive electrode). Figure 1 It can be seen that when the cut-off voltage is 1.5V, the working time of the conductive self-enhanced high-specific-capacitance composite cathode material is 586s, and the working time of the NiS2 cathode is 340s. The working time of the conductive self-enhanced high-specific-capacitance composite cathode material is 1.7 times that of the NiS2 cathode, and the actual discharge capacity is as high as 1582A·sg －1 At the same time, the lowest voltage of the conductive self-enhanced high-capacitance composite cathode material under a large current pulse at 320s is still as high as 1.6V, while the corresponding pulse voltage of the NiS2 cathode is only 0.75V.

[0038] Example 2

[0039] This embodiment provides a method for preparing a conductive self-reinforced high-capacity composite positive electrode material for a thermal battery, specifically:

[0040] Step 1. Dehydration: Place nickel-based oxide, NiS2, LiCl-KCl, lithium sulfide, and carbon nanotubes in a vacuum drying oven at 170°C for dehydration.

[0041] Step 2. Mixing: Add nickel-based oxide, NiS2, LiCl-KCl, and lithium sulfide in a mass ratio of 32:48:17:2, and rotate in a planetary gravity disperser at a speed of 900 r / min for 1 minute to mix evenly.

[0042] Step 3. Melting: Place the mixed materials in step 2 in an argon atmosphere sintering furnace at 500℃ for 8 hours to change the electrolyte LiCl-KCl from solid to liquid, and heat the positive electrode active material nickel oxide NiO / defective nickel oxide Ni 1-X O and NiS2 are infiltrated and filled;

[0043] Step 4. Crushing: After the molten material in step 3 is cooled and solidified in the furnace, the material is crushed using a crusher and passed through a 100-mesh sieve;

[0044] Step 5. Add the powder prepared in step 4 and carbon nanotubes in a mass ratio of 99:1, rotate in a planetary gravity disperser at a speed of 600 r / min for 2 minutes and mix evenly to obtain the conductive self-reinforced high-specific-capacity composite positive electrode material for the thermal battery.

[0045] Example 3

[0046] This embodiment provides a method for preparing a conductive self-reinforced high-capacity composite positive electrode material for a thermal battery, specifically:

[0047] Step 1. Dehydration: Nickel oxide NiO / defective nickel oxide Ni 1-X O, NiS2, LiCl-KCl, lithium sulfide, and carbon nanotubes were placed in a vacuum drying oven at 170°C to remove water for later use;

[0048] Step 2. Mixing: Nickel oxide NiO / defective nickel oxide Ni 1-X O, NiS2, LiCl-KCl, and lithium sulfide were added in a mass ratio of 40:40:16:2 and mixed evenly in a planetary gravity disperser at a speed of 1000 r / min for 1 min.

[0049] Step 3. Melting: Place the mixed materials in step 2 in an argon atmosphere sintering furnace at 400℃ for 12 hours to change the electrolyte LiCl-KCl from solid to liquid, and heat the positive electrode active material nickel oxide NiO / defective nickel oxide Ni 1-X O and NiS2 are infiltrated and filled;

[0050] Step 4. Crushing: After the molten material in step 3 is cooled and solidified in the furnace, the material is crushed using a crusher and passed through a 100-mesh sieve;

[0051] Step 5. Add the powder prepared in step 4 and carbon nanotubes in a mass ratio of 98:2, rotate in a planetary gravity disperser at a speed of 400 r / min for 3 minutes and mix evenly to obtain a conductive self-reinforced high-specific-volume composite positive electrode material.

[0052] The present invention discloses a method for preparing a conductive self-reinforced high-specific-capacity composite positive electrode material for thermal batteries, which realizes the organic synergy of the high specific capacity, high thermal stability, and late-stage high conductivity characteristics of nickel-based oxides and the high potential and early-stage high conductivity characteristics of transition metal sulfides. The prepared composite positive electrode has comprehensive characteristics such as high specific capacity, high thermal stability, and high conductivity, and is an ideal positive electrode material for the development of high-specific-energy, long-term, and high-power output thermal batteries.

Claims

1. A conductive self-reinforced high-capacity composite positive electrode material for thermal batteries, characterized by: The positive electrode material includes components of nickel-based oxide, transition metal sulfide, electrolyte, lithiating agent and high conductivity conductive agent, wherein the nickel-based oxide, transition metal sulfide, electrolyte and lithiating agent are mixed and sintered in an inert atmosphere at 400-550°C, and the electrolyte changes from solid to liquid, and the nickel-based oxide and transition metal sulfide are infiltrated and filled; the nickel-based oxide includes components of nickel oxide NiO and defective nickel oxide Ni 1-X O, defective nickel oxide Ni 1-X The percentage of O in the nickel-based oxide is between 5% and 30%; the transition metal sulfide is a mixture of one or more of FeS2 and CoS2; and the high-conductivity conductive agent is a mixture of one or more of carbon nanotubes, graphene, and conductive graphite.

2. The conductive self-reinforced high specific capacity composite positive electrode material for thermal batteries according to claim 1, characterized in that: The weight percentages of the components are: nickel-based oxide 24% to 40%, transition metal sulfide 40% to 56%, electrolyte 5% to 18%, lithiating agent 1% to 3%, and high-conductivity conductive agent 0.5% to 2%.

3. The conductive self-reinforced high-capacity composite positive electrode material for a thermal battery according to claim 2, characterized in that: The nickel-based oxide is powder with a particle size of 20 μm to 50 μm.

4. The conductive self-reinforced high-capacity composite positive electrode material for a thermal battery according to claim 2, characterized in that: The electrolyte is selected from any one of LiCl-KCl, LiF-LiCl-LiBr, and LiCl-LiBr-KBr eutectic molten salts.

5. The conductive self-reinforced high-capacity composite positive electrode material for a thermal battery according to claim 2, characterized in that: The lithiating agent is a mixture of one or more of lithium oxide and lithium sulfide.

6. The method for preparing a conductive self-reinforced high-capacity composite positive electrode material for a thermal battery according to any one of claims 2 to 5, characterized in that: The preparation is carried out according to the following steps: Step 1: Dehydration: nickel-based oxide, transition metal sulfide, electrolyte, lithiating agent, and high-conductivity conductive agent are placed in a vacuum drying oven at 80°C to 200°C for dehydration. Step 2: Mixing: weighing the nickel-based oxide, transition metal sulfide, electrolyte, and lithiating agent according to the ratio in claim 2 and mixing them evenly; Step 3: Melting: Place the materials mixed in step 2 in an inert atmosphere protection sintering furnace or vacuum sintering furnace at 400°C to 550°C and sinter for 6 to 12 hours. The electrolyte changes from solid to liquid, and the nickel-based oxide and transition metal sulfide are infiltrated and filled. Step 4: Crushing: After the molten material in step 3 is cooled and solidified, crush it and sieve the powder through 80-200 mesh sieve; Step 5: Evenly mix the powder prepared in the fourth step and the high-conductivity conductive agent weighed in proportion as in claim 2 to obtain the conductive self-reinforced high-specific-capacity composite positive electrode material for the thermal battery.

7. The preparation method according to claim 6, characterized in that: In step 2 and step 5, a planetary gravity disperser is used for mixing operation. The dispersion speed of the planetary gravity disperser is 400 r / min to 1200 r / min, and the dispersion time is 1 min to 3 min.

8. The preparation method according to claim 6, characterized in that: The inert gas in the inert atmosphere protection sintering in step three is high-purity argon, and is purified by dehydration, with a water content of ≤50ppm.

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