A high-performance thermal battery positive electrode material and preparation method thereof

Abstract

This solution discloses a high-performance cathode material for thermal batteries in the field of thermal battery technology, specifically a ternary transition metal sulfide Ni x Fe y Co 1‑x‑y S2, where 0.5 ≤ x ≤ 0.8, 0 < y ≤ 0.3, and 0 < 1 - x - y ≤ 0.3. The cathode material has the comprehensive advantages of high capacity of NiS2, high potential of FeS2, high thermal stability and low internal resistance of CoS2, and has an obvious ternary synergistic effect. Among them, the resistivity is about 0.01 - 0.1 Ω·m; the discharge voltage reaches about 1.95 V; the discharge specific capacity reaches 1200 A·sg ‑1 (cut-off at a working voltage of 1.5 V), and it is an ideal cathode material for manufacturing high-specific-characteristic and large-capacity thermal batteries.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal batteries, and in particular relates to a high-performance thermal battery positive electrode material and a preparation method thereof. Background Art

[0002] Thermal batteries, or heat-activated batteries, are primary storage batteries that use molten salt as electrolyte and are activated by melting it with a heat source. Thermal batteries have the advantages of high specific energy and specific power, wide operating temperature range, long storage time, rapid and reliable activation, good mechanical properties, and no maintenance. They are ideal military power sources and are widely used as working power sources for military weapons such as artillery shells, missiles, underwater weapons, and nuclear weapons.

[0003] With the rapid development of high-tech national defense equipment, it requires supporting thermal batteries to have high specific energy characteristics, long working time and high ambient temperature resistance. High specific energy thermal batteries must be based on high-performance electrode materials. Compared with high-performance LiB alloy negative electrode materials, the current positive electrode materials have become the bottleneck restricting the improvement of thermal battery electrical performance. Traditional transition metal sulfide (such as FeS2, NiS2, CoS2) positive electrode materials can no longer meet the long-term working requirements of thermal batteries and the high specific energy output requirements at ultra-high ambient temperatures due to their limited specific capacity, poor thermal stability and low electrical conductivity.

[0004] CN 102339979 A discloses a method for preparing a thin-film positive electrode of a thermal battery, which can prepare positive electrode materials such as FeS2; CN102544482A discloses a formula of a positive electrode material of CoS2 for a thermal battery and its processing technology; CN 114349080 A discloses a nano nickel disulfide and its preparation method and application. Iron disulfide has a high potential, but a low decomposition temperature (550°C) and a large internal resistance, so it is not suitable for long-term working thermal batteries; cobalt disulfide has a high thermal decomposition temperature (650°C) and a small internal resistance, but its voltage and discharge capacity are not high, so it is not suitable for high specific energy thermal batteries; nickel disulfide has a high capacity, and its decomposition temperature, internal resistance and potential are between FeS2 and CoS2.

[0005] Therefore, how to produce a thermal battery positive electrode with high potential, high capacity, high thermal stability and high conductivity is an urgent problem to be solved. Summary of the invention

[0006] The present invention aims to provide a thermal battery positive electrode with high potential, high capacity, high thermal stability and high conductivity in view of the deficiencies in the prior art.

[0007] A high-performance thermal battery positive electrode material in this scheme, the high-performance thermal battery positive electrode material is a ternary transition metal sulfide Ni x Fe y Co 1-x-y S2; Nix Fe y Co 1-x-y S2 is a single-component compound, wherein 0.5≤x≤0.8, 0<y≤0.3, and 0<1-xy≤0.3.

[0008] Single-component compound: refers to a single material combination, with different elements bonded together by chemical bonds at a fixed molar ratio, which is a pure phase structure; it cannot be mixed with multiple phases, and only the ratio of various elements meets the requirements. XRD characterization must be a single material phase. Usually, the electrode potential and thermal stability of electrode active materials in different phases are different. Mixing electrode materials with different potential differences is not conducive to the battery to achieve high-voltage precision discharge. Therefore, the single component of the electrode active material is the key feature to achieve its high performance.

[0009] This program provides Ni x Fe y Co 1-x-y The S2 cathode material has the combined advantages of NiS2 high capacity, FeS2 high potential, and CoS2 high thermal stability and low internal resistance, and has an obvious ternary synergistic effect. Among them, the resistivity is about 0.01~0.1Ω·m; the discharge voltage reaches about 1.95V; the discharge specific capacity reaches 1200A·sg -1 (1.5V operating voltage cut-off), it is an ideal positive electrode material for manufacturing high-specificity and large-capacity thermal batteries, and has extremely high engineering application value.

[0010] The present invention also provides the high performance thermal battery positive electrode material Ni x Fe y Co 1-x-y The preparation method of S2 is to mix an iron source, a cobalt source and a nickel source in proportion to prepare a mixed ion solution, then add Na2S2O3·5H2O to react hydrothermally, and then remove sulfur by high-temperature sintering.

[0011] More specifically: the preparation method comprises the following steps:

[0012] (1) weighing raw materials of iron source, cobalt source and nickel source in proportion, and dissolving them in distilled water at room temperature to form a mixed ion solution;

[0013] (2) weighing Na2S2O3·5H2O, dissolving it in distilled water at room temperature, and then transferring it to the mixed ion solution prepared in step (1) and stirring it thoroughly;

[0014] (3) subjecting the solution in step (2) to a hydrothermal reaction, and washing and filtering the precipitate obtained by the reaction to obtain a precipitate;

[0015] (4) The precipitate obtained in step (3) is subjected to vacuum freeze drying to obtain Ni-containing Sx Fe y Co 1-x-y S2 dry powder;

[0016] (5) subjecting the S-containing powder obtained in step (4) to high-temperature desulfurization treatment under an inert protective atmosphere to finally obtain the ternary transition metal sulfide Ni x Fe y Co 1-x-y S2 powder.

[0017] The inert protective gas in the above step (5) can be any one of helium, argon, neon or nitrogen, or a combination of at least two of them.

[0018] Beneficial effects of vacuum freeze drying: In conventional vacuum drying processes, the temperature in the vacuum box is usually above 80°C, while Ni x Fe y Co 1-x-y The cobalt element in the S2 precipitate is easily oxidized and deformed to form cobalt sulfate under high temperature and humidity conditions, causing some electrode materials to denature and lose their electrochemical properties. Therefore, freeze-drying can avoid this problem.

[0019] Furthermore, in step (1), the iron source is preferably ferrous sulfate and / or ferrous chloride, the cobalt source is preferably cobalt sulfate and / or cobalt chloride, and the nickel source is preferably nickel sulfate and / or nickel chloride.

[0020] Furthermore, the amount of the precipitant Na2S2O3·5H2O used in step (2) is preferably 20wt% to 50wt% more than its theoretical amount.

[0021] The excess of 20 wt% of the precipitant is mainly to provide a more sufficient S source to ensure the completeness of the hydrothermal reaction.

[0022] Furthermore, the stirring time in step (2) is preferably 10 to 30 min, and the stirring rate is 100 to 260 r / min.

[0023] If the stirring rate is too low, the crystal nucleation is very uneven, and it is difficult to generate a single phase target compound during the hydrothermal reaction, usually a multiphase mixture; if the stirring rate is too high, the number of crystal nuclei is too large, the particle size of the product during the hydrothermal reaction is too fine, and the thermal stability is poor. The stirring rate in this scheme is the optimal rate screened after countless attempts.

[0024] Furthermore, in step (3), the hydrothermal reaction temperature is 160-200° C., the reaction pressure is not less than 2-4 MPa, and the reaction time is 3-6 h.

[0025] Furthermore, in step (3), the obtained precipitate is washed and filtered multiple times until no white precipitate is produced after an aqueous solution containing barium ions is added dropwise to the filtrate produced by filtration.

[0026] Sulfate ions SO4 in solution 2- Encountering barium ions Ba 2+ White precipitate barium sulfate will be generated immediately. No white precipitate is generated after adding barium ions to the filtrate, mainly to ensure that the precipitate is completely washed clean during hydrothermal treatment. Preparation of target material Ni x Fe y Co 1-x-y The raw materials of S2, such as ferrous sulfate, cobalt sulfate, and nickel sulfate, contain sulfate ions. If the target material Ni x Fe y Co 1-x-y S2 contains impurity sulfate ion SO4 2- , which will reduce the electrical properties of the material.

[0027] Furthermore, the freezing temperature of the vacuum freeze-drying treatment in step (4) is -40°C to -60°C, and the freeze-drying time is 12 to 24 hours.

[0028] Further, the desulfurization treatment in step (5) is: Ni containing S is removed under a protective atmosphere. x Fe y Co 1-x-y The S2 powder is kept at 400-500°C for 8-12 hours.

[0029] Keeping the temperature at 400℃~500℃ for 8~12h can, on the one hand, ensure the complete removal of excess impurity sulfur in the material, thereby limitedly improving the discharge voltage accuracy of the electrode material and the safety of the battery; on the other hand, long-term high-temperature treatment can further agglomerate and grow the target material particles generated by the hydrothermal reaction, thereby improving the thermal stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Ni obtained in Example 1 of the present invention 0.8 Fe 0.1 Co 0.1 XRD pattern of S2 cathode material;

[0031] Figure 2 Ni obtained in Example 1 of the present invention 0.8 Fe 0.1 Co 0.1 SEM image of S2 cathode material;

[0032] Figure 3 Ni obtained in Example 1 of the present invention 0.8 Fe 0.1 Co 0.1The electrical performance comparison curve of S2 positive electrode material and NiS2 positive electrode material, in which the negative electrode of the single cell is LiB alloy and the electrolyte is LiF-LiCl-LiBr ternary all-lithium electrolyte. DETAILED DESCRIPTION

[0033] The following is further described in detail through specific implementation methods:

[0034] Example 1, provides Ni 0.8 Fe 0.1 Co 0.1 The preparation method of the S2 positive electrode comprises the following steps:

[0035] (1) Weigh 25.6 g NiSO4·6H2O, 3.32 g FeCl3·6H2O and 3.42 g CoSO4·7H2O as initial raw materials, dissolve them in distilled water at room temperature and stir until they are completely dissolved;

[0036] (2) weighing 84.8 g of Na2S2O3·5H2O, dissolving it in distilled water at room temperature, then transferring it to the mixed metal ion solution prepared in step (1), and then stirring it thoroughly at a rate of 200 rad / min for 15 min;

[0037] (3) The solution of step (2) was transferred into a hydrothermal reactor, and the reaction time was 4 h at a temperature of 180°C. The reaction precipitate was then washed and filtered several times until the filtrate was dripped with Ba-containing 2+ Ions without white precipitate produced, precipitate obtained;

[0038] (4) The precipitate obtained in step (3) was subjected to vacuum freeze drying at -40°C for 24 hours to obtain Ni mixed with sulfur element 0.8 Fe 0.1 Co 0.1 S2 dry powder;

[0039] (5) The dried powder in step (4) was placed in an argon-protected box furnace and subjected to desulfurization treatment at 480°C for 12 h at a heating rate of 10°C / min to obtain pure Ni 0.8 Fe 0.1 Co 0.1 S2 positive electrode material.

[0040] Ni 0.8 Fe 0.1 Co 0.1 The X-ray diffraction (XRD) pattern of S2 powder is as follows Figure 1 As shown in the scanning electron microscope (SEM) image Figure 2 As shown, the electrical performance curve is as follows Figure 3 As shown. Figure 1 and Figure 2 It can be seen that the obtained product has a single phase and a particle size of 1 to 4 μm; the obtained Ni 0.8 Fe 0.1 Co 0.1 The resistivity of S2 powder is 0.03Ω·m, the discharge voltage is 1.95V, and the discharge capacity is 1200A·sg -1 (Cut off 1.5V operating voltage), with very excellent performance.

[0041] Example 2 provides Ni 0.5 Fe 0.25 Co 0.25 The preparation method of the S2 positive electrode comprises the following steps:

[0042] (1) Weigh 13.19 g NiSO4·6H2O, 6.76 g FeCl3·6H2O, and 7.03 g CoSO4·7H2O as initial raw materials, dissolve them in distilled water at room temperature and stir until they are completely dissolved;

[0043] (2) weighing 64.5 g of Na2S2O3·5H2O, dissolving it in distilled water at room temperature, then transferring it to the mixed metal ion solution prepared in step (1), and then stirring it thoroughly at a rate of 260 rad / min for 10 min;

[0044] (3) The solution of step (2) was transferred into a hydrothermal reactor, and the reaction time was 3 h at a temperature of 200 ° C. The reaction precipitate was then washed and filtered several times until the filtrate was dripped with Ba-containing 2+ Ions without white precipitate produced, precipitate obtained;

[0045] (4) The precipitate obtained in step (3) was subjected to vacuum freeze drying at -55°C for 12 h to obtain Ni mixed with sulfur element 0.5 Fe 0.25 Co 0.25 S2 dry powder;

[0046] (5) The dried powder in step (4) was placed in an argon-protected box furnace and subjected to desulfurization treatment at 450°C for 18 hours at a heating rate of 10°C / min to obtain pure Ni 0.5 Fe 0.25 Co 0.25 S2 positive electrode material.

Claims

1. A method for preparing a high-performance thermal battery positive electrode material, characterized in that: The high-performance thermal battery positive electrode material is a ternary transition metal sulfide Ni x Fe y Co 1-x-y S2; Ni x Fe y Co 1-x-y S2 is a single-component compound, wherein x=0.8, y=0.1; the high-performance thermal battery positive electrode material is prepared by the following steps: (1) weighing raw materials of iron source, cobalt source and nickel source in proportion, and dissolving them in distilled water at room temperature to form a mixed ion solution; (2) weighing Na2S2O3·5H2O, dissolving it in distilled water at room temperature, and then transferring it to the mixed ion solution prepared in step (1) and stirring it thoroughly; (3) subjecting the solution in step (2) to a hydrothermal reaction, washing and filtering the precipitate obtained by the reaction to obtain a precipitate; washing and filtering the precipitate obtained multiple times until no white precipitate is produced after adding a barium ion-containing aqueous solution to the filtrate produced by filtration; (4) The precipitate obtained in step (3) is subjected to vacuum freeze drying to obtain Ni-containing S x Fe y Co 1-x-y S2 drying powder; the freezing temperature of the vacuum freeze drying process is -40°C to -60°C, and the freeze drying time is 12 to 24 hours; (5) desulfurizing the S-containing powder obtained in step (4) under an inert protective atmosphere to finally obtain the ternary transition metal sulfide Ni x Fe y Co 1-x-y S2 powder.

2. The method for preparing a high-performance thermal battery positive electrode material according to claim 1, characterized in that: In step (1), the iron source is preferably ferrous sulfate and / or ferrous chloride, the cobalt source is preferably cobalt sulfate and / or cobalt chloride, and the nickel source is preferably nickel sulfate and / or nickel chloride.

3. The method for preparing a high-performance thermal battery positive electrode material according to claim 1, characterized in that: The amount of the precipitant Na2S2O3·5H2O used in step (2) exceeds its theoretical amount by 20wt% to 50wt%.

4. The method for preparing a high-performance thermal battery positive electrode material according to claim 1, characterized in that: The stirring time in step (2) is 10 to 30 minutes, and the stirring rate is 100 to 260 r / min.

5. The method for preparing a high-performance thermal battery positive electrode material according to claim 1, characterized in that: In step (3), the hydrothermal reaction temperature is 180-220° C., the reaction pressure is not less than 2-4 MPa, and the reaction time is 3-6 h.

6. A method for preparing a high-performance thermal battery positive electrode material according to any one of claims 1 to 5, characterized in that: The desulfurization treatment in step (5) is as follows: Ni containing S is removed under a protective atmosphere. x Fe y Co 1-x-y The S2 powder is kept at 400-500°C for 8-12 hours.

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