A cathode material with high interfacial wettability and its preparation method

Abstract

This invention relates to a high-interfacial-wetting cathode material and its preparation method in the field of thermal battery technology. The material comprises a cathode active material and a halide cathode additive, wherein the halide cathode additive accounts for 5% to 20% by mass. The cathode active material is a sulfide cathode, including one or more of FeS2, CoS2, and NiS2. The halide cathode additive is a metal halide, including one or more of nickel chloride, cobalt chloride, nickel fluoride, and copper fluoride. This solution significantly reduces the interfacial impedance between the cathode and the electrolyte, improving power performance and discharge capacity.

Description

Technical Field

[0001] This invention relates to the field of thermal battery technology, specifically to a cathode material with high interfacial wettability and its preparation method. Background Technology

[0002] With the rapid development of equipment upgrades and the aerospace field, thermal battery systems with long storage time, maintenance-free operation, and high-power discharge capability in harsh environments have become a key research focus in the military battery field, particularly for high-energy-density batteries. High-power-density thermal batteries are currently the core development direction. The negative electrode and electrolyte of thermal batteries can already meet the discharge requirements of new thermal batteries, while the positive electrode material is the main factor restricting the improvement of the discharge performance of thermal batteries.

[0003] Nickel chloride (NiCl2) is an ideal cathode material for thermal batteries due to its low cost, high theoretical capacity, high discharge current density, and high voltage plateau, and related research has been extensive. In the prior art, NiCl2 is disclosed in patent publication number CN107644985A. GlCs composite cathode materials utilize a molten salt method to lower the insertion reaction temperature, forming an electrolyte shell to slow down the dissolution of active materials. Patent CN107492633B discloses Rance Ni / NiCl2 composite cathode materials, prepared by calcination. However, pure NiCl2 has poor conductivity, a long activation time, and is prone to short circuits when dissolved in molten salt electrolytes, making direct engineering applications difficult.

[0004] Existing technologies for improving the wettability of the cathode and electrolyte have significant drawbacks. For example, patent CN116053472A uses anionic substitution to modify the cathode interface, but the thickness and ratio of the interface layer are difficult to control, and the preparation equipment is complex. In patent CN113130840A, insulating adsorbents such as MgO, MgF2, and Al2O3 are generated in situ on the cathode surface, reducing the cathode capacity, and the amount and location of the precipitate cannot be controlled. Patent CN117878325A uses oxygen-containing lithium salts to modify the sulfide cathode, but the addition of inactive materials reduces the capacity, and the effect of improving wettability is limited.

[0005] Conventional physical mixing methods cannot achieve a uniform microstructure distribution of sulfides and halides, easily leading to problems such as localized component excess, incomplete reactions, and halide melt overflow, resulting in degraded battery performance. Therefore, developing a sulfide-based composite cathode material with excellent interfacial wettability, structural stability, and simple preparation is crucial for promoting high specific energy... The development of high specific power thermal batteries is of great significance. Summary of the Invention

[0006] The present invention aims to provide a high-capacity, high-wetting thermal battery cathode material to solve the problem of weak interfacial wettability between the cathode and molten salt electrolyte in the prior art, so as to significantly reduce the interfacial impedance between the cathode and electrolyte and improve power performance and discharge capacity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a positive electrode material with high interfacial wettability, comprising: a positive electrode active material and a halide positive electrode additive, wherein the halide positive electrode additive accounts for 5% to 20% by mass percentage; The positive electrode active material is a sulfide positive electrode, which includes one or more of FeS2, CoS2, and NiS2. The halide cathode additive is a metal halide, which includes one or more of nickel chloride, cobalt chloride, nickel fluoride, and copper fluoride.

[0008] Preferably, as an improvement, the mass percentage of the halide cathode additive is 10% to 15%.

[0009] A method for preparing a cathode material with high interfacial wettability includes the following steps: S1, Solution preparation: Add the halide cathode additive to the organic solvent and stir to form a uniform halide solution; S2, Thorough mixing: While continuously stirring, add the positive electrode active material to the halide solution to ensure that the positive electrode active material and the halide solution are in full contact; S3, Solution Removal: Remove the organic solvent from the solution after thorough mixing in step S2 to obtain a primary composite powder in which halides are uniformly attached and covered on the surface or pores of the positive electrode active material. S4. The primary composite powder is heat-treated in an inert gas atmosphere at a temperature of 300~600℃, which is lower than the decomposition temperature of halides and sulfides, so that the positive electrode active material and halides form a dense layer, thereby anchoring and encapsulating the halides.

[0010] Preferably, as an improvement, the organic solvent in step S1 is anhydrous ethanol, acetone, isopropanone, or acetonitrile.

[0011] Preferably, as an improvement, the organic solvent removal method in step S3 is heating, rotary evaporation, or spray drying, with the rotary evaporation temperature being 40~60℃.

[0012] Preferably, as an improvement, heat treatment is performed in step S4 followed by vacuum drying, with a drying temperature of 100~150℃ and a drying time of 8~16 hours.

[0013] Preferably, as an improvement, cathode materials with high interfacial wettability are used in thermal batteries.

[0014] The advantages of this solution are: 1. This solution achieves molecular-level uniform composite of sulfide positive electrode active material and halide positive electrode additive through solution method, and uses low-temperature heat treatment to structurally encapsulate the halide, so that the positive electrode material has high wettability, high capacity and high structural stability, significantly improves the interfacial wettability between the positive electrode material and molten salt electrolyte, effectively reduces the interfacial impedance between the positive electrode and electrolyte, accelerates the ion and electron transport rate, shortens the thermal battery activation time, and improves the high-power discharge capability of the battery.

[0015] 2. This solution uses low-temperature heat treatment to form a dense coating layer between sulfides and halides, effectively anchoring and encapsulating the halide particles. This structurally suppresses the melting and overflow of halides when the battery is operating at high temperatures, preventing the collapse of the cathode material and short circuits inside the battery, and significantly improving the high-temperature no-load safety and operational stability of the thermal battery.

[0016] 3. This scheme synergistically combines highly stable sulfides with high-capacity halides with high discharge platform, without adding insulating inactive materials, and will not reduce the effective capacity of the cathode. It can fully utilize the electrochemical performance of the halide cathode while retaining the high specific energy advantage of the sulfide cathode, and achieve simultaneous improvement in the capacity and power performance of the cathode material.

[0017] 4. This scheme enables halides to be evenly distributed on the surface and in the pores of sulfides, allowing the discharge reaction of the cathode material to be more complete and uniform, optimizing the battery discharge platform, making the discharge voltage more stable and the voltage drop smaller, improving the depth of discharge and discharge efficiency, and improving the overall electrochemical performance of the thermal battery. Attached Figure Description

[0018] Figure 1 The figure shows a comparison curve of the high-temperature no-load discharge performance of the hot battery between the cathode material prepared in Example 1 of this invention and the comparative cathode material prepared using a conventional physical mixing process. Detailed Implementation

[0019] The following detailed description illustrates the specific implementation method: Example 1 A cathode material with high interfacial wettability is composed of a cathode active material and a halide cathode additive, wherein the halide cathode additive accounts for approximately 9% by mass percentage. The positive electrode active material is a sulfide positive electrode, and FeS2 is selected as the sulfide positive electrode.

[0020] The halide cathode additive is a metal halide, including nickel chloride.

[0021] Example 2 A cathode material with high interfacial wettability is composed of a cathode active material and a halide cathode additive, wherein the halide cathode additive accounts for 10% by mass percentage.

[0022] The positive electrode active material is a sulfide positive electrode, which comprises a mixture of FeS2 and CoS2 in a mass ratio of FeS2:CoS2 = 8:2. The halide cathode additive is a metal halide, which is a mixture of nickel chloride and nickel fluoride, with a mass ratio of nickel chloride to nickel fluoride of 1:1. Example 3 A cathode material with high interfacial wettability is composed of a cathode active material and a halide cathode additive, wherein the halide cathode additive accounts for 15% by mass percentage.

[0023] The positive electrode active material is a sulfide positive electrode, and the sulfide positive electrode is NiS2.

[0024] The halide cathode additive is a metal halide, which is a mixture of nickel fluoride and copper fluoride, with a mass ratio of nickel fluoride:copper fluoride = 7:3.

[0025] Example 4 A cathode material with high interfacial wettability is composed of a cathode active material and a halide cathode additive, wherein the halide cathode additive accounts for 20% by mass percentage.

[0026] The positive electrode active material is a sulfide positive electrode, which is a mixture of FeS2 and NiS2 in a mass ratio of FeS2∶NiS2=7∶3.

[0027] The halide cathode additive is a metal halide, and the metal halide is cobalt chloride.

[0028] Example 1 describes a method for preparing a cathode material with high interfacial wettability, comprising the following steps: A method for preparing a cathode material with high interfacial wettability includes the following steps: S1, Solution preparation: In a dry room with humidity less than 3%, add 15g of halide cathode additive to an organic solvent (anhydrous ethanol, acetone, isoacetone or acetonitrile) and stir to form a uniform halide solution. S2, Thorough mixing: While stirring continuously, add 150g of micron-sized positive electrode active material to the halide solution to ensure that the positive electrode active material and the halide solution are in full contact. S3, Solution Removal: Remove the organic solvent from the solution after thorough mixing in step S2 by heating, rotary evaporation or spray drying; when rotary evaporation is selected, rotate at 60 rpm in a 50°C water bath to slowly evaporate the organic solvent, and obtain a primary composite powder in which halides are uniformly attached and covered on the surface or in the pores of the positive electrode active material.

[0029] S4. The primary composite powder is subjected to low-temperature heat treatment in an inert gas atmosphere at a temperature of 300-600℃, which is lower than the decomposition temperature of halides and sulfides. This allows the positive electrode active material to form a dense layer with the halides, achieving anchoring and encapsulation of the halides. After the low-temperature heat treatment, vacuum drying is performed at a temperature of 100-150℃ for 8-16 hours.

[0030] As attached Figure 1 As shown, attached Figure 1 The figures show a comparison curve of the high-temperature no-load discharge performance of the cathode material prepared using Example 1 of the present invention and the comparative cathode material prepared using a conventional physical mixing process. As can be seen from the curves, under the same test conditions, the discharge voltage plateau of the example is significantly higher than that of the comparative example, and the voltage curve is more stable with less fluctuation. This indicates that the composite cathode material of the present invention has better interfacial wettability and electrochemical stability under high-temperature conditions, effectively reduces interfacial impedance, and achieves higher operating voltage and more stable discharge performance. This verifies the significant advantages of the present invention in improving the interfacial performance of cathode materials and the high-temperature discharge performance of hot batteries.

[0031] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A positive electrode material having high interfacial wettability, characterized by include: It consists of positive electrode active material and halide positive electrode additive, with the halide positive electrode additive accounting for 5%~20% by mass percentage; The positive electrode active material is a sulfide positive electrode, which includes one or more of FeS2, CoS2, and NiS2; the halide positive electrode additive is a metal halide, which includes one or more of nickel chloride, cobalt chloride, nickel fluoride, and copper fluoride.

2. The positive electrode material with high interfacial wettability according to claim 1, characterized in that: The mass percentage of the halide cathode additive is 10% to 15%.

3. The method of claim 1 or 2, wherein the method further comprises: adding a dispersant to the mixture of the lithium transition metal oxide and the solvent. Includes the following steps: S1, Solution preparation: Add the halide cathode additive to the organic solvent and stir to form a uniform halide solution; S2, Thorough mixing: While continuously stirring, add the positive electrode active material to the halide solution to ensure that the positive electrode active material and the halide solution are in full contact; S3, Solution Removal: Remove the organic solvent from the solution after thorough mixing in step S2 to obtain a primary composite powder in which halides are uniformly attached and covered on the surface or pores of the positive electrode active material. S4. The primary composite powder is heat-treated in an inert gas atmosphere at a temperature of 300~600℃, which is lower than the decomposition temperature of halides and sulfides, so that the positive electrode active material and halides form a dense layer, thereby anchoring and encapsulating the halides.

4. The method of claim 3, wherein the method further comprises: The organic solvent in step S1 is anhydrous ethanol, acetone, isopropanone, or acetonitrile.

5. The method for preparing a cathode material with high interfacial wettability according to claim 4, characterized in that: In step S3, the organic solvent is removed by heating, rotary evaporation, or spray drying, with the rotary evaporation temperature being 40~60℃.

6. The method for preparing a cathode material with high interfacial wettability according to claim 5, characterized in that: After heat treatment in step S4, vacuum drying is performed at a temperature of 100~150℃ for 8~16 hours.

7. The application of a cathode material with high interfacial wettability according to any one of claims 1 to 2 in a thermal battery.

Images