Thermal battery composite positive electrode material with high utilization rate and preparation method thereof

Abstract

The invention provides a high-utilization-rate thermal battery composite positive electrode material and a preparation method thereof, and solves the technical problems that an existing thermal battery positive electrode material is low in utilization rate, unbalanced in positive and negative electrode capacity ratio and the like and restricts the development of a thermal battery. The composite positive electrode material comprises two sulfide active positive electrode materials FeS2 and CoS2, lithium silicon alloy powder, lithium oxide and an ionic conductive agent, the mass percent of the active positive electrode materials is 30%-90%, the mass percent of the ionic conductive agent is 10%-50%, the mass percent of the lithium silicon alloy powder is 1%-20%, the mass percent of the lithium oxide is 1%-30%, and the ionic conductive agent is at least one eutectic salt of LiCl-LiBr-KBr, LiCl-LiBr-LiF and LiCl-KCl. The preparation method comprises the following steps: (1) carrying out high-energy ball milling on the active positive electrode material for a certain time to obtain undersize powder with different mesh numbers; (2) performing high-temperature treatment on the screen underflow powder to obtain activated positive electrode powder; and (3) uniformly mixing the positive electrode powder subjected to high-temperature treatment, lithium silicon alloy powder, an ionic conductive agent and lithium oxide, and performing lithiation, sieving and drying treatment to obtain the thermal battery composite positive electrode powder.

Description

Technical Field

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

[0002] Thermal batteries are one-time, irreversible chemical power sources that feature molten salt materials as electrolytes. Under normal temperature storage, the electrolyte is a non-conductive solid inorganic salt, which melts at high temperatures and turns into a liquid with high ionic conductivity, thereby activating the battery. Thermal batteries have low internal resistance, a wide operating temperature range, long storage time, rapid and reliable activation, and require no maintenance. They have developed into an ideal power source for modern weapons.

[0003] At present, the mainstream positive electrode material of thermal batteries is FeS 2 and CoS 2 Transition metal sulfides, such as CoS, are an important component of thermal batteries and account for a large proportion of electrode materials. Therefore, the performance of the positive electrode material largely determines the performance of thermal batteries. However, the current utilization rate of sulfide positive electrode materials is too low, which affects its development of the thermal battery market. First, CoS 2 The raw materials are artificially synthesized, the particle size is small and the growth is uniform, but the starting voltage is low and the price is expensive. 2 The raw materials can only be extracted from pyrite, and the particle size is large and the distribution is uneven, which will increase the porosity of the active material in the electrode and make some FeS 2 The particles cannot contact with other particles well, and the electrode cannot fully react with the electrolyte layer contact interface, resulting in an increase in the internal resistance of the battery and a decrease in the utilization rate of the positive electrode material. Secondly, the reasonable capacity ratio of the positive and negative electrode materials of the thermal battery is very important. The excessive sulfur vapor produced by the positive electrode will cause serious thermal runaway when it is out of control, and even short-circuit combustion and explosion. Excessive negative electrode will also consume lithium in the positive electrode, reduce the battery energy density, and increase the battery cost. Therefore, improving the utilization rate of the positive electrode material is particularly important for improving the performance of thermal batteries and developing the thermal battery market. Summary of the invention

[0004] The present invention proposes a high-utilization thermal battery composite positive electrode material and a preparation method thereof, aiming to overcome the deficiencies of the prior art and solve the technical problems that restrict the development of thermal batteries, such as low utilization of thermal battery positive electrode materials and unbalanced ratio of positive and negative electrode capacities.

[0005] The present invention is achieved by the following technical solutions:

[0006] A high-utilization thermal battery composite positive electrode material, comprising FeS 2 and CoS 2Two sulfide active positive electrode materials, lithium silicon alloy powder, lithium oxide and ion conductive agent, wherein the mass percentages are: 30% to 90% active positive electrode material, 10% to 50% ion conductive agent, 1% to 20% lithium silicon alloy powder, 1% to 30% lithium oxide, and the ion conductive agent is at least one eutectic salt of LiCl-LiBr-KBr, LiCl-LiBr-LiF, and LiCl-KCl.

[0007] A method for preparing a high-utilization thermal battery composite positive electrode material comprises the following steps:

[0008] (1) high-energy ball milling the active positive electrode material for a certain period of time to obtain sieve powders of different mesh sizes;

[0009] (2) subjecting the screened powder to high temperature treatment to obtain activated positive electrode powder;

[0010] (3) The high-temperature treated positive electrode powder, lithium silicon alloy powder, ion conductive agent and lithium oxide are mixed evenly, and after lithiation, screening and drying, a thermal battery composite positive electrode powder is obtained.

[0011] In step (1), the powder is ball-milled at a rate of 200 to 1000 r / min, and the ball-milling time is 2 to 15 h.

[0012] In step (2), the activation temperature is 200-800° C. and the activation time is 2-15 hours.

[0013] In step (3), the drying temperature is 100 to 500° C. and the drying time is 2 to 15 hours.

[0014] The present invention has the following advantages:

[0015] (1) A preparation method and application of a high-utilization thermal battery composite positive electrode material of the present invention, through a high-energy ball milling process, FeS 2 The particle size of the positive electrode powder is reduced and evenly distributed, which increases the specific surface area of ​​the positive electrode material, reduces the solutes in the electrolyte when the positive electrode material participates in the electrode reaction, prolongs the retention time of the double electrical layer structure of the electrode interface, and effectively improves the utilization rate of the positive electrode material and the specific capacity of the thermal battery.

[0016] (2) A preparation method and application of a high-utilization thermal battery composite positive electrode material of the present invention, through a magnetic suspension screening process, FeS 2 The positive electrode powder is screened in different mesh ranges, and the particles with the same mesh range that have the closest particle size distribution to FeS 2 and CoS 2 The positive electrode powder is matched to improve the mixing uniformity and reaction activity of the two, and further improve the utilization rate of the positive electrode material.

[0017] (3) The preparation method and application of a high-utilization thermal battery composite positive electrode material of the present invention effectively improves the utilization rate of the positive electrode material and the working time of the thermal battery by optimizing the capacity matching problem of the positive and negative electrode materials of the thermal battery.

[0018] (4) A preparation method and application of a high-utilization thermal battery composite positive electrode material of the present invention, using two sulfide FeS 2 and CoS 2 The positive electrode material and the mixing with the ionic conductive agent with higher conductivity significantly reduce the polarization resistance and ohmic resistance during the discharge process of the thermal battery, and extend the working time of the thermal battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a discharge performance diagram of a single battery of positive electrode materials with different particle sizes in the present invention;

[0020] Figure 2 The FeS in the present invention 2 SEM photos of raw materials before and after ball milling and sieving;

[0021] Figure 3 The FeS in the present invention 2 Laser particle size test of raw materials before and after ball milling and screening;

[0022] Figure 4 The CoS in the present invention 2 SEM photo of raw materials (a) and laser particle size test image (b);

[0023] Figure 5 This is a discharge performance diagram of a single cell composed of different negative electrode lithium contents in the present invention. DETAILED DESCRIPTION

[0024] The preparation method and application of a high-utilization thermal battery composite positive electrode material of the present invention solve the technical problems that restrict the development of thermal batteries, such as large and uneven particle size of thermal battery positive electrode materials, insufficient design of positive and negative electrode capacity matching, resulting in low positive electrode material utilization, and limited actual discharge capacity.

[0025] The present invention provides a method for preparing a high-utilization thermal battery composite positive electrode material, and the specific steps are as follows:

[0026] S1. After high-energy ball milling of the original positive electrode material, sieve powders of different particle sizes ranging from 200 mesh to 600 mesh are obtained;

[0027] S2, activating the powders of different particle sizes and setting them aside;

[0028] S3. Evenly mix the activated positive electrode powder, lithium silicon alloy powder, ion conductive agent and lithium oxide, and obtain the thermal battery composite positive electrode powder after lithiation, sieving and drying.

[0029] Application Example 1:

[0030] The thermal battery composite positive electrode material prepared in the embodiment is used to assemble the battery. The single cell is composed of two positive electrode materials, an ion conductive agent, an electrolyte separator, a baffle ring, a thermal buffer layer, a negative electrode material and a current collector. Take 1g of each thermal battery composite positive electrode material of different particle sizes in Example 1, 0.9g of electrolyte, 0.46g of negative electrode lithium-boron alloy, add a baffle ring and a current collector to form a single cell with a diameter of 31mm; the single cell is placed in a hot press at 450℃ and the current density is 100mA / cm 2 Constant current discharge, the lower cut-off voltage is 1.3V, discharge data see Figure 1 .

[0031] Figure 1 The discharge performance diagram of the positive electrode monomer battery with different particle sizes in the present invention shows that after the three monomer batteries were discharged at no load for 1 minute, they were then discharged at a current density of 100 mA / cm 2 When the cut-off voltage is 1.3V, the discharge time of the 200-mesh, 400-mesh and 600-mesh composite positive electrode single-cell batteries is 2055s, 2500s and 2580s respectively, and the discharge specific capacity is 354mAh.g -1 , 430mAh.g -1 and 444mAh.g -1 The discharge results show that the cut-off voltage is 1.3V, and the discharge time of the 600-mesh composite positive electrode single cell is 25.5% longer than that of the 200-mesh composite positive electrode single cell.

[0032] Combination Figure 2 Scanning electron microscope images show that FeS 2 The particle size of the raw powder before processing is large and the shape is uneven. After high-energy ball milling and magnetic suspension screening process, the particle size is significantly reduced and the shape is roughly uniform. Figure 3 200 mesh, 400 mesh, 600 mesh FeS 2 Laser particle size test diagram of powder, where FeS 2 The median particle size of the powder decreased from 59.12 μm to 7.85 μm. Figure 4 For CoS 2 SEM photos of raw materials and laser particle size test images show that CoS 2 The particle size of the raw material is 8.06 μm, which is different from the FeS 2 The particle size (7.85 μm) is close. Figure 1The discharge results show that the composite sulfide positive electrode single cell with smaller and similar particle size has the best discharge performance. The main reasons are: first, the particle sizes of the two sulfide positive electrodes are close, which can improve the mixing uniformity and reaction activity of the positive electrode powder; second, the positive electrode particle size is smaller, which can shorten the diffusion path of lithium ions, reduce the solutes of the positive electrode material and the electrolyte when the positive electrode material participates in the electrode reaction, reduce the polarization resistance and ohmic resistance during the discharge process, and effectively improve the utilization rate of the positive electrode material and the working time of the thermal battery.

[0033] Application Example 2:

[0034] Take 1g of the 600-mesh thermal battery composite positive electrode material undersieve in Example 2, 0.9g of electrolyte, 0.23g, 0.46g and 0.6g of negative electrode lithium-boron alloy respectively, add a baffle ring, a thermal buffer layer and a current collector to form a single cell with a diameter of 31mm; the single cell is discharged at a constant current density of 100mA / cm2, the lower cut-off voltage is 1.3V, and the discharge data is shown in FIG. Figure 5 .

[0035] Figure 5 The discharge performance diagram of three monomer batteries with different negative electrode lithium contents in the present invention shows that after the three monomer batteries are discharged at no load for 1 minute, they are discharged at a constant current with a current density of 100 mA / cm 2 When the cut-off voltage is 1.3V, the discharge time of the three cells with different negative electrode contents is 1706s, 2580s and 3290s, respectively, and the corresponding discharge capacity is 294mAh.g -1 , 444mAh.g -1 and 567mAh.g -1 The results show that the cut-off voltage is 1.3V, and the negative electrode Li-B (0.6g) / FeS 2 Ratio Li-B(0.23g) / FeS 2 The discharge time of the system's single cell increased by 92.8%, indicating that when the free lithium content in the lithium-boron alloy of the negative electrode of the single cell is increased to a certain range, the fibrous skeleton of the lithium-boron compound is guaranteed not to collapse, which can effectively improve the utilization rate of the positive electrode material and extend the working time of the thermal battery.

[0036] In summary, the high-utilization thermal battery composite positive electrode material of the present invention can be discharged stably for a long time in the thermal battery, which can improve the utilization rate of the positive electrode material, effectively extend the working time of the thermal battery, ensure the stable operation of the thermal battery, and has extremely high engineering application value.

Claims

1. A high-utilization thermal battery composite positive electrode material, characterized by: It includes two sulfide active positive electrode materials, FeS2 and CoS2, lithium silicon alloy powder, lithium oxide and ion conductive agent, and the mass percentages are: 30% to 90% active positive electrode material, 10% to 50% ion conductive agent, 1% to 20% lithium silicon alloy powder, 1% to 30% lithium oxide, and the ion conductive agent is at least one eutectic salt of LiCl-LiBr-KBr, LiCl-LiBr-LiF, and LiCl-KCl.

2. A method for preparing a high-utilization thermal battery composite positive electrode material, characterized in that: Using the high-utilization thermal battery composite positive electrode material according to claim 1, comprising the following steps: (1) high-energy ball milling the active positive electrode material for a certain period of time to obtain sieve powders of different mesh sizes; (2) subjecting the screened powder to high temperature treatment to obtain activated positive electrode powder; (3) The high-temperature treated positive electrode powder, lithium silicon alloy powder, ion conductive agent and lithium oxide are mixed evenly, and after lithiation, screening and drying, a thermal battery composite positive electrode powder is obtained.

3. The method for preparing a high-utilization thermal battery composite positive electrode material according to claim 2, characterized in that: In step (1), the powder is ball-milled at a rate of 200 to 1000 r / min, and the ball-milling time is 2 to 15 h.

4. The method for preparing a high-utilization thermal battery composite positive electrode material according to claim 2, characterized in that: In step (2), the activation temperature is 200-800° C. and the activation time is 2-15 hours.

5. The method for preparing a high-utilization thermal battery composite positive electrode material according to claim 2, characterized in that: In step (3), the drying temperature is 100 to 500° C. and the drying time is 2 to 15 hours.

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