Composite positive electrode material and preparation method thereof, and high-specific-energy single battery containing composite positive electrode material

Abstract

The invention discloses a composite positive electrode material and a preparation method thereof in the technical field of batteries, and a high-specific-energy single battery containing the composite positive electrode material. The composite positive electrode material comprises the following raw materials: nickel chloride, potassium chloride, an adsorbent and graphene in a weight ratio of (80-95): (1-10): (3-10): (1-5). The preparation method comprises the following steps: uniformly mixing nickel chloride, potassium chloride and an adsorbent, calcining in an inert atmosphere, taking out, crushing, adding graphene, uniformly mixing, and tabletting to obtain the composite positive electrode material, the composite positive electrode material has relatively high specific capacity, and the specific capacity is improved by 15% compared with that of a conventional CoS2 composite sheet; compared with a conventional halide composite sheet, the specific capacity is improved by 60%. The material is used for preparing a high-specific-energy single battery, the electromotive force of the single battery obtained by matching with a negative electrode assembly, a diaphragm piece, carbon paper, a substrate and a heating piece is 2.5 V, internal resistance increase in the discharging process is avoided, and the material has high conductivity and thermal stability.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a composite positive electrode material and a preparation method thereof, and a high-energy-density single cell containing the composite positive electrode material. Background Art

[0002] Thermal batteries are heat-activated storage batteries that rely on their own heating system to heat and melt non-conductive solid salt electrolytes into ionic conductors to enter the working state. Thermal batteries have the characteristics of activation at any angle, fast activation speed, long storage time, and strong ability to withstand environmental mechanical conditions. They have been widely used in aerospace systems, etc. In addition, the application of thermal batteries in the civilian field has also received attention. There have been research reports on their use as aircraft emergency power supplies, fire alarm power supplies, and underground high-temperature prospecting power supplies.

[0003] With the continuous development and updating of products, the requirements for the performance of thermal batteries are getting higher and higher, and the requirements for their working time, output power, and high specific characteristics are getting higher and higher. Thermal batteries are mainly composed of substrates, positive electrodes, diaphragms, negative electrode components (negative electrodes, asbestos rings, sheet current collectors), heating systems (electric ignition heads or flames, ignition paper, heating sheets), insulation pads, battery shells, and battery covers with terminals. Among them, the influence of thermal battery electrode materials on its output capacity, specific capacity, specific power and other electrochemical properties is the most critical.

[0004] Nowadays, thermal batteries have strict requirements on single cells. Among conventional single cells, only cells with positive electrode materials such as FeS2 and CoS2 can be used in engineering applications. They match lithium alloy negative electrode materials and have relatively mature technology. However, the operating voltage of its single cells is below 2V, and high-power output will be greatly limited. At the same time, the specific capacity has reached a certain limit (theoretical specific capacity 1206As / g (333mAh / g)), which is not conducive to the development of miniaturized and lightweight thermal batteries. Therefore, it is urgent to carry out research on new positive electrode technologies with both high potential and high specific capacity, and develop high-potential and high-specific capacity composite sheets.

[0005] In addition, the commonly used conventional nickel chloride composite positive electrode sheet mainly includes nickel chloride, diaphragm and graphite. The positive electrode single cell prepared by such a composite positive electrode sheet can meet the working voltage of 2.5V, but the halide therein is compatible with the molten salt and does not have the ability to work for a long time. Summary of the invention

[0006] The present invention aims to provide a composite positive electrode sheet and a preparation method thereof, and a single cell for a high specific energy thermal battery containing the same, so as to solve the problem in the prior art that thermal batteries assembled with single cells of halide positive electrode materials that can meet an operating voltage of 2.5V do not have the ability to work for a long time.

[0007] In a first aspect, the present invention provides a composite positive electrode material, comprising raw materials and a weight ratio of nickel chloride: potassium chloride: adsorbent: graphene of 80-95:1-10:3-10:1-5.

[0008] Furthermore, the adsorbent is selected from one of MgO and Al2O3.

[0009] Furthermore, the nickel chloride is sublimated nickel chloride.

[0010] In a second aspect, the present invention also provides a method for preparing the composite positive electrode material, comprising the following steps:

[0011] S1. Mix nickel chloride, potassium chloride and adsorbent, calcine under an inert atmosphere, and crush them for later use;

[0012] S2, adding graphene to the mixed material of S1, mixing well and then pressing into tablets to obtain the composite positive electrode material.

[0013] Furthermore, the inert atmosphere is preferably argon or helium, and the entire preparation process is completed in a drying room with a humidity of less than 3%.

[0014] Furthermore, the calcination temperature in S1 is 700°C to 900°C.

[0015] Furthermore, the powder is sieved with a sieve of ≥80 mesh after the pulverization in S1.

[0016] In a third aspect, the present invention also provides a high specific energy single cell, the single cell comprising a negative electrode assembly, a diaphragm, carbon paper, a composite positive electrode sheet, a substrate and a heating sheet, the composite positive electrode sheet being obtained by cutting the composite positive electrode material as described in any one of claims 1 to 3.

[0017] Furthermore, the carbon paper is mainly composed of a mixture of carbon fibers and amorphous carbon, and the thickness of the carbon paper is 0.08 mm to 0.3 mm.

[0018] Furthermore, the negative electrode component is made of LiB material.

[0019] Furthermore, LiBr-KBr-CsBr is used as the electrolyte in the diaphragm sheet.

[0020] The beneficial technical effects of the present invention are:

[0021] 1. The electromotive force of the single cell of the present invention is 2.5V, which avoids the increase of internal resistance during the discharge process and has high conductivity and thermal stability.

[0022] 2. The present invention provides a composite material which is a NiCl2 composite positive electrode material, which has a higher specific capacity, which is 15% higher than the specific capacity of conventional CoS2 composite sheets; and 60% higher than the specific capacity of conventional halide composite sheets.

[0023] 3. The high specific energy single cell obtained by the present invention can meet the requirements of long-term, high specific energy single cell compared to conventional nickel chloride positive electrode single cells, and has the advantages of good electrochemical performance, strong stability, good conductivity, formability, and high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The SEM images of the nickel chloride composite positive electrode material described in Example 1 of the present invention are as follows: (a) sublimated nickel chloride raw material; (b) nickel chloride composite positive electrode powder;

[0025] Figure 2 The SEM images of the carbon papers described in Examples 4 to 6;

[0026] Figure 3 The electrical performance comparison diagram of conventional nickel chloride positive electrode single cell battery assembly and high specific energy single cell battery assembly of Examples 4 to 6 of the present invention (current density 100mA / cm 2 , load 1000mA / cm during discharge 2 Current density (pulse current);

[0027] Figure 4 The no-load curves after activation are assembled for conventional nickel chloride positive electrode single cells and the high specific energy single cells of Example 4. DETAILED DESCRIPTION

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

[0029] 1. Preparation of nickel chloride composite positive electrode material

[0030] Examples 1 to 3 The raw materials described in Table 1 were prepared in proportion, and the preparation process included the following steps:

[0031] S1. Add potassium chloride to the sublimated nickel chloride and mix well, then add the adsorbent and mix again, calcine at 700° C. to 900° C. under an inert atmosphere for 2 to 6 hours, preferably 4 hours, take out and grind, and keep the powder that passes through an 80-mesh sieve for later use;

[0032] S2. Add graphene to the powder of S1, mix well, and then press into sheets to obtain the composite positive electrode material.

[0033] Table 1 Raw materials and weight ratios of composite positive electrode materials used in various examples

[0034] Example Adsorbent Sublimation Nickel Chloride: Potassium Chloride: Adsorbent: Graphene Example 1 MgO 85：7：6：2 Example 2 MgO 95:10:3:5 Example 3 <![CDATA[Al2O3]]> 80:1:10:1

[0035] 2. Preparation of high specific energy monomer battery

[0036] Examples 4 to 6 are as follows to prepare high specific energy single cells:

[0037] (1) A LiB negative electrode assembly, a diaphragm, carbon paper, a nickel chloride composite positive electrode sheet, a substrate and a heater sheet are prepared; wherein the diaphragm uses LiBr-KBr-CsBr as an electrolyte; the carbon paper is mainly composed of a mixture of carbon fiber and amorphous carbon; the nickel chloride composite positive electrode sheet is obtained by cutting the nickel chloride composite positive electrode material described in Example 1, and the thickness of the carbon paper is shown in Table 2 below;

[0038] (2) Stack the negative electrode assembly, the diaphragm sheet, the carbon paper and the NiCl2 composite positive electrode sheet, the substrate, and the heater sheet in sequence.

[0039] Table 2 The thickness of carbon paper in each embodiment

[0040] Example Carbon paper thickness (mm) Example 4 0.18 Example 5 0.12 Example 3 0.22

[0041] Test example:

[0042] According to the method of Example 4, 16 single cells were prepared and then assembled into unit cells. The discharge was compared with that of unit cells equipped with conventional nickel chloride positive electrode single cells (composed of LiB negative electrode assembly, diaphragm, conventional nickel chloride composite positive electrode sheet (conventional nickel chloride composite positive electrode sheet, the main components include nickel chloride, diaphragm and graphite, without carbon paper), substrate and heater). Except for the single cell preparation method, the other steps of the unit cell preparation method are exactly the same; the amount of positive electrode material and diaphragm material used in the conventional single cell and the high specific energy single cell are exactly the same.

[0043] from Figure 3 and Figure 4 It can be seen that the high specific energy single cell assembly battery and the conventional single cell assembly battery have the same current density of 100mA / cm 2 Compared with conventional single-cell assembled batteries, its working time is significantly longer under low discharge and no-load, and there is no sudden drop when no-load, which avoids the mutual dissolution of positive electrode materials and diaphragm materials and improves the specific energy of thermal batteries.

Claims

1. A composite positive electrode material, characterized in that: The raw materials and weight ratio thereof are nickel chloride: potassium chloride: adsorbent: graphene which is 80-95:1-10:3-10:1-5.

2. A composite positive electrode material according to claim 1, characterized in that: The adsorbent is selected from one of MgO and Al2O3.

3. A composite positive electrode material according to claim 2, characterized in that: The nickel chloride is sublimated nickel chloride.

4. A method for preparing a composite positive electrode material according to any one of claims 1 to 3, characterized in that The following steps are involved: S1. Mix nickel chloride, potassium chloride and adsorbent, calcine under an inert atmosphere, and crush them for later use; S2, adding graphene to the mixed material of S1, mixing well and then pressing into tablets to obtain the composite positive electrode material.

5. The method for preparing a composite positive electrode material according to claim 4, characterized in that: The calcination temperature in S1 is 700°C to 900°C.

6. The method for preparing a composite positive electrode material according to claim 5, characterized in that: The powder is sieved through a sieve with mesh size of ≥80 after the pulverization in S1.

7. A high specific energy single cell, characterized in that: The single cell comprises a negative electrode assembly, a diaphragm sheet, carbon paper, a composite positive electrode sheet, a substrate and a heating sheet. The composite positive electrode sheet is obtained by cutting the composite positive electrode material as claimed in any one of claims 1 to 3.

8. A high specific energy single cell according to claim 7, characterized in that: The carbon paper is mainly composed of a mixture of carbon fibers and amorphous carbon, and the thickness of the carbon paper is 0.08 mm to 0.3 mm.

9. A high specific energy single cell according to claim 8, characterized in that: The negative electrode component is made of LiB material.

10. A high specific energy single cell according to claim 9, characterized in that: The diaphragm sheet uses LiBr-KBr-CsBr as the electrolyte.

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