A lithium-carbon dioxide battery positive electrode and preparation method thereof

Abstract

This invention discloses a lithium-carbon dioxide battery cathode and its preparation method. Using a one-step hydrothermal synthesis method, CuCo2S4 nanosheets are in situ generated on hydrophilic carbon cloth. This lithium-carbon dioxide battery cathode provides abundant reaction sites and short ion diffusion pathways, providing more space for the accumulation of discharge products and facilitating the reversible formation and decomposition of these products. The lithium-carbon dioxide battery exhibits a high discharge capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-carbon dioxide batteries, and in particular to a lithium-carbon dioxide battery positive electrode and a preparation method thereof. Background Art

[0002] As the global economy and technology continue to develop, humanity's demand for and consumption of energy is increasing. Exploring and finding new energy materials and developing new energy sources are among humanity's most pressing challenges. Due to the increasing carbon dioxide emissions and the greenhouse effect, finding and developing new methods for recycling carbon dioxide is also considered crucial. Lithium-carbon dioxide (Li-CO2) batteries, which use lithium metal as the negative electrode and carbon dioxide as the positive electrode, have attracted considerable attention due to their ability to reversibly utilize and convert CO2 for energy storage.

[0003] Lithium-carbon dioxide batteries are widely used due to their high discharge voltage (~2.8 V) and theoretical high energy density of 1876 Wh kg based on the Li-CO2 system. -1 Unfortunately, the reversibility and cycle performance of lithium-carbon dioxide batteries are poor, which seriously hinders their further application. The by-product Li2CO3 acts as an insulator, making lithium-carbon dioxide batteries (4Li + +3CO2+4e – →2Li2CO3+C,E θ =2.80V vs.Li / Li + )’s positive electrode surface is passivated, so a high decomposition voltage is required during charging. However, high potentials can lead to severe decomposition of the electrolyte, thereby reducing the battery’s electrochemical performance and cycle reversibility. Therefore, the key to improving the performance of lithium-carbon dioxide batteries is to develop efficient cathode catalysts to reduce the charging potential and promote the reversible generation and decomposition of discharge products. Summary of the Invention

[0004] The present invention aims to provide a lithium-carbon dioxide battery positive electrode and a preparation method thereof, which provides abundant reaction sites and shorter ion diffusion paths, provides more accumulation space for discharge products, and improves the discharge capacity of the lithium-carbon dioxide battery.

[0005] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0006] The present invention discloses a method for preparing a positive electrode of a lithium-carbon dioxide battery, comprising the following steps:

[0007] (1) The carbon cloth is first heat-treated, then ultrasonically cleaned with acetone and water respectively, then immersed in potassium persulfate and sulfuric acid solution, finally ultrasonically cleaned with water, and then dried to obtain a hydrophilic carbon cloth;

[0008] (2) adding copper acetate monohydrate, cobalt acetate tetrahydrate and thiourea to a mixture of water and ethylene glycol, and stirring to form a homogeneous solution;

[0009] (3) The solution obtained in step (2) is transferred to a reactor, and the carbon cloth obtained in step (1) is placed therein, and the reaction is carried out by high-temperature steam sealing; after the reaction, the reaction is cooled to room temperature, and the obtained material is washed and dried to obtain the positive electrode of the lithium-carbon dioxide battery.

[0010] As a preferred technical solution, in step (1), the carbon cloth is first heat-treated at 400°C for 20 minutes, then ultrasonically washed with acetone and water for 1 hour respectively, and then the carbon cloth is immersed in a 5% potassium persulfate and 10% sulfuric acid solution at 80°C for 8 hours, and finally ultrasonically washed with water and dried to obtain a hydrophilic carbon cloth.

[0011] As a preferred technical solution, in step (2), the molar ratio of copper acetate monohydrate, cobalt acetate tetrahydrate and thiourea is 1:2:4, and the volume ratio of water to ethylene glycol is 1:1.

[0012] As a preferred technical solution, in step (3), the temperature of the high-temperature steam seal is maintained at 200° C. for 20 hours.

[0013] The present invention discloses a lithium-carbon dioxide battery positive electrode prepared by the above preparation method, in which CuCo2S4 nanosheets are in situ generated on a hydrophilic treated carbon cloth.

[0014] As a preferred technical solution, the mass loading of CuCo2S4 nanosheets on carbon cloth is 0.8-1.0 mg cm -2 .

[0015] Beneficial effects of the present invention:

[0016] (1) The present invention uses carbon cloth as the base material, which ensures good electrical conductivity and flexibility. It can be used as a base to support active materials and directly used as a working electrode without adding any adhesive.

[0017] (2) The nanosheet morphology of CuCo2S4 provides a high specific surface area, abundant reaction sites and shorter ion diffusion paths.

[0018] (3) The positive electrode material of the present invention constructs a three-dimensional transmission channel for ions and gases, providing more accumulation space for discharge products and facilitating the reversible generation and decomposition of discharge products. The lithium-carbon dioxide battery exhibits a high discharge capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a scanning electron microscope image of the positive electrode of the lithium-carbon dioxide battery prepared in Example 1.

[0020] Figure 2 This is the specific capacity-voltage curve of the lithium-carbon dioxide battery prepared in Example 1.

[0021] Figure 3 This is the specific capacity-voltage curve of the lithium-carbon dioxide battery prepared in Example 2. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described below with reference to the accompanying drawings.

[0023] Example 1

[0024] (1) First, the carbon cloth was heat-treated at 400°C for 20 minutes, and then ultrasonically washed with acetone and water for 1 hour respectively. Then, the carbon cloth was immersed in 5% potassium persulfate and 10% sulfuric acid solution at 80°C for 8 hours. Finally, the carbon cloth was ultrasonically washed with water for 3 times, each washing time was 10 minutes, and then dried at 80°C to obtain the hydrophilic carbon cloth. The carbon cloth was cut into 1 cm wide and 5 cm long specifications for standby use.

[0025] (2) adding 2 mmol of copper acetate monohydrate, 4 mmol of cobalt acetate tetrahydrate, and 8 mmol of thiourea to a mixture of water and ethylene glycol in a volume ratio of 1:1, and stirring to form a homogeneous solution;

[0026] (3) The solution obtained in step (2) is transferred to a reactor, and the carbon cloth obtained in step (1) is placed in the reactor, and the reaction is carried out at 200°C with high-temperature steam sealing for 20 hours; after the reaction, the reaction is cooled to room temperature, and the obtained material is washed and dried to obtain the positive electrode of the lithium-carbon dioxide battery.

[0027] Scanning electron microscope image of the positive electrode of lithium-carbon dioxide battery Figure 1 As shown in the figure, it can be seen that CuCo2S4 nanosheets are in situ generated on the hydrophilic treated carbon cloth, and the mass loading of CuCo2S4 nanosheets on the carbon cloth is 0.8-1.0 mg cm -2 .

[0028] The obtained positive electrode was cut into pieces with an area of ​​1×1 cm -2 In a high-purity argon glove box with water and oxygen content below 0.1 PPM, the negative electrode shell, spring, gasket, lithium negative electrode, glass fiber separator, 100 μL of 1.0 M lithium bistrifluoromethanesulfonyl imide (LiTFSI) dissolved in tetraethylene glycol dimethyl ether (TEGDME) electrolyte were sequentially stacked, followed by the positive electrode and a porous positive electrode shell (CR2032 type). The lithium-carbon dioxide battery was assembled on a hydraulic packaging machine.

[0029] After the lithium-carbon dioxide battery is assembled, it is transferred to a sealed test chamber. High-purity CO2 is then continuously introduced into the test chamber at a certain flow rate for 30 minutes and stabilized in a 25°C constant temperature chamber for 12 hours to ensure that the battery is in a stable CO2 atmosphere. After that, the circuits are connected and the LAND-CT2001A battery test system is used to perform a full discharge at a specific current at a constant temperature. 20μA cm in a CO2 and Ar atmosphere. -2 The full discharge performance test was carried out at a current density of Figure 2 As shown in Figure 2, when the cut-off voltage is 2.0 V, the discharge capacity of the lithium-carbon dioxide battery is 1577.2 μAh cm -2 .

[0030] Example 2

[0031] The only difference between Example 2 and Example 1 is that after the lithium-carbon dioxide battery is assembled, it is transferred to a sealed test box, and then high-purity CO2 is continuously introduced into the test box at a certain flow rate for 30 minutes, and then stabilized in a 25°C constant temperature box for 12 hours to ensure that the battery is in a stable CO2 atmosphere. Then, the circuits are connected and a specific current discharge-charge cycle test is performed at a constant temperature using the LAND-CT2001A battery test system. At 10μA cm -2 The discharge-charge cycle test was carried out at a current density of , and the electrochemical test results were as follows Figure 3 As shown, there is a small charge and discharge overpotential of only 0.62V between the cathodes, and the cycle performance is good.

[0032] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a positive electrode of a lithium-carbon dioxide battery, characterized in that: The following steps are involved: (1) The carbon cloth is first heat-treated, then ultrasonically cleaned with acetone and water respectively, then immersed in potassium persulfate and sulfuric acid solution, finally ultrasonically cleaned with water, and then dried to obtain a hydrophilic carbon cloth; (2) adding copper acetate monohydrate, cobalt acetate tetrahydrate and thiourea to a mixture of water and ethylene glycol, and stirring to form a homogeneous solution; (3) The solution obtained in step (2) is transferred to a reactor, and the carbon cloth obtained in step (1) is placed therein, and the reaction is carried out by high-temperature steam sealing; after the reaction, the reaction is cooled to room temperature, and the obtained material is washed and dried to obtain the positive electrode of the lithium-carbon dioxide battery.

2. The method for preparing a positive electrode for a lithium-carbon dioxide battery according to claim 1, wherein: In the step (1), the carbon cloth is first heat-treated at 400° C. for 20 minutes, then ultrasonically washed with acetone and water for 1 hour respectively, and then the carbon cloth is immersed in a 5% potassium persulfate and 10% sulfuric acid solution at 80° C. for 8 hours, and finally ultrasonically washed with water and dried to obtain a hydrophilic carbon cloth.

3. The method for preparing a positive electrode for a lithium-carbon dioxide battery according to claim 1, wherein: In the step (2), the molar ratio of copper acetate monohydrate, cobalt acetate tetrahydrate and thiourea is 1:2:4, and the volume ratio of water to ethylene glycol is 1:

1.

4. The method for preparing a positive electrode for a lithium-carbon dioxide battery according to claim 1, wherein: In the step (3), the temperature of the high-temperature steam seal is maintained at 200° C. for 20 hours.

5. The lithium-carbon dioxide battery positive electrode prepared by the preparation method according to any one of claims 1 to 4, characterized in that: CuCo2S4 nanosheets were in situ generated on hydrophilic treated carbon cloth.

6. The lithium-carbon dioxide battery positive electrode according to claim 5, characterized in that: The mass loading of CuCo2S4 nanosheets on carbon cloth is 0.8-1.0 mg cm -2 .

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