Method for detecting lithium-carbon dioxide battery cathode discharge products

Abstract

The application discloses a kind of Li-CO2 battery anode discharge product detection methods, after discharging Li-CO2 battery is removed anode, it is washed after being placed in organic solvent and dried;After washing, the anode is placed in 10-20mL ultrapure water, so that anode product Li2C2O4 is fully reacted with H2O and dissolved, then separation is obtained reaction solution and anode;KI's acid solution is mixed in the obtained reaction solution, titrate to colorless by Na2S2O3 standard solution, it is titration end point, calculate Li2C2O4 content;The obtained anode is placed in aqueous solution containing methyl orange indicator, titrate to light pink by HCl standard solution, it is titration end point, calculate Li2CO3 content;The present application effectively solves the Li2C2O4 / Li2CO3 detection problem urgently needed to be solved in the current organic system Li-CO2 battery research, with the advantages of low detection cost, high efficiency, small human error, rapid detection etc.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of Li-CO2 battery, and particularly relates to a detection method of positive electrode discharge product of a Li-CO2 battery. BACKGROUND

[0002] The emission of power plant and industrial waste gas is a global environmental and social problem, and its resource utilization is of great significance to environmental protection and energy security. Designing CO2 as both a reaction medium and a reactant to achieve chemical conversion and utilization is a challenging topic in the current field of green chemistry. A new battery system (Li-CO2 battery) with CO2 or its mixed gas as the cathode active ingredient is expected to become a powerful technology to alleviate the greenhouse effect and treat power plant waste gas, and to realize the conversion and energy storage of CO2 at room temperature.

[0003] Compared with conventional CO2 treatment technologies (electrolytic reduction method, photoelectric reduction method, high-temperature solid oxide electrolysis cell (SOECs), etc.), the organic system Li-CO2 battery has the advantages of high capacity, wide electrochemical window, high CO2 solubility, high safety and high adaptability. However, due to the low conductivity and electrochemical activity of Li2CO3, the Li-CO2 battery is prone to high polarization during charging. Therefore, exploring the electrochemical activity of Li2CO3 and finding a solution are key scientific problems for optimizing the performance of the Li-CO2 battery.

[0004] From the perspective of regulating high-efficiency catalysts, current research has two solutions. Most researchers have improved the deposition and decomposition of Li2CO3 at the cathode by regulating the morphology of highly active catalysts. The resulting ordered, weakly crystalline Li2CO3 can maximize the utilization of active sites while enhancing its own electrochemical activity. Under this technical path, traditional highly active catalysts such as carbon materials and their composites: graphene, Cu / nitrogen-doped graphene, etc.; transition metals and their composites: Ir / B4C, Ru / N-doped CNT, Ru / nickel foam, RuCu alloy, etc.; metal oxides: RuO2 / CNT, etc.; metal carbides and redox pairs, etc., have all solved the problems of mass transfer, thermodynamic stability, and interfacial contact of Li2CO3 to varying degrees. In addition, the recent emerging catalyst design scheme has innovatively proposed an intermediate product (Li2C2O4) stabilization strategy. By designing catalyst adsorption sites to stabilize Li2C2O4, the traditional highly stable Li2CO3 of Li-CO2 batteries is converted into highly active Li2C2O4, reducing the energy barrier required for its decomposition, and greatly reducing the charge overpotential of Li-CO2 batteries. The currently reported Mo2C, MoN and their composite materials are efficient catalysts for realizing this strategy, thanks to the Mo and C2O4 2- The stable combination of Li2C2O4 and Li2CO3 significantly reduces the charge voltage of the corresponding Li-CO2 battery and further extends the cycle life. Therefore, the rational catalyst design to maximize the production of Li2C2O4 is one of the current research hotspots of Li-CO2 batteries, and the establishment of an efficient and reasonable Li2C2O4 / Li2CO3 detection platform is the cornerstone of this research.

[0005] Given the urgent need to address the Li2C2O4 / Li2CO3 detection issues in organic Li-CO2 batteries, building a Li2CO3 and Li2C2O4 detection platform is crucial. However, the Li-CO2 battery field currently relies on conventional testing methods such as XRD, Raman, and infrared spectroscopy for qualitative analysis. These methods suffer from high costs, low efficiency, significant human error, and inherent limitations in rapid detection. Furthermore, Li2C2O4 is extremely unstable in air, and conventional testing methods inevitably lead to oxidation during sample transportation and testing, significantly reducing accuracy. Summary of the Invention

[0006] The purpose of the present invention is to propose a method for detecting discharge products of the positive electrode of a Li-CO2 battery, which can quickly detect the content of Li2C2O4 / Li2CO3 and has the advantages of low cost, short time consumption, low operation requirements, high detection accuracy and quantitative analysis.

[0007] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0008] The method for detecting the discharge product of the positive electrode of a Li-CO2 battery comprises the following steps:

[0009] (1) After the Li-CO2 battery is discharged, the positive electrode is removed, cleaned in an organic solvent, and dried;

[0010] (2) The cleaned positive electrode is placed in 10-20 mL of ultrapure water, so that the positive electrode product Li2C2O4 fully reacts with H2O and is dissolved, and then the reaction solution and the positive electrode are separated;

[0011] (3) The obtained reaction solution is mixed with an acidic KI solution, titrated with a Na2S2O3 standard solution until colorless, which is the titration end point, and the content of Li2C2O4 is calculated;

[0012] (4) The obtained positive electrode is placed in an aqueous solution containing a methyl orange indicator, titrated with an HCl standard solution until light pink, which is the titration end point, and the content of Li2CO3 is calculated.

[0013] According to the above scheme, the organic solvent in step 1 is dimethyl ether or acetonitrile, and ultrasonic cleaning is used.

[0014] According to the above scheme, the drying method in step 1 is vacuum drying or wiping.

[0015] According to the above scheme, the cleaned positive electrode in step 2 is placed in boiling ultrapure water.

[0016] According to the above scheme, the amount of the acidic KI solution in step 3 is 0.5-10 ml, the concentration of KI is 2 wt%, the acidified solution is H2SO4, and the pH is 2.

[0017] According to the above scheme, the amount of the methyl orange indicator in step 4 is 0.1 ml, and the aqueous solution is 10-20 mL.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] The present application effectively solves the problem of detecting Li2C2O4 / Li2CO3 in the current research of organic system Li-CO2 battery, which has the advantages of low detection cost, high efficiency, small human error, and rapid detection.

[0020] The rapid detection method proposed by the present application successfully avoids the problem of significant reduction in detection accuracy caused by the instability of Li2C2O4 in air in the conventional test environment.

[0021] The application separates Li2C2O4 / Li2CO3 from water by using the reactivity and solubility difference of Li2C2O4 / Li2CO3 in water, and then separately titrates and detects, which greatly increases the operability and detection accuracy; meanwhile, by increasing the water temperature and reducing the amount of reaction water, the amount of Li2CO3 dissolved in water is controlled within an acceptable error range. DETAILED DESCRIPTION

[0022] The following examples further illustrate the technical solutions of the application, but do not limit the scope of protection of the application.

[0023] The specific embodiment provides a detection method for positive electrode discharge products of a Li-CO2 battery, comprising the following steps:

[0024] (1) remove the positive electrode of the discharged Li-CO2 battery, clean it in an organic solvent, and dry it;

[0025] (2) place the cleaned positive electrode in 10-20 mL of ultrapure water, make the positive electrode product Li2C2O4 fully react and dissolve with H2O, and then separate to obtain a reaction solution and a positive electrode;

[0026] (3) add an acidic KI solution to the obtained reaction solution, titrate with a Na2S2O3 standard solution until colorless, which is the titration endpoint, and calculate the Li2C2O4 content;

[0027] (4) place the obtained positive electrode in an aqueous solution containing a methyl orange indicator, titrate with an HCl standard solution until light pink, which is the titration endpoint, and calculate the Li2CO3 content.

[0028] Specifically, the organic solvent in step 1 is dimethyl ether or acetonitrile, and ultrasonic-assisted cleaning is used.

[0029] Specifically, the drying method in step 1 is vacuum drying or wiping. Reducing the contact time of the positive electrode with oxygen can increase the accuracy.

[0030] Specifically, the cleaned positive electrode in step 2 is placed in boiling ultrapure water. Li2CO3 is slightly soluble in water, and increasing the water temperature can not only reduce the solubility of Li2CO3 in water, but also increase the reaction efficiency of Li2C2O4 with H2O; at the same time, in this step, the amount of ultrapure water should be reduced as much as possible under the premise of ensuring that Li2C2O4 fully reacts with H2O, to further reduce the amount of Li2CO3 dissolved and reduce errors.

[0031] Specifically, the amount of the acidic KI solution in step 3 is 0.5-10 ml, the KI concentration is 2 wt%, the acidified solution is H2SO4, and the pH is 2.

[0032] Specifically, the amount of methyl orange indicator used in step 4 is 0.1 ml, and the aqueous solution is 10-20 mL.

[0033] Example 1

[0034] (1) After uniformly coating Mo2C as the catalyst material on carbon paper, assemble it into a Li-CO2 battery, discharge it to 0.4 mAh, and then remove it from the glove box for disassembly.

[0035] (2) After disassembling the above battery to obtain the target electrode, immediately wash it in acetonitrile solvent to remove the surface residual organic impurities, and vacuum dry it for 6 h.

[0036] (3) Quickly place the dried electrode into a glass container containing 20 mL of ultrapure water, with the water temperature at 99°C, and shake vigorously for 20 seconds to completely dissolve the discharge products in the target electrode. After complete dissolution, separate the reaction solution and the target electrode for subsequent titration test. The chemical reaction involved is as follows:

[0037] Li2C2O4 + 2H2O = H2C2O4 + 2LiOH

[0038] (4) Add 2wt% KI / H2SO4 acid solution to the reaction solution, with the amount being 0.5 ml, and titrate with Na2S2O3 standard solution until it is colorless, which is the end point of titration. The amount of Na2S2O3 standard solution used is 15.82 ml, and the chemical reaction involved is as follows:

[0039] H2C2O4 + 2KI + H2SO4 = I2 + K2SO4 + 2H2O

[0040] I2 + 2Na2S2O3 = Na2S4O6 + 2NaI

[0041] The Li2C2O4 content in the target solution can be calculated based on the volume of Na2S2O3 standard solution and 2wt% KI / H2SO4 solution consumed by Li2C2O4, and the specific calculation process is as follows:

[0042]

[0043]

[0044]

[0045] (5) Place the target positive electrode in an aqueous solution containing methyl orange indicator, with the amount of methyl orange indicator being 0.1 ml and the amount of aqueous solution being 20 mL. Titrate with 2.08 ml of HCl standard solution until it is light pink, which is the end point of titration, and calculate the Li2CO3 content. The chemical reaction involved is as follows:

[0046] Li2CO3 + 2HCl = 2LiCl + CO2 + H2O

[0047] The Li2CO3 content in the target solution can be calculated based on the volume of the standard HCl solution consumed by Li2CO3, and the specific calculation process is as follows.

[0048] n HCl = C HCl V HCl = 5 x 10 -3 mol / L x 2.08 x 10 -3 L = 10.4 μmol

[0049]

[0050] Finally, it is concluded that the Li-CO2 battery in this embodiment is discharged to 0.4 mAh, the Li2CO3 content is 5.2 μmol, the Li2C2O4 content is 8.0 μmol, and the ratio of the two is

Claims

1. A method for detecting discharge products of a positive electrode of a Li-CO2 battery, characterized in that The following steps are involved: (1) Remove the positive electrode of the discharged Li-CO2 battery, wash it in an organic solvent, and then dry it; (2) The cleaned positive electrode is placed in 10-20 mL of ultrapure water to allow the positive electrode product Li2C2O4 to fully react with H2O and dissolve, and then separate to obtain the reaction solution and the positive electrode; (3) Add KI acidic solution to the obtained reaction solution, mix, and titrate with Na2S2O3 standard solution until it becomes colorless, which is the titration end point, and calculate the Li2C2O4 content; (4) The obtained positive electrode is placed in an aqueous solution containing methyl orange indicator and titrated with HCl standard solution until the color turns light pink, which is the titration end point. The Li2CO3 content is calculated.

2. The method for detecting discharge products of the positive electrode of a Li-CO2 battery according to claim 1, wherein The organic solvent in step 1 is dimethyl ether or acetonitrile, and ultrasonic cleaning is used.

3. The method for detecting discharge products of the positive electrode of a Li-CO2 battery according to claim 1, characterized in that The drying method in step 1 is vacuum drying or wiping.

4. The method for detecting discharge products of a positive electrode of a Li-CO2 battery according to claim 1, wherein The positive electrode cleaned in step 2 is placed in boiling ultrapure water.

5. The method for detecting discharge products of the positive electrode of a Li-CO2 battery according to claim 1, wherein In step 3, the amount of the acidic KI solution used is 0.5-10 ml, the KI concentration is 2 wt %, the acidified solution is H 2 SO 4 , and the pH is 2.

6. The method for detecting discharge products of a positive electrode of a Li-CO2 battery according to claim 1, wherein The dosage of the methyl orange indicator in step 4 is 0.1 ml, and the aqueous solution is 10-20 mL.

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