A lithium-carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis

Abstract

The present invention discloses a lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis. The present invention utilizes bismuth oxyhalide / carbon paper with a layered crystal structure as a photoelectric cathode and an organic ether solvent with added halogen lithium salt as an electrolyte to enhance the light-assisted lithium carbon dioxide battery. Bismuth oxyhalide substances generate abundant electron-hole pairs under the action of the light field, which significantly reduces the difficulty of forming and decomposing Li2CO3 during the charge and discharge process. Due to the incorporation of halogen lithium salt, the photoelectric cathode is more likely to react at the solid-liquid interface, thereby enabling the photoelectric cathode to operate stably and continuously. Halogen lithium salt also helps in carrier separation, ensuring that the light-assisted lithium carbon dioxide battery maintains a low dead barrier throughout the entire cycle. The present invention significantly improves the life and stability of the photoelectric cathode through the synergistic effect of the cathode and the electrolyte, greatly reduces the difficulty of forming / decomposing the discharge product Li2CO3 during the discharge / charge process of the lithium carbon dioxide battery, reduces the overpotential of the lithium carbon dioxide battery, and improves the electrochemical performance and cycle stability of the battery.

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 with homogeneous and heterogeneous synergistic catalysis. Background Art

[0002] As a unique energy storage device for carbon dioxide storage and conversion, lithium carbon dioxide batteries are expected to alleviate a series of environmental problems caused by the continued burning of fossil fuels, such as the greenhouse effect. Generally, the theoretical energy density of lithium carbon dioxide batteries is as high as 1876Whkg -1 , is considered one of the next-generation energy storage devices with potential application prospects in many scenarios. However, the discharge product of lithium-carbon dioxide batteries, Li2CO3, is a wide-bandgap insulating material that is thermodynamically stable, resulting in slow kinetics of the carbon dioxide reduction reaction (CO2RR) and carbon dioxide evolution reaction (CO2ER). Therefore, it is crucial to find a new method to promote the formation and decomposition of Li2CO3 to achieve stable and durable lithium-carbon dioxide batteries.

[0003] External solar-driven lithium-carbon dioxide batteries are a very promising and attractive strategy. Under illumination, the photocatalyst at the cathode effectively captures photons, and the active photoexcited electrons and holes act on the redox reaction of CO2, respectively, thereby reducing voltage hysteresis and improving the reversibility of the battery. However, as the cycle progresses, the photocathode becomes very unstable, especially in the continuous strong oxidizing environment brought about by photogenerated holes. The photon utilization rate decreases, and the photocathode gradually loses its original performance. Therefore, there is an urgent need to design a strategy to effectively extend the life of the photocathode. Summary of the Invention

[0004] To solve the problems of the prior art, the purpose of this application is to provide a homogeneous and heterogeneous synergistic catalyst for light-assisted lithium carbon dioxide batteries and its preparation method and application, so as to help solve the problems of high overpotential and low cycle life of lithium carbon dioxide batteries in the prior art.

[0005] In order to solve the problems of the prior art, the technical solution adopted by the present invention is:

[0006] A lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis includes a positive electrode, a separator, a negative electrode, and an electrolyte. The positive electrode is a bismuth oxyhalide photoelectric positive electrode Bi5O7X / CP, the electrolyte is an organic ether electrolyte added with a lithium salt, and the negative electrode is a lithium foil, wherein the lithium salt includes lithium bistrifluoromethanesulfonyl imide with a final concentration of 1 mol / L and LiX with a final concentration of 0.05 mol / L, and X is Cl, Br, or I.

[0007] As an improvement, the diaphragm is a glass fiber diaphragm GF / D.

[0008] As an improvement, the organic ether electrolyte comprises a mixture of one or more of epoxide, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0009] As an improvement, the bismuth oxyhalide photoelectric positive electrode Bi5O7X / CP is prepared by mixing the active material Bi5O7X, polyvinylidene fluoride binder PVDF and Ketjen Black in a mass ratio of 8:1:1 and adding them to n-methyl-2-pyrrolidone liquid to form a uniform slurry. After that, the slurry is coated on a carbon paper disc and dried in a vacuum drying oven at 120°C for 12 hours.

[0010] A further improvement is that the preparation method of the Bi5O7X is: dissolving Bi(NO3)3·5H2O and NaOH in distilled water to form a white mixture; then adding KX solution to the white mixture, stirring for 30 minutes, heating at 180°C for 24 hours, cooling to room temperature, collecting the precipitate by centrifugation, washing with deionized water and ethanol three times respectively, and drying in a drying oven at 60°C.

[0011] As a further improvement, the final concentration of Bi(NO3)3 in the white mixture is 0.2 mol / L, the final concentration of NaOH is 0.6 mol / L, and the final concentration of KX is 0.08 mol / L.

[0012] As an improvement, the working environment of the homogeneous and heterogeneous synergistic catalytic lithium carbon dioxide battery is: the area of ​​the cut bismuth oxyhalide photoelectric positive electrode Bi5O7X / CP is 1.13cm 2 , and the effective lighting area is 0.5cm 2 , the flow rate of CO2 is 0.05mL / min.

[0013] Beneficial effects:

[0014] Compared with the prior art, the present invention is a lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis, which uses bismuth oxyhalide / carbon paper with a layered crystal structure as a photoelectric cathode and an organic ether solvent with added halogen lithium salt as an electrolyte to enhance the light-assisted lithium carbon dioxide battery. As a p-type semiconductor, bismuth oxyhalide substances produce abundant electron-hole pairs under the action of the light field, which significantly reduces the difficulty of the formation and decomposition of Li2CO3 during the charge and discharge process. Due to the incorporation of halogen lithium salts in the electrolyte, the photoelectric cathode is more likely to react with holes at the solid-liquid interface. The more significant photocurrent response of the Bi5O7I photoelectric cathode and lithium iodide can be attributed to the more densely separated photocharges, indicating that the holes are more likely to react with I -The photoelectric cathode can work stably and continuously. In addition, the halogen lithium salt also helps to separate the charge carriers. Therefore, the light-assisted lithium carbon dioxide battery maintains a low overpotential throughout the cycle. The lithium carbon dioxide battery using Bi5O7I photoelectric cathode has a current density of 0.01mAcm -2 Under the light condition, it shows an ultra-high discharge voltage platform of 3.05V, which exceeds the equilibrium potential of product formation (2.80Vvs. Li + / Li), indicating that light energy is continuously output as electrical energy. Compared with batteries without lithium iodide, the solid-liquid synergistic light-assisted battery showed no efficiency drop even after 20 cycles. This shows that the complementary advantages of the two catalysts can significantly improve the lifespan and stability of the photocathode, reduce the overpotential of lithium-carbon dioxide batteries, and improve the electrochemical performance and cycle stability of the battery, showing good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the structure of Bi5O7I crystal;

[0016] Figure 2 This is a scanning electron microscope image of Bi5O7I;

[0017] Figure 3 is the X-ray diffraction pattern of Bi5O7I;

[0018] Figure 4 Schematic diagram of the energy barrier of lithium carbon dioxide batteries with different compositions under different conditions, wherein (a) is Comparative Example 1, (b) is Comparative Example 2, and (c) is Example 3;

[0019] Figure 5 It curves of lithium carbon dioxide batteries with and without lithium iodide under light-dark cycle irradiation;

[0020] Figure 6 The cycle performance of the photovoltaic auxiliary cell without adding LiI (the cell assembled in Comparative Example 1);

[0021] Figure 7 The cycling performance of the photovoltaic auxiliary cell with added LiI (the cell assembled in Example 3);

[0022] Figure 8 The material of Example 3 has a high sensitivity and low power consumption. -2 The cycle curve below;

[0023] Figure 9 The rate performance of the lithium carbon dioxide battery at different current densities under the conditions of illumination and no illumination for the material of Example 3;

[0024] Figure 10 The overpotential of the lithium carbon dioxide battery at different current densities with and without illumination for the material of Example 3;

[0025] Figure 11 The Bi5O7I photoelectric anode light-assisted battery assembled in Comparative Example 1 was 0.01 mA cm -2 Discharge and charge curves of the battery under no light conditions;

[0026] Figure 12 This is a cycle performance diagram of the battery assembled in Comparative Example 2;

[0027] Figure 13 This is a graph showing the cycle performance of the battery assembled in Comparative Example 3. DETAILED DESCRIPTION

[0028] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0029] Example 1 Preparation of positive electrode material

[0030] 4.85g of Bi(NO₃)₃·5H₂O and 1.20g of NaOH were dissolved in 50mL of distilled water to form a white mixture, designated Mixture 1A. Then, 4mL of a 1 mol / L KI solution was added to Mixture 1A and stirred for 30 minutes. This mixture was designated Mixture 1B. Mixture 1B was placed in a 100mL Teflon-lined stainless steel autoclave and heated at 180°C for 24 hours. After cooling to room temperature, the precipitate was collected by centrifugation, washed three times with deionized water and three times with ethanol, and dried at 60°C for 24 hours.

[0031] Figure 1 and Figure 2 The schematic diagram and SEM image of the Bi5O7I photoelectric cathode structure with layered crystal structure prepared in Example 1 of the present invention are respectively. Figure 2 It can be seen that [Bi2O2] 2+ The layers are alternately formed with double halogen layers to form Bi5O7I, and the electrode sheet has a diameter of 11 mm.

[0032] Figure 3 This is the XRD pattern of the Bi5O7I photoelectric cathode electrode sheet with a layered crystal structure prepared in Example 1 of the present invention. As can be seen from the figure, the XRD pattern of the Bi5O7I photoelectric cathode electrode sheet with a layered crystal structure prepared in Example 1 is consistent with the standard card, proving that Bi5O7I was successfully synthesized.

[0033] Bi5O7I was mixed with a polyvinylidene fluoride binder (PVDF) and Ketjen Black in an n-methyl-2-pyrrolidone liquid. The mass ratio of the active material Bi5O7I to PVDF and Ketjen Black was 8:1:1. The slurry was evenly coated on a carbon paper disk and dried in a vacuum drying oven at 120°C for 12 hours to obtain a bismuth oxyhalide photoelectric cathode Bi5O7I / CP.

[0034] Example 2 Preparation of electrolyte

[0035] Measure 2 mL of 1 M lithium bis(trifluoromethanesulfonyl)imide-1,3-epoxypentane electrolyte into a glass bottle; then weigh 0.0134 g of anhydrous potassium iodide powder and add it to the above electrolyte, stir thoroughly to dissolve, and then obtain the electrolyte.

[0036] Example 3

[0037] The positive electrode of Example 1, 100 μL of the electrode solution prepared in Example 2, and lithium foil were used as the negative electrode. A glass fiber separator with a pore size of 2.7 μm and a diameter of 19 mm was used. Swagelok-type cells were assembled in a glove box with a high-purity carbon dioxide atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm).

[0038] The Swagelok type cell has an air cavity and a transparent window to ensure sufficient light exposure. The cut Bi5O7X / CP photoelectric cathode area is 1.13cm 2 , and the effective lighting area is 0.5cm 2 All cycling performance tests were conducted on a Land-CT3001A battery test system, with a constant current discharge / charge cycle at a fixed flow rate of 0.05 ml / min CO2. The illumination source used was a 300 W xenon lamp (MC-PF300C, MerryChange, China), providing light energy in the wavelength range of 280–750 nm. The illumination intensity on the Bi5O7I / CP electrode surface was 100 mW cm -2 , potential range is 2.2-5.0V vs.Li / Li + .

[0039] Figure 8 In order to utilize the lithium carbon dioxide battery of Example 3 in which a homogeneous and heterogeneous synergistic catalysis is used with and without a power density of about 100 mW cm -2The cycle life diagram under the condition of a xenon lamp as the light source. Under 250h of illumination, the lithium carbon dioxide battery still shows outstanding cycle stability without increasing polarization. This is because in the presence of the redox medium, the battery has a very stable photoelectric cathode and continuous separation of photogenerated electrons and holes. The lithium carbon dioxide battery can still be stably charged and discharged after 125 cycles, further indicating that the redox medium (LiI) can still participate in the reaction without being deactivated. Combined with the information in the figure, it can be seen that the present invention can significantly improve the cycle stability of the lithium carbon dioxide battery through the synergistic effect of two catalysts (LiI and Bi5O7I) under the influence of light, indicating that there is a good reversible reaction inside the battery and accelerating the reaction kinetics rate of the CO2 oxidation / reduction reaction in the battery.

[0040] Figure 9 and Figure 10 The results show that the -2 Rate performance and overpotential at different current densities. In the entire current density range, the overpotential of the light field is much lower than that of the dark field. In fact, in the discharge state, at 0.1 mA cm -2 At a current density of 0.5 mA cm, the potential of the lithium carbon dioxide battery is lower than 2.0 V. -2 When the current density decreases to 0.01 mAh cm, the battery loses its function, while the discharge potential of the light-assisted lithium-carbon dioxide battery can still be maintained at 2.5 V and the charging potential is lower than 4.0 V. -2 The voltage can also recover to the level of the initial five cycles, indicating that the battery has good rate performance. The repeatability of the charge and discharge potential and the continuous photoresponsivity indicate that the electrons and holes generated by light can accelerate the CO2RR / CO2ER process under illumination.

[0041] Example 4

[0042] The difference between this embodiment and embodiment 1 is that the added halogen element is Br.

[0043] Example 5

[0044] The difference from Example 1 is that the added halogen elements are all Cl.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that a conventional 1,3-epoxypentane electrolyte containing only bis(trifluoromethanesulfonyl)imide lithium and no halogen lithium salt is used as the battery electrolyte. The battery was assembled according to the method of Example 3 and the performance test was carried out. The results are as follows: Figure 6 and Figure 11 shown.

[0047] Figure 5 The It curves of lithium-carbon dioxide batteries with and without lithium iodide under light-dark cycle irradiation are shown in Figure 2. The carrier recombination rate can be analyzed from the figure. The photocurrent response of Bi5O7I photoanode with lithium iodide is more significant, which can be attributed to the denser separation of photocharges, indicating that holes are more likely to react with I - The photoelectric cathode can react instead of recombining with electrons, thus enabling the photoelectric cathode to work stably and continuously.

[0048] Figure 6 and Figure 11 The first discharge and charge curves of the lithium carbon dioxide battery prepared in comparative example 1 under conditions with and without light. The lithium carbon dioxide battery using Bi5O7I photoelectric positive electrode at a current density of 0.01 mA cm -2 Under the light condition, it shows an ultra-high discharge voltage platform of 3.05V, which exceeds the equilibrium potential of product formation (2.80V vs. Li + / Li), indicating that light energy is continuously output as electrical energy, while in the dark it is only 2.65V. During reverse charging, the light-induced charging voltage dropped to 3.25V, 1.05V lower than 4.30V, indicating that the participation of photoinduced holes reduces the battery's electrical energy input, achieving an energy efficiency of 93.8%, significantly higher than the 61.6% in the dark. Figure 7 The cycling performance of the LiI-added photovoltaic-assisted cell (Example 3) shows no decrease in efficiency even after 20 cycles compared to a cell without lithium iodide. This further demonstrates that the complementary advantages of the two catalysts in this invention can significantly improve the lifespan and stability of the photovoltaic anode, reduce the overpotential of the lithium-carbon dioxide cell, and enhance the cell's electrochemical performance and cycling stability.

[0049] Comparative Example 2

[0050] The difference from Example 1 is that conventional carbon nanotube film purchased from Suzhou JEDI Nanotechnology Co., Ltd. is used as the positive electrode. The battery is assembled according to the method of Example 3 and the performance test is carried out. The results are as follows: Figure 12 shown.

[0051] As can be seen from the figure, when only LiI is used as a heterogeneous catalyst, the battery's first cycle charge and discharge overpotential exceeds 1.6V. As the number of cycles increases, the battery quickly becomes polarized, seriously affecting the battery's cycle stability and life.

[0052] Figure 4Schematic diagram of the energy barrier of lithium carbon dioxide batteries under different conditions using batteries assembled using Comparative Example 1, Comparative Example 2, and Example 3. As can be seen from the figure, the energy barrier of the lithium carbon dioxide battery in Comparative Example 1 that does not contain a redox medium will increase as the photoelectric cathode fails, making battery operation increasingly difficult; the energy barrier of the lithium carbon dioxide battery in Comparative Example 2 that contains a redox medium but no photoelectric cathode is very high, making battery operation difficult; the energy barrier of the lithium carbon dioxide battery in Example 3 that contains both a redox medium and a photoelectric cathode is greatly reduced, and there is no obvious change as the battery operates, and the battery performance is significantly improved.

[0053] Comparative Example 3

[0054] The difference from Example 1 is that a conventional carbon nanotube film purchased from Suzhou JEDI Nanotechnology Co., Ltd. is used as the positive electrode, and a conventional 1,3-epoxypentane electrolyte containing only bis(trifluoromethanesulfonyl)imide lithium and no halogen lithium salt is used as the battery electrolyte. The battery was assembled according to the method of Example 3 and the performance test was carried out. The results are as follows: Figure 13 shown.

[0055] As can be seen from the figure, the battery prepared in Comparative Example 3 experiences rapid polarization after more than 30 cycles. This is due to the accumulation of lithium carbonate, a difficult-to-decompose discharge product, at the positive electrode, leading to significant degradation of battery performance. After 40 cycles, the charging platform exceeds 4.5V, with an overpotential of approximately 2V, indicating a significant decline in battery performance.

[0056] In summary, the bismuth oxyhalide substances selected in the present invention as p-type semiconductors generate abundant electron-hole pairs under the action of the light field, which significantly reduces the difficulty of the formation and decomposition of Li2CO3 during the charge and discharge process. With the incorporation of halogen lithium salts, the photocathode is more likely to react with holes at the solid-liquid interface. The photocurrent response of the Bi5O7I photocathode to lithium iodide is more significant, so that the photocathode can work stably and continuously. In addition, halogen lithium salts also contribute to carrier separation. Compared with batteries that do not contain lithium iodide, the solid-liquid collaborative light-assisted battery does not show a decrease in efficiency even after 20 cycles. This shows that the complementary advantages of the two catalysts can significantly improve the life and stability of the photocathode, reduce the overpotential of the lithium carbon dioxide battery, improve the electrochemical performance and cycle stability of the battery, and have good application prospects.

[0057] The above description is merely a specific embodiment of the present application. Any person skilled in the art may easily conceive of variations or substitutions within the technical scope disclosed in this application, and such variations or substitutions shall be within the scope of protection of this application. The scope of protection of this application shall be subject to the scope of protection of the claims.

Claims

1. A lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis, comprising a positive electrode, a separator, a negative electrode and an electrolyte, characterized in that: The positive electrode is a bismuth oxyhalide photoelectric positive electrode Bi5O7X / CP, the electrolyte is an organic ether electrolyte added with a lithium salt, and the negative electrode is a lithium foil, wherein the lithium salt includes lithium bistrifluoromethanesulfonyl imide with a final concentration of 1 mol / L and LiX with a final concentration of 0.05 mol / L, and X is Cl, Br or I.

2. A lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis according to claim 1, characterized in that: The diaphragm is a glass fiber diaphragm GF / D.

3. The lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis according to claim 1, characterized in that: The organic ether electrolyte comprises a mixture of one or more of epoxypentane, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

4. The lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis according to claim 1, characterized in that: The bismuth oxyhalide photoelectric positive electrode Bi5O7X / CP is prepared by mixing the active material Bi5O7X, polyvinylidene fluoride binder PVDF and Ketjen Black in a mass ratio of 8:1:1 and adding them to an n-methyl-2-pyrrolidone liquid to form a uniform slurry. The slurry is then coated on a carbon paper disc and dried in a vacuum drying oven at 120°C for 12 hours.

5. The lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis according to claim 1, characterized in that: The preparation method of Bi5O7X is as follows: Bi(NO3)3·5H2O and NaOH are dissolved in distilled water to form a white mixture; KX solution is then added to the white mixture, stirred for 30 minutes, heated at 180°C for 24 hours, cooled to room temperature, and centrifuged to collect the precipitate. After washing with deionized water and ethanol three times respectively, the precipitate is dried in a drying oven at 60°C.

6. The lithium carbon dioxide battery with homogeneous and heterogeneous synergistic catalysis according to claim 1, characterized in that: The working environment of the homogeneous and heterogeneous synergistic catalytic lithium carbon dioxide battery is as follows: the area of ​​the tailored bismuth oxyhalide photoelectric cathode Bi5O7X / CP is 1.13 cm 2 , and the effective lighting area is 0.5 cm 2 , the flow rate of CO2 is 0.05 mL / min.

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