A photoelectric positive electrode for a light-assisted lithium-air battery, a preparation method thereof, and a light-assisted lithium-air battery

Abstract

The present invention belongs to the technical field of metal-air batteries, and provides a light-assisted lithium-air battery photoelectric positive electrode, a preparation method thereof, and a light-assisted lithium-air battery. The present invention adopts nickel-doped α-ferric oxide nanospheres, conductive carbon black, and a binder to prepare a porous coating and applies it to a conductive current collector. Under light conditions, nickel-doped α-ferric oxide nanospheres are used to absorb light energy to achieve the separation of photogenerated electrons and holes. During the charging reaction, the photogenerated electrons can be transmitted to the lithium negative electrode through an external circuit and combined with lithium ions for deposition. At the same time, the photogenerated holes oxidize lithium peroxide to promote its decomposition into oxygen, reduce the battery charging overpotential, and alleviate the occurrence of side reactions, thereby improving the charge and discharge efficiency and cycle stability of the lithium-air battery. The results of the embodiment show that the lithium-air battery assembled with the light-assisted lithium-air battery photoelectric positive electrode provided by the present invention has a first cycle overpotential of 0.73V under light conditions.

Description

Technical Field

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

[0002] With the rapid development of new energy electric vehicles, people are increasingly demanding high-energy-density secondary batteries. Among the many secondary battery systems, lithium-air batteries are considered to have good application prospects in the field of future power batteries due to their ultra-high theoretical energy density (3860mAh / g). However, the discharge product of lithium-air batteries, lithium peroxide, is insulating and insoluble in organic electrolytes, which leads to slow reaction kinetics of its formation and decomposition process, causing the battery to exhibit a high battery reaction overpotential. High overpotential can cause the occurrence of side reactions related to electrolyte decomposition, resulting in a shortened battery cycle life, which restricts the practical application of lithium-air batteries. Recently, designing light-assisted lithium-air batteries is considered to be an effective method to improve the above-mentioned problems of lithium-air batteries. As the core of light-assisted lithium-air batteries, the photocathode plays a key role in the electrochemical performance of light-assisted lithium-air batteries. Therefore, how to prepare high-performance photocathode and thus improve the electrochemical performance of light-assisted lithium-air batteries has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0003] The purpose of the present invention is to provide a light-assisted lithium-air battery photoelectric cathode and a preparation method thereof and a light-assisted lithium-air battery. The light-assisted lithium-air battery photoelectric cathode provided by the present invention has excellent catalytic effect, promotes the formation and decomposition process of lithium peroxide, and reduces the battery charging overpotential.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a photoelectric positive electrode for a light-assisted lithium-air battery, comprising a conductive current collector and a porous coating coated on either side of the conductive current collector; the porous coating comprises nickel-doped α-ferric oxide nanospheres, conductive carbon black and a binder.

[0006] Preferably, the coating amount of the porous coating is 0.2 to 2.0 mg / cm 2 .

[0007] Preferably, the mass ratio of the nickel-doped α-ferric oxide nanospheres, the conductive carbon black and the binder is (1-3):(6-8):1.

[0008] Preferably, the conductive carbon black includes one or two of Ketjen black, acetylene black, carbon nanotubes and graphene; and the binder includes polyvinylidene fluoride.

[0009] Preferably, the diameter of the nickel-doped α-ferric oxide nanospheres is 200-300 nm.

[0010] Preferably, the preparation method of the nickel-doped α-ferric oxide nanospheres comprises: mixing potassium ferrocyanide, diammonium hydrogen phosphate, a nickel source and water, performing a hydrothermal reaction, and then washing and drying the mixture by centrifugation to obtain nickel-doped α-ferric oxide nanospheres.

[0011] Preferably, the molar ratio of the potassium ferrocyanide, diammonium hydrogen phosphate and nickel source is (2.5-3): 1: (0.25-0.9).

[0012] Preferably, the temperature of the hydrothermal reaction is 180-200° C., and the time of the hydrothermal reaction is 5-40 hours.

[0013] The present invention provides a method for preparing the photoelectric cathode of a light-assisted lithium-air battery described in the above technical solution, comprising the following steps:

[0014] (1) mixing nickel-doped α-ferric oxide nanospheres, conductive carbon black, a binder, and a slurry to obtain a coating slurry;

[0015] (2) coating the coating slurry obtained in step (1) on either side of a conductive current collector, and drying the coating slurry to obtain a photoelectric positive electrode for a light-assisted lithium-air battery.

[0016] The present invention also provides a light-assisted lithium-air battery, comprising the light-assisted lithium-air battery photoelectric cathode described in the above technical solution or the light-assisted lithium-air battery photoelectric cathode prepared by the above preparation method, an electrolyte, a diaphragm and a lithium sheet.

[0017] The present invention provides a photoelectric positive electrode for a light-assisted lithium-air battery, comprising a conductive current collector and a porous coating applied to either side of the conductive current collector; the porous coating comprises nickel-doped α-ferric oxide nanospheres, conductive carbon black, and a binder. The porous coating is prepared using nickel-doped α-ferric oxide nanospheres, conductive carbon black, and a binder and applied to the conductive current collector. Under illumination, the nickel-doped α-ferric oxide nanospheres absorb light energy, separating photogenerated electrons from holes. During the charging reaction, the photogenerated electrons can be transmitted through an external circuit to the lithium negative electrode, where they combine with lithium ions for deposition. Simultaneously, the photogenerated holes oxidize lithium peroxide, promoting its decomposition into oxygen. This reduces the battery's charge overpotential and mitigates side reactions, thereby improving the charge and discharge efficiency and cycle stability of the lithium-air battery. The nickel-doped α-Fe2O3 nanospheres used in the present invention increase their defect states due to nickel doping, regulating the material's bandgap. This helps enhance the photocathode's catalytic effect on battery reactions, boosting its photoelectrocatalytic activity and promoting the formation and decomposition of lithium peroxide during battery cycling, thereby alleviating the high overpotential of lithium-air batteries. Results from the examples show that a lithium-air battery assembled using the light-assisted lithium-air battery photocathode provided by the present invention achieved a first-cycle overpotential of 0.73V under illumination. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the XRD pattern of nickel-doped α-ferric oxide nanospheres prepared in Example 1 of the present invention;

[0019] Figure 2 This is a SEM image of nickel-doped α-ferric oxide nanospheres prepared in Example 1 of the present invention;

[0020] Figure 3 TEM image of nickel-doped α-ferric oxide nanospheres prepared in Example 1 of the present invention;

[0021] Figure 4 This is a SEM image of the photoelectric cathode of the light-assisted lithium-oxygen battery in Example 1 of the present invention;

[0022] Figure 5 The first charge and discharge curves of the button batteries prepared in Application Example 1 of the present invention and Comparative Application Example 1 are shown. DETAILED DESCRIPTION

[0023] The present invention provides a photoelectric positive electrode for a light-assisted lithium-air battery, comprising a conductive current collector and a porous coating coated on either side of the conductive current collector; the porous coating comprises nickel-doped α-ferric oxide nanospheres, conductive carbon black and a binder.

[0024] The photoelectric cathode of a light-assisted lithium-air battery provided by the present invention comprises a conductive current collector and a porous coating applied on either side of the conductive current collector. By applying the porous coating on either side of the conductive current collector, the present invention enhances the photoelectrocatalytic activity of the photoelectrochemical cathode, promotes the formation and decomposition of lithium peroxide during battery cycling, and alleviates the high overpotential problem of lithium-air batteries.

[0025] In the present invention, the conductive current collector preferably comprises carbon paper, nickel foam or carbon cloth, more preferably carbon paper or carbon cloth. The present invention has no particular limitation on the source of the conductive current collector, and commercially available products known to those skilled in the art can be used.

[0026] In the present invention, the coating amount of the porous coating is preferably 0.2 to 2.0 mg / cm 2 , more preferably 0.8 to 1.0 mg / cm 2 The present invention preferably controls the coating amount of the porous coating within the above range. Too little coating amount of the porous coating is not conducive to the generation and storage of a large amount of discharge products. Too much coating amount of the porous coating will hinder the transmission of electrons and ions and is not conducive to sufficient infiltration of the electrolyte.

[0027] In the present invention, the porous coating comprises nickel-doped α-ferric oxide nanospheres, conductive carbon black, and a binder. The present invention utilizes nickel-doped α-ferric oxide nanospheres, conductive carbon black, and a binder to form a porous coating. The nickel-doped α-ferric oxide nanospheres absorb light energy, achieving separation of photogenerated electrons and holes. During the charging reaction, the photogenerated electrons can be transmitted through an external circuit to the lithium negative electrode, combining with lithium ions for deposition. Simultaneously, the photogenerated holes oxidize lithium peroxide, promoting its decomposition into oxygen, reducing the battery's charge overpotential and mitigating side reactions, thereby improving the charge and discharge efficiency and cycle stability of the lithium-air battery.

[0028] In the present invention, the mass ratio of the nickel-doped α-ferric oxide nanospheres, conductive carbon black, and binder is preferably (1-3): (6-8): 1, and more preferably (2-3): (7-8): 1. In the present invention, the mass ratio of the nickel-doped α-ferric oxide nanospheres, conductive carbon black, and binder is preferably controlled within the above range, which is beneficial for obtaining a photoelectric cathode with excellent conductivity, catalyticity, and stability.

[0029] In the present invention, the conductive carbon black preferably includes one or two of Ketjen black, acetylene black, carbon nanotubes, and graphene, and more preferably includes one or two of Ketjen black, acetylene black, and graphene. The present invention does not particularly limit the source of the conductive carbon black; commercially available products familiar to those skilled in the art may be used.

[0030] In the present invention, the binder preferably comprises polyvinylidene fluoride. The present invention has no particular limitation on the source of the binder, and commercially available products well known to those skilled in the art can be used.

[0031] In the present invention, the diameter of the nickel-doped α-ferric oxide nanospheres is preferably 200-300 nm, more preferably 250-300 nm. The present invention preferably uses nickel-doped α-ferric oxide nanospheres within the above diameter range, which is conducive to exposing more active sites.

[0032] In the present invention, the structure of the nickel-doped α-ferric oxide nanospheres is preferably a core-shell structure. In the present invention, the core-shell structure of the nickel-doped α-ferric oxide nanospheres is conducive to the diffusion of oxygen, the transmission of lithium ions and the storage of discharge products.

[0033] In the present invention, the method for preparing nickel-doped α-ferric oxide nanospheres preferably comprises: mixing potassium ferrocyanide, diammonium hydrogen phosphate, a nickel source and water, performing a hydrothermal reaction, and then washing by centrifugation and drying to obtain nickel-doped α-ferric oxide nanospheres.

[0034] The present invention does not specifically limit the mixing process of the potassium ferrocyanide, diammonium hydrogen phosphate, nickel source, and water; any solid-liquid mixing method known to those skilled in the art may be employed. In the present invention, the mixing is preferably performed under stirring. In the present invention, the stirring speed is preferably 350 to 400 rpm; the stirring time is preferably 1 to 1.5 hours; and the stirring method is preferably magnetic stirring.

[0035] In the present invention, the molar ratio of potassium ferrocyanide, diammonium hydrogen phosphate and nickel source is preferably (2.5-3):1:(0.25-0.9), more preferably (2.5-2.8):1:(0.25-0.8).

[0036] In the present invention, the nickel source preferably includes nickel chloride or nickel nitrate. The present invention has no particular limitation on the source of the nickel source, and commercially available products known to those skilled in the art can be used.

[0037] In the present invention, the volume ratio of the water to the mass ratio of potassium ferricyanide is preferably 30 mL:0.148 g. In the present invention, the water is preferably distilled water.

[0038] In the present invention, the temperature of the hydrothermal reaction is preferably 180-200° C. In the present invention, the temperature of the hydrothermal reaction is preferably controlled within the above range, which is conducive to obtaining nickel-doped α-ferric oxide nanospheres with a core-shell structure and uniform particle size.

[0039] In the present invention, the hydrothermal reaction time is preferably 5 to 40 hours, more preferably 20 to 30 hours. In the present invention, as the hydrothermal reaction time increases, the crystal phase transforms from amorphous to polycrystalline, and the obtained nickel-doped α-ferric oxide nanospheres have good photoelectrocatalytic performance.

[0040] The centrifugal washing and drying operations are not particularly limited in the present invention; they can be performed using technical solutions familiar to those skilled in the art. In the present invention, the detergents used in the centrifugal washing are preferably distilled water and ethanol. In the present invention, the drying temperature is preferably 60-70°C; the drying time is preferably 12-14 hours; and the drying equipment is preferably a vacuum drying oven.

[0041] The present invention adopts nickel-doped α-iron sesquioxide nanospheres, conductive carbon black and binder to prepare a porous coating and apply it to a conductive current collector. Under light conditions, the nickel-doped α-iron sesquioxide nanospheres absorb light energy to achieve the separation of photogenerated electrons and holes. During the charging reaction, the photogenerated electrons can be transmitted to the lithium negative electrode through an external circuit and combined with lithium ions to deposit. At the same time, the photogenerated holes oxidize lithium peroxide to promote its decomposition into oxygen, reduce the battery charging overpotential, and alleviate the occurrence of side reactions, thereby improving the charge and discharge efficiency and cycle stability of the lithium-air battery. The nickel-doped α-iron sesquioxide nanospheres used in the present invention can increase the defect state of the α-iron sesquioxide nanospheres due to nickel doping, regulate the band gap width of the material, help to improve the catalytic effect of the photoelectric positive electrode on the battery reaction, enhance the photoelectric catalytic activity of the photoelectric positive electrode, promote the formation and decomposition of lithium peroxide during the battery cycle, and improve the problem of high overpotential of the lithium-air battery.

[0042] The present invention provides a method for preparing the photoelectric cathode of a light-assisted lithium-air battery described in the above technical solution, comprising the following steps:

[0043] (1) mixing nickel-doped α-ferric oxide nanospheres, conductive carbon black, a binder, and a slurry to obtain a coating slurry;

[0044] (2) coating the coating slurry obtained in step (1) on either side of a conductive current collector, and drying the coating slurry to obtain a photoelectric positive electrode for a light-assisted lithium-air battery.

[0045] The invention mixes nickel-doped alpha-ferric oxide nanospheres, conductive carbon black, a binder and slurry to obtain coating slurry.

[0046] The present invention does not specifically limit the method for mixing the nickel-doped α-ferric oxide nanospheres, conductive carbon black, binder, and slurry; any solid-liquid mixing method known to those skilled in the art can be employed. In the present invention, the mixing is preferably performed by ball milling. The ball milling speed is preferably 350-400 rpm, and the ball milling time is preferably 20-25 hours.

[0047] In the present invention, the slurry is preferably N-methylpyrrolidone. The amount of the slurry used is preferably 1-3% of the total mass of the nickel-doped α-ferric oxide nanospheres, conductive carbon black, and binder. The source of the slurry is not particularly limited, and commercially available products known to those skilled in the art can be used.

[0048] After obtaining the coating slurry, the present invention applies the coating slurry on either side of a conductive current collector, and obtains a photoelectric positive electrode of a light-assisted lithium-air battery after drying.

[0049] The present invention has no particular limitation on the coating method, and any coating method well known to those skilled in the art may be used.

[0050] In the present invention, the drying temperature is preferably 120-130° C.; the drying time is preferably 12-14 hours; and the drying equipment is preferably a vacuum drying oven.

[0051] The present invention also provides a light-assisted lithium-air battery, comprising the photoelectric cathode described in the above technical solution or the photoelectric cathode prepared by the above preparation method, an electrolyte, a separator, and a lithium sheet. The light-assisted lithium-air battery provided by the present invention has good charge and discharge efficiency and cycle stability.

[0052] In the present invention, the electrolyte preferably comprises 1M lithium perchlorate / dimethyl sulfoxide (LiClO4) / DMSO, 1M lithium trifluoromethanesulfonate / tetraethylene glycol dimethyl ether (LiCF3SO3) / TEGDM, or 1M lithium bis(trifluoromethanesulfonyl)imide / tetraethylene glycol dimethyl ether (LiTFSI) / TEGDME; the separator preferably comprises a glass fiber separator; and the lithium sheet preferably has a thickness of 0.6 mm. The sources of the electrolyte, separator, and lithium sheet are not particularly limited; commercially available products known to those skilled in the art may be used.

[0053] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0054] Example 1

[0055] The photoelectric cathode of a light-assisted lithium-air battery is composed of carbon paper and a porous coating coated on either side of the carbon paper. The porous coating is composed of nickel-doped α-ferric oxide nanospheres, Ketjen black, and polyvinylidene fluoride in a mass ratio of 3:6:1. The coating amount of the porous coating is 0.8 mg / cm 2 , the diameter of nickel-doped α-Fe2O3 nanospheres is 250nm, and the structure is a core-shell structure;

[0056] The preparation process of nickel-doped α-Fe2O3 nanospheres is as follows:

[0057] S1: Place 0.148 g of potassium ferrocyanide, 0.023 g of diammonium hydrogen phosphate, and 0.013 g of nickel nitrate in a beaker (the molar ratio of potassium ferrocyanide, diammonium hydrogen phosphate, and nickel nitrate is 2.59:1:0.41), add 30 mL of distilled water, and stir magnetically at 350 rpm for 1 h to obtain a clear solution;

[0058] S2: The clear solution obtained in S1 was transferred to a 50 mL polytetrafluoroethylene liner and subjected to a hydrothermal reaction in a reactor at 200°C. After the reaction for 30 h, the mixture was cooled to room temperature. The reaction product was then centrifuged and washed with distilled water and ethanol, and then dried in a vacuum drying oven at 60°C for 12 h to obtain nickel-doped α-ferric oxide nanospheres, which were designated as Ni@α-Fe2O3 nanospheres.

[0059] The preparation process of the photoelectric cathode of light-assisted lithium-air battery is as follows:

[0060] (1) Ni@α-Fe2O3 nanospheres, Ketjen black, and polyvinylidene fluoride were mixed, and N-methylpyrrolidone accounting for 1% of the total mass of Ni@α-Fe2O3 nanospheres, Ketjen black, and polyvinylidene fluoride was added, followed by ball milling at 350 rpm for 20 h to obtain a coating slurry;

[0061] (2) The coating slurry obtained in step (1) is applied on one side of the carbon paper. The coating amount of the slurry on the carbon paper is 0.8 mg / cm 2 , and then dried in a vacuum drying oven at 120 ° C for 12 h to obtain a light-assisted lithium oxygen battery photoelectric cathode.

[0062] Figure 1 The XRD pattern of Ni@α-Fe2O3 nanospheres prepared in this example. Figure 1 It can be seen that the diffraction peaks of the Ni@α-Fe2O3 nanospheres synthesized in this example are consistent with the α-Fe2O3 standard card (JCPDS No.33-0664), and no other impurity phases appear, indicating that Ni atoms are embedded in the α-Fe2O3 lattice.

[0063] Figure 2 This is the SEM image of the Ni@α-Fe2O3 nanospheres prepared in this example. Figure 2 It can be seen that the Ni@α-Fe2O3 sample synthesized in this example is uniformly spherical.

[0064] Figure 3 This is the TEM image of Ni@α-Fe2O3 nanospheres prepared in this example. Figure 3 It can be seen that the Ni@α-Fe2O3 nanospheres synthesized in this example are a core-shell structure, and the diameter of the nanospheres is about 250 nm.

[0065] Figure 4 The SEM image of the photoelectric positive electrode of the light-assisted lithium oxygen battery in this embodiment is shown in FIG. Figure 4 It can be seen that the porous coating coated on the surface of the photoelectric positive electrode provided in this embodiment is composed of uniformly distributed Ni@α-Fe2O3 nanospheres and Ketjen black, wherein the spherical particles are Ni@α-Fe2O3 nanospheres and the small particles are Ketjen black.

[0066] Example 2

[0067] The photoelectric cathode of a light-assisted lithium-air battery is composed of carbon paper and a porous coating coated on either side of the carbon paper. The porous coating is composed of nickel-doped α-ferric oxide nanospheres, Ketjen black, and polyvinylidene fluoride in a mass ratio of 2:7:1. The coating amount of the porous coating is 0.8 mg / cm 2 , the diameter of nickel-doped α-Fe2O3 nanospheres is 250nm, and the structure is a core-shell structure;

[0068] The preparation process of nickel-doped α-Fe2O3 nanospheres is as follows:

[0069] S1: Place 0.148 g of potassium ferrocyanide, 0.023 g of diammonium hydrogen phosphate, and 0.011 g of nickel chloride in a beaker (the molar ratio of potassium ferrocyanide, diammonium hydrogen phosphate, and nickel chloride is 2.59:1:0.48), add 30 mL of distilled water, and stir magnetically at 350 rpm for 1 h to obtain a clear solution;

[0070] S2: The clear solution obtained in S1 was transferred to a 50 mL polytetrafluoroethylene liner and subjected to a hydrothermal reaction in a reactor at 200°C. After the reaction for 30 h, the mixture was cooled to room temperature. The reaction product was then centrifuged and washed with distilled water and ethanol, and then dried in a vacuum drying oven at 60°C for 12 h to obtain nickel-doped α-ferric oxide nanospheres, which were designated as Ni@α-Fe2O3 nanospheres.

[0071] The preparation process of the photoelectric cathode of light-assisted lithium-air battery is as follows:

[0072] (1) Ni@α-Fe2O3 nanospheres, Ketjen black, and polyvinylidene fluoride were mixed, and N-methylpyrrolidone accounting for 1% of the total mass of Ni@α-Fe2O3 nanospheres, Ketjen black, and polyvinylidene fluoride was added, followed by ball milling at 350 rpm for 20 h to obtain a coating slurry;

[0073] (2) The coating slurry obtained in step (1) is applied on one side of the carbon paper. The coating amount of the slurry on the carbon paper is 0.8 mg / cm 2 , and then dried in a vacuum drying oven at 120 ° C for 12 h to obtain a light-assisted lithium oxygen battery photoelectric cathode.

[0074] Example 3

[0075] The photoelectric cathode of a light-assisted lithium-air battery is composed of carbon paper and a porous coating coated on either side of the carbon paper. The porous coating is composed of nickel-doped α-ferric oxide nanospheres, Ketjen black, and polyvinylidene fluoride in a mass ratio of 3:6:1. The coating amount of the porous coating is 0.8 mg / cm 2 , the diameter of nickel-doped α-Fe2O3 nanospheres is 250nm, and the structure is a core-shell structure;

[0076] The preparation process of nickel-doped α-Fe2O3 nanospheres is as follows:

[0077] S1: Place 0.148 g of potassium ferrocyanide, 0.023 g of diammonium hydrogen phosphate, and 0.013 g of nickel nitrate in a beaker (the molar ratio of potassium ferrocyanide, diammonium hydrogen phosphate, and nickel nitrate is 2.59:1:0.41), add 30 mL of distilled water, and stir magnetically at 350 rpm for 1 h to obtain a clear solution;

[0078] S2: The clear solution obtained in S1 was transferred to a 50 mL polytetrafluoroethylene liner and subjected to a hydrothermal reaction in a reactor at 200°C. After reacting for 20 h, the mixture was cooled to room temperature. The reaction product was then centrifuged and washed with distilled water and ethanol, and then dried in a vacuum drying oven at 60°C for 12 h to obtain nickel-doped α-ferric oxide nanospheres, which were designated as Ni@α-Fe2O3 nanospheres.

[0079] The preparation process of the photoelectric cathode of light-assisted lithium-air battery is as follows:

[0080] (1) Ni@α-Fe2O3 nanospheres, Ketjen black, and polyvinylidene fluoride were mixed, and N-methylpyrrolidone accounting for 1% of the total mass of Ni@α-Fe2O3 nanospheres, Ketjen black, and polyvinylidene fluoride was added, followed by ball milling at 350 rpm for 20 h to obtain a coating slurry;

[0081] (2) The coating slurry obtained in step (1) is applied on one side of the carbon paper. The coating amount of the slurry on the carbon paper is 0.8 mg / cm 2, and then dried in a vacuum drying oven at 120 ° C for 12 h to obtain a light-assisted lithium oxygen battery photoelectric cathode.

[0082] Comparative Example 1

[0083] (1) Ketjen black and polyvinylidene fluoride were mixed in a mass ratio of 9:1, N-methylpyrrolidone accounting for 1% of the total mass of Ketjen black and polyvinylidene fluoride was added, and then ball milled at 350 rpm for 20 hours to obtain a coating slurry;

[0084] (2) The coating slurry obtained in step (1) is applied on one side of the carbon paper. The coating amount of the slurry on the carbon paper is 0.8 mg / cm 2 , and then dried in a vacuum drying oven at 120°C for 12 h to obtain a positive electrode sheet.

[0085] Application Examples 1 to 3 and Comparative Application Example 1

[0086] The photoelectric cathodes in Examples 1 to 3 and Comparative Example 1 were respectively assembled with 1M LiTFSI / TEGDME electrolyte, a glass fiber separator, and a 0.6 mm lithium sheet into 2025 button cells. The 2025 button cell cathode shell had a circular window with a diameter of 10 mm.

[0087] Performance testing: In an oxygen atmosphere glove box, the button cells prepared in Examples 1 to 3 and Comparative Example 1 were tested for charge and discharge using the Newwell battery testing system. The test conditions were: room temperature (25°C), xenon lamp illumination, current density (200mA / g), capacity limit (1000mAh / g) (calculated based on the mass of the carbon material in the positive electrode), and voltage range (2.2-4.5V vs. Li / Li). + , the test results are shown in Table 1 and Figure 5 .

[0088] In an oxygen atmosphere glove box, the button cell prepared in Example 1 was subjected to charge and discharge tests using the Newwell battery testing system. The test conditions were: at room temperature of 25°C, without light irradiation, with a current density of 200 mA / g, a limited capacity of 1000 mAh / g (both calculated based on the mass of the carbon material in the positive electrode), and a voltage range of 2.2 to 4.5 V vs. Li / Li. + , the test results are shown in Table 1 and Figure 5 .

[0089] Table 1 Electrical properties of button batteries prepared in Application Examples 1 to 3 and Comparative Application Example 1

[0090]

[0091] As can be seen from Table 1, the photoelectrocatalytic performance of the photoelectrode containing nickel-doped α-ferric oxide nanospheres has been significantly improved, effectively reducing the battery overpotential.

[0092] Figure 5 The first charge and discharge curves of the button batteries prepared in Application Example 1 and Comparative Application Example 1 are shown. Figure 5 It can be seen that under the irradiation of xenon lamp light source, the current density is 200mA / g, the limiting capacity is 1000mAh / g, and the voltage range is 2.2~4.5Vvs.Li / Li + Under the conditions of , the first cycle overpotential of the light-assisted lithium-air battery containing the photoelectric cathode prepared in the embodiment of the present invention is 0.73V.

[0093] It can be seen from the above examples that the light-assisted lithium-oxygen battery photoelectric cathode provided by the present invention has excellent catalytic effect, promotes the formation and decomposition process of lithium peroxide, and reduces the battery charging overpotential. The lithium-air battery assembled using the light-assisted lithium-air battery photoelectric cathode provided by the present invention has a first cycle overpotential of 0.73V under light conditions.

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A photoelectric cathode for a light-assisted lithium-air battery, comprising a conductive current collector and a porous coating applied on either side of the conductive current collector; the porous coating comprising nickel-doped α-ferric oxide nanospheres, conductive carbon black, and a binder; The coating amount of the porous coating is 0.8 to 2.0 mg / cm 2 ; The preparation method of the nickel-doped α-ferric oxide nanospheres comprises: Potassium ferrocyanide, diammonium hydrogen phosphate, a nickel source and water are mixed and subjected to hydrothermal reaction, and then centrifugally washed and dried to obtain nickel-doped α-ferric oxide nanospheres.

2. The photoelectric cathode of a light-assisted lithium-air battery according to claim 1, wherein The mass ratio of the nickel-doped α-ferric oxide nanospheres, the conductive carbon black and the binder is (1-3): (6-8):

1.

3. The photoelectric cathode of the light-assisted lithium-air battery according to claim 1, characterized in that The conductive carbon black includes one or two of Ketjen black, acetylene black, carbon nanotubes and graphene; and the binder includes polyvinylidene fluoride.

4. The photoelectric cathode of a light-assisted lithium-air battery according to claim 1, wherein The diameter of the nickel-doped α-ferric oxide nanospheres is 200-300 nm.

5. The photoelectric cathode of the light-assisted lithium-air battery according to claim 1, characterized in that The molar ratio of the potassium ferrocyanide, diammonium hydrogen phosphate and nickel source is (2.5-3):1:(0.25-0.9).

6. The photoelectric cathode of the light-assisted lithium-air battery according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 180-200° C., and the time of the hydrothermal reaction is 5-40 hours.

7. The method for preparing the photoelectric cathode of a light-assisted lithium-air battery according to any one of claims 1 to 6, comprising the following steps: (1) mixing nickel-doped α-ferric oxide nanospheres, conductive carbon black, a binder, and a slurry to obtain a coating slurry; (2) coating the coating slurry obtained in step (1) on either side of a conductive current collector, and drying the coating slurry to obtain a photoelectric positive electrode for a light-assisted lithium-air battery.

8. A light-assisted lithium-air battery, comprising the photoelectric cathode of any one of claims 1 to 6 or the photoelectric cathode prepared by the preparation method of claim 7, an electrolyte, a separator and a lithium sheet.

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