A low-temperature metal fuel cell

Abstract

The present invention discloses a novel low-temperature metal fuel cell, which belongs to the field of energy material technology and comprises the following steps: solid-phase mixing of an Fe salt, a Co salt, a Cu salt, an Al salt, and a carbon source; wherein the carbon source is dicyandiamide; calcining the mixed powder under a nitrogen atmosphere to obtain a precursor material; calcining at a temperature of 750-850°C for 1.5-2.5 hours; and immersing the obtained precursor material in an HCl solution, washing, and drying to obtain an electrocatalyst. The electrocatalytic material preparation process of the present invention is simple, the raw materials used are low-cost, and it is easy to implement. The assembled metal-air battery has excellent discharge performance and can withstand cold environments of -30°C.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and more specifically, to an electrocatalyst for a low-temperature metal-air battery, a preparation method thereof, and a low-temperature metal fuel cell. Background Art

[0002] Metal-air batteries have made great progress in the field of new energy in recent years due to their unique advantages such as low environmental pollution, high discharge capacity, and high energy density. Aluminum metal is abundant in the earth's crust. When used as an aluminum-air fuel cell, its actual specific capacity is 2.3 times that of lithium-ion batteries, reaching 500 Wh kg. -1 In addition, aluminum-air batteries can be mechanically recharged by replacing new metal electrodes and electrolytes, making them "refuelable" batteries. However, aluminum-air batteries are at -10 o The difficulty of self-starting in environments with low temperatures (C) and the slow kinetics of the cathode reaction limit the battery's practical energy density. Therefore, the most commonly used cathode catalysts are precious metals such as Pt and Au, which have high catalytic efficiency. However, the high cost and low utilization efficiency of precious metals limit their large-scale commercial production and application. Therefore, in order to enable the application of aluminum-air batteries in regional environments with complex temperatures, it is necessary to design a metal-air battery catalyst that is efficient and stable at low temperatures. Summary of the Invention

[0003] To address the aforementioned difficulties with aluminum-air batteries in discharging at low temperatures and overcome the shortcomings of the prior art, this invention provides a method for preparing an electrocatalyst for low-temperature metal-air batteries. The electrocatalytic material preparation process is simple, using inexpensive raw materials and is easy to implement. The resulting metal-air battery exhibits excellent discharge performance and is resistant to temperatures as low as -30°C.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A method for preparing an electrocatalyst for a low-temperature metal-air battery comprises the following steps:

[0006] (1) solid-phase mixing of Fe salt, Co salt, Cu salt, Al salt and a carbon source; wherein the carbon source is dicyandiamide, and the mass ratio of the sum of the mass of the Fe salt, Co salt, Cu salt and Al salt to the mass of the carbon source is 1:4.5-5.5; calcining under a nitrogen gas atmosphere to obtain a precursor material; the calcination temperature is 750-850 °C, and the time is 1.5-2.5 h;

[0007] (3) The obtained precursor material is immersed in an HCl solution, and the electrocatalyst HFeCoCuAl@CNTs is obtained after washing and drying.

[0008] In the present invention, HFeCoCuAl@CNTs is composed of high-entropy nanomaterials and nitrogen-doped carbon nanotubes, wherein the high-entropy alloy contains four metal elements: Fe, Co, Cu, and Al, and the nitrogen-doped carbon nanotubes are formed in situ; the prepared HFeCoCuAl@CNTs material has a dual-phase structure; due to its rich defect structure and a large number of active sites on the surface, it can be used in low-temperature aluminum-air batteries.

[0009] Furthermore, in step (1), the Fe salt, Co salt, Cu salt, and Al salt are specifically FeCl3, Co(NO3)2·6H2O, Cu(CH3COO)2, and Al(NO3)3, respectively. In the present invention, the acid radicals of these metal salts are easily removed, making it easier to obtain the desired product, and therefore the above metal salts are preferably used.

[0010] Furthermore, in step (1), the mass ratio of FeCl3, Co(NO3)2·6H2O, Cu(CH3COO)2 and Al(NO3)3 is (0.7~1.2):(0.7~1.2):(0.7~1.2), preferably 1:1:1:1.

[0011] Furthermore, in step (1), the mass ratio of the sum of the masses of the Fe salt, the Co salt, the Cu salt, and the Al salt to the mass ratio of the carbon source is 1:5.

[0012] Furthermore, in step (1), the solid phase mixing is ball milling, and the ball milling time is 150 to 200 minutes. The raw materials are ball milled in a planetary ball mill in a forward and reverse rotation mode, so as to be evenly mixed and obtain a more uniform product.

[0013] Specifically, during ball milling, the machine can be rotated forward for 5 minutes, reversed for 5 minutes, and rested for 1 minute until the milling is completed.

[0014] Furthermore, in step (2), the calcination temperature is preferably 800°C and the calcination time is 2 h. Under this temperature condition, carbon nanotubes CNTs can be grown in situ while ensuring the dispersion of CNTs.

[0015] Furthermore, in step (3), the concentration of the HCl solution is 0.5-5 mol L -1 The immersion time is 10-30 hours. Preferably, the HCl solution concentration is 1 mol / L, and the immersion time is 24 hours. This immersion time in a hydrochloric acid solution of this concentration yields the best electrocatalyst material. This is the optimal process condition for synthesizing the HFeCoCuAl@CNTs catalyst.

[0016] A second object of the present invention is to provide an electrocatalyst for low-temperature metal-air batteries prepared by any of the above preparation methods.

[0017] The present invention also aims to provide a low-temperature metal fuel cell, wherein the cathode of the low-temperature metal fuel cell comprises the electrocatalyst described above. That is, the electrocatalyst for low-temperature metal-air battery is applied to the metal fuel cell.

[0018] Furthermore, the obtained electrocatalyst material is dissolved in a naphthol aqueous solution under ultrasonic conditions, and then coated on a hydrophobic carbon cloth to obtain a modified carbon cloth electrode, which is used as the cathode of the aluminum-air battery; the electrolyte of the low-temperature metal fuel cell is a cesium hydroxide solution, preferably, the concentration of the cesium hydroxide solution is 5 mol L -1 .

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The HFeCoCuAl@CNTs material prepared by the present invention has a special two-phase structure. The defect structure caused by the two-phase structure greatly improves the electrochemical performance of aluminum-air batteries. -2 At a current density of 1.5 GHz, the aluminum-air battery using this catalyst can discharge stably for 250 hours in a low-temperature environment of -30 ℃.

[0021] (2) Alloy nanoparticles provide a large number of reactive sites, and the limiting current density of ORR can reach 6.41 mAcm -2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a TEM image of the catalyst prepared in Example 1;

[0023] Figure 2 HAADF-STEM image of the catalyst prepared in Example 1;

[0024] Figure 3 Linear voltammetric scan of the oxygen reduction performance of the catalyst prepared in Example 1;

[0025] Figure 4 Schematic diagram of the device of the aluminum-air battery obtained by assembling the catalyst prepared in Example 1;

[0026] Figure 5 The linear voltammetric scan diagram of the aluminum-air battery obtained by assembling the catalysts prepared in Example 1 and Comparative Example 2 at room temperature;

[0027] Figure 6 Example 1 is prepared as a catalyst assembly and the constant current discharge performance of the aluminum-air battery at room temperature;

[0028] Figure 7 Constant current discharge performance of the aluminum-air battery obtained in Example 1 at low temperature;

[0029] Figure 8 X-ray diffraction (XRD) pattern of the catalyst prepared in Comparative Example 1;

[0030] Figure 9 Comparative Example 1 is prepared as the constant current discharge performance of the aluminum-air battery obtained by assembling the catalyst at room temperature;

[0031] Figure 10 Comparative Example 1 is prepared as the constant current discharge performance of the aluminum-air battery obtained by assembling the catalyst at low temperature;

[0032] Figure 11 TEM image of the catalyst prepared in Comparative Example 3;

[0033] Figure 12 Comparative Example 3 is prepared as the constant current discharge performance of the aluminum-air battery obtained by assembling the catalyst at low temperature;

[0034] Figure 13 TEM image of the catalyst prepared in Comparative Example 4;

[0035] Figure 14 Comparative Example 5 is a linear voltammetric scan diagram of the aluminum-air battery obtained by catalyst assembly at room temperature. DETAILED DESCRIPTION

[0036] The following description sets forth numerous specific details to facilitate a thorough understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific implementations disclosed below.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] In the following examples, all the raw materials used are common commercial products that can be purchased directly.

[0039] Example 1

[0040] The preparation method of the electrocatalyst HFeCoCuAl@CNTs material for aluminum-air batteries described in this embodiment includes the following steps:

[0041] The preparation method of the electrocatalyst HFeCoCuAl@CNTs material for aluminum-air batteries comprises the following steps:

[0042] 1) Weigh 4 g of dicyandiamide into a mortar and add 0.2 g of anhydrous ferric chloride, 0.2 g of cobalt nitrate hexahydrate, 0.2 g of aluminum nitrate, and 0.2 g of anhydrous copper acetate.

[0043] 2) The above metal salts and dicyandiamide were initially ground and mixed uniformly, and then transferred to a planetary ball mill for ball milling, alternating forward rotation for 5 minutes and reverse rotation for 5 minutes, with an interval of 1 minute. The total ball milling time was 179 minutes to obtain a uniformly mixed powder.

[0044] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate is from room temperature to 800 o C and kept warm for 2 h to obtain nitrogen-doped graphitic carbon nanotubes supported on quaternary high entropy alloy (FeCoCuAl@CNTs).

[0045] 4) Weigh 20 mg of FeCoCuAl@CNTs and soak them in 20 mL of 1 M HCl solution for 24 hours. Wash them three times with deionized water and three times with ethanol, then vacuum dry them for 6 hours. The resulting black powder is the biphasic HFeCoCuAl@CNTs catalyst.

[0046] The catalyst prepared in this example was subjected to the following tests:

[0047] TEM test: TEM test results are as follows Figure 1 Figure 2 shows a transmission electron microscopy image of HFeCoCuAl@CNTs, which shows that the alloy nanoparticles are encapsulated by carbon nanotubes. The carbon nanotube structure facilitates ion and electron transport during electrocatalysis.

[0048] HR-TEM test: Figure 2 This is the HR-TEM test result, that is, the high-resolution transmission electron microscopy image of HFeCoCuAl@CNTs; in the high-resolution transmission electron microscopy image, lattice fringes with interplanar spacings of 2.19 Å and 2.01 Å can be observed, corresponding to the fcc structure and bcc structure, respectively.

[0049] Catalytic performance test:

[0050] Both oxygen reduction and oxygen evolution performance tests were performed using a three-electrode system. The working electrode was a glassy carbon electrode loaded with the catalyst material prepared in Example 1, the counter electrode was a mercury / mercuric oxide electrode, and the auxiliary electrode was a platinum wire. The electrolyte was a 0.1 M potassium hydroxide solution.

[0051] Specifically, a mixed slurry was prepared. The mixed slurry consisted of 5 mg of catalyst material, 480 μL of deionized water, 480 μL of ethanol, and 40 μL of Nafion solution. In this example, 5 μL of the mixed slurry was dripped onto a glassy carbon electrode and allowed to dry naturally before use to obtain a working electrode.

[0052] The catalyst obtained in this embodiment has good oxygen reduction and oxygen evolution catalytic performance. Figure 3 The linear voltammetric scan results of oxygen reduction of the catalyst material of this example were tested at 1600 rpm. The onset potential was 1.1 V, the half-wave potential was 0.823 V, and the limiting current density was 6.41 mA cm -2 .

[0053] Aluminum-air battery performance test:

[0054] The aluminum air test device uses a polished aluminum plate as the anode and a carbon cloth modified with the catalyst (the 2 mg catalyst obtained in Example 1 is loaded on a 1*1 cm 2 The low-temperature metal fuel cell obtained in this example was then tested for its electrical properties.

[0055] Figure 4 This is a state diagram of the catalyst material of this embodiment being used as a cathode catalyst in a low-temperature aluminum-air battery.

[0056] Figure 5 The LSV curve of the aluminum-air battery obtained in Example 1 at room temperature is given, and the power density is 43 mW cm -2 . Figure 6 The constant current discharge performance graph is shown. At 10 mA cm -2 At a current density of , the aluminum-air battery can be discharged at room temperature for about 5 hours, after which the voltage will gradually decay. Figure 7 Its low temperature discharge performance is 2 mA cm -2 At a current density of 1.5 GHz, the aluminum-air battery using this electrocatalyst can discharge stably for more than 250 hours in a low-temperature environment of -30 ℃.

[0057] Example 2

[0058] The preparation method of the electrocatalyst HFeCoCuAl@CNTs material for aluminum-air batteries comprises the following steps:

[0059] 1) Weigh 4.2 g of dicyandiamide into a mortar and pestle, then add 0.2 g of anhydrous ferric chloride, 0.2 g of cobalt nitrate hexahydrate, 0.2 g of aluminum nitrate, and 0.2 g of anhydrous copper acetate.

[0060] 2) After the above metal salts and dicyandiamide are preliminarily ground and mixed evenly, they are transferred to a planetary ball mill for ball milling, alternating forward rotation for 5 minutes and reverse rotation for 5 minutes with an interval of 1 minute. The total ball milling time is 200 minutes to obtain a uniformly mixed powder.

[0061] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate was from room temperature to 830 o C and kept warm for 2 h to obtain nitrogen-doped graphitic carbon nanotubes supported on quaternary high entropy alloy (FeCoCuAl@CNTs).

[0062] 4) Weigh 20 mg of FeCoCuAl@CNTs and soak them in 20 mL of 1.5 M HCl solution for 20 hours. Wash them three times with deionized water and three times with ethanol, then vacuum dry them for 6 hours. The resulting black powder is the biphasic HFeCoCuAl@CNTs catalyst.

[0063] The catalyst obtained in this example was tested and showed to also have a structure of alloy nanoparticles coated with carbon nanotubes.

[0064] An aluminum-air battery was assembled according to the method in Example 1. The test conditions were the same as in Example 1. The obtained aluminum-air battery was tested to be able to stably discharge for more than 200 hours in a low temperature environment of -30°C.

[0065] Example 3

[0066] The preparation method of the electrocatalyst HFeCoCuAl@CNTs material for aluminum-air batteries comprises the following steps:

[0067] 1) Weigh 3.8 g of dicyandiamide into a mortar and pestle. Add 0.21 g of anhydrous ferric chloride, 0.21 g of cobalt nitrate hexahydrate, 0.19 g of aluminum nitrate, and 0.19 g of anhydrous copper acetate.

[0068] 2) After the above metal salts and dicyandiamide are preliminarily ground and mixed evenly, they are transferred to a planetary ball mill and ball milled, alternating forward rotation for 5 minutes and reverse rotation for 5 minutes with an interval of 1 minute. The total ball milling time is 190 minutes to obtain a uniformly mixed powder.

[0069] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate was from room temperature to 780 o C and kept warm for 2 h to obtain nitrogen-doped graphitic carbon nanotubes supported on quaternary high entropy alloy (FeCoCuAl@CNTs).

[0070] 4) Weigh 20 mg of FeCoCuAl@CNTs and soak them in 20 mL of 2 M HCl solution for 20 hours. Wash them three times with deionized water and three times with ethanol, then vacuum dry them for 6 hours. The resulting black powder is the biphasic HFeCoCuAl@CNTs catalyst.

[0071] The catalyst obtained in this example was tested and showed to also have a structure of alloy nanoparticles coated with carbon nanotubes.

[0072] An aluminum-air battery was assembled according to the method in Example 1. The test conditions were consistent with those in Example 1. The obtained aluminum-air battery was tested to be able to discharge stably for more than 200 hours in a low temperature environment of -30°C.

[0073] Comparative Example 1

[0074] A method for preparing an electrocatalyst HFeCoCuAl@CNTs material for an aluminum-air battery comprises the following steps:

[0075] 1) Weigh 4 g of dicyandiamide into a mortar and pestle, then add 0.2 g of anhydrous ferric chloride, 0.2 g of cobalt nitrate hexahydrate, 0.2 g of aluminum nitrate, and 0.2 g of anhydrous copper acetate.

[0076] 2) After preliminary grinding and mixing of the metal salts and dicyandiamide, transfer them to a planetary ball mill and mill them alternately in forward rotation for 5 minutes and reverse rotation for 5 minutes with an interval of 1 minute. The total milling time is 179 minutes to obtain a uniformly mixed powder.

[0077] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate is from room temperature to 800 o C and kept warm for 2 h to obtain nitrogen-doped graphitic carbon nanotubes supported on quaternary high entropy alloy (FeCoCuAl@CNTs).

[0078] Comparative Example 1 removes the acid etching. Compared with Example 1, Comparative Example 1 changes the phase structure of the alloy nanoparticles. Figure 8 The XRD results show that the alloy is mainly composed of bcc phase. Figure 9 The discharge performance diagram of the low-temperature aluminum-air battery of Comparative Example 1 is given. The test conditions are consistent with those in Example 1. It discharges for about 3 hours at room temperature. In comparison, the electrochemical performance has a greater attenuation. Figure 10 The aluminum-air battery obtained in Comparative Example 1 can be stably discharged for about 40 hours in a low-temperature environment of -30°C, and the discharge time is greatly attenuated.

[0079] Comparative Example 2

[0080] 1) Weigh 4 g of dicyandiamide into a mortar and pestle, then add 0.2 g of anhydrous ferric chloride, 0.2 g of cobalt nitrate hexahydrate, 0.2 g of aluminum nitrate, and 0.2 g of anhydrous copper acetate.

[0081] 2) The above metal salts and dicyandiamide were initially ground and mixed uniformly, and then transferred to a planetary ball mill for ball milling, alternating forward rotation for 5 minutes and reverse rotation for 5 minutes, with an interval of 1 minute. The total ball milling time was 179 minutes to obtain a uniformly mixed powder.

[0082] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate is from room temperature to 800 o C and kept warm for 2 h to obtain the precursor material.

[0083] 4) Weigh 20 mg of the resulting precursor and soak it in 20 mL of 1 M HCl solution for 12 hours. Wash it three times with deionized water and three times with ethanol, then vacuum dry it for 6 hours to obtain the catalyst.

[0084] Comparative Example 2 is compared with Example 1, in which the immersion time in step 4) is adjusted. The test conditions are the same as those in Example 1. The power density of the aluminum-air battery obtained by the test is 38 mW cm -2 .

[0085] Comparative Example 3

[0086] A method for preparing an electrocatalyst HFeCoCuAl@CNTs material for an aluminum-air battery comprises the following steps:

[0087] 1) Weigh 4 g of dicyandiamide into a mortar and add 0.2 g of anhydrous ferric chloride, 0.2 g of cobalt nitrate hexahydrate, 0.2 g of aluminum nitrate, and 0.2 g of anhydrous copper acetate.

[0088] 2) After preliminary grinding and mixing of the metal salts and dicyandiamide, transfer them to a planetary ball mill and mill them alternately in forward rotation for 5 minutes and reverse rotation for 5 minutes with an interval of 1 minute. The total milling time is 179 minutes to obtain a uniformly mixed powder.

[0089] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate is from room temperature to 700 o C and kept warm for 2 h to obtain a quaternary high entropy alloy / carbon composite material (FeCoCuAl / C).

[0090] 4) Weigh 20 mg of FeCoCuAl / C and soak it in 20 mL of 1 M HCl solution for 24 hours. Wash it three times with deionized water and three times with ethanol, then vacuum dry it for 6 hours to obtain the electrocatalyst.

[0091] Comparative Example 3 at 700 o Compared with Example 1, Comparative Example 3 changed the carbon treatment temperature. Figure 11 The TEM image of the catalyst prepared in Comparative Example 3 is given, and it can be seen that no carbon tubes are formed in the alloy material. Figure 12 The discharge performance diagram of the low-temperature aluminum-air battery of Comparative Example 3 is given. The discharge is about 2.4 hours at low temperature, and the electrochemical performance is greatly attenuated in comparison.

[0092] Comparative Example 4

[0093] 1) Weigh 4 g of urea into a mortar and pestle, then add 0.2 g of anhydrous ferric chloride, 0.2 g of cobalt nitrate hexahydrate, 0.2 g of aluminum nitrate, and 0.2 g of anhydrous copper acetate.

[0094] 2) The above metal salts and dicyandiamide were initially ground and mixed uniformly, and then transferred to a planetary ball mill for ball milling, alternating forward rotation for 5 minutes and reverse rotation for 5 minutes, with an interval of 1 minute. The total ball milling time was 179 minutes to obtain a uniformly mixed powder.

[0095] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate is from room temperature to 800 o C and kept warm for 2 h to obtain the precursor material.

[0096] 4) Weigh 20 mg of the resulting precursor and soak it in 20 mL of 1 M HCl solution for 24 hours. Wash it three times with deionized water and three times with ethanol, then vacuum dry it for 6 hours to obtain the catalyst.

[0097] Comparative Example 4 compared to Example 1, the type of carbon source was changed. Figure 13 This is a TEM image of the electrocatalyst obtained in Comparative Example 4, showing that the metal particles are severely agglomerated.

[0098] Comparative Example 5

[0099] 1) Weigh 4 g of dicyandiamide into a mortar and add 0.2 g of anhydrous ferric chloride, 0.2 g of cobalt nitrate hexahydrate, 0.2 g of aluminum nitrate, and 0.2 g of manganese acetate.

[0100] 2) The above metal salts and dicyandiamide were initially ground and mixed uniformly, and then transferred to a planetary ball mill for ball milling, alternating forward rotation for 5 minutes and reverse rotation for 5 minutes, with an interval of 1 minute. The total ball milling time was 179 minutes to obtain a uniformly mixed powder.

[0101] 3) Place the mixed powder in a tube furnace and heat it at 5 o C min -1 The heating rate is from room temperature to 800 o C and kept warm for 2 h to obtain the precursor material.

[0102] 4) Weigh 20 mg of the resulting precursor and soak it in 20 mL of 1 M HCl solution for 24 hours. Wash it three times with deionized water and three times with ethanol, then vacuum dry it for 6 hours to obtain the catalyst.

[0103] Comparative Example 5 Compared with Example 1, the anhydrous copper acetate in the metal salt was replaced with manganese acetate. Figure 14 The LSV curve of the obtained aluminum-air battery at room temperature is 39 mW cm -2 .

[0104] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing an electrocatalyst for a low-temperature metal-air battery, characterized in that: The following steps are involved: (1) solid-phase mixing of Fe salt, Co salt, Cu salt, Al salt and a carbon source; wherein the carbon source is dicyandiamide, and the mass ratio of the sum of the mass of the Fe salt, Co salt, Cu salt and Al salt to the mass of the carbon source is 1:4.5-5.5; (2) calcining the mixed powder in a nitrogen atmosphere to obtain a precursor material; the calcination temperature is 750~850℃ and the time is 1.5~2.5 h; (3) The obtained precursor material is immersed in an HCl solution for 20 to 30 h. After washing and drying, the electrocatalyst HFeCoCuAl@CNTs is obtained. The electrocatalyst has an fcc structure and a bcc structure.

2. The preparation method according to claim 1, characterized in that In step (1), the Fe salt, Co salt, Cu salt and Al salt are specifically FeCl3, Co(NO3)2·6H2O, Cu(CH3COO)2 and Al(NO3)3, respectively.

3. The preparation method according to claim 2, characterized in that The mass ratio of FeCl3, Co(NO3)2·6H2O, Cu(CH3COO)2 and Al(NO3)3 is (0.7~1.2):(0.7~1.2):(0.7~1.2).

4. The preparation method according to claim 1, characterized in that In step (1), the mass ratio of the sum of the masses of the Fe salt, the Co salt, the Cu salt, and the Al salt to the mass ratio of the carbon source is 1:

5.

5. The preparation method according to claim 1, characterized in that In step (1), the solid phase mixing is ball milling mixing, and the ball milling time is 150-200 min.

6. The preparation method according to claim 1, characterized in that In step (2), the calcination temperature is 800°C and the time is 2 h.

7. The preparation method according to claim 1, characterized in that In step (3), the concentration of the HCl solution is 0.5~5 mol L -1 .

8. An electrocatalyst for low-temperature metal-air batteries prepared by the preparation method according to any one of claims 1 to 7.

9. A low-temperature metal fuel cell, characterized in that: The cathode of the low-temperature metal fuel cell comprises the electrocatalyst according to claim 8.

10. The low-temperature metal fuel cell according to claim 9, characterized in that: The obtained electrocatalyst material is dissolved in a naphthol aqueous solution under ultrasonic conditions, and then coated on a hydrophobic carbon cloth to obtain a modified carbon cloth electrode, which is used as the cathode of an aluminum-air battery; the electrolyte of the low-temperature metal fuel cell is a cesium hydroxide solution.

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