Zinc-air composite battery cathode material catalyst and its preparation method and application

Abstract

The invention discloses a method for preparing a zinc-air composite battery cathode material catalyst, which comprises the following steps: S1: weighing niobium oxalate, strontium nitrate, cobalt nitrate, iron nitrate and manganese nitrate, and weighing citric acid and EDTA at the same time, adding the above raw materials into a reaction vessel, and synthesizing a SNCF-Mn gel precursor by a sol-gel method; S2: drying and sintering it to obtain a B-position Mn element doped SNCF, namely SNCF-Mn; S3: placing it in a tubular furnace, heating it to 400°C under an argon atmosphere to perform a sulfurization operation, and obtaining a zinc-air composite battery cathode material catalyst final product SNCF-Mn-S4. The catalyst prepared by the invention solves the problem of insufficient performance of the oxygen reduction reaction ORR of the SNCF catalyst, and greatly improves the electrochemical properties of the zinc-air composite battery, such as the potential difference ΔE, the cycle efficiency and the cycle stability.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a zinc-air composite battery cathode material catalyst and a preparation method and application thereof. Background Art

[0002] Metal-air batteries are considered to be a new type of battery material with great development and application prospects in the future. The air cathode material is the core component of metal-air batteries and has a direct impact on the battery performance of metal-air batteries. The catalytic layer contained in the metal-air battery provides a catalyst for the electrochemical reaction in the battery. Perovskite-type oxygen catalysts have received increasing research and attention in metal-air batteries due to their unique physical and chemical properties. However, the perovskite catalysts used in traditional metal-air batteries have a small specific surface area due to high-temperature sintering and agglomeration, as well as insufficient oxygen reduction reaction (ORR) performance.

[0003] Sb 0.1 Co 0.7 Fe 0.2 O 3-δ (SNCF) oxygen catalyst has excellent OER activity due to its high oxygen vacancy concentration, fast oxygen reaction rate and optimal covalent electron configuration. However, the disadvantages of SNCF are also obvious, such as high temperature sintering will cause agglomeration, resulting in a lower specific surface area and difficulty in exposing active sites, segregation of A-site ions and easy reaction with OH in alkaline solution. - The formation of corresponding insoluble hydroxides is an important factor affecting its catalytic activity and stability. However, its most serious problem is its low ORR activity. The slow ORR kinetics is the biggest obstacle to its becoming a bifunctional oxygen catalyst. There are few reports on the application of oxygen composite catalysts based on SNCF in the field of zinc-air composite batteries. Summary of the invention

[0004] In view of the above shortcomings of the prior art, the present invention provides a zinc-air composite battery cathode material catalyst to solve the problems of small specific surface area, difficulty in exposing active sites, segregation of A-site ions and easy reaction with OH in alkaline solution when SNCF oxygen catalyst is used in metal-air batteries. - The formation of corresponding insoluble hydroxides and other problems can solve the problem of insufficient oxygen reduction reaction (ORR) performance of SNCF catalyst.

[0005] Based on a lot of preliminary research, the inventors of this application have found that the existing technology has the following problems: 1) Although surface structural construction of SNCF can increase its specific surface area, its improvement in OER and ORR performance is not ideal. 2) Although Mn doping of other types of material systems has improved performance, the performance improvement is not significant compared to the original sample without Mn doping, and the stability of zinc-air batteries made without perovskite as a matrix support is also unsatisfactory. 3) Perovskite is an oxide with a very stable structure. Direct sulfurization cannot effectively dope or compound the S element, which leads to the catalytic performance of the perovskite catalyst cannot be greatly improved. The inventors of this application creatively proposed for the first time to first add strontium niobium cobalt iron (SrNb 0.1 Co 0.7 Fe 0.2 O 3-δ The original basic structure of zinc-air composite battery (SNCF) is doped with Mn element in the B position, and then a high-performance zinc-air composite battery cathode material catalyst is prepared by setting strict conditions and pressurizing sulfurization.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for preparing a zinc-air composite battery cathode material catalyst, the preparation method comprising the following steps:

[0008] Step S1: Weighing niobium oxalate, strontium nitrate, cobalt nitrate, iron nitrate and manganese nitrate according to a certain stoichiometric ratio, and weighing a certain amount of citric acid and EDTA, adding the above raw materials into a reaction container, and synthesizing a SNCF-Mn gel precursor by a sol-gel method;

[0009] Step S2: drying and sintering the SNCF-Mn gel precursor obtained in step S1 to obtain SNCF doped with Mn at the B site, referred to as SNCF-Mn;

[0010] Step S3: placing a certain amount of the SNCF-Mn obtained in step S2 in a tubular furnace, heating it to 400° C. under an argon atmosphere for sulfurization operation, and obtaining the final product SNCF-Mn-S4 of the zinc-air composite battery cathode material catalyst.

[0011] Preferably, the cathode material catalyst SNCF-Mn-S4 obtained in step S3 has an electrochemical performance potential difference ΔE that is improved by more than 100 mV compared to the SNCF-Mn obtained in step S2.

[0012] Preferably, in step S1, the stoichiometric ratio of the molar number of all metal ions in the niobium oxalate, strontium nitrate, cobalt nitrate, iron nitrate and manganese nitrate to the molar number of EDTA and citric acid is: metal ion: EDTA: citric acid is 2:1:4.

[0013] Preferably, in step S1, the raw materials are added to the reaction container in the order of niobium oxalate, citric acid, strontium nitrate, cobalt nitrate, iron nitrate, manganese nitrate and EDTA.

[0014] Preferably, in step S2, the drying operation conditions are a drying temperature of 180±5°C and a drying time of 2±0.5h, and the SNCF gel precursor is obtained in an expanded foam state; the sintering operation conditions are a calcination temperature of 1000±20°C and a calcination time of 12±0.5h.

[0015] Preferably, in step S2, the B-site Mn element-doped SNCF has a general formula of S(NCF)aMnb; wherein the molar ratio a:b of the B-site NCF element to the Mn element is 0.95:0.05 to 0.5:0.5.

[0016] Preferably, in step S2, the B-site Mn element-doped SNCF has a general formula of S(NCF)aMnb; wherein the molar ratio a:b of the B-site NCF element to the Mn element is 0.65:0.35.

[0017] Preferably, in step S3, when the temperature of the vulcanization operation rises to 400±10°C, the valve at one end of the tube furnace is closed to give the tube furnace a certain pressure, and when the pressure of the tube furnace rises to 0.5±0.05 bar, the valves at both ends of the tube furnace are kept closed.

[0018] One aspect of the present invention is to provide a cathode material catalyst for a zinc-air composite battery, wherein the cathode material catalyst is obtained by the above-mentioned preparation method.

[0019] Another aspect of the present invention is to use the cathode material catalyst of the zinc-air composite battery as described above, and to prepare a slurry with the cathode material catalyst and carbon powder in a ratio of 5 mg:5 mg, and then uniformly load the slurry on a 1×1 cm 2 The carbon cloth is used as the cathode of the zinc-air composite battery to make a zinc-air composite battery; wherein the power density of the zinc-air composite battery reaches 135mW / cm 2 , the cycle efficiency reaches 75%, and the charge and discharge cycle can operate stably for up to 500 hours.

[0020] Beneficial effects of the present invention:

[0021] The cathode material catalyst of the zinc-air composite battery prepared by the present invention solves the problems that when the SNCF oxygen catalyst is applied to metal-air batteries, its specific surface area is small, the active sites are difficult to expose, the A-site ion is segregated, and it is easy to react with OH in an alkaline solution. -The formation of corresponding insoluble hydroxides and other problems make it have excellent performance in ORR / OER performance, and its potential difference ΔE has reached a breakthrough of 0.80V (ΔE is defined as 10mA*cm -2 The OER potential (Ej = 10) and the ORR half-wave potential (E 1 / 2 ). It is usually used as an indicator to determine the bifunctional catalytic performance of a catalyst, and the smaller the value, the better the catalytic performance of the catalyst).

[0022] The zinc-air composite battery made of the catalyst material prepared by the present invention as the cathode exhibits a charge-discharge cycle efficiency of up to 75% and a charge-discharge cycle stability of over 500 hours.

[0023] The zinc-air composite battery cathode material catalyst prepared by the present invention has good ORR / OER activity and stability, can be used for oxygen evolution reaction and as an electrode material for electrolysis of seawater to produce hydrogen, electrolysis of water to produce hydrogen, fuel cells, supercapacitors, metal-air batteries, etc., and has broad development prospects in zinc-air composite battery technology.

[0024] The preparation method of the present invention is relatively simple to operate, has a short preparation cycle, does not use precious metal materials, has low cost, has controllable synthesis conditions, and has the potential for large-scale preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the synthesis of SNCF-Mn-S4 in Example 1;

[0026] Figure 2 a. Figure 2 b. Figure 2 c and Figure 2 d are scanning electron microscope (SEM) images of control example 1 (SNCF), control example 2 (SNCF-Mn), control example 3 (SNCF-S4) and example 1 (SNCF-Mn-S4), respectively;

[0027] Figure 3 a is the X-ray diffraction (XRD) diagram of control example 1 (SNCF) and control example 2 (SNCF-Mn), Figure 3 b is the XRD pattern of control example 3 (SNCF-S4) and control example 1 (SNCF); Figure 3 c is the XRD pattern of Example 1 (SNCF-Mn-S4);

[0028] Figure 4 ORR / OER performance diagram of Example 1, Comparative Examples 1, 2, and 3 in 0.1 M KOH solution;

[0029] Figure 5This is a charge and discharge cycle diagram of the zinc-air composite battery made from the catalyst material of Example 1. DETAILED DESCRIPTION

[0030] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0031] Example 1

[0032] The preparation method of the zinc-air composite battery cathode material catalyst of the present embodiment comprises the following steps:

[0033] Step S1: weigh 0.00065 mol of niobium oxalate (C 10 H5B 20 ), 0.01 mol strontium nitrate (Sr(NO3)2), 0.00455 mol cobalt nitrate (Co(NO3)2*6H2O), 0.0013 mol ferric nitrate (Fe(NO3)3*9H2O) and 0.0035 mol manganese nitrate (added as 50wt% Mn(NO3)2 solution), and a certain amount of 0.04 mol citric acid and 0.01 mol EDTA are weighed, and the above raw materials are added into a reaction container, and a SNCF-Mn gel precursor is synthesized by a sol-gel method, specifically, the above raw materials are continuously stirred under heating in a water bath at a temperature of 80°C until the liquid is in a gel state; the stoichiometric ratio of the molar number of all metal ions in the niobium oxalate, strontium nitrate, cobalt nitrate, ferric nitrate and manganese nitrate to the molar number of EDTA and citric acid is: metal ion: EDTA: citric acid is 2:1:4. The raw materials are added to the reaction container in the order of niobium oxalate, citric acid, strontium nitrate, cobalt nitrate, iron nitrate, manganese nitrate and EDTA; when adding the above raw materials, ensure that the previous substance is completely dissolved and the final solution is clear before adding the second substance.

[0034] Step S2: drying and sintering the obtained SNCF-Mn gel precursor to obtain SNCF doped with Mn at the B site, referred to as S(NCF) 0.65 Mn 0.35 (SNCF-Mn); the drying operation conditions are a drying temperature of 180°C and a drying time of 2 hours, and the obtained SNCF gel precursor is in an expanded foam state; the sintering operation conditions are a calcination temperature of 1000°C and a calcination time of 12 hours. 0.1 Co 0.7 Fe 0.2 O 3-δThe Mn element was doped on the original basic structure of SNCF (abbreviated as SNCF). The incorporation of Mn element regulated the number of oxygen vacancies in SNCF. At the same time, Mn element has the effect of refining the grains. From the SEM image, it can be seen that the sample after Mn doping is smaller, which solves the problem of small specific surface area caused by agglomeration of traditional perovskite due to high-temperature sintering.

[0035] Step S3: a certain amount of the SNCF-Mn obtained in step S2 is placed in a tubular furnace, and the temperature is raised to 400°C under argon atmosphere to perform a sulfurization operation to obtain the final product SNCF-Mn-S4 of the zinc-air composite battery cathode material catalyst. In the experiment of this embodiment, 0.2g of SNCF-Mn sample and 1g of sulfur powder are placed in two different ceramic boats, one in front and one in the back (sulfur powder in front and sample in the back, that is, sulfur powder is close to the outlet of the tubular furnace), the air intake rate of the tubular furnace is adjusted to 30ml / min, the heating rate is 3°C / min, the maximum temperature is 400°C, and then it is naturally cooled after being kept warm for 2 hours; during the experiment, the outlet of the tubular furnace is closed when the temperature of the tubular furnace is raised to 400°C, the air inlet is kept continuously to inlet, and then the air inlet is closed when the pressure in the furnace is raised to 0.5bar, so that the valves at both ends of the tubular furnace are kept closed. Keep the temperature at 400℃ for 2 hours under high pressure to allow the reactants to fully react, wait for the tube furnace to cool down to room temperature, and restore the pressure in the tube furnace to normal pressure before opening it. The present invention can replace the oxygen atoms in the sample lattice with S atoms in an oxygen-free atmosphere to increase oxygen vacancies. At the same time, the Mn and Co elements in the sample can combine with the S element to form sulfides to enhance the ORR catalytic activity of the sample. The best sample obtained in this experimental exploration is the sample SNCF-Mn-S4 obtained by sulfurization at 400℃ in an argon atmosphere.

[0036] Those skilled in the art know that the partial catalytic performance or stability of the catalyst can be improved by sulfurization operation. However, different sulfurization raw materials or sulfurization conditions have a great influence on the performance of the catalyst. The present application creatively proposes a method of pressurized sulfurization, which changes the internal lattice stress of the reactants by giving them a certain degree of pressure during the sulfurization process and then makes it easier for S atoms to combine with the reactants to achieve the best sulfurization effect. In the prior art, the sample potential difference performance ΔE before and after catalyst sulfurization is only improved by 63mV, and the sulfurization operation has a limited level of improvement on the catalyst performance. The sample SNCF-Mn-S4 prepared by pressurized sulfurization in this embodiment has ΔE=0.80V, and the sample performance is far better than the sulfurization level mentioned in other works (usually greater than 0.9V).

[0037] Example 2

[0038] The preparation method of the catalyst SNCF-Mn-S4 in this embodiment is basically the same as that in Example 1, except that: in step S1, the raw material ratio of SNCF is weighed according to the following stoichiometric ratio: 0.0005 mol niobium oxalate, 0.01 mol strontium nitrate, 0.0035 mol cobalt nitrate, 0.001 mol iron nitrate and 0.005 mol manganese nitrate, and a certain amount of 0.04 mol citric acid and 0.01 mol EDTA are weighed; at the same time, after the B-position Mn element is doped in step S2, the SNCF-Mn is S(NCF) 0.5 Mn 0.5 .

[0039] Example 3

[0040] The preparation method of the catalyst SNCF-Mn-S4 in this embodiment is basically the same as that in Example 1, except that: in step S1, the raw material ratio of SNCF is weighed according to the following stoichiometric ratio: 0.00095 mol niobium oxalate, 0.01 mol strontium nitrate, 0.00665 mol cobalt nitrate, 0.0019 mol iron nitrate and 0.0005 mol manganese nitrate, and a certain amount of 0.04 mol citric acid and 0.01 mol EDTA are weighed; at the same time, after the B-position Mn element is doped in step S2, the SNCF-Mn is S(NCF) 0.95 Mn 0.05 .

[0041] Example 4

[0042] The preparation method of the catalyst SNCF-Mn-S4 in this embodiment is basically the same as that in Example 1, except that: in step S1, the raw material ratio of SNCF is weighed according to the following stoichiometric ratio: 0.0008 mol niobium oxalate, 0.01 mol strontium nitrate, 0.0056 mol cobalt nitrate, 0.0016 mol iron nitrate and 0.002 mol manganese nitrate, and a certain amount of 0.04 mol citric acid and 0.01 mol EDTA are weighed; at the same time, after the B-position Mn element is doped in step S2, the SNCF-Mn is S(NCF) 0.8 Mn 0.2 .

[0043] Comparative Example 1

[0044] The preparation method of the catalyst SNCF of this comparative example is basically the same as that of Example 1, except that: the raw material manganese nitrate in step S1 and step S2 is not added during the catalyst preparation process, that is, the SNCF is not doped with Mn element at the B position; at the same time, the SNCF obtained in the above steps is not subjected to sulfurization treatment.

[0045] Comparative Example 2

[0046] The preparation method of the catalyst SNCF-Mn in this comparative example is basically the same as that in Example 1, except that the sulfurization treatment in step S3 is not performed during the catalyst preparation process.

[0047] Comparative Example 3

[0048] The preparation method of the catalyst SNCF-S4 of this comparative example is basically the same as that of Example 1, except that: the raw material manganese nitrate in step S1 and step S2 is not added during the catalyst preparation process, that is, the SNCF is not doped with Mn element at the B position, but the SNCF is directly sulfided.

[0049] The catalysts prepared in Example 1 and Comparative Examples 1 to 3 were characterized structurally, and the results are as follows:

[0050] in, Figure 1 Schematic diagram of SNCF synthesis of comparative example 1; Figure 2 a is a scanning electron microscope (SEM) image of control example 1, from which it can be clearly seen that the physical phase of SNCF is a block structure with a relatively smooth surface; Figure 2 b is a scanning electron microscope (SEM) image of SNCF-Mn of control example 2. It can be clearly seen from the image that the surface of the SNCF-Mn sample is rougher and the particles are finer. This structure increases the specific surface area of ​​the catalyst material and provides more active sites, thereby improving its overall catalytic activity. Figure 2 c and Figure 2 d are SEM images of SNCF-S4 and SNCF-Mn-S4, respectively.

[0051] Figure 3 a is the X-ray diffraction (XRD) diagram of SNCF and SNCF-Mn, Figure 3 b and Figure 3 c are the XRD patterns of SNCF-S4 and SNCF-Mn-S4 at scanning angles of 20-90°. Figure 3 It can be clearly seen in c that the characteristic peaks of MnS and CoS2 exist in Example 1. Transition metal sulfides have very outstanding ORR performance, and their appearance makes up for the insufficient ORR performance of perovskite-type catalysts. This explains why the ORR performance of sample SNCF-Mn-S4 is greatly improved.

[0052] The catalysts prepared in Example 1 and Comparative Examples 1 to 3 were tested for performance, and the results are as follows:

[0053] The samples SNCF-Mn-S4, SNCF, SNCF-Mn, and SNCF-S4 of Example 1 and Comparative Examples 1, 2, and 3 were used in a three-electrode system to test their ORR / OER performance on a rotating disk electrode at 25°C. Specifically, 5 mg of the above sample (catalyst) + 5 mg of carbon powder + 2 mL of anhydrous ethanol + 80 μL of Nafion (5 wt%) were weighed, and then the mixed catalyst slurry was shaken in an ultrasonic cleaner for 1 hour to mix the catalyst evenly; 20 μL of the catalyst slurry was applied to the glassy carbon area on the rotating disk electrode, and the catalyst loading was 0.245 mg / cm 2 After natural air drying, the OER and ORR performances were tested as working electrodes in a three-electrode system, that is, a carbon rod was used as a counter electrode, a calomel electrode was used as a reference electrode, and the electrolyte was 0.1 M KOH solution. The catalytic performance of the catalyst was detected by a CHI760 electrochemical workstation with a rotation speed of 1600 rpm, a linear scan range of 0.2-1.0 (OER)-0.8-0.2 (ORR), a scan rate of 5 mV / s, an electrochemical impedance spectroscopy frequency range of 0.1-100000 Hz, and 85% solution resistance compensation.

[0054] Figure 4 a and Figure 4 b are the ORR / OER performance diagrams of Example 1, Comparative Examples 1, 2, and 3 in 0.1M KOH solution, respectively. It is obvious from the figure that the ORR / OER performance of SNCF-Mn-S4 in Example 1 is more superior, which makes the zinc-air composite battery prepared therefrom have better performance. It can be seen that the cathode material catalyst SNCF-Mn-S4 prepared in Example 1 has an electrochemical performance potential difference ΔE improvement of more than 100mV compared with SNCF-Mn obtained in Comparative Example 3.

[0055] Figure 5 The figure is a charge-discharge cycle diagram of the zinc-air composite battery prepared in Example 1. It can be seen from the figure that the zinc-air composite battery with the cathode made of sample SNCF-Mn-S4 shows excellent charge-discharge performance, and its charge-discharge cycle stability is very impressive, and it can operate stably within 500 hours; the power density of the prepared zinc-air composite battery reaches 135mW / cm 2 , the cycle efficiency reaches 75%.

[0056] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A method for preparing a cathode material catalyst for a zinc-air composite battery, characterized in that: The preparation method comprises the following steps: Step S1: Weighing niobium oxalate, strontium nitrate, cobalt nitrate, iron nitrate and manganese nitrate according to a certain stoichiometric ratio, and weighing a certain amount of citric acid and EDTA, adding the above raw materials into a reaction container, and synthesizing a SNCF-Mn gel precursor by a sol-gel method; Step S2: drying and sintering the SNCF-Mn gel precursor obtained in step S1 to obtain SNCF doped with Mn at the B site, referred to as SNCF-Mn; Step S3: placing a certain amount of the SNCF-Mn obtained in step S2 in a tubular furnace, heating it to 400° C. under an argon atmosphere for sulfurization operation, and obtaining the final product SNCF-Mn-S4 of the zinc-air composite battery cathode material catalyst.

2. The method for preparing a zinc-air composite battery cathode material catalyst according to claim 1, characterized in that: The cathode material catalyst SNCF-Mn-S4 obtained in step S3 has an electrochemical performance potential difference ΔE that is improved by more than 100 mV compared to the SNCF-Mn obtained in step S2.

3. The method for preparing a zinc-air composite battery cathode material catalyst according to claim 1, characterized in that: In step S1, the stoichiometric ratio of the molar number of all metal ions in the niobium oxalate, strontium nitrate, cobalt nitrate, iron nitrate and manganese nitrate to the molar number of EDTA and citric acid is: metal ion: EDTA: citric acid is 2:1:

4.

4. The method for preparing a cathode material catalyst for a zinc-air composite battery according to claim 1, characterized in that: In step S1, the raw materials are added into the reaction container in the order of niobium oxalate, citric acid, strontium nitrate, cobalt nitrate, iron nitrate, manganese nitrate and EDTA.

5. The method for preparing a cathode material catalyst for a zinc-air composite battery according to claim 1, characterized in that: In step S2, the drying operation conditions are a drying temperature of 180±5°C and a drying time of 2±0.5h, and the SNCF-Mn gel precursor is obtained in an expanded foam state; the sintering operation conditions are a calcination temperature of 1000±20°C and a calcination time of 12±0.5h.

6. The method for preparing a cathode material catalyst for a zinc-air composite battery according to claim 1, characterized in that: In step S2, the B-site Mn-doped SNCF has the general formula S(NCF) a Mn b ; Among them, the molar ratio of NCF element to Mn element at B position a:b is 0.95:0.05~0.5:0.

5.

7. The method for preparing a cathode material catalyst for a zinc-air composite battery according to claim 4, characterized in that: In step S2, the B-site Mn-doped SNCF has the general formula S(NCF) a Mn b ; Among them, the molar ratio of NCF element to Mn element at B position a:b is 0.65:0.

35.

8. The method for preparing a cathode material catalyst for a zinc-air composite battery according to claim 1, characterized in that: In step S3, when the temperature of the vulcanization operation rises to 400±10°C, the valve at one end of the tube furnace is closed to give the tube furnace a certain pressure. When the pressure of the tube furnace rises to 0.5±0.05 bar, the valves at both ends of the tube furnace are kept closed.

9. A zinc-air composite battery cathode material catalyst, characterized in that The cathode material catalyst is obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the zinc-air composite battery cathode material catalyst as claimed in claim 9, characterized in that: The cathode material catalyst and carbon powder are prepared into slurry in a ratio of 5 mg:5 mg, and then the slurry is evenly loaded on a 1×1 cm 2 The carbon cloth is used as the cathode of the zinc-air composite battery to make a zinc-air composite battery; wherein the power density of the zinc-air composite battery reaches 135mW / cm 2 , the cycle efficiency reaches 75%, and the charge and discharge cycle can operate stably for up to 500 hours.

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