Low-polarization zinc-sulfur battery positive electrode material and preparation method thereof

Abstract

The invention provides a low-polarization zinc-sulfur battery positive electrode material and a preparation method thereof.The method comprises the steps that firstly, sulfur powder and tellurium powder are mixed and ground, then the mixture is transferred into a glass tube, the tube is sealed in a vacuum mode, then the tube is transferred into heating equipment to be calcined, and a precursor material is obtained; and mixing and grinding the prepared precursor material and carbon, sealing the tube in vacuum again, transferring the tube into heating equipment, and calcining to obtain TeySx / C powder, namely the low-polarization aqueous zinc-sulfur positive electrode material. The prepared low-polarization aqueous zinc-sulfur positive electrode material not only reduces the phase change energy barrier in the sulfur reduction process and accelerates the transfer of electrons / Zn < 2 + >, but also can improve the catalytic efficiency of a catalyst in an electrolyte so as to promote the sulfur oxidation process. The aqueous zinc-sulfur battery assembled based on the TeySx / C positive electrode material shows low polarization, high discharge platform, high rate capacity and excellent cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous zinc-ion batteries, and in particular, to a low-polarization zinc-sulfur battery cathode material and a preparation method thereof. More specifically, the present invention relates to a method for preparing Te y S x / C zinc-sulfur battery cathode material by a vacuum-sealed tube high-temperature calcination method. Background Art

[0002] The rapid growth of global energy demand has driven the research interest in high-safety and high-energy-density batteries. Aqueous zinc-ion batteries have attracted increasing attention from researchers due to their high safety, environmental friendliness, and rich resources. However, limited by the intercalation mechanism cathode materials, such as vanadium-based materials, manganese-based materials, Prussian blue analogs, and polymers, the low specific capacity (usually less than 400 mAh g -1 ) and the limited aqueous electrochemical stability window lead to the low energy density of aqueous zinc-ion batteries, making it difficult to meet the requirements of high-energy-density batteries. The sulfur cathode material with a conversion mechanism has advantages such as a high theoretical specific capacity (1675 mAh g -1 ) and low cost. When paired with a zinc anode to form an aqueous zinc-sulfur battery, an energy density of up to 577 Wh kg -1 can be achieved based on a theoretical voltage of 1.04 V, showing great advantages in realizing high-safety and high-energy-density batteries. However, due to the high energy barrier in the structure decomposition / formation during the conversion process and the electro-neutral characteristics of sulfur and its discharge product zinc sulfide, the slow solid-solid reaction kinetics is caused. Furthermore, in actual tests, aqueous zinc-sulfur batteries usually suffer from large polarization, rapid capacity decay, and limited energy density.

[0003] Therefore, there is an urgent need in the industry to develop a new technology for a low-polarization aqueous zinc-sulfur cathode material and its preparation method. Summary of the Invention

[0004] To solve the problems existing in the above-mentioned prior art, the present invention provides a low-polarization zinc-sulfur battery cathode material and a preparation method thereof. Specifically, Te y S x / C zinc-sulfur battery cathode material is prepared by a vacuum-sealed tube high-temperature calcination method. The ingenious design of the Te y S x / C zinc-sulfur battery cathode material of the present invention can solve the pain point of low polarization of aqueous zinc-sulfur batteries and improve their energy density. The cathode material not only reduces the phase transition energy barrier during the sulfur reduction process and accelerates the transfer of electrons / Zn 2+ , but also can improve the catalytic efficiency of the catalyst in the electrolyte to promote the sulfur oxidation process.

[0005] To achieve the above object, the present invention provides a method for preparing a cathode material for a zinc-sulfur battery, comprising the following steps:

[0006] Step 1: Mix and grind sulfur powder and tellurium powder to obtain a mixed powder;

[0007] Step 2: Vacuum seal the mixed powder obtained in Step 1, transfer it to a heating device, and calcine it at a high temperature to obtain a precursor powder;

[0008] Step 3: Mix and grind the precursor powder obtained in Step 2 with carbon to obtain a mixed powder of the precursor and carbon;

[0009] Step 4: Vacuum seal the mixed powder of the precursor and carbon obtained in Step 3, transfer it to a heating device, and calcine it at a high temperature to obtain Te y S x / C powder, which is the low-polarization aqueous zinc-sulfur cathode material.

[0010] Further, in Step 1, the molar ratio of the sulfur powder to the tellurium powder is 0.9:0.02 - 0.225.

[0011] Further, in Step 2, the specific process of the high-temperature calcination is as follows: at a heating rate of 1 - 5 °C / min, raise the temperature from room temperature to 460 - 550 °C, keep it warm for 8 - 12 h, and then naturally cool to room temperature.

[0012] Further, in Step 2, the heating device is a muffle furnace or a tube furnace.

[0013] Further, in Step 3, the carbon is any one of hollow carbon spheres, Ketjen black, mesoporous carbon, and activated carbon.

[0014] Further, in Step 3, the mass ratio of the precursor powder to the carbon is 0.5 - 4:1.

[0015] Further, in Step 4, the mixed powder of the precursor and carbon obtained in Step 3 is calcined using a heating device, and the specific process of the high-temperature calcination is as follows: at a heating rate of 1 - 5 °C / min, raise the temperature from room temperature to 300 - 550 °C, keep it warm for 8 - 12 h, and then naturally cool to room temperature.

[0016] The present invention also provides a low-polarization zinc-sulfur battery cathode material prepared by the above preparation method.

[0017] The present invention has the following beneficial effects:

[0018] The present invention provides a low-polarization zinc-sulfur battery cathode material and a preparation method thereof. The method specifically includes: first, sulfur powder (S) and tellurium powder (Te) are mixed and ground according to a certain molar ratio, then transferred to a glass tube, vacuum-sealed, and then transferred to a heating device for calcination to obtain a precursor material. The prepared precursor material is mixed and ground with carbon, and then vacuum-sealed and transferred to a heating device for calcination again to obtain a Te y S x / C cathode material. In the low-polarization aqueous zinc-sulfur cathode material prepared by the present invention, most of the Te bonds with S to form Te-S bonds, and a small part of Te is uniformly distributed in the cathode in the form of elemental substance. Among them, the bonded Te with strong electron donor characteristics can not only cause atomic-scale strain inside the S8 ring to weaken the S-S bond strength, reduce the phase transition energy barrier during the sulfur reduction process, and accelerate the entry of Zn 2+ but also establish an internal electron transfer channel to accelerate electron transfer. The in-situ formed elemental Te has a low surface charge density and can adsorb a large amount of catalytic components in the electrolyte as a co-catalyst, acting as a bridge between the catalyst and the reaction active center, thereby enhancing the catalytic efficiency of the catalyst to further promote the sulfur oxidation process. Benefiting from the two-way promotion of the sulfur oxidation and reduction processes, the aqueous zinc-sulfur battery assembled based on the Te y S x / C cathode material exhibits low polarization, a high discharge platform, high rate capacity, and excellent cycling performance.

[0019] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the drawings to further elaborate on the present invention in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0021] Figure 1 is the XRD comparison diagram of the precursor powder, sulfur powder, and tellurium powder prepared in Example 1 of the present invention;

[0022] Figure 2 is the XPS comparison diagram of the precursor powder, sulfur powder, and tellurium powder prepared in Example 1 of the present invention;

[0023] Figure 3 is the Raman comparison diagram of the precursor powder, sulfur powder, and tellurium powder prepared in Example 1 of the present invention;

[0024] Figure 4 is the XRD diagram of the Te y S x / C powder prepared in Example 1 of the present invention;

[0025] Figure 5 is Te prepared in Example 1 of the present invention y S x SEM and elemental distribution maps of S / C powder

[0026] Figure 6 is Te prepared in Example 1 of the present invention y S x XPS analysis diagrams of S / C powder prepared in Example 1 of the present invention and S / C powder prepared in Comparative Example 1

[0027] Figure 7 are charge-discharge curves of the battery assembled with the positive electrode material prepared in Example 1 of the present invention and the battery assembled with the positive electrode material prepared in Comparative Example 1 at 0.1 Ag -1 under the following conditions

[0028] Figure 8 are cycle performance diagrams of the battery assembled with the positive electrode material prepared in Example 1 of the present invention and the battery assembled with the positive electrode material prepared in Comparative Example 1

[0029] Figure 9 are comparative diagrams of the electrochemical performance of the battery assembled with the positive electrode material prepared in Example 1 of the present invention and the battery assembled with the positive electrode material prepared in Comparative Examples 6-7; among them Figure 9 (a) is a comparative diagram of the cycle performance of Example 1 of the present invention and Comparative Examples 6-7; (b) is a comparative diagram of the impedance curves of Example 1 of the present invention and Comparative Examples 6-7, (c) is a comparative diagram of the fitted R ct value diagram, (d) is an equivalent circuit diagram related to fitting Detailed implementation manners

[0030] The following will describe the embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention can be implemented in many different ways defined and covered by the claims

[0031] Example 1

[0032] A preparation method of a positive electrode material for a low-polarization zinc-sulfur battery, comprising the following steps

[0033] Step 1: Mix and grind sulfur powder and tellurium powder in a molar ratio of 0.9:0.1 to obtain a mixed powder

[0034] Step 2: Vacuum seal the powder obtained in Step 1, transfer it to a muffle furnace, and calcine it at a heating rate of 5 °C per minute to 460 °C for 12 h to obtain a precursor powder

[0035] Step 3: Mix and grind the precursor powder obtained in Step 2 and Ketjen black in a mass ratio of 1.2:1 to obtain a mixed powder of the precursor and Ketjen black

[0036] Step 4: Vacuum seal the mixed powder obtained in Step 3, transfer it to a muffle furnace, and calcine it at a heating rate of 5 °C per minute to 460 °C for 12 hours of heat preservation to obtain Te y S x / C powder, which is the aqueous zinc-sulfur cathode material described above.

[0037] Example 2

[0038] A preparation method of a low-polarization zinc-sulfur battery cathode material, comprising the following steps:

[0039] Step 1: Mix and grind sulfur powder and tellurium powder according to a molar ratio of 0.9:0.02 to obtain a mixed powder;

[0040] Step 2: Vacuum seal the powder obtained in Step 1, transfer it to a muffle furnace, and calcine it at a heating rate of 5 °C per minute to 460 °C for 12 hours of heat preservation to obtain a precursor powder;

[0041] Step 3: Mix and grind the precursor powder obtained in Step 2 and Ketjen black according to a mass ratio of 0.5:1 to obtain a mixed powder of the precursor and Ketjen black;

[0042] Step 4: Vacuum seal the mixed powder obtained in Step 3, transfer it to a muffle furnace, and calcine it at a heating rate of 1 °C per minute to 300 °C for 12 hours of heat preservation to obtain Te y S x / C powder, which is the aqueous zinc-sulfur cathode material described above.

[0043] Example 3

[0044] A preparation method of a low-polarization zinc-sulfur battery cathode material, comprising the following steps:

[0045] Step 1: Mix and grind sulfur powder and tellurium powder according to a molar ratio of 0.9:0.225 to obtain a mixed powder;

[0046] Step 2: Vacuum seal the powder obtained in Step 1, transfer it to a muffle furnace, and calcine it at a heating rate of 5 °C per minute to 460 °C for 12 hours of heat preservation to obtain a precursor powder;

[0047] Step 3: Mix and grind the precursor powder obtained in Step 2 and Ketjen black according to a mass ratio of 4:1 to obtain a mixed powder of the precursor and Ketjen black;

[0048] Step 4: Vacuum seal the mixed powder obtained in Step 3, transfer it to a muffle furnace, and calcine it at a heating rate of 5 °C per minute to 550 °C for 8 hours of heat preservation to obtain Te y S x / C powder, which is the aqueous zinc-sulfur cathode material described above.

[0049] Comparative Example 1 (without Te)

[0050] A preparation method of a low-polarization zinc-sulfur battery cathode material, comprising the following steps:

[0051] Step 1: Mix and grind sulfur powder and Ketjen black according to a mass ratio of 1.2:1 to obtain a mixed powder;

[0052] Step 2: Vacuum seal the powder obtained in Step 1, transfer it to a muffle furnace, and calcine it at a heating rate of 5 °C per minute to 160 °C, and keep it warm for 12 h to obtain S / C powder;

[0053] Comparative Example 2 (without S)

[0054] A preparation method of a low-polarization zinc-sulfur battery cathode material, comprising the following steps:

[0055] Step 1: Mix and grind tellurium powder and Ketjen black according to a mass ratio of 1.2:1 to obtain a mixed powder;

[0056] Step 2: Vacuum seal the powder obtained in Step 1, transfer it to a muffle furnace, and calcine it at a heating rate of 5 °C per minute to 460 °C, and keep it warm for 12 h to obtain Te / C powder;

[0057] Comparative Example 3 (different carbon sources)

[0058] The difference between Comparative Example 3 and Example 1 is that activated carbon is used as the carbon source, and the others are the same as Example 1.

[0059] Comparative Example 4 (too high temperature)

[0060] The difference between Comparative Example 4 and Example 1 is that the calcination temperature is 600 °C, and the others are the same as Example 1.

[0061] Comparative Example 5 (too low temperature)

[0062] The difference between Comparative Example 5 and Example 1 is that the calcination temperature is 250 °C, and the others are the same as Example 1.

[0063] Comparative Example 6 (too high S content)

[0064] The difference between Comparative Example 6 and Example 1 is that the molar ratio of sulfur powder to tellurium powder is 0.9:0.01, and the others are the same as Example 1.

[0065] Comparative Example 7 (too high Te content)

[0066] The difference between Comparative Example 7 and Example 1 is that the molar ratio of sulfur powder to tellurium powder is 0.9:0.3, and the others are the same as Example 1.

[0067] Figure 1XRD comparison diagrams of the precursor powder, sulfur powder, and tellurium powder prepared in Example 1 of the present invention; among them, the XRD diffraction peaks of the precursor powder in Example 1 are similar to the S phase, indicating that the introduction of Te does not change the crystal structure of S. It is worth noting that the main diffraction peak of Example 1 is shifted to 23.1° to the left compared to S, which is attributed to the substitution of S atoms by Te atoms with a larger ionic radius, resulting in atomic-scale strain inside the S8 ring, suggesting the formation of Te-S bonds. At the same time, the diffraction peak of the precursor powder in Example 1 at 27.7° is significantly enhanced, and the diffraction peak at this position overlaps with the main diffraction peak of tellurium powder, indicating that elemental Te may exist in the precursor powder of Example 1. To further confirm the above results, XPS analysis was performed on the precursor powder, sulfur powder, and tellurium powder prepared in Example 1, as Figure 2 shown. In the Te 3d spectrum, a peak located at 573.2 eV was detected, which can be attributed to the characteristic peak of Te-Te bonds, meaning that elemental Te exists in the precursor powder of Example 1. In addition, the peak located at 574.4 eV can be attributed to Te-S bonds, proving that Te has successfully entered the inside of the S8 ring. Similar results were also confirmed in the Raman spectra of the precursor powder, sulfur powder, and tellurium powder prepared in Example 1, as Figure 3 shown. For the precursor powder of Example 1, in addition to the Raman characteristic peaks of S, a new Raman peak was also detected at 342 cm -1 , which is attributed to the stretching vibration of Te-S bonds. At the same time, a weak Raman signal peak at 120 cm -1 was also detected, which is attributed to the Raman peak of elemental Te. These results indicate that the precursor powder of Example 1 with Te-S bonds and elemental Te has been successfully constructed. The generation of internal stress in the S8 ring helps to weaken the internal S-S bonds to reduce the phase transition energy barrier during the S reduction process. At the same time, the entry of Te into the inside of the S8 ring also helps to adjust the electronic structure of the S8 ring to accelerate the electron transfer. In addition, the presence of elemental Te with a low surface charge density has a stronger affinity for the catalytic components in the electrolyte, which helps to improve the catalytic efficiency of the catalytic components.

[0068] Figure 4 XRD pattern of the Te y S x / C powder prepared in Example 1 of the present invention. As can be seen from Figure 4 , after the precursor powder prepared in Example 1 is mixed and calcined with Ketjenblack powder, only the XRD diffraction peaks of Te are shown, indicating the presence of elemental Te in Example 1. Further, Figure 5 XRD pattern of the Te y S x / C powder prepared in Example 1 of the present invention. SEM and elemental distribution maps of the Te Figure 5It can be seen that S and Te elements are evenly distributed on Ketjen black. Figure 6 is Te obtained in Example 1 of the present invention y S x XPS analysis diagrams of S / C powder obtained in Example 1, S / C powder obtained in Comparative Example 1, and tellurium powder. The results show that Te-S bonds and Te-Te bonds still exist in Example 1, indicating that the precursor powder in Example 1 is only physically mixed with Ketjen black and its inherent chemical properties have not changed after calcination. The purpose of mixing the precursor powder of Example 1 with Ketjen black is that Ketjen black, as a host material, can further improve the electronic conductivity of the precursor powder of Example 1 when the precursor powder is loaded on it. Combining these results shows that the cathode material of Example 1 is expected to promote the redox reaction of the aqueous zinc-sulfur battery to reduce polarization.

[0069] The materials obtained in Examples 1-3 and Comparative Examples 1-7 were used as the cathode, glass fiber as the separator, a blend solution of zinc trifluoromethanesulfonate / water / ether / iodine as the electrolyte, and zinc foil as the anode to assemble a button cell, and the electrochemical performance was tested using a BlueTEC electrochemical test system. The test conditions were: current density of 0.1 and 6 A g -1 , and the voltage range was 0.1-1.5 V.

[0070] Figure 7 are the charge-discharge curves of the battery assembled with the cathode material obtained in Example 1 of the present invention and the battery assembled with the cathode material obtained in Comparative Example 1 at 0.1 A g -1 . It can be seen from Figure 7 that the discharge mid-voltage of Example 1 is as high as 0.74 V, and the charge mid-voltage is only 1.13 V; the total voltage polarization is only 0.39 V, which is much smaller than 0.8 V of Comparative Example 1. And Example 1 also obtained an energy density of 872 Wh kg -1 (calculated based on sulfur). This result also verifies the superiority of Example 1 as a low-polarization aqueous zinc-sulfur cathode material due to the presence of Te-S bonds and elemental Te, and significantly improves the energy density of the aqueous zinc-sulfur battery. Further, Figure 8 are the cycle performance diagrams of the battery assembled with the cathode material obtained in Example 1 of the present invention and the battery assembled with the cathode material obtained in Comparative Example 1. It can be seen from Figure 8 that even when cycling at a high-rate current density, Example 1 still exhibits good cycle stability, and the capacity is still as high as 487 mAh g after cycling 2500 times at 6 A g -1 -1On the contrary, in Comparative Example 1, the capacity rapidly decayed in the early stage, and the battery failed after 700 cycles. Therefore, these results fully demonstrate that the formation of Te-S bonds changes the strain inside the S8 ring to weaken the S-S bonds, which significantly reduces the phase transition energy barrier of the sulfur reduction process and accelerates the entry of Zn 2+ . Meanwhile, the presence of the Te cocatalyst also further improves the catalytic efficiency of the catalytic components and significantly promotes the sulfur oxidation process. Benefiting from the promotion of the sulfur redox kinetics, an aqueous zinc-sulfur battery with excellent electrochemical performance is also obtained. The experimental performance of the positive electrode materials prepared in Example 2 and Example 3 is similar to that of Example 1 and will not be elaborated here.

[0071] In addition, Comparative Example 2 does not contain sulfur element compared with Example 1 and is not suitable as the positive electrode material of the aqueous zinc-sulfur battery. The difference between Comparative Example 3 and Example 1 lies in the different carbon sources. Activated carbon is used as the carbon source in Comparative Example 3. Compared with Ketjen black in Example 1, the specific surface area of activated carbon is smaller, which is not conducive to the infiltration of the electrolyte, limits the ion transport, and thus leads to poor utilization rate of the active material and exhibits a low specific capacity (usually lower than 800 mAh g -1 at a current density of 0.1 Ag -1 ). Comparative Example 4 adopted a higher calcination temperature compared with Example 1. The too high calcination temperature will lead to the loss of the sulfur source of the active material, resulting in an imbalance in the ratio of sulfur and tellurium, leading to too high tellurium content inside the material, and thus resulting in a decrease in the specific capacity (usually lower than 800 mAh g -1 at a current density of 0.1 Ag -1 ). Comparative Example 5 adopted a lower calcination temperature compared with Example 1, which will cause the precursor powder not to reach the melting point, so it cannot be melt-blended with the carbon source, which will lead to uneven distribution of the precursor powder on the carbon source, and further affect the utilization rate of the active material, and finally lead to a decrease in the specific capacity. From Example 1 and Comparative Examples 6-7 (as shown Figure 9 ), the S content in Comparative Example 6 is too high and its charge transfer resistance is higher, indicating that the electron transfer rate is too slow, resulting in a larger polarization. Although the charge transfer resistance of Comparative Example 7 with too high Te content is smaller, meaning faster electron transfer, too high Te will lead to a lower specific capacity of the material.

[0072] In summary, the present invention provides a preparation method of a positive electrode material for a low-polarization zinc-sulfur battery, which includes: first, mixing sulfur powder (S) and tellurium powder (Te) according to a certain molar ratio and grinding them, then transferring them into a glass tube, vacuum sealing the tube, and then transferring them into a heating device for calcination to obtain a precursor material. Mixing the prepared precursor material with carbon and grinding again, and then vacuum sealing the tube and transferring it into a heating device for calcination to obtain Te y S x / C cathode material. In this material, a part of Te bonds with S to form Te-S bonds, and a part of Te exists in the form of elemental substance. The bonded Te can not only establish an electron transfer channel inside the S8 ring to accelerate electron transfer, but also generate atomic-scale bond strain inside the S8 ring to weaken the S-S bond and promote sulfur reduction kinetics; elemental Te has a strong affinity for the catalyst in the electrolyte, can enrich the catalyst at the cathode and act as a bridge to connect the reaction active center and the catalyst to enhance the catalytic efficiency of the catalyst and promote sulfur oxidation kinetics. Therefore, based on Te y S x / C cathode material assembled aqueous zinc-sulfur battery exhibits excellent electrochemical performance.

[0073] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a low-polarization zinc-sulfur battery positive electrode material, characterized in that: The following steps are involved: Step 1, mixing sulfur powder and tellurium powder and grinding them to obtain mixed powder; Step 2, vacuum seal the mixed powder obtained in step 1, transfer it to a heating device for high-temperature calcination, and obtain a precursor powder; Step 3, mixing and grinding the precursor powder obtained in step 2 with carbon to obtain a mixed powder of the precursor and carbon; Step 4: The mixed powder of the precursor and carbon obtained in step 3 is sealed in a vacuum tube and transferred to a heating device for high-temperature calcination to obtain Te y S x / C powder is the low polarization zinc-sulfur positive electrode material.

2. The method for preparing a low polarization zinc-sulfur battery positive electrode material according to claim 1, characterized in that: In step 1, the molar ratio of the sulfur powder to the tellurium powder is 0.9:0.02-0.

225.

3. The method for preparing a low polarization zinc-sulfur battery positive electrode material according to claim 1, characterized in that: In step 2, the specific process of high temperature calcination is: heating from room temperature to 460-550° C. at a heating rate of 1-5° C. / min, keeping the temperature for 8-12 hours, and then naturally cooling to room temperature.

4. The method for preparing a low polarization zinc-sulfur battery positive electrode material according to claim 1, characterized in that: In step 2, the heating equipment is a muffle furnace or a tubular furnace.

5. The method for preparing a low polarization zinc-sulfur battery positive electrode material according to claim 1, characterized in that: In step 3, the carbon is any one of hollow carbon spheres, Ketjen black, mesoporous carbon and activated carbon.

6. The method for preparing a low polarization zinc-sulfur battery positive electrode material according to claim 1, characterized in that: In step 3, the mass ratio of the precursor powder to carbon is 0.5-4:

1.

7. The method for preparing a low polarization zinc-sulfur battery positive electrode material according to claim 1, characterized in that: In step 4, the mixed powder of the precursor and carbon obtained in step 3 is calcined using a heating device. The specific process of high-temperature calcination is: heating from room temperature to 300-550°C at a heating rate of 1-5°C / min, keeping warm for 8-12 hours, and then naturally cooling to room temperature.

8. A low polarization zinc-sulfur battery positive electrode material, characterized in that: The method is described in any one of claims 1 to 7.

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