Preparation method of manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery positive electrode material

Abstract

The present invention discloses for the first time a method for preparing a nitrogen-doped manganese vanadate micro-nano polyhedron structure material as a wide temperature range lithium-sulfur battery positive electrode sulfur skeleton material, which belongs to the field of energy material preparation. The method is to use a divalent manganese salt as a manganese source, a pentavalent vanadium salt as a vanadium source, and then adjust the pH value to 13-14, using a non-template method to prepare a polyhedron structure material morphology precursor; then calcined (4-12h) at 600-900 ° C to generate manganese vanadate polyhedrons; then annealed twice under a reducing atmosphere such as ammonia after hot-melt compounding with elemental sulfur at 140-180 ° C. The present invention does not need to use a template, the material has good stability, novel structure, and after being doped with nitrogen, the material surface electronic arrangement is changed, the crystal defects are increased, the material's adsorption capacity and catalytic effect on polysulfides are improved, and the utilization rate of active material sulfur in lithium-sulfur batteries and the shuttle effect generated during the battery reaction can be effectively improved in a wider temperature range. When the material is used for the positive electrode sulfur skeleton material of a lithium-sulfur battery, the battery can be made to have a better cycle life under a wide temperature range of high and low temperatures. This will enable lithium-sulfur batteries to be further put into practical use.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy material preparation, and relates to a method for preparing a lithium-sulfur battery positive electrode material that can alleviate the shuttle effect of lithium-sulfur batteries over a wide temperature range and improve the cycle stability of lithium-sulfur batteries. Background Art

[0002] Lithium-sulfur batteries are considered to be one of the most promising new energy storage systems due to their advantages such as ultra-high theoretical specific capacity (1675mAh / g) and theoretical energy density (2600Wh / kg), abundant sulfur reserves and low price. They can be applied to portable electronic products, electric vehicles and large-scale energy storage. However, lithium-sulfur batteries still have many problems and challenges, such as the extremely low electronic and ionic conductivity of the reactant element S8 and the final reduction products Li2S2 and Li2S in the battery system, the volume change of the electrodes during charge and discharge, and the generation of polysulfides soluble in the electrolyte by element S8 during the battery charge and discharge process, which easily shuttle to the battery negative electrode and deposit on the surface of the metallic lithium, causing irreversible loss of the battery active material. In addition, the battery electrode material has a volume expansion of up to 80% from the initial state to the final state, which will ultimately lead to low utilization of the active material of the lithium-sulfur battery and poor battery cycle stability, thus restricting the development and application of lithium-sulfur batteries. Incorporating sulfur framework materials into the cathode of lithium-sulfur batteries can effectively improve the electrode's conductivity, inhibit the shuttling effect of polysulfides, and catalyze sulfur conversion reactions. Currently, a significant amount of research is underway to address this issue. However, this work is conducted at room temperature. my country, with its vast territory and wide temperature ranges, also faces challenges in the complex operating environments of equipment using battery systems. Therefore, the ability of battery systems to operate properly across a wider temperature range, from high to low, is crucial.

[0003] Unlike traditional lithium-ion batteries, lithium-sulfur batteries experience a "shuttle effect" in which polysulfides, an intermediate product of the reaction process, reduce the battery's cycle stability. Furthermore, at high temperatures, the dissolution rate of polysulfides accelerates, increasing their solubility. This "shuttle effect" is significantly exacerbated, leading to a sharp decrease in the cycle life of lithium-sulfur batteries at high temperatures. Lithium-sulfur batteries are secondary batteries based on a multi-electron reaction mechanism, and the electrochemical reaction process involves multiple solid-liquid phase transitions. Therefore, their electrochemical reaction process is much more affected by low temperatures than traditional lithium-ion batteries.

[0004] Therefore, developing cathode materials that maintain excellent electrochemical performance under a wide temperature range of high and low temperatures is a major challenge in the field of lithium-sulfur batteries. Summary of the Invention

[0005] In order to achieve the above objectives, the technical solution of the present invention provides a method for preparing a positive electrode material that maintains excellent electrochemical performance in a wide temperature range of high and low temperatures, which includes the following:

[0006] A method for preparing a manganese vanadate-sulfur composite wide-temperature range lithium-sulfur battery cathode material, comprising the following steps:

[0007] S1. Dispersing or dissolving raw materials in solvent A to obtain raw material solution A; the raw materials include a divalent manganese metal compound and a pentavalent vanadium metal compound;

[0008] S2. Using solvent B, adjust the pH of the raw material solution A to 13-14 to obtain raw material solution B;

[0009] S3, reflux-heating the raw material solution B at a first predetermined temperature for a first predetermined time, centrifuging and washing, and obtaining a precursor;

[0010] S4, subjecting the precursor to a pyrolysis reaction to obtain a manganese vanadate polyhedron material;

[0011] S5, heating the manganese vanadate polyhedron material at a second predetermined temperature for a second predetermined time in a reducing nitrogen-containing atmosphere to obtain a nitrogen-doped manganese vanadate micro-nano polyhedron structure material;

[0012] S6. Mix the nitrogen-doped manganese vanadate micro-nano polyhedron structure material and elemental sulfur in a predetermined proportion, and heat-treat them at a third predetermined temperature for a third predetermined time to obtain a manganese vanadate-sulfur composite wide-temperature-range lithium-sulfur battery positive electrode material (nitrogen-doped manganese vanadate micro-nano polyhedron-sulfur composite material lithium-sulfur battery positive electrode material).

[0013] As one aspect of the present invention, the divalent manganese metal compound is one or more divalent nickel compounds such as manganese acetylacetonate, manganese acetate, manganese nitrate, and manganese carbonate.

[0014] As one aspect of the present invention, the pentavalent vanadium metal compound is one or more of ammonium metavanadate, sodium metavanadate, and potassium metavanadate.

[0015] As one aspect of the present invention, the solvent A further comprises one or more of ethanol, acetone, ethylene glycol, and glycerol.

[0016] As one aspect of the present invention, the solvent B further comprises one or more of ammonia water, sodium hydroxide solution, and potassium hydroxide.

[0017] As one aspect of the present invention, the first predetermined temperature is 120-200° C.; the first predetermined time is 1 to 3 hours.

[0018] As one aspect of the present invention, the temperature of the pyrolysis reaction is 500-920°C, the heating rate is 1-5°C / min, and the pyrolysis time is 2-4h.

[0019] As one aspect of the present invention, the reducing atmosphere is one of ammonia, ammonia-hydrogen mixture, and ammonia-nitrogen mixture, the second predetermined temperature is 700-900° C., and the second predetermined time is 1-3 hours.

[0020] As one aspect of the present invention, the third predetermined temperature is 140-180° C., and the third predetermined time is 4-6 hours.

[0021] As one aspect of the present invention, the solid obtained by centrifugation is washed with ethanol and deionized water to obtain a precursor.

[0022] The wide temperature range lithium-sulfur battery described in the present invention refers to a battery that uses lithium as an anode and sulfur as a cathode reactant and has an operating temperature of -40°C to 70°C.

[0023] After adopting the above scheme, the present invention has the following advantages:

[0024] 1. The method of the present invention is simple, easy to operate, has low temperature, simple post-processing, simple equipment requirements, moderate cost, and is suitable for large-scale production;

[0025] Second, the material has good stability and novel structure. After being doped with nitrogen, it will change the surface electron configuration of the material, increase the defects in the crystal, and enhance the material's adsorption capacity and catalytic effect on polysulfides. It can effectively improve the utilization rate of the active sulfur in lithium-sulfur batteries over a wider temperature range and inhibit the shuttle effect generated during the battery reaction.

[0026] 3. The positive electrode material synthesized by the method of the present invention enables the battery to have higher battery capacity and cycle stability in a wide temperature range.

[0027] In summary, the present invention discloses for the first time a method for preparing a nitrogen-doped manganese vanadate micro-nano polyhedron structure material as a sulfur skeleton material for a positive electrode of a wide temperature range lithium-sulfur battery. The method uses a divalent manganese salt as a manganese source and a pentavalent vanadium salt as a vanadium source, and then adjusts the pH value to 13-14 to prepare a polyhedron structure material morphology precursor using a non-template method; then calcining at 600-900°C (4-12h) to generate manganese vanadate polyhedrons; and then hot-melt compounding with elemental sulfur at 140-180°C and secondary annealing in a reducing atmosphere such as ammonia.

[0028] This invention eliminates the need for a template, boasts excellent material stability and a novel structure. Nitrogen doping modifies the material's surface electron configuration, increases defects within the crystal, and enhances its adsorption capacity and catalytic effect on polysulfides. This effectively increases the utilization of the active sulfur in lithium-sulfur batteries over a wider temperature range and suppresses the shuttle effect that occurs during battery reactions. When used as the sulfur framework for the positive electrode of lithium-sulfur batteries, this material can enhance the battery's cycle life across a wide temperature range, both high and low. This further advances the practical application of lithium-sulfur batteries.

[0029] With reference to the following description and the accompanying drawings, the specific embodiments of the present invention are disclosed in detail, indicating the manner in which the principles of the present invention can be employed. It should be understood that the embodiments of the present invention are not limited in scope thereby.

[0030] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0031] It should be emphasized that the term "include / comprising" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 This is a scanning electron microscope image of nitrogen-doped manganese vanadate polyhedrons prepared by the present invention;

[0034] Figure 2 The XRD pattern and EDS elemental analysis of nitrogen-doped manganese vanadate polyhedron prepared by the present invention are shown;

[0035] Figure 3 This is a cycle test of nitrogen-doped manganese vanadate polyhedron-S prepared by the method of the present invention at room temperature;

[0036] Figure 4 The test results of nitrogen-doped manganese vanadate polyhedron-S prepared by the method of the present invention were obtained under a wide temperature range.

[0037] Figure 5 It is a flow chart of the steps of the preparation method of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] Example 1:

[0041] Add 0.86g of manganese acetate and 0.89g of ammonium metavanadate to 100mL of ethylene glycol, stir until completely dissolved and transfer to a 200mL round-bottom flask. Use ammonia water to adjust the pH value of the solution to 13. Heat to 170°C under condensing conditions and maintain the temperature for 1.5h. After cooling to room temperature, centrifuge the solid and wash it with ethanol and deionized water several times, then vacuum dry at 80°C overnight. In an air atmosphere, calcine at 800°C for 6h with a heating rate of 5°C / min to obtain manganese vanadate. The obtained manganese vanadate is calcined at 800°C for 2h in an ammonia atmosphere to obtain the final product, nitrogen-doped manganese vanadate, with a micromorphology as shown below. Figure 1 As shown, it is a polyhedron with a diameter of about 500-1000 nanometers. The surface of the polyhedron is relatively smooth and the edges between the faces can be clearly seen.

[0042] like Figure 2 XRD data in

[15] showed that the material had standard characteristic peaks of manganese vanadate (MnV2O6), and EDS data in

[15] indicated that the nitrogen content in the material was approximately 4.24%. 0.5 g of the above material was mixed with 1.5 g of sublimed sulfur, stirred evenly, and heated at 155°C for 6 hours to obtain the finished product, a nitrogen-doped manganese vanadate-sulfur composite material.

[0043] The performance of this material as a positive electrode active material for lithium-sulfur batteries is as follows Figure 3 、 4As shown. At room temperature, the battery maintained a high capacity of 816 mAh g-1 after 350 cycles at a high current density of 2C. When tested at a current density of 1C over a wide temperature range, the battery released a discharge capacity of 1284 mAh g-1 at 70 degrees Celsius, with little apparent attenuation. At a low temperature of -20°C, the capacity remained at 625 mAh g-1, and at -40°C, it was 521 mAh g-1. Once the temperature returned to room temperature, the capacity also returned to its previous level.

[0044] Example 2:

[0045] Add 1.34g of manganese nitrate and 1.46g of sodium metavanadate to 150mL of ethylene glycol, stir until completely dissolved, and transfer to a 200mL round-bottom flask. Use sodium hydroxide to adjust the pH of the solution to 14. Heat to 180°C under condensing conditions and maintain the temperature for 2h. After cooling to room temperature, centrifuge the solid and wash it several times with ethanol and deionized water, then vacuum dry at 80°C overnight. In an air atmosphere, calcine at 700°C for 6h with a heating rate of 5°C / min to obtain the finished manganese vanadate. The obtained manganese vanadate is calcined at 900°C for 1h in a mixed atmosphere of ammonia and hydrogen to obtain the final product, nitrogen-doped manganese vanadate. Take 0.5g of the above material and mix it with 1.5g of sublimed sulfur, stir it evenly, and heat it at 155°C for 6h to obtain the finished product, nitrogen-doped manganese vanadate-sulfur composite material. This material is used as the positive electrode active material of lithium-sulfur batteries. The capacity of the battery is 1302mAh g-1 at 70°C under a current density of 1C, 630mAh g-1 at -20°C, and 532mAh g-1 at -40°C.

[0046] Example 3:

[0047] Add 1.27g of manganese acetylacetonate and 1.11g of potassium metavanadate to 100mL of glycerol, stir until completely dissolved, and transfer to a 200mL round-bottom flask. Adjust the pH of the solution to 14 with potassium hydroxide. Heat to 190°C under condensing conditions and maintain the temperature for 3 hours. After cooling to room temperature, centrifuge the solid and wash it multiple times with ethanol and deionized water, then vacuum dry at 80°C overnight. Calcinate at 700°C in an air atmosphere for 6 hours at a heating rate of 5°C / min to obtain the finished manganese vanadate. Calcine the resulting manganese vanadate at 700°C for 3 hours in a mixed atmosphere of ammonia and nitrogen to obtain the final product, nitrogen-doped manganese vanadate. Take 0.5g of the above material and mix it with 1.5g of sublimed sulfur, stir evenly, and heat it at 155°C for 6 hours to obtain the finished product, nitrogen-doped manganese vanadate-sulfur composite material. This material is used as the positive electrode active material of lithium-sulfur batteries. The capacity of the battery is 1250mAh g-1 at 70°C under a current density of 1C, 590mAh g-1 at -20°C, and 520mAh g-1 at -40°C.

[0048] Any numerical value cited herein includes all values ​​of the lower and upper values ​​in increments of one unit from the lower limit to the upper limit, and there is an interval of at least two units between any lower value and any higher value. For example, if the value of the quantity of a component or a process variable (such as temperature, pressure, time, etc.) is set forth to be from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, the purpose is to illustrate that values ​​such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also explicitly listed in this specification. For values ​​less than 1, one unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1. These are merely examples that are intended to be clearly expressed, and it can be considered that all possible combinations of the numerical values ​​listed between the minimum and maximum values ​​are explicitly set forth in this specification in a similar manner.

[0049] Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. When used with a range, "about" or "approximately" applies to both endpoints of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30," including at least the specified endpoints.

[0050] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the appended claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein from the foregoing claims is not intended to be a disclaimer of such subject matter, nor should it be assumed that the inventors did not consider such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A method for preparing a manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery cathode material, characterized in that: The following steps are involved: S1. Dispersing or dissolving raw materials in solvent A to obtain raw material solution A; the raw materials include a divalent manganese metal compound and a pentavalent vanadium metal compound; S2. Using solvent B, adjust the pH of the raw material solution A to 13-14 to obtain raw material solution B; S3, reflux-heating the raw material solution B at a first predetermined temperature for a first predetermined time, centrifuging and washing, and obtaining a precursor; S4, subjecting the precursor to a pyrolysis reaction to obtain a manganese vanadate polyhedron material; S5. Heating the manganese vanadate polyhedron material in a reducing nitrogen-containing atmosphere at a second predetermined temperature for a second predetermined time to obtain a nitrogen-doped manganese vanadate micro-nano polyhedron structure material; the reducing nitrogen-containing atmosphere is one of ammonia, ammonia-hydrogen mixture, and ammonia-nitrogen mixture; the second predetermined temperature is 700-900° C., and the second predetermined time is 1-3 hours; S6. Mix the nitrogen-doped manganese vanadate micro-nano polyhedron structure material and elemental sulfur in a predetermined ratio, and heat-treat them at a third predetermined temperature for a third predetermined time to obtain a manganese vanadate-sulfur composite wide-temperature-range lithium-sulfur battery positive electrode material.

2. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery positive electrode material according to claim 1, wherein: The divalent manganese metal compound is one or more of manganese acetylacetonate, manganese acetate, manganese nitrate, and manganese carbonate.

3. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery positive electrode material according to claim 1, wherein: The pentavalent vanadium metal compound is one or more of ammonium metavanadate, sodium metavanadate, and potassium metavanadate.

4. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery positive electrode material according to claim 1, wherein: The solvent A includes one or more of ethanol, acetone, ethylene glycol, and glycerol.

5. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery positive electrode material according to claim 1, wherein: The solvent B includes one or more of ammonia water and sodium hydroxide solution.

6. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery cathode material according to claim 1, wherein: The first predetermined temperature is 120-200° C.; the first predetermined time is 1-3 hours.

7. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery cathode material according to claim 1, wherein: The temperature of the pyrolysis reaction is 500-950° C., the heating rate is 1-5° C. / min, and the pyrolysis time is 2-4 h.

8. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery cathode material according to claim 1, wherein: The third predetermined temperature is 140-180° C., and the third predetermined time is 4-6 hours.

9. The method for preparing the manganese vanadate-sulfur composite wide temperature range lithium-sulfur battery cathode material according to claim 1, wherein: The solid centrifuged in step S3 is washed with ethanol and deionized water.

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