Nickel single atom with coordination structure as well as preparation method and application of nickel single atom

Abstract

The invention relates to the technical field of electrode materials, and discloses a nickel single atom with a coordination structure and a preparation method and application of the nickel single atom with the coordination structure, and the general formula of the nickel single atom with the coordination structure is NiNxSy, wherein 3 > = x > = 1, 3 > = y > = 1; x and y are integers. The preparation method comprises the following steps: dispersing the Ni / ZIF-8 compound in a solvent in an inert gas atmosphere, mixing with a sulfur source, and pyrolyzing at 900-1200 DEG C for 1-4 hours to obtain the nickel monoatom with the coordination structure. The nickel monatomic with the coordination structure provided by the invention changes an electronic structure around a central Ni atom, so that the electron transfer capability of the nickel monatomic is enhanced, and electron transfer is promoted; and rich active sites are also provided, so that the polysulfide can be better anchored, the catalytic performance is improved, and the interaction between the nickel monatomic material with the coordination structure and the active substance sulfur and the oxidation-reduction reaction of the positive electrode of the lithium-sulfur battery are optimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and in particular relates to a nickel single atom with a coordination structure, a preparation method and an application thereof. Background Art

[0002] Lithium-sulfur batteries are widely considered to be one of the most promising next-generation battery technologies due to their high theoretical specific capacity (1675mAh / g) and low material cost. However, the shuttling effect of polysulfides in lithium-sulfur batteries, the electronic insulation of charge and discharge products, and the slow polysulfide conversion reaction kinetics limit the practical application of lithium-sulfur batteries. Therefore, introducing single-atom catalysts into lithium-sulfur batteries is one of the effective strategies to solve the problem of slow polysulfide conversion.

[0003] With MN x L y Metal single-atom catalysts with (M=Fe or Ni, L=S or P) structure have the advantages of unique electronic structure, high catalytic activity and good conductivity. They can not only firmly anchor polysulfides, but also accelerate the redox reaction of lithium-sulfur batteries.

[0004] However, existing metal single-atom catalysts still have some problems in practical applications, which are manifested in poor cycling at high rates. For example, the Fe-N prepared by GQCao et al. 4 / S 2 C, which provides 749mAh·g at 2.0C -1 The initial discharge capacity at 4.0C is only 465 mAh g -1 . Summary of the invention

[0005] The present invention provides a nickel single atom with a coordination structure and a preparation method and application thereof, which solves the problem of poor circulation of metal single atom catalysts constructed in the prior art at high rates.

[0006] The first aspect of the present invention provides a nickel single atom having a coordination structure, the general formula of which is NiN x S y ; Among them, 3≥x≥1, 3≥y≥1; x and y are both integers.

[0007] Preferably, comprising: NiN 3 S 1 、NiN 2 S 2 or NiN 1 S 3 .

[0008] The second object of the present invention is to protect the preparation method of the nickel single atom with a coordination structure, comprising:

[0009] In an inert gas atmosphere, the Ni / ZIF-8 complex is dispersed in a solvent, mixed with a sulfur source, and then pyrolyzed at 900-1200°C for 1-4 hours to obtain nickel single atoms with a coordination structure.

[0010] The pyrolysis process is as follows: the precursor powder is heated to 900-950°C and kept warm for 1-4 hours to form a coordination structure of NiN 3 S 1 The precursor powder is heated to 1000-1050°C for 1-4 hours to form a coordination structure of NiN 2 S 2 The precursor powder is heated to 1100-1150°C for 1-4 hours to form a coordination structure of NiN 1 S 3 The method can precisely control the coordination numbers of N and S by different pyrolysis temperatures.

[0011] The present invention introduces a sulfur source into the precursor, and is therefore equally applicable to different precursors. At the same time, the coordination environment can be precisely controlled by different temperature zones.

[0012] Preferably, the ratio of the Ni / ZIF-8 complex to the sulfur source is 50-300 mg: 10-100 μL.

[0013] Preferably, the sulfur source is any one of thiophene, carbon disulfide, thiophenol, sulfoxide, thioether and thiol.

[0014] Preferably, the heating rate during the pyrolysis is 5 to 7° C. / min.

[0015] Heating the temperature too quickly will result in incomplete coordination and carbonization, while heating the temperature too slowly will take too much time.

[0016] Preferably, the preparation method of the Ni / ZIF-8 composite is:

[0017] 2-methylimidazole, zinc source and nickel source are dispersed in a solvent, centrifuged and the solid is dried to obtain a Ni / ZIF-8 complex; wherein the mass ratio of the 2-methylimidazole, zinc source and nickel source is 10-13g:3-6g:200-300mg.

[0018] Preferably, the zinc source is zinc nitrate hexahydrate; the nickel source is one of nickel nitrate hexahydrate, nickel acetylacetonate, nickelocene, and nickel chloride hexahydrate.

[0019] The third object of the present invention is to protect the use of the nickel single atom with a coordination structure in the preparation of sulfur positive electrode materials.

[0020] A fourth object of the present invention is to protect a sulfur cathode material, comprising a sulfur cathode active material and the nickel single atom with a coordination structure supported on the sulfur cathode active material.

[0021] A fifth object of the present invention is to protect the preparation method of the sulfur positive electrode material as follows:

[0022] The nickel single atom with a coordination structure and elemental sulfur are mixed, and then heated at 120 to 160° C. for 10 to 12 hours to obtain the sulfur positive electrode material; wherein the mass ratio of the nickel single atom with a coordination structure to the elemental sulfur is 1:3.

[0023] A sixth object of the present invention is to protect a lithium-sulfur battery comprising the sulfur positive electrode material.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. NiN provided by existing technology 4 In contrast, the nickel single atom with a coordination structure provided by the present invention: NiN x S y Since the electronegativity of the S atom is lower than that of the N atom, the addition of the S atom will cause the metal cation in the MNC to deviate from the center, breaking the symmetric charge transfer and spin of the MN site, changing the electronic structure around the central Ni atom, and enhancing the ability of the nickel atom to transfer electrons, thereby promoting the transfer of electrons; the nickel atom coordinated by nitrogen and sulfur provides abundant active sites, which is conducive to better anchoring polysulfides, improving catalytic performance, optimizing the interaction between the nickel atom material with a coordination structure and the active substance sulfur, as well as the redox reaction of the positive electrode of the lithium-sulfur battery, and proposing related mechanisms of action. At the same time, with the introduction of sulfur coordination, the porosity of the material also increases, and the porous structure and large specific surface area effectively guarantee the physical adsorption of the active substance. The prior art also provides an iron atom with a coordination structure: Fe-N 4 / S 2 C provides electrons to nearby N through the second coordinated CSC bond, thereby increasing the electron density of the central Fe. The two Ss are coordinated in the second shell, which only changes the coordination structure of the second shell, and the first shell does not change. Under 4C conditions, the initial discharge capacity is only 465 mAh g -1 In the present invention, NiN x S y The first coordinated S atom provides electrons to the N atom, thereby increasing the electron density of the central Ni. All S atoms are coordinated in the first shell, so that electron transfer can be performed more quickly, thereby promoting the conversion of sulfur species more quickly and improving the electrochemical performance of Li-S. The NiN prepared by the present invention 3 S1 、NiN 1 S 3 It is an asymmetric coordination. It has been reported in the literature that asymmetric coordination has better performance than symmetric coordination.

[0026] 2. The method for preparing nickel single atoms with coordination structures provided by the present invention is that the three types of nickel single atoms with coordination structures are relatively stable, and each type can be separated separately; by controlling the pyrolysis temperature to accurately control the different N and S coordination ratios, the doping of N atoms will cause a partial loss at high temperatures, the higher the temperature, the faster the loss, and the more sulfur atoms are doped. The present invention is to introduce a sulfur source into the precursor, so it is also applicable to different precursors.

[0027] 3. Fe-N prepared by existing technology 4 / S 2 When C is used as the sulfur cathode material of lithium-sulfur batteries, the initial discharge capacity is only 465 mAh g at 4C. -1 When the nickel single atom with coordination structure provided by the present invention is used as sulfur positive electrode material of lithium-sulfur battery, the initial discharge capacity is as high as 627 mAh g at 4.0C. -1 At 5.0C, the initial discharge capacity is as high as 609mAh·g -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The NiN prepared in Example 9 of the present invention 3 S 1 Transmission electron microscopy image of a single nickel atom with a coordinated structure;

[0029] Figure 2 The NiN prepared in Example 9 of the present invention 3 S 1 Scanning electron micrograph of the coordinated structure of a single nickel atom;

[0030] Figure 3 The NiN prepared in Example 9 of the present invention 2 S 2 Transmission electron microscopy image of a single nickel atom with a coordinated structure;

[0031] Figure 4 The NiN prepared in Example 9 of the present invention 2 S 2 Scanning electron micrograph of the coordinated structure of a single nickel atom;

[0032] Figure 5 The NiN prepared in Example 9 of the present invention 1 S 3 Transmission electron microscopy image of a single nickel atom with a coordinated structure;

[0033] Figure 6 The NiN prepared in Example 9 of the present invention 1 S 3 Scanning electron micrograph of the coordinated structure of a single nickel atom;

[0034] Figure 7 The NiN prepared in Example 5 of the present invention x S y X-ray diffraction pattern of nickel single atom with coordinated structure;

[0035] Figure 8 It is a rate performance diagram of the sulfur positive electrode material prepared in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0036] The technical solutions in the present invention will be described clearly and completely below in conjunction with the specific implementation of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The methods described in the embodiments of the present invention are conventional methods unless otherwise specified. The materials, reagents, etc. used can be obtained from commercial sources unless otherwise specified.

[0038] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. Among them, A and B can be singular or plural; the single symbol " / " means "or".

[0039] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of A, B or C", or "at least one of A, B and C" can represent any one of A, B, C, or A+B, or A+C, or B+C, or A+B+C, where A, B, C can be single or multiple, respectively.

[0040] In the following description of this embodiment, the order of serial numbers does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of this embodiment.

[0041] In the following description of the present embodiment, the numerical range should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Any stated value or intermediate value in the stated range and any other stated value or each smaller range between the intermediate values ​​in the stated range are also included in the present embodiment, and the upper and lower limits of the smaller range can be independently included or excluded in the range.

[0042] Unless otherwise stated, the technical / scientific terms used in the present embodiment have the same meanings as those generally understood by those skilled in the art to which the present application belongs. Although the present application only describes preferred methods and materials, any similar or equivalent methods and materials may also be used in the implementation or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

[0043] In the embodiment of the present invention, NSC represents a nitrogen-sulfur co-doped carbon substrate material, namely ZIF-8.

[0044] Example 1

[0045] A method for preparing a nickel single atom with a coordination structure:

[0046] Step 1, weigh 10 g of 2-methylimidazole, 3 g of zinc nitrate hexahydrate and 200 mg of nickel acetylacetonate and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 24 hours, centrifuge and dry them to constant weight in a vacuum environment at 60° C. to obtain the Ni / ZIF-8 complex.

[0047] Step 2: Disperse 50 mg of the Ni / ZIF-8 complex obtained in step 1 in anhydrous ethanol, add 10 μL of thiophene, ultrasonically treat for 2 h, stir for 5 h, centrifuge, and vacuum dry to constant weight at 60°C to obtain a precursor powder.

[0048] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0049] A method for preparing a sulfur cathode material, comprising:

[0050] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0051] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0052] Example 2

[0053] A method for preparing a nickel single atom with a coordination structure:

[0054] Step 1, weighing 10 g of 2-methylimidazole, 3 g of zinc nitrate hexahydrate and 200 mg of nickel nitrate hexahydrate, respectively, and dissolving them in an equal volume of anhydrous methanol, then quickly mixing and stirring the above solutions for 20 hours, centrifuging and drying them at 30° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0055] Step 2, take 50 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, add 10 μL of thiophene, ultrasonically treat for 0.5 h, stir for 4 h, centrifuge, and vacuum dry to constant weight at 30° C. to obtain a precursor powder.

[0056] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0057] A method for preparing a sulfur cathode material, comprising:

[0058] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0059] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0060] Example 3

[0061] A method for preparing a nickel single atom with a coordination structure:

[0062] Step 1, weigh 10g of 2-methylimidazole, 3g of zinc nitrate hexahydrate and 200mg of nickelocene and dissolve them in equal volumes of anhydrous methanol respectively, then quickly mix and stir the above solutions for 26h, centrifuge and dry them at 40°C under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0063] Step 2, take 50 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, disperse it in a mixed solution of 10 μL of thiophene and anhydrous ethanol, ultrasonically treat it for 1 hour, stir it for 5 hours, centrifuge it, and vacuum dry it to constant weight at a drying temperature of 40°C to obtain a precursor powder.

[0064] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0065] A method for preparing a sulfur cathode material, comprising:

[0066] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0067] The obtained sulfur positive electrode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur positive electrode by an electrode coating method.

[0068] Example 4

[0069] A method for preparing a nickel single atom with a coordination structure:

[0070] Step 1, weigh 10g of 2-methylimidazole, 3g of zinc nitrate hexahydrate and 200mg of nickel chloride hexahydrate and dissolve them in an equal volume of anhydrous methanol respectively, then quickly mix and stir the above solutions for 30h, centrifuge and dry at 70°C under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0071] Step 2, take 50 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, add 10 μL of thiophene, ultrasonically treat for 3 hours, stir for 7 hours, centrifuge, and vacuum dry to constant weight at a drying temperature of 70° C. to obtain a precursor powder.

[0072] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0073] A method for preparing a sulfur cathode material, comprising:

[0074] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0075] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0076] Example 5

[0077] A method for preparing a nickel single atom with a coordination structure:

[0078] Step 1, weigh 11 g of 2-methylimidazole, 5 g of zinc nitrate hexahydrate and 250 mg of nickel acetylacetonate and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 24 hours, centrifuge and dry them at 60° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0079] Step 2, take 50 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 2 hours, stir for 5 hours, centrifuge, and vacuum dry to constant weight at 60°C to obtain a precursor powder.

[0080] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0081] A method for preparing a sulfur cathode material, comprising:

[0082] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0083] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0084] Example 6

[0085] A method for preparing a nickel single atom with a coordination structure:

[0086] Step 1, weigh 11 g of 2-methylimidazole, 5 g of zinc nitrate hexahydrate and 250 mg of nickel nitrate hexahydrate and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 20 hours, centrifuge and dry them at 30° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0087] Step 2, take 50 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 0.5 h, stir for 4 h, centrifuge, and vacuum dry to constant weight at 30° C. to obtain a precursor powder.

[0088] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0089] A method for preparing a sulfur cathode material, comprising:

[0090] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0091] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0092] Example 7

[0093] A method for preparing a nickel single atom with a coordination structure:

[0094] Step 1, weigh 11 g of 2-methylimidazole, 5 g of zinc nitrate hexahydrate and 250 mg of nickelocene and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 26 hours, centrifuge and dry them at 40° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0095] Step 2, take 50 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 1 hour, stir for 5 hours, centrifuge, and vacuum dry to constant weight at a drying temperature of 40° C. to obtain a precursor powder.

[0096] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0097] A method for preparing a sulfur cathode material, comprising:

[0098] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0099] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0100] Example 8

[0101] A method for preparing a nickel single atom with a coordination structure:

[0102] Step 1, weigh 11 g of 2-methylimidazole, 5 g of zinc nitrate hexahydrate and 250 mg of nickel chloride and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 30 hours, centrifuge and dry them at 70° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0103] Step 2, take 50 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 3 hours, stir for 7 hours, centrifuge, and vacuum dry to constant weight at a drying temperature of 70° C. to obtain a precursor powder.

[0104] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0105] A method for preparing a sulfur cathode material, comprising:

[0106] The obtained NiN 3 S1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0107] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0108] Example 9

[0109] A method for preparing a nickel single atom with a coordination structure:

[0110] Step 1, weigh 13g of 2-methylimidazole, 6g of zinc nitrate hexahydrate and 300mg of nickel acetylacetonate and dissolve them in an equal volume of anhydrous methanol respectively, then quickly mix and stir the above solutions for 20 to 30h, centrifuge and dry to constant weight at 30 to 70°C under vacuum to obtain the Ni / ZIF-8 complex.

[0111] Step 2: Disperse 100 mg of the Ni / ZIF-8 complex obtained in step 1 in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 2 h, stir for 5 h, centrifuge, and vacuum dry to constant weight at 60° C. to obtain a precursor powder.

[0112] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1S 3 -Nickel single atoms from NSC.

[0113] A method for preparing a sulfur cathode material, comprising:

[0114] Step 4: NiN obtained in step 3 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0115] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0116] Example 10

[0117] A method for preparing a material having a coordination structure:

[0118] Step 1, weigh 13 g of 2-methylimidazole, 6 g of zinc nitrate hexahydrate and 300 mg of nickel nitrate hexahydrate and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 20 hours, centrifuge and dry them at 30° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0119] Step 2, take 100 mg of the Ni / ZIF-8 complex obtained in step 1 and disperse it in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 0.5 h, stir for 4 h, centrifuge, and vacuum dry to constant weight at 30° C. to obtain a precursor powder.

[0120] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1-NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0121] A method for preparing a sulfur cathode material, comprising:

[0122] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 120°C, and kept warm for 10 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0123] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding nickel single atom-sulfur cathode material by an electrode coating method.

[0124] Embodiment 11

[0125] A method for preparing a material having a coordination structure:

[0126] Step 1, weigh 13 g of 2-methylimidazole, 6 g of zinc nitrate hexahydrate and 300 mg of nickelocene and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 26 hours, centrifuge and dry them at 40° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0127] Step 2: Disperse 100 mg of the Ni / ZIF-8 complex obtained in step 1 in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 1 h, stir for 5 h, centrifuge, and vacuum dry to constant weight at 40° C. to obtain a precursor powder.

[0128] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0129] A method for preparing a sulfur cathode material, comprising:

[0130] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 140 ° C, and kept warm for 11 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0131] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0132] Example 12

[0133] A method for preparing a material having a coordination structure:

[0134] Step 1, weigh 13 g of 2-methylimidazole, 6 g of zinc nitrate hexahydrate and 300 mg of nickel chloride and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 30 hours, centrifuge and dry them at 70° C. under vacuum to constant weight to obtain the Ni / ZIF-8 complex.

[0135] Step 2: Disperse 100 mg of the Ni / ZIF-8 complex obtained in step 1 in anhydrous ethanol, add 50 μL of thiophene, ultrasonically treat for 3 h, stir for 7 h, centrifuge, and vacuum dry to constant weight at 70° C. to obtain a precursor powder.

[0136] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, and heat to 900°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere; cool the furnace to room temperature to obtain a NiN 3 S 1 -NSC nickel single atom; heated to 1000℃ and maintained for 3h; cooled down to room temperature, the coordination structure of NiN 2 S 2 -NSC nickel single atom; heated to 1100℃ and maintained for 3h; cooled to room temperature, the coordination structure of NiN 1 S 3 -Nickel single atoms from NSC.

[0137] A method for preparing a sulfur cathode material, comprising:

[0138] The obtained NiN 3 S 1 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 3 S 1 . Will NiN 2 S 2 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 2 S 2 .NiN 1 S 3 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 160°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 1 S 3 .

[0139] The obtained sulfur cathode material was uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then 32 drops of N-methylpyrrolidone were added to obtain the corresponding sulfur cathode by an electrode coating method.

[0140] The preparation method of the coordination-controllable nickel single atom-sulfur positive electrode material provided by the present invention improves the utilization rate of the active material through the good anchoring effect of nitrogen, sulfur and nickel atoms on polysulfides, and the carbon material with a porous structure further provides physical adsorption for polysulfides. Most importantly, the introduction of nitrogen and sulfur atoms changes the surrounding environment of the central nickel atom, further improves the activity of the nickel single atom catalyst, optimizes the interaction between the coordination-controllable nickel single atom material and the active substance sulfur, and improves the reaction kinetics of the sulfur positive electrode of the lithium-sulfur battery.

[0141] Comparative Example 1

[0142] A method for preparing a material having a coordination structure:

[0143] Step 1, weigh 10 g of 2-methylimidazole, 3 g of zinc nitrate hexahydrate and 200 mg of nickel acetylacetonate and dissolve them in an equal volume of anhydrous methanol, then quickly mix and stir the above solutions for 24 hours, centrifuge and dry them to constant weight in a vacuum environment at 60° C. to obtain the Ni / ZIF-8 complex.

[0144] Step 2: Disperse 50 mg of the Ni / ZIF-8 complex obtained in step 1 in anhydrous ethanol, add 10 μL of thiophene, ultrasonically treat for 2 h, stir for 5 h, centrifuge, and vacuum dry to constant weight at 60°C to obtain a precursor powder.

[0145] Step 3: transfer the precursor powder obtained in step 2 to a tube furnace, heat to 800°C and maintain for 3 hours at a heating rate of 5°C / min under an argon atmosphere, and cool to room temperature to obtain a NiN 4 -Nickel single atoms from NSC.

[0146] A method for preparing a sulfur cathode material, comprising:

[0147] The obtained NiN 4 -NSC nickel single atoms and elemental sulfur were uniformly mixed in a mass ratio of 1:3, heated to 155°C, and kept warm for 12 hours to obtain the sulfur positive electrode material, namely S@NiN 4 .

[0148] The obtained sulfur cathode material S@NiN 4 After being uniformly mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, 32 drops of N-methylpyrrolidone were added, and the corresponding nickel single atom-sulfur positive electrode material was obtained by electrode coating method.

[0149] Since the morphology and size of the nickel single atoms and ZIF-8 with coordination structures obtained in Examples 1 to 12 are basically the same, only the nickel single atoms and ZIF-8 with coordination structures obtained in some examples are tested below.

[0150] Figure 1 The NiN prepared in Example 9 of the present invention 3 S 1 TEM image of the coordination structure of a single nickel atom. Figure 2 The NiN prepared in Example 9 of the present invention 3 S 1 From the SEM image of the coordinated structure of nickel single atoms, it can be clearly seen that the ZIF-8 morphology remains intact and the size is about 70-80nm, which is conducive to providing a large number of active sites for the conversion of sulfur species and catalytic reactions. Figure 3 and Figure 4 The NiN prepared in Example 9 2 S 2 Transmission electron microscope and scanning electron microscope images of the coordination structure of single nickel atoms; Figure 5 and Figure 6 The NiN prepared in Example 9 1 S 3 From the transmission electron microscopy and scanning electron microscopy images of the coordinated structure of nickel single atoms, it can be found that as the temperature increases, the morphology of ZIF-8 gradually decomposes, resulting in a reduction in active sites and a decrease in electrochemical performance. Figure 7 The NiN prepared in Example 5 of the present invention x S y XRD schematic diagram of the coordinated structure of a single nickel atom. From the figure, it can be seen that there are no other peaks except the two carbon peaks, so it is judged that no other metal compounds or clusters appear. Figure 8 The figure is a rate performance diagram of the sulfur positive electrode material prepared in Example 1 of the present invention and Comparative Example 1. It can be seen that the positive electrode material after the coordination change has obvious advantages at high rates, especially the asymmetric coordinated NiN 1 S 3 -NSC and NiN 3 S 1 -NSC showed better performance.

[0151] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0152] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A nickel single atom having a coordination structure, characterized in that: Its general formula is NiN x S y , where 3≥x≥1, 3≥y≥1; x and y are both integers.

2. The nickel single atom having a coordination structure according to claim 1, characterized in that: Contains NiN3S1, NiN2S2 or NiN1S3.

3. A method for preparing a nickel single atom having a coordination structure according to claim 1, characterized in that: include: In an inert gas atmosphere, the Ni / ZIF-8 complex is dispersed in a solvent, mixed with a sulfur source, and then pyrolyzed at 900-1200°C for 1-4 hours to obtain nickel single atoms with a coordination structure.

4. The method for preparing a nickel single atom having a coordination structure according to claim 3, characterized in that: The ratio of the Ni / ZIF-8 complex to the sulfur source is 50-300 mg:10-100 μL.

5. The method for preparing a nickel single atom having a coordination structure according to claim 3, characterized in that: The sulfur source is any one of thiophene, carbon disulfide, thiophenol, sulfoxide, thioether and mercaptan.

6. The method for preparing a nickel single atom having a coordination structure according to claim 3, characterized in that: The heating rate during the pyrolysis is 5-7°C / min.

7. Use of the nickel single atom with a coordination structure as claimed in claim 1 in preparing a sulfur positive electrode material.

8. A sulfur cathode material, characterized in that: The invention comprises a sulfur positive electrode active material and the nickel single atom having a coordination structure as claimed in claim 1 supported on the sulfur positive electrode active material.

9. The method for preparing the sulfur positive electrode material according to claim 8, characterized in that: Include: The nickel single atom with a coordination structure and elemental sulfur are mixed, and then heated at 120 to 160° C. for 10 to 12 hours to obtain the sulfur positive electrode material; wherein the mass ratio of the nickel single atom with a coordination structure to the elemental sulfur is 1:

3.

10. A lithium-sulfur battery, characterized in that: Contains the sulfur positive electrode material according to claim 8.

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