Negative electrode active material and preparation method therefor, and negative electrode sheet and use thereof
By performing selenization and carbonization treatment on hollow materials to form metal selenide nanoparticles and coat them with a carbon layer, the volume effect problem of silicon-based and tin-based materials during charge and discharge processes is solved, thereby improving the capacity and cycle performance of secondary batteries.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NATIONAL INSTITUTE OF GUANGDONG ADVANCED ENERGY STORAGE CO LTD
- Filing Date
- 2024-12-11
- Publication Date
- 2026-05-21
Smart Images
Figure CN2024138441_21052026_PF_FP_ABST
Abstract
Description
Negative electrode active materials and their preparation methods, negative electrode sheets and their applications Technical Field
[0001] This application relates to the field of electrode materials technology, specifically to negative electrode active materials and their preparation methods, negative electrode sheets and their applications. Background Technology
[0002] Secondary batteries possess advantages such as high energy density, high output voltage, low self-discharge, and good cycle performance, and are widely used in power batteries and consumer electronics. In secondary batteries, the properties of the negative electrode active material play a crucial role in improving electrochemical performance.
[0003] Among negative electrode active materials, silicon-based and tin-based materials have been widely studied due to their high theoretical specific capacity. However, silicon-based and tin-based materials suffer from severe volume effects. During charge-discharge cycles, the volume expansion and contraction of electrode materials may lead to structural collapse. Negative electrode active materials are prone to breakage and pulverization, and it is difficult to form a stable SEI film on the surface, resulting in rapid capacity decay and poor cycle performance of the battery. Summary of the Invention
[0004] Based on this, this application provides a negative electrode active material and its preparation method, a negative electrode sheet and its application. The negative electrode active material prepared by the preparation method provided in this application can effectively mitigate the problems of volume change and structural collapse of electrode materials during charging and discharging, thereby effectively improving the capacity and cycle performance of secondary batteries; moreover, the preparation method of this application is simple and easy to realize industrial production.
[0005] A first aspect of this application provides a method for preparing a negative electrode active material, comprising the following steps:
[0006] A hollow material is selected, comprising iron-cobalt-nickel layered double hydroxide nanoparticles and a polydopamine material layer coating the surface of the iron-cobalt-nickel layered double hydroxide nanoparticles, wherein the iron-cobalt-nickel layered double hydroxide nanoparticles have a hollow structure.
[0007] The hollow material is subjected to selenization and carbonization treatment to transform the iron-cobalt-nickel layered double hydroxide nanoparticles into metal selenide nanoparticles and the polydopamine material layer into a carbon coating layer to prepare the negative electrode active material; wherein, the metal selenide nanoparticles include cobalt, nickel and iron ternary metal selenides.
[0008] In one embodiment, the specific steps of the selenization and carbonization treatment include: mixing the hollow material and selenium powder, and performing selenization and carbonization treatment at 300°C to 800°C in a mixed atmosphere of inert gas and reducing gas.
[0009] In one embodiment, the process parameters of the selenization and carbonization treatment have one or more of the following characteristics:
[0010] (1) The mass ratio of the hollow material and the selenium powder is 1:(1~1.5);
[0011] (2) The reducing gas is hydrogen;
[0012] (3) The selenization and carbonization treatment time is 2h to 6h.
[0013] In one embodiment, the preparation steps of the hollow material include:
[0014] The egg yolk shell structural material includes a core and an inner coating layer covering the core. The core is a metal-organic framework material, and there is a gap between the inner coating layer and the core. The inner coating layer includes a cobalt-nickel layered double hydroxide. The surface of the inner coating layer is also coated with a polydopamine material layer.
[0015] The hollow material is prepared by ion exchange and etching of the metal-organic framework material in the egg yolk shell structure material using a ferrous source, forming a hollow structure, and transforming the cobalt-nickel layered double hydroxide into an iron-cobalt-nickel layered double hydroxide.
[0016] In one embodiment, the etching process has one or more of the following features:
[0017] (1) The ferrous source includes ferrous chloride tetrahydrate;
[0018] (2) The mass ratio of the ferrous source to the egg yolk shell structural material is 1:(1.8~2.2);
[0019] (3) The specific steps of the etching process include: dispersing the egg yolk shell structure material and the ferrous source in an alcohol solvent, stirring for 2h to 3h, and then preparing the hollow material.
[0020] In one embodiment, the preparation steps of the egg yolk shell structural material include:
[0021] A precursor material is taken, the precursor material comprising a core and a polydopamine material layer coated on the core, wherein the core is a cobalt-containing metal-organic framework material;
[0022] The precursor material is mixed with a nickel source to form a cobalt-nickel layered double hydroxide with the cobalt element in the core. The cobalt-nickel layered double hydroxide is attached to the interior of the polydopamine material layer to form an inner coating layer. A gap is formed between the inner coating layer and the core to prepare the yolk shell structure material.
[0023] In one embodiment, the specific steps of mixing the precursor material with the nickel source include:
[0024] The precursor material is dispersed in a first solvent to prepare a first mixture;
[0025] The nickel source is dispersed in a second solvent to prepare a second mixture;
[0026] The first mixture is added to the first mixture, and after stirring for 2 to 3 hours, the egg yolk shell structure material is prepared.
[0027] In the first mixture, the mass concentration of the precursor material is 0.005 g / mL to 0.007 g / mL; in the second mixture, the mass concentration of the nickel source is 0.3 g / mL to 0.4 g / mL.
[0028] In one embodiment, the preparation steps of the precursor material include:
[0029] The cobalt-containing metal-organic framework material was prepared by mixing a cobalt source and an organic ligand in a solvent.
[0030] The cobalt-containing metal-organic framework material, dopamine hydrochloride, and an alkaline buffer are mixed to coat the surface of the cobalt-containing metal-organic framework material with polydopamine, thereby preparing the precursor material.
[0031] In one embodiment, the preparation step of the precursor material has one or more of the following features:
[0032] (1) The cobalt source includes cobalt nitrate hexahydrate;
[0033] (2) The organic ligands include dimethylimidazole;
[0034] (3) The mass ratio of the cobalt source and the organic ligand is (11-12):(13-14);
[0035] (4) The alkaline buffer includes tris(hydroxymethyl)aminomethane;
[0036] (5) The mass ratio of the cobalt-containing metal-organic framework material, dopamine hydrochloride and alkaline buffer is (0.25-0.35):(0.1-0.2):(0.1-0.15).
[0037] A second aspect of this application provides a negative electrode active material, which is prepared by the preparation method described in the first aspect of this application;
[0038] The negative electrode active material includes metal selenide nanoparticles and a carbon coating layer covering the surface of the metal selenide nanoparticles.
[0039] The metal selenide nanoparticles are hollow and include ternary metal selenides of cobalt, nickel, and iron.
[0040] In one embodiment, the particle size of the negative electrode active material is 200 nm to 400 nm.
[0041] A third aspect of this application provides a negative electrode sheet, comprising a negative current collector and a negative active material layer stacked on the surface of the negative current collector, wherein the negative active material layer comprises the negative active material described in any embodiment of the second aspect of this application.
[0042] In one embodiment, the negative electrode active material accounts for 70% to 85% of the negative electrode active material layer by weight percentage.
[0043] A fourth aspect of this application provides a secondary battery, including the negative electrode sheet described in any embodiment of the third aspect of this application.
[0044] In one embodiment, the secondary battery is a sodium-ion battery.
[0045] A fifth aspect of this application provides an electrical device including a secondary battery as described in any embodiment of the fourth aspect of this application.
[0046] This application has the following beneficial effects:
[0047] The preparation method provided in this application includes the steps of selecting hollow materials and performing selenization and carbonization treatment on the hollow materials. The resulting negative electrode active material includes hollow metal selenide nanoparticles. Their unique hollow structure effectively mitigates the problems of volume change and structural collapse of the electrode material during charging and discharging. Simultaneously, the multi-element metal selenides possess good conductivity and a stable crystal structure, which can improve charge transport performance. Furthermore, the carbon coating layer, which transforms the polydopamine material layer during the preparation process, not only improves conductivity but also increases the mechanical strength of the entire negative electrode active material, preventing breakage during battery cycling. At the same time, the carbon coating layer provides a physical barrier, reducing direct contact between the metal selenides and the electrolyte, improving electrolyte compatibility, and reducing the occurrence of side reactions.
[0048] In summary, the negative electrode active material prepared by the method provided in this application can effectively improve the capacity, cycle performance, and rate performance of secondary batteries. Furthermore, the preparation method of this application is simple and easy to implement for industrial production. Attached Figure Description
[0049] Figure 1 is a schematic diagram of the preparation process of the negative electrode active material provided in an example of this application;
[0050] Figure 2 is a schematic diagram of the structure of the negative electrode active material provided in this application;
[0051] Figure 3 is a TEM image of the hollow material prepared in Example 1 of this application;
[0052] Figure 4 is a TEM image of the negative electrode active material prepared in Example 1 of this application;
[0053] Figure 5 is the XRD pattern of the negative electrode active material prepared in Example 1 of this application;
[0054] Figure 6 shows the cycle performance test diagram of the negative electrode active material under different current densities in Example 1 and Comparative Examples 1 to 2 of this application.
[0055] Figure 7 shows the cycle performance test results of the negative electrode active materials in Example 1 and Comparative Examples 1 to 2 of this application at a current of 10 A / g.
[0056] In the figure, 10-hollow structure, 20-metal selenide nanoparticles, 30-carbon coating layer, 101-cobalt-containing metal-organic framework material, 102-interstitial space, 201-cobalt-nickel layered double hydroxide, 202-iron-cobalt-nickel layered double hydroxide nanoparticles, and 301-polydopamine material layer. Detailed Implementation
[0057] The following detailed description, in conjunction with specific embodiments, provides a more complete and clear account of the negative electrode active material, its preparation method, the negative electrode sheet, and its applications. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.
[0058] Transition metal selenium possesses advantages such as high theoretical specific capacity and strong chemical stability, making it a highly promising electrode material for secondary batteries. However, there are currently few preparation schemes for polymetallic selenides, mainly because the synthesis of pure-phase polymetallic selenides is quite difficult, and the synthesized materials are generally mono- and binary metal selenides. Mono- and binary selenides also have limited effectiveness in improving the performance of anode active materials. Furthermore, the preparation of hollow polymetallic selenide nanoparticles also faces problems such as failure to form, collapse of the hollow structure, or dissolution.
[0059] Based on this, the first aspect of this application provides a method for preparing a negative electrode active material, comprising the following steps:
[0060] S501. Take a hollow material, wherein the hollow material comprises iron-cobalt-nickel layered double hydroxide nanoparticles and a polydopamine material layer coating the surface of the iron-cobalt-nickel layered double hydroxide nanoparticles, wherein the iron-cobalt-nickel layered double hydroxide nanoparticles have a hollow structure.
[0061] S502. The hollow material is subjected to selenization and carbonization treatment to transform the iron-cobalt-nickel layered double hydroxide nanoparticles into metal selenide nanoparticles and the polydopamine material into a carbon coating layer to prepare the negative electrode active material; wherein, the metal selenide nanoparticles 20 include cobalt, nickel and iron ternary metal selenides.
[0062] After the hollow material undergoes selenization and carbonization treatment, the iron-cobalt-nickel layered double hydroxide is transformed into a metal selenide, wherein the metal selenide is a ternary metal selenide of cobalt, nickel, and iron; the polydopamine material is carbonized to form a carbon coating layer. Furthermore, in the preparation method provided in this application, selenization and carbonization are performed simultaneously, which is beneficial to improving preparation efficiency. Moreover, the method for preparing the negative electrode active material provided in this application results in multi-metal selenide hollow nanoparticles with a stable crystal structure, effectively avoiding the problems of hollow structure collapse and dissolution. This, in turn, can effectively improve the electrochemical performance of the prepared negative electrode active material.
[0063] Specifically, the selenization and carbonization treatment includes the following steps: mixing the hollow material and selenium powder, and performing selenization and carbonization treatment at 300℃ to 800℃ in a mixed atmosphere of inert gas and reducing gas. Specifically, the temperature for selenization and carbonization treatment includes, but is not limited to, 300℃, 340℃, 350℃, 360℃, 380℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃.
[0064] To ensure sufficient selenium source participation in the reaction and achieve effective conversion of iron-cobalt-nickel layered double hydroxides into metal selenides, in one example, the process parameters for the selenization and carbonization treatment include: a mass ratio of the hollow material to the selenium powder of 1:(1-1.5). Specifically, the mass ratio of the hollow material to the selenium powder includes, but is not limited to, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5.
[0065] In one example, the process parameters for the selenization and carbonization treatment include: the reducing gas is hydrogen. Performing the selenization and carbonization treatment in a mixed atmosphere of inert and reducing gases can effectively avoid the possibility of metal oxidation, thereby promoting the formation of metal selenides and improving their purity.
[0066] In one example, the volume ratio of the inert gas to the reducing gas is (8.5–9.5):1. Specifically, the volume ratio of the inert gas to the reducing gas includes, but is not limited to, 8.5:1, 8.6:1, 8.7:1, 8.8:1, 8.9:1, 9:1, 9.1:1, 9.2:1, 9.3:1, 9.4:1, or 9.5:1.
[0067] In one example, the process parameters for the selenization carbonization treatment include: the selenization carbonization treatment time is 2h to 6h. Specifically, the selenization treatment time includes, but is not limited to, 2h, 3h, 4h, 5h, or 6h.
[0068] In one specific example, the method for preparing the negative electrode active material includes the following steps:
[0069] S50. The hollow material and selenium powder are mixed at a mass ratio of 1:(1~1.5), and the mixture is subjected to selenization and carbonization treatment at 300℃~800℃ for 2h~6h in a mixed atmosphere of inert gas and reducing gas to prepare the negative electrode active material.
[0070] In one example, the preparation steps of the hollow material include:
[0071] S401. Take an egg yolk shell structural material, the egg yolk shell structural material including a core body and an inner coating layer covering the core body, the core body being a metal-organic framework material, a gap being left between the inner coating layer and the core body, the inner coating layer including a cobalt-nickel layered double hydroxide; the surface of the inner coating layer is also coated with a polydopamine material layer;
[0072] S402. The metal-organic framework material in the egg yolk shell structure material is subjected to ion exchange and etching treatment using a ferrous source to form a hollow structure, and the cobalt-nickel layered double hydroxide is transformed into iron-cobalt-nickel layered double hydroxide to prepare the hollow material.
[0073] This application discovered that Fe in ferriferrous sources 2+ It can undergo ion exchange with metal ions in metal-organic framework materials to effectively etch the core and form hollow materials. Meanwhile, Fe... 2+ It will also react with cobalt-nickel layered double hydroxides to produce iron-cobalt-nickel layered double hydroxides. If Fe... 2+ Replace with Fe 3+ When ferric nitrate nonahydrate is used as the iron source, the metal-organic framework material will be completely hydrolyzed, causing the solution to change from a suspension to a clear and transparent solution without the formation of solid particles. This is therefore unfavorable for the formation of hollow materials. Furthermore, Fe... 2+ Replace with Mn 2+ Cu2+ Plasma etching, which uses manganese chloride tetrahydrate and copper chloride dihydrate for etching, has the disadvantage of insufficient etching and inability to form a hollow structure.
[0074] In one example, the ferrous source comprises ferrous chloride tetrahydrate.
[0075] To ensure effective etching of the yolk-shell structure material by the ferrous source and to achieve effective conversion of cobalt-nickel layered double hydroxides to iron-cobalt-nickel layered double hydroxides, in one example, the process parameters for ion exchange and etching include a mass ratio of the ferrous source to the yolk-shell structure material of 1:(1.8–2.2). Specifically, the mass ratio of the ferrous source to the yolk-shell structure material includes, but is not limited to, 1:1.8, 1:1.9, 1:2, 1:2.1, or 1:2.2.
[0076] In one example, the specific steps for ion exchange and etching include: dispersing the egg yolk shell structure material and the ferrous source in an alcohol solvent, stirring for 2 to 3 hours, and then preparing the hollow material.
[0077] In one example, after the step of preparing the hollow material, the steps of filtration, washing, and drying are also included.
[0078] In one specific example, the method for preparing the hollow material includes the following steps:
[0079] S40. The egg yolk shell structural material and the ferrous source are dispersed in an alcohol solvent at a mass ratio of 1:(1.8~2.2), and stirred for 2h~3h. The metal-organic framework material in the egg yolk shell structural material is etched by the ferrous source to reduce the core and form a hollow structure, and the cobalt-nickel layered double hydroxide is transformed into iron-cobalt-nickel layered double hydroxide to prepare the hollow material.
[0080] In one example, the preparation steps of the yolk shell structural material include:
[0081] S301. Take a precursor material, the precursor material including a core and a polydopamine material layer coated on the core, the core being a cobalt-containing metal-organic framework material;
[0082] S302. The precursor material is mixed with a nickel source to form a cobalt-nickel layered double hydroxide with the cobalt element in the core. The cobalt-nickel layered double hydroxide is attached to the interior of the polydopamine material layer to form an inner coating layer. A gap is formed between the inner coating layer and the core to prepare the yolk shell structure material.
[0083] In one example, the specific steps of mixing the precursor material with the nickel source include:
[0084] The precursor material is dispersed in a first solvent to prepare a first mixture;
[0085] The nickel source is dispersed in a second solvent to prepare a second mixture;
[0086] The first mixture is added to the first mixture, and after stirring for 2 to 3 hours, the egg yolk shell structure material is prepared.
[0087] In the first mixture, the mass concentration of the precursor material is 0.005 g / mL to 0.007 g / mL; in the second mixture, the mass concentration of the nickel source is 0.0065 g / mL to 0.0075 g / mL.
[0088] In the first mixture, the mass concentration of the precursor material includes, but is not limited to, 0.005 g / mL, 0.0055 g / mL, 0.0058 g / mL, 0.006 g / mL, 0.0062 g / mL, 0.0065 g / mL, 0.0068 g / mL, and 0.007 g / mL. In the second mixture, the mass concentration of the nickel source includes, but is not limited to, 0.0065 g / mL, 0.0068 g / mL, 0.007 g / mL, 0.0072 g / mL, or 0.0075 g / mL.
[0089] In one example, the nickel source comprises nickel nitrate hexahydrate.
[0090] Specifically, the first solvent and the second solvent are each independently selected from alcohol solvents. For example, the alcohol solvents include, but are not limited to, methanol, ethanol, isopropanol, and n-propanol.
[0091] In one specific example, the method for preparing the egg yolk shell structural material includes the following steps:
[0092] Step S30: Disperse the precursor material in a first solvent to prepare a first mixture, wherein the mass concentration of the precursor material in the first mixture is 0.005 g / mL to 0.007 g / mL; disperse the nickel source in a second solvent to prepare a second mixture, wherein the mass concentration of the nickel source in the second mixture is 0.0065 g / mL to 0.0075 g / mL; add the first mixture to the first mixture, stir for 2 h to 3 h, and then prepare the egg yolk shell structure material.
[0093] In one example, the preparation steps of the precursor material include:
[0094] S10. Mix the cobalt source and organic ligand in a solvent to prepare the cobalt-containing metal-organic framework material;
[0095] S20. The cobalt-containing metal-organic framework material, dopamine hydrochloride, and alkaline buffer are mixed to coat the surface of the cobalt-containing metal-organic framework material with polydopamine, thereby preparing the precursor material.
[0096] Cobalt-containing metal-organic framework materials were prepared using cobalt source and organic ligands. These metal-organic framework materials have an ordered pore structure and high specific surface area and porosity, thus providing a good foundation for subsequent etching processes and promoting the formation of hollow structures.
[0097] In one example, the cobalt source includes cobalt nitrate hexahydrate.
[0098] In one example, the organic ligand includes dimethylimidazole.
[0099] In one example, the mass ratio of the cobalt source to the organic ligand is (11-12):(13-14). Specifically, the mass ratio of the cobalt source to the organic ligand includes, but is not limited to, 11:13, 11.5:13.1, 11.6:13.1, 11.64:13.1, 11.64:13.14, 11.65:13.14, 12:13.14, 12:13.5, 12:13.8, or 12:14.
[0100] In one specific example, the preparation steps of the cobalt-containing metal-organic framework material include:
[0101] S101. Mix cobalt source in a first organic solvent to prepare a first solution; mix organic ligand in a second organic solvent to prepare a second solution; add the first solution to the second solution and stir for 10h to 14h to prepare the cobalt-containing metal-organic framework material.
[0102] Specifically, the first organic solvent and the second organic solvent are each independently selected from alcohol solvents. For example, the alcohol solvent includes, but is not limited to, methanol, ethanol, isopropanol, and n-propanol.
[0103] In one example, the alkaline buffer comprises tris(hydroxymethyl)aminomethane. Tris(hydroxymethyl)aminomethane effectively maintains pH, allowing dopamine hydrochloride to undergo self-polymerization in an alkaline environment to form a polydopamine coating.
[0104] In one example, the mass ratio of the cobalt-containing metal-organic framework material, dopamine hydrochloride, and alkaline buffer is (0.25–0.35):(0.1–0.2):(0.1–0.15). Specifically, the mass ratio of the cobalt-containing metal-organic framework material, dopamine hydrochloride, and alkaline buffer includes, but is not limited to, 0.25:0.1:0.1, 0.3:0.1:0.1, 0.3:0.15:0.1, 0.3:0.15:0.12, 0.3:0.15:0.121, 0.3:0.2:0.15, 0.35:0.1:0.1, 0.35:0.15:0.15, or 0.35:0.2:0.15.
[0105] In one specific example, the method for preparing the cobalt-containing metal-organic framework material includes the following steps:
[0106] S201. The cobalt-containing metal-organic framework material, dopamine hydrochloride, and alkaline buffer are mixed in a mixed solvent to coat the surface of the cobalt-containing metal-organic framework material with polydopamine, thereby preparing the precursor material.
[0107] The mixed solvent comprises an alcohol solvent and water. The volume ratio of the alcohol solvent to water is (0.8–1.2):1. For example, the alcohol solvent includes, but is not limited to, methanol, ethanol, isopropanol, and n-propanol.
[0108] Referring to Figure 1, specifically, the preparation method of the negative electrode active material includes the following steps:
[0109] a. Mix cobalt source in a first organic solvent to prepare a first solution; mix organic ligand in a second organic solvent to prepare a second solution; add the first solution to the second solution and stir for 10h to 14h to prepare the cobalt-containing metal-organic framework material 101.
[0110] b. Mix the cobalt-containing metal-organic framework material 101, dopamine hydrochloride, and an alkaline buffer in a mixed solvent to coat the surface of the cobalt-containing metal-organic framework material with polydopamine material, thereby preparing the precursor material.
[0111] c. Disperse the precursor material in a first solvent to prepare a first mixture, wherein the mass concentration of the precursor material in the first mixture is 0.005 g / mL to 0.007 g / mL; disperse the nickel source in a second solvent to prepare a second mixture, wherein the mass concentration of the nickel source in the second mixture is 0.0065 g / mL to 0.0075 g / mL; add the first mixture to the first mixture and stir for 2 to 3 hours to allow the nickel source to form a cobalt-nickel layered double hydroxide 201 with the cobalt element in the core body through the polydopamine material layer 301. The cobalt-nickel layered double hydroxide 201 is attached to the interior of the polydopamine material layer 301 to form an inner coating layer. A gap 102 is formed between the inner coating layer and the core body to prepare the yolk shell structure material.
[0112] d. The egg yolk shell structural material and the ferrous source are dispersed in an alcohol solvent at a mass ratio of 1:(1.8-2.2) and stirred for 2-3 hours. The metal-organic framework material in the egg yolk shell structural material is etched by the ferrous source to reduce the core and form a hollow structure 10. The cobalt-nickel layered double hydroxide 201 is transformed into iron-cobalt-nickel layered double hydroxide to prepare the hollow material. At this time, the hollow material includes iron-cobalt-nickel layered double hydroxide nanoparticles 202. The iron-cobalt-nickel layered double hydroxide nanoparticles 202 are hollow and the surface of the iron-cobalt-nickel layered double hydroxide nanoparticles 202 is coated with a polydopamine material layer 301.
[0113] e. The hollow material and selenium powder are mixed at a mass ratio of 1:(1 to 1.5), and the mixture is subjected to selenization and carbonization treatment at 300°C to 800°C for 2 to 6 hours in a mixed atmosphere of inert gas and reducing gas to prepare the negative electrode active material.
[0114] In this application, the mechanism for preparing the negative electrode active material is as follows: First, a cobalt-containing metal-organic framework (MOF) material is prepared using a cobalt source and organic ligands. Using this material as a template, when dopamine hydrochloride is added, the dopamine hydrochloride polymerizes and coats the surface of the MOF material, thus preparing a precursor material. Since the polydopamine layer has a porous structure, after the addition of a nickel source, the nickel source passes through the pores into the polydopamine material layer. Furthermore, the nickel source can also react with the cobalt element in the MOF material to form a cobalt-nickel layered double hydroxide. This process occurs on the inner surface of the polydopamine material layer; that is, the presence of the polydopamine material layer provides a growth site for the formation of the cobalt-nickel layered double hydroxide. In addition, since the partial dissolution of the MOF material is necessary to release cobalt ions to form the cobalt-nickel layered double hydroxide, a gap is formed between the MOF material core and the cobalt-nickel layered double hydroxide layer. The addition of a ferrihydride source can etch the remaining MOF material core to form a hollow structure and transform the cobalt-nickel layered double hydroxide into an iron-cobalt-nickel layered double hydroxide, thus preparing a hollow material. This hollow material comprises iron-cobalt-nickel layered double hydroxide hollow nanoparticles and a polydopamine material layer coated on the surface of the iron-cobalt-nickel layered double hydroxide hollow nanoparticles. Further selenization and carbonization treatments on the hollow material transform the iron-cobalt-nickel layered double hydroxide into a ternary metal selenide and the polydopamine material layer into a carbon coating layer.
[0115] Referring to Figure 2, a second aspect of this application provides a negative electrode active material, the negative electrode active material comprising metal selenide nanoparticles 20 and a carbon coating layer 30 covering the surface of the metal selenide nanoparticles 20; wherein the metal selenide nanoparticles 20 are hollow structures, and the metal selenide nanoparticles comprise cobalt, nickel, and iron ternary metal selenides.
[0116] The negative electrode active material provided in this application includes hollow metal selenide nanoparticles. Their unique hollow structure effectively mitigates volume changes and structural collapse of the electrode material during charging and discharging. Simultaneously, the multi-element metal selenides possess excellent conductivity and a stable crystal structure, which improves charge transport performance. Furthermore, a carbon coating layer is applied to the surface of the metal selenide nanoparticles. This carbon coating layer not only enhances conductivity but also increases the mechanical strength of the entire negative electrode active material, preventing breakage during battery cycling. Simultaneously, the carbon coating layer provides a physical barrier, reducing direct contact between the metal selenides and the electrolyte, improving electrolyte compatibility, and reducing side reactions. In summary, the negative electrode active material provided in this application can effectively improve the capacity, cycle performance, and rate performance of secondary batteries.
[0117] In one example, the particle size of the negative electrode active material is 200 nm to 400 nm. It is understood that the particle size of the negative electrode active material can be selected from any value between 200 nm and 400 nm. Specifically, the particle size of the negative electrode active material includes, but is not limited to, 200 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, 350 nm, 370 nm, 390 nm, or 400 nm. A third aspect of this application provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode active material layer stacked on the surface of the negative electrode current collector, wherein the negative electrode active material layer comprises the negative electrode active material described in any example of the second aspect of this application.
[0118] In one example, the negative electrode active material comprises 70% to 85% of the negative electrode active material layer by weight. Specifically, the proportion of the negative electrode active material includes, but is not limited to, 67.5%, 70%, 72%, 75%, 78%, 80%, 82%, 83%, or 85%.
[0119] In one more specific example, the negative electrode active material layer comprises, by weight percentage: 70% to 85% negative electrode active material, 7.5% to 15% binder, and 7.5% to 15% conductive agent.
[0120] For example, the conductive agent includes, but is not limited to, conductive carbon black. The binder includes, but is not limited to, sodium alginate. By proportioning the components in the negative electrode active material layer, good adhesion between the active material and the current collector can be ensured, while maintaining structural stability. Specifically, the mass percentage of the negative electrode active material includes, but is not limited to, 67.5%, 70%, 72%, 75%, 78%, 80%, 82%, 83%, or 85%. The mass percentage of the binder includes, but is not limited to, 7.5%, 8%, 9%, 10%, 11%, 12%, or 15%. The mass percentage of the conductive agent includes, but is not limited to, 7.5%, 8%, 9%, 10%, 11%, 12%, or 15%.
[0121] A fourth aspect of this application provides a secondary battery including the negative electrode sheet described in any example of the third aspect of this application.
[0122] In one example, the secondary battery is a sodium-ion battery.
[0123] Lithium-ion batteries (LIBs) are widely used as energy storage devices due to their long lifespan and environmental friendliness. However, current LIBs face several challenges, such as limited capacity and uneven distribution of lithium resources. In contrast, sodium-ion batteries (SIBs) are considered an ideal alternative to LIBs due to abundant sodium resources and a similar ion storage mechanism. However, sodium ions have a relatively large radius... This leads to phenomena such as volume expansion and contraction of electrode materials during sodium insertion and removal during charging and discharging. This can cause structural collapse and rapid degradation of battery performance, thus limiting the commercial development of SIBs.
[0124] Transition metal selenium (TMSe) possesses advantages such as high theoretical specific capacity and strong chemical stability, making it a highly promising electrode material for secondary batteries. The negative electrode active material provided in this application contains multi-metal selenides in its inner coating layer, exhibiting excellent conductivity and a stable crystal structure, thus improving charge transport performance. Furthermore, its unique hollow structure effectively mitigates volume changes and structural collapse during sodium insertion and removal in SIBs during charging and discharging. Further, the surface of the metal selenide nanoparticles is coated with a carbon coating layer. This carbon coating not only enhances conductivity but also increases the mechanical strength of the entire negative electrode active material, preventing breakage during battery cycling. Simultaneously, the carbon coating layer provides a physical barrier, reducing direct contact between the metal selenides and the electrolyte, improving electrolyte compatibility, and reducing side reactions. Therefore, the negative electrode active material provided in this application, when used as a negative electrode active material for SIBs, can effectively prevent excessive volume expansion during sodium insertion and removal, thereby effectively improving the capacity and cycle performance of SIBs.
[0125] A fifth aspect of this application provides an electrical device including a secondary battery as described in any example of the fourth aspect of this application.
[0126] The following specific embodiments illustrate this application in detail. It should also be understood that the following embodiments are only for further explanation of this application and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values in the embodiments below.
[0127] Example 1
[0128] (1) Preparation of MOF materials:
[0129] 11.64 g of cobalt nitrate hexahydrate was mixed in 500 mL of methanol to prepare a purple-pink first solution; 13.14 g of dimethylimidazole was mixed in 500 mL of methanol to prepare a transparent second solution; the purple-pink first solution was added to the transparent second solution, stirred for 12 h, allowed to stand for 12 h, centrifuged, washed, and dried in a 60℃ forced-air drying oven for 24 h to prepare MOF material.
[0130] (2) Preparation of precursor materials:
[0131] 0.3 g of MOF material, 0.15 g of dopamine hydrochloride and 0.121 g of tris(hydroxymethyl)aminomethane (alkaline buffer) were mixed in 100 mL of mixed solvent (ethanol and water volume ratio of 1:1) to coat the surface of the cobalt-containing metal-organic framework material with polydopamine, thus preparing a black-gray precursor material.
[0132] (3) Preparation of egg yolk shell structural materials:
[0133] 0.3 g of precursor material was dispersed in 50 mL of ethanol to prepare a first mixture, wherein the mass concentration of the precursor material in the first mixture was 0.006 g / mL; nickel nitrate hexahydrate was dispersed in 50 mL of ethanol to prepare a second mixture, wherein the mass concentration of nickel nitrate hexahydrate in the second mixture was 0.0068 g / mL; the first mixture was added to the first mixture, and after stirring for 2 h, the nickel source formed a cobalt-nickel layered double hydroxide with the cobalt element in the core body through the polydopamine material layer. The cobalt-nickel layered double hydroxide adhered to the interior of the polydopamine material layer to form an inner coating layer, and a gap was formed between the inner coating layer and the core body. After filtration and washing, the mixture was placed in a 60°C forced-air drying oven and dried for 24 h to prepare the egg yolk shell structure material.
[0134] (4) Preparation of hollow materials:
[0135] 0.2g of egg yolk shell structural material and 0.4g of ferrous chloride tetrahydrate were dispersed in 50mL of ethanol and stirred for 2-3 hours. The metal-organic framework material in the egg yolk shell structural material was subjected to ion exchange and etching treatment by ferrous source to reduce the core and form a hollow structure. The cobalt-nickel layered double hydroxide was transformed into iron-cobalt-nickel layered double hydroxide. After filtration and washing, it was placed in a 60℃ forced-air drying oven for 24 hours to prepare hollow material. The TEM image of the hollow material is shown in Figure 3. At this time, the hollow material includes iron-cobalt-nickel layered double hydroxide hollow nanoparticles and a polydopamine material layer coated on the surface of the iron-cobalt-nickel layered double hydroxide hollow nanoparticles.
[0136] (5) Preparation of negative electrode active materials:
[0137] Hollow materials and selenium powder were ground uniformly in a mortar at a 1:1 mass ratio. Then, under a mixed atmosphere of Ar / H2 gas flow (Ar / H2 volume ratio of 9:1), a selenization and carbonization treatment was performed at 500℃ for 3 hours to prepare the negative electrode active material. The negative electrode active material comprises hollow metal selenide nanoparticles, including cobalt, nickel, and iron ternary metal selenides; and the surface of the metal selenide nanoparticles is coated with a carbon coating layer. A TEM image of the negative electrode active material is shown in Figure 4; an XRD pattern of the negative electrode active material is shown in Figure 5.
[0138] Comparative Example 1
[0139] Comparative Example 1 is basically the same as Example 1, the main difference being that Comparative Example 1 does not include the step of treating with ferrous chloride tetrahydrate. The specific steps are as follows:
[0140] (1) Preparation of MOF materials:
[0141] 11.64 g of cobalt nitrate hexahydrate was mixed in 500 mL of methanol to prepare a purple-pink first solution; 13.14 g of dimethylimidazole was mixed in 500 mL of methanol to prepare a transparent second solution; the purple-pink first solution was added to the transparent second solution, stirred for 12 h, allowed to stand for 12 h, centrifuged, washed, and dried in a 60℃ forced-air drying oven for 24 h to prepare MOF material.
[0142] (2) Preparation of precursor materials:
[0143] 0.3 g of MOF material, 0.15 g of dopamine hydrochloride and 0.121 g of tris(hydroxymethyl)aminomethane (alkaline buffer) were mixed in 100 mL of mixed solvent (ethanol and water volume ratio of 1:1) to coat the surface of the cobalt-containing metal-organic framework material with polydopamine, thus preparing a black-gray precursor material.
[0144] (3) Preparation of egg yolk shell structural materials:
[0145] 0.3 g of precursor material was dispersed in 50 mL of ethanol to prepare a first mixture, wherein the mass concentration of the precursor material in the first mixture was 0.006 g / mL; nickel nitrate hexahydrate was dispersed in 50 mL of ethanol to prepare a second mixture, wherein the mass concentration of nickel nitrate hexahydrate in the second mixture was 0.0068 g / mL; the first mixture was added to the first mixture, and after stirring for 2 h, the nickel source formed a cobalt-nickel layered double hydroxide with the cobalt element in the core body through the polydopamine material layer. The cobalt-nickel layered double hydroxide adhered to the interior of the polydopamine material layer to form an inner coating layer, and a gap was formed between the inner coating layer and the core body. After filtration and washing, the mixture was placed in a 60°C forced-air drying oven and dried for 24 h to prepare the egg yolk shell structure material.
[0146] (4) Preparation of cobalt-nickel selenide anode active material:
[0147] Egg yolk shell structural material and selenium powder were ground evenly in a mortar at a mass ratio of 1:1. Then, under a mixed atmosphere of Ar / H2 gas flow (Ar / H2 volume ratio of 9:1), the cobalt-nickel selenide anode active material was prepared by selenization and carbonization treatment at 500℃ for 3 hours.
[0148] Comparative Example 2
[0149] Comparative Example 2 is basically the same as Example 1, the main difference being that Comparative Example 2 does not include the steps of treating nickel nitrate hexahydrate and ferrous chloride tetrahydrate. The specific steps are as follows:
[0150] (1) Preparation of MOF materials:
[0151] 11.64 g of cobalt nitrate hexahydrate was mixed in 500 mL of methanol to prepare a purple-pink first solution; 13.14 g of dimethylimidazole was mixed in 500 mL of methanol to prepare a transparent second solution; the purple-pink first solution was added to the transparent second solution, stirred for 12 h, allowed to stand for 12 h, centrifuged, washed, and dried in a 60℃ forced-air drying oven for 24 h to prepare MOF material.
[0152] (2) Preparation of precursor materials:
[0153] 0.3 g of MOF material, 0.15 g of dopamine hydrochloride and 0.121 g of tris(hydroxymethyl)aminomethane (alkaline buffer) were mixed in 100 mL of mixed solvent (ethanol and water volume ratio of 1:1) to coat the surface of the cobalt-containing metal-organic framework material with polydopamine, thus preparing a black-gray precursor material.
[0154] (3) Preparation of cobalt selenide anode active material:
[0155] The black-gray precursor material and selenium powder were ground evenly in a mortar at a mass ratio of 1:1. Then, under a mixed atmosphere of Ar / H2 gas flow (Ar / H2 volume ratio of 9:1), the cobalt selenide anode active material was prepared by selenization and carbonization treatment at 500℃ for 3 hours.
[0156] Comparative Example 3
[0157] (1) Preparation of MOF materials:
[0158] 11.64 g of cobalt nitrate hexahydrate was mixed in 500 mL of methanol to prepare a purple-pink first solution; 13.14 g of dimethylimidazole was mixed in 500 mL of methanol to prepare a transparent second solution; the purple-pink first solution was added to the transparent second solution, stirred for 12 h, allowed to stand for 12 h, centrifuged, washed, and dried in a 60℃ forced-air drying oven for 24 h to prepare MOF material.
[0159] (2) Preparation of egg yolk shell structural materials:
[0160] 0.3 g of MOF material was dispersed in 50 mL of ethanol to prepare a first mixture, wherein the mass concentration of the precursor material in the first mixture was 0.006 g / mL; nickel nitrate hexahydrate was dispersed in 50 mL of ethanol to prepare a second mixture, wherein the mass concentration of nickel nitrate hexahydrate in the second mixture was 0.0068 g / mL; the first mixture was added to the first mixture, stirred for 2 h, filtered, washed, and then dried in a forced-air drying oven at 60 °C for 24 h to prepare the egg yolk shell structure material.
[0161] (3) Preparation of hollow materials:
[0162] 0.2g of egg yolk shell structural material and 0.4g of ferrous chloride tetrahydrate were dispersed in 50mL of ethanol and stirred for 2-3 hours. The metal-organic framework material in the egg yolk shell structural material was etched by the ferrous source to reduce the core and form a hollow structure. The cobalt-nickel layered double hydroxide was transformed into iron-cobalt-nickel layered double hydroxide. After filtration and washing, the material was dried in a 60℃ forced-air drying oven for 24 hours to prepare the hollow material.
[0163] (4) Preparation of negative electrode active materials:
[0164] Hollow core material and selenium powder were ground uniformly in a mortar at a 1:1 mass ratio. Then, under a mixed atmosphere of Ar / H2 gas flow (Ar / H2 volume ratio of 9:1), a selenization treatment was performed at 500℃ for 3 hours to prepare the negative electrode active material. Because dopamine hydrochloride was not added during the preparation process of Comparative Example 3, the polydopamine layer could not be formed, and therefore the negative electrode active material did not include a carbon coating layer. Testing showed that the negative electrode active material was non-conductive, resulting in poor battery performance.
[0165] Test case
[0166] The negative electrode active material, conductive carbon black, and sodium alginate prepared in the examples and comparative examples were mixed at a mass ratio of 8:1:1, and deionized water was added to grind them into a slurry. The slurry was coated onto copper foil, and a CR2032 sodium-ion battery was assembled in a glove box. The cycle performance of the sodium-ion battery was tested using a Blue Electric system. The cycle performance test graphs at different current densities are shown in Figure 6, and the cycle performance test graph at a current of 10 A / g is shown in Figure 7.
[0167] As shown in Figures 3 and 4, both the hollow material and the negative electrode active material prepared in Example 1 of this application have hollow structures, with a particle size of approximately 200 nm to 400 nm. The XRD pattern in Figure 5 shows that the negative electrode active material prepared in Example 1 has a pure-phase metal selenide crystal structure.
[0168] In Comparative Example 1, the step of treating with ferrous chloride tetrahydrate was omitted, resulting in a selenide that was not hollow and did not contain iron selenide. In Comparative Example 2, the steps of treating with nickel nitrate hexahydrate and ferrous chloride tetrahydrate were omitted, resulting in a selenide that was not hollow and did not contain nickel selenide or iron selenide. As shown in Figure 6, the negative electrode active material of Example 1 exhibited the best rate performance at different current densities. As shown in Figure 7, Example 1 showed the highest specific capacity and coulombic efficiency at a current of 10 A / g, indicating that the negative electrode active material of Example 1 had good cycle stability. These results demonstrate that the negative electrode active material provided in this application, comprising hollow metal selenide nanoparticles and a carbon coating layer, and wherein the metal selenides include cobalt selenide, nickel selenide, and iron selenide, can effectively improve conductivity and alleviate the volume expansion problem during cycling. Furthermore, the multi-metal selenide is Na... + It provides more active sites, thereby accelerating Na + Reaction kinetics of migration.
[0169] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0170] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.
Claims
1. A method for preparing a negative electrode active material, characterized in that, Includes the following steps: A hollow material is selected, comprising iron-cobalt-nickel layered double hydroxide nanoparticles and a polydopamine material layer coating the surface of the iron-cobalt-nickel layered double hydroxide nanoparticles, wherein the iron-cobalt-nickel layered double hydroxide nanoparticles have a hollow structure. The hollow material is subjected to selenization and carbonization treatment to transform the iron-cobalt-nickel layered double hydroxide nanoparticles into metal selenide nanoparticles and the polydopamine material layer into a carbon coating layer to prepare the negative electrode active material; wherein, the metal selenide nanoparticles include cobalt, nickel and iron ternary metal selenides.
2. The method for preparing the negative electrode active material according to claim 1, characterized in that, The specific steps of the selenization and carbonization treatment include: mixing the hollow material and selenium powder, and carrying out selenization and carbonization treatment at 300℃~800℃ in a mixed atmosphere of inert gas and reducing gas.
3. The method for preparing the negative electrode active material according to claim 2, characterized in that, The process parameters for the selenization and carbonization treatment have one or more of the following characteristics: (1) The mass ratio of the hollow material and the selenium powder is 1:(1~1.5); (2) The reducing gas is hydrogen; (3) The selenization and carbonization treatment time is 2h to 6h.
4. The method for preparing the negative electrode active material according to any one of claims 1 to 3, characterized in that, The preparation steps of the hollow material include: The egg yolk shell structural material includes a core and an inner coating layer covering the core. The core is a metal-organic framework material, and there is a gap between the inner coating layer and the core. The inner coating layer includes a cobalt-nickel layered double hydroxide. The surface of the inner coating layer is also coated with a polydopamine material layer. The hollow material is prepared by ion exchange and etching of the metal-organic framework material in the egg yolk shell structure material using a ferrous source, forming a hollow structure, and transforming the cobalt-nickel layered double hydroxide into an iron-cobalt-nickel layered double hydroxide.
5. The method for preparing the negative electrode active material according to claim 4, characterized in that, The etching process has one or more of the following characteristics: (1) The ferrous source includes ferrous chloride tetrahydrate; (2) The mass ratio of the ferrous source to the egg yolk shell structural material is 1:(1.8~2.2); (3) The specific steps of the etching process include: dispersing the egg yolk shell structure material and the ferrous source in an alcohol solvent, stirring for 2h to 3h, and then preparing the hollow material.
6. The method for preparing the negative electrode active material according to claim 4, characterized in that, The preparation steps of the egg yolk shell structural material include: A precursor material is taken, the precursor material comprising a core and a polydopamine material layer coated on the core, wherein the core is a cobalt-containing metal-organic framework material; The precursor material is mixed with a nickel source to form a cobalt-nickel layered double hydroxide with the cobalt element in the core. The cobalt-nickel layered double hydroxide is attached to the interior of the polydopamine material layer to form an inner coating layer. A gap is formed between the inner coating layer and the core to prepare the yolk shell structure material.
7. The method for preparing the negative electrode active material according to claim 6, characterized in that, The specific steps for mixing the precursor material with the nickel source include: The precursor material is dispersed in a first solvent to prepare a first mixture; The nickel source is dispersed in a second solvent to prepare a second mixture; The first mixture is added to the first mixture, and after stirring for 2 to 3 hours, the egg yolk shell structure material is prepared. In the first mixture, the mass concentration of the precursor material is 0.005 g / mL to 0.007 g / mL; in the second mixture, the mass concentration of the nickel source is 0.3 g / mL to 0.4 g / mL.
8. The method for preparing the negative electrode active material according to claim 6 or 7, characterized in that, The preparation steps of the precursor material include: The cobalt-containing metal-organic framework material was prepared by mixing a cobalt source and an organic ligand in a solvent. The cobalt-containing metal-organic framework material, dopamine hydrochloride, and an alkaline buffer are mixed to coat the surface of the cobalt-containing metal-organic framework material with polydopamine, thereby preparing the precursor material.
9. The method for preparing the negative electrode active material according to claim 8, characterized in that, The preparation steps of the precursor material have one or more of the following characteristics: (1) The cobalt source includes cobalt nitrate hexahydrate; (2) The organic ligands include dimethylimidazole; (3) The mass ratio of the cobalt source and the organic ligand is (11-12):(13-14); (4) The alkaline buffer includes tris(hydroxymethyl)aminomethane; (5) The mass ratio of the cobalt-containing metal-organic framework material, dopamine hydrochloride and alkaline buffer is (0.25-0.35):(0.1-0.2):(0.1-0.15).
10. A negative electrode active material, characterized in that, The anode active material is prepared by the preparation method according to any one of claims 1 to 9; the anode active material includes metal selenide nanoparticles and a carbon coating layer covering the surface of the metal selenide nanoparticles. The metal selenide nanoparticles are hollow and include ternary metal selenides of cobalt, nickel, and iron.
11. The negative electrode active material according to claim 10, characterized in that, The particle size of the negative electrode active material is 200 nm to 400 nm.
12. A negative electrode sheet, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer stacked on the surface of the negative electrode current collector, wherein the negative electrode active material layer includes the negative electrode active material as described in claim 10 or 11.
13. The negative electrode sheet according to claim 12, characterized in that, The negative electrode active material accounts for 70% to 85% of the negative electrode active material layer by weight percentage.
14. A secondary battery, characterized in that, Includes the negative electrode sheet as described in claim 12 or 13.
15. The secondary battery according to claim 14, characterized in that, The secondary battery is a sodium-ion battery.
16. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 14 or 15.