One-step dealloying preparation method of a highly stable antimony-based composite electrode material

Abstract

The present invention relates to a one-step dealloying preparation method of a highly stable antimony-based composite electrode material. First, a Mg-rich Mg-Cu-Sb ternary alloy is prepared, and then a Cu₂Sb / Sb₂O₃ composite electrode material with high cycle stability is obtained in one step by a simple chemical etching method. Cu₂Sb has a nanoporous structure, which can fully accommodate the volume fluctuations of Sb during cycling; in addition, Cu in Cu₂Sb is electrochemically inactive and can form atomic-scale confinement on the volume expansion of Sb; in addition, the presence of Sb₂O₃ can further alleviate the volume fluctuation amplitude of Sb by using the intermediate layer product Na₂O generated during its sodium intercalation process while increasing the theoretical specific capacity of the Sb material to a certain extent. By exerting the synergistic strengthening effect of the beneficial effects of the nanoporous structure, the inert Cu component, and the active Sb₂O₃, the cycle stability of the Sb-based composite electrode material is improved.

Description

Technical Field

[0001] The present invention relates to the field of energy storage material preparation, and in particular to a single-step dealloying preparation method for a highly stable antimony-based composite electrode material. Background Art

[0002] Currently, sodium-ion batteries, with their resource and cost advantages, have become an important complementary technology to lithium-ion batteries. However, the theoretical specific capacity of the currently widely used carbon anode materials is low, which restricts further improvement of the energy density of sodium-ion batteries and limits their industrial application. Compared with carbon anode materials, metallic antimony (Sb) has a higher theoretical specific capacity and is currently the most promising anode material for sodium-ion batteries. However, Sb undergoes huge volume fluctuations during the process of sodium insertion and extraction, and is prone to pulverization, resulting in rapid capacity decay.

[0003] In order to effectively alleviate the huge volume fluctuation problem of Sb materials during charging and discharging, the following methods are often used:

[0004] (1) Structural improvement of electrode materials. This method is to construct sponge-like through-hole micro- and nano-pore spaces in dense Sb materials, that is, to prepare porous Sb, so as to alleviate the apparent volume expansion of Sb and thereby effectively improve the cycle stability of Sb. Currently, there are many technologies that can realize the preparation of porous metals, such as template method, vapor deposition method, sol-gel method, pyrolysis method, dealloying method, etc. Among them, the dealloying method is more suitable for large-scale production due to its low cost, simple operation, and strong controllability of pore size, and has broad application prospects;

[0005] (2) Introducing electrochemically inert components to form a composite electrode. This method is to dope Sb with a component M that is not electrochemically active (no volume change during the sodium insertion and removal process) (forming a compound or mixing), and using this component to form a volume expansion limit for Sb, thereby inhibiting the pulverization of Sb and thus improving its cycle life. Compared with mechanical mixing, the construction of the Sb intermetallic compound M x Sb 1-x It can establish an interatomic bond between M and Sb, and maximize the confinement effect of M on Sb;

[0006] (3) Construct electrochemically active antimony compounds to partially replace Sb. Among the many antimony compounds, antimony oxide (Sb2O3) not only has a higher theoretical specific capacity than Sb, but the intermediate layer product Na2O generated during the sodium insertion process can act as a buffer phase for Sb volume fluctuations, thereby alleviating Sb pulverization and improving its cycling performance to a certain extent.

[0007] In view of this, in order to maximize the expansion confinement effect on Sb negative electrode materials during the electrochemical cycling process, the current research on Sb-based negative electrode materials often tends to adopt a method that combines multiple design ideas in the above methods to prepare complex-structured Sb-based composite materials with active / inert buffer phases and nanoporous channels, so as to maximize the cycling stability of Sb-based negative electrode materials. However, the preparation process often involves multiple steps such as heat treatment, hydrothermal treatment, and ball milling, which is rather cumbersome, increases the material preparation cost and has low production efficiency, limiting the wide industrial manufacturing and application of high-performance Sb-based composite electrode materials. On this basis, there are few reports on methods that can prepare Sb-based composite electrode materials with complex structures in a single step. Summary of the Invention

[0008] In view of the above technical problems, the present invention combines three methods: structural nanoporosity, introduction of electrochemically inert buffer phases, and construction of Sb oxides, and proposes a new method for preparing Sb-based negative electrode composite materials by a single-step dealloying method. The present invention designs a Mg-rich Mg-Cu-Sb ternary alloy with a specific composition range, and then obtains a Cu2Sb / Sb2O3 composite electrode material with high cycling stability in one step by a simple chemical etching method. Among them, Cu2Sb has a nanoporous structure and can fully accommodate the volume fluctuation of Sb during cycling; in addition, Cu in Cu2Sb does not have electrochemical activity and can form atomic-scale confinement on the volume expansion of Sb; in addition, the presence of Sb2O3 can further alleviate the volume fluctuation amplitude of Sb by using the intermediate layer product Na2O generated during its sodiation process while increasing the theoretical specific capacity of Sb materials to a certain extent. By exerting the synergistic strengthening effect of the beneficial effects of the nanoporous structure, inert Cu component, and active Sb2O3, the cycling stability of the Sb-based composite electrode material is effectively improved.

[0009] Aiming at the problem of poor cycling stability of Sb materials as negative electrode materials for sodium-ion batteries, the present invention modifies Sb negative electrode materials from three aspects: the structure, composition, and phase of the material. A new method for preparing Sb-based negative electrode composite materials by a single-step dealloying method is adopted, that is, by designing a Mg-rich Mg-Cu-Sb ternary alloy with a specific composition range, and then obtaining a Cu2Sb / Sb2O3 composite electrode material with high cycling stability in one step by a simple chemical etching method. The present invention provides a new idea for preparing composite electrode materials with complex structures and high performance for secondary batteries by the dealloying method.

[0010] The specific steps of the basic technical solution of the present invention are summarized as follows:

[0011] I. Preparation of Mg-Cu-Sb alloy: The metallic Mg, metallic Cu, and metallic Sb are uniformly mixed according to a certain molar fraction ratio. The mixed powder is placed in a vacuum arc melting furnace. Under a certain vacuum degree and at an appropriate current magnitude, the mixed powder is melted for a certain period of time to obtain an alloy ingot. Subsequently, after turning the alloy ingot over, the melting is repeated several times with the same parameters, and finally, a Mg-Cu-Sb alloy ingot with uniform composition is obtained.

[0012] II. Dealloying: The Mg-Cu-Sb alloy ingot obtained in Step I is cut into alloy foil sheets with a certain thickness by wire electrical discharge machining. The foil sheets are polished to remove the wire cutting marks on their surfaces, and then they are ultrasonically cleaned in absolute ethanol and acetone for a certain period of time respectively. The obtained clean alloy foil sheets are placed in a hydrochloric acid solution with a certain concentration and left standing at room temperature until no new bubbles are generated in the alloy foil sheets, and then all the solution is removed with a dropper.

[0013] III. Cleaning and drying: The product obtained in Step II is ultrasonically cleaned with absolute ethanol several times, and then the product is placed in a vacuum drying oven and dried under a certain vacuum degree and temperature for a certain period of time to obtain the target product, the porous Cu2Sb / Sb2O3 composite material.

[0014] In Step I, the molar fraction ratio of the metallic Mg, metallic Cu, and metallic Sb is (1 - x - y):x:y, where 3x + 2.5y < 100% and x < 2y.

[0015] In Step I, the vacuum degree of the vacuum arc melting is less than 5×10 -2 Pa, the current magnitude is 20 A to 60 A, the melting duration of the mixed powder is 5 to 15 s, and the melting is repeated 3 to 5 times with the same parameters.

[0016] In Step II, the thickness of the cut alloy sheets is 0.5 mm to 3 mm, and they are ultrasonically cleaned in absolute ethanol and acetone for 5 to 10 min respectively.

[0017] In Step II, the concentration of hydrochloric acid is 0.1 mol / L to 2 mol / L, and the room temperature refers to 20°C to 25°C.

[0018] In Step III, the product is ultrasonically cleaned with absolute ethanol 2 to 4 times, the vacuum degree of the vacuum drying is 1×10 -2 Pa, the drying temperature is 20°C to 60°C, and the treatment time is 20 min to 2 h.

[0019] The beneficial effects of the present invention are:

[0020] 1. Cu2Sb has a nanoporous structure that can fully accommodate the volume fluctuations of Sb during cycling. In addition, Cu in Cu2Sb is electrochemically inactive and can form atomic-scale confinement on the volume expansion of Sb. Moreover, the presence of Sb2O3 can further alleviate the volume fluctuation amplitude of Sb by using the intermediate layer product Na2O generated during its sodiation process while increasing the theoretical specific capacity of the Sb material to a certain extent. By exerting the synergistic strengthening effect of the beneficial effects of the nanoporous structure, inert Cu component, and active nanoporous Sb2O3, the cycling stability of the Sb-based composite electrode material is effectively improved. A one-step dealloying preparation method for a highly stable antimony-based composite electrode material has the following advantages:

[0021] 2. The present invention realizes the rapid preparation of a complex-structured Sb-based composite electrode material by one-step dealloying at room temperature. The method is simple and efficient, can effectively improve production efficiency and reduce production costs, and is suitable for industrial production.

[0022] 3. The present invention can control the composition ratio of Cu2Sb and Sb2O3 in the composite electrode material by changing the ratio of metallic Cu and metallic Sb, and thus can precisely regulate the cycling stability, specific capacity, and rate performance of the composite electrode material according to the usage requirements.

[0023] 4. The prepared Cu2Sb / Sb2O3 composite electrode material has a nanoporous structure, a large surface area, a high specific capacity, and excellent cycling stability. In addition, it realizes the expansion confinement synergistic effect on the volume fluctuations of Sb during cycling from multiple angles, and can more effectively improve the cycling stability of the Sb material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the secondary electron morphology of the porous Cu2Sb / Sb2O3 composite material prepared in Example 1 by the specific implementation method. It can be seen that the loose and porous Cu2Sb nanosheets wrap the Sb2O3 nanosheets, and the phases are evenly distributed, non-agglomerated, and a large space is reserved for the electrochemical volume fluctuations of the Sb matrix, which is beneficial to improving the cycling stability of the electrode material.

[0025] Figure 2 It is the X-ray diffraction spectrum of the porous Cu2Sb / Sb2O3 composite material prepared in Example 2 by the specific implementation method. It can be seen that the typical characteristic peaks of the product are consistent with the characteristic peaks of the standard cards ICDD PDF#85-0492 and ICDD PDF#43-1071 of Cu2Sb and Sb2O3, proving the formation of the above two phases.

[0026] Figure 3Electrochemical cycling stability test curve of the porous Cu2Sb / Sb2O3 composite material prepared by the specific embodiment of Example 4. It can be seen that the capacity retention rate of the electrode material is still as high as 87% after 220 charge-discharge cycles at a high current density of 2 A·g -1 , indicating that the porous Cu2Sb / Sb2O3 composite material prepared by this patent has high cycling stability. Specific Embodiment

[0027] Aiming at the problem of poor cycling stability of Sb materials as anode materials for sodium-ion batteries, this invention modifies the Sb anode material from three aspects: the structure, composition, and phase of the material. A new method for preparing Sb-based anode composite materials by a one-step dealloying method is adopted, that is, by designing a Mg-rich Mg-Cu-Sb ternary alloy with a specific composition range, and then using a simple chemical corrosion method to obtain a Cu2Sb / Sb2O3 composite electrode material with high cycling stability in one step. Among them, Cu2Sb has a nanoporous structure, which can fully accommodate the volume fluctuation of Sb during cycling; in addition, Cu in Cu2Sb is electrochemically inactive and can form an atomic-scale confinement for the volume expansion of Sb; in addition, the presence of Sb2O3 can further alleviate the volume fluctuation amplitude of Sb by using the intermediate layer product Na2O generated during the sodiation process on the basis of a certain improvement in the theoretical specific capacity of Sb materials. By giving full play to the synergistic strengthening effect of the beneficial effects of the nanoporous structure, inert Cu component, and active Sb2O3, the cycling stability of the Sb-based composite electrode material is effectively improved.

[0028] Example 1: A one-step dealloying preparation method of a high-stability antimony-based composite electrode material:

[0029] I. Preparation of Mg-Cu-Sb alloy: Uniformly mix elemental Mg, elemental Cu, and elemental Sb in a molar fraction ratio of 65%:15%:20%. Place the mixed powder in a vacuum arc melting furnace. Under a vacuum of 3×10 -2 Pa and a current of 30 A, melt the mixed powder for 10 s to obtain an alloy ingot. Then, turn the alloy ingot over and repeat the melting 3 times with the same parameters to finally obtain a Mg-Cu-Sb alloy ingot with uniform composition;

[0030] II. Dealloying: Cut the Mg-Cu-Sb alloy ingot obtained in step I into alloy foil sheets with a thickness of 1 mm by wire electrical discharge machining, polish the foil sheets to remove the wire electrical discharge machining marks on their surfaces, and then ultrasonically clean them in absolute ethanol and acetone for 5 min respectively. Place the obtained clean alloy foil sheets in a hydrochloric acid solution with a concentration of 1 mol / L and let them stand at 20°C until no new bubbles are generated in the alloy foil sheets, and then slowly remove all the solutions with a dropper;

[0031] III. Cleaning and Drying: The product obtained in Step II is ultrasonically cleaned three times with absolute ethanol, and then the product is placed in a vacuum drying oven and dried for 30 min under a vacuum degree of 1×10 -2 Pa and at an environment temperature of 40 °C to obtain the target product, the porous Cu2Sb / Sb2O3 composite material.

[0032] The beneficial effects of this embodiment are as follows: Cu2Sb has a nanoporous structure, which can fully accommodate the volume fluctuation of Sb during cycling; in addition, Cu in Cu2Sb does not have electrochemical activity and can form atomic-scale confinement on the volume expansion of Sb; furthermore, the presence of Sb2O3 can, on the basis of improving the theoretical specific capacity of the Sb material to a certain extent, further alleviate the volume fluctuation amplitude of Sb by using the intermediate layer product Na2O generated during its sodiation process. By giving full play to the synergistic strengthening effect of the beneficial effects of the nanoporous structure, inert Cu component, and active Sb2O3, the cycling stability of the Sb-based composite electrode material is effectively improved.

[0033] Example 2: The difference between this embodiment and Example 1 is that in Step I, metallic Mg, metallic Cu, and metallic Sb are uniformly mixed in a molar fraction ratio of 70%:15%:15%.

[0034] Example 3: The difference between this embodiment and Example 1 is that under a vacuum degree of 3×10 -2 Pa and at a current of 55 A, the mixed powder is melted for 5 s to obtain an alloy ingot.

[0035] Example 4: The difference between this embodiment and Example 1 is that the concentration of hydrochloric acid used in Step II is 0.3 mol / L.

[0036] Example 5: The difference between this embodiment and Example 1 is that in Step III, it is dried for 20 min under a vacuum degree of 1×10 -2 Pa and at an environment temperature of 60 °C to obtain the target product, the porous Cu2Sb / Sb2O3 composite material.

Claims

1. A single-step dealloying preparation method for a highly stable antimony-based composite electrode material, characterized in that, The specific steps are as follows: (1) Preparation of Mg-Cu-Sb alloy: The metal Mg, metal Cu, and metal Sb are uniformly mixed in a certain molar fraction ratio. The molar fraction ratio of metal Mg, metal Cu, and metal Sb is (1 - x - y):x:y, where 3x + 2.5y < 100% and x < 2y; The mixed powder is placed in a vacuum arc melting furnace. Under a certain vacuum degree and at an appropriate current, the mixed powder is melted for a certain period of time to obtain an alloy ingot. Subsequently, after the alloy ingot is turned over, the melting is repeated several times with the same parameters, and finally a Mg-Cu-Sb alloy ingot with uniform composition is obtained; (2) Dealloying: The Mg-Cu-Sb alloy ingot obtained in step (1) is cut into alloy foil sheets with a certain thickness by wire electrical discharge machining, and the wire cutting marks on the surface of the foil sheets are removed by polishing. Subsequently, they are ultrasonically cleaned in absolute ethanol and acetone for a certain period of time respectively; The obtained clean alloy foil sheets are placed in a hydrochloric acid solution with a certain concentration and left standing at room temperature until no new bubbles are generated in the alloy foil sheets. Subsequently, all the solution is removed with a dropper; (3) Cleaning and drying: The product obtained in step (2) is ultrasonically cleaned with absolute ethanol several times, and then the product is placed in a vacuum drying oven and dried under a certain vacuum degree and temperature for a certain period of time to obtain the target product, the porous Cu2Sb / Sb2O3 composite material.

2. The one-step dealloying preparation method of a highly stable antimony-based composite electrode material as described in claim 1, characterized in that, In step (i), the vacuum degree of vacuum arc melting is less than 5×10 -2 Pa, the current magnitude is 20 A to 60 A, the melting duration of the mixed powder is 5 to 15 s, and the melting is repeated 3 to 5 times using the same parameters.

3. The single-step dealloying preparation method of a highly stable antimony-based composite electrode material as claimed in claim 1, characterized in that, In step (2), the thickness of the alloy sheets obtained by cutting is 0.5 mm to 3 mm, and they are ultrasonically cleaned in absolute ethanol and acetone for 5 to 10 minutes respectively.

4. The one-step dealloying preparation method of a highly stable antimony-based composite electrode material according to claim 1, characterized in that, In step (2), the concentration of hydrochloric acid is 0.1 mol / L to 2 mol / L, and room temperature refers to 20°C to 25°C.

5. The single-step dealloying preparation method of a highly stable antimony-based composite electrode material as claimed in claim 1, characterized in that, In step (iii), the product is ultrasonically cleaned with absolute ethanol 2 - 4 times, and the vacuum degree for vacuum drying is 1×10 -2 Pa, the drying temperature is 20℃ - 60℃, and the treatment time is 20 min - 2 h.

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