A tin antimony sodium alloy / carbon composite negative electrode material based on Na 15 A preparation method of a tin antimony sodium alloy / carbon composite negative electrode material based on Sn4 precursor

Abstract

The application discloses a kind of based on Na 15 Preparation method of tin antimony sodium alloy / carbon composite negative electrode material of Sn4 precursor. The method will Na 15 Sn4 powder, Sb powder and conductive carbon black are mixed, and carbon-coated NaSnSb alloy composite material is directly prepared by in-situ solid phase alloying reaction. The special feature of this method is that the addition of Sb triggers the decomposition and reconstruction of Na 15 Sn4 precursor, in-situ generates embedded composite structure composed of Sn-Sb alloy nanocrystals and sodium compound buffer matrix, and produces synergistic enhancement effect with the external carbon coating layer. The material not only eliminates the risk of sodium dendrite from the sodium storage mechanism, but also effectively solves the volume expansion problem in the cycle process through its unique microstructure, significantly improves the cycle stability and rate performance of the electrode, and is especially suitable for the all-solid-state battery system with extremely high safety requirement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid-state batteries, and particularly relates to a Sn4-based Sn-Sb-Na alloy / carbon composite negative electrode material 15 The application relates to a preparation method of a tin-antimony-sodium alloy / carbon composite negative electrode material based on a Sn4 precursor, in particular to a preparation method of a carbon-coated sodium-tin-antimony alloy composite material for a full-solid-state sodium ion battery. BACKGROUND

[0002] With the rapid development of renewable energy and smart grid, there is an urgent need for large-scale, low-cost and high-safety electrochemical energy storage technology. Sodium ion batteries are one of the most promising candidates due to the abundant resource and low cost of sodium. Among various sodium ion battery anode materials, alloy-based materials (such as Sn, Sb, Ge, etc.) have attracted much attention due to their high theoretical specific capacity. Among them, SnSb is considered to be an alloy anode with great application prospect, with a theoretical capacity as high as 853 mAh g -1 However, it undergoes severe volume change (usually more than 300%) during charge and discharge, which causes material particle pulverization and continuous rupture and regeneration of the interface film with the solid-state electrolyte, ultimately leading to rapid capacity and cycle life decay.

[0003] To address the above challenges, the prior art usually adopts the following strategies, but they each have limitations that are difficult to overcome:

[0004] (1) Multi-element alloying strategy and its limitations:

[0005] Researchers have attempted to alleviate the volume effect by preparing binary or ternary alloys (such as SnSb alloy). However, the current mainstream synthesis method, such as high-temperature smelting, has significant drawbacks: first, this process requires handling extremely reactive sodium metal, which has very high safety requirements for production equipment and huge energy consumption; second, high temperatures can lead to element segregation, making it difficult to obtain alloys with uniform composition; most importantly, this method usually produces bulk alloys or coarse particles with uniform composition, which lack effective nanoscale and microstructure design to buffer stress, and the volume expansion problem is only partially alleviated, not fundamentally solved.

[0006] (2) Carbon coating strategy and its limitations:

[0007] Introducing carbon materials (such as conductive carbon black, graphene) to construct a composite structure is another common approach. However, the existing methods mostly use a two-step method of "first synthesizing the alloy, then coating the carbon". The binding force between this subsequently introduced carbon layer and the alloy particles is usually weak, mostly physical adhesion. Under the great stress of long-term cycling, this fragile interface is prone to breakage and detachment, and cannot effectively and continuously conduct electrons and bind volume expansion, resulting in limited performance improvement.

[0008] (3) The absence of pre-sodiation strategy:

[0009] In addition, alloy anodes generally have the problem of low first coulombic efficiency, which is due to the irreversible consumption of a large number of sodium ions in the formation of a solid-state electrolyte interface film (SEI). In the prior art, single Sn, Sb, etc. are directly used as anodes, and no additional sodium source is provided to compensate for this consumption, resulting in a decrease in the energy density of the full battery.

[0010] In summary, the prior art is still seeking a material design and preparation method that can simultaneously solve the problems of intrinsic volume expansion, interface stability and low first coulombic efficiency of alloy anodes. In particular, how to actively construct a stable composite structure that can inherently suppress stress and has excellent conductive network and pre-sodiation characteristics at the atomic / nano scale through a safe, efficient and easy-to-industrialize process is still a technical bottleneck faced by those skilled in the art.

[0011] The purpose of the present application is to overcome the shortcomings of the prior art and provide a completely new solution. SUMMARY

[0012] The purpose of the present application is to overcome the shortcomings of the prior art and provide a completely new solution. 15 The present application provides a preparation method of a tin-antimony-sodium alloy / carbon composite anode material based on a Na

[0013] The present application aims to provide a method for preparing a carbon-coated tin-antimony-sodium alloy composite material by in-situ alloying reaction through ball milling of a pre-sodiated Na 15 Sn4 alloy as a precursor and Sb powder. The method is safe and efficient, and the obtained material has a unique "active nanocrystal-buffer matrix-conductive carbon layer" multi-level structure, effectively solving the technical bottlenecks of low electronic conductivity and large volume expansion of alloy anode materials, and providing a reliable anode solution for obtaining high-performance, long-life full-solid-state sodium ion batteries.

[0014] The purpose of the present application can be achieved by the following scheme:

[0015] The present application provides a preparation method of a tin-antimony-sodium alloy / carbon composite anode material based on a Na 15 Sn4 precursor, comprising the following steps: mixing Na 15 Sn4 powder, Sb powder and conductive carbon black, and obtaining a tin-antimony-sodium alloy / carbon composite anode material after ball milling.

[0016] As an embodiment of the present application, the mixing is carried out in an inert gas atmosphere.

[0017] As an embodiment of the present application, the conductive carbon black is Super P.

[0018] As one embodiment of the present invention, Na 15 The stoichiometric ratio of Sn4 powder to Sb powder is 8-12:50-100, preferably 8-12:85-95, and more preferably 8-12:88-92. In the metal mixed powder, Na, in stoichiometric proportions... 15 The proportion of Sn4 powder is 8%-12%; the metal mixed powder includes Na 15 Sn4 powder, Sb powder.

[0019] In one embodiment of the present invention, the mass ratio of the metal mixed powder to the conductive carbon black is 9-11:1, preferably 10:1; the metal mixed powder includes Na. 15 Sn4 powder, Sb powder.

[0020] In one embodiment of the present invention, the ball milling speed is 300~600 rpm, and the milling is paused for 4~10 minutes every 10~40 minutes, with a total milling time of 4~10 hours. Preferably, the ball milling speed is 450~550 rpm, and the milling is paused for 4~6 minutes every 25~35 minutes, with a total milling time of 4~6 hours.

[0021] To address the issue of volume expansion in alloy-based anode materials, existing technologies often employ a two-step method: "first synthesizing the alloy, then carbon coating." This method typically results in alloy-based anode materials with weak bonding between the carbon layer and alloy particles, and excessive grain growth during the Sn-Sb alloying process, leading to a decrease in the performance of the Sn-Sb alloy anode. This invention incorporates conductive carbon into the ball mill jar during the alloy preparation process, providing a conductive network and limiting excessive Sn-Sb grain growth, resulting in Sn-Sb nanocrystals. These nanocrystals then form a strong interfacial fusion with the composite material through mechanochemical interactions.

[0022] The present invention provides a carbon-coated sodium-tin-antimony alloy composite material obtained by the preparation method described above.

[0023] This invention provides an application of the sodium-tin-antimony alloy composite material in the preparation of all-solid-state sodium-ion batteries.

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

[0025] (1) Sodium metal anodes are prone to forming sodium dendrites during cycling. These dendrites can pierce the sulfide electrolyte, causing internal short circuits in the battery, leading to thermal runaway or even fire and explosion. This invention constructs an alloy anode material, Na... 15 Sn4 and Sb together form an intercalation alloy anode that stores sodium ions through an alloying reaction, fundamentally eliminating the possibility of dendrite growth and greatly improving the intrinsic safety of all-solid-state batteries.

[0026] (2) Single alloy anode (such as pure Na) 15 Sn4 still suffers from volume expansion issues. This invention introduces Sb for compounding and ball milling, constructing a buffer structure inside the alloy anode, thereby improving the material's cycle stability. Due to its unique pre-sodiumization structure and buffering mechanism, the material achieves an initial coulombic efficiency of 89.38%, significantly higher than the 70% of conventional alloys.

[0027] (3) Sodium metal is an active metal with extremely high reducing power. It reacts violently and continuously with sulfide electrolytes to form a thick and unstable interfacial phase, resulting in huge interfacial impedance and rapid consumption of active substances. Attached Figure Description

[0028] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1 SEM image (1 μm) of the material in Example 1;

[0030] Figure 2 EDS analysis chromatogram (5 μm) of Example 1;

[0031] Figure 3 The negative electrode interface diagrams for Example 1 and Comparative Example 2 after cycling at 0.1C are shown.

[0032] Figure 4 A comparison of the discharge capacity of different materials after cycling at 0.1C;

[0033] Figure 5 The charge-discharge specific capacity diagram is shown for Example 1 after 100 cycles at 0.1C. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0035] This invention provides a method for preparing a carbon-coated sodium-tin-antimony alloy composite material for all-solid-state sodium-ion batteries, comprising the following steps:

[0036] S1. In a glove box filled with an inert gas atmosphere, weigh the raw materials according to the stoichiometric ratio and transfer them to a mortar. Grind them manually to mix the raw materials evenly.

[0037] S2. Weigh the ball milling media according to a certain ball-to-material ratio, transfer the uniformly mixed powder and ball milling media into a zirconia ball milling jar, and ball mill under an argon atmosphere at a certain speed and time.

[0038] S3. Finally, after the ball milling is completed, the composite material is scraped off from the milling jar and placed in a sample bottle in a glove box for storage.

[0039] The alloy anode material of this invention is made by using Na 15 Carbon-coated NaSnSb alloy composites are directly prepared by mixing Sn4 powder, Sb powder, and conductive carbon black through an in-situ solid-state alloying reaction. The unique aspect of this method is that the addition of Sb triggers the Na... 15 The decomposition and reconstruction of the Sn4 precursor resulted in the in-situ generation of an embedded composite structure composed of Sn-Sb alloy nanocrystals and a sodium compound buffer matrix, which synergistically enhanced the structure with the external carbon coating layer. This material not only eliminates the risk of sodium dendrite formation from the perspective of sodium storage mechanism, but also effectively solves the volume expansion problem during cycling through its unique microstructure, significantly improving the cycle stability and rate performance of the electrode. It is particularly suitable for all-solid-state battery systems with extremely high safety requirements.

[0040] Example 1

[0041] (1) In a glove box filled with an inert gas atmosphere, weigh out Na in a stoichiometric ratio of 1:9. 15 Transfer 2g of Sn4 powder and Sb powder to a mortar, then weigh out 0.2g of Super P powder and put it into the mortar. Grind manually to mix the raw materials evenly.

[0042] (2) Weigh 5mm zirconia grinding beads according to a ball-to-material ratio of 40:1. Transfer the uniformly mixed powder and grinding media to a 100ML zirconia grinding jar. Grind the powder at 500rpm under an argon atmosphere. Pause for 5min every 30min to prevent the temperature generated during grinding from affecting the material. The total grinding time is 5h.

[0043] (3) Finally, the prepared Na 15 The Sn4-Sb@C composite material was scraped from the ball mill jar and stored in a glove box sample bottle.

[0044] Examples 2-7

[0045] This embodiment provides an alloy / carbon composite anode material, the preparation method of which is basically the same as that in Example 1, the only difference being the alloy powder and its proportion, as shown in Table 1 below:

[0046] Table 1

[0047]

[0048] Comparative Example 1

[0049] (1) In a glove box filled with an inert gas atmosphere, the purchased sodium block was rolled out by hand with a stainless steel rolling pin into a sodium sheet with a thickness of about 400 micrometers, and then cut into a round sodium sheet with a diameter of 9 mm.

[0050] Comparative Example 2

[0051] (1) In a glove box filled with an inert gas atmosphere, according to Na 15 Weigh out the purchased Na powder and Sn powder separately and transfer them to a mortar. Grind them manually to mix the raw materials evenly.

[0052] (2) Weigh 5mm zirconia grinding beads according to a ball-to-material ratio of 40:1. Transfer the uniformly mixed powder and grinding media to a 100ML zirconia grinding jar. Grind the powder at 500rpm under an argon atmosphere. Pause for 5min every 30min to prevent the temperature generated during grinding from affecting the material. The total grinding time is 15h.

[0053] (3) Finally, the Na prepared after ball milling 15 After being scraped from the ball mill jar, the Sn4 composite material was stored in a sample vial in a glove box.

[0054] Comparative Example 3

[0055] This comparative example provides an alloy / carbon composite anode material, the preparation method of which is basically the same as that in Example 1, the only difference being that Na is prepared first. 15 Sn4-Sb composite material, then ball-milled with Super P.

[0056] The steps are as follows:

[0057] (1) In a glove box filled with an inert gas atmosphere, weigh out Na in a stoichiometric ratio of 1:9. 15 Mix 2g of Sn4 powder and 2g of Sb powder in a mortar and grind manually until the raw materials are evenly mixed.

[0058] (2) Weigh 5mm zirconia grinding beads according to a ball-to-material ratio of 40:1. Transfer the uniformly mixed powder and grinding media to a 100ML zirconia grinding jar. Grind the powder at 500rpm under an argon atmosphere. Pause for 5min every 30min to prevent the temperature generated during grinding from affecting the material. The total grinding time is 5h.

[0059] (3) Finally, the Na after the ball milling was completed 15After scraping the Sn4-Sb composite material from the ball mill jar, weigh it and add 0.2g of Super P to a 100ml zirconia ball mill jar at a mass ratio of 10:1. The ball-to-material ratio is 20:1, and the ball diameter is 5mm. The ball milling is carried out at 500rpm under an argon atmosphere, with a 5min pause every 30min to prevent the temperature generated during the ball milling process from affecting the material. The total ball milling time is 5h.

[0060] (4) After the ball milling in step (3) is completed, put the material into the glove box and scrape off the material and put it into the sample bottle for storage.

[0061] Comparative Example 4

[0062] This comparative example provides an alloy / carbon composite anode material, the preparation method of which is basically the same as that in Example 1, the only difference being that Na is used... 15 Sn4 powder and Sb powder are replaced with an equal amount of Na3Sb powder (2g) and mixed with 0.2g Super P powder.

[0063] Comparative Example 5

[0064] This comparative example provides an alloy / carbon composite anode material, and the preparation method is basically the same as that in Example 1, except that Sb powder is replaced with an equal amount of Na3Sb powder.

[0065] Comparative Example 6

[0066] This comparative example provides an alloy / carbon composite anode material, and the preparation method is basically the same as that in Example 1, except that: Na powder, Sn powder, and Sb powder are weighed out according to the same stoichiometric ratio and mixed with Super P powder.

[0067] Comparative Example 7

[0068] This comparative example provides an alloy / carbon composite anode material, and the preparation method is basically the same as that in Example 1, except that Sn powder and Sb powder are weighed out according to the same stoichiometric ratio and mixed with Super P powder.

[0069] The materials prepared in the examples and comparative examples were characterized:

[0070] (1) SEM

[0071] The ball-milled composite material exhibits a relatively uniform particle distribution, mainly composed of submicron and nano-sized secondary agglomerates. At high magnification (e.g., Figure 1 As shown in the figure, Na can be clearly observed. 15Sn4-Sb alloy particles are tightly wrapped and connected by a loose, porous network of conductive carbon black (Super P). These carbon layers are not completely dense films, but rather adhere to the surface of the alloy particles in a "grape bunch" morphology, forming a typical rudimentary 'core-shell' structure. This structure ensures good electronic contact between the active material particles, while its porosity also provides channels for electrolyte wetting and rapid sodium ion transport.

[0072] (2) EDS

[0073] To verify the structure of the composite material in Example 1, it was characterized by EDS (e.g., Figure 2 This study confirms that the four elements Sn, Sb, Na, and C exhibit a highly uniform distribution in the composite material, indicating that the components have achieved nanoscale homogeneity. Furthermore, the signal distributions of the composite Sn and Sb elements highly overlap, suggesting that the two metal components have achieved uniform composite at the nanoscale. The signal of the C element forms a continuous network framework covering the entire field of view, perfectly superimposed on the distribution areas of Sn and Sb elements. This strongly demonstrates that the conductive carbon is not simply a mixture, but rather a successful construction of a three-dimensional conductive network coating the surface of the alloy particles and penetrating the entire composite material.

[0074] Performance tests were performed on the materials prepared in the examples and comparative examples:

[0075] (1) Performance testing of all-solid-state batteries

[0076] 100 mg of sulfide electrolyte (Na3SbS4) was weighed and placed in a ceramic mold. The electrolyte sheet was pressed at 180 MPa for 2 min. Then, 2 mg of positive electrode material (TiS2) was added to one side of the electrolyte, and the pressure was applied again at 360 MPa for 2 min. Subsequently, negative electrode material (Na3SbS4 prepared in Example 1) was added to the other side. 15 100 mg of Sn4-Sb@C alloy anode material, sodium sheet (Comparative Example 1), and Na prepared in Comparative Example 2. 15 (100 mg of Sn4 alloy material, 100 mg of material from Comparative Example 3, etc.) were pressed at 360 MPa for 1 minute. Finally, Al current collectors were added to the positive electrode side and Cu current collectors to the negative electrode side. The battery mold was removed from the glove box and placed on a stainless steel fixture, then subjected to 38 MPa pressure to obtain a sandwich-type all-solid-state battery. The pressurized battery was placed in the Blue Electric testing system, and a constant current charge-discharge mode was set. At room temperature, in a 0.1C constant current charge-discharge mode, the charge-discharge specific capacity and capacity retention rate were tested after 100 cycles, as shown in Table 2. The Na4 alloy materials prepared in Examples 1, 2, and 3 were... 15 The discharge capacity of the Sn4-Sb composite material after 0.1C cycling is compared to that of... Figure 4 As shown.Figure 5 The charge-discharge specific capacity diagram is shown for Example 1 after 100 cycles at 0.1C.

[0077] (2) Interface stability test

[0078] Negative electrode interface after 0.1C long cycle Figure 3 As shown, Na can be seen 15 The presence of cracks at the interface of the Sn4 anode material confirms that the cracks are caused by volume expansion due to interfacial expansion. Meanwhile, the Na... 15 The absence of obvious cracks in the Sn4-Sb@C alloy anode material proves that the addition of Sb powder to construct a buffer layer solved the problem of volume expansion of the anode material.

[0079] Table 2

[0080]

[0081] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method based on Na 15 The method for preparing a tin-antimony-sodium alloy / carbon composite anode material based on Sn4 precursor is characterized by... The steps include: Na 15 Sn4 powder, Sb powder, and conductive carbon black were mixed and ball-milled to obtain a tin-antimony-sodium alloy / carbon composite anode material.

2. The method for preparing the tin-antimony-sodium alloy / carbon composite anode material according to claim 1, characterized in that, The mixing is carried out in an inert gas atmosphere.

3. The method for preparing the tin-antimony-sodium alloy / carbon composite anode material according to claim 1, characterized in that, The conductive carbon black is Super P.

4. The method for preparing the tin-antimony-sodium alloy / carbon composite anode material according to claim 1, characterized in that, Na 15 The stoichiometric ratio of Sn4 powder to Sb powder is 5~25:75~95.

5. The method for preparing the tin-antimony-sodium alloy / carbon composite anode material according to claim 1, characterized in that, The mass ratio of the metal mixed powder to the conductive carbon black is 9-11:1; the metal mixed powder includes Na. 15 Sn4 powder, Sb powder.

6. The method for preparing the tin-antimony-sodium alloy / carbon composite negative electrode material according to claim 1, characterized in that, The ball milling speed is 300~600 rpm. During ball milling, pause for 4~10 minutes every 10~40 minutes. The total ball milling time is 4~10 hours.

7. A tin-antimony-sodium alloy / carbon composite anode material obtained by the preparation method as described in claim 1.

8. The application of the method for preparing the tin-antimony-sodium alloy / carbon composite anode material as described in claim 7 in the preparation of all-solid-state sodium-ion batteries.

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