Conductive interface modified sodium battery alloy foil negative electrode material, preparation method therefor and use thereof

Abstract

A conductive interface modified sodium battery alloy foil negative electrode material, a preparation method therefor and the use thereof. The conductive interface modified sodium battery alloy foil negative electrode material comprises: a sodium ion battery alloy foil negative electrode and a conductive modification layer completely attached to the bottom surface of the sodium ion battery alloy foil negative electrode, wherein the sodium ion battery alloy foil negative electrode is a whole foil body, which does not contain a conductive agent and a binder, the surface being attached to or not attached to a current collector. The conductive modification layer comprises a carbon-based conductive modification layer prepared by means of a coating process or a metal-based conductive modification layer prepared by means of a plating process. The mass proportion of a conductive material in the conductive interface modified sodium battery alloy foil negative electrode material is less than 50%.

Description

Conductive interface modified sodium battery alloy foil negative electrode material and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 18, 2023, with application number 202311203885.0 and invention name “Conductive interface modified sodium battery alloy foil negative electrode material and its preparation method and application”. Technical Field

[0002] The present invention relates to the technical field of sodium battery negative electrodes, and in particular to a conductive interface modified sodium battery alloy foil negative electrode material, a preparation method thereof, and applications thereof. Background Art

[0003] As one of the energy storage technologies currently developing alongside renewable energy, sodium-ion batteries have experienced over 50 years of development, with performance and various indicators becoming mature and stable. Improving the reversible specific capacity of sodium-ion battery cathode and anode materials remains a key research focus and challenge in this field. Currently, sodium-ion battery anodes are primarily based on amorphous carbon materials, which have reached maturity in terms of specific capacity. To further enhance the energy density of sodium-ion battery cells, alloy anode systems based on alloying reactions with sodium (e.g., elements such as tin, bismuth, and antimony) are an important choice for next-generation sodium-ion battery anode materials.

[0004] Alloy anode materials experience large volume expansion during the reaction process (for example, tin expands by 4.2 times), which makes them prone to cracking, pulverization, and rapid capacity decay during the cycling of sodium-ion batteries. At the same time, some alloy anode materials are not compatible with mainstream carbonate-based electrolytes, and some materials have poor kinetics that affect rate performance. This seriously hinders the manufacture and further application of alloy anode materials. Developing sodium-ion battery alloy anode materials with higher specific capacity, excellent cycle performance, and simple processing technology is one of the key challenges for the next generation of sodium-ion batteries.

[0005] Directly using alloying elements to make foil negative electrodes (such as metal foils such as tin, bismuth, and antimony) as negative electrode active materials, a whole piece of metal foil can undergo alloying reaction with sodium to store sodium, which is a very advanced concept. Since the metal foil itself is a whole, it is equivalent to eliminating the binder and current collector, thereby achieving improved specific energy density, lower cost, higher compaction density, eliminating processing steps such as negative electrode cell mixing and slurrying, and convenient recycling compared to traditional negative electrodes, and has great application prospects. However, the surface load of the foil negative electrode is higher, and it needs to withstand a higher surface current density at the same charge and discharge rate, which poses a great challenge to the conductivity of the foil negative electrode. In particular, for some metals with poor conductivity, such as Sn, the problem of conductivity is particularly serious. Poor metal conductivity will lead to large polarization and low capacity of the foil negative electrode, and the advantages of high capacity and high specific energy density cannot be fully utilized. Currently, there is no effective means to improve the conductivity of foil anodes, which seriously affects the capacity during the cycle. For example, tin foil anodes can only exert about 80% of their theoretical capacity (847 mAh / g) at a very low current density of 0.1 A / g. At the same time, the capacity activation cycle is long, so the practical application of foil anodes is far from over. Therefore, if the interfacial conductivity of foil anodes can be enhanced to bring about stronger overall kinetic performance, so that foil anodes can adapt to higher current densities in practical applications and exert higher specific capacity, it will inevitably further promote the research and application of next-generation sodium-ion battery anode materials.

[0006] Summary of the Invention

[0007] The present invention aims to provide a conductive interface-modified sodium battery alloy foil negative electrode material, its preparation method, and its application. This conductive interface-modified sodium battery alloy foil negative electrode material exhibits high specific capacity and high areal loading. The conductive interface modification effectively increases the current density during cycling. This material is suitable for large-scale commercial production and application.

[0008] To this end, in a first aspect, an embodiment of the present invention provides a conductive interface modified sodium battery alloy foil negative electrode material, the conductive interface modified sodium battery alloy foil negative electrode material comprising: a sodium ion battery alloy foil negative electrode and a conductive modification layer completely attached to the bottom surface of the sodium ion battery alloy foil negative electrode;

[0009] Wherein, the sodium ion battery alloy foil negative electrode is a whole foil material, does not contain a conductive agent or a binder inside, and is attached or not attached to the current collector on the surface;

[0010] The conductive modification layer includes a carbon-based conductive modification layer prepared by a coating process or a metal-based conductive modification layer prepared by a plating process;

[0011] The mass proportion of the conductive material in the conductive interface modified sodium battery alloy foil negative electrode material is less than 50%.

[0012] Preferably, the sodium ion battery alloy foil negative electrode is specifically: a foil made of a metal element, a foil made of an alloy of multiple metal elements, or a foil made of an alloy of one or more metal elements and one or more non-metallic elements;

[0013] The metal elements include: one or more of Sn, Sb, Bi, Ge, and Pb elements; the non-metal elements include: one or more of S, Se, and P elements.

[0014] Preferably, the carbon-based conductive modification layer prepared by the coating process includes: one or more of graphene, MXene, single-walled carbon nanotubes, multi-walled carbon nanotubes, fullerene, carbon black, Ketjen black, graphite, hard carbon, and soft carbon with conductive properties.

[0015] Preferably, the metal-based conductive modification layer prepared by the plating process includes: one element or a combination of several elements selected from the group consisting of silver (Ag), copper (Cu), gold (Au), aluminum (Al), molybdenum (Mo), tungsten (W), zinc (Zn), cobalt (Co), nickel (Ni), iron (Fe), manganese (Mn) and platinum (Pt) with conductive properties.

[0016] In a second aspect, an embodiment of the present invention provides a method for preparing the conductive interface modified sodium battery alloy foil negative electrode material described in the first aspect above, the preparation method comprising: preparing a conductive modification layer on the bottom surface of the sodium ion battery alloy foil negative electrode.

[0017] Preferably, the conductive modification layer prepared on the bottom surface of the sodium ion battery alloy foil negative electrode is: a carbon-based conductive modification layer prepared by a coating process;

[0018] Specifically, the process comprises: mixing a carbon-based conductive material and a binder in a desired mass ratio, uniformly dispersing the mixture with a solvent, forming a film on the surface of the negative electrode of a sodium ion battery alloy foil, drying the dispersed solvent to obtain a carbon-based conductive modified layer on the negative electrode surface of the sodium ion battery alloy foil prepared by an adhesion coating process, and drying the film; the solid content of the carbon-based conductive material accounts for 20% to 95% by weight; the rotation speed for uniformly dispersing the mixture with the solvent is 500 to 3000 rpm, and the dispersion time is 0.2 to 10 hours;

[0019] Among them, the specific process of forming the film on the surface of the negative electrode of the sodium ion battery alloy foil includes: one of: flat film cold roller, flat film cold tank, flat film co-extrusion, blown film or blown film co-extrusion.

[0020] Preferably, the conductive modification layer prepared on the bottom surface of the sodium ion battery alloy foil negative electrode is: a metal-based conductive modification layer prepared by a plating process;

[0021] Specifically, the method includes: subjecting a desired metal-based conductive target material to ion bombardment at a set voltage, evaporation and gasification at a set temperature, or dissolution through an electrochemical oxidation reaction, and depositing a homogeneous coating on the surface of the negative electrode of the sodium ion battery alloy foil, wherein the coating thickness is 10-200 microns; and then drying the conductive modified layer at a temperature of 60-150° C. for 4-16 hours; and the thickness of the conductive modified layer after drying is 0.5-150 microns.

[0022] The specific process of preparing the metal-based conductive modification layer by the plating process includes: vacuum evaporation, sputtering, spraying, ion plating, electroplating, coating, and chemical plating.

[0023] In a third aspect, an embodiment of the present invention provides a sodium ion battery negative electrode, comprising the conductive interface modified sodium battery alloy foil negative electrode material described in the first aspect above.

[0024] In a fourth aspect, an embodiment of the present invention provides a sodium ion battery, comprising the sodium ion battery negative electrode described in the third aspect above.

[0025] In a fifth aspect, an embodiment of the present invention provides an electronic device comprising the sodium ion battery described in the fourth aspect.

[0026] The embodiment of the present invention provides a conductive interface modified sodium battery alloy foil negative electrode material. After being treated by a carbon-based conductive material coating or a metal-based conductive material plating process, the overall conductivity of the foil negative electrode material can be significantly improved without sacrificing the overall specific capacity of the foil negative electrode, thereby ensuring the utilization of capacity under different charge and discharge rates. After a current density of 0.2A / g and above, the specific capacity of the foil negative electrode material after conductive modification is significantly improved compared with the unmodified control sample. The carbon-based conductive material coating or metal-based conductive material plating process adopted by the present invention for the conductive modification of the foil negative electrode material has simple procedures, mature technology, rich choices, low equipment requirements, low overall cost, and is easy to prepare on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic structural diagram of a conductive interface modified sodium battery alloy foil negative electrode material provided by an embodiment of the present invention;

[0028] FIG2 is a surface scanning electron microscope (SEM) image of the material provided in Example 1 of the present invention;

[0029] FIG3 is a charge-discharge curve of the first cycle of the material provided in Example 1 of the present invention;

[0030] FIG4 is a cycle diagram of specific capacity / coulombic efficiency at different rates for the material provided in Example 1 of the present invention;

[0031] FIG5 is a surface SEM image of the material provided in Example 2 of the present invention;

[0032] FIG6 is a charge-discharge curve of the first cycle of the material provided in Example 2 of the present invention;

[0033] FIG7 is a cycle diagram of specific capacity / coulombic efficiency at different rates for the material provided in Example 2 of the present invention;

[0034] FIG8 is a non-magnified camera photo of the material provided in Example 3 of the present invention;

[0035] FIG9 is a cross-sectional SEM image of the material provided in Example 3 of the present invention;

[0036] FIG10 is a charge-discharge curve of the first cycle of the material provided in Example 3 of the present invention;

[0037] FIG11 is a cycle diagram of specific capacity / Coulombic efficiency at different rates for the material provided in Example 3 of the present invention;

[0038] FIG12 is a surface SEM image of the material provided in Example 3 of the present invention after charge and discharge cycles;

[0039] FIG13 is a surface SEM image of the material provided in Example 3 of the present invention after charge and discharge cycles;

[0040] FIG14 is a charge-discharge curve of the first cycle of the material provided in Example 4 of the present invention;

[0041] FIG15 is a graph showing the specific capacity / coulombic efficiency cycle at different rates for the material provided in Example 4 of the present invention;

[0042] FIG16 is a charge-discharge curve of the first cycle of the material provided in Example 5 of the present invention;

[0043] FIG17 is a graph showing the specific capacity / coulombic efficiency cycle at different rates for the material provided in Example 5 of the present invention;

[0044] FIG18 is a charge-discharge curve of the first cycle of the material provided in Example 6 of the present invention;

[0045] FIG19 is a graph showing the specific capacity / coulombic efficiency cycle at different rates for the material provided in Example 6 of the present invention;

[0046] FIG20 is a charge-discharge curve of the first cycle of the material provided in Example 7 of the present invention;

[0047] FIG21 is a SEM image of the material provided in Comparative Example 1 of the present invention;

[0048] FIG22 is a charge-discharge curve of the first week of the material provided in Comparative Example 1 of the present invention;

[0049] FIG23 is a graph showing the specific capacity / coulombic efficiency cycle at different rates for the material provided in Comparative Example 1 of the present invention;

[0050] FIG24 is a first-cycle charge-discharge curve of the material provided in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0052] The embodiment of the present invention provides a conductive interface modified sodium battery alloy foil negative electrode material, the structure of which is shown in FIG1 . The conductive interface modified sodium battery alloy foil negative electrode material comprises: a sodium ion battery alloy foil negative electrode 1 and a conductive modification layer 2 completely attached to the bottom surface of the sodium ion battery alloy foil negative electrode;

[0053] Among them, the sodium ion battery alloy foil negative electrode is a whole foil material, does not contain a conductive agent or a binder inside, and the surface is not attached to the current collector; the sodium ion battery alloy foil negative electrode is specifically: a foil made of a metal element, a foil made of an alloy of multiple metal elements, or a foil made of an alloy of one or more metal elements and one or more non-metallic elements; wherein the metal elements include: one or more of Sn, Sb, Bi, Ge, and Pb elements; the non-metallic elements include one or more of S, Se, and P elements.

[0054] The conductive modification layer includes a carbon-based conductive modification layer prepared by a coating process or a metal-based conductive modification layer prepared by a plating process; the mass proportion of the conductive material in the conductive interface modified sodium battery alloy foil negative electrode material is less than 50%.

[0055] The carbon-based conductive modification layer prepared by the coating process includes: one or more of graphene, MXene, single-walled carbon nanotubes, multi-walled carbon nanotubes, fullerene, carbon black, acetylene black, Ketjen black, graphite, hard carbon, and soft carbon with conductive properties.

[0056] The metal-based conductive modification layer prepared by the plating process includes: one element or a combination of several elements among silver (Ag), copper (Cu), gold (Au), aluminum (Al), molybdenum (Mo), tungsten (W), zinc (Zn), cobalt (Co), nickel (Ni), iron (Fe), manganese (Mn) and platinum (Pt) with conductive properties.

[0057] The conductive interface modified sodium battery alloy foil negative electrode material of the present invention can be obtained by preparing a conductive modification layer on the bottom surface of the sodium ion battery alloy foil negative electrode.

[0058] The specific method can adopt a carbon-based conductive modification layer prepared by a coating process or a metal-based conductive modification layer prepared by a plating process.

[0059] The carbon-based conductive modification layer prepared by the coating process specifically includes: mixing the carbon-based conductive material and the binder according to the required mass ratio, uniformly dispersing them with a solvent, forming a film on the surface of the negative electrode of the sodium ion battery alloy foil, and drying the dispersed solvent to obtain the surface of the negative electrode of the sodium ion battery alloy foil with the carbon-based conductive modification layer prepared by the coating process attached. The thickness of the conductive modification layer formed after drying is 0.5-150 microns.

[0060] The conductive interface-modified sodium battery alloy foil negative electrode material comprises a carbon-based conductive material with a solid content of 20% to 95% by weight. The solvent is uniformly dispersed at a speed of 500 to 3000 rpm for a dispersion time of 0.2 to 10 hours. The specific process for forming the film on the surface of the sodium-ion battery alloy foil negative electrode includes one of flat film cold roll (i.e., casting), flat film cold tank, flat film co-extrusion, blown film, or blown film co-extrusion. The carbon-based conductive material includes one or more of conductive graphene, MXene, single-walled carbon nanotubes, multi-walled carbon nanotubes, fullerenes, carbon black, acetylene black, Ketjen black, graphite, hard carbon, and soft carbon.

[0061] The metal-based conductive modification layer prepared by the coating process specifically includes: subjecting the required metal-based conductive target material to ion bombardment at a voltage of 15V-10KV, or high-temperature evaporation and gasification at 300-2600 degrees Celsius, or electrochemical oxidation reaction dissolution under vacuum conditions of 0.1-15 Pa, to deposit a homogeneous coating on the surface of the negative electrode of the sodium ion battery alloy foil, with a coating thickness of 10-200 microns; then drying at a drying temperature of 60-150 degrees Celsius for 4-16 hours; the thickness of the conductive modification layer after drying is 0.5-150 microns;

[0062] Among them, the specific processes for preparing the metal-based conductive modification layer using the plating process include: vacuum evaporation, sputtering, spraying, ion plating (including any one of hollow cathode ion plating, hot cathode ion plating, arc ion plating, active reaction ion plating, radio frequency ion plating, and DC discharge ion plating), electroplating (water plating or cold plating), coating (brush plating or tankless electroplating), and chemical plating.

[0063] The conductive interface thickness ultimately formed on the surface of the alloy foil negative electrode of the present invention is 0.5-150 microns, and the mass proportion of the conductive material in the alloy foil negative electrode after the conductive interface modification is less than 50%. This can significantly improve the conductivity of the foil negative electrode, enhance the overall dynamic performance of the foil negative electrode, reduce polarization, and promote the use of capacity. For example, the tin foil negative electrode after the interface conductive modification can exert about 98% of the theoretical capacity (theoretical capacity is 847 mAh / g) at 0.1 amps / gram, and can achieve more than 80% of the theoretical capacity (theoretical capacity is 847 mAh / g) at a current density of 0.5 amps / gram, achieving higher rate charge and discharge while ensuring high capacity and high specific energy density. At the same time, it helps dissipate the heat generated by charge and discharge, improving high and low temperature performance.

[0064] The conductive interface-modified sodium battery alloy foil negative electrode material provided by the present invention can be used as the negative electrode of a sodium ion battery. This sodium ion electrode can be used in electronic devices. The conductive interface-modified sodium battery alloy foil negative electrode material of the present invention exhibits a higher mass specific capacity at different current densities than an unmodified alloy foil negative electrode material.

[0065] In order to better understand the technical solution provided by the present invention, the preparation process and characteristics of the conductive interface modified sodium battery alloy foil negative electrode material of the present invention are respectively described below with multiple specific examples.

[0066] Example 1

[0067] 4 grams of carbon black and 6 grams of sodium carboxymethyl cellulose were placed in a ball mill, followed by 300 grams of ball mill beads and 10 milliliters of a 1:1 mixture of deionized water and ethanol. The mixture was stirred at 300 rpm for 1 hour, and the slurry and ball mill beads were separated. The slurry was then coated onto a prepared 10-micron thick tin foil surface using a flat film cold roll process, with an initial thickness of 30 microns. The slurry was then transferred to an oven and dried at 80 degrees Celsius for 6 hours to obtain a tin foil negative electrode material with a conductive surface modification of carbon black. The thickness of the tin foil negative electrode after drying was approximately 12 microns. Figure 2 is a surface scanning electron microscope (SEM) image of the material provided in Example 1 of the present invention. Due to the low density of carbon black and sodium carboxymethyl cellulose, there was almost no significant increase in mass compared to the tin foil negative electrode in the subsequent comparative example 1 that was not surface-conductively modified.

[0068] A button-type half-cell was assembled in an argon glove box using sodium metal as the counter electrode and 1 mol NaPF6-DME (ethylene glycol dimethyl ether) as the electrolyte. A glass fiber separator was used to form a CR2032 button-type battery. Figure 3 shows the first-cycle charge-discharge curve for the material provided in Example 1 of the present invention. The first cycle of charge-discharge cycling at a current density of 0.1 A / g in the 0-1 V voltage range resulted in a reversible specific capacity of 755 mAh / g and a first-cycle coulombic efficiency of 90.16%. Figure 4 is a specific capacity / coulombic efficiency cycle diagram of the material provided in Example 1 of the present invention at different rates. In the voltage range of 0-1 volt, charge and discharge cycles were performed at 0.1 A / g, 0.2 A / g, 0.5 A / g, and 1 A / g for 10 cycles, and finally charge and discharge cycles were performed at a current density of 0.5 A / g to obtain the rate performance data of the tin foil negative electrode material with conductive modification of the carbon black surface, wherein the reversible specific capacity at a current density of 0.2 A / g is 798 mAh / g, the reversible specific capacity at a current density of 0.5 A / g is 675 mAh / g, and the reversible specific capacity at a current density of 1 A / g is 367 mAh / g.

[0069] Example 2

[0070] 3 grams of multi-walled carbon nanotubes and 6 grams of sodium alginate were placed in a ball mill, followed by 270 grams of ball mill beads and 9 milliliters of a 1:1 mixture of deionized water and ethanol. The mixture was stirred at 400 rpm for 1 hour. The slurry and ball mill beads were separated and coated onto a prepared 10-micron thick tin foil surface using a flat film cold roll process to an initial thickness of 40 microns. The slurry was then transferred to an oven and dried at 80 degrees Celsius for 6 hours to obtain a tin foil negative electrode material with a surface conductive modification of the multi-walled carbon nanotubes. The thickness of the tin foil negative electrode after drying was approximately 12 microns. Figure 5 is a surface SEM image of the material provided in Example 2 of the present invention. Due to the low density of multi-walled carbon nanotubes and sodium alginate, the mass of the tin foil negative electrode, which was not surface conductively modified, was almost unchanged compared to the tin foil negative electrode in Comparative Example 1.

[0071] A button-type half-cell was assembled using metallic sodium as the counter electrode and 1 mol NaPF6-DME as the electrolyte. Glass fiber was used as the separator and assembled into a CR2032 button-type battery in an argon glove box. Figure 6 shows the first-week charge-discharge curve of the material provided in Example 2 of the present invention. The first-week charge-discharge cycle at a current density of 0.1 A / g in the 0-1 volt voltage range resulted in a reversible specific capacity of 755 mAh / g and a first-week coulombic efficiency of 89.90%. Figure 7 shows the specific capacity / coulombic efficiency cycle diagram of the material provided in Example 2 of the present invention at different rates. In the 0-1 volt voltage range, 10 charge-discharge cycles were performed at 0.1 A / g, 0.2 A / g, 0.5 A / g, and 1 A / g, respectively. Finally, a charge-discharge cycle was performed at a current density of 0.5 A / g to obtain the rate performance data of the tin foil negative electrode material with surface conductive modification of multi-walled carbon nanotubes.

[0072] Example 3

[0073] 2 grams of single-walled carbon nanotubes and 3 grams of sodium carboxymethyl cellulose were placed in a mixing tank, 5 milliliters of deionized water were added, and the mixture was stirred at 2000 rpm for 20 minutes. The slurry was coated on the surface of the prepared 10-micron thick tin foil through a flat film cold roller process. The initial thickness of the slurry was 50 microns. The slurry was then transferred to an oven and dried at 80 degrees Celsius for 6 hours to obtain a tin foil negative electrode material with surface conductivity modified by single-walled carbon nanotubes. The thickness of the tin foil negative electrode after drying was about 12 microns. Figure 8 is a non-magnified camera photo of the material provided in Example 3 of the present invention, and Figure 9 is a cross-sectional SEM photo of the material provided in Example 3 of the present invention. Since the density of single-walled carbon nanotubes and sodium carboxymethyl cellulose is relatively small, the mass of the tin foil negative electrode that has not been surface-conductively modified is almost not significantly increased compared to that of the comparative example 1.

[0074] Using metallic sodium as the counter electrode and 1 mole of NaPF6-DME as the electrolyte, a button half-cell was assembled, and glass fiber was used as a separator. CR2032 button batteries were assembled in an argon glove box. Figure 10 shows the first-week charge-discharge curve of the material provided in Example 3 of the present invention. The first-week charge-discharge cycle was performed at a current density of 0.1 A / g in the 0-1 volt voltage range. Figure 11 shows the specific capacity / coulombic efficiency cycle diagram at different rates of the material provided in Example 3 of the present invention. In the 0-1 volt voltage range, 10 charge-discharge cycles were performed at 0.1 A / g, 0.2 A / g, 0.5 A / g, and 1 A / g, respectively. Finally, a charge-discharge cycle was performed at a current density of 0.5 A / g to obtain the rate performance data of the tin foil negative electrode material with conductive surface modification of multi-walled carbon nanotubes. Figures 12 and 13 are surface scanning electron microscope (SEM) images of the material after undergoing charge and discharge cycles.

[0075] Example 4

[0076] 4 grams of graphite and 4 grams of sodium alginate were placed in a ball mill, 240 grams of ball mill beads were added, 8 milliliters of a 1:1 mixed solution of deionized water and ethanol were added, and the mixture was stirred at 400 rpm for 1 hour. The slurry and the ball mill beads were separated, and the slurry was coated on the prepared 10-micron thick tin foil surface by a flat film cold roller process. The initial slurry thickness was 30 microns, and then transferred to an oven and dried at 80 degrees Celsius for 6 hours to obtain a tin foil negative electrode material with conductive modification of the graphite surface; the thickness of the tin foil negative electrode after drying was about 12 microns. Due to the low density of graphite and sodium alginate, the mass of the tin foil negative electrode that was not surface-conductively modified was almost not significantly increased compared with that of the comparative example 1.

[0077] A button-type half-cell was assembled using sodium metal as the counter electrode and 1 mol NaPF6-DME as the electrolyte. A glass fiber separator was used in an argon glove box to form a CR2032 button-type battery. Figure 14 shows the first-cycle charge-discharge curves for the material provided in Example 4 of the present invention. The first cycle was performed at a current density of 0.1 A / g in the 0-1 V voltage range. The reversible specific capacity achieved was 757 mAh / g, and the first-cycle coulombic efficiency was 89.76%. Figure 15 is a graph of the specific capacity / coulombic efficiency cycle at different rates for the material provided in Example 4 of the present invention. In the 0-1 volt voltage range, 10 charge-discharge cycles were performed at 0.1 amps / g, 0.2 amps / g, 0.5 amps / g, and 1 amp / g, respectively. Finally, a charge-discharge cycle was performed at a current density of 0.5 amps / g, and the rate performance data of the tin foil negative electrode material with conductive surface modification of multi-walled carbon nanotubes was obtained. The reversible specific capacity at a current density of 0.2 amps / g was 790 mAh / g, the reversible specific capacity at a current density of 0.5 amps / g was 698 mAh / g, and the reversible specific capacity at a current density of 1 amp / g was 460 mAh / g. Example 5

[0078] The surface of the prepared 10 micron thick tin foil is subjected to the surface gold plating conductive modification by the spraying process, and the vacuum is drawn to 10 -5 After MPa, gold foil was selected and sprayed with a current of 0.5 mA for 100 seconds, transferred to an oven, and dried at 80 degrees Celsius for 2 hours to obtain a tin foil negative electrode material with a gold-plated surface conductively modified; since the surface sprayed layer was extremely thin, the thickness and mass of the tin foil negative electrode after drying were almost not significantly increased compared with the tin foil negative electrode in comparative example 1 that was not subjected to surface conductive modification.

[0079] A button-type half-cell was assembled using sodium metal as the counter electrode and 1 mol NaPF6-DME as the electrolyte. A glass fiber separator was used in an argon glove box to form a CR2032 button-type battery. Figure 16 shows the first-cycle charge-discharge curves for the material provided in Example 5 of the present invention. The first cycle of charge-discharge cycling at a current density of 0.1 A / g in the 0-1 V voltage range yielded a reversible specific capacity of 766 mAh / g and a first-cycle coulombic efficiency of 90.10%. Figure 17 is a specific capacity / coulombic efficiency cycle diagram at different rates for the material provided in Example 5 of the present invention. In the voltage range of 0-1 volt, charge and discharge cycles were performed at 0.1 A / g, 0.2 A / g, 0.5 A / g, and 1 A / g for 10 cycles, and finally charge and discharge cycles were performed at a current density of 0.5 A / g to obtain rate performance data of a tin foil negative electrode material with a thin spray-coated gold-plated surface conductive modification. The reversible specific capacity at a current density of 0.2 A / g is 810 mAh / g, the reversible specific capacity at a current density of 0.5 A / g is 737 mAh / g, and the reversible specific capacity at a current density of 1 A / g is 518 mAh / g.

[0080] Example 6

[0081] The surface of the prepared 10 micron thick tin foil is subjected to the surface gold plating conductive modification by the spraying process, and the vacuum is drawn to 10 -5 After MPa, gold foil was selected and sprayed with a current of 0.5 mA for 300 seconds, transferred to an oven, and dried at 80 degrees Celsius for 2 hours to obtain a tin foil negative electrode material with a gold-plated surface conductively modified; since the surface sprayed layer was extremely thin, the thickness and mass of the tin foil negative electrode after drying were almost not significantly increased compared with the tin foil negative electrode in comparative example 1 that was not subjected to surface conductive modification.

[0082] A button-type half-cell was assembled using sodium metal as the counter electrode and 1 mol NaPF6-DME as the electrolyte. A glass fiber separator was used in an argon glove box to form a CR2032 button-type battery. Figure 18 shows the first-cycle charge-discharge curves for the material provided in Example 6 of the present invention. The first cycle of charge-discharge cycling at a current density of 0.1 A / g in the 0-1 V voltage range yielded a reversible specific capacity of 766 mAh / g and a first-cycle coulombic efficiency of 90.28%. Figure 19 is a specific capacity / coulombic efficiency cycle diagram at different rates for the material provided in Example 6 of the present invention. In the voltage range of 0-1 volt, 10 charge and discharge cycles were performed at 0.1 A / g, 0.2 A / g, 0.5 A / g, and 1 A / g, respectively. Finally, a charge and discharge cycle was performed at a current density of 0.5 A / g to obtain rate performance data of a tin foil negative electrode material with a thick spray-coated gold-plated surface conductive modification. The reversible specific capacity at a current density of 0.2 A / g is 812 mAh / g, the reversible specific capacity at a current density of 0.5 A / g is 743 mAh / g, and the reversible specific capacity at a current density of 1 A / g is 555 mAh / g.

[0083] Example 7

[0084] 2 grams of single-walled carbon nanotubes and 3 grams of sodium carboxymethyl cellulose were placed in a mixing tank, 6 milliliters of deionized water were added, and the mixture was stirred at 2000 rpm for 20 minutes. The slurry was coated on the surface of a prepared 15-micron thick lead foil by a flat film cold roller process. The initial thickness of the slurry was 60 microns. The slurry was then transferred to an oven and dried at 80 degrees Celsius for 6 hours to obtain a lead foil negative electrode material with surface conductive modification of single-walled carbon nanotubes. The thickness of the lead foil negative electrode after drying was about 17 microns. Due to the low density of single-walled carbon nanotubes and sodium carboxymethyl cellulose, there was almost no significant increase in the mass of the lead foil negative electrode in comparative example 3 that was not surface conductively modified.

[0085] A button-type half-cell was assembled using sodium metal as the counter electrode and 1 mol NaPF6-DME as the electrolyte. A glass fiber separator was used in an argon glove box to form a CR2032 button-type battery. Figure 20 shows the first-cycle charge-discharge curve for the material provided in Example 7 of the present invention. The first cycle of charge-discharge cycling at a current density of 0.1 A / g in the 0-1 V voltage range resulted in a reversible specific capacity of 470 mAh / g and a first-cycle coulombic efficiency of 85.79%.

[0086] Comparative Example 1

[0087] The surface of the prepared 10-micron thick tin foil was wiped with anhydrous ethanol to remove impurities attached to the surface, then transferred to an oven and dried at 80 degrees Celsius for 6 hours to obtain a tin foil negative electrode without surface modification. Figure 21 is a surface SEM image of the material provided in Comparative Example 1 of the present invention;

[0088] A button-type half-cell was assembled using metallic sodium as the counter electrode and 1 mol NaPF6-DME as the electrolyte. Glass fiber was used as the separator and assembled into a CR2032 button-type battery in an argon glove box. Figure 22 shows the charge-discharge curve of the material provided in Comparative Example 1 of the present invention in the first week. The first week of charge-discharge cycles were performed at a current density of 0.1 A / g in the 0-1 volt voltage range. Figure 22 shows the charge-discharge curve of the material provided in Comparative Example 1 of the present invention. The reversible specific capacity was 736 mAh / g, and the first week coulombic efficiency was 87.31%. Figure 23 shows the specific capacity / coulombic efficiency cycle diagram of the material provided in Comparative Example 1 of the present invention at different rates. In the 0-1 volt voltage range, 10 charge-discharge cycles were performed at 0.1 A / g, 0.2 A / g, 0.5 A / g, 1 A / g, and 2 A / g, respectively. Finally, a charge-discharge cycle was performed at a current density of 1 A / g to obtain the rate performance data of the tin foil negative electrode material without surface conductive modification. The reversible specific capacity at a current density of 0.2 A / g is 767 mAh / g, the reversible specific capacity at a current density of 0.5 A / g is 449 mAh / g, the reversible specific capacity at a current density of 1 A / g is 178 mAh / g, and the reversible specific capacity at a current density of 2 A / g is 20 mAh / g.

[0089] Comparative Example 2

[0090] The surface of the prepared 15-micron thick lead foil was wiped with anhydrous ethanol to remove impurities attached to the surface, transferred to an oven, and dried at 80 degrees Celsius for 6 hours to obtain a lead foil negative electrode without surface modification.

[0091] A button-type half-cell was assembled using sodium metal as the counter electrode and 1 mol NaPF6-DME as the electrolyte. A glass fiber separator was used in an argon glove box to form a CR2032 button-type battery. Figure 24 shows the first-cycle charge-discharge curve for the material provided in Comparative Example 2 of the present invention. The first cycle was performed at a current density of 0.1 A / g in the 0-1 V voltage range. Figure 24 shows the charge-discharge curve for the material provided in Comparative Example 3 of the present invention. A reversible specific capacity of 445 mAh / g was achieved, and the first-cycle coulombic efficiency was 81.51%.

[0092] In Table 1 below, for the examples using a flat-film cold roll process for conductive interface modification, 2 grams of conductive interface modification material and 3 grams of sodium carboxymethyl cellulose were used for slurry preparation. 5 milliliters of deionized water were added and mixed at 2000 rpm for 30 minutes. The resulting slurry was then coated on the foil surface using a flat-film cold roll process. All electrochemical performance tests for the comparative examples and examples in the table below were performed using sodium metal as the counter electrode, 1 mol NaPF6-DME as the electrolyte, and CR2032 button-type cells assembled in an argon glove box using a glass fiber separator. These tests were conducted at a current density of 0.5 A / g in the 0-1 V voltage range at room temperature.

[0093] Table 1

[0094] The embodiment of the present invention provides a conductive interface modified sodium battery alloy foil negative electrode material. After being treated by a carbon-based conductive material coating or a metal-based conductive material plating process, the overall conductivity of the foil negative electrode material can be significantly improved without sacrificing the overall specific capacity of the foil negative electrode, thereby ensuring the utilization of capacity under different charge and discharge rates. After a current density of 0.2A / g and above, the specific capacity of the foil negative electrode material after conductive modification is significantly improved compared with the unmodified control sample. The carbon-based conductive material coating or metal-based conductive material plating process adopted by the present invention for the conductive modification of the foil negative electrode material has simple procedures, mature technology, rich choices, low equipment requirements, low overall cost, and is easy to prepare on a large scale.

[0095] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A conductive interface modified sodium battery alloy foil negative electrode material, characterized in that: The conductive interface modified sodium battery alloy foil negative electrode material comprises: a sodium ion battery alloy foil negative electrode and a conductive modification layer completely attached to the bottom surface of the sodium ion battery alloy foil negative electrode; Wherein, the sodium ion battery alloy foil negative electrode is a foil material as a whole, does not contain a conductive agent or a binder inside, and is attached or not attached to a current collector on the surface; The conductive modification layer includes a carbon-based conductive modification layer prepared by a coating process or a metal-based conductive modification layer prepared by a plating process; The mass proportion of the conductive material in the conductive interface modified sodium battery alloy foil negative electrode material is less than 50%.

2. The conductive interface modified sodium battery alloy foil negative electrode material according to claim 1, characterized in that: The sodium ion battery alloy foil negative electrode is specifically: a foil made of a metal element, a foil made of an alloy of multiple metal elements, or a foil made of an alloy of one or more metal elements and one or more non-metallic elements; The metal elements include: one or more of Sn, Sb, Bi, Ge, and Pb elements; the non-metal elements include: one or more of S, Se, and P elements.

3. The conductive interface modified sodium battery alloy foil negative electrode material according to claim 1, characterized in that: The carbon-based conductive modification layer prepared by the coating process includes: one or more of graphene, MXene, single-walled carbon nanotubes, multi-walled carbon nanotubes, fullerene, carbon black, Ketjen black, graphite, hard carbon, and soft carbon with conductive properties.

4. The conductive interface modified sodium battery alloy foil negative electrode material according to claim 1, characterized in that: The metal-based conductive modification layer prepared by the plating process includes: one element or a combination of several elements selected from the group consisting of silver (Ag), copper (Cu), gold (Au), aluminum (Al), molybdenum (Mo), tungsten (W), zinc (Zn), cobalt (Co), nickel (Ni), iron (Fe), manganese (Mn) and platinum (Pt) having conductive properties.

5. A method for preparing the conductive interface modified sodium battery alloy foil negative electrode material according to any one of claims 1 to 4, characterized in that: The preparation method comprises: preparing a conductive modification layer on the bottom surface of a negative electrode of a sodium ion battery alloy foil.

6. The preparation method according to claim 5, characterized in that: The conductive modification layer prepared on the bottom surface of the negative electrode of the alloy foil of the sodium ion battery is: a carbon-based conductive modification layer prepared by a coating process; Specifically, the method comprises: mixing a carbon-based conductive material and a binder according to a required mass ratio, uniformly dispersing the carbon-based conductive material with a solvent, forming a film on the negative electrode surface of a sodium ion battery alloy foil, and drying the dispersed solvent to obtain a surface of a negative electrode of a sodium ion battery alloy foil with a carbon-based conductive modified layer prepared by an attachment coating process and drying the surface; the solid content of the carbon-based conductive material accounts for 20% to 95% by weight; the rotation speed for uniformly dispersing the carbon-based conductive material with a solvent is 500 to 3000 rpm, and the dispersion time is 0.2 to 10 hours; Among them, the specific process of forming the film on the surface of the negative electrode of the sodium ion battery alloy foil includes: one of: flat film cold roller, flat film cold tank, flat film co-extrusion, blown film or blown film co-extrusion.

7. The preparation method according to claim 5, characterized in that: The conductive modification layer prepared on the bottom surface of the negative electrode of the alloy foil of the sodium ion battery is: a metal-based conductive modification layer prepared by a coating process; specifically comprising: subjecting the required metal-based conductive target material to ion bombardment at a set voltage or evaporation and gasification at a set temperature or dissolution through an electrochemical oxidation reaction, and depositing a homogeneous coating on the surface of the negative electrode of the alloy foil of the sodium ion battery, wherein the coating thickness is 10-200 microns; and then drying, the drying temperature is 60-150° C., and the drying time is 4-16 hours; the thickness of the conductive modification layer after drying is 0.5-150 microns; The specific process of preparing the metal-based conductive modification layer by the plating process includes: one of vacuum evaporation, sputtering, spraying, ion plating, electroplating, coating and chemical plating.

8. A sodium ion battery negative electrode, characterized in that: The sodium ion battery negative electrode comprises the conductive interface modified sodium battery alloy foil negative electrode material as described in any one of claims 1 to 4 above.

9. A sodium ion battery, characterized in that: The sodium ion battery comprises the sodium ion battery negative electrode as described in claim 8 above.

10. An electronic device, characterized in that: The electronic device comprises the sodium ion battery according to claim 9.

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