Three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheets, their preparation methods, and their applications in sodium metal batteries
By growing Bi2O3 nanosheets on three-dimensional carbon cloth fibers and then heat-treating them to form Bi nanoparticles, a three-dimensional hierarchical Na/Na3Bi/CC composite sodium metal sheet was prepared. This solved the problems of uneven deposition and dendrite growth of sodium metal anodes, and improved the stability and performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHWEST UNIV
- Filing Date
- 2024-07-09
- Publication Date
- 2026-06-30
AI Technical Summary
Sodium metal anodes suffer from uneven deposition, sodium dendrite growth, unstable SEI film, and severe volume expansion during cyclic charging and discharging, resulting in poor battery cycle stability and even potential safety hazards.
A three-dimensional hierarchical Na/Na3Bi/CC composite sodium sheet was prepared by growing Bi2O3 nanosheets on three-dimensional carbon cloth fibers and heat-treating them to form Bi nanoparticles, thus creating a highly sodium-affinity buffer modification layer. The three-dimensional hierarchical Na/Na3Bi/CC composite sodium sheet was then prepared using a melt infiltration method, achieving uniform distribution and adsorption of metallic sodium.
It improves the wetting and uniform distribution of metallic sodium on the three-dimensional current collector, buffers the deformation and stress during the sodium deposition/stripping process, inhibits sodium dendrite growth, optimizes the electrode interface reaction process, and improves the rate performance and cycle life of the battery.
Smart Images
Figure CN118867143B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of sodium metal battery technology, and relates to a three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet, its preparation method, and its application in sodium metal batteries. Background Technology
[0002] Sodium metal anodes possess numerous advantages, including high specific capacity (1165 mAh / g), low redox potential (-2.71 V vs. SHE), low cost, and abundant raw materials, making them promising candidates for high-energy-density energy storage. However, highly reactive sodium metal still faces many challenges during charge-discharge cycles, such as uneven sodium deposition, severe sodium dendrite growth, unstable SEI film, and dramatic volume expansion. These issues lead to poor battery cycle stability, low coulombic efficiency, and even safety accidents such as dendrites piercing the separator and causing explosions, significantly limiting the practical application and development of sodium metal batteries.
[0003] Among numerous strategies for modifying sodium metal anodes, loading metallic sodium onto a three-dimensional current collector substrate is considered an effective approach. The three-dimensional substrate allows for the control of a uniform spatial current density distribution, mitigating sodium dendrite growth, and effectively buffering the volumetric stress during sodium deposition / stripping, thus improving electrode stability. Carbon cloth fiber is a commonly used three-dimensional current collector substrate, possessing advantages such as high conductivity, strong mechanical stability, light weight, and low cost; however, pure carbon cloth fiber lacks sodium affinity, making it difficult to adsorb molten metallic sodium. Summary of the Invention
[0004] Therefore, the purpose of this invention is to provide a three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet, its preparation method, and its application in sodium metal batteries. This three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet achieves sufficient wetting and uniform distribution of sodium metal on a three-dimensional carbon cloth substrate.
[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:
[0006] This invention provides a method for preparing a three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet, comprising the following steps:
[0007] (1) Carbon fabric Bi2O3 / CC with Bi2O3 nanosheet array was grown in a mixed solution of ethanol, ethylene glycol and bismuth nitrate pentahydrate and subjected to a solvothermal reaction.
[0008] (2) The Bi2O3 / CC obtained in step (1) is heat-treated and cooled to obtain a three-dimensional carbon cloth substrate Bi2O3 / Bi / CC with Bi2O3 / Bi nanoparticles grown on it.
[0009] (3) Heat the sodium metal to a molten state, and then contact the molten sodium with the three-dimensional carbon cloth substrate Bi2O3 / Bi / CC obtained in step (2). Sodium is completely adsorbed onto the surface and interior of the substrate to obtain a three-dimensional layered Na / Na3Bi / CC composite sodium metal sheet.
[0010] As a preferred technical solution, in step (1), the thickness of the carbon cloth is 360μm and the diameter of a single carbon fiber is 10μm.
[0011] As a preferred technical solution, in the mixed solution of step (1), the volume ratio of ethanol to ethylene glycol is 1-5:1, and the content of bismuth nitrate pentahydrate is 0.03-0.1M.
[0012] As a preferred technical solution, the conditions for the solvothermal reaction in step (1) are: reaction temperature 140-200℃, reaction time 3-8 hours.
[0013] As a preferred technical solution, the heat treatment conditions in step (2) are: Ar atmosphere, heating rate 5-15℃ / min, heat treatment temperature 300-600℃, and holding time 1-4 hours.
[0014] As a preferred technical solution, in step (3), the loading of metallic sodium on the three-dimensional carbon cloth substrate Bi2O3 / Bi / CC is 10-40 mg / cm³. 2 .
[0015] The present invention also provides a three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet prepared by the above preparation method.
[0016] The present invention also provides a sodium metal symmetric battery, wherein the sodium metal symmetric battery is assembled using the three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet as the positive and negative electrodes of the battery.
[0017] The present invention also provides a sodium metal full cell, wherein the sodium metal full cell is assembled using the three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet as the negative electrode.
[0018] The beneficial effects of this invention are as follows:
[0019] This invention constructs a highly sodium-affinity three-dimensional conductive substrate by uniformly growing Bi₂O₃ / Bi particles on three-dimensional carbon cloth fibers, and prepares a three-dimensional hierarchical Na / Na₃Bi / CC composite sodium metal sheet through molten sodium infiltration. The sodium-affinity Bi₂O₃ / Bi nanoparticles are uniformly dispersed on the carbon cloth fibers. When they come into contact with molten sodium, an alloying reaction easily occurs to form a Na₃Bi buffer modification layer. This buffer layer significantly reduces the sodium nucleation energy barrier, effectively improving the affinity and adsorption of the three-dimensional substrate with sodium metal, allowing the molten sodium metal to be fully wetted and uniformly distributed within the three-dimensional framework. The sufficient wetting and uniform distribution of sodium metal on the three-dimensional carbon cloth substrate increases the sodium loading in the three-dimensional current collector substrate. An appropriate loading can buffer deformation and stress during sodium deposition / stripping, reduce electrode interface impedance, effectively inhibit sodium dendrite growth, optimize the interface reaction process, and improve the rate performance and cycle life of the battery. Attached Figure Description
[0020] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:
[0021] Figure 1 The image shows a scanning electron microscope (SEM) image of the three-dimensional Bi2O3 / CC structure and the Bi2O3 / Bi / CC substrate.
[0022] Figure 2 X-ray diffraction (XRD) pattern of Na / Na3Bi / CC composite sodium metal sheet;
[0023] Figure 3 This is a comparison of the cycle performance of composite sodium metal sheets and pure sodium metal sheets in a symmetrical battery system.
[0024] Figure 4 This is a comparison chart of the rate performance of composite sodium metal sheets and pure sodium metal sheets in a symmetrical battery system.
[0025] Figure 5 The graph shows a comparison of the rate performance of composite sodium metal sheets and pure sodium metal sheets in a full battery system.
[0026] Figure 6 This is a cycle performance comparison diagram of composite sodium metal sheets and pure sodium metal sheets in a full battery system. Detailed Implementation
[0027] The preferred embodiments of the present invention will now be described in detail with reference to the examples. The described embodiments are only a part of the embodiments of the present invention, and not all of them. The scope of the present invention should not be construed as limited to the embodiments described below. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0028] 1. Preparation of Na / Na3Bi / CC composite sodium metal sheets:
[0029] (1) A hydrophilic CC substrate with a thickness of 360 μm and a single carbon fiber diameter of about 10 μm was placed in a mixed solution of bismuth nitrate pentahydrate, ethanol and ethylene glycol, wherein the volume ratio of ethanol to ethylene glycol was 3:1 and the mass content of bismuth nitrate pentahydrate was 0.05M. A polytetrafluoroethylene reactor was used as the reaction vessel, and a solvothermal reaction was carried out at a constant temperature of 160℃ for 5 hours in an electric oven to obtain a carbon cloth structure (Bi2O3 / CC) with bismuth oxide nanosheet arrays. The substrate was washed with deionized water and dried in an electric oven at 60℃ for later use.
[0030] SEM images of the Bi2O3 / CC structure are shown below. Figure 1 As shown in Figure a, the Bi2O3 generated by the solvothermal reaction is in the form of nanosheets, and the interwoven nanosheets grow uniformly on the carbon cloth fiber in a porous array.
[0031] (2) The above Bi2O3 / CC was placed in a tube furnace and calcined at 500°C for 2 hours in an Ar atmosphere. The heating rate was 10°C / min. After natural cooling, the highly sodium-loving Bi2O3 / Bi / CC substrate was obtained. At this time, the Bi2O3 nanosheets were partially reduced to form Bi / Bi2O3 composite nanoparticles, which were uniformly anchored on the carbon fiber.
[0032] SEM images of the Bi2O3 / Bi / CC substrate are shown below. Figure 1 As shown in b, after heat treatment, the Bi2O3 nanosheet array is partially reduced and generated into nanoparticles. These nanoparticles are uniformly and densely embedded on the carbon cloth fiber, and their particle size distribution is 50-300 nm.
[0033] (3) Take 20 mg of metallic sodium, heat it to 200 °C to melt it, and take the above Bi2O3 / Bi / CC substrate (area 1 cm²) 2 The molten sodium is brought into contact with the substrate, and the molten sodium is fully wetted and completely adsorbed onto the substrate. The resulting composite electrode is then cooled to obtain a three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet.
[0034] The SEM image of the composite sodium metal sheet is as follows: Figure 2 As shown in Figure a, metallic sodium is uniformly coated on carbon cloth fibers, exhibiting a porous granular surface without obvious bulk accumulation, demonstrating the successful composite of metallic sodium and carbon cloth fibers. Its XRD image is shown below. Figure 2As shown in b, the diffraction peaks mainly correspond to alloy Na3Bi (JCPDS card number: 74-1161) and metallic Na (JCPDS card number: 22-0948), proving that metallic sodium forms a Na3Bi buffer modification layer during the recombination process with the sodium-loving Bi2O3 / Bi / CC substrate.
[0035] 2. Assembly and electrochemical performance testing of sodium metal symmetric batteries:
[0036] Sodium metal symmetric cells were assembled using Na / Na3Bi / CC composite sodium metal electrodes, polypropylene membranes, and 1M NaClO4 / EC+DEC (V%, 1:1, 5% FEC) electrolyte. For comparison, a sodium metal symmetric cell was assembled using pure sodium metal electrodes under the same conditions. The electrochemical performance of both symmetric cells was tested at room temperature at a current density of 1 mA / cm². 2 The surface area capacity is 1mAh / cm². 2 Its stability was tested under cyclic charge-discharge conditions; at 1mAh / cm 2 At the area capacity, with 1, 2, 5 and 10 mA / cm² 2 The current density was used for charging and discharging to test its rate performance.
[0037] Cyclic performance test results are as follows Figure 3 As shown, the polarization overpotential of the composite sodium metal sheet symmetric cell stabilized at 15 mV, and the voltage curve remained stable over 2500 h of cycling without significant voltage plateau fluctuations. In contrast, the initial overpotential of the pure sodium metal sheet symmetric cell exceeded 80 mV, and the voltage curve became extremely unstable with large overpotential fluctuations as the reaction continued, eventually leading to a short circuit after 80 cycles. This result demonstrates that the cycling stability of the composite sodium metal sheet is significantly improved.
[0038] The results of the rate performance test are as follows: Figure 4 As shown, compared with pure sodium metal sheet symmetrical cells, composite sodium metal sheet symmetrical cells exhibit smaller polarization voltages and more stable charge-discharge curves under various test current densities. This result proves that the reaction kinetics and rate performance of composite sodium metal sheets are significantly improved.
[0039] 3. Assembly and electrochemical performance testing of sodium metal full cells:
[0040] Sodium metal full cells were assembled using a Na / Na3Bi / CC composite sodium metal sheet as the negative electrode, sodium vanadium phosphate as the positive electrode, polypropylene as the separator, and 1M NaClO4 / EC+DEC (V%, 1:1, 5% FEC) as the electrolyte. For comparison, sodium metal full cells were assembled using a pure sodium metal sheet as the negative electrode, with other conditions unchanged. The electrochemical performance of the two sodium metal full cells was tested at room temperature: their rate performance was tested by charge-discharge at current densities ranging from 1C to 10C; their stability was tested by cyclic charge-discharge at a current density of 1C.
[0041] The results of the rate performance test are as follows: Figure 5 As shown, compared to full cells assembled from pure sodium metal sheets, the specific capacity of the composite sodium metal full cell system is significantly improved at charge-discharge rates of 1C-10C, demonstrating that the composite sodium metal system possesses superior electrochemical reaction kinetics. Cycling performance comparison is as follows: Figure 6 As shown, after 500 cycles, the specific capacity retention rate of the composite sodium metal battery system is as high as 91%, and its coulombic efficiency remains stable above 99%. In contrast, the specific capacity of the pure sodium metal battery system decreases significantly and fluctuates drastically after 100 cycles, with a capacity retention rate of only about 60% after 500 cycles, and the coulombic efficiency also fluctuates greatly. This comparison demonstrates that the stability of the composite sodium metal sheet full cell has been effectively improved.
[0042] The above embodiments are only used to illustrate preferred embodiments of the present invention, and are not intended to limit the concept and scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the concept and principles of this application should be included within the scope of protection of this application.
Claims
1. A method for preparing a three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet, characterized in that: Includes the following steps: (1) Carbon fabric Bi2O3 / CC with Bi2O3 nanosheet array was grown in a mixed solution of ethanol, ethylene glycol and bismuth nitrate pentahydrate and subjected to a solvothermal reaction. (2) The Bi2O3 / CC obtained in step (1) is heat-treated and cooled to obtain a three-dimensional carbon cloth substrate Bi2O3 / Bi / CC with Bi2O3 / Bi nanoparticles grown on it. (3) Heat the sodium metal to a molten state, and then contact the molten sodium with the three-dimensional carbon cloth substrate Bi2O3 / Bi / CC obtained in step (2). Sodium is completely adsorbed onto the surface and interior of the substrate to obtain a three-dimensional layered Na / Na3Bi / CC composite sodium metal sheet.
2. The preparation method according to claim 1, characterized in that: In step (1), the thickness of the carbon cloth is 360 μm and the diameter of a single carbon fiber is 10 μm.
3. The preparation method according to claim 1, characterized in that: In the mixed solution of step (1), the volume ratio of ethanol to ethylene glycol is 1-5:1, and the content of bismuth nitrate pentahydrate is 0.03-0.1M.
4. The preparation method according to claim 1, characterized in that: The conditions for the solvothermal reaction in step (1) are: reaction temperature 140-200℃, reaction time 3-8 hours.
5. The preparation method according to claim 1, characterized in that: The heat treatment conditions in step (2) are: Ar atmosphere, heating rate 5-15℃ / min, heat treatment temperature 300-600℃, and holding time 1-4 hours.
6. The preparation method according to claim 1, characterized in that: In step (3), the loading of metallic sodium on the three-dimensional carbon cloth substrate Bi2O3 / Bi / CC is 10-40 mg / cm³. 2 .
7. The three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet prepared by the preparation method according to any one of claims 1 to 6.
8. A sodium metal symmetric battery, characterized in that: A sodium metal symmetric battery is assembled using the three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet as described in claim 7 as the positive and negative electrodes.
9. A sodium metal full battery, characterized in that: A sodium metal full cell is assembled using the three-dimensional hierarchical Na / Na3Bi / CC composite sodium metal sheet as described in claim 7 as the negative electrode.