Potassium-ion battery negative electrode, potassium-ion battery and preparation method and application thereof

Abstract

This invention relates to the field of secondary battery chemical energy storage technology, and particularly to a potassium-ion battery anode, a potassium-ion battery, its preparation method, and its applications. The invention includes the following steps: providing a bismuth-tin metal-organic framework precursor; mixing the bismuth-tin metal-organic framework precursor with a carbon source to obtain a composite precursor; and calcining the composite precursor under an inert atmosphere to induce a carbothermic reduction reaction, yielding a bismuth-tin dimer with a phase-separated structure, which is then coated with carbon to form a potassium-ion battery anode material. The anode material prepared by this invention can be widely used in high-performance potassium-ion batteries, especially suitable for large-scale energy storage, portable electronic devices, electric vehicles, and other fields, meeting the application requirements of different scenarios and possessing strong practicality and broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of secondary battery chemical energy storage technology, and in particular to a potassium-ion battery anode, a potassium-ion battery, its preparation method and application. Background Technology

[0002] With the rapid development of the new energy industry, lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, and other fields. However, the limited and uneven distribution of lithium resources has resulted in high costs for lithium-ion batteries, making it difficult to meet the needs of large-scale energy storage. Potassium-ion batteries, on the other hand, benefit from abundant and widely distributed potassium resources, low cost, and a potassium ion radius similar to that of lithium ions, exhibiting a similar electrochemical working principle. Therefore, they have become one of the most promising alternative technologies for large-scale energy storage.

[0003] Anode materials are one of the core components determining the electrochemical performance of potassium-ion batteries. Currently reported potassium-ion battery anode materials mainly include carbon-based materials, alloy materials, and metal compounds. Among them, bismuth (Bi) and tin (Sn), as typical alloy anode materials, have high theoretical potassium storage capacity (Bi: 385 mAh / g, Sn: 847 mAh / g), and are abundant and inexpensive, attracting widespread attention. However, Bi and Sn undergo drastic volume expansion during potassium intercalation (Bi: 259%, Sn: 360%), leading to particle agglomeration and structural collapse, which in turn causes a sharp decline in battery cycle stability. At the same time, the large radius of potassium ions (1.38 Å) results in a slow diffusion rate in Bi and Sn, leading to poor rate performance of the materials. These problems severely limit their practical application.

[0004] To address these issues, researchers typically employ modification strategies such as carbon coating, nanostructuring, and bimetallic composites. Among these, the bimetallic composite strategy, through the synergistic effect of two metals, can effectively mitigate the volume expansion of a single metal while simultaneously enhancing the potassium ion diffusion rate. However, the preparation of existing bimetallic bismuth-tin composite anode materials often involves simple physical mixing, making it difficult to form a stable and clear phase interface and fully leverage the synergistic effect of the bimetals. Furthermore, the lack of precise synergistic control over the various preparation parameters results in uneven material morphology and poor structural stability, failing to achieve a balance between high capacity and long cycling performance.

[0005] In the prior art, CN113839038A discloses a method for preparing MOF-derived bismuth@carbon nanocomposites. This method involves preparing a MOF precursor through a solvothermal reaction of bismuth salt and ligands, followed by calcination in an inert atmosphere to obtain the Bi@C composite material. While this method is simple, it can only prepare single-metal bismuth-carbon composites, failing to utilize the synergistic effect of bimetals. Furthermore, the material morphology and structure are difficult to control precisely, and the cycling stability still needs improvement. In addition, the preparation of existing bimetallic bismuth-tin-carbon composites does not involve synergistic regulation of MOF precursor preparation parameters, carbon coating ratio, calcination process, and the Bi / Sn molar ratio. This makes it difficult to form a stable and clear phase interface, hindering efficient potassium ion transport and preventing the formation of a controllable "relay diffusion" potassium storage mechanism. Consequently, the volume expansion mitigation effect is limited, failing to fully leverage the synergistic advantages of bimetals and carbon coating. This is the core technical bottleneck in existing bimetallic alloy anodes, which struggle to achieve both high capacity and long cycling performance. Summary of the Invention

[0006] To address the problems mentioned in the background section, this invention provides a potassium-ion battery anode, a potassium-ion battery, a method for preparing the same, and its applications.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention discloses a method for preparing a potassium-ion battery anode, which specifically includes the following steps: First, a bismuth-tin metal-organic framework precursor is provided; then, the bismuth-tin metal-organic framework precursor is mixed with a carbon source to obtain a composite precursor. The mixing process is carried out at room temperature with a stirring rate of 300-500 r / min and a stirring time of 1-2 h to ensure that the two are mixed uniformly without obvious agglomeration; then, the composite precursor is calcined under an inert atmosphere to cause the bismuth-tin metal-organic framework precursor to undergo a carbothermic reduction reaction, resulting in a bismuth-tin dimer with a phase-separated structure, which is then coated with carbon to form a potassium-ion battery anode material. The calcination process adopts a programmed temperature rise method with a heating rate of 5-10 °C / min, from room temperature to the calcination temperature, and after calcination, it is naturally cooled to room temperature to obtain the anode material.

[0008] The aforementioned bismuth-tin metal-organic framework precursor was prepared by the following method: bismuth and tin sources were dissolved in an organic solvent, mixed with an organic ligand, and then subjected to a solvothermal reaction to obtain the bismuth-tin metal-organic framework precursor. The bismuth source included at least one of bismuth nitrate, bismuth chloride, and bismuth acetate; the tin source included at least one of stannous chloride, tin nitrate, and tin acetate; the solvothermal reaction temperature was 120-180℃, and the reaction time was 12-24 h. After the reaction, the precursor was centrifuged, washed, and vacuum dried to obtain the bismuth-tin metal-organic framework precursor. The vacuum drying temperature was 60-80℃, and the drying time was 8-12 h.

[0009] In the preparation of the bismuth-tin metal-organic framework precursor, the molar ratio of the bismuth source to the tin source is (1-4):(1-2), the organic ligand includes 1,3,5-benzenetricarboxylic acid, and the organic solvent includes a mixed solvent of methanol and N,N-dimethylformamide, with a volume ratio of methanol:N,N-dimethylformamide = 4:1. The total molar ratio of the organic ligand to the bismuth and tin sources is (1-3):1. The washing process uses alternating washing with methanol and deionized water, with each washing lasting 5-10 minutes and repeated 3-5 times.

[0010] In the preparation process of the negative electrode of a potassium-ion battery, the carbon source includes polyvinylpyrrolidone; the mass ratio of the bismuth-tin metal-organic framework precursor to the carbon source is 1:(1-3). The molecular weight of the polyvinylpyrrolidone is 10,000-50,000, and an appropriate amount of deionized water can be added as a dispersion medium during the mixing process, with the amount of dispersion medium added being 5-10 times the total mass of the composite precursor.

[0011] The calcination treatment temperature is 500-700℃, the holding time is 1-3 hours, and the inert atmosphere includes argon. The flow rate of the inert atmosphere is 50-100 mL / min, and the inert atmosphere is continuously introduced during the calcination process to prevent air from entering and causing product oxidation; the calcination equipment is a tube furnace.

[0012] This invention also discloses a potassium-ion battery anode, which is prepared by any of the above-mentioned methods for preparing a potassium-ion battery anode. Specifically, it comprises a bismuth-tin dimer with a phase-separated structure and a porous carbon network coating the bismuth-tin dimer. The phase-separated structure includes a bismuth-rich phase and a tin-rich phase, with an interface formed between the two phases. The bismuth-rich phase has a particle size of 50-200 nm, the tin-rich phase has a particle size of 30-150 nm, and the interface width is 5-20 nm. The porous carbon network has a pore size of 10-100 nm, a porosity of 30%-60%, and a carbon coating thickness of 10-50 nm.

[0013] The present invention further discloses a potassium-ion battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is the aforementioned potassium-ion battery negative electrode. The battery is assembled in an argon-filled glove box, where the water and oxygen content is below 1 ppm.

[0014] The positive electrode comprises at least one of a Prussian blue analogue, a polyanionic compound, or a layered oxide; the electrolyte comprises a potassium salt-containing carbonate electrolyte; and the membrane comprises a glass fiber membrane or a polypropylene membrane. Specifically, the Prussian blue analogue comprises at least one of Prussian blue and Prussian white; the polyanionic compound comprises at least one of potassium iron phosphate and potassium vanadium phosphate; the layered oxide comprises at least one of potassium cobalt oxide and potassium nickel oxide; the potassium salt comprises at least one of potassium hexafluorophosphate and potassium bis(trifluoromethanesulfonyl)imide, and the concentration of the potassium salt in the electrolyte is 0.5-1.5 mol / L; the carbonate electrolyte comprises at least one of ethylene carbonate, dimethyl carbonate, and diethyl carbonate, with a volume ratio of 1:(1-2):(1-2); and the membrane has a thickness of 10-20 μm and a porosity of 40%-70%.

[0015] The present invention also discloses an application of a potassium-ion battery anode material, namely, using the above-mentioned potassium-ion battery anode to prepare a potassium-ion battery, which can be applied to at least one of energy storage devices, portable electronic devices, and electric vehicles.

[0016] This invention also discloses a method for preparing a potassium-ion battery. The method includes assembling a positive electrode, a negative electrode, a separator, and an electrolyte to form a battery, wherein the negative electrode is the aforementioned potassium-ion battery negative electrode. Specifically, the assembly step involves stacking the positive electrode, separator, and negative electrode sequentially, placing them in a battery casing, injecting electrolyte, and sealing them. The sealing pressure is 0.1-0.3 MPa, and the sealing time is 5-10 min. The positive electrode is prepared by mixing positive electrode active material, conductive agent, and binder in a mass ratio of 8:1:1, adding an appropriate amount of N-methylpyrrolidone, stirring evenly, coating the mixture onto aluminum foil, and then drying and rolling it. The drying temperature is 100-120℃, the drying time is 12-24 h, and the rolling pressure is 10-20 MPa.

[0017] This invention also provides the application of the above-mentioned phase separation structure and relay diffusion type bismuth-tin dimer carbon composite negative electrode material for potassium-ion batteries. The material is used as the negative electrode of a potassium-ion battery and is assembled with a positive electrode, electrolyte, and separator to form a potassium-ion battery. The positive electrode material is one or more of Prussian blue analogues (such as K3Fe(CN)6), polyanionic compounds (such as KTi2(PO4)3), or layered oxides (such as K2MnO4). The electrolyte is a potassium hexafluorophosphate-carbonate electrolyte (such as 0.8MKPF6 / EC+DMC+EMC, volume ratio 1:1:1). The separator is a glass fiber separator or a polypropylene separator.

[0018] The beneficial effects of this invention are: 1. This invention achieves precise control of phase separation structure, carbon coating thickness, and porous structure by precisely coordinating the Bi / Sn molar ratio, MOF precursor preparation parameters (organic solvent ratio, ligand dosage, hydrothermal parameters, etc.), carbon coating ratio (PVP dosage, ultrasonic stirring parameters, etc.), and calcination process (temperature, holding time, heating rate, etc.). This solves the technical pain points of uneven structure and blurred phase interface in existing bimetallic materials, and significantly improves the controllability of material structure.

[0019] 2. The phase separation structure constructed through multi-parameter collaboration enables the efficient operation of the relay diffusion potassium storage mechanism, significantly improving the potassium ion diffusion rate and electron transport efficiency, while effectively mitigating the volume expansion during potassium intercalation. The outer porous carbon network further enhances structural stability and ion transport capability, giving the material high specific capacity, excellent cycle stability, and rate performance.

[0020] 3. This invention adopts a process that combines hydrothermal synthesis and carbothermal reduction. The steps are simple and convenient to operate. All preparation parameters are easy to control. Moreover, the bismuth source, tin source, ligand and PVP and other reagents used are all conventional reagents, which are inexpensive and do not require complicated equipment, making them suitable for large-scale industrial production.

[0021] 4. The negative electrode material prepared by this invention can be widely used in high-performance potassium-ion batteries, especially in large-scale energy storage, portable electronic devices, electric vehicles and other fields. It can meet the application needs of different scenarios and has strong practicality and broad application prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The images show scanning electron microscope (SEM) images and particle size distribution diagrams of the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention. The SEM images show that the material has a uniform rod-like morphology, and the particle size distribution diagrams show that the material particles are concentrated in the submicron range. Figure 2 The image shows a transmission electron microscope (TEM) image of the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention. The "phase separation" structure in which Bi-rich and Sn-rich phases coexist can be clearly observed inside the material, and a clear phase interface is formed between the two phases (the boundary between the light and dark areas in the image). This phase interface is the core structural basis for realizing the "relay diffusion" potassium storage mechanism. At the same time, the porous carbon network of the outer coating can be observed, further confirming the successful preparation of the innovative structure of this invention. Figure 3 The image shows the X-ray diffraction pattern of the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention. The characteristic peaks correspond to the standard diffraction peaks of Bi and Sn, confirming the successful preparation of the bismuth-tin dimer. It also shows that there are no impurity peaks and the crystallinity is good. Figure 4 The image shows the Raman spectrum of the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention. The presence of the D peak and the G peak confirms the formation of the carbon coating layer. The high intensity of the D peak indicates that the carbon layer has abundant defects, which is beneficial for potassium ion transport. Figure 5 The thermogravimetric curve of the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention can be used to calculate the mass fraction of the carbon coating layer, confirming that the thickness of the carbon coating layer is appropriate. Figure 6 The graph shows the cycling performance of a potassium-ion battery assembled with the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention at a current density of 500 mA / g; it shows that the capacity retention rate is 79.3% after 300 cycles, and the cycling stability is excellent. Figure 7 The diagram shows the cycling performance of a potassium-ion battery assembled with the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention at a current density of 1000 mA / g; it shows that the capacity decay is slow and the cycling stability is good at high current densities. Figure 8 The graph shows the rate performance of a potassium-ion battery assembled with the bismuth-tin dimer carbon composite anode material prepared in Example 1 of this invention; it shows that the material can maintain a high reversible specific capacity and excellent rate performance under different current densities. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 A method for preparing a potassium-ion battery negative electrode, the specific steps of which are as follows: S1. Preparation of BiSn-MOF precursor: 298 mg of bismuth nitrate pentahydrate (purity ≥99.5%) and 92 mg of stannous chloride dihydrate (purity ≥99%) were dissolved in 60 mL of an organic solvent containing methanol and N,N-dimethylformamide in a volume ratio of 4:1. 1 mmol of 1,3,5-benzenetricarboxylic acid was added, and the mixture was stirred for 30 min until completely dissolved. The solution was then transferred to a 50 mL hydrothermal reactor and reacted at 120 °C for 24 h. After cooling to room temperature, the solution was centrifuged at 9000 r / min for 8 min, washed 4 times alternately with methanol and deionized water, and dried at 70 °C for 18 h to obtain rod-shaped BiSn-MOF precursor. S2, Carbon Coating and Calcination Reduction: The BiSn-MOF precursor prepared in step S1 was dispersed in a polyvinylpyrrolidone (PVP, molecular weight 10000) solution. The mass ratio of BiSn-MOF precursor to PVP was controlled at 1:2. The mixture was ultrasonically dispersed at 250W for 30 min, then magnetically stirred for 2 h, and freeze-dried at -45℃ for 12 h to obtain the BiSn-MOF / PVP composite. The composite was placed in a tube furnace, and argon gas (flow rate 80 sccm) was introduced. The temperature was increased to 600℃ at a rate of 2℃ / min, held for 2 h, and then naturally cooled to room temperature to obtain the anode material.

[0026] Example 2 Similar to Example 1, except that the amounts of bismuth nitrate pentahydrate and stannous chloride dihydrate in step S1 were adjusted to 499 mg and 47 mg, respectively, i.e., the molar ratio of bismuth source to tin source was 3:1 (Bi:Sn=3:1). The amounts of other reagents, operating parameters and steps were completely consistent with Example 1, and the negative electrode material was prepared.

[0027] Example 3 Similar to Example 1, except that the amounts of bismuth nitrate pentahydrate and stannous chloride dihydrate in step S1 were adjusted to 298 mg and 138 mg, respectively, that is, the molar ratio of bismuth source to tin source was 1:1 (Bi:Sn=1:1). The amounts of other reagents, operating parameters and steps were completely consistent with Example 1, and the negative electrode material was prepared.

[0028] Example 4 Similar to Example 1, except that the amounts of bismuth nitrate pentahydrate and stannous chloride dihydrate in step S1 were adjusted to 240 mg and 168 mg, respectively, i.e., the molar ratio of bismuth source to tin source was 1:1.5 (Bi:Sn=1:1.5). The amounts of other reagents, operating parameters and steps were completely consistent with Example 1, and the negative electrode material was prepared.

[0029] Example 5 Similar to Example 1, except that the amounts of bismuth nitrate pentahydrate and stannous chloride dihydrate in step S1 were adjusted to 200 mg and 186 mg, respectively, i.e., the molar ratio of bismuth source to tin source was 1:2 (Bi:Sn=1:2). The amounts of other reagents, operating parameters and steps were completely consistent with Example 1, and the negative electrode material was prepared.

[0030] Example 6 Same as Example 1, except that in step S2, the mass ratio of BiSn-MOF precursor to polyvinylpyrrolidone is adjusted to 1:1 (due to insufficient PVP). The remaining reagent amounts, operating parameters and steps are completely consistent with Example 1, and the negative electrode material is prepared.

[0031] Example 7 Same as Example 1, except that in step S2, the mass ratio of BiSn-MOF precursor to polyvinylpyrrolidone was adjusted to 1:3 (too much PVP was used). The remaining reagent amounts, operating parameters and steps were completely consistent with Example 1, and the negative electrode material was prepared.

[0032] Example 8 Same as Example 1, except that the calcination temperature in step S2 is adjusted to 500℃, while the remaining reagent dosages, operating parameters and steps are completely consistent with Example 1, and the negative electrode material is prepared.

[0033] Example 9 Same as Example 1, except that the calcination temperature in step S2 is adjusted to 700℃, while the remaining reagent dosages, operating parameters and steps are completely consistent with Example 1, and the negative electrode material is prepared.

[0034] Example 10 Same as Example 1, except that in step S1, the mixed organic solvent is methanol and N,N-dimethylformamide mixed at a volume ratio of 3:1. The amount of other reagents, operating parameters and steps are completely consistent with Example 1, and the negative electrode material is prepared.

[0035] Comparative Example 1 The specific steps are as follows: S1. Preparation of Bi-MOF precursor: 596 mg of bismuth nitrate pentahydrate was dissolved in 60 mL of an organic solvent containing a mixture of methanol and N,N-dimethylformamide at a volume ratio of 4:1. 1 mmol of 1,3,5-benzenetricarboxylic acid was added, and the mixture was stirred for 30 min until completely dissolved. The solution was then transferred to a 50 mL hydrothermal reactor and reacted at 120 °C for 24 h. After cooling to room temperature, the solution was centrifuged at 9000 r / min for 8 min, washed 4 times alternately with methanol and deionized water, and dried at 70 °C for 18 h to obtain rod-shaped Bi-MOF precursor. S2, Carbon Coating and Calcination Reduction: The Bi-MOF precursor prepared in step S1 was dispersed in a polyvinylpyrrolidone (PVP, molecular weight 10000) solution, and the mass ratio of Bi-MOF precursor to PVP was controlled at 1:2. The mixture was ultrasonically dispersed at 250W for 30 min, then magnetically stirred for 2 h, and freeze-dried at -45℃ for 12 h to obtain the Bi-MOF / PVP composite. The composite was placed in a tube furnace, and argon gas (flow rate 80 sccm) was introduced. The temperature was increased to 600℃ at a rate of 2℃ / min, held for 2 h, and then naturally cooled to room temperature to obtain the anode material.

[0036] Comparative Example 2 The specific steps are as follows: Preparation of S1 and Sn-MOF precursors: 368 mg of stannous chloride dihydrate was dissolved in 60 mL of an organic solvent containing a mixture of methanol and N,N-dimethylformamide at a volume ratio of 4:1. 1 mmol of 1,3,5-benzenetricarboxylic acid was added, and the mixture was stirred for 30 min until completely dissolved. The solution was then transferred to a 50 mL hydrothermal reactor and reacted at 120 °C for 24 h. After cooling to room temperature, the solution was centrifuged at 9000 r / min for 8 min, washed 4 times alternately with methanol and deionized water, and dried at 70 °C for 18 h to obtain rod-shaped Sn-MOF precursors. S2, Carbon Coating and Calcination Reduction: The Sn-MOF precursor prepared in step S1 was dispersed in a polyvinylpyrrolidone (PVP, molecular weight 10000) solution, and the mass ratio of Sn-MOF precursor to PVP was controlled at 1:2. The mixture was ultrasonically dispersed at 250W for 30 min, then magnetically stirred for 2 h, and freeze-dried at -45℃ for 12 h to obtain the Sn-MOF / PVP composite. The composite was placed in a tube furnace, and argon gas (flow rate 80 sccm) was introduced. The temperature was increased to 600℃ at a rate of 2℃ / min, held for 2 h, and then naturally cooled to room temperature to obtain the anode material.

[0037] (1) Electrochemical performance testing: The negative electrode material prepared in Example 1 was used as the working electrode, potassium metal sheet as the counter electrode and reference electrode, glass fiber as the separator, and 0.8M KPF6 / EC+DMC+EMC (volume ratio 1:1:1) as the electrolyte. A CR2032 coin cell potassium-ion battery was assembled in an argon glove box. The battery underwent constant current charge-discharge testing using a Blue Electric testing system. The test voltage range was 0.01-3.0V, the current density was 500mA / g, and the cycle length was 300 cycles. Simultaneously, rate performance testing was performed with current densities of 100mA / g, 200mA / g, 500mA / g, 1000mA / g, and 2000mA / g, with 5 cycles at each current density, finally returning to 100mA / g for 5 cycles.

[0038] Test results: After 300 cycles at a current density of 500 mA / g, the reversible specific capacity of the battery is still 201.5 mAh / g, with a capacity retention rate of 79.3%. After 100 cycles at a current density of 1000 mA / g, the reversible specific capacity remains above 210 mAh / g. Rate performance tests show that at current densities of 100 mA / g, 200 mA / g, 500 mA / g, 1000 mA / g, and 2000 mA / g, the reversible specific capacities are 285.3 mAh / g, 262.1 mAh / g, 252.7 mAh / g, 231.2 mAh / g, and 117.2 mAh / g, respectively. When the current density is restored to 100 mA / g, the capacity can be restored to 278.5 mAh / g.

[0039] (2) Performance comparison of different embodiments and comparative examples: Using the negative electrode materials prepared in Examples 1-10 and Comparative Examples 1-2, potassium-ion batteries were fabricated according to the method in Effect Example 1. The initial specific capacity and capacity retention after 300 cycles at a current density of 500 mA / g were tested. The test results are shown in Table 1 below. Table 1. Performance Comparison Results of Different Embodiments and Comparative Examples As shown in Table 1, the bismuth-tin dimer carbon composite anode materials prepared in Examples 1-10 of this invention exhibit significantly better electrochemical performance than Comparative Examples 1-2. The core reason lies in the fact that this invention, through precise synergistic control of the Bi / Sn molar ratio, MOF precursor preparation parameters, carbon coating ratio, and calcination process, successfully optimized the phase separation structure while constructing a highly efficient "relay diffusion" potassium storage mechanism. In contrast, Comparative Examples 1-2, lacking bimetallic synergistic design and multi-parameter synergistic control, could not form a phase separation structure and relay diffusion mechanism, relying solely on a single metal to complete the potassium intercalation process. This resulted in either severe volume expansion and extremely poor cycle stability (Comparative Example 1), or excessively low theoretical capacity, failing to meet practical application requirements (Comparative Example 2). Neither solution addressed the core pain points of the prior art, further highlighting the necessity and rationality of the multi-parameter synergistic control strategy of this invention.

[0040] Further analysis of the test data for each variable group in Table 1 reveals that Example 1, as the optimal parameter combination, achieved a synergistic match and mutual support among the preparation parameters, successfully forming a regular rod-shaped morphology, a uniform phase separation structure, and a carbon coating layer of moderate thickness. This provided a strong guarantee for the efficient operation of the "relay diffusion" mechanism, resulting in optimal initial specific capacity and cycle stability. In contrast, Examples 2-10, with only a single parameter deviating from the optimal value, led to an imbalance with other parameters. Specifically, this manifested as either uneven phase separation structure and blurred phase interfaces (Examples 2, 3, 5, 10), incomplete or excessively thick carbon layers (Examples 6, 7), or insufficient reduction of the MOF precursor or agglomeration of material particles (Examples 8, 9), ultimately resulting in varying degrees of decline in the electrochemical performance of the material. This phenomenon further confirms the core value of the synergistic regulation of the preparation parameters in this invention—independent optimization of a single parameter cannot achieve optimal material performance. Only when the parameters cooperate and are precisely matched can the bimetallic synergistic effect, the transport advantages of the phase separation structure, and the buffering and protective effect of carbon coating be fully utilized, ultimately achieving a dual improvement in material specific capacity and cycle stability.

Claims

1. A method for preparing a potassium-ion battery negative electrode, characterized in that, Includes the following steps: Provide bismuth-tin metal-organic framework precursors; The bismuth-tin metal-organic framework precursor was mixed with a carbon source to obtain a composite precursor; The composite precursor is calcined under an inert atmosphere to cause a carbothermic reduction reaction in the bismuth-tin metal-organic framework precursor, resulting in a bismuth-tin dimer with a phase-separated structure, which is then coated with carbon to form a potassium-ion battery anode material.

2. The preparation method according to claim 1, characterized in that, The bismuth-tin metal-organic framework precursor is prepared by a method comprising the following steps: dissolving a bismuth source and a tin source in an organic solvent, mixing them with an organic ligand, and then performing a solvothermal reaction to obtain the bismuth-tin metal-organic framework precursor.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the bismuth source to the tin source is (1-4):(1-2), the organic ligand includes 1,3,5-benzenetricarboxylic acid, and the organic solvent includes a mixed solvent of methanol and N,N-dimethylformamide, wherein the volume ratio of the mixed solvent is methanol:N,N-dimethylformamide = 4:

1.

4. The preparation method according to claim 1, characterized in that, The carbon source includes polyvinylpyrrolidone; the mass ratio of the bismuth-tin metal-organic framework precursor to the carbon source is 1:(1-3).

5. The preparation method according to claim 1, characterized in that, The calcination treatment temperature is 500-700℃, the calcination treatment holding time is 1-3h, and the inert atmosphere includes argon atmosphere.

6. A potassium-ion battery negative electrode, characterized in that, Prepared by the preparation method according to any one of claims 1 to 5, comprising: A bismuth-tin dimer with a phase-separated structure comprising a bismuth-rich phase and a tin-rich phase, wherein an interface is formed between the two phases; and A porous carbon network covering the outside of the bismuth-tin dimer.

7. A potassium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The negative electrode is the potassium-ion battery negative electrode according to claim 6.

8. The potassium-ion battery according to claim 7, characterized in that, The positive electrode includes at least one of a Prussian blue analogue, a polyanionic compound, or a layered oxide; the electrolyte includes a potassium salt carbonate electrolyte; and the diaphragm includes a glass fiber diaphragm or a polypropylene diaphragm.

9. An application of a potassium-ion battery anode material, characterized in that, The potassium-ion battery anode described in claim 6 is used to prepare a potassium-ion battery.

10. A method for preparing a potassium-ion battery, comprising the step of assembling a positive electrode, a negative electrode, a separator, and an electrolyte to form a battery, characterized in that, The negative electrode is the potassium-ion battery negative electrode according to claim 6.

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