Preparation method of sodium ion intercalation cadmium thiophosphate material

Abstract

The invention discloses a preparation method of a sodium ion intercalation cadmium thiophosphate material, and relates to the technical field of functional material preparation. The preparation method comprises the following steps: adding cadmium thiophosphate into a mixed aqueous solution of ethylenediaminetetraacetic acid and potassium salt, and stirring at the temperature of 40-60 DEG C to carry out first ion exchange reaction, so as to obtain a potassium ion intercalation cadmium thiophosphate intermediate; and adding the potassium ion intercalation cadmium thiophosphate intermediate into a sodium salt aqueous solution, stirring at the temperature of 20-30 DEG C, and carrying out secondary ion exchange reaction to obtain the sodium ion intercalation cadmium thiophosphate material. The method adopts a low-temperature water-phase ion exchange process, has the characteristics of mild conditions, simplicity and convenience in operation, environmental friendliness and the like, and is suitable for large-scale preparation. Effective intercalation of sodium ions can be realized under mild conditions, so that the interlayer spacing of the obtained material is obviously enlarged, the conductivity is obviously improved, and the material shows excellent energy storage performance when being used as a sodium ion battery negative electrode.

Description

Technical Field

[0001] This invention relates to the field of functional materials preparation technology, and in particular to a method for preparing sodium ion intercalated cadmium thiophosphate material. Background Technology

[0002] In the field of electrochemical energy storage, two-dimensional layered materials have attracted much attention due to their unique structure and easily tunable physicochemical properties. Modifying two-dimensional materials, such as controlling their interlayer spacing, introducing defects, or doping with elements, can effectively improve their electronic structure, ion transport kinetics, and structural stability, thereby enhancing their electrochemical performance in alkali metal ion (such as sodium-ion and potassium-ion) batteries. Among these modifications, alkali metal ion intercalation is a commonly used method, which can directly increase the interlayer spacing, reduce the ion diffusion barrier, and potentially introduce additional charge carriers, thereby improving the material's conductivity and ion migration rate.

[0003] However, traditional processes for achieving alkali metal ion intercalation often rely on high-temperature solid-state reactions or complex treatments under high vacuum and inert atmosphere protection. These methods are typically demanding, energy-intensive, and complex, which to some extent limits the controllable preparation and large-scale application of materials. Therefore, developing a mild, simple, and highly controllable intercalation preparation method is of great significance for promoting the practical application of high-performance two-dimensional electrode materials. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing sodium-ion intercalated cadmium thiophosphate materials, thereby solving the problems existing in the prior art. This invention provides a method for preparing sodium-ion intercalated cadmium thiophosphate materials under mild conditions and with simple operation. This method can achieve effective sodium ion intercalation under mild conditions, significantly increasing the interlayer spacing and conductivity of the resulting material, thus enabling it to exhibit excellent energy storage performance when used as a negative electrode in sodium-ion batteries.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention: a method for preparing a sodium ion-intercalated cadmium thiophosphate material, comprising the following steps: Cadmium thiophosphate (CdPS3) was added to a mixed aqueous solution of ethylenediaminetetraacetic acid and potassium (K) salt, and the mixture was stirred at 40-60°C to carry out the first ion exchange reaction, yielding potassium-intercalated cadmium thiophosphate (CdPS3). 2-2x Cd x PS3, 0 < x < 1) intermediate; The potassium-intercalated cadmium thiophosphate intermediate was added to an aqueous sodium (Na) salt solution, and a second ion exchange reaction was carried out by stirring at a temperature of 20-30°C (i.e., room temperature) to obtain the sodium-intercalated cadmium thiophosphate material (i.e., Na).2-2x Cd x PS3 material, 0 < x < 1).

[0006] In this invention, firstly, CdPS3 is subjected to a first ion exchange reaction with a mixed aqueous solution containing ethylenediaminetetraacetic acid and potassium salt in an aqueous phase system at 40-60°C to obtain the intermediate product K. 2-2x Cd x PS3; subsequently, K was placed at room temperature (20-30℃). 2-2x Cd x PS3 undergoes a second ion exchange reaction with an aqueous solution of sodium salt to finally obtain the target product Na. 2- 2x Cd x PS3 material. This invention employs a low-temperature aqueous phase ion exchange process, which features mild conditions, simple operation, and environmental friendliness, making it suitable for large-scale preparation. In the material prepared by this invention, sodium ions successfully insert into the CdPS3 interlayer, significantly expanding the interlayer spacing, while simultaneously forming cadmium vacancies, improving the material's conductivity, and causing the microstructure to transform from the original two-dimensional sheet-like structure to a one-dimensional rod-like structure, increasing the specific surface area and active sites. The obtained Na... 2-2x Cd x When PS3 material is used as an anode material in sodium-ion batteries, it exhibits excellent cycle stability and rate performance.

[0007] This invention achieves sodium ion intercalation through two ion exchange reactions. Direct ion exchange of CdPS3 in a sodium salt aqueous solution fails to achieve sodium ion intercalation. This is because the radius of hydrated sodium ions is too large (276 pm), preventing direct insertion into the interlayer space of CdPS3. In contrast, the smaller radius of hydrated potassium ions (232 pm) allows direct insertion into the interlayer space, thus widening the interlayer spacing.

[0008] In the first ion exchange reaction, ethylenediaminetetraacetic acid (EDTA) acts as a chelating agent and can react with Cd. 2+ Ion binding, consuming Cd 2+ This promotes the K in the solution + Cd removed by ion substitution 2+ Ions, generating K 2-2x Cd x PS3.

[0009] Furthermore, the potassium salt includes one or more of potassium carbonate (K2CO3), potassium chloride (KCl), potassium sulfate (K2SO4), and potassium nitrate (KNO3).

[0010] Furthermore, the concentration of potassium ions in the mixed aqueous solution (total concentration of all potassium ions) is 1-3 mol / L.

[0011] Furthermore, the molar ratio of ethylenediaminetetraacetic acid to potassium ions in the mixed aqueous solution is 1:1-1.5.

[0012] Furthermore, the ratio of the amount of cadmium thiophosphate to the amount of potassium ions contained in the mixed aqueous solution is 100 mg: 0.01-0.03 mol.

[0013] Furthermore, the reaction time for the first ion exchange reaction is 2-12 hours.

[0014] Furthermore, after the first ion exchange reaction is completed, the process also includes washing, centrifugation, and drying.

[0015] Furthermore, the sodium salt in the sodium salt aqueous solution includes one or more of sodium chloride, sodium fluoride, and sodium sulfate.

[0016] Furthermore, the sodium ion concentration in the sodium salt aqueous solution is 1-3 mol / L.

[0017] Furthermore, the ratio of the potassium ion intercalated cadmium thiophosphate intermediate to the sodium ions contained in the sodium salt aqueous solution is 100 mg: 0.01-0.03 mol.

[0018] Furthermore, the reaction time for the second ion exchange reaction is 1-5 hours.

[0019] Furthermore, after the second ion exchange reaction is completed, the process also includes washing, centrifugation, and drying.

[0020] Further, the preparation steps of the cadmium thiophosphate include: placing a mixture of phosphorus powder and sulfur powder in a molar ratio of 1:3-5 in the upstream temperature zone of a dual-temperature zone reaction apparatus, placing CdS powder in the downstream temperature zone of the dual-temperature zone reaction apparatus, and heating the upstream and downstream temperature zones to 280-320℃ and 520-600℃ respectively in a flowing inert atmosphere to carry out the reaction, thereby obtaining the cadmium thiophosphate.

[0021] Preferably, the dual-temperature zone reaction device includes a dual-temperature zone tube furnace.

[0022] Furthermore, the cadmium thiophosphate is a two-dimensional cadmium thiophosphate, that is, a two-dimensional cadmium thiophosphate nanosheet.

[0023] The method of this invention can obtain two-dimensional sheet-like cadmium thiophosphate materials, which, after two ion exchange reactions, can yield one-dimensional nanorod-shaped sodium ion-intercalated cadmium thiophosphate materials. In contrast, cadmium thiophosphate prepared by other methods, such as chemical vapor transport, is a bulk material, not a two-dimensional sheet-like material. If bulk cadmium thiophosphate is used as a raw material for the ion exchange reaction, the resulting alkali metal ion-intercalated cadmium thiophosphate material still retains a bulk morphology, rather than a one-dimensional nanorod-shaped morphology.

[0024] Furthermore, the upstream temperature zone is kept at 280-320℃ for 3 hours, and the downstream temperature zone is kept at 520-600℃ for 3 hours.

[0025] Furthermore, the flow rate of the inert atmosphere is 40-100 sccm.

[0026] The second technical solution of the present invention: a sodium ion intercalated cadmium thiophosphate material prepared by the above-described method.

[0027] The third technical solution of the present invention: the application of the above-mentioned sodium ion intercalated cadmium thiophosphate material in the preparation of sodium ion battery anode.

[0028] The fourth technical solution of the present invention: a sodium-ion battery negative electrode, the raw material of which includes the above-mentioned sodium-ion intercalated cadmium thiophosphate material.

[0029] Na prepared by this invention 2-2x Cd x In PS3 material, sodium ions are inserted into the interlayer space of two-dimensional CdPS3, widening the interlayer spacing. This widened interlayer spacing helps mitigate electrode volume expansion. 2-2x Cd x The Cd metal vacancies present in the PS3 materials can enhance Na... 2-2x Cd x The high electrical conductivity of PS3 material accelerates electron / ion transport. After the insertion of sodium ions, Na... 2-2x Cd x The morphology of PS3 material changes from a two-dimensional sheet-like structure to a one-dimensional rod-like structure, therefore Na 2-2x Cd x The increased specific surface area of ​​PS3 material provides more ion adsorption sites. Especially when used as an anode material in sodium-ion batteries, it exhibits excellent specific capacity, cycle stability, and rate performance.

[0030] The present invention discloses the following technical effects: Compared with traditional complex electrochemical intercalation and solvothermal methods, the low-temperature aqueous phase ion exchange strategy proposed in this invention is simpler to operate. The Na₂O₃ prepared by this invention... 2-2x Cdx Compared to pure CdPS3, PS3 materials have larger interlayer spacing and higher conductivity, providing a rapid channel for sodium ion migration and thus improving Na+. 2-2x Cd x The PS3 material is used as a negative electrode material in sodium-ion batteries, demonstrating improved cycle stability and rate performance. The Na2O material prepared in this invention... 2-2x Cd x PS3 material has a one-dimensional rod-like structure, which can provide more adsorption sites for sodium ions, thereby improving the specific capacity of the anode material. The Na prepared using this invention... 2-2x Cd x The sodium-ion battery assembled with PS3 materials can achieve a charge / discharge specific capacity of 1000mAh / g at a current density of 0.1A / g. Attached Figure Description

[0031] 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.

[0032] Figure 1 This is a SEM image of the two-dimensional CdPS3 material prepared in Example 1.

[0033] Figure 2 The image shows the SEM image of the K2-2xCdxPS3 intermediate prepared in Example 1.

[0034] Figure 3 The image shows a SEM image of the Na2-2xCdxPS3 material prepared in Example 1.

[0035] Figure 4 The image shows a SEM image of the bulk CdPS3 material prepared in Comparative Example 3.

[0036] Figure 5 The image shows a SEM image of the Na2-2xCdxPS3 material prepared in Comparative Example 4.

[0037] Figure 6 The images show the XRD patterns of the two-dimensional CdPS3, Na2-2xCdxPS3 and K2-2xCdxPS3 materials prepared in Example 1.

[0038] Figure 7 The charge-discharge curves are shown for a sodium-ion battery assembled using the Na2-2xCdxPS3 material prepared in Example 1 as the negative electrode material.

[0039] Figure 8The charge-discharge cycle curves are shown for sodium-ion batteries assembled using the Na2-2xCdxPS3 material prepared in Example 1 or the two-dimensional CdPS3 material prepared in Comparative Example 1 as the negative electrode material.

[0040] Figure 9 The charge-discharge curves of sodium-ion batteries assembled using the Na2-2xCdxPS3 material prepared in Example 1 or the two-dimensional CdPS3 material prepared in Comparative Example 1 as the negative electrode material are shown at different rates. Detailed Implementation

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0043] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0044] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0045] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0046] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0047] In the following embodiments, comparative examples and test examples of the present invention, if room temperature or normal temperature is involved, it specifically refers to 20-30℃.

[0048] All raw materials used in the following embodiments, comparative examples and test examples of this invention are commercially available products.

[0049] Example 1 A method for preparing a sodium ion-intercalated cadmium thiophosphate material, comprising the following steps: (1) Preparation of two-dimensional CdPS3 material (i.e., CdPS3 nanosheets): Phosphorus powder and sulfur powder were mixed in a molar ratio of 1:4. 1g of the phosphorus powder-sulfur powder mixture was placed in the upstream of a dual-temperature zone tube furnace; 500mg of CdS powder was placed in the downstream of the dual-temperature zone tube furnace. In a flowing argon atmosphere (argon flow rate of 60sccm), the upstream temperature zone was kept at 300℃ for 3h, and the downstream temperature zone was kept at 560℃ for 3h (after argon was introduced, the upstream and downstream temperature zones started to heat up simultaneously and reached the target temperature simultaneously). After natural cooling (argon was kept flowing during the cooling process), the downstream solid product was collected to obtain the two-dimensional CdPS3 material.

[0050] (2) First ion exchange (K + Intercalation): Weigh 100 mg of two-dimensional CdPS3 material and add it to 10 mL of a mixed aqueous solution of KCl, K2CO3, and ethylenediaminetetraacetic acid (KCl, K2CO3, and ethylenediaminetetraacetic acid concentrations were 1 mol / L, 1 mol / L, and 2 mol / L, respectively). Stir at 50 °C for 7 h to carry out the first ion exchange reaction. After the reaction, wash with deionized water by centrifugation. Place the centrifuged solid in a drying oven and dry at 60 °C for 12 h to obtain K... 2-2x Cd x PS3 intermediate.

[0051] (3) Second ion exchange (Na) + Exchange): 100mg K 2-2x Cd x The PS3 intermediate was added to 10 mL of a 2 mol / L NaCl aqueous solution and stirred at 30 °C for 3 h to carry out the second ion exchange reaction. After the reaction, the mixture was washed with deionized water by centrifugation. The solid separated by centrifugation was placed in a drying oven and dried at 60 °C for 12 h to obtain the final product, sodium ion-intercalated cadmium thiophosphate material, i.e., Na... 2-2x Cd x PS3 materials.

[0052] Example 2 A method for preparing a sodium ion-intercalated cadmium thiophosphate material, comprising the following steps: (1) Preparation of two-dimensional CdPS3 material: Same as step (1) in Example 1.

[0053] (2) First ion exchange (K + Intercalation): Weigh 100 mg of CdPS3 material and add it to 10 mL of a mixed aqueous solution of KCl, K2CO3, and ethylenediaminetetraacetic acid (KCl, K2CO3, and ethylenediaminetetraacetic acid concentrations were 0.5 mol / L, 0.75 mol / L, and 1.5 mol / L, respectively). Stir at 55 °C for 4 h to carry out the first ion exchange reaction. After the reaction, wash with deionized water by centrifugation. Place the centrifuged solid in a drying oven and dry at 60 °C for 12 h to obtain K... 2-2x Cd x PS3 intermediate.

[0054] (3) Second ion exchange (Na) + Exchange): 100mg K 2-2x Cd x The PS3 intermediate was added to 10 mL of a 2 mol / L NaCl aqueous solution and stirred at 30 °C for 1 h to carry out the second ion exchange reaction. After the reaction, the mixture was washed with deionized water by centrifugation. The centrifuged solid was placed in a drying oven and dried at 60 °C for 12 h to obtain the final product, sodium ion-intercalated cadmium thiophosphate material, i.e., Na... 2-2x Cd x PS3 materials.

[0055] Example 3 A method for preparing a sodium ion-intercalated cadmium thiophosphate material, comprising the following steps: (1) Preparation of two-dimensional CdPS3 material: Same as step (1) in Example 1.

[0056] (2) First ion exchange (K + Intercalation): Weigh 100 mg of CdPS3 material and add it to 10 mL of a mixed aqueous solution of K2SO4 and ethylenediaminetetraacetic acid (K2SO4 and ethylenediaminetetraacetic acid concentrations were 1.5 mol / L and 3 mol / L, respectively). Stir at 40 °C for 12 h to carry out the first ion exchange reaction. After the reaction, wash with deionized water by centrifugation. Place the centrifuged solid in a drying oven and dry at 60 °C for 12 h to obtain K... 2-2x Cd x PS3 intermediate.

[0057] (3) Second ion exchange (Na) + Exchange): 100mg K 2-2x Cd xThe PS3 intermediate was added to 10 mL of a 1 mol / L NaF aqueous solution and stirred at 30 °C for 5 h to carry out the second ion exchange reaction. After the reaction, the mixture was washed with deionized water by centrifugation. The centrifuged solid was placed in a drying oven and dried at 60 °C for 12 h to obtain the final product, sodium-intercalated cadmium thiophosphate material, i.e., Na... 2-2x Cd x PS3 materials.

[0058] Example 4 A method for preparing a sodium ion-intercalated cadmium thiophosphate material, comprising the following steps: (1) Preparation of two-dimensional CdPS3 material: Same as step (1) in Example 1.

[0059] (2) First ion exchange (K + Intercalation): Weigh 100 mg of CdPS3 material and add it to 10 mL of a mixed aqueous solution of KNO3 and ethylenediaminetetraacetic acid (both KNO3 and ethylenediaminetetraacetic acid concentrations are 2.5 mol / L). Stir at 60 °C for 2 h to carry out the first ion exchange reaction. After the reaction, wash with deionized water by centrifugation. Place the centrifuged solid in a drying oven and dry at 60 °C for 12 h to obtain K… 2-2x Cd x PS3 intermediate.

[0060] (3) Second ion exchange (Na) + Exchange): 100mg K 2-2x Cd x The PS3 intermediate was added to 10 mL of a 1.5 mol / L Na₂SO₄ aqueous solution and stirred at 30 °C for 1 h to carry out the second ion exchange reaction. After the reaction, the mixture was washed with deionized water by centrifugation. The centrifuged solid was placed in a drying oven and dried at 60 °C for 12 h to obtain the final product, sodium-intercalated cadmium thiophosphate material, i.e., Na₂SO₄. 2-2x Cd x PS3 materials.

[0061] Example 5 A method for preparing a sodium ion-intercalated cadmium thiophosphate material, comprising the following steps: (1) Preparation of two-dimensional CdPS3 material: Same as step (1) in Example 1.

[0062] (2) First ion exchange (K +Intercalation): Weigh 100 mg of CdPS3 material and add it to 10 mL of a mixed aqueous solution of KCl and ethylenediaminetetraacetic acid (both KCl and ethylenediaminetetraacetic acid concentrations are 1 mol / L). Stir at 50 °C for 8 h to carry out the first ion exchange reaction. After the reaction, wash with deionized water by centrifugation. Place the centrifuged solid in a drying oven and dry at 60 °C for 12 h to obtain K... 2-2x Cd x PS3 intermediate.

[0063] (3) Second ion exchange (Na) + Exchange): 100mg K 2-2x Cd x The PS3 intermediate was added to 10 mL of a 1 mol / L NaCl aqueous solution and stirred at 30 °C for 3 h to carry out the second ion exchange reaction. After the reaction, the mixture was washed with deionized water by centrifugation. The centrifuged solid was placed in a drying oven and dried at 60 °C for 12 h to obtain the final product, sodium ion-intercalated cadmium thiophosphate material, i.e., Na... 2-2x Cd x PS3 materials.

[0064] Example 6 A method for preparing a sodium ion-intercalated cadmium thiophosphate material, comprising the following steps: (1) Preparation of two-dimensional CdPS3 material: Same as step (1) in Example 1.

[0065] (2) First ion exchange (K + Intercalation): Weigh 100 mg of CdPS3 material and add it to 10 mL of a mixed aqueous solution of KCl and ethylenediaminetetraacetic acid (both KCl and ethylenediaminetetraacetic acid concentrations are 3 mol / L). Stir at 50 °C for 10 h to carry out the first ion exchange reaction. After the reaction, wash with deionized water by centrifugation. Place the centrifuged solid in a drying oven and dry at 60 °C for 12 h to obtain K... 2-2x Cd x PS3 intermediate.

[0066] (3) Second ion exchange (Na) + Exchange): 100mg K 2-2x Cd x The PS3 intermediate was added to 10 mL of a mixed aqueous solution of NaCl and NaF (both NaCl and NaF concentrations were 1.5 mol / L), and the mixture was stirred at 30 °C for 5 h to carry out the second ion exchange reaction. After the reaction, the mixture was washed with deionized water by centrifugation. The solid separated by centrifugation was placed in a drying oven and dried at 60 °C for 12 h to obtain the final product, sodium ion-intercalated cadmium thiophosphate material, i.e., Na... 2-2x Cdx PS3 materials.

[0067] Comparative Example 1 The preparation steps of two-dimensional CdPS3 material are as follows: Phosphorus powder and sulfur powder were mixed at a molar ratio of 1:4. 1g of this mixture was placed in the upstream section of a dual-temperature zone tubular furnace; CdS powder was placed in the downstream section. Under a flowing argon atmosphere (argon flow rate of 60 sccm), the upstream temperature zone was held at 300℃ for 3 hours, and the downstream temperature zone was held at 560℃ for 3 hours (after argon was introduced, both the upstream and downstream temperature zones began to heat up simultaneously and reached the target temperature at the same time). After natural cooling (argon was continuously introduced during the cooling process), the downstream solid product was collected to obtain two-dimensional CdPS3 material.

[0068] Comparative Example 2 The preparation steps for potassium ion-intercalated cadmium thiophosphate materials are as follows: (1) Preparation of two-dimensional CdPS3 material (i.e., CdPS3 nanosheets): Phosphorus powder and sulfur powder were mixed in a molar ratio of 1:4. 1g of the phosphorus powder-sulfur powder mixture was placed in the upstream of a dual-temperature zone tube furnace; CdS powder was placed in the downstream of the dual-temperature zone tube furnace. In a flowing argon atmosphere (argon flow rate of 60sccm), the upstream temperature zone was kept at 300℃ for 3h, and the downstream temperature zone was kept at 560℃ for 3h (after argon was introduced, the upstream and downstream temperature zones started to heat up simultaneously and reached the target temperature simultaneously). After natural cooling (argon was kept flowing during the cooling process), the downstream solid product was collected to obtain the two-dimensional CdPS3 material.

[0069] (2) Ion exchange (K + Intercalation): 100 mg of two-dimensional CdPS3 material was weighed and added to 10 mL of a mixed aqueous solution of KCl, K2CO3, and ethylenediaminetetraacetic acid (KCl, K2CO3, and ethylenediaminetetraacetic acid concentrations were 1 mol / L, 1 mol / L, and 2 mol / L, respectively). The mixture was stirred at 50 °C for 7 h to carry out the ion exchange reaction. After the reaction, the material was washed with deionized water by centrifugation. The solid separated by centrifugation was placed in a drying oven and dried at 60 °C for 12 h to obtain K... 2-2x Cd x PS3.

[0070] Comparative Example 3 The preparation steps for bulk CdPS3 material are as follows: Cadmium powder (2.0 g), phosphorus powder (0.5 g), and sulfur powder (1.6 g) were weighed out as reaction raw materials, thoroughly ground and mixed, and then transferred to the bottom of a quartz tube. The quartz tube was then vacuum-sealed and placed in a tube furnace, where it was reacted at a constant temperature of 700°C for 7 days. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, and the resulting product was transferred to a ceramic boat. Under a flowing argon atmosphere (argon flow rate of 100 sccm), the mixture was heated to 300°C and held for 30 minutes to remove residual sulfur and phosphorus powder, ultimately obtaining bulk CdPS3 material.

[0071] Comparative Example 4 Same as Example 1, except that step (1) is omitted and the two-dimensional CdPS3 material in step (2) is replaced with the bulk CdPS3 material prepared in Comparative Example 3.

[0072] Test Example 1 Morphological and structural characterization: Scanning electron microscopy (SEM) was used to examine the two-dimensional CdPS3 material prepared in Example 1 (i.e., the two-dimensional CdPS3 material prepared in Comparative Example 1) and K. 2-2x Cd x PS3 intermediate (i.e., K prepared in Comparative Example 2) 2-2x Cd x PS3) and Na 2-2x Cd x The PS3 material was observed for morphology, and the results are as follows: Figure 1-3 As shown, where, Figure 1 It is a two-dimensional CdPS3 material. Figure 2 For K 2-2x Cd x PS3 intermediate Figure 3 for Na 2-2x Cd x PS3 materials. For example... Figure 1 As shown, CdPS3 material has a typical two-dimensional sheet-like structure; as Figure 2 As shown, via K + After intercalation, K 2-2x Cd x The PS3 transforms into a one-dimensional rod-shaped morphology; such as Figure 3 As shown, via Na + After intercalation, the final Na 2-2x Cd x The PS3 material also exhibits a one-dimensional rod-like morphology. Furthermore, SEM was used to compare the bulk CdPS3 material prepared in Comparative Example 3 and the Na material prepared in Comparative Example 4. 2-2x Cd x The PS3 material was observed for morphology, and the results are as follows: Figure 4-5 As shown, where, Figure 4 It is a bulk CdPS3 material. Figure 5 for Na 2- 2x Cd x PS3 materials. For example... Figure 4 As shown, CdPS3 material has a bulk structure; as Figure 5 As shown, bulk CdPS3 material is treated with Na + After intercalation, the final Na 2-2x Cd x The PS3 material also exhibits a blocky shape.

[0073] Figure 6 The two-dimensional CdPS3 and Na prepared in Example 1 2-2x Cd x PS3 and K 2-2x Cd x The XRD pattern of the PS3 material shows that inserting K... + and Na + Subsequently, the diffraction peaks corresponding to the (001) plane all shifted to lower angles, and the interlayer spacing increased from 0.65 nm in CdPS3 material to 0.86 nm and 1.02 nm, respectively.

[0074] Test Example 2 Electrochemical performance testing: Na prepared according to various examples or comparative examples 2-2x Cd x PS3 material, CdPS3 material or K 2-2x Cd x The PS3 material was used as the negative electrode material to assemble a sodium-ion battery for electrochemical performance testing. The assembly steps and testing methods of the sodium-ion battery are as follows: A negative electrode material, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 80:10:10. An appropriate amount of N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred until homogeneous to form a slurry. This slurry was then coated onto a copper foil current collector and vacuum-dried at 100°C for 12 hours. The slurry was then cut into circular electrode sheets with a diameter of 12 mm. Each circular electrode sheet had an active material loading of 1.4 mg. The obtained circular electrode sheets were used as the negative electrode in a sodium-ion battery. A 1 mol / L NaPF6 solution of ethylene carbonate / dimethyl carbonate (EC / DMC, volume ratio 1:1) was used as the electrolyte, Whatman GF / D was used as the separator, and a sodium sheet was used as the counter electrode to assemble a CR 2025 coin-type sodium-ion battery.

[0075] The assembled sodium-ion batteries were charged and discharged at room temperature with a current density of 0.1 A / g to obtain charge-discharge curves and discharge specific capacities. The results are as follows: Figure 7 As shown in Table 1.

[0076] Each assembled sodium-ion battery was cycled 600 times at a current density of 1 A / g to obtain charge-discharge cycle curves and capacity retention rates. The results are as follows: Figure 8 As shown in Table 1.

[0077] The assembled sodium-ion batteries were subjected to rate performance tests at current densities of 0.1, 0.2, 0.5, 1, 2, and 5 A / g, respectively. Charge-discharge curves and discharge specific capacities at different rates were obtained, and the results are as follows: Figure 9 As shown in Table 1.

[0078] Figure 7 Na prepared in Example 1 2-2x Cd x The charge-discharge curves of a sodium-ion battery assembled using PS3 material as the negative electrode material are shown. It can be seen that the Na2O material prepared in Example 1... 2-2x Cd x Sodium-ion batteries assembled using PS3 materials as negative electrode materials achieve a discharge specific capacity of 1000mAh / g.

[0079] Figure 8 Na prepared in Example 1 2-2x Cd x Charge-discharge cycle curves of sodium-ion batteries assembled using PS3 material or CdPS3 material prepared in Comparative Example 1 as the negative electrode material. It can be seen that the Na2O2 prepared in Example 1... 2-2x Cd x Sodium-ion batteries assembled using PS3 material as the negative electrode material retained 91.2% of their capacity after 600 cycles at a current density of 1 A / g.

[0080] Figure 9 Na prepared in Example 1 2-2x Cd x Sodium-ion batteries assembled using PS3 material or the two-dimensional CdPS3 material prepared in Comparative Example 1 as the negative electrode material exhibit charge-discharge curves at different rates. It can be seen that the Na2O material prepared in Example 1... 2- 2x Cd x Sodium-ion batteries assembled using PS3 material as the negative electrode exhibit good structural stability and rate performance, with discharge specific capacities of 1000, 944, 904, 860, 820, and 765 mAh / g at current densities of 0.1, 0.2, 0.5, 1, 2, and 5 A / g, respectively.

[0081] Table 1 Depend on Figure 7-9 As shown in Table 1, compared with the unintercalated pure two-dimensional CdPS3 material in Comparative Example 1, the Na content of each embodiment... 2-2x Cdx The PS3 material showed significant improvements in specific capacity, cycle stability, and rate performance, indicating that sodium ion intercalation effectively optimized the material's structure and electrochemical performance.

[0082] Compared with the potassium ion intercalation in Comparative Example 2, K 2-2x Cd x Compared to PS3 material, the Na in Example 1 2-2x Cd x The PS3 material exhibits significantly higher specific capacity. This indicates that sodium ion intercalation, compared to potassium ion intercalation, allows for a larger interlayer spacing, thus achieving a higher specific capacity.

[0083] Compared with the block Na in Comparative Example 4 2-2x Cd x Compared to PS3 material, the Na in Example 1 2-2x Cd x The PS3 material exhibits significant advantages in specific capacity, cycle stability, and rate performance, indicating that the rod-shaped structure has a more significant performance improvement effect compared to the bulk structure.

[0084] Furthermore, compared with the bulk CdPS3 material in Comparative Example 3, the two-dimensional CdPS3 material in Comparative Example 1 also showed better performance in terms of specific capacity, cycle stability and rate performance, proving that the two-dimensional structure can more effectively improve the material performance than the bulk structure.

[0085] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a sodium ion-intercalated cadmium thiophosphate material, characterized in that, Includes the following steps: Cadmium thiophosphate was added to a mixed aqueous solution of ethylenediaminetetraacetic acid and potassium salt, and the mixture was stirred at 40-60°C to carry out the first ion exchange reaction, thereby obtaining a potassium ion intercalated cadmium thiophosphate intermediate. The potassium ion-intercalated cadmium thiophosphate intermediate was added to a sodium salt aqueous solution, and a second ion exchange reaction was carried out by stirring at a temperature of 20-30°C to obtain the sodium ion-intercalated cadmium thiophosphate material.

2. The method for preparing sodium ion-intercalated cadmium thiophosphate material as described in claim 1, characterized in that, The potassium salt includes one or more of potassium carbonate, potassium chloride, potassium sulfate, and potassium nitrate; And / or, the concentration of potassium ions in the mixed aqueous solution is 1-3 mol / L.

3. The method for preparing sodium ion-intercalated cadmium thiophosphate material as described in claim 1, characterized in that, The molar ratio of ethylenediaminetetraacetic acid to potassium ions in the mixed aqueous solution is 1:1-1.5; And / or, the ratio of the amount of cadmium thiophosphate to the amount of potassium ions contained in the mixed aqueous solution is 100 mg: 0.01-0.03 mol.

4. The method for preparing sodium ion-intercalated cadmium thiophosphate material as described in claim 1, characterized in that, The reaction time for the first ion exchange reaction is 2-12 hours.

5. The method for preparing sodium ion-intercalated cadmium thiophosphate material as described in claim 1, characterized in that, The sodium salt in the sodium salt aqueous solution includes one or more of sodium chloride, sodium fluoride, and sodium sulfate; And / or, the sodium ion concentration in the sodium salt aqueous solution is 1-3 mol / L; And / or, the ratio of the potassium ion intercalated cadmium thiophosphate intermediate to the sodium ions contained in the sodium salt aqueous solution is 100 mg: 0.01-0.03 mol.

6. The method for preparing sodium ion-intercalated cadmium thiophosphate material as described in claim 1, characterized in that, The reaction time for the second ion exchange reaction is 1-5 hours.

7. The method for preparing sodium ion intercalated cadmium thiophosphate material as described in claim 1, characterized in that, The preparation steps of the cadmium thiophosphate include: placing a mixture of phosphorus powder and sulfur powder in a molar ratio of 1:3-5 in the upstream temperature zone of a dual-temperature zone reaction apparatus, placing CdS powder in the downstream temperature zone of the dual-temperature zone reaction apparatus, and heating the upstream and downstream temperature zones to 280-320℃ and 520-600℃ respectively in a flowing inert atmosphere to carry out the reaction, thereby obtaining the cadmium thiophosphate.

8. A sodium ion intercalated cadmium thiophosphate material prepared by the method for preparing sodium ion intercalated cadmium thiophosphate material according to any one of claims 1-7.

9. The application of the sodium-ion intercalated cadmium thiophosphate material as described in claim 8 in the preparation of a sodium-ion battery anode.

10. A sodium-ion battery negative electrode, characterized in that, The raw materials include the sodium ion intercalated cadmium thiophosphate material as described in claim 8.

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