A sodium supplementing material capable of simultaneously supplementing active sodium and sodium hexafluorophosphate, and preparation and application thereof

Abstract

This invention relates to a sodium-supplementing material capable of simultaneously replenishing active sodium and sodium hexafluorophosphate, and its preparation and application. The sodium-supplementing material comprises the following raw material components by weight percentage: 10-50% elemental phosphorus, 50-90% sodium fluoride, and 1-5% Ketjen Black. Compared with existing technologies, the phosphorus-based bifunctional sodium-supplementing separator and sodium-supplementing cathode provided by this invention not only possess higher theoretical capacity, effectively compensating for irreversible capacity loss during the first cycle of the battery, but also generate NaPF6 in situ under electrochemical conditions through the synergistic reaction of red phosphorus and sodium fluoride, achieving simultaneous replenishment of active sodium and electrolyte sodium salts, thereby improving the initial coulombic efficiency and long-term cycle performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of sodium replenishment materials technology for sodium-ion batteries, and relates to a sodium replenishment material that can simultaneously replenish active sodium and sodium hexafluorophosphate, as well as its preparation and application. Background Technology

[0002] Sodium-ion batteries, with their abundant resources, low cost, and good safety, have shown broad application prospects in large-scale energy storage and low-cost power batteries. However, during the first charge and discharge of sodium-ion batteries, the high chemical reactivity of the negative electrode material surface inevitably leads to a series of side reactions with the electrolyte, consuming some sodium ions from the positive electrode and electrolyte components, and forming a solid electrolyte interphase (SEI) film on the negative electrode surface. Although the formation of the SEI film helps to suppress the continuous decomposition of the electrolyte and stabilize the electrode interface, thereby improving the cycle stability of the battery, its formation process causes significant loss of active sodium, resulting in a significant reduction in the initial capacity and initial coulombic efficiency of the battery. Taking the commonly used hard carbon negative electrode as an example, the loss of active sodium due to SEI formation during the first cycle can typically reach more than 10%; for high specific capacity negative electrode materials such as tin-based and phosphorus-based materials, this loss ratio can further increase to 15% or even higher, becoming a major bottleneck restricting the improvement of energy density and practical application of sodium-ion batteries.

[0003] To compensate for the irreversible loss of active sodium during SEI formation and to improve the initial coulombic efficiency and energy density of sodium-ion batteries, developing efficient and controllable sodium replenishment technologies has become a key direction in current sodium-ion battery research and industrialization. Cathode sodium replenishment materials, due to their better air stability and process compatibility, are more easily integrated with existing sodium-ion battery manufacturing processes, thus becoming a focus of current sodium replenishment technology research. Existing reported cathode sodium replenishment materials mainly include organic sodium replenishers (such as sodium salts of organic carboxylate and cyclic organic sodium salts) and inorganic sodium replenishers (such as transition metal sodium salts and polyanionic sodium salts).

[0004] However, the aforementioned sodium replenishment materials generally suffer from limited sodium replenishment capacity and significant side reactions during the sodium replenishment process. For example, some organic sodium replenishers or high-valence inorganic sodium salts release gas or undergo structural collapse during sodium replenishment, leading to unstable electrode interfaces, poor electrode material contact, and increased electrochemical impedance, thus affecting the overall performance of the battery. While some inorganic sodium replenishment materials do not produce gas during sodium replenishment, their poor air stability necessitates high environmental storage requirements, which is not conducive to industrial applications.

[0005] For example, Chinese patent CN119230828B provides a sodium-replenishing material, which mentions using sodium compounds such as sodium fluoride and reducing agents such as elemental phosphorus to generate sodium ions during secondary battery cycling, forming an SEI film, improving the battery's initial coulombic efficiency, and increasing conductivity in the electrolyte by controlling the reaction products, thus protecting the positive electrode material. However, the performance of this sodium-replenishing material in terms of battery specific capacity is still relatively low and needs further improvement. Summary of the Invention

[0006] The purpose of this invention is to provide a sodium replenishing material that can simultaneously replenish active sodium and sodium hexafluorophosphate, as well as its preparation and application, which can simultaneously replenish active sodium and sodium hexafluorophosphate during the first charge and discharge process of sodium-ion batteries, thereby improving the initial coulombic efficiency and cycle stability.

[0007] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a sodium supplement material that can simultaneously supplement active sodium and sodium hexafluorophosphate, comprising the following raw material components by weight percentage: 10-50% elemental phosphorus, 50-90% sodium fluoride, and 1-5% Ketjenblack.

[0008] Furthermore, the Ketjenblack is one or more of mesoporous carbon, Ketjenblack, carbon nanotubes, and graphene.

[0009] Furthermore, the elemental phosphorus is red phosphorus.

[0010] Furthermore, the mass ratio of elemental phosphorus to sodium fluoride is 1:3~8.

[0011] In a second aspect, the present invention provides a method for preparing a sodium-supplementing material that can simultaneously supplement active sodium and sodium hexafluorophosphate. Elemental phosphorus, sodium fluoride, and Ketjen black are weighed and ball-milled in an inert atmosphere or vacuum to obtain the sodium-supplementing material, which is the target product.

[0012] Furthermore, during the ball milling process, the rotation speed is 500~700 rpm and the time is 1~3 hours.

[0013] Furthermore, the inert atmosphere is provided by nitrogen or argon.

[0014] In a third aspect, the present invention provides a sodium-supplementing material that can simultaneously replenish active sodium and sodium hexafluorophosphate, and its application as a sodium-supplementing material in sodium-ion batteries.

[0015] Furthermore, the sodium-supplementing material is used to directly fabricate a positive electrode sheet, or to prepare a sodium-supplementing separator.

[0016] In a fourth aspect, the present invention provides a sodium-ion battery positive electrode sheet, comprising a positive electrode active material, a conductive agent, a binder, and a sodium supplementing material as described in the first aspect above, wherein the amount of the sodium supplementing material is 2 wt.% to 5 wt.%.

[0017] In a fifth aspect, the present invention provides a sodium-ion battery sodium-replenishing separator, which is obtained by preparing a slurry from the sodium-replenishing material, conductive agent and binder as described in the first aspect above and coating it onto the separator substrate, wherein the mass ratio of the sodium-replenishing material, conductive agent and binder is (7~9):(0.5~2):(0.5~1).

[0018] Compared with existing technologies, the sodium-supplementing material provided by this invention can be used in sodium-ion batteries, and is particularly suitable for negative electrode systems with high specific capacity or those prone to forming unstable interfaces. It can effectively compensate for the initial irreversible capacity loss and improve the initial coulombic efficiency and long-term cycle performance of the battery. Attached Figure Description

[0019] Figure 1 The charge-discharge curves of the PNF sample prepared in Example 1 at different rates are shown. Figure 2 XPS spectra of P2p and F1s of PNF under different charging states in Example 1; Figure 3 The cycle performance and coulombic efficiency of the full cells in Example 2 and Comparative Example 1; Figure 4 The cycle performance and coulombic efficiency of the full cells in Example 3 and Comparative Example 2; Figure 5 The cycle performance and coulombic efficiency of the full cell in Comparative Example 3 are shown. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0022] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0023] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0024] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0025] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0026] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0027] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0028] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0029] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0030] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0032] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0033] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0034] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0035] In some embodiments, the present invention provides a sodium supplement material that can simultaneously supplement active sodium and sodium hexafluorophosphate, comprising the following raw material components by weight percentage: 10-50% elemental phosphorus, 50-90% sodium fluoride, and 1-5% Ketjenblack.

[0036] Optionally, the elemental phosphorus is red phosphorus.

[0037] Optionally, the mass ratio of elemental phosphorus to sodium fluoride is 1:3 to 8.

[0038] The sodium supplement in this invention undergoes the following reaction under electrochemical conditions to generate sodium and NaPF6, achieving dual supplementation: P + 6NaF → NaPF6 + 5Na ++5e The reaction does not produce gas and leaves no solid insoluble residue. Its theoretical specific capacity is 474 mAh / g, effectively avoiding the interfacial instability problem caused by the release of gas from traditional sodium supplements (such as sodium oxalate and sodium ferrite).

[0039] Furthermore, this invention introduces Ketjenblack as a conductive component in the sodium supplement. Compared to conventional conductive carbon black and carbon nanotubes, after ball milling and compounding, Ketjenblack not only constructs a highly efficient conductive network but also achieves particle coating and dispersion during ball milling, enhancing interfacial contact. Its porous structure further promotes electrolyte wetting and ion transport, thereby optimizing the local reaction environment and electron-ion synergistic transport, and improving overall reaction kinetics and rate performance, thus effectively increasing specific capacity and reducing decomposition potential. In other embodiments, this invention also provides a method for preparing a sodium supplement material that can simultaneously supplement active sodium and sodium hexafluorophosphate. Elemental phosphorus, sodium fluoride, and Ketjenblack are weighed and ball-milled in an inert atmosphere or vacuum to obtain the sodium supplement material, which is the target product.

[0040] Optionally, during the ball milling process, the rotation speed is 500~700 rpm and the time is 1~3 hours. Here, when the ball milling speed is too low, such as using a low-energy ball mill of 200~300 rpm or conventional mechanical mixing methods such as sand milling or hand milling, the resulting sodium-supplementing material is difficult to bind tightly at the nanoscale because the components are difficult to adhere closely. Therefore, some materials are prone to losing electrical contact, making it difficult for electrochemical reactions to occur, and the sodium supplementer cannot play its role, resulting in a decrease in specific capacity.

[0041] In addition, the ball mill can be an existing device such as a planetary high-energy ball mill, and its structure itself is not an innovative point of protection of this invention, so it will not be described in detail here.

[0042] Alternatively, the inert atmosphere may be provided by nitrogen or argon.

[0043] In other embodiments, the present invention provides a sodium-supplementing material capable of simultaneously replenishing active sodium and sodium hexafluorophosphate, used as a sodium-supplementing material in sodium-ion batteries.

[0044] Optionally, when the sodium supplement is added to the sodium-ion battery, the applicable charging rate of the sodium-ion battery is 0.02C~0.1C, and the cutoff voltage is 4.3~4.5V.

[0045] Optionally, the sodium-supplementing material is used to directly form a positive electrode sheet, or to prepare a sodium-supplementing separator.

[0046] In a fourth aspect, the present invention provides a sodium-ion battery positive electrode sheet, comprising a positive electrode active material, a conductive agent, a binder, and a sodium supplementing material as described in the first aspect above, wherein the amount of the sodium supplementing material is 2 wt.% to 5 wt.%.

[0047] In a fifth aspect, the present invention provides a sodium-ion battery sodium-replenishing separator, which is obtained by preparing a slurry from the sodium-replenishing material, conductive agent and binder as described in the first aspect above and coating it onto the separator substrate, wherein the mass ratio of the sodium-replenishing material, conductive agent and binder is (7~9):(0.5~2):(0.5~1).

[0048] In the preparation of the positive electrode and the sodium-supplemented separator, the conductive agent used can be one or a mixture of Super-P, mesoporous carbon, Ketjen black, carbon nanotubes and graphene; the binder used can be one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and polyethyl methacrylate (PEMA).

[0049] Each of the above implementation methods can be implemented individually, or in any combination of two or more without violating logic.

[0050] The above-described embodiments will be described in more detail below with reference to specific examples.

[0051] In the following embodiments, the composition ratio of sodium ferric pyrophosphate (NFPP) or P2-type cathode (P2-NF) slurry is sodium ferric pyrophosphate (or P2-type cathode material, purchased from Shenzhen BTR New Energy Materials Co., Ltd., brand name BNH-P2B): conductive carbon Super P: binder PVDF (polyvinylidene fluoride) = 8:1:1 (mass ratio), the solvent is N-methylpyrrolidone (NMP), and the solid content is 30-50%, with the solid content here around 40%. The composition ratio of hard carbon anode slurry is 9:0.5:0.25:0.25, the solvent is deionized water, and the solid content is 40%. Unless otherwise specified, the electrolyte formulation used is a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1) containing 1 M sodium perchlorate (NaClO4) + 5% fluoroethylene carbonate (FEC). The polypropylene diaphragm used is a single-layer PP diaphragm with a thickness of 16um, Celgard PP1611.

[0052] Example 1: A mixture of red phosphorus (P), sodium fluoride (NaF), and Ketjen black (KB) (with a mass ratio of red phosphorus to sodium fluoride of 1:4 and Ketjen black accounting for 5% of the total mass of the mixture) was ball-milled at 600 r / min for 2 h to obtain a sample (PNF). This sample was then mixed with Super P and PVDF at a mass ratio of 7:2:1 to prepare a slurry. The slurry was coated onto aluminum foil and vacuum-dried at 60℃ for 12 h to obtain an active material loading of 1 mg / cm³. 2 The positive electrode and sodium metal negative electrode were assembled into a CR2032 button cell in an argon-protected glove box.

[0053] The CR2032 button cells prepared above were charged to 4.5 V at constant current rates of 0.02C, 0.05C, and 0.1C, respectively.

[0054] Figure 1 The charge-discharge curves of PNF at different rates are shown.

[0055] from Figure 1 It can be seen that PNF has a capacity of approximately 450 mAh g. -1 It exhibits good sodium replenishment capacity and low discharge specific capacity, demonstrating excellent sodium replenishment effect; increasing the charging rate does not significantly reduce the capacity of the PNF, reflecting good rate performance.

[0056] Figure 2 The XPS spectra of P2p and F1s of the PNF under different charging states in Embodiment 1 of the present invention are shown. Figure 2 It can be seen that the strength of PP bonds and Na-F bonds gradually decreases during the charging process, while the strength of PF bonds increases, indicating that PNF gradually decomposes during the charging process to generate NaPF6.

[0057] Example 2: A mixture of red phosphorus (P), sodium fluoride (NaF), and Ketjen black (KB) (with a mass ratio of red phosphorus to sodium fluoride of 1:4 and Ketjen black accounting for 5% of the total mass of the mixture) was ball-milled at 600 r / min for 2 h to obtain a sample (PNF). This sample was then mixed with Super P and PVDF in a ratio of 7:2:1 to prepare a slurry. This slurry was coated onto a polypropylene diaphragm and vacuum-dried for 12 h to obtain an active material loading of 0.2 mg / cm³. 2 A sodium-replenishing membrane was then used, and the sodium-replenishing membrane was then fitted with a membrane with an areal capacity of 0.5 mAh / cm². 2 The sodium iron pyrophosphate positive electrode sheet, with an areal capacity of 0.7 mAh / cm², is used. 2The hard carbon anode was used to assemble CR2032 button cells (denoted as NFPP / PLF / HC) in an argon-protected glove box. The first cycle was charged at 0.1C with constant current and constant voltage to 4.3 V, with a cutoff rate of 0.005C. Then, it was discharged at 0.1C with constant current to 1.5 V to complete the first cycle. After that, it was charged at 0.1C with constant current to 4 V and discharged at 0.1C with constant current to 1.5 V for two cycles of activation. Then, a long cycle test was performed at a rate of 0.5C, with the long cycle voltage range being [1.5 V, 4 V].

[0058] Comparative Example 1: A sodium iron pyrophosphate (NFPP) cathode slurry was prepared, and an areal capacity of 0.5 mAh / cm³ was obtained. 2 The positive electrode sheet, with an area capacity of 0.7 mAh / cm², is simultaneously used. 2 The hard carbon anode was used to assemble CR2032 button cells (denoted as NFPP / / HC) in an argon-protected glove box. The first cycle was charged at 0.1C with constant current and constant voltage to 4.3 V, with a cutoff rate of 0.005C. Then, it was discharged at 0.1C with constant current to 1.5 V to complete the first cycle. After that, it was charged at 0.1C with constant current to 4 V and discharged at 0.1C with constant current to 1.5 V for two cycles of activation. Then, a long cycle test was performed at a rate of 0.5C, with the long cycle voltage range being [1.5 V, 4 V].

[0059] Figure 3 The cycle performance and coulombic efficiency of the full cells in Example 2 and Comparative Example 1 of this invention are shown.

[0060] from Figure 3 It can be seen that using PNF as a sodium-supplemented separator exhibits a good sodium-supplementing effect in NFPP||HC full cells, significantly improving the discharge specific capacity. Moreover, the sodium-supplemented cells maintain better cycle stability and coulombic efficiency compared to the unsupplemented cells.

[0061] Example 3: A mixture of red phosphorus (P), sodium fluoride (NaF), and Ketjen black (KB) (with a mass ratio of red phosphorus to sodium fluoride of 1:4 and Ketjen black accounting for 5% of the total mass of the mixture) was ball-milled at 600 r / min for 2 h to obtain a sample (PNF). This sample was then mixed with Super P and PVDF at a mass ratio of 7:2:1 to prepare a slurry. This slurry was coated onto a polypropylene diaphragm and vacuum-dried for 12 h to obtain an active material loading of 0.2 mg / cm³. 2 A sodium-replenishing membrane was then used, and the sodium-replenishing membrane was then fitted with a membrane with an areal capacity of 0.5 mAh / cm². 2 The P2-type positive electrode (P2-NF) positive electrode sheet, with an areal capacity of 0.7 mAh / cm². 2The hard carbon anode was used to assemble CR2032 button cells (denoted as P2-NF / PLF / HC) in an argon-protected glove box. The first cycle was performed by constant current and constant voltage charging at 0.1C to 4.3V, with a cutoff rate of 0.005C. Then, the cells were discharged at 0.1C at a constant current to 2V to complete the first cycle. After that, the cells were charged at 0.1C at a constant current to 4.3V and discharged at 0.1C at a constant current to 2V for two cycles of activation. Then, a long-cycle test was performed at a 0.5C rate, with the long-cycle voltage range being [2V, 4.3V].

[0062] Comparative Example 2: A P2-type cathode (P2-NF) slurry was prepared, and a P2 cathode areal capacity of 0.5 mAh / cm² was obtained. 2 The positive electrode sheet, with an area capacity of 0.7 mAh / cm², is simultaneously used. 2 The hard carbon anode was used to assemble CR2032 button cells (denoted as P2-NF / / HC) in an argon-protected glove box. The first cycle was charged at 0.1C with constant current and constant voltage to 4.3 V, with a cutoff rate of 0.005C. Then, it was discharged at 0.1C with constant current to 2 V to complete the first cycle. After that, it was charged at 0.1C with constant current to 4.3 V and discharged at 0.1C with constant current to 2 V for two cycles of activation. Then, a long cycle test was performed at a rate of 0.5C, with the long cycle voltage range being [2 V, 4.3 V].

[0063] Figure 4 The cycle performance and coulombic efficiency of the full cells in Example 3 and Comparative Example 2 are given.

[0064] from Figure 4 It can be seen that using PNF as a sodium-supplemented separator exhibits a good sodium-supplementing effect in P2-NF||HC full cells, significantly improving the discharge specific capacity. Moreover, the sodium-supplemented cells maintain better cycle stability and coulombic efficiency compared to the unsupplemented cells.

[0065] Comparative Example 3: A slurry was prepared by mixing sodium oxalate (NCO), Super P, and PVDF in a ratio of 7:2:1. This slurry was then coated onto a polypropylene diaphragm and vacuum-dried for 12 hours to obtain an active material loading of 0.2 mg / cm³. 2 The sodium-replenishing membrane was then fitted with a membrane having a surface capacity of 0.5 mAh / cm². 2 The sodium iron pyrophosphate positive electrode sheet, with an areal capacity of 0.7 mAh / cm², is used. 2The hard carbon anode was used to assemble CR2032 button cells (denoted as NFPP / NCO / HC) in an argon-protected glove box. The first cycle was charged at 0.1C with constant current and constant voltage to 4.3 V, with a cutoff rate of 0.005C. Then, it was discharged at 0.1C with constant current to 1.5 V to complete the first cycle. After that, it was charged at 0.1C with constant current to 4 V and discharged at 0.1C with constant current to 1.5 V for two cycles of activation. Then, a long cycle test was performed at a rate of 0.5C, with the long cycle voltage range being [1.5V, 4V].

[0066] Figure 5 The cycle performance and coulombic efficiency of the full cell in Comparative Example 3 are shown.

[0067] from Figure 5 It can be seen that due to the high decomposition potential of sodium oxalate, there was no significant improvement in capacity and cycling performance. Compared with Example 3, it is evident that using the PNF sample of this application as a sodium supplement agent is significantly more effective than conventional sodium supplementation components such as sodium oxalate, and can effectively improve coulombic efficiency and cycling stability.

[0068] Comparative Example 4: It is almost identical to Example 3, except that Ketjen black is replaced with an equal mass of conductive carbon black.

[0069] Comparative Example 5: It is largely the same as Example 3, except that Ketjen Black is replaced with an equal mass of carbon nanotubes.

[0070] Comparative Example 6: Most of the components are the same as in Example 2, except that the mill speed is adjusted to 200 rpm.

[0071] Comparative Example 7: Most of the components are the same as in Example 2, except that the mill speed is adjusted to 1000 rpm.

[0072] Comparative Example 8: Compared to Example 2, most of the process is the same, except that the ball milling process is changed to sand milling for 6 hours.

[0073] Table 1. Charge specific capacity and decomposition potential of half-cells As shown in Table 1, the type of conductive carbon and the ball milling speed have a significant impact on particle coating and dispersion, and enhanced interfacial contact during ball milling. Specifically, regarding the type of conductive carbon, compared to conventional conductive carbon black and carbon nanotubes, Ketjenblack, after ball milling and compounding, not only constructs a highly efficient conductive network but also achieves particle coating and dispersion during ball milling, enhancing interfacial contact. Its porous structure further promotes electrolyte wetting and ion transport, thereby optimizing the local reaction environment and electron-ion synergistic transport, improving overall reaction kinetics and rate performance, thus effectively increasing specific capacity and reducing decomposition potential. As for the ball milling speed, if the speed is too low, the particle size reduction is limited, resulting in insufficient interfacial contact between different components, making it difficult for the electrochemical reaction to proceed effectively. This prevents the sodium supplementer from exerting its sodium-supplementing effect in subsequent applications, leading to lower capacity. Conversely, if the speed is too high, it does not further improve capacity but instead consumes excess energy.

[0074] Comparative Example 9: Most of them are the same as in Example 1, except that the charging rate is 0.3C.

[0075] Table 3 As shown in Table 3, when the charging rate is too high, the sodium-supplementing material exhibits significant polarization, making it difficult to utilize its capacity, and the decomposition potential also increases significantly.

[0076] In summary, the phosphorus-based bifunctional sodium-supplementing separator and sodium-supplementing cathode provided by this invention not only possess high theoretical capacity, effectively compensating for irreversible capacity loss during the first cycle of the battery, but also achieve simultaneous replenishment of active sodium and electrolyte sodium salts through the synergistic reaction of red phosphorus and sodium fluoride to generate NaPF6 in situ under electrochemical conditions, thereby improving the battery's initial coulombic efficiency and long-term cycle performance. This reaction process does not produce gas or leave solid residues, significantly reducing side reactions and interfacial instability. Furthermore, the selected raw materials exhibit good environmental stability, the preparation process is simple, and it has strong adaptability, making it particularly suitable for high-specific-capacity anode systems, demonstrating promising practical application prospects and industrialization potential.

[0077] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A sodium supplementing material capable of simultaneously supplementing active sodium and sodium hexafluorophosphate, characterized by comprising: The raw material components include the following weight percentages: elemental phosphorus 10-50%, sodium fluoride 50-90%, and Ketjen black 1-5%.

2. The sodium supplement material according to claim 1, capable of simultaneously supplementing active sodium and sodium hexafluorophosphate, is characterized in that, The elemental phosphorus mentioned is red phosphorus.

3. The sodium supplement material according to claim 1, capable of simultaneously supplementing active sodium and sodium hexafluorophosphate, is characterized in that, The mass ratio of elemental phosphorus to sodium fluoride is 1:3~8.

4. A method for preparing a sodium-supplementing material capable of simultaneously supplementing active sodium and sodium hexafluorophosphate as described in any one of claims 1-3, characterized in that, Elemental phosphorus, sodium fluoride, and Ketjen black are weighed and ball-milled in an inert atmosphere or vacuum to obtain a sodium-supplementing material, which is the target product.

5. The method for preparing a sodium supplement material capable of simultaneously supplementing active sodium and sodium hexafluorophosphate according to claim 4, characterized in that, During the ball milling process, the rotation speed is 500~700 rpm and the time is 1~3 hours; The inert atmosphere is provided by nitrogen or argon.

6. The application of a sodium-replenishing material capable of simultaneously replenishing active sodium and sodium hexafluorophosphate as described in any one of claims 1-3 in sodium-ion batteries.

7. The application according to claim 6, characterized in that, The sodium supplement is used to directly produce positive electrode sheets or to prepare sodium-supplemented separators.

8. The application according to claim 6, characterized in that, When the sodium supplement is added to the sodium-ion battery, the applicable charging rate of the sodium-ion battery is 0.02C~0.1C, and the cutoff voltage is 4.3~4.5V.

9. A sodium-ion battery positive electrode, characterized in that, It includes a positive electrode active material, a conductive agent, a binder, and a sodium supplement material as described in any one of claims 1-3, wherein the amount of the sodium supplement material is 2 wt.% to 5 wt.%.

10. A sodium-ion battery sodium-replenishing separator, characterized in that, The slurry is prepared by mixing the sodium-supplementing material, conductive agent and binder as described in any one of claims 1-3 and then coating it onto the membrane substrate, wherein the mass ratio of the sodium-supplementing material, conductive agent and binder is (7~9):(0.5~2):(0.5~1).

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