Sodium ion battery based on micron metal negative electrode and molten salt electrolyte

Abstract

The invention relates to a sodium ion battery based on a micron metal negative electrode and a molten salt electrolyte, the sodium ion battery comprises the micron metal negative electrode and the molten salt electrolyte, the micron metal negative electrode is a micron-sized Sb simple substance, a Sb alloy, a Sb compound or a Sb compound, and the molten salt electrolyte comprises NaFSI and KFSI. According to the sodium ion battery based on the micron metal negative electrode and the molten salt electrolyte, the molten salt electrolyte is adopted and does not contain an organic solvent, the problems of oxygenolysis of the organic solvent under high voltage and reductive decomposition of the organic solvent under low voltage are solved, and the molten salt electrolyte has high ionic conductance and low interface impedance under a high-temperature condition; and the constructed sodium ion battery has excellent electrochemical properties, including high capacity, high voltage, high efficiency, long cycle life and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a sodium-ion battery, more particularly to a sodium-ion battery based on a micron metal negative electrode and a molten salt electrolyte. BACKGROUND

[0002] With the global emphasis on environmental protection and sustainable development, renewable energy (such as wind energy, solar energy, etc.) has gradually become an important choice to replace traditional fossil energy, which is crucial to achieve the goal of "carbon neutralization" and "carbon peak". However, the intermittent and unstable characteristics of renewable energy make it difficult to be efficiently utilized without the development and application of large-scale energy storage systems. Among various energy storage systems, electrochemical energy storage systems are considered to play an important role in large-scale energy storage due to their high volume and mass energy density, flexible installation, etc. Lithium-ion batteries have been widely used in portable electronic devices, electric vehicles and large-scale energy storage due to their excellent electrochemical performance. However, China's lithium resource reserves account for only 7% of the world's total, and the supply of lithium resources is highly dependent on imports, making it difficult to meet the growing market demand. Global lithium resources are highly concentrated in Chile, Australia and Argentina, with these countries accounting for 72% of the world's lithium reserves in 2021. Therefore, to cope with the global lithium supply chain crisis, it is particularly important to develop new energy storage systems.

[0003] Sodium-ion battery systems have become an important development direction for future large-scale energy storage technology due to their abundant resources and low prices, and have received widespread attention. In recent years, under the joint efforts of scientists around the world, the performance of sodium-ion battery anode and cathode materials and electrolyte has been continuously breakthrough, which has promoted sodium-ion batteries to gradually move from laboratory research to large-scale industrialization. Numerous sodium-ion battery companies have emerged around the world, such as China's Zhongke Haina and Ningde Times, America's Natron Energy, Britain's Faradion and France's Tiamat, etc. have launched the first generation of sodium-ion battery products. Under the joint efforts of academia and industry, the industrialization process of sodium-ion batteries is constantly advancing, and its large-scale commercial application is almost within reach.

[0004] However, most of the current sodium-ion batteries still face the following two challenges.

[0005] First, most current sodium-ion batteries use organic electrolytes, i.e., by dissolving sodium salts in organic solvents to form electrolytes. Sodium-ion batteries constructed with organic liquid electrolytes use organic liquids as solvents to dissociate sodium salts, allowing the solvent to conduct sodium ions and ensure that the electrolyte has ionic conductivity. This is determined by the intrinsic properties of the electrolyte. However, this electrolyte system has certain safety hazards during battery overcharging or short circuiting. The heat generated inside the battery can quickly ignite the organic solvent, thereby exacerbating the battery's combustion or thermal runaway phenomenon. For example, CN202311442827.3 discloses a sodium-ion battery electrolyte, which includes inorganic sodium salt, composite solvent system with different donor numbers (including high DN value solvent and low DN value solvent) and additives, and shows good electrochemical performance when used in Hard carbon||Na3V2(PO4)3 full cell. However, although this electrolyte system has improved performance, it still relies on organic solvents and cannot fundamentally solve the safety problem of organic electrolytes. All-solid-state sodium-ion batteries use solid-state electrolytes to replace liquid electrolytes, which not only significantly improves the safety of the battery, but also helps to improve the energy density. However, existing inorganic solid-state electrolytes (such as oxides, sulfides and halides) still have many limitations in terms of ionic conductivity and interface compatibility with electrodes (including mechanical, chemical and electrochemical aspects), and the interface contact problem in solid-state batteries and the complex battery preparation process seriously limit the development and industrialization process of all-solid-state sodium-ion batteries.

[0006] Secondly, the negative electrode material of sodium ion battery generally uses amorphous carbon material (including soft carbon and hard carbon), and the specific capacity is generally less than 300 mAh / g, which limits the energy density of the full battery system to some extent. For example, CN202311100138.4 discloses a method for preparing a long-cycle full battery by adjusting the N / P ratio of sodium vanadium phosphate and hard carbon. The battery system uses sodium vanadium phosphate as the positive electrode and hard carbon as the negative electrode material, and the electrolyte is a 1M NaPF6 solution in an organic solvent. For another example, CN202210834056.1 discloses a polyformaldehyde semi-solid sodium ion battery and its preparation method and application. Without reducing the amount of liquid electrolyte injection, part of the solvent of the liquid electrolyte is replaced with trioxymethylene, which is in-situ polymerized in the battery during battery formation to form polyformaldehyde insoluble in the liquid component, forming a semi-solid sodium ion battery containing polyformaldehyde. The battery system uses sodium vanadium phosphate as the positive electrode and hard carbon as the negative electrode material, and exhibits good cycle stability. For another example, Liu et al. also reported the electrochemical performance of a full battery constructed with Na3V2(PO4)3 positive electrode material and hard carbon negative electrode material, and the electrolyte is a liquid organic ether electrolyte (NaPF6 dissolved in diglyme). The full battery constructed exhibits good cycle stability. Although these studies improve the cycle stability of sodium ion batteries to some extent, the specific capacity of the negative electrode material is still low, which limits the energy density of the full battery system. In addition, when metal elements (such as Sn, Sb, Bi, etc.) that can form alloys with sodium ions are used as negative electrode materials of sodium ion batteries, although the specific capacity can be greater than 400 mAh / g, these materials have a serious volume expansion problem (volume expansion rate greater than 290%) during sodium ion intercalation / deintercalation, which seriously affects the cycle stability of sodium ion batteries. Although nanocrystallization and carbon coating techniques can effectively inhibit the volume expansion of alloy negative electrodes during the cycle process to some extent, the application of these techniques will increase the preparation cost and reduce the volume energy density. In addition, because the discharge voltage of NaCrO2 is low, NaZn||NaCrO2 exhibits good electrochemical performance in molten salt electrolyte, but the output voltage of the full battery constructed is low, and the energy density is low, therefore, NaZn||NaCrO2 has high cost and low energy density, which limits its potential for large-scale application. SUMMARY

[0007] In order to solve the problems of safety hazards in the existing liquid electrolyte, poor performance of solid-state electrolyte battery, low capacity of carbon-based negative electrode material, and serious volume expansion of metal element negative electrode in the prior art, the present application provides a sodium ion battery based on a micron metal negative electrode and a molten salt electrolyte.

[0008] The sodium ion battery based on the micron metal negative electrode and the molten salt electrolyte according to the application comprises a micron metal negative electrode and a molten salt electrolyte, wherein the micron metal negative electrode is a micron-sized Sb element, Sb alloy, Sb compound or Sb composite, and the molten salt electrolyte comprises NaFSI and KFSI.

[0009] In a preferred embodiment, the size of the micron metal negative electrode particle is between 1 micrometer and 20 micrometers.

[0010] In a preferred embodiment, the micron metal negative electrode is micron Sb, micron Sb-Sn alloy, micron Sb-Bi alloy, micron SbO2, micron SbS2 or carbon-coated micron Sb.

[0011] In a preferred embodiment, the molar ratio of NaFSI and KFSI is 56:44.

[0012] In a preferred embodiment, the molten salt electrolyte further comprises CsFSI.

[0013] In a preferred embodiment, the mass percentage of CsFSI in the molten salt electrolyte is 5% to 15%.

[0014] In a preferred embodiment, the sodium ion battery further comprises a positive electrode.

[0015] In a preferred embodiment, the positive electrode is Na3Fe2(SO4)3, Na3V2(PO4)3, Na4Fe3(PO4)2(P2O7), Prussian blue / white or layered oxide.

[0016] In a preferred embodiment, the sodium ion battery further comprises a separator, wherein the separator is a PP separator, a modified PP separator, a modified PE separator, a glass fiber separator or a polyimide separator.

[0017] In a preferred embodiment, the working temperature of the sodium ion battery is 70-150°C.

[0018] The sodium ion battery based on the micron metal negative electrode and the molten salt electrolyte according to the application adopts the molten salt electrolyte, does not contain organic solvents, avoids the problems of oxidative decomposition at high voltage and reductive decomposition at low voltage of organic solvents, and has high ion conductivity and low interface impedance under high temperature conditions, so as to ensure that the constructed sodium ion battery has excellent electrochemical performance, including high capacity, high voltage, high efficiency and long cycle life and other advantages. These advantages make the sodium ion battery of the application have broad application prospects in large-scale energy storage, extreme conditions (such as high temperature environment) and other fields. DETAILED DESCRIPTION

[0019] The sodium-ion battery according to the present application comprises a micron metal negative electrode, a molten salt electrolyte and a positive electrode, which can be expressed as micron metal negative electrode || molten salt electrolyte || positive electrode.

[0020] In the present application, the micron metal negative electrode is micron-sized antimony (Sb) element, Sb alloy, Sb compound or Sb composite, with a reversible capacity greater than 500 mAh / g. In preferred embodiments, the size of the micron metal negative electrode particles is between 1 micron and 20 microns, maintaining good cycle stability. In particular, micron Sb has very poor cycle stability in liquid electrolyte, but micron Sb exhibits very good compatibility with molten salt electrolyte. This is because in the molten salt electrolyte, molten salt ions generate a protective layer in situ on the surface of micron Sb during electrochemical processes, inhibiting the continuous expansion of the volume of micron Sb and the interface side reaction. Moreover, micron Sb exhibits excellent cycle stability in molten molten salt electrolyte, and thus the sodium-ion battery constructed therefrom exhibits many advantages, including high operating voltage, high energy density, high safety, high temperature characteristics and good cycle stability.

[0021] As a negative electrode material, micron Sb has a higher sodium intercalation capacity than Na-Zn alloy negative electrode, which can reach 650 mAh / g, and has better performance, larger capacity and longer cycle. In addition, compared with materials such as hard carbon, soft carbon and nano-Sb, micron Sb not only has low cost and simple preparation process, but also can provide higher specific capacity, and the use of micron Sb as a negative electrode material for sodium-ion batteries effectively improves the overall performance and economy of the battery.

[0022] In addition to micron Sb, the negative electrode material of the present application can also be its related alloy (such as micron Sb-Sn, Sb-Bi alloy, etc.), its related compound (such as micron SbO2 or micron SbS2) or its related composite (such as carbon-coated micron Sb), etc. These materials not only inherit the advantages of micron Sb, but also further optimize the electrochemical performance through alloying or surface modification. For example, micron Sb-Sn alloy utilizes the synergistic effect of Sb and Sn to significantly improve the electronic conductivity and interface stability of the material, while effectively inhibiting the volume expansion, thereby significantly improving the performance of the negative electrode material. For another example, carbon-coated micron Sb significantly improves the electronic conductivity and interface stability of the negative electrode material by coating a layer of carbon material on the surface of micron Sb, effectively inhibiting the volume expansion, and also improving the cycle stability and rate performance of the material, thereby further improving the electrochemical performance of the sodium-ion full battery. These diversified negative electrode material options provide more space for the design and optimization of sodium-ion batteries.

[0023] In the present application, the molten salt electrolyte is NaFSI and KFSI. The full name of NaFSI in Chinese is sodium bis(fluorosulfonyl)imide, the chemical formula is F2NNaO4S2, and the CAS number is 100669-96-3. The full name of KFSI in Chinese is potassium bis(fluorosulfonyl)imide, the English name is potassium bis(fluorosulfonyl)imide, the alias is potassium bis(fluorosulfonyl)amide, the chemical formula is KN(SO2F)2, and the CAS number is 14984-76-0. In a preferred embodiment, the molar ratio of NaFSI and KFSI is 56:44.

[0024] In particular, the present application uses pure molten salt as electrolyte, which is solid at room temperature and liquid when the temperature is raised to above 60°C (for example, at a working temperature of 80°C). It exhibits very high sodium ion conductivity and sodium ion transference number. The molten salt electrolyte used in the present application only contains salt and does not contain organic solvent, so the safety performance is greatly improved. Compared with traditional liquid electrolyte, the traditional liquid electrolyte contains both electrolyte salt and organic liquid solvent. The organic liquid solvent is prone to redox decomposition, and the electrolyte salt is also prone to redox decomposition. The resulting solid electrolyte interface (SEI) impedance is large and the volume expansion resistance is poor, so the compatibility is poor. The solid electrolyte interface (SEI) impedance produced by the redox decomposition of the molten salt electrolyte used in the present application is small and the volume expansion resistance is excellent, so the compatibility is good. In addition, in terms of ionic conductivity, the molten salt electrolyte is higher than the traditional liquid electrolyte, because the molten salt electrolyte does not have solvation effect, and the ion transmission is more efficient at higher temperature.

[0025] In addition to the above-mentioned NaFSI and KFSI mixed molten salt electrolyte, other salts such as CsFSI can also be added to the molten salt electrolyte to further reduce the melting point and improve the performance. The full name of CsFSI in Chinese is cesium bis(fluorosulfonyl)imide, the English name is Cesium bis(fluorosulfonyl)imide, the alias is Cesium bis(fluorosulfonyl)amide, and the chemical formula is CsN(SO2F)2. The addition of CsFSI can improve the cycle stability of the battery. The reason is that the addition of Cesium changes the microstructure of the electrolyte, regulates the solid electrolyte interface properties, stabilizes the interface, and thus improves the overall performance of the battery. In a preferred embodiment, the mass percentage of CsFSI in the molten salt electrolyte is 5%-15%, preferably 10%.

[0026] In the present application, the positive electrode is a commercialized positive electrode material, such as commercialized sodium iron sulfate (Na3Fe2(SO4)3), which can provide a higher discharge voltage platform, thereby outputting more energy at the same current, and thus improving the energy density of the battery. The sodium iron sulfate positive electrode material used has significant advantages. Specifically, the average sodium intercalation voltage of this material is higher, and compared with other positive electrode materials (such as NaCrO2), it can provide a higher energy density. This characteristic makes sodium iron sulfate an ideal positive electrode material for sodium-ion batteries, which helps to improve the overall performance of the battery, and the electrochemical comprehensive performance is optimal.

[0027] In addition to sodium iron sulfate (Na3Fe2(SO4)3), the present application can also use other positive electrode materials. For example, sodium vanadium phosphate (Na3V2(PO4)3) positive electrode material is also a good choice, which has the advantages of better cycle stability than Na3Fe2(SO4)3 and better rate characteristics. In addition, sodium iron pyrophosphate is also suitable for the present application, such as Na4Fe3(PO4)2(P2O7), which has lower cost, and its cycle stability, rate characteristics and specific capacity are all better than Na3Fe2(SO4)3. The positive electrode material can also use Prussian blue / white and layered oxides, etc. These positive electrode materials all have good electrochemical performance and cycle stability, which can meet the needs of different application scenarios, and further improve the performance and applicability of sodium-ion batteries.

[0028] The sodium-ion battery according to the present application also includes a separator. The separator material can be selected according to factors such as chemical stability, mechanical strength, porosity, and compatibility with electrolyte. In the present application, the separator can be made of various materials, including PP (polypropylene), modified PP, modified PE (polyethylene), glass fiber separator, and polyimide separator, etc.

[0029] The sodium-ion battery according to the present application can work at a temperature of 80-150°C, showing excellent electrochemical performance, including high capacity, high voltage, high efficiency, long cycle, etc. In addition, the sodium-ion battery according to the present application has the advantages of high safety, long calendar life, etc., and has very good application prospects. For example, in the preferred embodiment, the average working voltage of the battery is between 2.2V and 3.0V, the energy density reaches 90 to 120 Wh / kg, the cycle life is 90 to 96% (100 cycles), and the battery still maintains high electrochemical performance at a higher working temperature (80°C). For another example, in the embodiment of micron Sb alloy negative electrode, the average working voltage of the battery is increased to 3.2V, and the energy density reaches 130 Wh / kg, which can further improve the electrochemical performance of the sodium-ion battery.

[0030] The preferred embodiments of the present application are given below and described in detail.

[0031] Example 1

[0032] The micron Sb||Na3Fe2(S04)3 molten salt sodium-ion battery was constructed. The micron Sb as anode material, conductive agent Super P, binder PVDF were mixed according to the mass ratio of 90:5:5 to prepare the slurry, then coated on the Al current collector, dried, rolled, cut, weighed to obtain the anode material. The commercial Na3Fe2(S04)3 cathode material, conductive agent Super P, binder PVDF were mixed according to the mass ratio of 90:5:5 to prepare the slurry, then coated on the Al current collector, dried, rolled, cut, weighed to obtain the cathode material. NaFSI: KFSI ratio 56: 44 (molar ratio) as electrolyte.

[0033] The battery was assembled in a glove box (water and oxygen values less than 0.5 ppm), and the temperature was maintained at 80 ℃ (range can be 70-150 ℃) during assembly. The mass of the molten salt electrolyte was 70 mg. The separator was a glass fiber separator. The micron Sb||Na3Fe2(S04)3 was assembled and cycled at 80 ℃. The electrochemical performance is shown in Table 1, including working voltage, energy density, cycle life, working temperature.

[0034] Example 2

[0035] The micron Sb||Na3V2(PO4)3 molten salt sodium-ion battery was constructed. The micron Sb as anode material, conductive agent Super P, binder PVDF were mixed according to the mass ratio of 90:5:5 to prepare the slurry, then coated on the Al current collector, dried, rolled, cut, weighed to obtain the anode material. The commercial Na3V2(PO4)3 cathode material, conductive agent Super P, binder PVDF were mixed according to the mass ratio of 90:5:5 to prepare the slurry, then coated on the Al current collector, dried, rolled, cut, weighed to obtain the cathode material. NaFSI: KFSI ratio 56: 44 (molar ratio) as electrolyte.

[0036] The battery was assembled in a glove box (water and oxygen values less than 0.5 ppm), and the temperature was maintained at 80 ℃ during assembly. The mass of the molten salt electrolyte was 70 mg. The separator was a glass fiber. The micron Sb||Na3Fe2(S04)3 battery was assembled and cycled at 80 ℃. The electrochemical performance is shown in Table 1, including working voltage, energy density, cycle life, working temperature.

[0037] Example 3

[0038] Build micron Sb||Na4Fe3(PO4)2(P2O7) molten salt sodium-ion battery. With micron Sb negative electrode material, conductive agent Super P, binder PVDF mixed according to the mass ratio of 90:5:5 to prepare slurry, then coated on Al current collector, dried, rolled, cut, weighed to get negative electrode material. With commercial Na4Fe3(PO4)2(P2O7) positive electrode material, conductive agent Super P, binder PVDF mixed according to the mass ratio of 90:5:5 to prepare slurry, then coated on Al current collector, dried, rolled, cut, weighed to get positive electrode material. NaFSI: KFSI ratio 56: 44 (molar ratio) as electrolyte.

[0039] Battery assembly in glove box (water and oxygen value less than 0.5 ppm), the temperature is maintained at 80 ℃ during assembly. The mass of molten salt electrolyte is 70 mg. The separator is glass fiber. Assembled into micron Sb||Na3V2(PO4)3 battery, cycled at 80 ℃. Its electrochemical performance is shown in Table 1, including working voltage, energy density, cycle life, working temperature.

[0040] Example 4

[0041] Build Sb||Na3Fe2(SO4)3 molten salt sodium-ion battery. With micron Sb negative electrode material, conductive agent Super P, binder PVDF mixed according to the mass ratio of 90:5:5 to prepare slurry, then coated on Al current collector, dried, rolled, cut, weighed to get negative electrode material. With commercial Na3Fe2(SO4)3 positive electrode material, conductive agent Super P, binder PVDF mixed according to the mass ratio of 90:5:5 to prepare slurry, then coated on Al current collector, dried, rolled, cut, weighed to get positive electrode material. NaFSI: KFSI ratio 56: 44 (molar ratio) + 10% mass ratio CsFSI additive as electrolyte.

[0042] Battery assembly in glove box (water and oxygen value less than 0.5 ppm), the temperature is maintained at 80 ℃ during assembly (range can be 80-150 ℃). The mass of molten salt electrolyte is 70 mg. The separator is glass fiber separator. Assembled into Sb||Na3Fe2(SO4)3 battery, cycled at 80 ℃. Its electrochemical performance is shown in Table 1, including working voltage, energy density, cycle life, working temperature.

[0043] Example 5

[0044] The micron Sb-Sn alloy||Na3Fe2(SO4)3 molten salt sodium-ion battery was constructed. The micron Sb-Sn alloy was synthesized by a solid-state method. The slurry was prepared by mixing the micron Sb-Sn alloy negative electrode material, conductive agent Super P, and binder PVDF in a mass ratio of 90:5:5, then coated on the Al current collector, dried, rolled, cut, and weighed to obtain the negative electrode material. The slurry was prepared by mixing the commercialized Na3Fe2(SO4)3 positive electrode material, conductive agent Super P, and binder PVDF in a mass ratio of 90:5:5, then coated on the Al current collector, dried, rolled, cut, and weighed to obtain the positive electrode material. NaFSI: KFSI ratio 56: 44 (molar ratio) + 10% mass ratio CsFSI additive as electrolyte.

[0045] The battery was assembled in a glove box (water and oxygen value less than 0.5 ppm), and the temperature was maintained at 80 °C (range can be 80-150 °C) during assembly. The mass of the molten salt electrolyte was 70 mg. The separator was a glass fiber separator. The micron Sb-Sn alloy||Na3Fe2(SO4)3 battery was assembled and cycled at 80 °C. The electrochemical performance is shown in Table 1, including working voltage, energy density, cycle life, and working temperature.

[0046] Example 6

[0047] The micron carbon-coated Sb||Na3Fe2(SO4)3 molten salt sodium-ion battery was constructed. The synthesis of carbon-coated micron Sb used a solid-state method. A uniform carbon layer was coated on the surface of micron Sb at 600 °C by an in-situ carbonization method using organic sucrose, which changed the interfacial properties, electronic conductivity, and other physicochemical properties. The slurry was prepared by mixing the carbon-coated micron Sb negative electrode material, conductive agent Super P, and binder PVDF in a mass ratio of 90:5:5, then coated on the Al current collector, dried, rolled, cut, and weighed to obtain the negative electrode material. The slurry was prepared by mixing the commercialized Na3Fe2(SO4)3 positive electrode material, conductive agent Super P, and binder PVDF in a mass ratio of 90:5:5, then coated on the Al current collector, dried, rolled, cut, and weighed to obtain the positive electrode material. NaFSI: KFSI ratio 56: 44 (molar ratio) + 10% mass ratio CsFSI additive as electrolyte.

[0048] The battery was assembled in a glove box (water and oxygen values less than 0.5 ppm), and the temperature was maintained at 80 °C (range can be 80-150 °C) during assembly. The mass of the molten salt electrolyte was 70 mg. The separator was a glass fiber separator. The assembly was a carbon-coated Sb || Na3Fe2(SO4)3 battery, and the cycling was performed at 80 °C. The electrochemical performance is shown in Table 1, including operating voltage, energy density, cycle life, operating temperature.

[0049] Table 1: Molten salt sodium-ion batteries with different anodes, electrolytes, micron metal and molten salt electrolyte cathodes Example Test parameter Average operating voltage (V) Energy density (Wh / kg) Operating temperature (°C) Cycle life (%) Example 1 Micro-Sb || Na3Fe2(SO4)3 NaFSI: KFSI 3.0 120 80 90 (100 cycles) Example 2 Micro-Sb || Na3V2(PO4)3 NaFSI: KFSI 2.6 100 80 95 (100 cycles) Example 3 <![CDATA[微米Sb||Na4Fe3(PO4)2(P2O7)NaFSI: KFSI]]> 2.2 90 80 94 (100 cycles) Example 4 Micro-Sb || Na3Fe2(SO4)3 NaFSI: KFSI 10% mass ratio CsFSI additive 3.0 120 80 96 (100 cycles) Example 5 Micron Sb-Sn alloy || Na3Fe2(SO4)3 NaFSI: KFSI 10% mass CsFSI additive 3.2 130 80 93 (100 cycles) Example 6 Micron carbon-coated Sb || Na3Fe2(SO4)3 NaFSI: KFSI 10% mass ratio CsFSI additive 3.0 120 80 95 (100 cycles)

[0050] The above description is only the preferred embodiment of the present application, not to limit the scope of the present application, the above embodiment of the present application can also be made various changes. That is, according to the application of the claims and the content of the specification of the simple, equivalent changes and modifications made in accordance with the contents of the present application, all fall within the scope of the claims of the present application. The present application is not described in detail, all are conventional technical content.

Claims

1. A sodium ion battery based on a micron metal negative electrode and a molten salt electrolyte, characterized in that: The sodium ion battery includes a micron metal negative electrode and a molten salt electrolyte, wherein the micron metal negative electrode is a micron-sized Sb element, Sb alloy, Sb compound or Sb complex, and the molten salt electrolyte includes NaFSI and KFSI.

2. The sodium ion battery according to claim 1, characterized in that The size of the micron metal negative electrode particles is between 1 micron and 20 microns.

3. The sodium ion battery according to claim 1, characterized in that The micron metal negative electrode is micron Sb, micron Sb-Sn alloy, micron Sb-Bi alloy, micron SbO2, micron SbS2 or carbon-coated micron Sb.

4. The sodium ion battery according to claim 1, characterized in that The molar ratio of NaFSI to KFSI is 56:

44.

5. The sodium ion battery according to claim 1, characterized in that Molten salt electrolytes also include CsFSI.

6. The sodium ion battery according to claim 5, characterized in that The mass percentage of CsFSI in the molten salt electrolyte is 5%-15%.

7. The sodium ion battery according to claim 1, characterized in that The sodium ion battery also includes a positive electrode.

8. The sodium ion battery according to claim 7, characterized in that The positive electrode is Na3Fe2(SO4)3, Na3V2(PO4)3, Na4Fe3(PO4)2(P2O7), Prussian blue / white or layered oxide.

9. The sodium ion battery according to claim 1, characterized in that The sodium ion battery also includes a diaphragm, wherein the diaphragm is a PP diaphragm, a modified PP diaphragm, a modified PE diaphragm, a glass fiber diaphragm or a polyimide diaphragm.

10. The sodium ion battery according to claim 1, characterized in that The operating temperature of sodium-ion batteries is between 70-150°C.