High-safety high-entropy electrolyte, preparation method and battery

Abstract

The application relates to a high-safety high-entropy electrolyte, a preparation method and a battery, the high-entropy electrolyte is in a liquid state at room temperature and is composed of a sodium salt and an organic solvent, and the high-entropy electrolyte can form a high-thermal-stability solid electrolyte interface layer on the surface of an electrode during normal charging and discharging of the battery. The high-entropy electrolyte is applied to a sodium battery, when the battery is normally cycled, the high-entropy electrolyte can form a high-thermal-stability solid electrolyte interface layer on the electrode side, can meet the stable long cycle life of the battery, can ensure that a full state-of-charge battery shows a low heat release rate under thermal abuse conditions, has no serious combustion and explosion phenomenon, meanwhile, the high-entropy electrolyte can be adapted to various sodium battery systems, can meet the normal operation requirements of a prepared battery cell system of the sodium battery. In addition, the preparation process of the high-entropy electrolyte is simple, raw materials are easy to obtain and low in cost, the long cycle life of the battery can be effectively realized, and the safety of the battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte technology, and relates to a highly safe high-entropy electrolyte, its preparation method, and a battery. Background Technology

[0002] Sodium batteries, as a promising next-generation energy storage technology to replace lithium batteries, have attracted widespread attention in recent years. Compared to lithium resources, sodium resources are abundant and widely distributed, offering greater economic viability and sustainability, thus making sodium batteries an important candidate for future energy storage systems. The electrolyte, a key component of sodium batteries, plays a crucial role in ion conduction, interface stability, and overall battery operating speed. However, traditional organic liquid electrolytes pose risks of flammability and explosion, and have poor thermal stability. Under high-temperature conditions, organic liquid electrolytes are prone to pyrolysis, which adversely affects the battery's cycle stability. Furthermore, the solid electrolyte interface layer formed on the electrode surface of traditional organic liquid electrolytes is typically rough, easily undergoing thermal decomposition under high temperatures. This leads to direct contact between the electrolyte and the sodium-modified negative electrode, generating heat. Simultaneously, the release of reducing gases further exacerbates the exothermic reaction, significantly increasing the risk of thermal runaway and jeopardizing the battery's safety and stability. Therefore, the thermal safety of the electrolyte is a crucial factor determining the overall performance of sodium batteries.

[0003] Researchers have proposed several strategies for achieving a high-safety electrolyte for sodium batteries, along with its preparation methods and applications:

[0004] For example, the literature (Angew. Chem. Int. Ed. 2022, 61, e202205045; J. Am. Chem. Soc. 2024, 146, 15751.) has increased the thermal decomposition temperature of electrolytes by using high-concentration or locally high-concentration electrolytes, thereby reducing the volatility and flammability of the electrolytes themselves and enhancing the thermal safety of the electrolyte system. However, the viscosity and cost still need to be balanced, which hinders further practical energy storage applications.

[0005] Patents such as CN104900879B introduce phosphate ester solvents or flame-retardant additives to achieve non-flammable electrolytes. However, this system improves the safety performance of sodium batteries at the expense of battery electrochemical performance.

[0006] As demonstrated in the literature (Chem.Eng.J.2021,425,130612.), the excellent thermal stability, wide electrochemical window, and low flammability of ionic liquid electrolytes can improve the safety and electrochemical performance of sodium batteries. However, their high viscosity and high cost remain major obstacles to their widespread application.

[0007] Solid-state electrolytes possess non-flammability and excellent thermal stability, capable of withstanding high temperatures without decomposition, significantly reducing the risk of fire and explosion. Furthermore, solid-state electrolytes maintain excellent structural integrity under various harsh conditions. For example, the literature (Adv. Energy Mater. 2017, 7, 1601196.) demonstrates that designing solid-state electrolytes with high thermal stability and high mechanical strength can minimize internal short circuits and other mechanical abuse that could lead to thermal runaway. However, the poor electrode-electrolyte interface compatibility and low room-temperature ionic conductivity of solid-state electrolytes hinder the development and application of solid-state sodium batteries.

[0008] As demonstrated in the literature (J. Power Sources 2019, 423, 137; ACS Energy Lett. 2024, 9, 4111; CN114156543A; CN113921907A, etc.), a stable solid electrolyte interface layer is formed on the electrode surface by adding film-forming additives or adjusting the electrolyte formulation. A stable solid electrolyte interface layer is crucial for the performance and safety of sodium batteries, effectively suppressing side reactions, delaying battery degradation, and improving battery cycle stability and safety. However, traditional organic liquid electrolytes form a solid electrolyte interface layer rich in organic components on the electrode surface, which has poor thermal stability and is prone to decomposition at high temperatures, resulting in a double decrease in battery cycle stability and safety. Therefore, optimizing the electrolyte composition to form a solid electrolyte interface layer with high thermal stability is an important research direction for achieving a balance between the electrochemical performance and safety of sodium batteries.

[0009] Recent studies have shown that high-entropy electrolytes, formed by introducing multiple salt components, can alter the solvation structure of the electrolyte, thereby stabilizing the electrode-electrolyte interface phase. For example, the high-entropy electrolyte prepared in the literature (Adv. Mater. 2023, 35, 2210677.) significantly improves the cycle life and rate performance of batteries and holds promise for expanding high and low temperature applications. This research provides a novel research approach for the design and development of next-generation high-energy-density and high-safety sodium batteries.

[0010] High-entropy electrolyte systems, as reported so far, can significantly improve the electrochemical performance of batteries due to the synergistic effect of their multi-component components. However, the complexity of high-entropy electrolyte components and the interactions between them are not yet fully understood. Under high-temperature or extreme conditions, they may exhibit pyrolysis behavior or adverse side reactions with electrode materials, thereby affecting battery stability and safety and increasing the risk of thermal runaway. Summary of the Invention

[0011] The purpose of this invention is to provide a highly safe high-entropy electrolyte, its preparation method, and a battery that can balance the electrochemical performance and thermal safety performance of sodium batteries.

[0012] The objective of this invention can be achieved through the following technical solutions:

[0013] In a first aspect, the present invention provides a highly safe high-entropy electrolyte, which is liquid at room temperature and is composed of sodium salt and organic solvent. The high-entropy electrolyte contains solvation structural clusters involving multiple anions. During normal charging and discharging of the battery, these clusters preferentially decompose on the electrode surface due to their higher redox properties, forming a solid electrolyte interface layer rich in inorganic matter and with high thermal stability.

[0014] Furthermore, the organic solvent is two or more of the following: propylene carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, triethyl phosphate, trimethyl phosphate, methyl ethyl carbonate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and 1,3-dioxolane.

[0015] Furthermore, the sodium salt is selected from any five or more of the following: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalateborate, sodium bis(oxalateborate), sodium tetrafluoroborate, sodium hexafluorophosphate, sodium perchlorate, sodium nitrate, and sodium trifluoromethanesulfonate. Known sodium salts applicable to sodium-ion battery electrolytes are collected. Combining multiple different types of sodium salts in the electrolyte can significantly increase the system's disorder. When the entropy value reaches a certain level, this high-entropy state can enhance the chemical and thermodynamic stability of the electrolyte through the synergistic effect of multiple components, enabling it to operate stably over a wider temperature and voltage window. This avoids unstable phenomena such as electrolyte decomposition and salt precipitation, thus achieving various aspects of battery performance.

[0016] Furthermore, the total concentration of the sodium salt in the high-entropy electrolyte is 0.8–1.2 mol / L.

[0017] Furthermore, different sodium salt components are added in equimolar amounts.

[0018] Furthermore, the water content in the high-entropy electrolyte is less than 20 ppm.

[0019] In a second aspect, the present invention also provides a method for preparing a highly safe high-entropy electrolyte, wherein sodium salt and organic solvent are mixed uniformly under an inert atmosphere to obtain the high-entropy electrolyte.

[0020] In a third aspect, the present invention also provides a battery that uses a high-safety, high-entropy electrolyte as described above as the electrolyte.

[0021] Furthermore, the battery is a sodium-ion battery, a sodium metal battery, or a sodium battery without a negative electrode.

[0022] Furthermore, in the cell system used in the battery, sodium nickel iron manganese oxide, sodium copper iron manganese oxide, sodium vanadium phosphate, sodium iron sulfate, sodium iron pyrophosphate, or Prussian blue are used as positive electrode materials, with no negative electrode, or one of hard carbon, soft carbon, titanium-based materials, alloy materials, metal oxides and sulfides, or sodium metal is used as the negative electrode material.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The designed high-entropy electrolyte is liquid at room temperature and has high ionic conductivity. The unique advantage of this application is that it can meet the normal charge and discharge requirements of sodium-ion batteries, sodium metal full batteries and negative electrode-free sodium battery systems; in addition, this invention achieves a good balance between the electrochemical performance and thermal safety performance of sodium batteries.

[0025] (2) Unlike traditional artificial solid-liquid interface layers, it can form a solid electrolyte interface layer rich in inorganic components on the electrode surface in an electrolyte system containing multiple salt components, which is difficult to thermally decompose at high temperatures.

[0026] (3) The presence of an inorganic solid electrolyte interface protective layer effectively increases the onset temperature during the thermal runaway process of sodium battery, significantly reduces the temperature rise rate during the thermal runaway process, minimizes the heat accumulation of sodium battery during the thermal runaway process, and alleviates the severity of sodium battery thermal runaway.

[0027] (4) Compared with existing electrolytes, the electrolyte in this invention has a conventional concentration, low solvent components and sodium salt, low usage in the electrolyte, and no special requirements for the use environment.

[0028] (5) The electrolyte system can achieve a low heat release rate during the thermal runaway process of sodium batteries, ensuring safe operation of the batteries; the batteries using the electrolyte system in this application have excellent room temperature long cycle performance, reliable safety performance, can reduce the temperature rise rate during thermal runaway, slow down the severity of thermal runaway events, and have no obvious combustion or explosion phenomena. Attached Figure Description

[0029] Figure 1 The graph shows the cycle performance of sodium batteries prepared using the high-entropy electrolyte and the conventional electrolyte in Example 1.

[0030] Figure 2 Accelerated calorimetry test diagram of a fully charged sodium battery prepared with the high-entropy electrolyte of Example 1;

[0031] Figure 3 A photograph of a sodium battery prepared with a high-entropy electrolyte in Example 1 after thermal runaway;

[0032] Figure 4The cycling performance diagrams show the sodium batteries prepared using the high-entropy electrolyte of Example 1 and the electrolyte of Comparative Example 1.

[0033] Figure 5 Accelerated calorimetry test diagram of a fully charged sodium battery prepared using the electrolyte of Comparative Example 1.

[0034] Figure 6 The cycling performance diagrams show the sodium batteries prepared using the high-entropy electrolyte of Example 1 and the electrolyte of Comparative Example 2. Figure 7 The graph shows the cycle performance of sodium batteries prepared using the high-entropy electrolyte of Example 1 and the electrolyte of Comparative Example 3. Detailed Implementation

[0035] 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.

[0036] To achieve a balance between electrochemical performance and thermal safety performance of sodium batteries, this invention provides a highly safe high-entropy electrolyte, which is prepared by uniformly mixing any five or more sodium salts with ester or ether organic solvents in an inert argon atmosphere.

[0037] In some specific embodiments, the organic solvent is composed of two or more of the following: propylene carbonate, ethylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, triethyl phosphate, trimethyl phosphate, methyl ethyl carbonate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and 1,3-dioxolane.

[0038] In some specific embodiments, the sodium salt is composed of any five or more of the following: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium di(oxalate borate), sodium tetrafluoroborate, sodium hexafluorophosphate, sodium perchlorate, sodium nitrate, and sodium trifluoromethanesulfonate. Preferably, different sodium salts are added in equimolar amounts. Furthermore, the total concentration of all sodium salts is 0.8–1.2 mol / L, more preferably 1.0 mol / L.

[0039] The present invention can be further understood from the following embodiments, but the present invention is not limited to the following embodiments.

[0040] In the following embodiments, hard carbon and NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was purchased from Shenzhen Kejing Zhida Technology Co., Ltd., the hard carbon model is Type 2 Kuraray, code 02009802; NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3The O2 model is MS-XN-33S, code 01009401. Figure 1 The conventional electrolyte was purchased from Duoduo Chemical Reagent Network, catalog number NC-004. The formula is sodium perchlorate dissolved in ethylene carbonate / propylene carbonate at a volume ratio of 1:1 and fluoroethylene carbonate is added at a total integral of 5%. The electrolyte concentration is 1 mol / L.

[0041] Unless otherwise specified, all other raw materials or processing techniques are commercially available materials or conventional processing techniques in the field.

[0042] Example 1:

[0043] A 1:1 volume ratio of ethylene carbonate / ethylene glycol dimethyl ether was prepared. The sodium salts were a mixture of six compounds: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component was 0.167 mol / L, and the concentration of the mixed electrolyte was 1.0 mol / L. At room temperature, this electrolyte system was used with hard carbon as the negative electrode, NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell testing with O2 as the positive electrode revealed that the battery achieved a coulombic efficiency of 88.46% in the first cycle, a cycle life of 400 cycles, and a capacity retention of >80%. Figure 1 As shown.

[0044] Figure 2 and Figure 3 The results showed that when thermal abuse tests were conducted using an accelerated calorimeter (ARC), the sodium battery's thermal runaway initiation temperature was 161.92℃, with a low temperature rise rate throughout the test and no serious fire or explosion events, demonstrating high safety performance.

[0045] Example 2:

[0046] A 1:1 volume ratio of ethylene carbonate / ethylene glycol dimethyl ether was prepared. The sodium salt was a mixture of five components: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, and sodium hexafluorophosphate. Each component had a concentration of 0.2 mol / L, and the total concentration of the mixed electrolyte was 1.0 mol / L. At room temperature, this electrolyte system was used with hard carbon as the negative electrode, NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode

[0047] When subjected to thermal abuse testing using an accelerated calorimeter (ARC), the sodium battery exhibits a low rate of temperature rise throughout the thermal runaway process, with no serious fire or explosion incidents, demonstrating high safety performance.

[0048] Example 3:

[0049] A 1:1 volume ratio of ethylene carbonate / ethylene glycol dimethyl ether was prepared. The sodium salts were a mixture of seven components: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium perchlorate, and sodium nitrate. Each component had a concentration of 0.143 mol / L, and the total concentration of the mixed electrolyte was 1.0 mol / L. At room temperature, this electrolyte system was used with hard carbon as the negative electrode, NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode

[0050] When subjected to thermal abuse testing using an accelerated calorimeter (ARC), the sodium battery exhibits a low rate of temperature rise throughout the thermal runaway process, with no serious fire or explosion incidents, demonstrating high safety performance.

[0051] Example 4:

[0052] A 1:1 volume ratio of ethylene carbonate / ethylene glycol dimethyl ether was prepared. The sodium salts were a mixture of eight compounds: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium perchlorate, sodium nitrate, and sodium trifluoromethanesulfonate. Each component had a concentration of 0.125 mol / L, and the total concentration of the mixed electrolyte was 1.0 mol / L. At room temperature, this electrolyte system was used with hard carbon as the negative electrode, NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode

[0053] When subjected to thermal abuse testing using an accelerated calorimeter (ARC), the sodium battery exhibits a low rate of temperature rise throughout the thermal runaway process, with no serious fire or explosion incidents, demonstrating high safety performance.

[0054] Example 5:

[0055] Prepare a 1:1 volume ratio of ethylene carbonate / ethylene glycol dimethyl ether mixed solution. The sodium salt is a mixture of nine sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium perchlorate, sodium nitrate, sodium trifluoromethanesulfonate, and sodium di(oxalate borate). The concentration of each component is 0.111 mol / L, and the total concentration of the mixed electrolyte is 1.0 mol / L.

[0056] This electrolyte system was used with hard carbon as the negative electrode, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode

[0057] Example 6:

[0058] Prepare a mixed solution of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate in a volume ratio of 1:1:1. The sodium salt is a mixture of six sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component is 0.167 mol / L, and the total concentration of the mixed electrolyte is 1.0 mol / L.

[0059] This electrolyte system was used with hard carbon as the negative electrode, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode

[0060] Example 7:

[0061] A mixed solution of ethylene glycol dimethyl ether / ethylene glycol diethyl ether / 1,3-dioxolane with a volume ratio of 1:1:1 was prepared. The sodium salt was a mixture of six components: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component was 0.167 mol / L, and the total concentration of the mixed electrolyte was 1.0 mol / L.

[0062] This electrolyte system was used with hard carbon as the negative electrode, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test using O2 as the positive electrode. Example 8:

[0063] A mixed solution of trimethyl phosphate and ethylene glycol dimethyl ether with a volume ratio of 1:1 was prepared. The sodium salt was a mixture of six components: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component was 0.167 mol / L, and the total concentration of the mixed electrolyte was 1.0 mol / L.

[0064] The electrolyte system was used to test a full cell with hard carbon as the negative electrode and sodium vanadium phosphate as the positive electrode.

[0065] Example 9:

[0066] A mixed solution of propylene carbonate / ethylene glycol dimethyl ether / fluoroethylene carbonate with a volume ratio of 1:1:1 was prepared. The sodium salt was a mixture of six components: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component was 0.167 mol / L, and the total concentration of the mixed electrolyte was 1.0 mol / L.

[0067] The electrolyte system was used to test a full cell with hard carbon as the negative electrode and sodium iron phosphate pyrophosphate as the positive electrode.

[0068] Example 10:

[0069] A mixed solution of ethylene carbonate / ethylene glycol dimethyl ether / fluoroethylene carbonate with a volume ratio of 1:1:1 was prepared. The sodium salt was a mixture of six components: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component was 0.167 mol / L, and the total concentration of the mixed electrolyte was 1.0 mol / L.

[0070] The electrolyte system was used for full-cell testing with hard carbon as the negative electrode and a Prussian blue analogue as the positive electrode.

[0071] Example 11:

[0072] Prepare a mixed solution of ethylene carbonate / ethylene glycol dimethyl ether with a volume ratio of 1:1. The sodium salt is a mixture of six sodium salts: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component is 0.167 mol / L, and the total concentration of the mixed electrolyte is 1.0 mol / L.

[0073] This electrolyte system was used with soft carbon as the negative electrode, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode.

[0074] Example 12:

[0075] Prepare a mixed solution of propylene carbonate / ethylene carbonate / fluoroethylene carbonate in a volume ratio of 1:1:1. The sodium salt is a mixture of six sodium salts: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component is 0.167 mol / L, and the total concentration of the mixed electrolyte is 1.0 mol / L.

[0076] The electrolyte system was used for full cell testing with Na2Ti3O7 as the negative electrode and sodium vanadium phosphate as the positive electrode.

[0077] Example 13:

[0078] Prepare a mixed solution of ethylene carbonate / ethylene glycol dimethyl ether with a volume ratio of 1:1. The sodium salt is a mixture of six sodium salts: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component is 0.167 mol / L, and the total concentration of the mixed electrolyte is 1.0 mol / L.

[0079] This electrolyte system is used with red phosphorus or black phosphorus as the negative electrode, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode.

[0080] Example 14:

[0081] Prepare a mixed solution of ethylene carbonate / ethylene glycol dimethyl ether with a volume ratio of 1:1. The sodium salt is a mixture of six sodium salts: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component is 0.167 mol / L, and the total concentration of the mixed electrolyte is 1.0 mol / L.

[0082] This electrolyte system was used with sodium metal as the negative electrode, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode.

[0083] Example 15:

[0084] Prepare a mixed solution of ethylene carbonate / ethylene glycol dimethyl ether with a volume ratio of 1:1. The sodium salt is a mixture of six sodium salts: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium hexafluorophosphate, and sodium perchlorate. The concentration of each component is 0.167 mol / L, and the total concentration of the mixed electrolyte is 1.0 mol / L.

[0085] This electrolyte system was used with copper foil as the negative electrode current collector, NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 Full cell test with O2 as the positive electrode.

[0086] Examples 1-15 show that when a sodium battery using a high-entropy electrolyte is cycled normally, a solid electrolyte interface layer rich in inorganic components and with high thermal stability is formed on the electrode surface. This ensures the long cycle life and other electrochemical performance of the sodium battery, while significantly increasing the decomposition temperature of the electrode-electrolyte interface layer during thermal runaway, reducing the temperature rise rate throughout the thermal runaway process, reducing heat accumulation, and preventing serious combustion and explosion events, thus ensuring high safety performance.

[0087] Comparative Example 1:

[0088] The electrolyte system was largely the same as in Example 1, except that the sodium salt was replaced with an equimolar amount of sodium perchlorate, and the electrolyte concentration was 1.0 mol / L. This electrolyte system was used with hard carbon as the negative electrode, NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 Full-cell testing with O2 as the positive electrode revealed that after 150 cycles, the capacity retention rate dropped below 80%. Figure 4 As shown.

[0089] When subjected to thermal abuse testing using an accelerated calorimeter (ARC), the sodium battery exhibited a thermal runaway initiation temperature of 52.386°C, a high rate of temperature rise throughout the test, and poor safety. Figure 5 .

[0090] Comparative Example 2:

[0091] Compared to Example 1, most aspects were the same, except that the sodium perchlorate concentration was increased to 0.5 mol / L, while the other five salts were all at 0.1 mol / L, resulting in a total electrolyte concentration of 1.0 mol / L. This electrolyte system was used with hard carbon as the negative electrode, NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 Full-cell testing with O2 as the positive electrode revealed that after 60 cycles, the capacity retention rate dropped below 80%. Figure 6 As shown.

[0092] Comparative Example 3:

[0093] The process is largely the same as in Example 1, except that the organic solvent system is replaced with a single organic solvent, ethylene glycol dimethyl ether, and the electrolyte concentration is 1.0 mol / L. This electrolyte system is used with hard carbon as the negative electrode, NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 Full-cell testing using O2 as the positive electrode revealed that after 50 cycles, the capacity retention rate dropped below 80%. Figure 7 As shown.

[0094] 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 highly safe, high-entropy electrolyte, characterized in that, It is liquid at room temperature and is composed of various sodium salts and organic solvents. The high-entropy electrolyte can form a solid electrolyte interface layer rich in inorganic matter and with high thermal stability during normal charging and discharging of the battery. It can increase the onset temperature during the thermal runaway process of sodium battery, reduce the temperature rise rate during the thermal runaway process, and alleviate the severity of the thermal runaway of sodium battery. The organic solvent is a mixed solution of ethylene carbonate / ethylene glycol dimethyl ether in a volume ratio of 1:1, or a mixed solution of ethylene glycol dimethyl ether / ethylene glycol diethyl ether / 1,3-dioxolane in a volume ratio of 1:1:1, or a mixed solution of propylene carbonate / ethylene glycol dimethyl ether / fluoroethylene carbonate in a volume ratio of 1:1:1, or a mixed solution of ethylene carbonate / ethylene glycol dimethyl ether / fluoroethylene carbonate in a volume ratio of 1:1:

1. The sodium salt is selected from any five or more of the following: sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium difluorooxalate borate, sodium di(oxalate borate), sodium tetrafluoroborate, sodium hexafluorophosphate, sodium perchlorate, sodium nitrate, and sodium trifluoromethanesulfonate. Different sodium salt components are added in equimolar amounts. The concentration of the sodium salt in the high-entropy electrolyte is 0.8~1.2 mol / L.

2. The high-safety, high-entropy electrolyte according to claim 1, characterized in that, The water content in the high-entropy electrolyte is less than 20 ppm.

3. The method for preparing a highly safe, high-entropy electrolyte as described in claim 1 or 2, characterized in that, The high-entropy electrolyte is obtained by uniformly mixing sodium salt and organic solvent under an inert atmosphere.

4. A battery, characterized in that, The battery uses a high-safety, high-entropy electrolyte as described in claim 1 or 2 as the electrolyte.

5. The battery according to claim 4, characterized in that, The battery is a sodium-ion battery, a sodium metal battery, or a sodium battery without a negative electrode.

6. The battery according to claim 4, characterized in that, The battery cell system uses sodium nickel iron manganese oxide, sodium copper iron manganese oxide, sodium vanadium phosphate, sodium iron sulfate, sodium iron pyrophosphate, or Prussian blue as the positive electrode material, with no negative electrode, or uses one of hard carbon, soft carbon, titanium-based materials, alloy materials, metal oxides and sulfides, or sodium metal as the negative electrode material.

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