Composite additive and sodium sulfoxyl chloride battery electrolyte and application
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QINGDAO INST OF BIOENERGY & BIOPROCESS TECH CHINESE ACADEMY OF SCI
- Filing Date
- 2026-04-16
- Publication Date
- 2026-06-19
Smart Images
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Figure SMS_5
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to a composite additive and a sodium thionyl chloride (Na / SOCl2) electrolyte and its application. Background Technology
[0002] Sodium thionyl chloride (Na / SOCl2) batteries, as a high-capacity, high-voltage electrochemical energy storage system, possess advantages such as high energy density, low self-discharge rate, and wide operating temperature range, and are expected to be widely used in military equipment, spacecraft, oil well logging, and long-life power supplies. Traditional sodium thionyl chloride batteries generally use sodium tetrachloroaluminate (NaAlCl4) dissolved in SOCl2 as the electrolyte. However, this system suffers from the problem of SOCl2's strong corrosiveness and high reactivity leading to the formation of an unstable passivation layer on the sodium anode surface, which in turn causes increased interfacial impedance, dendrite formation, capacity decay, and safety hazards.
[0003] Current research has attempted to regulate the interfacial reaction behavior of sodium anodes by introducing functional additives, aiming to construct stable interfacial films and suppress side reactions. However, in SOCl2 systems, traditional additives often face problems such as polarity mismatch, poor solubility, easy crystallization, and phase separation. Furthermore, their decomposition products are not compatible with the SOCl2 system, often leading to a loose, layered solid electrolyte interphase (SEI) film structure and a lack of long-term stability. Therefore, achieving high solubility and interfacial stability of additives in SOCl2 systems remains a major challenge in the development of sodium thionyl chloride batteries. Summary of the Invention
[0004] This invention provides a composite additive, a sodium thionyl chloride (Na / SOCl2) battery electrolyte, and its application.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A composite additive, comprising a sodium salt and a cosolvent, both containing a sulfonamide structure; wherein the sulfonamide structure is a -SO2-N- structural unit.
[0006] Both the sodium salt and the co-solvent contain -SO2-N- structural units, which can form stable dipole-dipole interactions and ordered molecular assembly in solution.
[0007] The sodium salt is sodium bis(fluorosulfonyl)imide (NaFSI) and / or sodium bis(trifluoromethanesulfonyl)imide (NaTFSI). The cosolvents are N,N-dimethylfluorosulfonamide (DMFSA) and / or N,N-dimethyltrifluoromethanesulfonamide (DMTMSA).
[0008] The sodium salt, sodium bis(trifluoromethanesulfonylimide), is shown in Formula 1: Formula 1 The sodium salt difluorosulfonylimide is shown in Formula 2: Formula 2 The co-solvent N,N-dimethyltrifluoromethanesulfonamide is shown in Formula 3: Formula 3 The cosolvent N,N-dimethylfluorosulfonamide is shown in Formula 4: Formula 4.
[0009] As can be seen from the above, sodium salts and cosolvents have similar sulfonylimide skeletons, which can achieve synergistic dissolution between molecules and synergistic assembly at the interface.
[0010] An application of the aforementioned composite additive, specifically its use in the preparation of sodium thionyl chloride battery electrolyte.
[0011] A sodium thionyl chloride battery electrolyte contains a base salt and a main solvent; the electrolyte contains the aforementioned composite additive, wherein the final concentration of sodium salt in the composite additive in the sodium thionyl chloride battery electrolyte is 0.05-0.25 M, and the mass fraction of the co-solvent is 1%-10%.
[0012] The sodium thionyl chloride battery electrolyte consists of a base salt, a main solvent, and composite additives; wherein the base salt is sodium tetrachloroaluminate (NaAlCl4), and its final concentration in the electrolyte system is 1-4 M (preferably 2.0-3.0 M); the main solvent is thionyl chloride (SOCl2), which serves as the main solvent in the system.
[0013] The electrolyte forms a double-layer SEI film on the surface of the sodium negative electrode. The inner layer is a dense NaF inorganic layer, and the outer layer is a flexible organic protective layer containing S, O, and N, thereby inhibiting sodium dendrite growth and side reactions.
[0014] A method for preparing the sodium thionyl chloride battery electrolyte, a) The main solvent is dried using molecular sieves in an inert atmosphere to remove trace amounts of moisture; b) Dissolve the base salt in the solvent after the above treatment at room temperature; c) Add the composite additive to the solution obtained in step b), stir and mix until fully dissolved to obtain the electrolyte.
[0015] An application of the sodium thionyl chloride battery electrolyte, wherein the electrolyte is used as an electrolyte in a sodium thionyl chloride battery.
[0016] A sodium thionyl chloride battery includes a conductive carbon positive electrode, a sodium metal negative electrode, a separator, and an electrolyte, wherein the electrolyte is the electrolyte solution between the positive and negative electrodes.
[0017] The positive electrode is one of acetylene black, Ketjen black, Super P, activated carbon, graphene, carbon nanotubes, carbon cloth, carbon paper, and carbon felt.
[0018] The diaphragm is a glass fiber diaphragm, a ceramic-coated diaphragm, a polymer microporous membrane (such as PE, PP or multilayer composite membrane) or a composite diaphragm.
[0019] The battery is at 1 mA cm -2 The discharge capacity retention rate after 100 cycles at current density is not less than 90%.
[0020] The battery is suitable for high specific energy storage scenarios and exhibits excellent cycle stability and safety.
[0021] The battery has a button, column, or stacked structure.
[0022] The advantages and positive effects of this invention are: The composite additive of this invention uses sodium salts and co-solvents that both contain -SO2-N- structural units, enabling stable dipole-dipole interactions and ordered molecular assembly in solution. Further, the composite additive is used to prepare a sodium thionyl chloride battery electrolyte. By introducing a composite additive of sodium salts and co-solvents both possessing sulfonylimide structures, a highly compatible organic-inorganic composite SEI film is constructed in situ on the sodium metal anode surface using intermolecular synergistic effects and self-assembly behavior. This effectively suppresses side reactions between sodium and SOCl2, improves the stability of the electrode interface and the homogeneity of the electrolyte, and ultimately significantly improves the cycle life and safety performance of the battery. Specifically: 1. This invention relates to a composite additive based on a sulfonylimide structure applied to thionyl chloride battery electrolytes. Both the composite additive and the SOCl2 solvent share common polar groups, exhibiting high electronic structural compatibility. This results in excellent solubility and chemical stability in the SOCl2 solvent environment, significantly reducing the risk of crystallization and phase separation of the sodium salt additive at high concentrations. Furthermore, due to the similar -SO2-N- structural units of the sodium salt and co-solvent in the composite additive, dipole-dipole interactions are more easily formed during intermolecular interactions, leading to ordered molecular assembly. Based on their molecular structural homology, this type of self-assembled solvation structure can construct a bilayer SEI film on the sodium anode surface: the inner layer is a dense inorganic NaF phase formed from sodium salt decomposition products, while the outer layer is a flexible organic protective layer composed of S, O, and N organic groups from the co-solvent decomposition products. This highly compatible organic-inorganic composite SEI film not only significantly improves the mechanical stability of the interface but also effectively suppresses side reactions between sodium metal and thionyl chloride solvent, blocking the corrosion of sodium metal by thionyl chloride. Therefore, the sodium thionyl chloride battery electrolyte system composed of the above-mentioned composite additives can achieve high-efficiency interfacial compatibility with both the sodium metal anode and the thionyl chloride cathode, thereby significantly improving the cycle stability and safety of the sodium-thionyl chloride battery.
[0023] 2. The composite additive proposed in this invention can construct a double-layer SEI film on the sodium anode surface: the inner layer is a dense inorganic NaF phase formed by sodium salt decomposition products, while the outer layer is a flexible organic protective layer composed of S, O, and N organic groups from the co-solvent decomposition products. This highly compatible organic-inorganic composite SEI film not only significantly improves the mechanical stability of the interface but also effectively inhibits the side reactions between sodium metal and thionyl chloride solvent, blocking the corrosion of sodium metal by thionyl chloride. Therefore, the thionyl chloride electrolyte system composed of the aforementioned composite additive can achieve highly efficient interfacial compatibility with both the sodium metal anode and the thionyl chloride cathode, thereby significantly improving the cycle stability and safety of the sodium-thionyl chloride battery.
[0024] 3. This invention can effectively suppress the growth of sodium dendrites, significantly improve the deposition / stripping stability of sodium metal anodes, and extend the cycle life of sodium thionyl chloride batteries.
[0025] 4. The electrolyte preparation process described in this invention is simple, requires little additives and the types of additives are adjustable, and has high cost controllability and process feasibility, making it easy to scale up production and promote application. Attached Figure Description
[0026] Figure 1 This is a schematic diagram illustrating the synergistic solvation mechanism of sodium salt and cosolvent.
[0027] Figure 2This is a comparison chart of the battery cycle performance of Example 1 and Comparative Example 1. Detailed Implementation
[0028] The following examples further illustrate specific embodiments of the present invention. It should be noted that the specific embodiments described herein are merely for illustration and explanation and are not intended to limit the scope of the present invention.
[0029] To better understand the intent of this invention, the idea and core concept behind the technical solution of this invention will be briefly explained first.
[0030] In sodium thionyl chloride batteries, SOCl2, as a solvent, exhibits strong corrosiveness and high reactivity. When it comes into direct contact with sodium metal, it readily undergoes side reactions, forming a heterogeneous and easily ruptured passivation film on the negative electrode surface. This unstable interfacial film cannot suppress side reactions in the long term, leading to continuous electrolyte consumption, increased interfacial impedance, and ultimately, rapid capacity decay and safety hazards. Therefore, the stability of the negative electrode interface remains a major challenge for the long-term cycling of sodium thionyl chloride batteries.
[0031] While the direct reaction between sodium metal and SOCl2 cannot be completely avoided, the SEI film formed at the interface can be designed to possess both a dense inorganic layer and a flexible organic layer. This would both block the continuous erosion of sodium by SOCl2 and inhibit the growth of sodium dendrites, effectively improving the stability of the interface and the long-cycle performance of the battery. Therefore, the key lies in introducing a class of composite additives with strong structural matching and compatibility of decomposition products to synergistically regulate the composition and physical properties of the SEI at the molecular level.
[0032] Based on this, this invention proposes utilizing the sulfonamide structural characteristics between sodium salts (NaFSI or NaTFSI) and co-solvents (DMFSA or DMTMSA) to promote self-assembly through intermolecular dipole-dipole interactions, thereby achieving high solubility and uniform distribution in the electrolyte. During the electrochemical process, the decomposition of the sodium salt provides F... - A dense NaF inner layer is formed, while the solubilizer decomposition provides S, O, and N organic groups, forming a flexible outer layer. Figure 1 This organic-inorganic composite SEI membrane can simultaneously meet the requirements of chemical stability and mechanical toughness, fundamentally solving the problem of interfacial instability in the sodium thionyl chloride system.
[0033] To further verify the effectiveness of the technical solution of the present invention, the following examples demonstrate the preparation method of the electrolyte of the present invention, as well as its application and electrochemical performance in sodium thionyl chloride batteries.
[0034] The electrochemical performance of sodium thionyl chloride batteries prepared with the electrolytes described in Examples 1-19 and Comparative Examples 1-6 was tested. The test conditions were: at 25 °C, with an electrolyte concentration of 1 mA cm⁻¹. -2 A constant current charge-discharge test was conducted, with a discharge cutoff voltage of 2 V and a charge cutoff capacity of 4 mAh cm⁻¹. -2 .
[0035] Example 1 The electrolyte consists of a main salt, a solvent, and a composite additive; the main salt is NaAlCl4 at a concentration of 2 M, the solvent is SOCl2, the composite additive is NaTFSI at a concentration of 0.2 M, and a co-solvent DMTMSA at a mass fraction of 2 wt% is added.
[0036] The preparation process of the electrolyte is as follows: In an argon-protected glove box, SOCl2 and DMTMSA are pretreated with molecular sieves to remove trace amounts of moisture; then NaAlCl4 is dissolved in SOCl2 and stirred evenly to obtain a NaAlCl4-SOCl2 base solution; on this basis, NaFSI and DMTMSA are added sequentially and stirred continuously until completely dissolved to obtain the target electrolyte.
[0037] A sodium thionyl chloride battery includes a conductive carbon positive electrode, a sodium metal negative electrode, a glass fiber separator, and the electrolyte.
[0038] The battery assembly process is as follows: First, the negative electrode and separator are stacked sequentially, then the electrolyte is injected, followed by the positive electrode and a stainless steel snap-on casing; finally, the battery is encapsulated to obtain a complete battery. For comparative analysis, composite additives were designed in the electrolyte formulations of Examples 1-19 and Comparative Examples 1-6, respectively. The formulation details are shown in Table 1.
[0039] Test results show that this electrolyte operates at approximately 1.2 V vs. Na / Na + Reduction film formation occurred, with an initial coulombic efficiency of 91.0%. (See attached image.) Figure 2 As shown, at 1 mA cm -2 After 50 cycles at the specified expansion ratio, the capacity retention rate reached 94%, which is significantly better than Comparative Example 1 (which had a retention rate of only 65.2%) (see Table 2).
[0040] Example 2 The difference from Example 1 is that the electrolyte formulation is 2.0 M NaAlCl4 + 0.15 M NaTFSI + 2% DMTMSA, otherwise it is the same as Example 1 (see Table 1). The test results (see Table 2) show that the battery has an initial coulombic efficiency of 91.5% and a capacity retention of 95% after 50 cycles.
[0041] Example 3 The difference from Example 1 is that the electrolyte is 2.5 M NaAlCl4 + 0.1 M NaFSI + 0.1 M NaTFSI, and the co-solvent is 2% DMFSA + 2% DMTMSA; the rest is the same as in Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 92.2% and a capacity retention of 95% after 50 cycles (see Table 2).
[0042] Example 4 The difference from Example 1 is that the electrolyte is 4.0 M NaAlCl4 + 0.25 M NaTFSI + 5% DMFSA, otherwise it is the same as Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 93.0% and a capacity retention of 96% after 50 cycles. At a high temperature of 60 °C, the capacity retention still reaches 91% after 50 cycles, indicating that the thermal stability of this invention is significantly superior (see Table 2).
[0043] Example 5 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.05 M NaFSI + 0.05 M NaTFSI + 1% DMFSA + 1% DMTMSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the initial coulombic efficiency is 89.0%, the capacity retention rate is 92% after 50 cycles, and the retention rate is still 84% at -20 °C, indicating that even at low concentrations of additives, the synergistic effect of the two salts + two cosolvents is still significant (see Table 2).
[0044] Example 6 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.1 M NaFSI + 3% DMFSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the initial coulombic efficiency is 90.3%, the capacity retention rate is 93% after 50 cycles, and the capacity retention rate is 85% at -20 °C, which verifies the important role of the cosolvent (see Table 2).
[0045] Example 7 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.2 M NaTFSI + 3% DMTMSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 91.1% and a capacity retention of 94% after 50 cycles, which is good performance (see Table 2).
[0046] Example 8 The difference from Example 1 is that the electrolyte is 4.0 M NaAlCl4 + 0.2 M NaFSI + 2% DMFSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 92.8% and a retention rate of 95% after 50 cycles, indicating that NaFSI can still dissolve well and form a stable SEI film at a high main salt concentration (see Table 2).
[0047] Example 9 The difference from Example 1 is that the electrolyte is 1.5 M NaAlCl4 + 0.2 M NaTFSI + 2% DMTMSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery coulombic efficiency is 88.5% and the retention rate is 91% after 50 cycles, demonstrating good compatibility with low concentration main salt system (see Table 2).
[0048] Example 10 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.1 M NaFSI + 0.1 M NaTFSI + 4% DMFSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 93.2% and still maintains 96% after 50 cycles, showing stable cycling (see Table 2).
[0049] Example 11 The difference from Example 1 is that the electrolyte is 2.5 M NaAlCl4 + 0.15 M NaFSI + 3% DMFSA + 2% DMTSA, otherwise it is the same as Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 93.5% and a retention rate of 90% at -20 °C (see Table 2).
[0050] Example 12 The difference from Example 1 is that the electrolyte is 4.0 M NaAlCl4 + 0.25 M NaTFSI + 10% DMFSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 94.1% and still maintains 95% after 50 cycles, showing stable cycling (see Table 2).
[0051] Example 13 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.05 M NaFSI + 5% DMTMSA, otherwise it is the same as Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 92.0% and a 50-cycle retention rate of 94% (see Table 2).
[0052] Example 14 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.2 M NaFSI + 2% DMFSA + 2% DMTMSA, otherwise it is the same as Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 89.5% and a 50-cycle retention rate of 92% (see Table 2).
[0053] Example 15 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.2 M NaTFSI + 1% DMFSA + 3% DMFSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery's initial coulombic efficiency is 88.7%, and the overall performance is average (see Table 2).
[0054] Example 16 The difference from Example 1 is that the electrolyte is 2.5 M NaAlCl4 + 0.1 M NaFSI + 0.15 M NaTFSI + 4% DMFSA, otherwise it is the same as Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 94.5%, a 50-cycle retention rate of 96%, and good cycle stability (see Table 2).
[0055] Example 17 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.15 M NaFSI + 0.1 M NaTFSI + 2% DMFSA + 2% DMTMSA, otherwise it is the same as Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 93.0% and a capacity retention of 95% after 50 cycles (see Table 2).
[0056] Example 18 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + 0.25 M NaTFSI + 5% DMTMSA, otherwise it is the same as Example 1 (see Table 1). Test results show that the battery has an initial coulombic efficiency of 90.8% and a 50-cycle retention rate of 93% (see Table 2).
[0057] Example 19 The difference from Example 1 is that the electrolyte is 3.0 M NaAlCl4 + 0.2 M NaFSI + 0.05 M NaTFSI + 3% DMFSA + 2% DMTMSA, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 95.2% and a 50-cycle retention rate of 97%, exhibiting the best overall performance (see Table 2).
[0058] Comparative Example 1 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4-SOCl2, without any additives; otherwise, it is the same as Example 1 (see Table 1). Test results show that the battery's initial coulombic efficiency is only 65.2%, capacity decays rapidly, and after 50 cycles, the capacity retention is only 50%, indicating poor stability (see Table 1). Figure 1 (and Table 2).
[0059] Comparative Example 2 The difference from Example 1 is that the electrolyte is 0.1 M NaPF6 dissolved in 2.0 M NaAlCl4-SOCl2, otherwise it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 65.2% and a capacity retention of 50% after 50 cycles, and the addition of NaPF6 has no effect (see Table 2).
[0060] Comparative Example 3 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + SOCl2, and the only additive is NaFSI (0.1 M), otherwise it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 75.0% and a capacity retention of 70% after 50 cycles, indicating that the SEI film is unstable in the absence of co-solvent synergy (see Table 2).
[0061] Comparative Example 4 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + SOCl2, the only additive is NaTFSI (0.1 M), and there is no co-solvent; otherwise, it is the same as Example 1 (see Table 1). The test results show that the battery has an initial coulombic efficiency of 80.0%, but the capacity retention rate is only 77% after 50 cycles, indicating that the SEI film is unstable without the synergistic effect of the co-solvent (see Table 2).
[0062] Comparative Example 5 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + SOCl2, and the only additive is DMFSA (5%), without NaFSI or NaTFSI; otherwise, it is the same as Example 1 (see Table 1). Test results show that the battery's initial coulombic efficiency is only 75.0%, and the capacity retention rate after 50 cycles is 65%, indicating that a single cosolvent cannot effectively control interfacial stability (see Table 2).
[0063] Comparative Example 6 The difference from Example 1 is that the electrolyte is 2.0 M NaAlCl4 + SOCl2, and the only additive is DMTMSA (2%), without NaFSI or NaTFSI; otherwise, it is the same as Example 1 (see Table 1). Test results show that the battery's initial coulombic efficiency is only 80%, and the capacity retention rate after 50 cycles is 75%, indicating that a single cosolvent cannot effectively control interfacial stability (see Table 2).
[0064] Table 1. Formulation of Composite Additives in Electrolyte
[0065] Table 2 Performance test results of sodium thionyl chloride batteries
[0066] In summary, the sulfonylimide-containing composite additive electrolyte system described in this invention exhibits excellent cycling stability at room temperature (capacity retention is mostly above 92%). In particular, Example 19 retains 91% of its capacity at -20 °C and achieves 94% capacity retention after 100 cycles at 60 °C, demonstrating excellent low- and high-temperature adaptability. In Comparative Examples 1-5, the use of non-homogeneous salts or single additives led to SEI membrane failure and a significant decrease in cycling performance, verifying the effectiveness of the technical solution of this invention.
[0067] In summary, both the sodium salt and the co-solvent in the composite additive of this invention contain -SO2-N- structural units, and they can achieve molecular self-assembly through dipole-dipole interactions, constructing a unique homologous solvated sheath structure in the electrolyte. The sodium salt and co-solvent in the solvated structure of the system synergistically decompose on the sodium metal anode surface, constructing a composite SEI film composed of an inner inorganic NaF phase and an outer organic phase containing S, O, and N groups. This composite SEI film effectively suppresses side reactions and the formation of sodium dendrites, improves the deposition / stripping stability of sodium metal, and thus significantly enhances the cycle life and safety of sodium thionyl chloride batteries. The electrolyte system is particularly suitable for sodium thionyl chloride batteries with high specific energy and high safety requirements, and has broad application prospects, especially in military, aerospace, and high-safety energy storage scenarios.
[0068] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A composite additive, characterized in that: The composite additive consists of a sodium salt and a cosolvent, both containing a sulfonamide structure; wherein the sulfonamide structure is a -SO2-N- structural unit.
2. The composite additive according to claim 1, characterized in that: The sodium salt is sodium bis(fluorosulfonyl)imide (NaFSI) and / or sodium bis(trifluoromethanesulfonyl)imide (NaTFSI). The cosolvents are N,N-dimethylfluorosulfonamide (DMFSA) and / or N,N-dimethyltrifluoromethanesulfonamide (DMTMSA).
3. The application of the composite additive containing homologous structures as described in claim 1, characterized in that: The application of the composite additive in the preparation of sodium thionyl chloride battery electrolyte.
4. A sodium thionyl chloride battery electrolyte, comprising a base salt and a main solvent, characterized in that: The electrolyte contains the composite additive as described in claim 1, wherein the final concentration of sodium salt in the composite additive in the electrolyte is 0.05-0.25 M, and the co-solvent accounts for 1%-10% of the mass fraction of the electrolyte.
5. The sodium thionyl chloride battery electrolyte according to claim 4, characterized in that: The sodium thionyl chloride battery electrolyte consists of a base salt, a main solvent, and composite additives; the base salt is sodium tetrachloroaluminate (NaAlCl4), with a final concentration of 1-4 M in the electrolyte system; the main solvent is thionyl chloride (SOCl2).
6. A method for preparing the sodium thionyl chloride battery electrolyte according to claim 4, characterized in that, a) The main solvent is dried using molecular sieves in an inert atmosphere to remove trace amounts of moisture; b) Dissolve the base salt in the main solvent after the above treatment at room temperature; c) Add the composite additive of claim 1 to the solution obtained in step b), stir and mix until fully dissolved to obtain the electrolyte.
7. The application of the sodium thionyl chloride electrolyte according to claim 4, characterized in that: The electrolyte is used as an electrolyte in sodium thionyl chloride batteries.
8. A sodium thionyl chloride battery, comprising a conductive carbon positive electrode, a sodium metal negative electrode, a separator, and an electrolyte, characterized in that, The electrolyte is the electrolyte described in claim 4.
9. The sodium thionyl chloride battery according to claim 8, wherein the positive electrode is one of acetylene black, Ketjen black, Super P, activated carbon, graphene, carbon nanotubes, carbon cloth, carbon paper, and carbon felt.
10. The sodium thionyl chloride battery according to claim 8, wherein the separator is a glass fiber separator, a ceramic coated separator, a polymer microporous membrane, or a composite separator.