High-temperature sodium-ion battery electrolyte and sodium-ion battery
By adding tetra(4-ethynylbenzene)methane and anode film-forming additives to the electrolyte of sodium-ion batteries, a stable cathode interface film is formed, which solves the problem of poor cycle performance of sodium-ion batteries at high temperatures, achieves high capacity retention and low volume growth rate at high temperatures, and improves the high-temperature stability and safety of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- FARASIS TECH (GANZHOU) CO LTD
- Filing Date
- 2023-12-29
- Publication Date
- 2026-07-31
AI Technical Summary
Sodium-ion batteries exhibit poor cycle performance at high temperatures, low capacity retention, gas generation, and high volume growth rate at high temperatures. Existing technologies such as controlling electrolyte volume, using high-salt-concentration electrolytes, or negative electrode film-forming additives have limited effectiveness and suffer from problems such as high cost and poor wettability.
Additive A, containing tetra(4-ethynylbenzene)methane, is used to form a dense interfacial film on the positive electrode surface. Combined with conventional negative electrode film-forming additive B, a stable interfacial film is formed, which inhibits the dissolution of organic components at high temperatures, reduces side reactions, and improves the stability of the electrode/electrolyte interface.
It significantly improves the capacity retention and reduces the volume growth rate of sodium-ion batteries at high temperatures, reduces gas production, enhances the high-temperature cycling and storage performance of the batteries, and improves the stability and safety of the batteries.
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Figure CN117913362B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium-ion battery technology, specifically to a high-temperature sodium-ion battery electrolyte and a sodium-ion battery. Background Technology
[0002] Compared to lithium resources, sodium resources are abundant, with an abundance of 2.64% in the Earth's crust, 440 times that of lithium resources. Furthermore, sodium is widely distributed, easy to refine, and inexpensive for large-scale commercial use. This gives sodium-ion batteries a significant advantage in raw material costs compared to lithium-ion batteries. The working principle of sodium-ion batteries is similar to that of lithium-ion batteries. In addition to cost advantages, sodium-ion batteries offer the following advantages: 1) Energy density superior to lead-acid batteries and comparable to lithium iron phosphate batteries; 2) Excellent low-temperature performance, suitable for use in cold regions; 3) Superior safety performance compared to ternary lithium batteries and lithium iron phosphate batteries; 4) Environmentally friendly, aligning with sustainable development strategies.
[0003] However, sodium-ion batteries also suffer from poor cycle performance, gas expansion during high-temperature storage, and low initial efficiency, which limits their widespread application. Research shows that the solubility of the solid electrolyte interface film in sodium-ion batteries is higher than that in lithium-ion batteries. At high temperatures, the organic components in the solid electrolyte interface film dissolve, resulting in a porous structure. The electrolyte continues to decompose, metal ions dissolve, and the solid electrolyte interface film continues to decompose and regenerate, triggering a series of side reactions that continuously consume the limited sodium resources within the sodium-ion battery, leading to increased internal resistance and capacity loss.
[0004] To address the high-temperature problem in batteries, the following solutions are generally adopted: 1) Controlling the electrolyte volume: Excessive electrolyte volume can exacerbate SEI film dissolution. During cycling, changes in electrode material volume can damage the SEI film, further increasing electrolyte consumption; 2) Using high-salt-concentration electrolytes: The SEI film formed in high-salt-concentration electrolytes has lower solubility; 3) Using high-temperature additives: Currently used additives are mainly targeted at the negative electrode. At high temperatures, the electrolyte decomposes on the negative electrode surface to form a thick SEI film. Using high-temperature additives can form a stable SEI composition, reducing the continuous dissolution of the SEI at high temperatures. However, the above-mentioned technical means to solve the high-temperature problem all have certain shortcomings. For example, reducing the electrolyte volume can lead to poor electrode wetting and high impedance; high-salt-concentration electrolytes are expensive and have high viscosity and poor wettability; simply using negative electrode film-forming additives has limited improvement on the high-temperature performance of the battery.
[0005] Patent CN115986207A uses a triazine compound containing acetylene silicon groups as an additive, which can form a film on the positive and negative electrode surfaces, effectively improving the high-voltage performance of sodium-ion batteries and significantly improving their capacity during high-temperature cycling and storage. However, it produces a large amount of gas at high temperatures, which will significantly degrade the battery's later cycle and storage stability and lifespan. Patent CN103545551B uses a phenylacetylene derivative as an additive, which can improve the gas production during room-temperature cycling of lithium titanate batteries. However, the hydroxyl, amino, and ether groups contained in its structure will significantly degrade the battery's high-temperature performance (hydroxyl groups easily react with LiPF6 to generate harmful HF, affecting the battery's storage stability; hydrogen on the amino group is not very stable and is easily consumed during storage or cycling, thus losing capacity; ether groups have poor oxidation resistance and are very easy to decompose at the positive electrode, affecting the battery's cycle stability).
[0006] Therefore, it is particularly important to provide a sodium-ion battery electrolyte that can form a dense and stable positive electrode interface film on the positive electrode surface, reduce the dissolution of organic components in the interface film at high temperatures, improve the high-temperature performance of the battery, and reduce gas production. Summary of the Invention
[0007] To address the shortcomings of the prior art, one objective of this invention is to provide a high-temperature sodium-ion battery electrolyte that can form a stable interface film on the positive electrode surface, reduce the dissolution of organic components in the interface film at high temperatures, improve the stability of the electrode-electrolyte interface, and enable sodium-ion batteries using this electrolyte to maintain a high capacity retention rate and a low volume growth rate under high-temperature cycling; thus solving the problems of poor high-temperature cycling performance, low capacity retention rate, and gas generation at high temperatures in sodium-ion batteries.
[0008] The above-mentioned objective of this invention is achieved through the following technical solution:
[0009] A high-temperature sodium-ion battery electrolyte comprises a non-aqueous organic solvent, a sodium salt, and additive A, wherein additive A is a compound having the following structural formula:
[0010]
[0011] In the electrolyte of this invention, during charge and discharge, the four terminal alkyne groups of additive A can form active centers. Additive A also possesses a highly symmetrical and stable structure, and does not contain hydroxyl, amino, or ether groups, which negatively impact battery performance. This makes the resulting interfacial film more stable and reduces side reactions. Consequently, the electrolyte of this invention polymerizes on the positive electrode surface to form a dense and robust CEI film. This interfacial film exhibits good thermal stability and excellent stability even at high temperatures. It can inhibit oxidation reactions of the electrolyte on the positive electrode surface, suppress the dissolution of transition metal ions in the positive electrode material, thereby inhibiting their catalytic decomposition of the electrolyte. It also inhibits battery capacity loss caused by transition metal ion deposition on the negative electrode, reduces polarization side reactions during battery charge and discharge, and improves the stability of the electrode / electrolyte interface. This allows sodium-ion batteries using the electrolyte of this invention to maintain high capacity retention and low volume growth rate under high-temperature cycling and storage conditions.
[0012] Preferably, the amount of additive A is 0.1% to 10% of the total mass of the sodium-ion battery electrolyte. More preferably, the amount of additive A is 0.1% to 5.0% of the total mass of the sodium-ion battery electrolyte. Even more preferably, the amount of additive A is 0.1% to 2% of the total mass of the sodium-ion battery electrolyte.
[0013] Preferably, the electrolyte further includes film-forming additive B, which includes at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), propylene sulfate (PCS), 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), methyl methylene disulfonate (MMDS), vinyl sulfite (ES), vinyl ethylene carbonate (VEC), and vinyl ethylene sulfite (VES).
[0014] Conventional negative electrode film-forming additive B can form an SEI film on the negative electrode surface. It works synergistically with additive A to effectively suppress the occurrence of side reactions and gas production during high-temperature storage of sodium-ion batteries, thereby improving the high-temperature performance of sodium-ion batteries. This allows sodium-ion batteries using the electrolyte of this invention to maintain a high capacity retention rate and a low volume growth rate under high-temperature cycling.
[0015] Preferably, the amount of film-forming additive B is 0.1% to 2.0% of the total mass of the sodium-ion battery electrolyte.
[0016] Preferably, the non-aqueous organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl acetate, and methyl acetate.
[0017] Preferably, the sodium salt comprises at least one of sodium hexafluorophosphate, sodium dioxalate borate, sodium perchlorate, sodium difluorooxalate borate, sodium difluorophosphate, and sodium difluorosulfonamide.
[0018] Preferably, the amount of the non-aqueous organic solvent used is 75% to 90% of the total mass of the sodium-ion battery electrolyte.
[0019] Preferably, the sodium salt comprises at least two of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium difluorophosphate, and sodium difluorosulfonamide.
[0020] Another object of the present invention is to provide a sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, and the sodium-ion battery electrolyte. Attached Figure Description
[0021] Figure 1 The graph shows the capacity retention of sodium-ion batteries in Example 2 and Comparative Example 1 under 60°C cycling.
[0022] Figure 2 The graph shows the growth rate of internal resistance of sodium-ion batteries in Example 2 and Comparative Example 1 under cycling at 60°C. Detailed Implementation
[0023] The applicant will now provide a detailed description of the method of the present invention in conjunction with specific embodiments, with the aim of enabling those skilled in the art to clearly understand the present invention.
[0024] The high-temperature sodium-ion battery electrolyte of the present invention comprises a non-aqueous organic solvent, a sodium salt, and additive A, wherein additive A is a compound having the following structural formula:
[0025]
[0026] The amount of non-aqueous organic solvent used can be 75% to 90% of the total mass of the sodium-ion battery electrolyte, for example, 76.5%, 81.5%, 82.5%, 84.5%, 86.2%, 86.6%, 89.2%, etc.; the amount of sodium salt used can be 6% to 15% of the total mass of the sodium-ion battery electrolyte, for example, 6%, 8%, 11%, 13%, 15%, etc. The electrolyte can have good performance within this range of the amount of non-aqueous organic solvent and sodium salt. For ease of comparison, the amount of sodium salt used in the following specific embodiments is uniformly selected as 12% of the total mass of the sodium-ion battery electrolyte.
[0027] As an optional implementation, the non-aqueous organic solvent may be selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl acetate, and methyl acetate.
[0028] As an optional implementation, the sodium salt may be selected from at least one of sodium hexafluorophosphate, sodium dioxalate borate, sodium perchlorate, sodium difluorooxalate borate, sodium difluorophosphate, and sodium difluorosulfonamide.
[0029] As an optional implementation, film-forming additive B includes at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), propylene sulfate (PCS), 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), methyl disulfonate (MMDS), vinyl sulfite (ES), vinyl ethylene carbonate (VEC), and vinyl ethylene sulfite (VES); the amount of film-forming additive B can be 0.1% to 2% of the total mass of the sodium-ion battery electrolyte.
[0030] The following embodiments are merely illustrative examples of specific implementations of the present invention. The described embodiments are only a part of the embodiments of the present invention, but the following embodiments should not be construed in any way as limiting the scope of protection claimed in the claims of the present invention.
[0031] The preparation method of the high-temperature sodium-ion battery electrolyte of the present invention is as follows:
[0032] In a helium-filled glove box, the solvents are first mixed evenly in proportion to obtain a mixed non-aqueous organic solvent. Then, sodium salt is added to the mixed non-aqueous organic solvent. After the sodium salt is completely dissolved, tetra(4-ethynylbenzene)methane and conventional negative electrode film-forming additive B are added. After stirring evenly, a high-temperature sodium-ion battery electrolyte is obtained.
[0033] The types and contents of additives and sodium salts, solvent ratios, etc. used in the various embodiments and comparative examples of this invention are shown in Table 1. The amount of each additive added is a mass percentage calculated based on the total mass of the electrolyte.
[0034] Table 1
[0035]
[0036] Note: "-" indicates that the substance is not added.
[0037] Preparation of sodium batteries:
[0038] Take Na[Ni 0.33 Fe 0.33 Cu 0.33 O2 layered oxide is used as the positive electrode material. It is dissolved in N-methylpyrrolidone solvent with conductive agent SP and binder PVDF at a mass ratio of 92:4:4. After thorough stirring and mixing, the solid content is controlled at 68% to prepare the positive electrode slurry. The positive electrode slurry is coated on aluminum foil positive electrode current collector, and then rolled, dried and stamped to obtain the positive electrode sheet.
[0039] Hard carbon was used as the negative electrode material. It was dissolved in deionized water solvent with conductive agent SP, binder styrene-butadiene rubber SBR1346 and thickener sodium carboxymethyl cellulose in a mass ratio of 94:3:2:1. After thorough stirring and mixing, the solid content was controlled at 50% to prepare the negative electrode slurry. The negative electrode slurry was coated on aluminum foil negative electrode current collector, and then rolled, dried and stamped to obtain the negative electrode sheet.
[0040] A diaphragm is made by coating a ceramic layer onto a polyethylene (PE) base film.
[0041] The above-mentioned positive electrode, negative electrode, and separator were used to form a battery cell, which was then dried in an oven at 80-85°C for 48 hours and then transferred to a glove box for later use. The sodium-ion battery electrolytes prepared in Examples 1-6 and the comparative examples were injected into the dried battery cells, and the cells were sequentially packaged, activated, formed, aged, repackaged, and tested for capacity to obtain sodium-ion batteries.
[0042] Sodium-ion battery performance test 1
[0043] After obtaining the sodium-ion battery, the sodium-ion batteries prepared in the examples and comparative examples were subjected to 1.5V~3.9V, 1C / 1C cycle charge-discharge tests respectively. The test steps are shown in Table 2, and the test results of capacity retention rate and internal resistance growth rate are shown in Table 3.
[0044] Table 2. Cyclic Test Steps
[0045] 1 Let it sit for 4 hours 2 1C rate constant current discharge to 1.5V 3 Let it sit for 30 minutes 4 1C rate constant current constant voltage charging to 3.9V, cut-off current 0.05C rate current. 5 Let it sit for 30 minutes 6 1C rate constant current discharge to 1.5V 7 Let it sit for 30 minutes 8 Loop: Starting step: 4, Number of loops: 800
[0046] Table 3. Capacity retention and internal resistance growth rate after 400 cycles.
[0047]
[0048]
[0049] Note: The data in the table is the average of two sodium-ion battery data.
[0050] As shown in Table 3, compared with Comparative Example 1, the addition of tetra(4-ethynylbenzene)methane to the electrolyte in this invention can effectively improve the capacity retention rate of sodium-ion batteries at high temperatures, reduce the rate of increase in internal resistance, and enhance the high-temperature cycle performance of sodium-ion batteries. The high-temperature cycle performance of the sodium-ion battery is optimal when the amount of tetra(4-ethynylbenzene)methane added is 0.5% of the total mass of the electrolyte. Compared with Example 3, Comparative Example 6 only used NaPF6 as the sodium salt, while the addition of both NaPF6 and NaFSi as semi-main salts significantly improved the high-temperature cycle performance. NaFSi has high thermal stability and can maintain the stability and safety of the battery under high-temperature conditions. Adding other high-temperature sodium salts to the traditional sodium salt NaPF6 can significantly improve the high-temperature performance of the battery. Compared to Example 2, Comparative Example 4 replaced tetra(4-ethynylbenzene)methane with 3-difluoromethoxyphenylacetylene. The capacity retention rate of the sodium-ion battery at high temperature was significantly reduced, and the internal resistance growth rate was significantly increased. This is mainly because the structural stability of 3-difluoromethoxyphenylacetylene is reduced compared to tetra(4-ethynylbenzene)methane, and the CEI film formed by the electrolyte is not dense enough, which in turn reduces the stability of the interface film and significantly reduces the high-temperature cycling performance of the sodium-ion battery.
[0051] Sodium-ion battery performance test 2
[0052] After collecting the data from sodium-ion battery test 1, the sodium-ion batteries prepared in the examples and comparative examples were subjected to a 3.9V full-charge 85℃ storage test. The test steps are shown in Table 4, and the test results are shown in Table 5.
[0053] Table 4 Storage Test Steps
[0054]
[0055]
[0056] Table 5 High-Temperature Storage Performance of Sodium-Ion Batteries
[0057]
[0058] Note: The data in the table is the average of two sodium-ion battery data.
[0059] As can be seen from the test results in Table 5, compared with Comparative Example 1, the addition of tetra(4-ethynylbenzene)methane to the electrolyte can effectively improve the capacity recovery rate, reduce the DC internal resistance growth rate, reduce the volume growth rate, and enhance the high-temperature storage performance of sodium-ion batteries. This is because the interfacial film formed by the electrolyte of this invention on the positive electrode surface is more stable, which can effectively suppress the occurrence of side reactions in sodium-ion batteries at high temperatures and reduce gas production. Compared with Example 3, the sodium salt in Comparative Example 6 is only NaPF6, while the high-temperature storage performance is significantly improved by adding both NaPF6 and NaFSi as semi-main salts. Compared to Example 2, Comparative Example 4 replaced tetra(4-ethynylbenzene)methane with 3-difluoromethoxyphenylacetylene, and Comparative Example 5 replaced tetra(4-ethynylbenzene)methane with 2,4,6-tris((trimethylsilyl)ethynyl)-1,3,5-triazine. Both of these changes resulted in a significant decrease in the capacity recovery rate of the sodium-ion battery and a significant increase in the internal resistance growth rate and volume growth rate. This may be because, compared to tetra(4-ethynylbenzene)methane, the positive electrode CEI film formed by 3-difluoromethoxyphenylacetylene and 2,4,6-tris((trimethylsilyl)ethynyl)-1,3,5-triazine has lower stability, triggers more side reactions, and produces more gas.
[0060] Sodium-ion battery performance test 3
[0061] The sodium-ion battery, after completing sodium-ion battery test 1 and sodium-ion battery test 2, was disassembled. The negative electrode was removed, cleaned with DMC, and dried. Then, a 10cm sample was taken. 2 The negative electrode sheet, which was cleaned by DMC, was acid-washed with 1 mL of 3M nitric acid solution to dissolve the transition metal deposited on the negative electrode into transition metal ions. The concentration of transition metal ions was measured by an inductively coupled plasma (ICP) instrument. The test results are shown in Table 6.
[0062] Table 6. Transition metal ion content of sodium-ion battery negative electrode after acid washing.
[0063]
[0064] Note: The data in the table is the average of two sodium-ion battery data.
[0065] The test results in Table 6 show that, compared to Comparative Example 1, Examples 1-6 all effectively reduced the content of transition metal ions dissolved from the negative electrode. This indicates that tetra(4-ethynylbenzene)methane has a significant inhibitory effect on the dissolution of transition metal ions. Furthermore, compared to Example 2, Comparative Example 4 replaced tetra(4-ethynylbenzene)methane with 3-difluoromethoxyphenylacetylene, and Comparative Example 5 replaced tetra(4-ethynylbenzene)methane with 2,4,6-tris((trimethylsilyl)ethynyl)-1,3,5-triazine. However, the content of transition metal ions at the negative electrode increased significantly. This may be because, compared to tetra(4-ethynylbenzene)methane, the positive electrode CEI film formed by 3-difluoromethoxyphenylacetylene and 2,4,6-tris((trimethylsilyl)ethynyl)-1,3,5-triazine has lower stability and a weaker ability to inhibit the dissolution of transition metal ions.
[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A high-temperature sodium-ion battery electrolyte, characterized in that, This is a non-aqueous electrolyte used to improve the high-temperature performance of sodium-ion batteries. The electrolyte includes a non-aqueous organic solvent, a sodium salt, and additive A. Additive A is a compound having the following structural formula: 。 2.The high-temperature sodium-ion battery electrolyte of claim 1, characterized in that, The amount of additive A is 0.1% to 10% of the total mass of the sodium-ion battery electrolyte. 3.The high-temperature sodium-ion battery electrolyte according to claim 2, characterized in that, The amount of additive A is 0.1% to 5.0% of the total mass of the sodium-ion battery electrolyte. 4.The high-temperature sodium-ion battery electrolyte according to claim 3, characterized in that, The amount of additive A is 0.1% to 2% of the total mass of the sodium-ion battery electrolyte. 5.The high-temperature sodium-ion battery electrolyte of claim 1, wherein, The electrolyte further includes film-forming additive B, which includes at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl sulfate (DTD), propylene sulfate (PCS), 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PST), methyl methanedisulfonate (MMDS), vinyl sulfite (ES), vinyl ethylene carbonate (VEC), and vinyl ethylene sulfite (VES). 6.The high-temperature sodium-ion battery electrolyte according to claim 5, characterized in that, The amount of film-forming additive B is 0.1% to 2.0% of the total mass of the sodium-ion battery electrolyte. 7.The high-temperature sodium-ion battery electrolyte of claim 1, wherein, The non-aqueous organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl acetate, and methyl acetate. 8.The high-temperature sodium-ion battery electrolyte of claim 1, characterized in that, The sodium salt includes at least one of sodium hexafluorophosphate, sodium dioxalate borate, sodium perchlorate, sodium difluorooxalate borate, sodium difluorophosphate, and sodium difluorosulfonamide. 9.The high-temperature sodium-ion battery electrolyte of claim 1, wherein, The amount of the non-aqueous organic solvent used is 75% to 90% of the total mass of the sodium-ion battery electrolyte. 10.The high-temperature sodium-ion battery electrolyte of claim 1, characterized in that, The sodium salt includes at least two of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium difluorophosphate, and sodium difluorosulfonamide.
11. A sodium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and the sodium-ion battery electrolyte as described in any one of claims 1 to 10.