Sodium-ion battery electrolyte and sodium-ion battery
By adding sodium salts and film-forming additives to the electrolyte of sodium-ion batteries, a dense SEI film is formed, which solves the problem of insufficient cycle performance and electrochemical performance of sodium-ion batteries, and achieves high-efficiency cycle and improved electrochemical performance of the batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG HAISIDA NAXING TECHNOLOGY CO LTD
- Filing Date
- 2024-10-31
- Publication Date
- 2026-05-08
AI Technical Summary
Existing sodium-ion batteries have poor cycle performance and electrochemical performance, especially the SEI film is prone to rupture under high temperature conditions, which leads to a decline in battery performance.
Adding functional additives, including sodium salts and film-forming additives such as acid anhydrides and cyclic carbonates, to the electrolyte forms a dense SEI film, improving the battery's cycle performance and electrochemical performance.
The prepared sodium-ion battery exhibits excellent cycle performance and electrochemical performance, with significantly improved initial coulombic efficiency and long-term capacity retention.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium-ion batteries, and more specifically to a sodium-ion battery electrolyte and a sodium-ion battery. Background Technology
[0002] Sodium-ion battery electrolytes are a crucial component of sodium-ion batteries. Optimizing the composition and structure of the electrolyte, exploring novel solvents and additives, and improving the compatibility between the electrolyte and electrode materials can enhance the battery's electrochemical performance and safety. High-concentration electrolytes possess a wider operating voltage range, a broader liquid temperature window, and lower flammability. They can form a uniform and protective SEI film while suppressing sodium dendrite growth. These properties provide the foundation for developing high-performance batteries. Advances in sodium-ion battery electrolyte research will provide significant support for their commercial application.
[0003] The properties of the SEI film in sodium-ion batteries, including its morphology, composition, and conductivity, significantly impact the electrochemical performance and safety of the system. Specifically, during charging, sodium ions are extracted from the positive electrode material and embedded into the carbon negative electrode via the electrolyte. The SEI film formed during the initial charging process prevents further decomposition of the electrolyte on the carbon negative electrode surface, acting as a sodium ion conductor and allowing only sodium ions to pass through. However, during subsequent charge-discharge cycles, electrode changes can cause the SEI film to rupture. This can lead to the negative electrode being re-exposed to the electrolyte and continuously reacting with it, consuming electrolyte and generating gas. This increases the internal pressure of the sodium-ion battery, reducing its cycle life. Especially when the battery is stored or used under high-temperature conditions, electrode volume changes are more pronounced, making the SEI film more prone to rupture and resulting in a more significant decline in the electrochemical performance of the sodium-ion battery under high-temperature conditions.
[0004] Currently, existing sodium-ion battery technologies often improve cycle performance and electrochemical performance by adding certain film-forming agents to the electrolyte, but this still cannot meet market demands. Summary of the Invention
[0005] The purpose of this invention is to overcome the problem of poor cycle performance and electrochemical performance of sodium-ion batteries in the prior art, and to provide a sodium-ion battery electrolyte and a sodium-ion battery that have excellent cycle performance and electrochemical performance.
[0006] To achieve the above objectives, the present invention provides a sodium-ion battery electrolyte containing functional additives and optionally a solvent; the functional additives include sodium salts and film-forming additives; the film-forming additives include anhydride compounds and cyclic carbonates represented by formula (1); the anhydride compounds are selected from at least one of diethanol anhydride, succinic anhydride, and maleic anhydride; and the mass ratio of the anhydride compounds to the cyclic carbonates is 1:1-5.
[0007] Equation (1):
[0008] In formula (1), R1 and R2 are each independently selected from H and C1-C6 alkyl groups.
[0009] A second aspect of the present invention provides a sodium-ion battery, wherein the electrolyte in the sodium-ion battery is the sodium-ion battery electrolyte described in the first aspect of the present invention.
[0010] By adopting the above technical solution, a dense SEI film can be formed through the synergistic effect of sodium salt and film-forming additive in the functional additive, thereby enabling the prepared sodium-ion battery to have both excellent cycle performance and electrochemical performance. Detailed Implementation
[0011] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0012] In this invention, C1-C6 alkyl refers to straight-chain or branched alkyl groups having 1-6 carbon atoms, including but not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, n-hexyl, and isohexyl.
[0013] The present invention provides a sodium-ion battery electrolyte containing functional additives and optionally a solvent; the functional additives include sodium salts and film-forming additives; the film-forming additives include anhydride compounds and cyclic carbonates of formula (1); the anhydride compounds are selected from at least one of diethanol anhydride, succinic anhydride and maleic anhydride; and the mass ratio of the anhydride compounds to the cyclic carbonates is 1:1-5.
[0014] Equation (1):
[0015] In formula (1), R1 and R2 are each independently selected from H and C1-C6 alkyl groups.
[0016] In this invention, by adding the functional additive to the battery electrolyte, the sodium salt and the film-forming additive have an excellent synergistic effect, which can form a dense SEI film, and further enable the prepared sodium-ion battery to have both excellent cycle performance and electrochemical performance.
[0017] In this invention, in order to improve the synergistic effect between cyclic carbonates and acid anhydride compounds in the film-forming additive, preferably, the mass ratio of the acid anhydride compounds to the cyclic carbonates is 1:2-3, for example, it can be any value within the range of 1:2, 1:3, etc.
[0018] In this invention, in order to improve the synergistic effect of sodium salt and film-forming additive in the functional additive, preferably, in formula (1), R1 and R2 are each independently selected from H and C1-C4 alkyl groups.
[0019] Preferably, R1 and R2 are each independently selected from H, methyl, ethyl, n-propyl, isopropyl, and n-butyl.
[0020] In this invention, in order to further improve the synergistic effect of the functional additives and make the prepared sodium-ion battery have excellent cycle performance and electrochemical performance, preferably, the cyclic carbonate shown in formula (1) is selected from at least one of the following compounds;
[0021] Compound (1): In formula (1), R1 is H and R2 is H;
[0022] Compound (2): In formula (1), R1 is H and R2 is methyl;
[0023] Compound (3): In formula (1), R1 is H and R2 is ethyl;
[0024] Compound (4): In formula (1), R1 is H and R2 is n-propyl.
[0025] In this invention, to improve the density of the SEI film and prepare a sodium-ion battery with good cycle performance and electrochemical performance, preferably, the content of the film-forming additive is 1-15 wt%, preferably 5-10 wt%, based on the total mass of the functional additives. For example, the content of the film-forming additive can be any value within the range of 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 15 wt%, etc.
[0026] In this invention, in order to prepare a sodium-ion battery with good cycle performance and electrochemical performance, preferably, the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium perchlorate and sodium tetrafluoroborate.
[0027] According to a preferred embodiment, the sodium salt content of the sodium salt is 85-99 wt%, preferably 90-95 wt%, based on the total mass of the functional additive.
[0028] According to another preferred embodiment, the sodium-ion battery electrolyte further contains a non-aqueous organic solvent as the solvent, and the content of the non-aqueous organic solvent is 60-90 wt% based on the total mass of the sodium-ion battery electrolyte, and the content of the functional additive is 10-40 wt%.
[0029] In this invention, to improve the solubility of the functional additive, preferably, the non-aqueous organic solvent is selected from one or more of methyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. More preferably, the non-aqueous organic solvent is selected from propylene carbonate and / or methyl ethyl carbonate, particularly propylene carbonate and methyl ethyl carbonate in a volume ratio of 1:1-3, for example, the volume ratio of propylene carbonate and methyl ethyl carbonate can be 1:1, 1:1.5, or 1:2.
[0030] A second aspect of the present invention provides a sodium-ion battery, wherein the electrolyte in the sodium-ion battery is the sodium-ion battery electrolyte described in the first aspect of the present invention.
[0031] According to the present invention, there are no particular limitations on the positive electrode, negative electrode and separator of the battery. Various types of positive electrodes, negative electrodes and separators used in the field of sodium-ion battery manufacturing can be used, as long as the electrolyte used in the battery is the sodium-ion battery electrolyte described in the present invention.
[0032] In this invention, the preparation method of the positive electrode can employ various methods commonly used in the art. For example, it may include mixing the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder with a solvent, coating and / or filling them onto the positive electrode current collector, drying, and rolling or not rolling to obtain the positive electrode.
[0033] According to the present invention, the positive electrode active material can be Na. x CoO2, Na x MnO2 and Na x At least one of FeO2, wherein 0 ≤ x ≤ 1. Preferably, the content of positive electrode active material in the positive electrode material layer of the battery is 92-98 wt%.
[0034] According to the present invention, preferably, the positive electrode binder can be selected from at least one of SBR (styrene-butadiene rubber), PAA (polyacrylic acid), and PVDF (polyvinylidene fluoride). Preferably, based on the positive electrode active material, the amount of the positive electrode binder can be 2.5-5 wt%. The positive electrode conductive agent can be at least one of CNT (carbon nanotubes) and conductive carbon black. Preferably, based on the positive electrode active material, the amount of the positive electrode conductive agent can be 0.6-1.2 wt%.
[0035] In this invention, the negative electrode can be prepared by various methods commonly used in the art. For example, it may include mixing negative electrode active material, negative electrode binder and negative electrode solvent, coating and / or filling it on the negative electrode current collector, forming a negative electrode material layer on the surface of the negative electrode current collector, drying, and calendering or not calendering to obtain the negative electrode.
[0036] According to the present invention, the negative electrode active material can be at least one of hard carbon, graphite and soft carbon. Preferably, the content of the negative electrode active material in the negative electrode material layer of the battery is 92-97 wt%.
[0037] According to the present invention, preferably, the negative electrode adhesive can be selected from at least one of SBR (styrene-butadiene rubber), PAA (polyacrylic acid), and CMC (sodium carboxymethyl cellulose). Preferably, based on the negative electrode active material, the amount of the negative electrode adhesive can be 4-10 wt%. The negative electrode conductive agent can be at least one of CNT and conductive carbon black. Preferably, based on the negative electrode active material, the amount of the negative electrode conductive agent can be 0.6-1.2 wt%.
[0038] In this invention, the current collectors in the positive and negative electrodes are commonly used current collectors in the art, such as aluminum foil and carbon-coated foil.
[0039] According to the present invention, the separator is disposed between the positive electrode and the negative electrode and has electrical insulation properties and liquid retention properties. The separator can be at least one selected from various separators used in sodium-ion batteries, such as PP, PE and ceramic separators.
[0040] In this invention, the battery is prepared by a conventional method in the art. Generally, the positive and negative electrodes are separated by a separator layer to form an electrode assembly. The resulting electrode assembly and non-aqueous electrolyte are then sealed in a battery case to obtain the battery provided by this invention.
[0041] The sodium-ion battery prepared using the electrolyte composition and electrolyte described in this invention exhibits excellent cycle performance and electrochemical performance. In some preferred embodiments, the initial coulombic efficiency and capacity retention after 300, 600, and 900 cycles of the prepared sodium-ion battery are all not less than 90%.
[0042] The present invention will be described in detail below through examples. In the following examples, vinylene carbonate was purchased from Aladdin Company, grade 872-36-6; diethanolamine was purchased from Aladdin Company, grade 4480-83-5; succinic anhydride was purchased from Aladdin Company, grade 108-30-5; and fluorovinylene carbonate was purchased from Aladdin Company, grade 14435-02-8.
[0043] Example 1
[0044] Electrolyte IA1 was prepared by adding 100.77 g of sodium hexafluorophosphate and 6.6 g of film-forming additive (including 4.4 g of vinylene carbonate and 2.2 g of diethanol anhydride) to 200 ml of a propylene carbonate and methyl ethyl carbonate solution with a volume ratio of 1:1.
[0045] Example 2
[0046] Electrolyte IA2 was prepared by adding 110g of sodium hexafluorophosphate and 12.5g of film-forming additive (including 3.5g of vinylene carbonate and 8g of diethanol anhydride) to 180ml of a propylene carbonate and methyl ethyl carbonate solution with a volume ratio of 1:1.5 at room temperature.
[0047] Example 3
[0048] Electrolyte IA3 was prepared by a method similar to that in Example 1, except that succinic anhydride was replaced with diethanolic anhydride in the same weight proportions.
[0049] Example 4
[0050] Electrolyte IA4 was prepared by a method similar to that in Example 1, except that sodium tetrafluoroborate was used instead of sodium hexafluorophosphate in the same weight proportions.
[0051] Example 5
[0052] Electrolyte IB5 was prepared by following a similar method to Example 1, except that 6.6 g of film-forming additives (including 4.95 g of vinylene carbonate and 1.65 g of diethanol anhydride) were added.
[0053] Example 6
[0054] Electrolyte IB6 was prepared by a method similar to that in Example 1, except that 6.6 g of film-forming additives (including 5.28 g of vinylene carbonate and 1.32 g of diethanol anhydride) were added.
[0055] Comparative Example 1
[0056] Electrolyte IB1 was prepared using a method similar to that in Example 1, except that diethanol anhydride was not added.
[0057] Comparative Example 2
[0058] Electrolyte IB2 was prepared using a method similar to that in Example 1, except that vinylene carbonate was not added.
[0059] Comparative Example 3
[0060] Electrolyte IB3 was prepared using a method similar to that in Example 1, except that an equal part by weight of fluoroethylene carbonate was used instead of ethylene carbonate.
[0061] Comparative Example 4
[0062] Electrolyte IB4 was prepared by following a similar method to Example 1, except that 10.5g of film-forming additive (including 10g of vinylene carbonate and 1.5g of diethanol anhydride) was added.
[0063] Test Example 1
[0064] Using NaMnO2 as the positive electrode material, hard carbon as the negative electrode, and PP as the separator, sodium-ion batteries S1-S6 and DS1-DS4 were prepared by slurry preparation, coating, winding, baking at 95℃ for 48h, and then injected into sodium-ion electrolytes IA1-IA6 and IB1-IB4 respectively. Cyclic tests were then performed on them, and the test results are shown in Table 1.
[0065] The positive electrode consists of: 95 wt% NaMnO2 positive electrode material; 4 wt% PVDF positive electrode binder; and 1 wt% conductive carbon black positive electrode conductive agent. The negative electrode consists of: 94.5 wt% hard carbon; 4.4 wt% SBR negative electrode binder; and 1.1 wt% conductive carbon black negative electrode conductive agent.
[0066] The testing method is as follows:
[0067] 1. Initial Coulombic Charge Efficiency: The battery is charged at a constant current of 0.2C to 3.95V, and then switched to constant voltage charging at 3.95V until the charging current is less than or equal to 0.05C, and then left to rest for 2 minutes; the battery is discharged at a constant current of 0.2C to 1.8V, left to rest for 2 minutes, and the charge and discharge capacity is recorded.
[0068] 2. Cyclic performance:
[0069] (1) The battery was discharged to 1.8V at a constant current of 0.5C at room temperature and left to stand for 30 minutes;
[0070] (2) Place the battery in an environment of 25℃±2℃ for 4 hours;
[0071] (3) Charge the battery at a constant current of 0.5C to 3.95V, and then switch to constant voltage charging at 3.95V until the charging current is less than or equal to 0.05C, and let it rest for 30 minutes.
[0072] (4) Discharge the battery at a constant current of 0.5C to 1.8V and let it rest for 30 minutes;
[0073] (5) Repeat steps 3-4 until the number of charge-discharge cycles is ≥900. Record the capacity retention rate after 300, 600 and 900 cycles respectively.
[0074] Table 1
[0075] Test Example Battery No. Initial coulombic efficiency / % 300 cycle capacity retention 600 cycle capacity retention 900 cycle capacity retention S1 91.04％ 94.12％ 92.53％ 91.13％ S2 91.08％ 94.26％ 92.49％ 91.91％ S3 90.94％ 92.94％ 91.82％ 90.71％ S4 90.52％ 92.31％ 91.91％ 90.81％ S5 84.78％ 87.89％ 85.86％ 84.01％ S6 84.41％ 87.86％ 85.48％ 84.72％ DS1 70.31％ 73.61％ 72.07％ 70.66％ DS2 71.42％ 74.53％ 72.54％ 71.73％ DS3 75.61％ 78.32％ 76.54％ 73.96％ DS4 75.34％ 79.69％ 76.80％ 72.68％
[0076] As can be seen from the results in Table 1, compared with Comparative Examples 1-4, the sodium-ion batteries prepared using Examples 1-6 of the present invention have significantly better initial coulombic charging efficiency and long-cycle performance. In particular, the initial coulombic efficiency and capacity retention rates after 300, 600, and 900 cycles of the sodium-ion batteries prepared in Examples 1-4 are all higher than 90%.
[0077] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A sodium-ion battery electrolyte, characterized in that, The electrolyte contains functional additives and optionally also contains solvents; the functional additives include sodium salts and film-forming additives; the film-forming additives include acid anhydride compounds and cyclic carbonates represented by formula (1); the acid anhydride compounds are selected from at least one of diethanol anhydride, succinic anhydride and maleic anhydride; and the mass ratio of the acid anhydride compounds to the cyclic carbonates is 1:1-5; Equation (1): In formula (1), R1 and R2 are each independently selected from H and C1-C6 alkyl groups.
2. The sodium-ion battery electrolyte according to claim 1, wherein, The mass ratio of the acid anhydride compound to the cyclic carbonate is 1:2-3.
3. The sodium-ion battery electrolyte according to claim 1 or 2, wherein, In formula (1), R1 and R2 are each independently selected from H and C1-C4 alkyl groups; Preferably, R1 and R2 are each independently selected from H, methyl, ethyl, n-propyl, isopropyl, and n-butyl.
4. The sodium-ion battery electrolyte according to any one of claims 1-3, wherein, The cyclic carbonates represented by formula (1) are selected from at least one of the following compounds; Compound (1): In formula (1), R1 is H and R2 is H; Compound (2): In formula (1), R1 is H and R2 is methyl; Compound (3): In formula (1), R1 is H and R2 is ethyl; Compound (4): In formula (1), R1 is H and R2 is n-propyl.
5. The sodium-ion battery electrolyte according to any one of claims 1-4, wherein, Based on the total mass of the functional additives, the content of the film-forming additives is 1-15 wt%, preferably 5-10 wt%.
6. The sodium-ion battery electrolyte according to any one of claims 1-5, wherein, The sodium salt is selected from one or more of sodium hexafluorophosphate, sodium perchlorate, and sodium tetrafluoroborate.
7. The sodium-ion battery electrolyte according to claim 6, wherein, Based on the total mass of the functional additives, the sodium salt content is 85-99 wt%, preferably 90-95 wt%.
8. The sodium-ion battery electrolyte according to any one of claims 1-7, wherein, The sodium-ion battery electrolyte also contains a non-aqueous organic solvent as the solvent. Based on the total mass of the sodium-ion battery electrolyte, the content of the non-aqueous organic solvent is 60-90 wt%, and the content of the functional additive is 10-40 wt%.
9. The sodium-ion battery electrolyte according to claim 8, wherein, The non-aqueous organic solvent is selected from one or more of methyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; Preferably, the non-aqueous organic solvent is selected from propylene carbonate and / or ethyl methyl carbonate.
10. A sodium-ion battery, wherein the electrolyte in the sodium-ion battery is the sodium-ion battery electrolyte according to any one of claims 1-9.