Electrolyte for sodium-ion battery and sodium-ion battery thereof

Abstract

The application relates to the technical field of sodium ion batteries, in particular to an electrolyte for a sodium ion battery and a sodium ion battery thereof. The electrolyte comprises organic solvents, sodium salts and additives in percentage by weight. The additives comprise malonic acid compounds, nitrile compounds and tris(trimethylsilyl) phosphate. The additives of the electrolyte comprise macromolecular malonic acid compounds, which can effectively react with alkaline substances on the surface of a positive electrode material, form a film on the positive electrode, slow down or prevent the decomposition of the electrolyte solvent by the alkaline substances; meanwhile, the tris(trimethylsilyl) phosphate and the nitrile compounds in the electrolyte can effectively inhibit the oxidation reaction of Fe and Ni in the positive electrode and prevent the reduction of Fe and Ni in the negative electrode; the above-mentioned joint action can effectively improve the cycle life of the sodium ion battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more particularly to an electrolyte for sodium-ion batteries and a sodium-ion battery thereof. Background Technology

[0002] Sodium is widely available and abundant, and its price is far lower than that of lithium. In recent years, with the soaring price of lithium, sodium-ion batteries have attracted widespread attention due to their potential cost reduction of 30-50% compared to lithium-ion batteries. Sodium-ion batteries have particularly attractive application prospects in energy storage, hybrid power, and lead-acid battery replacement.

[0003] Based on the cathode material, sodium ions can be classified into Na3V2(PO4)3 and NaNi. x Fe y Mn z O2, Prussian blue, and three types of batteries; NaNi x Fe y Mn z O2 sodium-ion batteries are favored because they have a higher energy density than Na3V2(PO4)3 sodium-ion batteries and a longer cycle life than Prussian blue sodium-ion batteries.

[0004] NaNi x Fe y Mn z In the preparation of O2 cathode materials, an excess of Na is added to obtain a cathode material with good crystallinity. Therefore, the material will always have a small amount of residual Na (existing as Na2O at high temperatures). When the temperature drops to room temperature, Na2O will adsorb CO2 and H2O from the air to form NaOH and Na2CO3, making the cathode material alkaline. Furthermore, Na is more alkaline than Li, therefore NaNi... x Fe y Mn z The alkalinity of O2 cathode materials is much higher than that of corresponding lithium-ion nickel-cobalt-manganese ternary cathode materials.

[0005] Because of its excessively high alkalinity, NaNi x Fe y Mn z The solvent components in the electrolyte of sodium-ion batteries (O2) will react with NaNi x Fe y Mn zThe NaOH and Na2CO3 on the surface of the O2 positive electrode material undergo a slow chemical reaction, producing gas. Over time, the amount of gas produced increases. For steel-cased batteries, the CID (Cellular Injection Discharge) may flip, causing the battery to stop supplying power and fail. For pouch and aluminum-cased batteries, the battery may bulge or the casing may bulge, leading to cracks at the welds, electrolyte leakage, and water absorption by the electrolyte, resulting in battery failure and potentially causing fires or explosions. Simultaneously, the Fe and Ni in the material have strong oxidizing properties. Under high temperatures or high voltages, direct contact with the electrolyte can catalyze its decomposition, accelerating electrolyte consumption and causing thickening of the positive electrode CEI (Cellular Electrode Injection) film and increased impedance. Furthermore, Fe and Ni can easily migrate to the negative electrode with charge, damaging the negative electrode SEI film and reducing cycle life. Summary of the Invention

[0006] This invention provides an electrolyte for sodium-ion batteries and a sodium-ion battery thereof, to solve the problems of existing NaNi electrolytes. x Fe y Mn z The defect in O2 sodium-ion batteries is that the electrolyte and the positive electrode material are prone to side reactions, which affects the performance of sodium-ion batteries.

[0007] In a first aspect, the present invention provides an electrolyte for sodium-ion batteries, comprising an organic solvent, a sodium salt, and additives; said additives include sebacic acid compounds, nitrile compounds, and tris(trimethylsilane)phosphate esters.

[0008] In the above-described solution, the electrolyte for sodium-ion batteries of the present invention includes an organic solvent, a sodium salt, and additives. The additives form a film on the positive electrode of the sodium-ion battery, which can prevent the occurrence of side reactions between the positive electrode material and the electrolyte, and effectively improve the cycle life of the sodium-ion battery. The additives include sebacic acid compounds, nitrile compounds, and tris(trimethylsilane) phosphates. The large molecular weight sebacic acid compounds in the additives can effectively react with alkaline substances on the surface of the positive electrode material and form a film on the positive electrode, slowing down or preventing the decomposition of the electrolyte solvent by alkaline substances. At the same time, the tris(trimethylsilane) phosphates and nitrile substances in the electrolyte can effectively inhibit the oxidation reaction of Fe and Ni in the positive electrode and prevent their reduction in the negative electrode. The combined effect of these factors can effectively improve the cycle life of the sodium-ion battery.

[0009] In one possible design, the sebacic acid compound is selected from one or more of 1,3-bis(p-carboxyphenoxy)propane-sedacid, 1,6-bis(p-carboxyphenoxy)hexane-sedacid, fumaric acid-sedacid, and fatty acid dimer-sedacid.

[0010] By specifically selecting the type of sebacic acid compound, better synergistic effects can be achieved with nitrile compounds and tris(trimethylsilane)phosphates to improve the cycle life of sodium-ion batteries.

[0011] In one possible design, the nitrile compound is selected from one or more of succinic acid, adiponitrile, and hexanetrionitrile.

[0012] By specifically selecting the type of nitrile compound, better synergy can be achieved with sebacic acid compounds and tris(trimethylsilane) phosphates to improve the cycle life of sodium-ion batteries.

[0013] In one possible design, the organic solvent is composed of cyclic carbonates, chain carbonates, and chain ethers; by weight, the electrolyte comprises 10-20 parts of the sodium salt, 10-30 parts of the cyclic carbonate, 20-60 parts of the chain carbonate, 5-10 parts of the chain ether, 0.1-2 parts of the sebacic acid compound, 0.1-2 parts of the nitrile compound, and 0.1-2 parts of the tris(trimethylsilane) phosphate.

[0014] In one possible design, the electrolyte comprises, by weight, 13-17 parts of the sodium salt, 22-24 parts of the cyclic carbonate, 46-53 parts of the chain carbonate, 8-10 parts of the chain ether, 0.4-1 part of the sebacic acid compound, 0.5-1 part of the nitrile compound, and 0.6-1 part of the tris(trimethylsilane) phosphate.

[0015] In the above scheme, by selecting a specific ratio of raw materials, the synergistic effect between the raw materials can be better achieved, thereby improving the cycle life of sodium-ion batteries.

[0016] In one possible design, the cyclic carbonate is selected from one or both of ethylene carbonate and propylene carbonate.

[0017] In one possible design, the chain carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and methyl propyl carbonate.

[0018] In one possible design, the chain ether is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0019] In the above scheme, by selecting a specific type of organic solvent, it is possible to achieve better synergy with other raw materials, thereby improving the cycle life of sodium-ion batteries.

[0020] In one possible design, the sodium salt is selected from one or more of sodium hexafluorophosphate, sodium perchlorate, and sodium tetrafluoroborate.

[0021] In the above scheme, by selecting a specific type of sodium salt, it is possible to achieve better synergy with other raw materials, thereby improving the cycle life of sodium-ion batteries.

[0022] In a second aspect, the present invention provides a sodium-ion battery comprising the electrolyte described above.

[0023] In one possible design, the sodium-ion battery is NaNi. x Fe y Mn z O2 sodium-ion battery.

[0024] The present invention provides an electrolyte for sodium-ion batteries comprising an organic solvent, a sodium salt, and additives. The additives include sebacic acid compounds, nitrile compounds, and tris(trimethylsilane)phosphate esters. The macromolecular sebacic acid compounds in the additives can effectively react with alkaline substances on the surface of the positive electrode material and form a film on the positive electrode, thus slowing down or preventing the decomposition of the electrolyte solvent by alkaline substances. At the same time, the tris(trimethylsilane)phosphate esters and nitrile substances in the electrolyte can effectively inhibit the oxidation reaction of Fe and Ni in the positive electrode and prevent their reduction in the negative electrode. The combined effect of these factors can effectively improve the cycle life of sodium-ion batteries. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Example 1

[0027] This embodiment provides an electrolyte for sodium-ion batteries, the preparation method of which is as follows:

[0028] An electrolyte is prepared by mixing 16g of sodium hexafluorophosphate, 24g of ethylene carbonate, 50g of dimethyl carbonate, 8g of diethylene glycol dimethyl ether, 0.8g of 1,3-bis(p-carboxyphenoxy)propane-sepiaric acid, 0.6g of succinic acid, and 0.6g of tris(trimethylsilane) phosphate.

[0029] Example 2

[0030] This embodiment provides an electrolyte for sodium-ion batteries, the preparation method of which is as follows:

[0031] An electrolyte is prepared by mixing 17g of sodium hexafluorophosphate, 24g of propylene carbonate, 46g of dimethyl carbonate, 10g of tetraethylene glycol dimethyl ether, 1.0g of 1,6-bis(p-carboxyphenoxy)hexane-sebacic acid, 1.0g of hexanetrionitrile, and 1g of tris(trimethylsilane) phosphate.

[0032] Example 3

[0033] This embodiment provides an electrolyte for sodium-ion batteries, the preparation method of which is as follows:

[0034] An electrolyte is prepared by mixing 13g of sodium hexafluorophosphate, 22g of ethylene carbonate, 53g of dimethyl carbonate, 8g of ethylene glycol dimethyl ether, 0.4g of fumaric-sebacic acid, 0.5g of adiponitrile, and 0.6g of tris(trimethylsilane) phosphate evenly.

[0035] Example 4

[0036] This embodiment provides an electrolyte for sodium-ion batteries, the preparation method of which is as follows:

[0037] An electrolyte is prepared by mixing 10g of sodium hexafluorophosphate, 19.7g of ethylene carbonate, 60g of dimethyl carbonate, 10g of ethylene glycol dimethyl ether, 0.1g of fumaric-sebacic acid, 0.1g of adiponitrile, and 0.1g of tris(trimethylsilane) phosphate.

[0038] Example 5

[0039] This embodiment provides an electrolyte for sodium-ion batteries, the preparation method of which is as follows:

[0040] An electrolyte is prepared by mixing 20g of sodium hexafluorophosphate, 30g of ethylene carbonate, 34g of dimethyl carbonate, 10g of ethylene glycol dimethyl ether, 2g of fumaric acid-sebacic acid, 2g of adiponitrile, and 2g of tris(trimethylsilane) phosphate.

[0041] Comparative Example 1

[0042] The difference from Example 1 is that no additives are added to the electrolyte.

[0043] Comparative Example 2

[0044] The difference from Example 2 is that no additives are added to the electrolyte.

[0045] Comparative Example 3

[0046] The difference from Example 3 is that no additives are added to the electrolyte.

[0047] Comparative Example 4

[0048] The difference from Example 3 is that the additive does not contain fumaric acid-sebacic acid.

[0049] Comparative Example 5

[0050] The difference from Example 3 is that the additive does not contain nitrile compounds.

[0051] Comparative Example 6

[0052] The difference from Example 3 is that the additive does not contain tris(trimethylsilane) phosphate.

[0053] The electrolytes prepared in the examples and comparative examples were injected into a 26650-3.0Ah sodium-ion battery cell (positive electrode NaFe). 1 / 3 Ni 1 / 3 Mn 1 / 3 A battery is made by using O3 and hard carbon as the negative electrode.

[0054] The prepared battery was subjected to a cycle test at 50℃ for 1000 cycles. The discharge capacity of the battery was recorded at the first and 1000th cycles, and the discharge retention rate was calculated. Discharge retention rate = (first discharge capacity / 1000th discharge capacity) * 100%. The experimental data are shown in Table 1 below.

[0055] Table 1. Comparison of cycle performance between batteries prepared in the examples and those prepared in the comparative examples.

[0056]

[0057] As shown in Table 1, the experimental data from Examples 1-5 demonstrate that sodium-ion batteries using an additive composed of sebacic acid compounds, nitrile compounds, and tris(trimethylsilane) phosphate exhibit excellent discharge retention and cycle life. Among these, the sodium-ion battery using the additive from Example 2 exhibits the best cycle life, with an internal resistance increase of approximately 1 mΩ before and after cycling. The experimental data from Comparative Examples 1-3 show that sodium-ion batteries without the additive have poorer cycle life, with a significant increase in internal resistance before and after cycling. The comparison results from Example 3 and Comparative Examples 4-6 indicate that the three components in the additive—sebacic acid compounds, nitrile compounds, and tris(trimethylsilane) phosphate—have a synergistic relationship. The absence of any one of these components affects the discharge retention and cycle life of the sodium-ion battery, while the synergistic effect among them more effectively improves the cycle life of the sodium-ion battery.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sodium-ion battery, characterized in that, The electrolyte comprises organic solvents, sodium salts and additives; the additives comprise succinic acid compounds, nitrile compounds and tri (trimethylsilyl) phosphate; the organic solvents are composed of cyclic carbonates, chain carbonates and chain ethers; the electrolyte comprises 10-20 parts of the sodium salt, 10-30 parts of the cyclic carbonate, 20-60 parts of the chain carbonate, 5-10 parts of the chain ether, 0.1-2 parts of the succinic acid compound, 0.1-2 parts of the nitrile compound and 0.1-2 parts of the tri (trimethylsilyl) phosphate by weight; the sodium ion battery is NaNi x Fe y Mn z O2 sodium ion battery.

2. The sodium-ion battery of claim 1, wherein, The succinic acid compound is selected from one or more of 1,3-bis(p-carboxyphenoxy)propane-sebacic acid, 1,6-bis(p-carboxyphenoxy)hexane-sebacic acid, fumaric acid-sebacic acid, and fatty acid dimer-sebacic acid.

3. The sodium-ion battery of claim 1, wherein, The nitrile compound is selected from one or more of butanedinitrile, hexanedinitrile, and hexanetristnitrile.

4. The sodium-ion battery of claim 1, wherein, The organic solvent is composed of a cyclic carbonate, a chain carbonate, and a chain ether; the electrolyte includes 10-20 parts by weight of the sodium salt, 10-30 parts by weight of the cyclic carbonate, 20-60 parts by weight of the chain carbonate, 5-10 parts by weight of the chain ether, 0.1-2 parts by weight of the succinic acid compound, 0.1-2 parts by weight of the nitrile compound, and 0.1-2 parts by weight of the tris(trimethylsilyl)phosphate.

5. The sodium-ion battery of claim 4, wherein, The electrolyte includes 13-17 parts by weight of the sodium salt, 22-24 parts by weight of the cyclic carbonate, 46-53 parts by weight of the chain carbonate, 8-10 parts by weight of the chain ether, 0.4-1 part by weight of the succinic acid compound, 0.5-1 part by weight of the nitrile compound, and 0.6-1 part by weight of the tris(trimethylsilyl)phosphate.

6. The sodium-ion battery of claim 4, wherein, The cyclic carbonate is selected from one or both of ethylene carbonate and propylene carbonate.

7. The sodium-ion battery of claim 4, wherein, The chain carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, and methyl propyl carbonate.

8. The sodium-ion battery of claim 4, wherein, The chain ether is selected from one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

9. The sodium-ion battery of claim 1, wherein, The sodium salt is selected from one or more of sodium hexafluorophosphate, sodium perchlorate, and sodium tetrafluoroborate.

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