A sodium-ion battery electrolyte and its preparation method

Abstract

The present invention discloses a sodium-ion battery electrolyte and a preparation method thereof, relating to the technical field of energy materials; it includes a sodium salt, a non-aqueous solvent and an additive; the molar concentration of the sodium salt is 0.5-2 mol / L, and the mass percentage concentration of the additive is 2-5%; the additive includes fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate. The sodium-ion battery electrolyte disclosed by the present invention has high ionic conductivity, good electrochemical performance, a long cycle service life of the sodium-ion battery using the same, and excellent capacity retention rate.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and particularly to a sodium-ion battery electrolyte and a preparation method thereof. Background Art

[0002] With the rapid development of information technology, portable electronic devices have become increasingly popular, and the demand for high specific energy batteries has increased year by year. Sodium-ion batteries have broad application prospects in the fields of large-scale energy storage, electric vehicles, electric ships, and special engineering vehicles due to their significant advantages such as low price, rich sodium resources, high use safety, environmental friendliness, high voltage similar to lithium, low self-discharge rate, and high energy density.

[0003] The positive and negative electrode materials, electrolyte, and separator are important components of a sodium-ion battery. Among them, the electrolyte plays a role in transporting ions, and its physical and chemical properties and chemical composition not only determine the kinetic performance of sodium ions in the electrolyte but also determine the composition and structure of the solid electrolyte interphase (SEI) film on the electrode surface, which has an important impact on the rate performance, electrode structure stability, and cycle life of sodium-ion batteries.

[0004] Currently, the most commonly used sodium-ion battery electrolyte is an electrolyte with carbonate esters as solvents and sodium salts such as sodium hexafluorophosphate and / or sodium perchlorate as solutes. The solvents in this type of electrolyte have a relatively high melting point, high viscosity, and strong interaction with sodium ions, which to a certain extent limits the diffusion of sodium ions in the solution and is also not conducive to the desolvation of sodium ions at the electrode-electrolyte interface. In addition, when charging and discharging under high-rate conditions, the conductivity of these electrolytes is not sufficient to support such a large current density, and the large charge transfer impedance and SEI film impedance limit the transport of sodium ions. Other types of sodium-ion battery electrolytes on the market also have more or less technical defects such as gas decomposition and production, which deteriorate the electrical contact of each component in the battery, resulting in a small amount of deposition and the formation of dendrites. When the dendrites grow too fast, they may pierce the separator, causing safety hazards; they are flammable and become combustible fuels during thermal runaway, affecting the use safety.

[0005] To solve the above problems, Chinese Patent Application CN105811001A proposes a sodium-ion battery electrolyte formulation with sodium hexafluorophosphate, sodium perchlorate, or N-hydroxysulfonyl succinimide sodium as the electrolyte and sulfolane and ionic liquid as the solvents. When preparing this electrolyte, the water and oxygen content of the preparation environment needs to be strictly controlled, and the preparation needs to be carried out in an environment of less than 0.1 ppm. In addition, the manufacturing and processing processes of these electrolytes are relatively complex, and the manufacturing cost is high.

[0006] It can be seen that developing a sodium-ion battery electrolyte with high ionic conductivity, good electrochemical performance, long cycle life of the sodium-ion battery using it, and excellent capacity retention rate, as well as its preparation method, meets the market demand, has high market value and application prospects, and is of great significance for promoting the further development of sodium-ion batteries. Summary of the Invention

[0007] The main object of the present invention is to solve the above technical problems and provide a sodium-ion battery electrolyte with high ionic conductivity, good electrochemical performance, long cycle life of the sodium-ion battery using it, and excellent capacity retention rate, as well as its preparation method.

[0008] To achieve the above object, the present invention provides a sodium-ion battery electrolyte, which includes a sodium salt, a non-aqueous solvent, and an additive; the molar concentration of the sodium salt is 0.5 - 2 mol / L, and the mass percentage concentration of the additive is 2 - 5%; the additive includes fluoroethylene carbonate, 1 - propenyl - 1,3 - sultone, vinylene sulfate, and vinylene carbonate.

[0009] Preferably, the sodium salt is at least one of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, and sodium nitrate; more preferably, the sodium salt is sodium hexafluorophosphate.

[0010] Preferably, the non-aqueous solvent is at least one of propylene carbonate, ethyl methyl carbonate, and diethyl carbonate; more preferably, the non-aqueous solvent is a mixture formed by mixing propylene carbonate and ethyl methyl carbonate in a mass ratio of 2:3.

[0011] Preferably, the mass ratio of fluoroethylene carbonate, 1 - propenyl - 1,3 - sultone, vinylene sulfate, and vinylene carbonate is (1 - 2):(0.5 - 1):(0.5 - 1):(0.5 - 1).

[0012] Preferably, the additive further includes bicyclo[2.2.2]oct - 7 - ene - 2,3,5,6 - tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid.

[0013] Preferably, the imidazolium ionic liquid is at least one of 1 - butyl - 2,3 - dimethylimidazolium hexafluorophosphate, 1 - hexyl - 3 - methylimidazolium hexafluorophosphate, and 1 - ethyl - 2,3 - dimethylimidazolium hexafluorophosphate.

[0014] Preferably, the mass ratio of fluoroethylene carbonate, bicyclo[2.2.2]oct - 7 - ene - 2,3,5,6 - tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid is 1:(0.2 - 0.4):0.1:0.1.

[0015] Another object of the present invention is to provide a method for preparing the sodium-ion battery electrolyte, comprising the following steps: adding the sodium salt and the additive into the non-aqueous organic solvent, and mixing evenly to obtain the sodium-ion battery electrolyte.

[0016] Due to the application of the above technical solution, the present invention has the following beneficial effects:

[0017] (1) For the method for preparing the sodium-ion battery electrolyte disclosed in the present invention, the components can be directly mixed evenly, without special equipment, with less capital investment, high preparation efficiency and high finished product qualification rate, simple process, convenient operation, and suitable for continuous large-scale production.

[0018] (2) The sodium-ion battery electrolyte disclosed in the present invention comprises a sodium salt, a non-aqueous solvent and an additive; the molar concentration of the sodium salt is 0.5 - 2 mol / L, and the mass percentage concentration of the additive is 2 - 5%; the additive comprises fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate; through the reasonable selection of the types and content ratios of the sodium salt, the non-aqueous solvent and the additive, they can better cooperate with each other and act together, thereby endowing the sodium-ion battery electrolyte product with high ionic conductivity, good electrochemical performance, long cycle service life of the sodium-ion battery using it, and excellent capacity retention rate.

[0019] (3) For the sodium-ion battery electrolyte disclosed in the present invention, the additive further comprises bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate and imidazolium ionic liquid; through the interaction and cooperation between the above components and other components in the electrolyte, the alkalinity on the surface of the positive electrode material can be neutralized, the decomposition effect of the alkalinity of the metal oxide on the carbonate can be inhibited, and at the same time, the hydrolysis of the electrolyte can be inhibited, so that during the storage, charging and discharging of the sodium-ion battery, the generation of gas can be reduced, thereby improving the cycle performance of the sodium-ion battery; in addition, compared with the traditional electrolyte, it shows higher ionic conductivity and lower sodium

[0020] desolvation energy, ensuring that the sodium-ion battery has excellent high-power performance. The sodium-ion battery using this electrolyte shows excellent capacity retention rate and cycle service life. Specific Embodiments

[0021] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious variations. Example 1

[0022] A sodium-ion battery electrolyte, comprising a sodium salt, a non-aqueous solvent, and an additive; the molar concentration of the sodium salt is 1 mol / L, and the mass percentage concentration of the additive is 4%; the additive includes fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate.

[0023] The sodium salt is sodium hexafluorophosphate; the non-aqueous solvent is a mixture formed by mixing propylene carbonate and ethyl methyl carbonate in a mass ratio of 2:3; the mass ratio of fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate is 2:0.5:1:0.5;

[0024] A method for preparing the sodium-ion battery electrolyte, comprising the following steps: adding the sodium salt and the additive to the non-aqueous organic solvent, and mixing evenly to obtain the sodium-ion battery electrolyte. Example 2

[0025] A sodium-ion battery electrolyte, comprising a sodium salt, a non-aqueous solvent, and an additive; the molar concentration of the sodium salt is 1 mol / L, and the mass percentage concentration of the additive is 3.5%; the additive includes fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate.

[0026] The sodium salt is sodium perchlorate; the non-aqueous solvent is a mixture formed by mixing propylene carbonate and ethyl methyl carbonate in a mass ratio of 2:3; the mass ratio of fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate is 2:0.5:0.5:0.5; the additive further includes bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid; the imidazolium ionic liquid is 1-butyl-2,3-dimethylimidazolium hexafluorophosphate; the mass ratio of fluoroethylene carbonate, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid is 1:0.2:0.1:0.1.

[0027] A method for preparing the sodium-ion battery electrolyte, comprising the following steps: adding the sodium salt and the additive to the non-aqueous organic solvent, and mixing evenly to obtain the sodium-ion battery electrolyte. Example 3

[0028] A sodium-ion battery electrolyte, comprising a sodium salt, a non-aqueous solvent, and an additive; the molar concentration of the sodium salt is 1.3 mol / L, and the mass percentage concentration of the additive is 4.5%; the additive includes fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate.

[0029] The sodium salt is a mixture formed by mixing sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, and sodium nitrate in a mass ratio of 1:1:0.3:0.2; the non-aqueous solvent is a mixture formed by mixing propylene carbonate and diethyl carbonate in a mass ratio of 2:3; the mass ratio of fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate is 2:1:1:0.5; the additive further includes bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid; the imidazolium ionic liquid is 1-hexyl-3-methylimidazolium hexafluorophosphate; the mass ratio of fluoroethylene carbonate, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid is 1:0.25:0.1:0.1.

[0030] A method for preparing the sodium-ion battery electrolyte includes the following steps: adding the sodium salt and the additive to the non-aqueous organic solvent, and mixing evenly to obtain the sodium-ion battery electrolyte. Example 4

[0031] A sodium-ion battery electrolyte includes a sodium salt, a non-aqueous solvent, and an additive; the molar concentration of the sodium salt is 1.6 mol / L, and the mass percentage concentration of the additive is 4.5%; the additive includes fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate.

[0032] The sodium salt is sodium tetrafluoroborate; the non-aqueous solvent is a mixture formed by mixing propylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:1:1; the mass ratio of fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate is 2:0.5:1:1.

[0033] The additive further includes bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid; the imidazolium ionic liquid is a mixture formed by mixing 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium hexafluorophosphate, and 1-ethyl-2,3-dimethylimidazolium hexafluorophosphate in a mass ratio of 1:2:1; the mass ratio of fluoroethylene carbonate, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid is 1:0.35:0.1:0.1.

[0034] A preparation method of the sodium-ion battery electrolyte includes the following steps: adding the sodium salt and the additive into the non-aqueous organic solvent, and mixing evenly to obtain the sodium-ion battery electrolyte. Example 5

[0035] A sodium-ion battery electrolyte includes a sodium salt, a non-aqueous solvent, and an additive; the molar concentration of the sodium salt is 2 mol / L, and the mass percentage concentration of the additive is 5%; the additive includes fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate.

[0036] The sodium salt is a mixture formed by mixing sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, and sodium nitrate in a mass ratio of 1:1:2:1; the non-aqueous solvent is a mixture formed by mixing propylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 1:2:1; the mass ratio of fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate is 2:1:1:1; the additive further includes bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid; the imidazolium ionic liquid is 1-ethyl-2,3-dimethylimidazolium hexafluorophosphate; the mass ratio of fluoroethylene carbonate, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid is 1:0.4:0.1:0.1.

[0037] A preparation method of the sodium-ion battery electrolyte includes the following steps: adding the sodium salt and the additive into the non-aqueous organic solvent, and mixing evenly to obtain the sodium-ion battery electrolyte.

[0038] Comparative Example 1

[0039] The present invention provides a sodium-ion battery electrolyte, whose formulation and preparation method are similar to those of Example 2, except that no additive is added.

[0040] Comparative Example 2

[0041] The present invention provides a sodium-ion battery electrolyte, whose formulation and preparation method are similar to those of Example 2, except that bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid are not added.

[0042] To further illustrate the beneficial technical effects of the sodium-ion battery electrolytes prepared in the embodiments of the present invention, the sodium-ion battery electrolytes prepared in each example were used as electrolytes, the XN33S sodium battery positive electrode produced by Jiangsu Xiangying New Energy Technology Co., Ltd. was used as the positive electrode, and a 16-mm-diameter sodium sheet was used as the negative electrode to assemble a button battery, which was left standing for 8 h, and the battery performance tests were carried out separately. At a voltage range of 1.0 - 4.2 V and a current density of 0.1 C, room-temperature charge and discharge were carried out, and the first charge-discharge efficiency was recorded. At room temperature, it was charged at a constant current of 1 C to 4.0 V, then charged at a constant voltage until the current was 0.05 C, and then discharged at a constant current of 1 / 3 C to 1.0 V. Charging / discharging was carried out in this way, and the capacity retention rate after 100 cycles was calculated. The test results are shown in Table 1.

[0043] Table 1

[0044] Project Initial charge-discharge efficiency (%) Capacity retention rate after 100 cycles (%) Example 1 95.17 95.5 Example 2 96.03 97.1 Example 3 96.35 97.7 Example 4 96.61 98.2 Example 5 96.90 98.6 Comparative Example 1 93.18 76.8 Comparative Example 2 94.46 93.2

[0045] As can be seen from Table 1, the sodium-ion battery using the sodium-ion battery electrolyte disclosed in the embodiments of the present invention has more excellent first charge-discharge efficiency and cycle service life compared with the products of the comparative examples; the addition of the additive is beneficial to improving the above performances.

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A sodium-ion battery electrolyte, characterized in that, It includes sodium salt, non-aqueous solvent and additive; the molar concentration of the sodium salt is 0.5 - 2 mol / L, and the mass percentage concentration of the additive is 2 - 5%; the additive includes fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, vinylene carbonate, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate and imidazolium ionic liquid.

2. The sodium-ion battery electrolyte according to claim 1, characterized in that, The sodium salt is at least one of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, and sodium nitrate.

3. The sodium-ion battery electrolyte according to claim 1, characterized in that, The non-aqueous solvent is at least one of propylene carbonate, ethyl methyl carbonate, and diethyl carbonate.

4. The sodium-ion battery electrolyte according to claim 1, characterized in that, The mass ratio of fluoroethylene carbonate, 1-propenyl-1,3-sultone, vinylene sulfate, and vinylene carbonate is (1 - 2):(0.5 - 1):(0.5 - 1):(0.5 - 1).

5. The sodium-ion battery electrolyte according to claim 1, characterized in that, The imidazolium ionic liquid is at least one of 1-butyl-2,3-dimethylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium hexafluorophosphate, and 1-ethyl-2,3-dimethylimidazolium hexafluorophosphate.

6. The sodium-ion battery electrolyte according to claim 1, characterized in that, The mass ratio of fluoroethylene carbonate, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, triethanolamine borate, and imidazolium ionic liquid is 1:(0.2 - 0.4):0.1:0.

1.

7. A method for preparing the sodium-ion battery electrolyte according to any one of claims 1-6, characterized in that, It includes the following steps: adding the sodium salt and the additive into the non-aqueous organic solvent, and mixing evenly to obtain the electrolyte for sodium-ion battery.