Crown ether compound, rechargeable battery electrolyte and rechargeable battery

Abstract

A crown ether compound, a rechargeable battery electrolyte and a rechargeable battery, wherein the rechargeable battery electrolyte is composed of a rechargeable battery electrolyte main liquid and an electrolyte additive, and the electrolyte additive is a crown ether compound represented by formula (i) or formula (ii): the rechargeable battery electrolyte contains the above-mentioned electrolyte additive, which can effectively isolate electrodes and electrolyte, thereby inhibiting side reactions between the electrolyte and the positive and negative electrodes of the battery, thereby improving the battery's kinetic performance and reducing the consumption of the electrolyte, thereby achieving an increase in the battery's cycle life.

Description

Technical Field

[0001] The invention relates to the field of metal batteries, and in particular to a crown ether compound, a rechargeable battery electrolyte and a rechargeable battery. Background Art

[0002] Lithium metal batteries have attracted much attention due to their high energy density, high operating voltage, no memory effect, long cycle life, no pollution, light weight and low self-discharge, etc. However, during the cycle, lithium metal batteries often face the problems of dendrite formation and frequent side reactions, resulting in poor cycle stability and safety hazards.

[0003] In order to solve these problems, related technologies have proposed a variety of improvement strategies, such as liquid electrolyte modification, construction of solid and quasi-solid electrolytes, design of interface protective films, and construction of three-dimensional conductive skeletons, thereby significantly improving the cycle performance of lithium metal batteries. Among them, the liquid electrolyte modification method is simple, does not change the existing process, has good practical prospects, and during the cycle, the electrolyte directly contacts the positive and negative electrodes; through electrolyte modification, a dense protective film can be constructed at the interface of the positive and negative electrodes at the same time, effectively isolating the electrodes and the electrolyte, while reducing side reactions, which has greater advantages. Therefore, the present application discloses an electrolyte additive for high-voltage lithium metal batteries, which can effectively solve the problems of dendrite formation and positive and negative electrode side reactions, and provide good long-cycle stability under high voltage conditions. It is simple to prepare, low cost, and suitable for various lithium metal electrolytes. Summary of the invention

[0004] Based on the above-mentioned technical problems, the present invention provides a crown ether compound, a rechargeable battery electrolyte and a rechargeable battery, which are used to solve the technical problems of the existing rechargeable battery organic electrolyte additives being few in variety, complex in preparation and high in cost.

[0005] To achieve the above object, according to one aspect of the present invention, the present invention provides a crown ether compound used as an electrolyte additive, which has a chemical structure shown in formula (i) or formula (ii):

[0006]

[0007] The crown ether compound of formula (i) can be synthesized by the synthesis routes shown in the following equations (1) and (2), and the crown ether compound of formula (ii) can be synthesized by the synthesis routes shown in the following equations (1) and (3):

[0008]

[0009] In the above formula (2), the -Br of the compound containing -Br may also be other halogen groups; in the above formula (3), the -I of the compound containing -I may also be other halogen groups.

[0010] According to another aspect of the present invention, the present invention further provides a rechargeable battery electrolyte, which is composed of a rechargeable battery electrolyte main solution and an electrolyte additive, wherein the electrolyte additive is the above-mentioned crown ether-based compound.

[0011] As a further preferred technical solution of the present invention, the rechargeable battery electrolyte is one of ester electrolyte, ether electrolyte, nitrile electrolyte, sulfone electrolyte, aqueous electrolyte, mixed electrolyte, and ionic liquid electrolyte.

[0012] As a further preferred technical solution of the present invention, the ratio of the mass of the electrolyte additive to the volume of the rechargeable battery electrolyte is 0.01-100g:1L.

[0013] According to another aspect of the present invention, the present invention further provides a rechargeable battery, which uses the above-mentioned rechargeable battery electrolyte.

[0014] As a further preferred technical solution of the present invention, the rechargeable battery is one of a metal lithium / lithium ion battery, a metal sodium / sodium ion battery, a metal potassium / potassium ion battery, a metal magnesium / magnesium ion battery, a metal aluminum / aluminum ion battery, a metal zinc / zinc ion battery, and an iron battery.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0016] The crown ether-based compound of the present invention is used as an electrolyte additive, and it uses 15-crown ether-5 with strong cation coordination ability as a structural mother core, thereby ensuring that the additive molecule has a strong coordination center, and can be adsorbed on the positive and negative electrode surfaces to coordinate and complex with a large number of lithium ions and participate in the generation of CEI and SEI interface films of fast ion conduction; by modifying the 15-crown ether-5 mother core with different substituents through side chain engineering, the uniformity of the accumulation of the additive molecule at the positive and negative electrode interfaces and the efficiency and stability of film formation can be effectively regulated, thereby regulating the uniformity of the distribution of metal ions at the interface, and effectively inhibiting the microstructural phase change of the positive electrode active material and the growth of the negative electrode metal dendrite. Therefore, the rechargeable battery electrolyte using the electrolyte additive of the present invention can effectively isolate the electrode and the electrolyte, thereby inhibiting the side reactions of the electrolyte and the positive and negative electrodes of the battery, so that the kinetic performance of the battery is improved and the consumption of the electrolyte is reduced, and the battery cycle life is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] Figure 1-1The cycling curves of Li / Al batteries assembled with blank ester LiPF6 electrolyte and modified electrolytes containing 15-crown ether-5, alkyl chain 15-crown ether-5, and sulfonic acid 15-crown ether-5, respectively.

[0019] Figure 1-2 The cycling curves of Li / Li batteries assembled with blank ester LiPF6 electrolyte and modified electrolytes containing 15-crown ether-5, alkyl chain 15-crown ether-5, and sulfonic acid 15-crown ether-5, respectively.

[0020] Figure 1-3 Performance test diagrams of lithium manganese oxide / Li batteries assembled with blank ester LiPF6 electrolyte and modified electrolytes containing 15-crown ether-5, alkyl chain 15-crown ether-5, and sulfonic acid 15-crown ether-5, respectively.

[0021] Figure 2-1 The cycling curves of Li / Al batteries assembled with blank ester LiPF6 electrolyte and modified electrolytes containing 15-crown ether-5, alkyl chain 15-crown ether-5, and fluorinated 15-crown ether-5, respectively.

[0022] Figure 2-2 The cycling curves of Li / Li batteries assembled with blank ester LiPF6 electrolyte and modified electrolytes containing 15-crown ether-5, alkyl chain 15-crown ether-5, and fluorinated 15-crown ether-5, respectively.

[0023] Figure 2-3 Performance test diagrams of lithium manganese oxide / Li batteries assembled with blank ester LiPF6 electrolyte and modified electrolytes containing 15-crown ether-5, alkyl chain 15-crown ether-5, and fluorinated 15-crown ether-5, respectively.

[0024] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0026] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0027] Embodiment 1:

[0028] This embodiment provides a method for preparing a rechargeable battery electrolyte containing a sulfonic acid 15-crown ether-5 electrolyte additive (hereinafter referred to as a modified electrolyte), comprising the following steps:

[0029] 0.5 g of sulfonic acid 15-crown ether-5 is dissolved in 1 L of rechargeable battery electrolyte to prepare a rechargeable battery electrolyte; the rechargeable battery electrolyte used contains 1 mol / L LiPF6, and its solvent is dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate in a volume ratio of 1:1:1. The rechargeable battery electrolyte is also called ester LiPF6 electrolyte in the following experiments.

[0030] In addition, as a control experiment of Example 1, the preparation method of Example 1 was referred to, and 15-crown ether-5 and alkyl chain 15-crown ether-5 were used to replace sulfonic acid 15-crown ether-5 in equal amounts to prepare a modified electrolyte containing 15-crown ether-5 and a modified electrolyte containing alkyl chain 15-crown ether-5.

[0031] The chemical structures of the above-mentioned 15-crown ether-5, alkyl chain 15-crown ether-5 and sulfonic acid 15-crown ether-5 are:

[0032]

[0033] In order to study the effect of adding sulfonic acid 15-crown ether-5 on the performance of ester LiPF6 electrolyte, the following three experiments were conducted in this example:

[0034] Experiment 1-1

[0035] Four identical Li / Al button-type symmetrical mold full cells (lithium foil diameter of 1 cm) were assembled, and 0.1 mL of ester LiPF6 electrolyte (marked as blank), 0.1 mL of modified electrolyte containing 15-crown ether-5 (marked as control 1), 0.1 mL of modified electrolyte containing alkyl chain 15-crown ether-5 (marked as control 2), and 0.1 mL of modified electrolyte containing sulfonic acid 15-crown ether-5 prepared in Example 1 (marked as sulfonic acid additive) were respectively loaded into the four mold full cells; then the cycle stability of the four batteries was tested at a current density of 0.5 mV / s, and the results are as follows: Figure 1-1 shown.

[0036] According to Figure 1, compared with the Li / Al battery assembled with the blank ester LiPF6 electrolyte, the modified electrolyte containing 15-crown ether-5, and the modified electrolyte containing alkyl chain 15-crown ether-5, the voltage of the Li / Al battery with the modified electrolyte containing sulfonic acid 15-crown ether-5 of Example 1 can be stabilized to above 5.0V, indicating that the addition of sulfonic acid 15-crown ether-5 to the blank ester LiPF6 electrolyte can significantly improve the high voltage stability of the electrolyte, and is significantly better than the modified electrolyte formed by adding 15-crown ether-5 (Control 1) or alkyl chain 15-crown ether-5 (Control 2).

[0037] Experiment 1-2

[0038] Four identical Li / Li button-type symmetrical mold full cells (lithium foil diameter of 1 cm) were assembled, and 0.1 mL of ester LiPF6 electrolyte (marked as blank), 0.1 mL of modified electrolyte containing 15-crown ether-5 (marked as control 1), 0.1 mL of modified electrolyte containing alkyl chain 15-crown ether-5 (marked as control 2), and 0.1 mL of modified electrolyte containing sulfonic acid 15-crown ether-5 prepared in Example 1 (marked as sulfonic acid additive) were respectively loaded into the four mold full cells; then the cycle stability of the four batteries was tested at a surface loading of 1 mAh·cm-2 and a current density of 2 mA·cm-2, and the results were as follows: Figure 1-2 shown.

[0039] according to Figure 1-2 It can be seen that compared with the Li / Li battery assembled with a blank ester electrolyte, a modified electrolyte containing 15-crown ether-5, and a modified electrolyte containing an alkyl chain 15-crown ether-5, the stable cycle time of the Li / Li battery containing a sulfonic acid 15-crown ether-5 modified electrolyte is increased from 30 h to more than 300 h, indicating that the addition of sulfonic acid 15-crown ether-5 to the ester electrolyte can significantly improve the cycle stability of the Li / Li battery, and is significantly better than the modified electrolyte formed by adding 15-crown ether-5 (control 1) or alkyl chain 15-crown ether-5 (control 2).

[0040] Experiments 1-3

[0041] Assemble four identical lithium nickel manganese oxide / Li full batteries (positive electrode sheet diameter is 1 cm, lithium nickel manganese oxide surface loading is 1.2 mg cm -2, lithium foil diameter 1 cm), 0.1 mL of ester LiPF6 electrolyte (marked as blank), 0.1 mL of modified electrolyte containing 15-crown ether-5 (marked as control 1), 0.1 mL of modified electrolyte containing alkyl chain 15-crown ether-5 (marked as control 2), and 0.1 mL of modified electrolyte containing sulfonic acid 15-crown ether-5 prepared in Example 1 (marked as sulfonic acid additive) were loaded into four mold full batteries respectively; then the cycle stability, capacity and retention rate of the four batteries were tested at a current density of 2C, and the results were as follows: Figure 1-3 shown.

[0042] according to Figure 1-3 It can be seen that at an ultra-high current density of 2C, the capacity of the lithium nickel manganese oxide / Li battery containing sulfonic acid 15-crown ether-5 modified electrolyte is nearly 20mAh / g higher than that of the lithium nickel manganese oxide / Li battery of the blank ester LiPF6 electrolyte and the two control groups; the lithium nickel manganese oxide / Li battery of the blank ester LiPF6 electrolyte showed a trend of decreasing capacity from the beginning of the cycle, and the capacity was only 27mAh / g after 800 cycles, while the lithium nickel manganese oxide / Li battery containing sulfonic acid 15-crown ether-5 modified electrolyte can stably cycle 800 cycles without any decrease in capacity. It can be seen that the cycle stability, capacity and retention rate of the lithium nickel manganese oxide / Li battery containing sulfonic acid 15-crown ether-5 modified electrolyte are significantly improved, indicating that the addition of sulfonic acid 15-crown ether-5 to the ester LiPF6 electrolyte can significantly improve the coulombic efficiency, cycle stability, capacity and retention rate of the battery.

[0043] Embodiment 2:

[0044] This embodiment provides a method for preparing a rechargeable battery electrolyte containing a fluorinated 15-crown ether-5 electrolyte additive (hereinafter referred to as a modified electrolyte), comprising the following steps:

[0045] 0.5 g of fluorinated 15-crown ether-5 was dissolved in 1 L of a rechargeable battery electrolyte to prepare a rechargeable battery electrolyte; the rechargeable battery electrolyte used contained 1 mol / L LiPF6, and its solvent was dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate in a volume ratio of 1:1:1. The rechargeable battery electrolyte was also called an ester LiPF6 electrolyte in the following experiments.

[0046] In addition, as a control experiment of Example 1, the preparation method of Example 1 was referred to, and 15-crown ether-5 and alkyl chain 15-crown ether-5 were used to replace the fluorinated 15-crown ether-5 in equal amounts to prepare a modified electrolyte containing 15-crown ether-5 and a modified electrolyte containing alkyl chain 15-crown ether-5.

[0047] The chemical structures of the above-mentioned 15-crown ether-5, alkyl chain 15-crown ether-5 and fluorinated 15-crown ether-5 are:

[0048]

[0049] In order to study the effect of adding fluorinated 15-crown ether-5 on the performance of ester LiPF6 electrolyte, the following three experiments were conducted in this example:

[0050] Experiment 2-1

[0051] Four identical Li / Al button-type symmetrical mold full cells (lithium foil diameter of 1 cm) were assembled, and 0.1 mL of ester LiPF6 electrolyte (marked as blank), 0.1 mL of modified electrolyte containing 15-crown ether-5 (marked as control 1), 0.1 mL of modified electrolyte containing alkyl chain 15-crown ether-5 (marked as control 2), and 0.1 mL of modified electrolyte containing fluorinated 15-crown ether-5 prepared in Example 2 (marked as fluorine-based additive) were respectively loaded into the four mold full cells; then the cycle stability of the four batteries was tested at a current density of 0.5 mV / s, and the results were as follows: Figure 2-1 shown.

[0052] According to Figure 1, compared with the blank ester LiPF6 electrolyte and the Li / Al battery modified with the electrolyte of control 1 and control 2, the voltage of the Li / Al battery containing the fluorinated 15-crown ether-5 modified electrolyte can be stabilized to above 5.0V, indicating that the addition of fluorinated 15-crown ether-5 to the blank ester LiPF6 electrolyte can significantly improve the high voltage stability of the electrolyte, and is better than control 1 and control 2.

[0053] Experiment 2-2

[0054] Four identical Li / Li button-type symmetrical mold full cells (lithium foil diameter of 1 cm) were assembled, and 0.1 mL of ester LiPF6 electrolyte (marked as blank), 0.1 mL of modified electrolyte containing 15-crown ether-5 (marked as control 1), 0.1 mL of modified electrolyte containing alkyl chain 15-crown ether-5 (marked as control 2), and 0.1 mL of modified electrolyte containing fluorinated 15-crown ether-5 prepared in Example 2 (marked as fluorine-based additive) were respectively loaded into the four mold full cells; then the cycle stability of the four batteries was tested at a surface loading of 1 mAh·cm-2 and a current density of 2 mA·cm-2, and the results were as follows: Figure 2-2 shown.

[0055] according to Figure 2-2It can be seen that compared with the Li / Li batteries containing blank ester electrolyte and control 1 and control 2, the stable cycle time of the Li / Li battery containing fluorinated 15-crown ether-5 modified electrolyte is increased from 30h to more than 300h, indicating that the addition of fluorinated 15-crown ether-5 to the ester electrolyte can significantly improve the cycle stability of the Li / Li battery, and is better than control 1 and control 2.

[0056] Experiment 2-3

[0057] Assemble four identical lithium nickel manganese oxide / Li full batteries (positive electrode sheet diameter is 1 cm, lithium nickel manganese oxide surface loading is 1.2 mg cm -2 , lithium foil diameter 1 cm), 0.1 mL of ester LiPF6 electrolyte (marked as blank), 0.1 mL of modified electrolyte containing 15-crown ether-5 (marked as control 1), 0.1 mL of modified electrolyte containing alkyl chain 15-crown ether-5 (marked as control 2), and 0.1 mL of modified electrolyte containing fluorinated 15-crown ether-5 prepared in Example 2 (marked as fluorine-based additive) were loaded into four mold full batteries respectively; then the coulombic efficiency, cycle stability, capacity and retention rate of the four batteries were tested at a current density of 2C, and the results were as follows: Figure 2-3 shown.

[0058] according to Figure 2-3 It can be seen that at an ultra-high current density of 2C, the capacity of the lithium nickel manganese oxide / Li battery containing fluorinated 15-crown ether-5 modified electrolyte is significantly improved compared to the capacity of the lithium nickel manganese oxide / Li battery with blank ester LiPF6 electrolyte; the lithium nickel manganese oxide / Li battery with blank ester LiPF6 electrolyte shows a trend of decreasing capacity from the beginning of the cycle, and the capacity is only 27mAh / g after 800 cycles, while the lithium nickel manganese oxide / Li battery containing fluorinated 15-crown ether-5 modified electrolyte can stably cycle 800 cycles with the capacity basically unchanged. It can be seen that the cycle stability, capacity and retention rate of the lithium nickel manganese oxide / Li battery containing fluorinated 15-crown ether-5 modified electrolyte are significantly improved, indicating that the addition of fluorinated 15-crown ether-5 to the ester LiPF6 electrolyte can significantly improve the coulombic efficiency, cycle stability, capacity and retention rate of the battery, and is better than control 1 and control 2.

[0059] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A crown ether compound, characterized in that It has the chemical structure shown in formula (i): （i） 2. A rechargeable battery electrolyte, characterized in that: The invention is composed of a rechargeable battery electrolyte and an electrolyte additive, wherein the electrolyte additive is the crown ether compound according to claim 1.

3. The rechargeable battery electrolyte according to claim 2, characterized in that: The rechargeable battery electrolyte is one of ester electrolyte, ether electrolyte, nitrile electrolyte, sulfone electrolyte, aqueous electrolyte, mixed electrolyte and ionic liquid electrolyte.

4. The rechargeable battery electrolyte according to claim 2 or 3, characterized in that: The ratio of the mass of the electrolyte additive to the volume of the rechargeable battery electrolyte is 0.01-100g:1L.

5. A rechargeable battery, characterized in that: The rechargeable battery electrolyte according to any one of claims 2 to 4 is used.

6. The rechargeable battery according to claim 5, characterized in that: The rechargeable battery is one of a metal lithium / lithium ion battery, a metal sodium / sodium ion battery, a metal potassium / potassium ion battery, a metal magnesium / magnesium ion battery, a metal aluminum / aluminum ion battery, a metal zinc / zinc ion battery, and an iron battery.

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