Secondary battery electrolyte additive and method for preparing the same

Abstract

This invention provides an additive for secondary battery electrolytes and its preparation method. The additive is obtained by bonding the oxygen atoms of the four hydroxyl groups on the R1-R5 groups of the compound shown in structural formula I to groups A and B in any of the following ways: (1) bonding with two A groups; (2) bonding with two B groups; (3) bonding with one A group and one B group; wherein n is 0 or 1; R1-R5 are independently selected from H, C1-C5 alkoxy groups, hydroxyl groups, and hydroxyl-substituted C1-C5 alkyl groups, and R1-R5 contain at least four hydroxyl groups; * represents the bonding position. The additive of this invention can form a stable, cross-linked, and tough SEI film and further reduce battery impedance. The raw materials for the preparation of the additive are inexpensive and readily available, with low cost, short reaction route, simple purification process, and high production efficiency, and have broad application prospects in secondary battery electrolytes.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a secondary battery electrolyte additive and its preparation method. Background Technology

[0002] Secondary batteries possess advantages such as stable voltage, safety and reliability, low cost, wide applicability, abundant raw materials, and high recyclability. They are a crucial component in major applications such as next-generation information and communication, electric vehicles, energy storage power stations, and the energy internet. However, the electrolyte is a key factor restricting the development of secondary batteries. Electrolytes generally consist of carbonate solvents, electrolyte salts, and additives, and their properties significantly affect battery capacity, internal resistance, storage performance, and cycle life. The main development strategy for electrolytes is to utilize functional additives to form a stable protective film on the surfaces of the positive and negative electrodes, slowing down the chemical reaction between the electrode materials and the electrolyte, while simultaneously improving the permeability of metal ions to reduce the internal resistance of the secondary battery and extend its lifespan. Currently, the protective films formed by commercially available film-forming additives suffer from drawbacks such as uneven film thickness, poor high-temperature stability, and poor metal ion permeability, which can easily lead to increased battery impedance and reduced lifespan. Ethylene sulfate (DTD) and its derivatives, as a novel type of film-forming additive, have improved the performance of batteries in high-temperature cycling, storage, and low-temperature discharge, but they still cannot effectively address the problem of high battery impedance. Summary of the Invention

[0003] Based on this, the purpose of the present invention is to provide a secondary battery electrolyte additive that can form a stable, cross-linked, and tough SEI film and further reduce battery impedance.

[0004] To achieve the above objectives, the present invention adopts the following technical solution.

[0005] An additive for a secondary battery electrolyte, wherein the additive is obtained by bonding the oxygen atoms of the four hydroxyl groups on the R1-R5 groups of the compound shown in structural formula I to groups A and B in any of the following ways: (1) bonding with two A groups; (2) bonding with two B groups; (3) bonding with one A group and one B group.

[0006]

[0007] Wherein, n is 0 or 1; R1 to R5 are independently selected from H, alkoxy, hydroxyl, and hydroxyl-substituted alkyl groups of C1 to C5, and R1 to R5 contain at least 4 hydroxyl groups; * represents the bonding position.

[0008] In some embodiments, at least four of the groups R1 to R5 contain hydroxyl groups, and the additive is obtained by bonding the oxygen atoms of the hydroxyl groups on the four groups to groups A and B.

[0009] In some preferred embodiments, the additive is selected from compounds with the following structural formulas:

[0010]

[0011] In some embodiments, the secondary battery is a lithium metal battery, a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery.

[0012] The present invention also provides a method for preparing the additive as described above, comprising the following steps: (1) placing an ether-containing polyol, solvent 1 and an acid-binding agent in a reaction vessel, adding thionyl chloride dropwise to the vessel to carry out the reaction; filtering to remove byproducts, washing the filtrate with saturated brine, separating the liquid, drying the organic phase, filtering, and concentrating the filtrate under reduced pressure to obtain an additive containing only group B; (2) placing the additive containing only group B, solvent 2 and ruthenium trichloride in a reactor, adding an oxidant to the vessel to carry out the reaction, filtering to remove byproducts, washing the filtrate with saturated brine, separating the liquid, drying the organic phase, filtering, and concentrating the filtrate under reduced pressure to obtain an additive containing at least one group A.

[0013] In some embodiments, step (1) further includes washing, recrystallizing and drying the additive containing only group B; and / or, step (2) further includes washing, recrystallizing and drying the additive containing at least one group A.

[0014] Preferably, the washing solvent is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, acetonitrile, and water.

[0015] Preferably, the solvent for recrystallization is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, acetonitrile, methanol, ethanol, tetrahydrofuran, ethylene glycol dimethyl ether, petroleum ether, n-hexane, benzene, toluene, and xylene.

[0016] In some embodiments, in step (1), thionyl chloride is added dropwise at -20°C to 0°C for 6 to 12 hours.

[0017] In some embodiments, in step (2), an oxidant is added and reacted at -10°C to 10°C for 2 to 8 hours.

[0018] In some embodiments, the molar ratio of the acid-binding agent, thionyl chloride and ether-containing polyol in step (1) is (4.3-4.5):(2.1-2.2):1; and / or, the molar ratio of the additive containing only group B to the oxidant in step (2) is 1:(1-2.2).

[0019] In some embodiments, the decompression range of the decompression concentration in step (1) and / or step (2) is 10 Pa to 4000 Pa.

[0020] In some embodiments, the organic phase described in step (1) and / or step (2) is dried using at least one of anhydrous magnesium sulfate and anhydrous sodium sulfate.

[0021] In some embodiments, the ether-containing polyol is selected from any one of arabinose, xylose, methyl glucoside, 1,4-anhydromannitol, 2,5-anhydrosorbitol, 1,5-anhydromannitol, and their isomers; and / or,

[0022] Solvent 1 is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and / or,

[0023] The acid-binding agent is selected from at least one of triethylamine, pyridine, N,N-dimethylformamide, DBU, and DIPEA; and / or

[0024] The solvent 2 is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, acetonitrile, and water; and / or,

[0025] The oxidant is selected from at least one of sodium hypochlorite and sodium periodate.

[0026] This invention provides a novel electrolyte additive for secondary batteries. The additive can undergo an electrochemical reduction reaction at the electrode interface, allowing the sulfite or sulfate structures in the additive to gain electrons and form metal sulfite or metal sulfate substances, thus creating a conductive interface at the electrode interface. Simultaneously, the sulfite or sulfate units in the additive can each form free radical intermediates, which can further react with other sulfite or sulfate units to form a stable, cross-linked, and tough SEI film. In addition, the additive also contains ether bonds, which may have a lithium-conducting function similar to PEO, thereby reducing battery impedance.

[0027] The additives prepared by this invention use inexpensive and readily available raw materials, have low cost, short reaction routes, simple purification processes, and high production efficiency, and have broad application prospects in secondary battery electrolytes. Attached Figure Description

[0028] Figure 1 The NMR spectrum of compound 6 is shown in the form of hydrogen NMR.

[0029] Figure 2 This is the carbon NMR spectrum of compound 6.

[0030] Figure 3 This is the ultra-high performance liquid chromatogram of compound 6. Detailed Implementation

[0031] Unless otherwise specified, the experimental methods described in the following embodiments of the present invention are generally performed under conventional conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the embodiments are commercially available products.

[0032] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0033] The terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product, or device that includes a series of steps is not limited to the steps or modules listed, but may optionally include steps not listed, or may optionally include other steps inherent to such process, method, product, or device.

[0034] In this invention, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0035] The following description uses specific examples. The compound structure was determined by one-dimensional NMR spectroscopy, and the purity was determined by ultra-high performance liquid chromatography.

[0036] Example 1

[0037] Add 150 g of arabinose, 750 g of ethyl acetate, and 355.5 g of pyridine to a 2 L three-necked flask and cool in a -20 °C cold bath. After the system has cooled to the set temperature, slowly add 261.8 g of thionyl chloride dropwise and stir thoroughly for 12 h. After the reaction is complete, remove the byproduct hydrochloride by vacuum filtration. Wash the organic solution with 250 g of saturated brine three times. Dry the remaining organic phase with 75 g of anhydrous magnesium sulfate for 1 h. After vacuum filtration, evaporate the organic solution under reduced pressure to obtain 229.9 g of crude white solid of compound 1. Add 1150 g of dimethyl carbonate for recrystallization. After vacuum filtration and drying, obtain 206.9 g of purified white powder solid, yield 85.4%, purity 99.7%.

[0038] 206.9 g of purified compound 1, 1035 g of dimethyl carbonate, 406.3 g of sodium periodate, and 20.6 mL of 1 mg / L ruthenium trichloride aqueous solution were added to a 2 L three-necked flask and cooled in a 10 °C cold bath. After the system cooled to the set temperature, 206.9 g of pure water was slowly added dropwise, and the mixture was stirred thoroughly for 2 h. After the reaction was complete, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 345 g of saturated brine, and the separation was repeated three times. The remaining organic phase was dried with 100 g of anhydrous magnesium sulfate for 1 h, filtered under reduced pressure, and the organic solution was rotary evaporated under reduced pressure to obtain 222.6 g of crude compound 2. 445 g of ice water was added to wash the crude compound 2, and after filtration, 1110 g of acetonitrile was added for recrystallization. After filtration under reduced pressure and drying, 200.3 g of purified white powder compound 2 was obtained, with a yield of 85.5% and a purity of 99.6%.

[0039] Example 2

[0040] Add 150g xylose, 750g methyl ethyl carbonate, and 454.5g triethylamine to a 2L three-necked flask and cool in a -10℃ cold bath. After the system has cooled to the set temperature, slowly add 261.8g thionyl chloride dropwise and stir thoroughly for 12 hours. After the reaction is complete, remove the byproduct hydrochloride by vacuum filtration. Wash the organic solution with 250g saturated brine three times. Dry the remaining organic phase with 75g anhydrous magnesium sulfate for 1 hour. After vacuum filtration, evaporate the organic solution under reduced pressure to obtain 234.7g of crude white solid of compound 1. Add 1170g dimethyl carbonate to recrystallize the product, filter under reduced pressure, and dry to obtain 211.3g of purified white powder, with a yield of 87.3% and a purity of 99.1%.

[0041] 211.3 g of purified compound 1, 1060 g of dimethyl carbonate, and 21.1 mL of 1 mg / L ruthenium trichloride aqueous solution were added to a 3 L three-necked flask and cooled in a 5 °C cold bath. After the system cooled to the set temperature, 1421 g of sodium hypochlorite aqueous solution was slowly added dropwise, and the reaction was stirred thoroughly for 2 h. After the reaction was complete, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 350 g of saturated brine and the separation was repeated three times. The remaining organic phase was dried with 105 g of anhydrous magnesium sulfate for 1 h. After vacuum filtration, the organic solution was rotary evaporated under reduced pressure to obtain 220.1 g of crude compound 2. 440 g of ice water was added to wash the crude product, and after filtration, 1100 g of acetonitrile was added for recrystallization. After vacuum filtration and drying, 198.1 g of purified white powder compound 2 product was obtained, with a yield of 82.8% and a purity of 99.5%.

[0042] Example 3

[0043] 164 g of 1,4-dehydrated mannitol, 820 g of diethyl carbonate, and 684 g of DBU were added to a 2 L three-necked flask and cooled in a 0 °C cold bath. After the system cooled to the set temperature, 261.8 g of thionyl chloride was slowly added dropwise, and the reaction was stirred thoroughly for 12 h. After the reaction was complete, the byproduct hydrochloride was removed by vacuum filtration. The organic solution was washed with 270 g of saturated brine and separated, repeated three times. The remaining organic phase was dried with 80 g of anhydrous magnesium sulfate for 1 h, filtered under reduced pressure, and then evaporated under reduced pressure to obtain 243.2 g of a white solid crude product of compound 5. 1200 g of dimethyl carbonate was added to recrystallize the product, and after vacuum filtration and drying, 231.0 g of a purified white powder solid was obtained, with a yield of 90.3% and a purity of 99.7%.

[0044] 231.0 g of purified compound 5, 1150 g of methyl ethyl carbonate, 428.9 g of sodium periodate, and 23.1 mL of 1 mg / L ruthenium trichloride aqueous solution were added to a 2 L three-necked flask and cooled in a 0 °C cold bath. After the system cooled to the set temperature, 231.0 g of pure water was slowly added dropwise, and the mixture was stirred thoroughly for 2 h. After the reaction was complete, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 365 g of saturated brine, and the separation was repeated three times. The remaining organic phase was dried with 110 g of anhydrous magnesium sulfate for 1 h. After vacuum filtration, the organic solution was rotary evaporated under reduced pressure to obtain 246.9 g of crude compound 6. 445 g of ice water was added to wash the crude product, and after filtration, 1110 g of acetonitrile was added for recrystallization. After vacuum filtration and drying, 229.6 g of purified white powder compound 6 was obtained, with a yield of 88.4% and a purity of 99.6%.

[0045] Example 4

[0046] 164 g of 2,5-dehydrated mannitol, 820 g of ethyl acetate, and 328.5 g of DMF were added to a 2 L three-necked flask and cooled in a -20 °C cold bath. After the system cooled to the set temperature, 261.8 g of thionyl chloride was slowly added dropwise, and the reaction was stirred thoroughly for 12 h. After the reaction was complete, the byproduct hydrochloride was removed by vacuum filtration. The organic solution was washed with 270 g of saturated brine and separated, repeated three times. The remaining organic phase was dried with 80 g of anhydrous magnesium sulfate for 1 h, filtered under reduced pressure, and then evaporated under reduced pressure to obtain 243.2 g of crude white solid of compound 9. 1200 g of dimethyl carbonate was added to recrystallize the product, filtered under reduced pressure, and dried to obtain 218.9 g of purified white powder, with a yield of 85.5% and a purity of 99.4%.

[0047] 218.9 g of purified compound 9, 1100 g of dimethyl carbonate, and 21.9 mL of 1 mg / L ruthenium trichloride aqueous solution were added to a 2 L three-necked flask and cooled in a 10 °C cold bath. After the system cooled to the set temperature, 1343.5 g of sodium hypochlorite aqueous solution was slowly added dropwise, and the reaction was stirred thoroughly for 2 h. After the reaction was complete, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 365 g of saturated brine and the separation was repeated three times. The remaining organic phase was dried with 110 g of anhydrous magnesium sulfate for 1 h. After vacuum filtration, the organic solution was rotary evaporated under reduced pressure to obtain 229.0 g of crude compound 10. 435 g of ice water was added to wash the product, and after filtration, 1090 g of acetonitrile was added for recrystallization. After vacuum filtration and drying, 213.0 g of purified white powder compound 10 product was obtained, with a yield of 86.5% and a purity of 99.5%.

[0048] Example 5

[0049] 164 g of 1,5-dehydrated mannitol, 820 g of methyl ethyl carbonate, and 355.5 g of pyridine were added to a 2 L three-necked flask and cooled in a -10 °C cold bath. After the system cooled to the set temperature, 261.8 g of thionyl chloride was slowly added dropwise, and the reaction was stirred thoroughly for 12 h. After the reaction was complete, the byproduct hydrochloride was removed by vacuum filtration. The organic solution was washed with 270 g of saturated brine and separated, repeated three times. The remaining organic phase was dried with 80 g of anhydrous magnesium sulfate for 1 h, filtered under reduced pressure, and then evaporated under reduced pressure to obtain 240.6 g of crude white solid of compound 12. 1200 g of dimethyl carbonate was added to recrystallize the product, and after vacuum filtration and drying, 216.6 g of purified white powder was obtained, with a yield of 84.6% and a purity of 99.5%.

[0050] 216.6 g of purified compound 12, 1080 g of diethyl carbonate, 402.0 g of sodium periodate, and 21.7 mL of 1 mg / L ruthenium trichloride aqueous solution were added to a 2 L three-necked flask and cooled in a 0 °C cold bath. After the system cooled to the set temperature, 216.6 g of pure water was slowly added dropwise, and the reaction was stirred thoroughly for 2 h. After the reaction was complete, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 360 g of saturated brine, and the separation was repeated three times. The remaining organic phase was dried with 110 g of anhydrous magnesium sulfate for 1 h. After vacuum filtration, the organic solution was rotary evaporated under reduced pressure to obtain 224.2 g of crude compound 13. 450 g of ice water was added to wash the product, and after filtration, 1120 g of acetonitrile was added for recrystallization. After vacuum filtration and drying, 208.5 g of purified white powder compound 13 was obtained, with a yield of 85.6% and a purity of 99.2%.

[0051] Example 6

[0052] 194 g of methyl glucoside, 970 g of ethyl acetate, and 580.5 g of DIPEA were added to a 2 L three-necked flask and cooled in a -20 °C cold bath. After the system cooled to the set temperature, 261.8 g of thionyl chloride was slowly added dropwise, and the reaction was stirred thoroughly for 12 h. After the reaction was complete, the byproduct hydrochloride was removed by vacuum filtration. The organic solution was washed with 330 g of saturated brine and separated, repeated three times. The remaining organic phase was dried with 100 g of anhydrous magnesium sulfate for 1 h, filtered under reduced pressure, and then evaporated under reduced pressure to obtain 257.4 g of crude white solid of compound 16. 1300 g of dimethyl carbonate was added to recrystallize the product, and the mixture was filtered under reduced pressure and dried to obtain 231.7 g of purified white powder, with a yield of 81.0% and a purity of 99.5%.

[0053] 231.7 g of purified compound 16, 1160 g of methyl ethyl carbonate, 346.2 g of sodium periodate, and 23.2 mL of 1 mg / L ruthenium trichloride aqueous solution were added to a 2 L three-necked flask and cooled in a 0 °C cold bath. After the system cooled to the set temperature, 231.7 g of pure water was slowly added dropwise, and the reaction was stirred thoroughly for 2 h. After the reaction was complete, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 385 g of saturated brine, and the separation was repeated three times. The remaining organic phase was dried with 115 g of anhydrous magnesium sulfate for 1 h. After vacuum filtration, the organic solution was rotary evaporated under reduced pressure to obtain 244.7 g of crude compound 17. 500 g of ice water was added to wash the product, and after filtration, 1250 g of acetonitrile was added for recrystallization. After vacuum filtration and drying, 227.6 g of purified white powder compound 17 product was obtained, with a yield of 88.4% and a purity of 99.2%.

[0054] Example 7

[0055] 164 g of 2,5-dehydrated mannitol, 820 g of ethyl acetate, and 328.5 g of DMF were added to a 2 L three-necked flask and cooled in a -20 °C cold bath. After the system cooled to the set temperature, 261.8 g of thionyl chloride was slowly added dropwise, and the reaction was stirred thoroughly for 12 h. After the reaction was complete, the byproduct hydrochloride was removed by vacuum filtration. The organic solution was washed with 270 g of saturated brine and separated, repeated three times. The remaining organic phase was dried with 80 g of anhydrous magnesium sulfate for 1 h, filtered under reduced pressure, and then evaporated under reduced pressure to obtain 243.2 g of crude white solid of compound 9. 1200 g of dimethyl carbonate was added to recrystallize the product, filtered under reduced pressure, and dried to obtain 218.9 g of purified white powder, with a yield of 85.5% and a purity of 99.4%.

[0056] 218.9 g of purified compound 9, 1100 g of dimethyl carbonate, and 21.9 mL of 1 mg / L ruthenium trichloride aqueous solution were added to a 2 L three-necked flask and cooled in a 5 °C cold bath. After the system cooled to the set temperature, 671.8 g of sodium hypochlorite aqueous solution was slowly added dropwise, and the reaction was stirred thoroughly for 2 h. After the reaction was complete, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 365 g of saturated brine three times. The remaining organic phase was dried with 110 g of anhydrous magnesium sulfate for 1 h. After vacuum filtration, the organic solution was rotary evaporated under reduced pressure to obtain a mixture of compounds 10 and 11, weighing 209.3 g. 435 g of ice water was added to the mixture for washing, followed by filtration and recrystallization with 500 g of acetonitrile. After vacuum filtration and drying, 194.1 g of purified white lumpy compound 11 was obtained, with a yield of 81.1% and a purity of 97.2%.

[0057] Taking the structure and purity test results of compound 6 as an example: Figure 1 The one-dimensional hydrogen NMR spectrum of compound 6, the product synthesized in Example 3 of this invention; Figure 2 The one-dimensional carbon NMR spectrum of compound 6, the product synthesized in Example 3 of this invention; Figure 3 The image shows the ultra-high performance liquid chromatogram of compound 6, the synthesized product of Example 3 of this invention. The retention time of 3.263 min indicates the target product, and the unlabeled peaks are system solvent peaks. The purity calculation formula is: (peak area of ​​target product / sum of peak areas of all substances in the system) * 100%.

[0058] The non-aqueous electrolyte containing the compound obtained in the above embodiments as an additive was used to prepare a lithium-ion battery, and a non-aqueous electrolyte containing DTD as an additive was used as a control group. The lithium-ion battery was prepared by the following method:

[0059] 1) Preparation of non-aqueous electrolyte:

[0060] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC = 1:1:1. Then, lithium hexafluorophosphate (LiPF6) was added to a molar concentration of 1 mol / L. Additives were added based on the total weight of the non-aqueous electrolyte as 100%. The types and contents of each additive are shown in Table 1.

[0061] 2) Preparation of the positive electrode:

[0062] The positive electrode active material, lithium nickel cobalt manganese oxide (LiNiO), was mixed in a mass ratio of 93:4:3. 0.5 Co 0.2 Mn 0.3O2, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) are mixed and dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry is uniformly coated on both sides of an aluminum foil, dried, calendered, and vacuum dried, and then aluminum leads are welded on using an ultrasonic welder to obtain a positive electrode sheet with a thickness between 120-150 μm.

[0063] 3) Preparation of the negative electrode:

[0064] Artificial graphite, conductive carbon black Super-P, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 94:1:2.5:2.5 and then dispersed in deionized water to obtain a negative electrode slurry. The slurry was coated on both sides of a copper foil, dried, calendered, and vacuum dried, and then nickel leads were welded on using an ultrasonic welder to obtain a negative electrode plate with a thickness between 120-150 μm.

[0065] 4) Cell fabrication:

[0066] A three-layer separator with a thickness of 20 μm is placed between the positive and negative plates. Then, the sandwich structure composed of the positive plate, negative plate and separator is wound up. The wound body is flattened and placed in an aluminum foil packaging bag. It is then vacuum baked at 75°C for 48 hours to obtain the cell to be injected with electrolyte.

[0067] 5) Electrolyte injection and formation of the battery cell:

[0068] In a glove box where the dew point is controlled below -40°C, the electrolyte prepared above is injected into the battery cell, vacuum sealed, and left to stand for 24 hours.

[0069] The initial formation was then performed as follows: constant current charging at 0.05C for 180 minutes, constant current charging at 0.2C to 3.95V, followed by a second vacuum sealing. Then, it was further charged at a constant current of 0.2C to 4.2V, left to stand at room temperature for 24 hours, and finally discharged at a constant current of 0.2C to 3.0V to obtain a LiNi alloy. 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery.

[0070] The relevant performance of the prepared lithium-ion batteries was tested:

[0071] High-temperature cycling performance test

[0072] The formed lithium-ion battery was charged at 45°C with a constant current of 1C to 4.2V, then charged with a constant current and constant voltage until the current dropped to 0.05C. Finally, it was discharged with a constant current of 1C to 3.0V. The initial impedance of the battery was measured during the first cycle. This charge-discharge cycle was repeated 1000 times. The calculation formula is as follows:

[0073] Internal resistance growth rate (%) = (impedance in week 1000 - initial impedance in week 1) / initial impedance in week 1 × 100%.

[0074] The test results are shown in Table 1:

[0075] Table 1. Electrolyte composition and impedance increase rate test results

[0076]

[0077] The above results demonstrate that the additive of the present invention significantly reduces impedance compared to DTD. This is likely because the additive contains ether bonds, giving it a lithium-conducting function similar to that of polymer PEO, thereby reducing battery impedance.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A secondary battery electrolyte additive, characterized in that, The additive is compound 5, compound 6, compound 7 or compound 8 obtained by bonding the oxygen atoms of the four hydroxyl groups on the R1~R5 groups in the compound shown in structural formula I with groups A and B through any one of the following three methods: (1) bonding with two A groups; (2) bonding with two B groups; (3) bonding with one A group and one B group. Structural Formula I A B Wherein, n is 0 or 1; R1~R5 are independently selected from H, C1~C5 alkoxy, hydroxyl, and hydroxyl-substituted C1~C5 alkyl groups, and R1~R5 contain at least 4 hydroxyl groups; * represents the bonding position; Compound 5 Compound 6 Compound 7 Compound 8.

2. The additive as described in claim 1, characterized in that, At least four groups in R1 to R5 contain hydroxyl groups, and the additive is obtained by bonding the oxygen atoms of the hydroxyl groups on the four groups to groups A and B.

3. The additive according to any one of claims 1-2, characterized in that, The secondary battery is a lithium metal battery, a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery.

4. The method for preparing the additive according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Place the ether-containing polyol, solvent 1 and acid-binding agent in a reaction vessel, add thionyl chloride dropwise to the vessel to carry out the reaction; filter, remove by-products, wash the filtrate with saturated brine, separate the liquid, dry the organic phase, filter, concentrate the filtrate under reduced pressure to obtain an additive containing only group B. (2) The additive containing only group B, solvent 2 and ruthenium trichloride are placed in a reactor, an oxidant is added to the container to react, by-products are removed by filtration, the filtrate is washed with saturated brine, separated, the organic phase is dried and filtered, and the filtrate is concentrated under reduced pressure to obtain an additive containing at least one group A.

5. The preparation method according to claim 4, characterized in that, In step (1), thionyl chloride is added dropwise at -20℃ to 0℃ for 6 h to 12 h.

6. The preparation method according to claim 4, characterized in that, In step (2), an oxidant is added at -10℃ to 10℃ and reacted for 2 h to 8 h.

7. The preparation method according to claim 4, characterized in that, The molar ratio of the acid-binding agent, thionyl chloride, and ether-containing polyol in step (1) is (4.3~4.5):(2.1~2.2):1; and / or, The molar ratio of the additive containing only group B to the oxidant in step (2) is 1: (1~2.2).

8. The preparation method according to claim 4, characterized in that, The organic phase described in step (1) and / or step (2) is dried using at least one of anhydrous magnesium sulfate and anhydrous sodium sulfate.

9. The preparation method according to any one of claims 4-8, characterized in that, The ether-containing polyol is selected from any one of arabinose, xylose, methyl glucoside, 1,4-anhydromannitol, 2,5-anhydrosorbitol, 1,5-anhydromannitol, and their isomers; and / or, Solvent 1 is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and / or, The acid-binding agent is selected from at least one of triethylamine, pyridine, N,N-dimethylformamide, DBU, and DIPEA; and / or The solvent 2 is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, acetonitrile, and water; and / or, The oxidant is selected from at least one of sodium hypochlorite and sodium periodate.

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