Secondary battery electrolyte additive and preparation method therefor

Abstract

A secondary battery electrolyte additive and a preparation method therefor. The additive is obtained by bonding oxygen atoms of four hydroxyl groups on groups R1-R5 in a compound as represented by structural formula I to groups A and B in any one of the following manners: (1) bonding to two A groups; (2) bonding to two B groups; and (3) bonding to one A group and one B group. wherein, n is 0 or 1; R1-R5 are independently selected from H, a C1-C5 alkoxy group, a hydroxyl group, and a hydroxyl-substituted C1-C5 alkyl group, and R1-R5 contain at least four hydroxyl groups; and * represents a bonding position.

Description

Secondary battery electrolyte additive and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on the Chinese patent application with application number 202310773861.2 and application date of June 28, 2023, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference. Technical Field

[0003] The present disclosure belongs to the technical field of secondary batteries, and particularly relates to a secondary battery electrolyte additive and a preparation method thereof. Background Art

[0004] Secondary batteries, with their advantages of stable voltage, safety and reliability, low cost, wide applicability, abundant raw materials, and high recycling rates, are a key component in major applications such as next-generation information and communications, electric vehicles, energy storage power stations, and the energy internet. However, electrolytes are a key factor restricting the development of secondary batteries. Electrolytes are generally composed of carbonate solvents, electrolyte salts, and additives, and their properties significantly influence the battery's capacity, internal resistance, storage performance, and cycle life. A major development strategy for electrolytes is to utilize functional additives to form a stable protective film on the surfaces of the battery's positive and negative electrodes, slowing the chemical reaction between the electrode materials and the electrolyte while increasing the permeability of metal ions, thereby reducing the internal resistance of the secondary battery and extending its service life. Currently, protective films formed with commercially available film-forming additives suffer from shortcomings such as uneven surface thickness, poor high-temperature stability, and poor metal ion permeability, which can easily lead to adverse effects such as increased battery impedance and reduced battery life. As a new class of film-forming additives, diethyl sulfate (DTD) and its derivatives have the potential to improve battery performance during high-temperature cycling, storage, and low-temperature discharge, but they still cannot effectively address the problem of high battery impedance.

[0005] Summary of the Invention

[0006] Based on this, the purpose of the present disclosure is to provide a secondary battery electrolyte additive and a preparation method thereof, wherein the additive can form a stable, cross-linked, tough SEI film and further reduce the battery impedance.

[0007] In order to achieve the above objectives, the present disclosure adopts the following technical solutions.

[0008] A secondary battery electrolyte additive, wherein the additive is formed by bonding the oxygen atoms of the four hydroxyl groups on the R1 to R5 groups in the compound represented by structural formula I to the groups A and B in any of the following ways: (1) bonding to two A groups; (2) bonding to two B groups; (3) bonding to one A group and one B group:

[0009] Wherein, n is 0 or 1; R1 to R5 are independently selected from H, C1 to C5 alkoxy, hydroxyl, and hydroxyl-substituted C1 to C5 alkyl, and R1 to R5 contain at least 4 hydroxyl groups; * represents the bonding position.

[0010] In some embodiments, at least four groups among R1 to R5 contain hydroxyl groups, and the additive is formed by bonding the oxygen atoms of the hydroxyl groups on the four groups with group A and group B.

[0011] Optionally, the additive is selected from at least one of the compounds represented by the following structural formula:

[0012] 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.

[0013] The present disclosure also provides a preparation method of the additive as described above, comprising the following steps: (1) placing an ether-containing polyol, a solvent 1, and an acid-binding agent in a reaction vessel, and dropwise adding thionyl chloride into the vessel to react; filtering to remove by-products, washing the filtrate with saturated brine, separating the liquids, drying the organic phase, filtering, and concentrating the filtrate under reduced pressure to obtain an additive containing only group B; and (2) placing the additive containing only group B, a solvent 2, and ruthenium trichloride in a reactor, adding an oxidant to the vessel to react, filtering to remove by-products, washing the filtrate with saturated brine, separating the liquids, drying the organic phase, filtering, and concentrating the filtrate under reduced pressure to obtain an additive containing at least one group A.

[0014] In some embodiments, step (1) further comprises washing, recrystallizing and drying the additive containing only group B; and / or, step (2) further comprises washing, recrystallizing and drying the additive containing at least one group A.

[0015] Optionally, the washing solvent is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile and water.

[0016] Optionally, the recrystallization solvent is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, methanol, ethanol, tetrahydrofuran, ethylene glycol dimethyl ether, petroleum ether, n-hexane, benzene, toluene, and xylene.

[0017] In some embodiments, in step (1), thionyl chloride is added dropwise at -20°C to 0°C for 6 hours to 12 hours.

[0018] In some embodiments, in step (2), an oxidant is added at -10°C to 10°C for 2h to 8h.

[0019] 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).

[0020] In some embodiments, the reduced pressure range of the reduced pressure concentration in step (1) and / or step (2) is 10Pa to 4000Pa.

[0021] In some embodiments, the organic phase in step (1) and / or step (2) is dried using at least one of anhydrous magnesium sulfate and anhydrous sodium sulfate.

[0022] 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 isomers thereof; and / or,

[0023] The solvent 1 is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; and / or,

[0024] The acid binding agent is selected from at least one of triethylamine, pyridine, N,N-dimethylformamide, DBU, and DIPEA; and / or

[0025] The solvent 2 is selected from at least one of ethyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile and water; and / or,

[0026] The oxidant is selected from at least one of sodium hypochlorite and sodium periodate.

[0027] The present disclosure provides a new secondary battery electrolyte additive, which can undergo an electrochemical reduction reaction at the electrode interface, so that the sulfite or sulfate structure in the additive can obtain electrons to form metal sulfite or metal sulfate substances, forming a conductive interface at the electrode interface; at the same time, the sulfite or sulfate units in the additive can each form a free radical intermediate, and further react with other sulfite or sulfate units to form a stable, cross-linked, 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.

[0028] The raw materials for preparing the additive disclosed in the present invention are cheap and readily available, the cost is low, the reaction route is short, the purification process is simple, the production efficiency is high, and the application prospect in secondary battery electrolyte is broad. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the H NMR spectrum of compound 6.

[0030] Figure 2 is the C NMR spectrum of compound 6.

[0031] FIG3 is an ultra-high performance liquid chromatogram of compound 6. DETAILED DESCRIPTION

[0032] The experimental methods in the following examples of this disclosure, where specific conditions are not specified, are generally carried out under conventional conditions or conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0033] Unless otherwise defined, all technical and scientific terms used in this disclosure have the same meaning as those commonly understood by those skilled in the art in the art. The terms used in the specification of this disclosure are only for the purpose of describing specific embodiments and are not intended to limit this disclosure.

[0034] The terms "including" and "having" and any variations thereof in this disclosure are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product, or device comprising a series of steps is not limited to the listed steps or modules, but may optionally include steps not listed, or may optionally include other steps inherent to the process, method, product, or device.

[0035] In this disclosure, "plurality" refers to two or more. "And / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0036] The following is an explanation with reference to specific examples, wherein the structure of the compound was confirmed by one-dimensional nuclear magnetic resonance spectroscopy, and the purity was confirmed by ultra-high performance liquid chromatography.

[0037] Example 1

[0038] Add 150g of arabinose, 750g of ethyl acetate, and 355.5g of pyridine to a 2L three-necked flask and cool in a -20°C cold bath. After the system is cooled to the set temperature, 261.8g of thionyl chloride is slowly added dropwise and the reaction is stirred for 12h. After the reaction is completed, the by-product hydrochloride is removed by filtration under reduced pressure, and the organic solution is washed with 250g of saturated brine and separated. This is repeated three times. The remaining organic phase is dried over 75g of anhydrous magnesium sulfate for 1h. After filtration under reduced pressure, the organic solution is evaporated under reduced pressure to obtain 229.9g of a crude white solid of compound 1. 1150g of dimethyl carbonate is added thereto for recrystallization, filtration under reduced pressure, and drying to obtain 206.9g of a refined white powdery solid with a yield of 85.4% and a purity of 99.7%.

[0039] To a 2L three-necked flask, 206.9g of refined compound 1, 1035g of dimethyl carbonate, 406.3g of sodium periodate, and 20.6mL of a 1mg / L ruthenium trichloride aqueous solution were added and cooled in a 10°C cold bath. After the system cooled to the set temperature, 206.9g of pure water was slowly added dropwise and the reaction was stirred for 2h. After the reaction was completed, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 345g of saturated brine three times. The remaining organic phase was dried over 100g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 222.6g of crude compound 2. 445g of ice water was added to the mixture for washing, filtered, and then 1110g of acetonitrile was added to the mixture for recrystallization. After reduced pressure filtering and drying, 200.3g of refined white powdered compound 2 was obtained, with a yield of 85.5% and a purity of 99.6%.

[0040] Example 2

[0041] To a 2L three-necked flask, 150g of xylose, 750g of ethyl methyl carbonate, and 454.5g of triethylamine were added and cooled in a -10°C cold bath. After the system was cooled to the set temperature, 261.8g of thionyl chloride was slowly added dropwise and the reaction was stirred for 12h. After the reaction was completed, the by-product hydrochloride was removed by filtration under reduced pressure, and the organic solution was washed with 250g of saturated brine and separated, and the reaction was repeated three times. The remaining organic phase was dried over 75g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 234.7g of a crude white solid of compound 1. 1170g of dimethyl carbonate was added thereto for recrystallization, filtered under reduced pressure, and dried to obtain 211.3g of a refined white powdery solid with a yield of 87.3% and a purity of 99.1%.

[0042] To a 3L three-necked flask, 211.3g of refined compound 1, 1060g of dimethyl carbonate, and 21.1mL of a 1mg / L ruthenium trichloride aqueous solution were added and cooled in a 5°C cold bath. After the system cooled to the set temperature, 1421g of sodium hypochlorite aqueous solution was slowly added dropwise and the reaction was stirred for 2h. After the reaction was completed, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 350g of saturated brine and the separation was repeated three times. The remaining organic phase was dried with 105g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 220.1g of crude compound 2. 440g of ice water was added for washing, filtered, and then 1100g of acetonitrile was added for recrystallization. After reduced pressure and filtration, the purified white powder compound 2 product 198.1g was obtained, with a yield of 82.8% and a purity of 99.5%.

[0043] Example 3

[0044] To a 2L three-necked flask, add 164g of 1,4-anhydromannitol, 820g of diethyl carbonate, and 684g of DBU. Cool the mixture in a 0°C cold bath. After the system cools to the set temperature, slowly add 261.8g of thionyl chloride dropwise and stir thoroughly for 12 hours. After completion of the reaction, remove the byproduct hydrochloride by-product by filtration under reduced pressure. The organic solution is washed with 270g of saturated brine three times. The remaining organic phase is dried over 80g of anhydrous magnesium sulfate for 1 hour, filtered under reduced pressure, and then rotary evaporated under reduced pressure to obtain 243.2g of crude compound 5 as a white solid. 1200g of dimethyl carbonate is added to the mixture for recrystallization. Filter under reduced pressure and dry to obtain 231.0g of a refined white powdery solid with a yield of 90.3% and a purity of 99.7%.

[0045] To a 2L three-necked flask, 231.0g of purified compound 5, 1150g of ethyl methyl carbonate, 428.9g of sodium periodate, and 23.1mL of a 1mg / L aqueous solution of ruthenium trichloride were added and cooled in a 0°C cold bath. After the system cooled to the set temperature, 231.0g of pure water was slowly added dropwise and the reaction was stirred thoroughly for 2h. After completion of the reaction, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 365g of saturated brine three times. The remaining organic phase was dried over 110g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 246.9g of crude compound 6. 445g of ice water was added to the mixture for washing, filtered, and then 1110g of acetonitrile was added to the mixture for recrystallization. After reduced pressure filtering and drying, 229.6g of the refined white powder compound 6 was obtained, with a yield of 88.4% and a purity of 99.6%.

[0046] Example 4

[0047] To a 2L three-necked flask, add 164g of 2,5-anhydromannitol, 820g of ethyl acetate, and 328.5g of DMF. Cool the mixture in a -20°C cold bath. After cooling to the set temperature, slowly add 261.8g of thionyl chloride dropwise and stir thoroughly for 12 hours. After completion of the reaction, remove the byproduct hydrochloride by-product by filtration under reduced pressure. The organic solution is washed with 270g of saturated brine three times. The remaining organic phase is dried over 80g of anhydrous magnesium sulfate for 1 hour, filtered under reduced pressure, and then rotary evaporated under reduced pressure to obtain 243.2g of crude compound 9 as a white solid. 1200g of dimethyl carbonate is added to the mixture for recrystallization. Filter under reduced pressure and dry to obtain 218.9g of a refined white powdery solid with a yield of 85.5% and a purity of 99.4%.

[0048] To a 2L three-necked flask, 218.9g of refined compound 9, 1100g of dimethyl carbonate, and 21.9mL of a 1mg / L ruthenium trichloride aqueous solution were added and cooled in a 10°C cold bath. After the system cooled to the set temperature, 1343.5g of sodium hypochlorite aqueous solution was slowly added dropwise and the reaction was stirred for 2h. After the reaction was completed, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 365g of saturated brine and the separation was repeated three times. The remaining organic phase was dried over 110g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 229.0g of a crude product of compound 10. 435g of ice water was added to the mixture for washing, filtered, and then 1090g of acetonitrile was added to the mixture for recrystallization. After reduced pressure filtering and drying, 213.0g of a refined white powder of compound 10 was obtained, with a yield of 86.5% and a purity of 99.5%.

[0049] Example 5

[0050] To a 2L three-necked flask, add 164g of 1,5-anhydromannitol, 820g of ethyl methyl carbonate, and 355.5g of pyridine and cool in a -10°C cold bath. After the system cools to the set temperature, slowly add 261.8g of thionyl chloride dropwise and stir thoroughly for 12 hours. After completion of the reaction, remove the byproduct hydrochloride by-product by filtration under reduced pressure. The organic solution is washed with 270g of saturated brine three times. The remaining organic phase is dried over 80g of anhydrous magnesium sulfate for 1 hour and filtered under reduced pressure. The organic solution is then rotary evaporated under reduced pressure to obtain 240.6g of crude compound 12 as a white solid. 1200g of dimethyl carbonate is added to the solution for recrystallization. Filter under reduced pressure and dry to obtain 216.6g of a refined white powdery solid with a yield of 84.6% and a purity of 99.5%.

[0051] To a 2L three-necked flask, 216.6g of purified compound 12, 1080g of diethyl carbonate, 402.0g of sodium periodate, and 21.7mL of a 1mg / L ruthenium trichloride aqueous solution were added and cooled in a 0°C cold bath. After the system cooled to the set temperature, 216.6g of pure water was slowly added dropwise and the reaction was stirred thoroughly for 2h. After the reaction was completed, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 360g of saturated brine three times. The remaining organic phase was dried over 110g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 224.2g of crude compound 13. 450g of ice water was added to the mixture for washing, filtered, and then 1120g of acetonitrile was added to the mixture for recrystallization. After reduced pressure filtering and drying, 208.5g of refined white powdered compound 13 product was obtained, with a yield of 85.6% and a purity of 99.2%.

[0052] Example 6

[0053] To a 2L three-necked flask, 194g of methyl glucoside, 970g of ethyl acetate, and 580.5g of DIPEA were added and cooled in a -20°C cold bath. After the system cooled to the set temperature, 261.8g of thionyl chloride was slowly added dropwise and the reaction was stirred for 12h. After the reaction was completed, the by-product hydrochloride was removed by filtration under reduced pressure, and the organic solution was washed with 330g of saturated brine and the separation was repeated three times. The remaining organic phase was dried over 100g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 257.4g of the crude product of compound 16 as a white solid. 1300g of dimethyl carbonate was added thereto for recrystallization, filtered under reduced pressure, and dried to obtain 231.7g of a refined white powdery solid with a yield of 81.0% and a purity of 99.5%.

[0054] To a 2L three-necked flask, 231.7g of purified compound 16, 1160g of ethyl methyl carbonate, 346.2g of sodium periodate, and 23.2mL of a 1mg / L aqueous solution of ruthenium trichloride were added and cooled in a 0°C cold bath. After the system cooled to the set temperature, 231.7g of pure water was slowly added dropwise and the reaction was stirred thoroughly for 2h. After completion of the reaction, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 385g of saturated brine three times. The remaining organic phase was dried over 115g of anhydrous magnesium sulfate for 1h, filtered under reduced pressure, and the organic solution was evaporated under reduced pressure to obtain 244.7g of crude compound 17. 500g of ice water was added to the mixture for washing, filtered, and then 1250g of acetonitrile was added to the mixture for recrystallization. After reduced pressure filtering and drying, 227.6g of the purified white powder compound 17 was obtained, with a yield of 88.4% and a purity of 99.2%.

[0055] Example 7

[0056] To a 2L three-necked flask, add 164g of 2,5-anhydromannitol, 820g of ethyl acetate, and 328.5g of DMF. Cool the mixture in a -20°C cold bath. After cooling to the set temperature, slowly add 261.8g of thionyl chloride dropwise and stir thoroughly for 12 hours. After completion of the reaction, remove the byproduct hydrochloride by-product by filtration under reduced pressure. The organic solution is washed with 270g of saturated brine three times. The remaining organic phase is dried over 80g of anhydrous magnesium sulfate for 1 hour, filtered under reduced pressure, and then rotary evaporated under reduced pressure to obtain 243.2g of crude compound 9 as a white solid. 1200g of dimethyl carbonate is added to the mixture for recrystallization. Filter under reduced pressure and dry to obtain 218.9g of a refined white powdery solid with a yield of 85.5% and a purity of 99.4%.

[0057] To a 2L three-necked flask, 218.9g of refined compound 9, 1100g of dimethyl carbonate, and 21.9mL of a 1mg / L ruthenium chloride aqueous solution were added and placed in a 5°C cold bath for cooling. After the system cooled to the set temperature, 671.8g of sodium hypochlorite aqueous solution was slowly added dropwise and the reaction was stirred for 2h. After completion of the reaction, the mixture was transferred to a separatory funnel and allowed to stand for separation. The organic phase was washed with 365g of saturated brine and the separation was repeated three times. The remaining organic phase was dried with 110g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution was vacuum evaporated to obtain 209.3g of a mixture of compounds 10 and 11. 435g of ice water was added for washing, and after suction filtration, 500g of acetonitrile was added thereto for recrystallization. After vacuum filtration and drying, 194.1g of the refined white block compound 11 product was obtained, with a yield of 81.1% and a purity of 97.2%.

[0058] Taking the structure and purity test results of Compound 6 as an example: Figure 1 shows the one-dimensional H-NMR spectrum of Compound 6, the product synthesized in Example 3 of the present disclosure; Figure 2 shows the one-dimensional C-NMR spectrum of Compound 6, the product synthesized in Example 3 of the present disclosure; Figure 3 shows the ultra-high performance liquid chromatogram of Compound 6, the product synthesized in Example 3 of the present disclosure. The peak with a retention time of 3.263 min is the target product, and the unlabeled peak is the system solvent peak. The purity calculation formula is: target product peak area / sum of the peak areas of all substances in the system * 100%.

[0059] The non-aqueous electrolyte solution containing the compound prepared in the above example as an additive was used to prepare a lithium-ion battery, and a non-aqueous electrolyte solution containing DTD as an additive was used as a control group. The lithium-ion battery was prepared by the following method:

[0060] 1) Preparation of non-aqueous electrolyte:

[0061] Ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC=1:1:1, and 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 the additives are shown in Table 1.

[0062] 2) Preparation of positive electrode sheet:

[0063] The positive electrode active material lithium nickel cobalt manganese oxide LiNi was mixed in a mass ratio of 93:4:3 0.5 Co 0.2 Mn 0.3O2, conductive carbon black Super-P, and a binder called polyvinylidene fluoride (PVDF) are then dispersed in N-methyl-2-pyrrolidone (NMP) to create a positive electrode slurry. The slurry is evenly coated on both sides of aluminum foil, dried, rolled, and vacuum-dried, and then ultrasonically welded with aluminum lead wires to create a positive electrode sheet with a thickness of between 120 and 150 μm.

[0064] 3) Preparation of negative electrode sheet:

[0065] The negative electrode active material, artificial graphite, conductive carbon black Super-P, and binders styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC), are mixed in a mass ratio of 94:1:2.5:2.5 and dispersed in deionized water to create a negative electrode slurry. The slurry is then coated on both sides of a copper foil, dried, rolled, and vacuum-dried. Nickel lead wires are then ultrasonically welded to create the negative electrode plate, which is between 120 and 150 μm thick.

[0066] 4) Preparation of battery cells:

[0067] A three-layer separator with a thickness of 20 μm was placed between the positive plate and the negative plate, and then the sandwich structure consisting of the positive electrode sheet, negative electrode sheet and separator was wound. The wound body was flattened and placed in an aluminum foil packaging bag, and vacuum-baked at 75°C for 48 hours to obtain a battery cell ready for liquid injection.

[0068] 5) Injection and formation of battery cells:

[0069] In a glove box with a dew point controlled below -40°C, the prepared electrolyte was injected into the battery cell, vacuum-sealed, and left to stand for 24 hours.

[0070] Then, the conventional formation of the first charge was carried out according to the following steps: 0.05C constant current charging for 180min, 0.2C constant current charging to 3.95V, secondary vacuum sealing, and then further 0.2C constant current charging to 4.2V, after being placed at room temperature for 24h, and then 0.2C constant current discharge to 3.0V, a LiNi 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery.

[0071] The relevant performance of the prepared lithium-ion battery was tested:

[0072] High temperature cycle performance test

[0073] The formed lithium-ion battery was charged at 45°C at a constant current of 1C to 4.2V, then charged at constant current and constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 1C to 3.0V. The initial impedance of the battery was measured in the first week. This method was used for 1000 cycles of charge and discharge. The calculation formula is as follows:

[0074] Internal resistance growth rate (%) = (1000th week impedance - first week initial impedance) / first week initial impedance × 100%.

[0075] The test results are shown in Table 1:

[0076] Table 1 Electrolyte composition and impedance increase rate test results

[0077] The above results show that the additive disclosed herein has a significant impedance reduction function compared to DTD. This may be because the additive disclosed herein contains ether bonds, which give it a lithium-conducting function similar to polymer PEO, thereby having the effect of reducing battery impedance.

[0078] The technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, 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 above-described embodiments merely represent several implementation methods of the present disclosure. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the scope of the present disclosure, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A secondary battery electrolyte additive, wherein the additive is obtained by bonding the oxygen atoms of the four hydroxyl groups on the R1 to R5 groups in the compound represented by structural formula I to the group A and the group B in any of the following ways: (1) bonding to two A groups; (2) bonding to two B groups; (3) bonding to one A group and one B group: in, n is 0 or 1; R1-R5 are independently selected from H, C1-C5 alkoxy, hydroxyl, and C1-C5 alkyl substituted with hydroxyl, and R1-R5 contain at least 4 hydroxyl groups; * represents the bonding position.

2. The additive according to claim 1, wherein At least four groups among R1 to R5 contain hydroxyl groups, and the additive is obtained by bonding the oxygen atoms of the hydroxyl groups on the four groups with group A and group B.

3. The additive according to claim 1 or 2, wherein The additive is selected from at least one of the compounds shown in the following structural formula:

4. The additive according to any one of claims 1 to 3, wherein 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.

5. The method for preparing the additive according to any one of claims 1 to 4, comprising the following steps: (1) placing an ether-containing polyol, a solvent 1 and an acid-binding agent in a reaction container, and dropwise adding thionyl chloride into the container to react; filtering to remove by-products, washing the filtrate with saturated brine, separating the liquids, drying the organic phase, filtering with suction, 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 container for reaction, filtering to remove by-products, washing the filtrate with saturated brine, separating the liquids, drying the organic phase, filtering with suction, and concentrating the filtrate under reduced pressure to obtain an additive containing at least one group A.

6. The preparation method according to claim 5, wherein In step (1), thionyl chloride is added dropwise at -20°C to 0°C and reacted for 6h to 12h.

7. The preparation method according to claim 5 or 6, wherein: In step (2), an oxidant is added at -10°C to 10°C and the reaction is carried out for 2h to 8h.

8. The preparation method according to any one of claims 5 to 7, wherein: 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).

9. The preparation method according to any one of claims 5 to 8, wherein: The organic phase in step (1) and / or step (2) is dried using at least one of anhydrous magnesium sulfate and anhydrous sodium sulfate.

10. The preparation method according to any one of claims 5 to 9, wherein: The ether-containing polyol is selected from any one of arabinose, xylose, methyl glucoside, 1,4-anhydromannitol, 2,5-anhydrosorbitol, 1,5-anhydromannitol and isomers thereof; and / or, The 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, ethyl methyl carbonate, acetonitrile and water; and / or, The oxidant is selected from at least one of sodium hypochlorite and sodium periodate.

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