Secondary battery electrolyte additive and preparation method thereof

Abstract

The invention provides a secondary battery electrolyte additive and a preparation method thereof. The additive is obtained by bonding oxygen atoms of four hydroxyl groups on R1-R5 groups in a compound as shown in a structural formula I with a group A and a group B through any one of the following modes: (1) bonding with two groups A; (2) bonding with two B groups; (3) bonding with one A group and one B group: # imgabs0 # wherein n is 0 or 1; r1 to R5 are independently selected from H, alkoxy of C1 to C5, hydroxyl and alkyl of C1 to C5 substituted by hydroxyl, and at least four hydroxyl are contained in R1 to R5; * represents a bonding position. The additive can form a stable, cross-linked and tough SEI film, and battery impedance is further reduced. The additive is cheap and easily available in preparation raw materials, low in cost, short in reaction route, simple in purification process, high in production efficiency and wide in application prospect in the secondary battery electrolyte.

Description

Technical Field

[0001] The invention belongs to the technical field of secondary batteries, and in particular relates to a secondary battery electrolyte additive and a preparation method thereof. Background Art

[0002] Secondary batteries have the advantages of stable voltage, safety and reliability, low price, wide application range, rich raw materials and high recycling rate. They are the key link of major applications such as new generation information communication, electric vehicles, energy storage power stations and energy Internet, and electrolyte is the key factor restricting the development of secondary batteries. Electrolyte is generally composed of carbonate solvents, electrolyte salts and additives, and its properties have a significant impact on the capacity, internal resistance, storage performance and cycle life of the battery. The main development strategy of electrolyte is to use functional additives to form a stable protective film on the surface of the positive and negative electrodes of the battery, slow down the chemical reaction between the electrode materials and the electrolyte, and improve the permeability of metal ions to reduce the internal resistance of the secondary battery and extend the service life of the battery. The protective film formed by the participation of commercial film-forming additives currently has the disadvantages of uneven film surface thickness, poor high temperature stability, and poor metal ion permeability, which can easily cause adverse effects such as increased battery impedance and reduced life. As a new type of film-forming additive, vinyl sulfate (DTD) and its derivative additives have the performance of improving high temperature cycling, storage and low temperature discharge of batteries, but they still cannot effectively improve the problem of high battery impedance. Summary of the invention

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

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

[0005] A secondary battery electrolyte additive, the additive is obtained by bonding the oxygen atoms of 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:

[0006]

[0007] Wherein, 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.

[0008] In some embodiments, 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.

[0009] In some preferred embodiments, the additive is selected from the compounds represented by the following structural formula:

[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 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 container, and dripping 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, 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 container 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.

[0013] 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.

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

[0015] Preferably, 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.

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

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

[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 reduced pressure range of the reduced pressure concentration in step (1) and / or step (2) is 10Pa to 4000Pa.

[0020] 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.

[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 isomers thereof; and / or,

[0022] The 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, ethyl methyl carbonate, acetonitrile and water; and / or,

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

[0026] The present invention provides a new electrolyte additive for secondary batteries. The additive can undergo an electrochemical reduction reaction at an electrode interface, so that a sulfite or sulfate structure in the additive can obtain electrons to form a metal sulfite or metal sulfate substance, thereby forming a conductive interface at the electrode interface. Meanwhile, the sulfite or sulfate units in the additive can form free radical intermediates respectively, and further react with other sulfite or sulfate units to form a stable, cross-linked, tough SEI film. In addition, the additive also contains an ether bond, which may have a lithium-conducting function similar to that of PEO, thereby reducing battery impedance.

[0027] The additive of the invention has cheap and readily available raw materials for preparation, low cost, short reaction route, simple purification process, high production efficiency, and broad application prospect in secondary battery electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the H NMR spectrum of compound 6.

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

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

[0031] The experimental methods in the following examples of the present invention, where no specific conditions are specified, are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0032] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] The terms "including" and "having" and any variations thereof of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment 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 these processes, methods, products or equipment.

[0034] In the present invention, the term "multiple" refers to two or more than two. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0035] The following is an explanation with reference to specific examples, wherein the structure of the compound is determined by one-dimensional nuclear magnetic resonance spectroscopy, and the purity is determined by ultra-high performance liquid chromatography.

[0036] Example 1

[0037] Add 150g of arabinose, 750g of ethyl acetate, and 355.5g of pyridine to a 2L three-necked flask and place it in a -20°C cold bath to cool. After the system is cooled to the set temperature, slowly add 261.8g of thionyl chloride and stir the reaction for 12h. After the reaction is completed, remove the by-product hydrochloride by vacuum filtration, wash the organic solution with 250g of saturated brine, repeat three times, and dry the remaining organic phase with 75g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 229.9g of the crude product of compound 1 as a white solid. Add 1150g of dimethyl carbonate to it for recrystallization, vacuum filtration, and drying to obtain 206.9g of refined white powdery solid, with a yield of 85.4% and a purity of 99.7%.

[0038] Add 206.9g of refined compound 1, 1035g of dimethyl carbonate, 406.3g of sodium periodate, and 20.6mL of 1mg / L ruthenium trichloride aqueous solution to a 2L three-necked flask, and place it in a 10°C cold bath to cool. After the system is cooled to the set temperature, slowly add 206.9g of pure water and stir the reaction for 2h. After the reaction is completed, transfer it to a separatory funnel and let it stand for separation. Take the organic phase and wash the separation with 345g of saturated salt water, repeat three times, and dry the remaining organic phase with 100g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 222.6g of crude compound 2. Add 445g of ice water to wash, filter and then add 1110g of acetonitrile to recrystallize, filter and dry under reduced pressure to obtain 200.3g of refined white powder compound 2 product, with a yield of 85.5% and a purity of 99.6%.

[0039] Example 2

[0040] Add 150g of xylose, 750g of ethyl methyl carbonate, and 454.5g of triethylamine to a 2L three-necked flask and place it in a -10°C cold bath to cool. After the system is cooled to the set temperature, slowly add 261.8g of thionyl chloride and stir the reaction for 12h. After the reaction is completed, remove the by-product hydrochloride by vacuum filtration, wash the organic solution with 250g of saturated brine, repeat three times, and dry the remaining organic phase with 75g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 234.7g of the crude product of compound 1 as a white solid. Add 1170g of dimethyl carbonate to it for recrystallization, vacuum filtration, and drying to obtain 211.3g of refined white powdery solid, with a yield of 87.3% and a purity of 99.1%.

[0041] Add 211.3g of refined compound 1, 1060g of dimethyl carbonate, 21.1mL of 1mg / L ruthenium trichloride aqueous solution to a 3L three-necked flask and place it in a 5°C cold bath for cooling. After the system is cooled to the set temperature, slowly add 1421g of sodium hypochlorite aqueous solution and stir the reaction for 2h. After the reaction is completed, transfer to a separatory funnel and let stand for separation. Take the organic phase and wash the separation with 350g of saturated brine, repeat three times, and dry the remaining organic phase with 105g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 220.1g of crude compound 2. Add 440g of ice water to wash, filter and then add 1100g of acetonitrile to recrystallize, filter and dry under reduced pressure to obtain 198.1g of refined white powder compound 2 product, with a yield of 82.8% and a purity of 99.5%.

[0042] Example 3

[0043] Add 164g of 1,4-dehydrated mannitol, 820g of diethyl carbonate, and 684g of DBU to a 2L three-necked flask and place it in a 0°C cold bath to cool. After the system is cooled to the set temperature, slowly add 261.8g of thionyl chloride and stir the reaction for 12h. After the reaction is completed, remove the by-product hydrochloride by vacuum filtration, wash the organic solution with 270g of saturated brine, repeat three times, and dry the remaining organic phase with 80g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 243.2g of the crude product of compound 5 as a white solid. Add 1200g of dimethyl carbonate to it for recrystallization, vacuum filtration, and drying to obtain 231.0g of refined white powder solid, with a yield of 90.3% and a purity of 99.7%.

[0044] Add 231.0g of refined compound 5, 1150g of ethyl methyl carbonate, 428.9g of sodium periodate, and 23.1mL of 1mg / L ruthenium trichloride aqueous solution to a 2L three-necked flask and place it in a 0°C cold bath for cooling. After the system is cooled to the set temperature, slowly add 231.0g of pure water and stir the reaction for 2h. After the reaction is completed, transfer it to a separatory funnel and let it stand for separation. Take the organic phase and wash the separation with 365g of saturated brine, repeat three times, and dry the remaining organic phase with 110g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 246.9g of crude compound 6. Add 445g of ice water to wash, filter and then add 1110g of acetonitrile to recrystallize, filter and dry under reduced pressure to obtain 229.6g of refined white powder compound 6 product, with a yield of 88.4% and a purity of 99.6%.

[0045] Example 4

[0046] Add 164g of 2,5-dehydrated mannitol, 820g of ethyl acetate, and 328.5g of DMF to a 2L three-necked flask and place it in a -20°C cold bath to cool. After the system is cooled to the set temperature, slowly add 261.8g of thionyl chloride and stir the reaction for 12h. After the reaction is completed, remove the by-product hydrochloride by vacuum filtration, wash the organic solution with 270g of saturated brine, repeat three times, and dry the remaining organic phase with 80g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 243.2g of the crude product of compound 9 as a white solid. Add 1200g of dimethyl carbonate to it for recrystallization, vacuum filtration, and drying to obtain 218.9g of refined white powdery solid, with a yield of 85.5% and a purity of 99.4%.

[0047] Add 218.9g of refined compound 9, 1100g of dimethyl carbonate, 21.9mL of 1mg / L ruthenium trichloride aqueous solution to a 2L three-necked flask, and place it in a 10°C cold bath to cool. After the system is cooled to the set temperature, slowly add 1343.5g of sodium hypochlorite aqueous solution, and stir the reaction for 2h. After the reaction is completed, transfer it to a separatory funnel and let it stand for separation. Take the organic phase and wash the separation with 365g of saturated salt water, repeat three times, and dry the remaining organic phase with 110g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 229.0g of crude product of compound 10. Add 435g of ice water to wash, filter and then add 1090g of acetonitrile to recrystallize, filter and dry under reduced pressure to obtain 213.0g of refined white powder compound 10 product, with a yield of 86.5% and a purity of 99.5%.

[0048] Example 5

[0049] Add 164g of 1,5-dehydrated mannitol, 820g of ethyl methyl carbonate, and 355.5g of pyridine to a 2L three-necked flask and place it in a -10°C cold bath to cool. After the system is cooled to the set temperature, slowly add 261.8g of thionyl chloride and stir the reaction for 12h. After the reaction is completed, remove the by-product hydrochloride by vacuum filtration, wash the organic solution with 270g of saturated brine, repeat three times, and dry the remaining organic phase with 80g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 240.6g of the crude product of compound 12 as a white solid. Add 1200g of dimethyl carbonate to it for recrystallization, vacuum filtration, and drying to obtain 216.6g of refined white powdery solid, with a yield of 84.6% and a purity of 99.5%.

[0050] Add 216.6g of refined compound 12, 1080g of diethyl carbonate, 402.0g of sodium periodate, 21.7mL of 1mg / L ruthenium trichloride aqueous solution to a 2L three-necked flask and place it in a 0°C cold bath for cooling. After the system is cooled to the set temperature, slowly add 216.6g of pure water and stir the reaction for 2h. After the reaction is completed, transfer it to a separatory funnel and let it stand for separation. Take the organic phase and wash the separation with 360g of saturated salt water, repeat three times, and dry the remaining organic phase with 110g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 224.2g of crude product of compound 13. Add 450g of ice water to wash, filter and then add 1120g of acetonitrile to recrystallize, filter and dry under reduced pressure to obtain 208.5g of refined white powder compound 13 product, with a yield of 85.6% and a purity of 99.2%.

[0051] Example 6

[0052] Add 194g of methyl glucoside, 970g of ethyl acetate, and 580.5g of DIPEA to a 2L three-necked flask and place it in a -20°C cold bath to cool. After the system is cooled to the set temperature, slowly add 261.8g of thionyl chloride and stir the reaction for 12h. After the reaction is completed, remove the by-product hydrochloride by vacuum filtration, wash the organic solution with 330g of saturated brine, repeat three times, and dry the remaining organic phase with 100g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 257.4g of the crude product of compound 16 as a white solid. Add 1300g of dimethyl carbonate to it for recrystallization, vacuum filtration, and drying to obtain 231.7g of refined white powdery solid, with a yield of 81.0% and a purity of 99.5%.

[0053] Add 231.7g of refined compound 16, 1160g of ethyl methyl carbonate, 346.2g of sodium periodate, and 23.2mL of 1mg / L ruthenium trichloride aqueous solution to a 2L three-necked flask, and place it in a 0°C cold bath to cool. After the system is cooled to the set temperature, slowly add 231.7g of pure water and stir the reaction for 2h. After the reaction is completed, transfer it to a separatory funnel and let it stand for separation. Take the organic phase and wash the separation with 385g of saturated salt water, repeat three times, and dry the remaining organic phase with 115g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 244.7g of crude compound 17. Add 500g of ice water to wash, filter and then add 1250g of acetonitrile to recrystallize, filter and dry under reduced pressure to obtain 227.6g of refined white powder compound 17 product, with a yield of 88.4% and a purity of 99.2%.

[0054] Example 7

[0055] Add 164g of 2,5-dehydrated mannitol, 820g of ethyl acetate, and 328.5g of DMF to a 2L three-necked flask and place it in a -20°C cold bath to cool. After the system is cooled to the set temperature, slowly add 261.8g of thionyl chloride and stir the reaction for 12h. After the reaction is completed, remove the by-product hydrochloride by vacuum filtration, wash the organic solution with 270g of saturated brine, repeat three times, and dry the remaining organic phase with 80g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain 243.2g of the crude product of compound 9 as a white solid. Add 1200g of dimethyl carbonate to it for recrystallization, vacuum filtration, and drying to obtain 218.9g of refined white powdery solid, with a yield of 85.5% and a purity of 99.4%.

[0056] Add 218.9g of refined compound 9, 1100g of dimethyl carbonate, 21.9mL of 1mg / L ruthenium trichloride aqueous solution to a 2L three-necked flask and place it in a 5°C cold bath to cool. After the system is cooled to the set temperature, slowly add 671.8g of sodium hypochlorite aqueous solution and stir the reaction for 2h. After the reaction is completed, transfer to a separatory funnel and let stand for separation. Take the organic phase and wash the separation with 365g of saturated salt water, repeat three times, and dry the remaining organic phase with 110g of anhydrous magnesium sulfate for 1h. After vacuum filtration, the organic solution is vacuum-rotated to obtain a mixture of compounds 10 and 11 of 209.3g. Add 435g of ice water to wash, filter and then add 500g of acetonitrile to recrystallize, filter and dry under reduced pressure to obtain 194.1g of refined white block compound 11 product, with a yield of 81.1% and a purity of 97.2%.

[0057] Take the structure and purity test results of compound 6 as an example: Figure 1 This is the one-dimensional H-NMR spectrum of the synthetic product compound 6 of Example 3 of the present invention; Figure 2 This is the one-dimensional NMR carbon spectrum of the synthetic product compound 6 of Example 3 of the present invention; Figure 3 This is the ultra-high performance liquid chromatogram of the synthetic product compound 6 of Example 3 of the present invention. The retention time 3.263 min is the target product, and the unmarked peak is the system solvent peak. The purity calculation formula is: target product peak area / sum of peak areas of all substances in the system*100%.

[0058] The non-aqueous electrolyte solution with the compound prepared in the above example as an additive was used to prepare a lithium ion battery, and the non-aqueous electrolyte solution with 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 ethyl methyl carbonate (EMC) are mixed in a mass ratio of EC:DEC:EMC=1:1:1, and then lithium hexafluorophosphate (LiPF6) is added to a molar concentration of 1 mol / L. Additives are 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.

[0061] 2) Preparation of positive electrode sheet:

[0062] 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 binder polyvinylidene fluoride (PVDF), and then disperse them in N-methyl-2-pyrrolidone (NMP) to obtain positive electrode slurry. The slurry is evenly coated on both sides of the aluminum foil, dried, rolled and vacuum dried, and welded with aluminum lead wires using an ultrasonic welder to obtain a positive electrode sheet with a thickness of between 120-150μm.

[0063] 3) Preparation of negative electrode sheet:

[0064] The negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are 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 is coated on both sides of the copper foil, dried, rolled and vacuum dried, and a nickel lead wire is welded with an ultrasonic welder to obtain a negative electrode plate with a thickness of 120-150μm.

[0065] 4) Preparation of battery cells:

[0066] A three-layer separator with a thickness of 20 μm was placed between the positive electrode plate and the negative electrode plate, and then the sandwich structure consisting of the positive electrode sheet, the negative electrode sheet and the 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 to be injected with liquid.

[0067] 5) Battery filling and formation:

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

[0069] Then, the conventional formation of the first charge was carried out according to the following steps: 0.05C constant current charging for 180 min, 0.2C constant current charging to 3.95 V, secondary vacuum sealing, and then further 0.2C constant current charging to 4.2 V, after being placed at room temperature for 24 hours, 0.2C constant current discharge to 3.0 V, to obtain a LiNi 0.5 Co 0.2 Mn 0.3 O2 / artificial graphite lithium-ion battery.

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

[0071] High temperature cycle performance test

[0072] The formed lithium-ion battery is charged at 45°C at a constant current of 1C to 4.2V, then charged at a constant current and constant voltage until the current drops to 0.05C, and then discharged at a constant current of 1C to 3.0V, and the initial impedance of the battery is measured in the first week. This method is used for 1000 cycles of charge and discharge. The calculation formula is as follows:

[0073] Internal resistance growth rate (%) = (1000th week impedance - first week initial impedance) / first week initial impedance × 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 show that the additive of the present invention has a significant function of reducing impedance compared to DTD. This may be because the additive of the present invention contains ether bonds, which makes it have 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 may be arbitrarily combined. 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-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A secondary battery electrolyte additive, characterized in that: 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 the 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: Wherein, 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, characterized in that 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, characterized in that The additive is selected from the compounds shown in the following structural formula:

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

5. The method for preparing the additive according to any one of claims 1 to 3, characterized in that: The following steps are involved: (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, characterized in that: 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, characterized in that: 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 claim 5, 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).

9. The preparation method according to claim 5, characterized in that: 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, 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 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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