Electrolyte additive containing imidazolyl sulfonic anhydride structure as well as preparation method and application of electrolyte additive

Abstract

The invention provides an electrolyte additive containing an imidazolyl sulfonic anhydride structure as well as a preparation method and application of the electrolyte additive. The electrolyte additive has a sulfamic anhydride structure and can react with free HF in the electrolyte, so that the free HF in the electrolyte can be removed, and the effect of relieving erosion of HF to a positive electrode structure is achieved. Meanwhile, the reaction product of the additive and HF can be selectively adsorbed on the surface of the positive electrode material to form a special buffer layer, and the buffer layer can be used as a protective layer to effectively prevent solvent molecules from directly contacting with the positive electrode material. Meanwhile, the reaction product fluorosulfonic anhydride of HF and the unreacted imidazolyl sulfonic anhydride structure can be reduced on the surface of the negative electrode to generate an organic phase rich in N and an inorganic LiF phase, so that huge volume expansion caused by the silicon negative electrode in the charging and discharging process is inhibited, and rapid attenuation of electrochemical performance caused by pulverization of the negative electrode material is avoided.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion batteries, and in particular relates to an electrolyte additive containing an imidazole sulfonic anhydride structure, and a preparation method and application thereof. Background Art

[0002] In recent years, in order to obtain electric vehicles with longer driving range and affordable prices, researchers have made considerable efforts to improve the energy density of lithium-ion batteries. Studies have shown that the use of LiNi 0.8 Mn 0.1 Co 0.1 Nickel-rich layered oxide cathodes such as O2 (abbreviated as: NCM811) can achieve high energy density in lithium-ion batteries.

[0003] At the same time, studies have shown that in order to further improve energy density, it can also be achieved by increasing the charge cut-off voltage. However, increasing the charge cut-off voltage will lead to structural degradation, electrolyte oxidation, and the subsequent formation of a CEI film with high impedance. At the same time, there is electrode crosstalk, and transition metals will dissolve from the positive electrode and deposit on the negative electrode surface, causing the electrolyte to continue to decompose, resulting in the thickening of the SEI film and affecting the performance of the battery cell.

[0004] On the other hand, in the negative electrode material system, the mainstream technical route to improve energy density is to use silicon-graphite composite materials. The core of this solution is to use silicon-based materials (theoretical gram capacity up to 4200mAh / g) and graphite materials to composite and achieve energy density leap by increasing the specific capacity of active materials. However, silicon materials will produce up to 300% volume expansion during the lithium ion insertion / extraction process, which brings dual technical challenges: first, the drastic volume change will cause stress concentration inside the active particles, causing particle rupture or even pulverization, and at the same time causing the physical contact between the active material and the current collector to fail; secondly, the dynamic volume fluctuation will destroy the stability of the solid electrolyte interface film (SEI) on the negative electrode surface. The interface film continues to consume electrolyte and active lithium ions during repeated fracture and reconstruction, which ultimately leads to a decrease in coulombic efficiency (usually <99.5%), an increase in interface impedance, and a rapid decay of cycle capacity. In order to meet the above challenges, the industry currently generally uses silicon dioxide (SiO x , expansion rate of about 160%) replaces pure silicon material, and by constructing a silicon oxide-graphite composite system, while maintaining a relatively high gram capacity (1500-1800mAh / g), the volume expansion rate is controlled within an acceptable range (about 10-15%), thereby significantly improving the stability of the electrode structure.

[0005] Currently, in lithium-ion batteries with a silicon monoxide anode, fluoroethylene carbonate (FEC) is commonly used as an additive in the electrolyte to form an effective SEI film. However, when FEC is used as an electrolyte additive, a large amount of FEC often needs to be added to ensure the formation of a relatively thick LiF-rich SEI film on the surface of the silicon anode. Thus, by utilizing the high mechanical strength and electronic insulation properties of LiF, the rupture of the SEI film caused by the continuous volume expansion of the silicon anode during charge and discharge can be restricted, and the growth of the SEI film in a proliferative manner due to the secondary contact between the active material and the electrolyte solvent can be avoided, thereby preventing the loss of active lithium and gas generation and expansion. However, in the actual process, after introducing a large amount of FEC, under high-temperature operating conditions of the battery, FEC will decompose to generate more HF, which will erode and damage the surface of the cathode material, resulting in the dissolution and migration of transition metals to the anode, further inducing a series of side reactions at the anode interface. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an electrolyte additive containing an imidazole-based sulfonic anhydride structure, as well as its preparation method and application.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides an electrolyte additive containing an imidazole-based sulfonic anhydride structure, having the structure shown in Formula A:

[0009]

[0010] Among them, R1 and R2 are independently selected from a hydrogen atom, a straight-chain alkyl group with 1 to 6 carbon atoms, an alkenyl group with 1 to 6 carbon atoms, or a cyano group.

[0011] Preferably, R1 and R2 are independently selected from a hydrogen atom, a straight-chain alkyl group with 1 to 3 carbon atoms, a vinyl group, or a cyano group.

[0012] Preferably, the electrolyte additive is selected from at least one of the following formulas (I) to (VII):

[0013]

[0014] In the second aspect, the present invention further provides a preparation method for the above-mentioned electrolyte additive containing an imidazole-based sulfonic anhydride structure, including the following steps:

[0015] Mix and react the compound shown in Formula B and the compound shown in Formula C to obtain the electrolyte additive shown in Formula A;

[0016]

[0017] Among them, R1 and R2 are independently selected from a hydrogen atom, a straight-chain alkyl group with 1 to 6 carbon atoms, an alkenyl group with 1 to 6 carbon atoms, or a cyano group.

[0018] Preferably, the molar ratio of the compound represented by Formula B to the compound represented by Formula C is (1 to 1.2):1, more preferably 1.14:1;

[0019] The temperature of the reaction is 20 to 25 °C, and the time is 2 to 3 h.

[0020] In a third aspect, the present invention provides an electrolyte additive for a silicon-based anode lithium-ion battery, comprising a first additive and a second additive;

[0021] The first additive is the electrolyte additive containing an imidazole-based sulfonic anhydride structure involved in the above technical solution;

[0022] The second additive is fluoroethylene carbonate.

[0023] Preferably, the mass ratio of the first additive to the second additive is (0.5 to 2):(5 to 15).

[0024] In a fourth aspect, the present invention further provides a non-aqueous electrolyte for a silicon-based anode lithium-ion battery, comprising a lithium salt, a non-aqueous organic solvent, and the above electrolyte additive.

[0025] Preferably, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, or lithium difluoro bis(oxalato)phosphate.

[0026] Preferably, the non-aqueous organic solvent includes an organic ester solvent or an ether solvent.

[0027] Preferably, the organic ester solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl formate, ethyl acetate, propyl acetate, propyl propionate, or methyl(trifluoroethyl)carbonate.

[0028] Preferably, the ether solvent is selected from at least one of dimethyl ether, diethyl ether, methyl ethyl ether, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, or 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0029] Preferably, the lithium salt accounts for 11 to 16% by weight of the non-aqueous electrolyte.

[0030] Preferably, the non-aqueous organic solvent accounts for 67 to 83.5% by weight of the non-aqueous electrolyte.

[0031] Preferably, the first additive accounts for 0.5 to 2% by weight of the non-aqueous electrolyte.

[0032] Preferably, the second additive accounts for 5-15% of the weight of the non-aqueous electrolyte.

[0033] Fifthly, the present invention also provides a silicon-based anode lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte of the above silicon-based anode lithium-ion battery.

[0034] Preferably, the active material of the positive electrode is selected from at least one of lithium cobaltate, lithium manganate, ternary nickel cobalt manganese lithium, lithium nickel manganate, lithium iron phosphate, or lithium manganese iron phosphate.

[0035] Preferably, the active material of the negative electrode is selected from at least one of a silicon-carbon composite material, a silicon-carbon-graphite composite material, silicon monoxide, or a silicon monoxide-graphite composite material.

[0036] Preferably, the separator is selected from a polypropylene separator, a polyethylene separator, or a polyethylene separator coated with alumina on one side.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The present invention provides an electrolyte additive containing an imidazole-based sulfonic anhydride structure. The sulfamic anhydride structure it has can react with free HF in the electrolyte, thereby removing free HF in the electrolyte and achieving the effect of alleviating the erosion of the positive electrode structure by HF. At the same time, the reaction product of this additive and HF can selectively adsorb on the surface of the positive electrode material to form a special "buffer layer". This buffer layer can serve as a protective layer to effectively block the direct contact between solvent molecules and the positive electrode material, thereby reducing the oxidative decomposition of solvent molecules and highly active positive electrode material at the positive electrode interface under high voltage conditions. At the same time, the reaction product fluorosulfonic anhydride with HF and the unreacted imidazole-based sulfonic anhydride structure can also be reduced on the surface of the negative electrode to generate an organic phase rich in N and an inorganic LiF phase, constructing an organic-inorganic composite elastic SEI film at the negative electrode interface, thereby inhibiting the huge volume expansion caused by the silicon-based negative electrode during charge and discharge and avoiding the rapid attenuation of electrochemical performance caused by the pulverization of the negative electrode material.

[0039] The present invention combines the electrolyte additive containing an imidazole-based sulfonic anhydride structure provided with fluoroethylene carbonate as the electrolyte additive, which can greatly improve the oxidation resistance of the electrolyte, improve the stability at the positive electrode interface under high voltage conditions, and the prepared lithium-ion battery has better electrochemical performance. Specifically, the high-temperature cycle performance and high-temperature storage performance of the prepared high-nickel lithium-ion battery in the voltage range of 3.0-4.33V are significantly improved. Detailed implementation manners

[0040] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0041] In the prior art, in a lithium-ion battery with a silicon-based negative electrode, when fluoroethylene carbonate (FEC) is used as an electrolyte additive, it will cause side reactions at the negative electrode, as well as problems such as loss of active lithium and gas production and expansion. The present invention provides an electrolyte additive containing an imidazole-based sulfonic anhydride structure, which has the structure shown in Formula A:

[0042]

[0043] Among them, R1 and R2 are independently selected from a hydrogen atom, a straight-chain alkyl group having 1 to 6 carbon atoms (such as a methyl group, an ethyl group, a propyl group, etc.), an alkenyl group having 2 to 6 carbon atoms (such as a vinyl group, a propenyl group, etc.) or a cyano group.

[0044] In some preferred embodiments of the present invention, the electrolyte additive containing an imidazole-based sulfonic anhydride structure has the structure shown in Formula A, wherein R1 and R2 are independently selected from a hydrogen atom, a straight-chain alkyl group having 1 to 3 carbon atoms, a vinyl group or a cyano group.

[0045] In some specific embodiments of the present invention, the electrolyte additive containing an imidazole-based sulfonic anhydride structure is selected from at least one of the following formulas (I) to (VII):

[0046]

[0047] The present invention also provides a preparation method for the above-mentioned electrolyte additive containing an imidazole-based sulfonic anhydride structure, but not limited to the preparation method provided by the present invention. Generally, it includes the following steps:

[0048] Mix and react the compound shown in Formula B and the compound shown in Formula C to obtain the electrolyte additive shown in Formula A;

[0049]

[0050] Among them, R1 and R2 are independently selected from a hydrogen atom, a straight-chain alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms or a cyano group.

[0051] In some embodiments of the present invention, the molar ratio of the compound shown in Formula B to the compound shown in Formula C is (1 to 1.2):1, more preferably 1.14:1; the reaction temperature is 20 to 25 °C, such as 20 °C, 22 °C or 25 °C; the time is 2 to 3 h, such as 2 h, 2.5 h or 3 h.

[0052] Specifically, the synthesis route of the above-mentioned electrolyte additive containing an imidazole-based sulfonic anhydride structure is as follows:

[0053]

[0054] In the above synthesis route, methanesulfonic acid reacts with sulfonyl chloride first to obtain a sulfonic anhydride structure intermediate (i.e., the compound shown in Formula B), and then undergoes a substitution reaction with an imidazole-based compound (i.e., the compound shown in Formula C) to obtain the target product (i.e., the compound shown in Formula A).

[0055] It can be seen that the preparation method of the electrolyte additive containing an imidazole-based sulfonic anhydride structure provided by the present invention is simple and convenient, and is easy to implement.

[0056] The above-mentioned electrolyte additive containing an imidazole-based sulfonic anhydride structure provided by the present invention has a sulfamic anhydride structure and can react with free HF in the electrolyte (see the following formula for the specific reaction), thereby removing free HF in the electrolyte and achieving the effect of alleviating the erosion of the positive electrode structure by HF. At the same time, the reaction product of this additive and HF can selectively adsorb on the surface of the positive electrode material to form a special "buffer layer", which can act as a protective layer to effectively block the direct contact between solvent molecules and the positive electrode material, thereby reducing the oxidative decomposition of solvent molecules and highly active positive electrode materials at the positive electrode interface under high voltage conditions. At the same time, the reaction product fluorosulfonic anhydride with HF and the unreacted imidazole-based sulfonic anhydride structure can also be reduced on the surface of the negative electrode to generate an N-rich organic phase and an inorganic LiF phase, constructing an organic-inorganic composite elastic SEI film at the negative electrode interface, thereby inhibiting the huge volume expansion caused by the silicon negative electrode during charge and discharge and avoiding the rapid attenuation of electrochemical performance caused by the pulverization of the negative electrode material.

[0057]

[0058] Based on the advantages of the above-mentioned electrolyte additive containing an imidazole-based sulfonic anhydride structure, the present invention also provides an electrolyte additive for a silicon-based negative electrode lithium-ion battery, which includes a first additive and a second additive. Among them, the first additive is the above-mentioned electrolyte additive containing an imidazole-based sulfonic anhydride structure; the second additive is fluoroethylene carbonate (FEC), and FEC can form a stable SEI film with high mechanical strength on the negative electrode. At the same time, the oxidation-resistant property of FEC itself can avoid dehydrogenation and oxidation decomposition under high voltage conditions.

[0059] In some embodiments of the present invention, the mass ratio of the first additive to the second additive is (0.5 - 2):(5 - 15), preferably (0.8 - 1.5):(8 - 13), and more preferably 1:10.

[0060] The present invention also provides a non-aqueous electrolyte for a silicon-based anode lithium-ion battery, which includes a lithium salt, a non-aqueous organic solvent, and the above electrolyte additive.

[0061] In the present invention, the lithium salt is selected from any one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB), or lithium difluoro(dioxalato)phosphate (LiDODFP).

[0062] In the present invention, the non-aqueous organic solvent includes an organic ester solvent and / or an ether solvent; wherein, the organic ester solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl formate, ethyl acetate, propyl acetate, propyl propionate, or methyl(trifluoroethyl)carbonate; the ether solvent is selected from at least one of dimethyl ether, diethyl ether, methyl ethyl ether, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, or 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0063] In some embodiments of the present invention, the lithium salt accounts for 11-16% by weight of the non-aqueous electrolyte, preferably 13%; the non-aqueous organic solvent accounts for 67-83.5% by weight of the non-aqueous electrolyte, preferably 70-80%, more preferably 76%; the first additive accounts for 0.5-2% by weight of the non-aqueous electrolyte, preferably 0.8%-1.5%, more preferably 1%; the second additive accounts for 5-15% by weight of the non-aqueous electrolyte, preferably 8-13%, more preferably 10%.

[0064] The present invention also provides a silicon-based anode lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte for the silicon-based anode lithium-ion battery.

[0065] In the present invention, the active material of the positive electrode is selected from at least one of lithium cobaltate, lithium manganate, ternary nickel cobalt manganese lithium, lithium nickel manganate, lithium iron phosphate, or lithium manganese iron phosphate, preferably ternary nickel cobalt manganese lithium (Ni9).

[0066] In the present invention, the active material of the negative electrode is selected from at least one of a silicon-carbon composite material, a silicon-carbon-graphite composite material, silicon monoxide, or a silicon monoxide-graphite composite material, preferably a silicon monoxide-graphite composite material, with a specific capacity of 650 mAh g -1 .

[0067] In the present invention, the separator is selected from a polypropylene separator, a polyethylene separator, or a polyethylene separator with one-sided alumina coating, preferably a polyethylene separator with one-sided alumina coating.

[0068] In the non-aqueous electrolyte provided by the present invention, the imidazole-based sulfonic anhydride compound and fluoroethylene carbonate are used in combination as electrolyte additives, which can synergistically and significantly improve the oxidation resistance of the electrolyte and enhance the stability at the positive electrode interface under high voltage conditions. At the same time, the special imidazole-based sulfonic anhydride structure and the fluoro sulfonic anhydride compound after reaction with HF can also be simultaneously reduced on the negative electrode surface to generate an organic phase and an inorganic phase, constructing an organic-inorganic composite elastic SEI film at the negative electrode interface, thereby alleviating the rapid decay of the electrochemical performance caused by the huge volume expansion of the silicon negative electrode during charge and discharge.

[0069] Test results show that the lithium-ion battery made with the non-aqueous electrolyte provided by the present invention has better electrochemical performance. Specifically, the high-temperature cycle performance and high-temperature storage performance of the prepared high-nickel lithium-ion battery in the voltage range of 3.0 - 4.3V have been significantly improved.

[0070] To further illustrate the present invention, the following examples are provided for detailed description. For those not specifying specific conditions in the examples, they can be carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products available through commercial channels.

[0071] Example 1

[0072] Prepare intermediate compound 1, and the specific steps are as follows:

[0073]

[0074] First, under a nitrogen atmosphere, 125 mL of anhydrous ether was added to a clean and dry 500 mL three-necked flask equipped with a magnetic rotor. The flask was placed in a dry ice / acetone bath. After starting stirring and controlling the solution temperature to drop to -78 °C, then sulfuryl chloride (8.36 mL, 0.1 mol) was slowly added. After the addition was complete, the low-temperature state was maintained. Subsequently, another clean and dry 500 mL three-necked flask equipped with a magnetic rotor and a constant-pressure dropping funnel was taken. Under a nitrogen atmosphere, methanesulfonic acid (9.61 g, 0.1 mol) was added, then 125 mL of anhydrous ether and pyridine (7.91 g, 0.1 mol) were added. Stirring was started and the flask was placed in a dry ice / acetone bath to lower the temperature of the mixed system to -78 °C. An ether solution containing sulfuryl chloride maintained at a low temperature was extracted with a syringe and then transferred and injected into the constant-pressure dropping funnel. Subsequently, it was slowly dropped into the mixed system containing methanesulfonic acid, and the dropping rate was controlled to be completed within 20 - 30 min. Then, stirring was continued for 2 h. Then, dry ice was not added to the dry ice / acetone bath, and the temperature of the reaction system was gradually raised to room temperature, and the stirring reaction was ended overnight. After the reaction was completed, suction filtration was carried out using diatomaceous earth, and the reaction flask was rinsed with 200 mL of ether, and filtration was continued. After combining the organic phases, it was concentrated by distillation under reduced pressure. The residue was purified by a silica gel chromatography column, and the eluent was a petroleum ether mixed solution containing 5 vol% ethyl acetate. After removing the solvent by distillation under reduced pressure, compound 1 was obtained with a yield of 79.2%. GCMS (m / z): calcd. for CH3O5S2Cl, 193.91, found 194.03.

[0075] Compound (I) was prepared as follows:

[0076]

[0077] Under a nitrogen atmosphere, intermediate 1 (6.21 g, 32.00 mmol), compound 2 (2.46 g, 30.00 mmol), sodium hydroxide (1.60 g, 40.00 mmol), and N,N-dimethylformamide (200 mL) were successively added to a clean and dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was stirred at room temperature for 3 h. After the reaction was completed, 300 mL of distilled water pre-cooled to 0 °C was added, and then the mixed solution was extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by distillation under reduced pressure, and using n-hexane as the eluent, after purification by a silica gel chromatography column, compound (I) was obtained with a yield of 75.3%. GCMS (m / z): calcd. for C5H8N2O5S2, 239.99, found 240.08.

[0078] The electrolyte 1 sample was prepared as follows:

[0079] In an argon glove box with the water and oxygen content both ≤ 0.1 ppm, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed in a volume ratio of 5:10:50:35 to obtain an organic solvent. Subsequently, lithium hexafluorophosphate (LiPF6) was slowly added to the organic solvent. After complete dissolution, compound (I) and FEC were added, and after stirring evenly, electrolyte 1 was obtained. Among them, the usage amounts of LiPF6, the organic solvent, compound (I), and FEC were 13%, 76%, 1%, and 10% of the total mass of the electrolyte, respectively.

[0080] Prepare a sample of experimental battery 1, and the specific steps are as follows:

[0081] Preparation of the positive electrode sheet: The positive electrode material nickel cobalt manganese lithium (Ni9), the conductive agent carbon black (SuperP), and the carbon nanotubes (CNT, an NMP solution with a mass fraction of 5%) binder polyvinylidene fluoride (PVDF, an NMP solution with a mass fraction of 5%) were weighed and mixed in a mass ratio of 97:0.7:0.8:1.5. After mixing, an appropriate amount of NMP was added to control the theoretical solid content to 65%. The positive electrode slurry was obtained by homogenization using a planetary homogenizer, and the positive electrode slurry was uniformly coated on an aluminum foil with a thickness of 13 μm. After drying, rolling, and cutting, a 50 mm × 70 mm positive electrode sheet was obtained.

[0082] Preparation of the separator: A polyethylene separator with single-sided alumina coating was used as the isolation membrane, and it was left standing in a drying room with a dew point of -35°C for 72 h before use.

[0083] Preparation of the negative electrode sheet: The negative electrode material silicon monoxide (gravimetric capacity 650 mAh g -1 )), the conductive agent SuperP, the thickening agent sodium carboxymethyl cellulose (CMC, an aqueous deionized solution with a solid content of 1.5%), and the binder polyacrylic acid (PAA, an aqueous deionized solution with a solid content of 6%) were mixed in a mass ratio of 95:1:1.5:2.5 (excluding the solvent). After mixing, deionized water was added to control the theoretical solid content to 55%. The negative electrode slurry was obtained by homogenization using a planetary homogenizer, and the negative electrode slurry was uniformly coated on the above-prepared composite modified copper foil. After drying, rolling, and cutting, a 52 mm × 72 mm negative electrode sheet was obtained. The N / P ratio of the positive and negative electrodes was 1.1.

[0084] Preparation of the battery: The battery was fabricated in a drying room with an ambient dew point ≤ -35°C. The separator was folded in a Z shape, and the positive electrode sheet and the negative electrode sheet were placed on each side. There were 12 layers of the positive electrode sheet and 13 layers of the negative electrode sheet. The positive electrode, separator, and negative electrode were stacked in sequence and aligned. The separator with the alumina-coated side faced the positive electrode to obtain an electrode assembly. After fixing the electrode assembly with polyimide tape, the tab welding was carried out. Subsequently, it was placed in an aluminum-plastic film, then vacuum baked at 90°C for 24 h. After cooling, the prepared electrolyte 1 was injected. Finally, after vacuum packaging, high-temperature infiltration, formation, aging, secondary packaging, and grading, the experimental battery 1 with a capacity of approximately 2.5 Ah was obtained.

[0085] Example 2

[0086] Compound (II) was prepared as follows:

[0087]

[0088] Under a nitrogen atmosphere, intermediate 1 (6.21 g, 32.00 mmol), compound 3 (2.88 g, 30.00 mmol), sodium hydroxide (1.60 g, 40.00 mmol), and N,N-dimethylformamide (200 mL) were successively added to a clean and dry 500 mL three-necked flask equipped with a magnetic rotor. Stirring was started, and the mixture was stirred at room temperature for 3 h. After the reaction was completed, 300 mL of distilled water pre-cooled to 0°C was added. Subsequently, the mixed solution was extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by vacuum distillation, and n-hexane was used as the eluent. After purification by silica gel column chromatography, compound (II) was obtained with a yield of 74.2%. GCMS (m / z): calcd. for C6H 10 N2O5S2, 254.00, found 254.16.

[0089] The electrolyte 2 sample was prepared according to the steps of Example 1, except that the usage amounts of LiPF6, organic solvent, compound (II), and FEC were 13%, 70%, 2%, and 15% of the total mass of the electrolyte, respectively.

[0090] The battery 2 sample was prepared according to the steps of Example 1.

[0091] Example 3

[0092] Compound (III) was prepared as follows:

[0093]

[0094] Under a nitrogen atmosphere, into a clean and dry 500 mL three-necked flask equipped with a magnetic rotor, intermediate 1 (6.21 g, 32.00 mmol), compound 4 (3.30 g, 30.00 mmol), sodium hydroxide (1.60 g, 40.00 mmol), and N,N-dimethylformamide (200 mL) were added in sequence. Stirring was started, and the mixture was stirred at room temperature for 3 h. After the reaction was completed, 300 mL of distilled water pre-cooled to 0 °C was added. Subsequently, the mixed solution was extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by distillation under reduced pressure, and n-hexane was used as the eluent. After purification by silica gel column chromatography, compound (III) was obtained with a yield of 72.1%. GCMS (m / z): calcd. for C7H 12 N2O5S2, 268.02, found 268.20.

[0095] The electrolyte 3 sample was prepared according to the steps of Example 1, except that the amounts of LiPF6, organic solvent, compound (III), and FEC used were 13%, 81.5%, 0.5%, and 5% of the total mass of the electrolyte, respectively.

[0096] The battery 3 sample was prepared according to the steps of Example 1.

[0097] Example 4

[0098] Compound (IV) was prepared, and the specific steps were as follows:

[0099]

[0100] Under a nitrogen atmosphere, into a clean and dry 500 mL three-necked flask equipped with a magnetic rotor, intermediate 1 (6.21 g, 32.00 mmol), compound 5 (2.82 g, 30.00 mmol), sodium hydroxide (1.60 g, 40.00 mmol), and N,N-dimethylformamide (200 mL) were added in sequence. Stirring was started, and the mixture was stirred at room temperature for 3 h. After the reaction was completed, 300 mL of distilled water pre-cooled to 0 °C was added. Subsequently, the mixed solution was extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by distillation under reduced pressure, and n-hexane was used as the eluent. After purification by silica gel column chromatography, compound (IV) was obtained with a yield of 71.8%. GCMS (m / z): calcd. for C6H8N2O5S2, 251.99, found 252.08.

[0101] The electrolyte 4 sample was prepared according to the steps of Example 1, except that the amounts of LiPF6, organic solvent, compound (IV), and FEC used were 11%, 83.5%, 0.5%, and 5% of the total mass of the electrolyte, respectively.

[0102] Prepare the battery 4 sample according to the steps of Example 1.

[0103] Example 5

[0104] Prepare compound (V) according to the following specific steps:

[0105]

[0106] Under a nitrogen atmosphere, add intermediate 1 (6.21 g, 32.00 mmol), compound 6 (2.82 g, 30.00 mmol), sodium hydroxide (1.60 g, 40.00 mmol) and N,N-dimethylformamide (200 mL) successively into a clean and dry 500 mL three-necked flask equipped with a magnetic rotor. Start stirring and stir the mixture at room temperature for 3 h. After the reaction is completed, add 300 mL of distilled water pre-cooled to 0 °C, and then extract the mixed solution with chloroform (3 × 100 mL). Combine the organic phases, distill off the solvent under reduced pressure, and purify through a silica gel chromatography column using n-hexane as the eluent to obtain compound (V) with a yield of 71.0%. GCMS (m / z): calcd. for C6H8N2O5S2, 251.99, found 252.21.

[0107] Prepare the electrolyte 5 sample according to the steps of Example 1, except that the usage amounts of LiPF6, organic solvent, compound (V), and FEC are 16%, 67%, 2%, and 15% of the total mass of the electrolyte, respectively.

[0108] Prepare the battery 5 sample according to the steps of Example 1.

[0109] Example 6

[0110] Prepare compound (VI) according to the following specific steps:

[0111]

[0112] Under a nitrogen atmosphere, into a clean and dry 500 mL three-necked flask equipped with a magnetic rotor, intermediate 1 (6.21 g, 32.00 mmol), compound 7 (2.79 g, 30.00 mmol), sodium hydroxide (1.60 g, 40.00 mmol) and N,N-dimethylformamide (200 mL) were added in sequence. Stirring was started, and the mixture was stirred at room temperature for 3 h. After the reaction was completed, 300 mL of distilled water pre-cooled to 0 °C was added. Subsequently, the mixed solution was extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by distillation under reduced pressure, and n-hexane was used as the eluent. After purification by silica gel column chromatography, compound (VI) was obtained with a yield of 69.5%. GCMS (m / z): calcd. for C5H5N3O5S2, 250.97, found 251.34.

[0113] The electrolyte 6 sample was prepared according to the steps of Example 1, except that the usage amounts of LiPF6, organic solvent, compound (VI), and FEC were 14%, 73%, 1%, and 12% of the total mass of the electrolyte, respectively.

[0114] The battery 6 sample was prepared according to the steps of Example 1.

[0115] Example 7

[0116] Compound (VII) was prepared, and the specific steps were as follows:

[0117]

[0118] Under a nitrogen atmosphere, into a clean and dry 500 mL three-necked flask equipped with a magnetic rotor, intermediate 1 (6.21 g, 32.00 mmol), compound 8 (2.79 g, 30.00 mmol), sodium hydroxide (1.60 g, 40.00 mmol) and N,N-dimethylformamide (200 mL) were added in sequence. Stirring was started, and the mixture was stirred at room temperature for 3 h. After the reaction was completed, 300 mL of distilled water pre-cooled to 0 °C was added. Subsequently, the mixed solution was extracted with chloroform (3 × 100 mL). The organic phases were combined, the solvent was removed by distillation under reduced pressure, and n-hexane was used as the eluent. After purification by silica gel column chromatography, compound (VII) was obtained with a yield of 68.2%. GCMS (m / z): calcd. for C5H5N3O5S2, 250.97, found 251.27.

[0119] The electrolyte 7 sample was prepared according to the steps of Example 1, except that the usage amounts of LiPF6, organic solvent, compound (VII), and FEC were 13%, 78%, 1%, and 8% of the total mass of the electrolyte, respectively.

[0120] Prepare the battery 7 sample according to the steps of Example 1.

[0121] Comparative Example 1

[0122] Prepare the electrolyte 8 sample according to the steps of Example 1, except that the first additive is removed, and the usage amounts of LiPF6, organic solvent, and FEC are 13%, 77%, and 10% of the total mass of the electrolyte respectively. Prepare the battery 8 sample according to the steps of Example 1.

[0123] Comparative Example 2

[0124] Prepare the electrolyte 9 sample according to the steps of Example 1, except that the first additive is methylene methanedisulfonate (MMDS), and the usage amounts of LiPF6, organic solvent, MMDS, and FEC are 13%, 76%, 1%, and 10% of the total mass of the electrolyte respectively.

[0125] Prepare the battery 9 sample according to the steps of Example 1.

[0126] Comparative Example 3

[0127] Prepare the electrolyte 10 sample according to the steps of Example 1, except that the first additive is vinylene sulfate (DTD), and the usage amounts of LiPF6, organic solvent, DTD, and FEC are 13%, 76%, 1%, and 10% of the total mass of the electrolyte respectively.

[0128] Prepare the battery 10 sample according to the steps of Example 1.

[0129] Comparative Example 4

[0130] Prepare the electrolyte 11 sample according to the steps of Example 1, except that the first additive is 1,3 - propane sultone (PS), and the usage amounts of LiPF6, organic solvent, PS, and FEC are 13%, 76%, 1%, and 10% of the total mass of the electrolyte respectively.

[0131] Prepare the battery 11 sample according to the steps of Example 1.

[0132] Perform room - temperature cycle performance tests, high - temperature cycle performance tests, and high - temperature storage performance tests on the experimental batteries made from Examples 1 - 7 and Comparative Examples 1 - 4, that is, lithium - ion batteries. The test conditions are as follows:

[0133] Battery room - temperature cycle test

[0134] The prepared lithium-ion battery was placed in a constant-temperature chamber at an ambient temperature of 25°C and charged at a current of 1C and a voltage of 4.3V with constant current and constant voltage until the cut-off current reached 0.05C. Then, it was discharged at a constant current of 1C until the voltage reached 3V, and this cycle was repeated 800 times. Record the capacity retention rate. The capacity retention rate (%) in the nth cycle = (discharge capacity in the nth cycle / discharge capacity in the first cycle) × 100%.

[0135] Battery high-temperature cycle test

[0136] The prepared lithium-ion battery was placed in a high-low temperature oven at a temperature of 45°C and left standing for 4 hours to stabilize the internal and external temperatures of the battery. It was charged at a current of 1C and a voltage of 4.3V with constant current and constant voltage until the cut-off current reached 0.05C. Then, it was discharged at a constant current of 1C until the voltage reached 3V, and this cycle was repeated 800 times. Record the capacity retention rate. The capacity retention rate (%) in the nth cycle = (discharge capacity in the nth cycle / discharge capacity in the first cycle) × 100%.

[0137] High-temperature storage performance test

[0138] Perform a 1C rate charge-discharge cycle at 25°C for one week, record the discharge capacity. Then, charge the battery at a constant current of 1C to 50% SOC, and measure the DCIR of the battery at 50% SOC. Use the drainage method to measure the battery volume, denoted as V0. Then, charge the battery at a constant current and constant voltage of 1C to a voltage of 4.3V with a cut-off current of 0.05C. After the battery is stored in a high-temperature explosion-proof box at 60°C for one week, discharge it at 1C to 3V at 25°C and then perform a 1C charge-discharge cycle for one week. Then, discharge the battery at 1C to 50% SOC at 25°C and measure the DCIR at 50% SOC. Use the drainage method to measure the battery volume, denoted as V1. Calculate the capacity retention rate, capacity recovery rate, internal resistance (DCR) growth rate, and volume expansion rate.

[0139] Capacity recovery rate = discharge capacity in the second cycle after high-temperature storage / discharge capacity in the last week before high-temperature storage × 100%.

[0140] After the test, measure the battery volume V1. The volume expansion rate (%) = (V1 - V0) × 100% / V0.

[0141] Table 1 below shows the compositions of the electrolytes in Examples 1-7 and Comparative Examples 1-4 of the present invention, and Table 2 shows the test results.

[0142] Table 1 Compositions of the electrolytes in Examples 1-7 and Comparative Examples 1-4 of the present invention

[0143]

[0144]

[0145] Table 2 Electrochemical performance table of Examples 1-7 and Comparative Examples 1-4

[0146]

[0147]

[0148] As can be seen from the data in Table 2, Examples 1 to 7 all exhibit excellent electrochemical performance. This is because the compound (I) containing imidazolyl sulfonic anhydride can react with HF generated by the decomposition of FEC, achieving the effect of alleviating the erosion of the cathode structure by HF. At the same time, the reaction product of this additive and HF can selectively adsorb on the surface of the cathode material to form a special "buffer layer", which can act as a protective layer to effectively block the direct contact between solvent molecules and the cathode material, avoiding the excessive dissolution and deposition of metal on the surface of the negative electrode, which catalyzes the decomposition and gas generation of the electrolyte. At the same time, a composite SEI film rich in N-containing organic phase and inorganic LiF phase can be reductively generated on the surface of the negative electrode, thereby inhibiting the huge volume expansion caused by the silicon negative electrode during charge and discharge and avoiding the rapid decay of electrochemical performance caused by the pulverization of the negative electrode material.

[0149] According to the comparison of the data results between Comparative Example 1 and the Examples, it can be seen that when the electrolyte additive containing imidazolyl sulfonic anhydride structure of the present invention is used in combination with FEC, compared with the use of FEC alone, the high-temperature cycling performance and high-temperature storage performance of the battery cells have been significantly improved, and the volume expansion rate has been significantly reduced, indicating that the compound containing imidazolyl sulfonic anhydride structure of the present invention has a significant improvement in the gas generation during high-temperature storage of the electrolyte.

[0150] According to the comparison of the data results between Comparative Examples 2, 3, 4 and the Examples, it can be seen that the compound containing imidazolyl sulfonic anhydride of the present invention exhibits more excellent cycling performance when used in combination with FEC compared with other commercially available sulfate-based and sulfonate-based additives. In the high-temperature storage test, the compound containing imidazolyl sulfonic anhydride can inhibit the volume expansion of the silicon negative electrode and the side reactions of the electrolyte, reducing the gas generation of the battery.

[0151] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electrolyte additive containing an imidazole-based sulfonic anhydride structure, characterized in that, It has the structure shown in Formula A: Wherein, R1 and R2 are independently selected from a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a cyano group.

2. The electrolyte additive containing an imidazolylsulfonic anhydride structure according to claim 1, wherein The electrolyte additive is selected from at least one of the following formulas (I) to (VII):

3. A preparation method of an electrolyte additive containing an imidazole-based sulfonic anhydride structure as described in claim 1 or 2, characterized in that, It includes the following steps: Mix and react the compound shown in Formula B and the compound shown in Formula C to obtain the electrolyte additive shown in Formula A; Wherein, R1 and R2 are independently selected from a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, or a cyano group.

4. The preparation method according to claim 3, characterized in that, The molar ratio of the compound shown in Formula B to the compound shown in Formula C is (1 to 1.2):1; The temperature of the reaction is 20 to 25 °C, and the time is 2 to 3 h.

5. An electrolyte additive for a silicon-based anode lithium-ion battery, characterized in that, It includes a first additive and a second additive; The first additive is the electrolyte additive containing an imidazole-based sulfonic anhydride structure described in Claim 1 or 2, or the electrolyte additive containing an imidazole-based sulfonic anhydride structure prepared by the preparation method described in Claim 3 or 4; The second additive is fluoroethylene carbonate.

6. The electrolyte additive for the silicon-based anode lithium-ion battery according to claim 5, characterized in that, The mass ratio of the first additive to the second additive is (0.5 to 2):(5 to 15).

7. A non-aqueous electrolyte for a silicon-based anode lithium-ion battery, characterized in that, It includes a lithium salt, a non-aqueous organic solvent, and the electrolyte additive described in Claim 5 or 6.

8. The non-aqueous electrolyte for a silicon-based anode lithium-ion battery according to claim 7, characterized in that, The lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, or lithium difluoro(dioxalato)phosphate; The non-aqueous organic solvent includes an organic ester solvent and / or an ether solvent; The organic ester solvent is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethyl formate, ethyl acetate, propyl acetate, propyl propionate, or methyl(trifluoroethyl)carbonate; The ether solvent is selected from at least one of dimethyl ether, diethyl ether, methyl ethyl ether, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, or 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

9. The non-aqueous electrolyte of the silicon-based anode lithium-ion battery according to claim 7 or 8, wherein The lithium salt accounts for 11 to 16% by weight of the non-aqueous electrolyte; The non-aqueous organic solvent accounts for 67 to 83.5% by weight of the non-aqueous electrolyte; The first additive accounts for 0.5 to 2% by weight of the non-aqueous electrolyte; The second additive accounts for 5 to 15% by weight of the non-aqueous electrolyte.

10. A silicon-based anode lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte of a silicon-based negative electrode lithium ion battery described in any one of Claims 7 to 9; The active material of the positive electrode is selected from at least one of lithium cobaltate, lithium manganate, ternary nickel cobalt manganese lithium, nickel manganese acid lithium, lithium iron phosphate, or lithium manganese iron phosphate; The active material of the negative electrode is selected from at least one of a silicon-carbon composite material, a silicon-carbon-graphite composite material, silicon monoxide, or a silicon monoxide-graphite composite material; The separator is selected from a polypropylene separator, a polyethylene separator, or a polyethylene separator with a single-sided coating of alumina.

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