Electrolyte containing siloxy phosphorene ester compound and energy storage device containing electrolyte

Abstract

The invention relates to an electrolyte containing a siloxy phosphorene ester compound and an energy storage device containing the electrolyte. The electrolyte comprises an electrolyte, an organic solvent, an additive and an additive, the additive is the siloxy-containing phosphorene compound with a structure as shown in a formula I, and the additive comprises any one or a combination of two of vinylene carbonate, 1, 3-propane sultone or ethylene sulfate. According to the electrolyte, the siloxy-containing phosphoenyl ester compound with the structure shown in the formula I serves as an additive to be matched with the additive, so that the discharge rate performance, the low-temperature discharge performance, the cycle performance and the like of the obtained energy storage device can be improved, and meanwhile, the safety of the energy storage device can be remarkably improved; and therefore, the device has the characteristics of long service life and high safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical energy storage, and in particular to an electrolyte containing a silicon-oxygen-containing phosphonate compound and an energy storage device containing the same. BACKGROUND

[0002] At present, the organic electrolyte material used in the lithium battery industry is mainly a silicon-oxygen-containing carbonate compound and a LiPF6 lithium salt system, and its performance is greatly reduced at high temperature (above 60℃), and its performance is reduced at low temperature (below-10℃), and the working temperature range of the power battery required by the electric vehicle is higher (about-30~80℃); and the silicon-oxygen-containing carbonate organic electrolyte material has high flammability, so there is a great hidden danger in safety; especially in the application field of hybrid and all-electric vehicles, long-term cycle problems and safety are important factors restricting the practical application of these materials.

[0003] The electrolyte is an important component of the lithium ion battery, which plays a role in transmitting lithium ions between the positive and negative electrodes. The traditional functional components in the electrolyte play a key role in prolonging the service life of the battery, but there is no long-term effective measure to delay or inhibit the generation of lithium dendrites, which greatly affects the safety performance and the service life of the charge and discharge cycle of the battery.

[0004] CN106033824A is an electrolyte for a high-voltage lithium ion battery, which contains tris(trimethylsilyl)borate, and the high-voltage lithium ion battery containing the electrolyte has excellent normal temperature cycle performance, high temperature cycle performance, high temperature storage performance and low temperature discharge performance. However, this substance cannot meet the safety requirements of the battery.

[0005] Therefore, with the increasing demand for high energy density of energy storage devices, it is essential to design and develop an electrolyte that can improve the safety and stability of the energy storage device while ensuring good cycle performance of the energy storage device. SUMMARY

[0006] To solve the above technical problems, the present application provides an electrolyte containing a silicon-oxygen-containing phosphonate compound and an energy storage device containing the same. The electrolyte containing the silicon-oxygen-containing phosphonate compound can improve the discharge rate performance, low temperature discharge performance and cycle performance of the obtained energy storage device, and can significantly improve the safety of the energy storage device, thereby having the characteristics of high service life and high safety.

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

[0008] In a first aspect, the present application provides an electrolyte containing a siloxy phosphate ester compound, the electrolyte comprising an electrolyte, an organic solvent, an additive, and an additive aid, the additive being a siloxy phosphate ester compound having a structure shown in Formula I:

[0009] Formula I;

[0010] wherein R1, R2, and R3 are the same or different, each independently selected from a substituted or unsubstituted C1-C6 alkyl group; and R4 is selected from H, a halogen, a substituted or unsubstituted C1-C4 alkyl group.

[0011] The substituted substituent group is selected from fluorine, a C1-C4 alkyl group, or a C1-C4 alkoxy group.

[0012] The additive aid comprises any one of vinyl carbonate (VC), 1,3-propane sultone (PS), or vinyl sulfate (DTD), or a combination of at least two thereof.

[0013] The present application, by designing the composition of the electrolyte, collocates the siloxy phosphate ester compound having a structure shown in Formula I as an additive with an additive aid, so as to be able to play a good synergistic effect, so that the electrolyte applied to an energy storage device can have good discharge rate performance, low-temperature discharge performance, and cycle performance, while also having excellent safety performance, and excellent comprehensive performance.

[0014] In the present application, the C1-C6 alkyl group can be a C1, C2, C3, C4, C5, or C6 alkyl group, the C1-C4 alkyl group can be a C1, C2, C3, or C4 alkyl group, and the C1-C4 alkoxy group can be a C1, C2, C3, or C4 alkoxy group.

[0015] The following is a preferred technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following preferred technical solution, the purpose and beneficial effects of the present application can be better achieved and realized.

[0016] As a preferred technical solution of the present application, R1, R2, and R3 are the same or different, each independently selected from any one of -CH3, -CH2CH3, -CF3, or -CH2CF3.

[0017] R4 is selected from any one of H, -CH3, or -CF3.

[0018] As a preferred technical solution of the present application, the mass percentage of the additive in the electrolyte is 0.1-20%, for example, it can be 0.1%, 0.5%, 1%, 3%, 5%, 10%, 12%, 15%, 18% or 20%, and specific point values between the above point values, limited to the length and for the sake of simplicity, the present application does not exhaustively list the specific point values included in the range, and preferably 1-20%.

[0019] The siloxyl-containing phosphonate compound with the structure shown in formula I in the present application is a liquid polar compound with high boiling point (boiling point greater than 260℃), low melting point (melting point lower than -40℃) and flame retardant performance, which can be well miscible with carbonate organic solvents, and also has good solubility to electrolytes such as lithium nitrate and lithium hexafluorophosphate, thereby improving the cycle stability and heat resistance of the obtained energy storage device. When the mass percentage is in the range of 0.1-20%, with the increase of the mass percentage, the discharge rate performance, low-temperature discharge performance and cycle performance show a trend of first increasing and then decreasing, and the safety performance gradually increases. Further, by optimizing the mass percentage of the additive, the obtained battery has better comprehensive performance, especially the cycle life and safety can be significantly improved. When the mass percentage is low, the concentration of the additive in the electrolyte is low, and the effect of improving the battery performance is not good. When the mass percentage is too high, the overall viscosity of the electrolyte is increased, which is not conducive to the infiltration of the electrolyte, thereby causing problems such as insufficient formation of the battery, imperfect interface film, deterioration of cycle performance and storage performance, and thus is not conducive to actual production.

[0020] As a preferred technical solution of the present application, the additive is a combination of 1,3-propanesulfonic acid lactone and ethylene sulfate.

[0021] In the present application, the additive is further preferably a combination of 1,3-propanesulfonic acid lactone and ethylene sulfate. In the high-nickel battery system, due to the poor oxidation resistance of VC, the combination of PS and DTD can be better matched with the siloxyl-containing phosphonate compound with the structure shown in formula I, thereby helping to improve the safe cycle operation of the obtained battery.

[0022] Preferably, the mass percentage of the additive in the electrolyte is 0.5-2%, for example, it can be 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8% or 2.0%, and specific point values between the above point values, limited to the length and for the sake of simplicity, the present application does not exhaustively list the specific point values included in the range.

[0023] The application can well control the mass ratio of the electrolyte and the additive by optimizing the content of the additive, so that the obtained electrolyte has more excellent comprehensive performance when used in energy storage devices. Preferably, the electrolyte comprises any one or a combination of at least two of XClO4 (perchlorate), XPF6 (hexafluorophosphate), XBF4 (tetrafluoroborate), XTFSI (bistrifluoromethanesulfonylimide), XFSI (bifluorosulfonylimide), XBOB (bisoxalate borate), XODFB (difluoro oxalate borate), XCF3SO3 (triflate), XAsF6 (hexafluoroarsenate) or XNO3 (nitrate); wherein X is selected from any one of Li, Na or K.

[0024] Preferably, the mass percentage of the electrolyte in the electrolyte is 8-20%, for example, can be 8%, 10%, 12%, 14%, 16%, 18% or 20%, and specific point values between the above point values, limited to the length and for the sake of simplicity, the application will not exhaustively list the specific point values included in the range.

[0025] Preferably, the organic solvent comprises any one or a combination of at least two of carbonates, carboxylic acid esters, fluorinated carboxylic acid esters, fluorinated ethers or aromatic hydrocarbons.

[0026] Preferably, the mass percentage of the organic solvent in the electrolyte is 60-91.4%, for example, can be 60%, 65%, 70%, 75%, 80%, 85%, 90% or 91.4%, and specific point values between the above point values, limited to the length and for the sake of simplicity, the application will not exhaustively list the specific point values included in the range.

[0027] Preferably, the carbonates include halogenated carbonates and / or non-halogenated carbonates.

[0028] Preferably, the halogenated carbonates include any one or a combination of at least two of vinyl fluoride carbonate, difluorovinyl carbonate, difluoropropylene carbonate, trifluoroethyl acetate, trifluoroethyl methyl carbonate, trifluoromethyl vinyl carbonate, 4-trifluoromethyl vinyl carbonate, vinyl chloride carbonate, bis (2,2,2-trifluoroethyl) carbonate, trifluoropropyl methyl carbonate, 3,3,3-trifluoroethyl acetate, 2-trifluoromethyl methyl benzoate, 4,4,4-trifluorobutyl ethyl carbonate or 1,1,1,3,3,3-hexafluoroisopropyl propenoate.

[0029] Preferably, the non-halogenated carbonates include any one or a combination of at least two of vinyl carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate or methyl ethyl carbonate.

[0030] Preferably, the carboxylic acid ester comprises a halogenated carboxylic acid ester and / or a non-halogenated carboxylic acid ester.

[0031] Preferably, the halogenated carboxylic acid ester comprises any one of or a combination of propyl fluorobutyrate, propyl fluoroacetate, isopropyl fluoroacetate, butyl fluoropropionate, isopropyl fluoropropionate, ethyl fluorobutyrate, methyl fluoropropionate, ethyl fluoropropionate or propyl fluoropropionate.

[0032] Preferably, the non-halogenated carboxylic acid ester comprises any one of or a combination of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate or propyl propionate.

[0033] Preferably, the fluoroether is a fluoroether having a carbon atom number of ≤7, which can be, for example, 1, 2, 3, 4, 5, 6 or 7, and specific point values between the aforementioned point values, which are not exhaustively listed in the present disclosure for the sake of brevity and conciseness.

[0034] Preferably, the aromatic hydrocarbon comprises a halogenated aromatic hydrocarbon and / or a non-halogenated aromatic hydrocarbon.

[0035] Preferably, the halogenated aromatic hydrocarbon comprises any one of or a combination of monofluorobenzene, difluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene or 2,4-dichlorotrifluorotoluene.

[0036] In a second aspect, the present disclosure provides an energy storage device comprising the electrolyte of the siloxy-containing phosphonate ester compound of the first aspect.

[0037] Preferably, the energy storage device comprises a lithium ion battery, a sodium ion battery, a potassium ion battery or a supercapacitor.

[0038] Preferably, the negative electrode material of the energy storage device comprises any one of or a combination of graphite, soft carbon, hard carbon, a composite of single-crystal silicon and graphite, a composite of silicon monoxide and graphite, lithium titanate or di-niobium pentoxide.

[0039] It should be noted that the preparation method of the lithium ion battery in the present application is not particularly limited, and the commonly used preparation methods in the art are applicable, including but not limited to the following preparation methods: the positive electrode uses a binder PVDF-S5130, a composite conductive agent Super-P / KS-6 (mass ratio Super-P:KS-6=2:1), an 811 nickel cobalt manganese ternary positive electrode material or a lithium cobaltate positive electrode material, and a solvent NMP (N-methyl-2-pyrrolidone); the negative electrode uses C-P15 or a silicon-carbon composite material (BETTERREY S420), a conductive agent Super-P, a solvent CMC, H2O, and a binder SBR as raw materials, and a slurry is prepared by using a wet slurry process respectively, the positive electrode is adjusted to a viscosity of 10000-13000 mPa·s, the negative electrode is adjusted to a viscosity of 1500-3000 mPa·s, the N / P ratio is designed to be 1.12, the capacity is 1.6-1.9 Ah, and then the lithium ion battery is prepared by coating, slicing, rolling, striping, drying at 140℃ for 8 h, pasting a tape, winding the battery core, drying at 80℃ for 48 h, and then injecting and sealing the electrolyte according to the following different electrolyte formulations, standing for 24 h, forming, primary final sealing, aging, secondary final sealing, to obtain a lithium ion soft package battery.

[0040] Compared with the prior art, the present application has at least the following beneficial effects:

[0041] (1) The present application can be well applied to energy storage devices by designing the composition of the electrolyte, using a siloxyl-containing phosphonate ester compound represented by formula I as an additive and an additive aid, so that the energy storage devices have good discharge rate performance, low-temperature discharge performance and cycle performance, and excellent safety performance, and excellent comprehensive performance.

[0042] (2) The electrolyte provided by the present application can improve the performance of the obtained energy storage devices, and in the NCM811 / graphite battery, the 3C discharge rate at normal temperature is 79.5-85.3%, the 1C discharge rate at-20℃ is 80.2-84.7%, the cycle capacity retention rate of 800 times of 1C charge / 1C discharge at normal temperature is 91.9-96.1%, the cycle capacity retention rate of 800 times of 1C charge / 1C discharge at 45℃ high temperature is 87.8-93.0%, and the safety is high. DETAILED DESCRIPTION

[0043] In order to facilitate the understanding of the present application, the present application lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0044] The reagents and raw materials used in the following examples and comparative examples are commercially available unless otherwise specified. The additives containing siloxyl phosphate ester compounds used are all purchased from Shijiazhuang Shengtai Material Co., Ltd. (purity is greater than 99.8%), and the structures of formula II to formula IV are as follows:

[0045] Formula II; Formula III; Formula IV.

[0046] Examples 1-16 and Comparative Examples 1-3

[0047] Examples 1-16 and Comparative Examples 1-3 all provide an electrolyte, which specifically includes components with mass percentage contents as shown in Table 1.

[0048] Table 1

[0049]

[0050] Wherein, “-” represents that the component is not added, EC represents ethylene carbonate, EMC represents methyl ethylene carbonate, DEC represents diethyl carbonate, PC represents propylene carbonate, PP represents propyl propionate, and EP represents ethyl propionate.

[0051] The electrolytes described in Examples 1-15 and Comparative Examples 1-2 are added to 1.80 Ah lithium ion batteries containing graphite negative material (Songshan P15) and NCM811 nickel-cobalt-manganese ternary material. The performance test standards / methods are as follows:

[0052] (1) Discharge rate performance: 1C current is 1.8 A, and 3C current is 5.4 A; the charge and discharge potential range is 2.75-4.2 V. The discharge rate at room temperature 3C is the ratio of the capacity C2 discharged at 3C constant current to the capacity C1 discharged at 1C constant current.

[0053] (2) Cycle performance: the charge and discharge potential range is 2.75-4.2 V, the charge current is 1C (1.8 A) to 4.2 V, the constant voltage charge to the cutoff current is less than or equal to 0.02C (0.036 A) at 4.2 V, and after standing for 5 min, 1C (1.8 A) is discharged to 2.75 V, and after standing for 5 min; such cycle charging and discharging.

[0054] (3) Low-temperature discharge performance: the 1C (1.8 A) discharge capacity at room temperature 25℃ is recorded as C1, after full charging at 4.2 V, after being frozen at -20℃ for 4 h, the discharge capacity is recorded as C2 at 1C (1.8 A) to 2.75 V. The discharge rate at -20℃ is C2 / C1.

[0055] (4) Safety performance: Hot box test: 10 batteries in full charge state were placed in an explosion-proof box at 130°C for 30 min; puncture test: 5 batteries in full charge state were punctured in the center of the battery with a 3 mm steel needle at a speed of 10 mm / s.

[0056] A lithium ion battery with a capacity of 1.85 Ah was also prepared by adding the electrolyte described in Example 16 and Comparative Example 3 to a negative electrode material of a silicon-carbon negative electrode material (BTR S420) and a positive electrode material of a 4.5V lithium cobalt oxide (LCO) battery. The performance test method / standard is as follows:

[0057] (1) Discharge rate performance: 1C current is 1.85A, and 3C current is 5.55A; the charge and discharge potential range is 2.75-4.50V. The discharge rate at room temperature 3C is the ratio of the capacity C2 discharged at a constant current of 3C to the capacity C1 discharged at a constant current of 1C.

[0058] (2) Cycle performance: The charge and discharge potential range is 2.75-4.50V, the charge current is 1C (1.85A) to 4.50V, and the constant voltage charge is to the cutoff current ≤0.02C (0.037A) at 4.50V, and then 1C (1.85A) discharge to 2.75V after standing for 5 min; such cycle charging and discharging.

[0059] (3) Low temperature discharge performance: The 1C (1.85A) discharge capacity at room temperature 25°C is recorded as C1, and after 4.5V full charge, the battery is frozen at -20°C for 4h, and then discharged to 2.75V at 1C (1.85A), and the discharge capacity is recorded as C2. The discharge rate at -20°C is C2 / C1.

[0060] (4) Safety performance: Hot box test: 10 batteries in full charge state were placed in an explosion-proof box at 130°C for 30 min; puncture test: 5 batteries in full charge state were punctured in the center of the battery with a 3 mm steel needle at a speed of 10 mm / s.

[0061] The test results are shown in Tables 2-4.

[0062] Table 2

[0063]

[0064] Table 3

[0065]

[0066] Table 4

[0067]

[0068] From the test results, it can be seen that:

[0069] (1) As can be seen from Examples 1 to 16, the additive of the siloxyl-containing phosphonate enolate compound having the structure shown in Formula I can be synergized with the additive aid to improve the comprehensive performance of the battery, and the battery has high safety, high-rate discharge rate of 79.5-85.3% at normal temperature, 1C discharge rate of 80.2-84.7% at-20℃, cycle capacity retention rate of 91.9-96.1% for 800 times of 1C charge / 1C discharge at normal temperature, cycle capacity retention rate of 87.8-93.0% for 800 times of 1C charge / 1C discharge at 45℃.

[0070] (2) As can be seen from Examples 1-6, when the mass percentage of the additive of the siloxyl-containing phosphonate enolate compound having the structure shown in Formula I is 0.1-20%, the battery has excellent comprehensive performance, and within the mass percentage range, the high-rate discharge performance, low-temperature discharge performance and cycle performance of the battery increase first and then decrease with the increase of the mass percentage of the additive; further, when the mass percentage of the additive is 1-20%, the battery has better comprehensive performance, indicating that the comprehensive performance of the battery can be further improved by adjusting the mass percentage of the additive of the siloxyl-containing phosphonate enolate compound having the structure shown in Formula I, thereby prolonging the service life of the battery. At the same time, the safety of the battery is gradually enhanced with the increase of the mass percentage of the specific additive, indicating that the use of the additive of the siloxyl-containing phosphonate enolate compound having the structure shown in Formula I can significantly improve the safety of the battery.

[0071] (3) As can be seen from Examples 10-13, the cycle performance, high-rate discharge performance and low-temperature discharge performance of the battery obtained in Example 13 are better than those of Examples 10-12, indicating that the additive aid is further optimized to be a combination of PS and DTD, which can be better matched with the additive of the siloxyl-containing phosphonate enolate compound having the structure shown in Formula I, thereby obtaining a battery with long cycle life, good high-rate discharge performance and low-temperature discharge performance.

[0072] (4) By comparing Example 5 with Comparative Example 1 and Comparative Example 2, it can be seen that if only the additive of the siloxy group-containing phosphonate compound having the structure shown in Formula I (Comparative Example 1) or only the specific additive aid (Comparative Example 2) is added, the cycle life, power characteristics, low-temperature characteristics and safety performance of the obtained battery are significantly poorer than those of the battery obtained by compounding the additive of the siloxy group-containing phosphonate compound having the structure shown in Formula I and the additive aid (Example 5), indicating that by compounding the additive of the siloxy group-containing phosphonate compound having the structure shown in Formula I and the additive aid in the present application, the two can play a synergistic effect, and thus a battery with more excellent comprehensive performance such as cycle life, good power characteristics and low-temperature characteristics, and high safety, etc. can be obtained.

[0073] (5) By comparing Example 16 with Comparative Example 3, it can be seen that the use of the additive of the siloxy group-containing phosphonate compound having the structure shown in Formula I in the present application can not only improve the discharge rate performance, low-temperature discharge performance and cycle performance of the obtained battery, but also significantly improve the safety of the battery, and thus a battery with both long service life and high safety can be obtained.

[0074] In summary, by designing the composition of the electrolyte and compounding the siloxy group-containing phosphonate compound having the structure shown in Formula I as an additive with a specific additive aid, the present application can be well applied to energy storage devices, so that the battery has good discharge rate performance, low-temperature discharge performance and cycle performance, and also has excellent safety performance, and the comprehensive performance is excellent.

[0075] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. An electrolyte solution containing a siliconoxy group-containing phosphonate compound, characterized by, The electrolyte includes an electrolyte, an organic solvent, an additive, and an additive aid, the additive having a siloxy group-containing phosphonate ester compound of Formula I: Formula I; wherein R1, R2, and R3 are the same or different, each independently selected from a substituted or unsubstituted C1-C6 alkyl group; R4 is selected from H, a halogen, a substituted or unsubstituted C1-C4 alkyl group; the substituted substituent group is selected from a fluorine, a C1-C4 alkyl group, or a C1-C4 alkoxy group; the additive aid includes any one or a combination of two of vinylene carbonate, 1,3-propane sultone, or ethylene sulfate.

2. The electrolyte according to claim 1, characterized in that, R1, R2, and R3 are the same or different, each independently selected from any one of -CH3, -CH2CH3, -CF3, or -CH2CF3; R4 is selected from any one of H, -CH3, or -CF3.

3. The electrolyte according to claim 1 or 2, characterized in that, The mass percentage of the additive is 0.1-20%, preferably 1-20%, based on 100% of the mass percentage of the electrolyte.

4. The electrolyte according to any one of claims 1 to 3, characterized in that, The additive aid is a combination of 1,3-propane sultone and ethylene sulfate; Preferably, the mass percentage of the additive aid is 0.5-2%, based on 100% of the mass percentage of the electrolyte.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The electrolyte includes any one or a combination of at least two of XClO4, XPF6, XBF4, XTFSI, XFSI, XBOB, XODFB, XCF3SO3, XAsF6, or XNO3; wherein X is selected from any one of Li, Na, or K; Preferably, the mass percentage of the electrolyte is 8-20%, based on 100% of the mass percentage of the electrolyte.

6. The electrolyte according to any one of claims 1 to 5, characterized in that, The organic solvent includes any one or a combination of at least two of a carbonate, a carboxylate, a fluorinated carboxylate, a fluoroether, or an aromatic hydrocarbon; Preferably, the mass percentage of the organic solvent is 60-91.4%, based on 100% of the mass percentage of the electrolyte.

7. The electrolyte according to claim 6, characterized in that The carbonate includes a halogenated carbonate and / or a non-halogenated carbonate; Preferably, the carboxylate includes a halogenated carboxylate and / or a non-halogenated carboxylate; Preferably, the fluoroether is a fluoroether with a carbon number ≤7; Preferably, the aromatic hydrocarbon includes a halogenated aromatic hydrocarbon and / or a non-halogenated aromatic hydrocarbon.

8. An energy storage device, characterized by, The energy storage device includes the electrolyte of the siloxy group-containing phosphonate ester compound of any one of claims 1-7.

9. The energy storage device of claim 8, wherein, The energy storage device includes a lithium ion battery, a sodium ion battery, a potassium ion battery, or a supercapacitor.

10. The energy storage device of claim 8 or 9, wherein, The negative electrode material of the energy storage device includes any one or a combination of at least two of graphite, soft carbon, hard carbon, a composite of single-crystal silicon and graphite, a composite of silicon monoxide and graphite, lithium titanate, or di-niobium pentoxide.

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