Electrolyte additive composition and application thereof

Abstract

According to the electrolyte additive composition and the application thereof, the first compound, the second compound and the third compound are introduced into the electrolyte additive composition in a matched mode, the out-of-control risk of a lithium ion battery can be reduced, and the electrochemical performance of the electrolyte additive composition at the normal temperature is basically the same as that of a traditional liquid lithium ion battery. When the electrolyte additive composition is out of control, the electrolyte additive composition is quickly converted from a crystalline state to an amorphous state at a high temperature, and polymer chain segments are quickly wound based on hydrogen bond interaction between polymer chains to form a polymer network skeleton structure, so that positive and negative electrode short circuits can be isolated. In the process, a polymer network skeleton structure formed by the electrolyte additive composition has the characteristics of high strength, high toughness, high melting point and high oxygen index, and can be rapidly coordinated with lithium ions through rich heteroatom sites on the skeleton to effectively inhibit the movement of the lithium ions in an electric field, so that the electric energy of a battery cell is released in a short time.

Description

Technical Field

[0001] The present invention belongs to the field of lithium - ion batteries, and particularly relates to an electrolyte additive composition and its application. Background Art

[0002] With the transformation of the world's energy structure, the proportion of new energy is increasing, and lithium - ion batteries play an indispensable role in the future energy structure. However, the current mainstream liquid lithium - ion batteries face a series of safety risk problems. Especially in some extreme scenarios, lithium - ion batteries are very likely to have safety accidents such as fire and explosion. In response to the above problems, major manufacturers in the industry have taken safety measures such as thermal insulation materials, BMS intelligent risk control, battery protection structures, and introducing electrolyte additives to reduce the risk of battery runaway.

[0003] Thermal insulation materials enhance battery safety by slowing down the diffusion and transfer of heat and flame within the battery pack. However, introducing thermal insulation materials will increase the volume of the battery, thereby reducing the energy density of the battery. More importantly, thermal insulation materials cannot completely prevent thermal runaway events from occurring; they can only slow down the propagation speed of thermal runaway.

[0004] The BMS can monitor the status of the battery in real - time, including parameters such as voltage, current, and temperature, to ensure the best performance and safety of the battery under various operating conditions, prevent over - charging, over - discharging, over - temperature, etc. of the battery, and thus effectively protect the safety of the battery system. However, both the hardware and software parts of the BMS system require investment costs. Especially in large - scale applications, the wires may be too long, increasing the cost.

[0005] The battery protection structure can quickly cut off or increase its own resistance when the lithium - ion battery is short - circuited, so as to reduce the current after the short - circuit, thereby suppressing the rise in the temperature of the lithium - ion battery and avoiding the further deterioration of the short - circuit consequences. The battery protection structure may increase the weight of the battery, thereby reducing the energy density of the battery.

[0006] The currently used electrolyte additives form a stable SEI film through the chemical composition and interfacial properties of the negative - electrode SEI film, thereby improving the cycle life and safety of the battery. However, the electrolyte additives or the by - products formed after their participation in the electrochemical reaction may have adverse reactions with other components in the battery, resulting in a decline in the electrochemical performance of the lithium - ion battery. Summary of the Invention

[0007] In order to reduce the risk of lithium - ion battery runaway and, at the same time, keep the electrochemical performance of the lithium - ion battery at a good level, the present application provides an electrolyte additive composition and its application.

[0008] According to one aspect of the present invention, there is provided an electrolyte additive composition, which includes a first compound, a second compound, and a third compound; the chemical structural formula of the first compound is shown in Formula (I) or Formula (II); the chemical structural formula of the second compound is shown in Formula (III) or Formula (IV); the chemical structural formula of the third compound is shown in Formula (V);

[0009]

[0010] Wherein: m1, m2, m3, m4, m5 are integers from 1 to 1000; n1, n2, n3, n4, n5, n6, n7 are integers from 0 to 10, and at least one of n2, n3, n4, n5, n6, n7 is a non-zero integer; r1, r2, r3, r4 are each independently selected from a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aromatic ring; r5, r6, r7, r8 are each independently selected from a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted ester group, or a substituted or unsubstituted aromatic ring; Z1, Z2, Z3, Z4, Z5, Z6 are each independently selected from a carbon atom or a nitrogen atom; Y is shown in Formula (VI); X1, X2 are each independently selected from a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aromatic ring; R1, R2, R3 are each independently selected from a hydrogen atom or a carbonyl group; R4, R5, R6 are each independently selected from an isocyanate group or a substituted or unsubstituted alkyl group; R7, R8, R9, R10, R11, R12 are each independently selected from a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aromatic ring; R13 is selected from a substituted or unsubstituted aryl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted furyl group, a substituted or unsubstituted tetrahydrofuryl group, or a substituted or unsubstituted pyranyl group; R14 is selected from a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group.

[0011] The electrolyte additive composition provided by the present application can reduce the out-of-control risk of lithium-ion batteries by introducing the first compound, the second compound, and the third compound in combination. At the same time, its electrochemical performance at room temperature is basically no different from that of traditional liquid lithium-ion batteries. This is because the electrolyte additive composition provided by the present application does not react inside the battery cell at room temperature, so it has little impact on the room-temperature electrical performance of the battery. When facing out-of-control situations (such as electrical abuse, thermal abuse, and mechanical abuse scenarios), on the one hand, the electrolyte additive composition rapidly transforms from a crystalline state to an amorphous state at high temperature, and based on the hydrogen bond interaction between polymer chains, the polymer chain segments quickly entangle with each other to form a polymer network skeleton structure, which can isolate the short circuit between the positive and negative electrodes; on the other hand, in the above process, the polymer network skeleton structure formed by the electrolyte additive composition has the characteristics of high strength, high toughness, high melting point, and high oxygen index, and can quickly coordinate with lithium ions through the abundant heteroatom sites on the skeleton, effectively inhibiting the movement of lithium ions under the electric field, thereby realizing the release of the electrical energy of the battery cell in a short time. Thus, by combining the first compound, the second compound, and the third compound, the present application can achieve the goal of protecting the safety of the battery cell, blocking the occurrence of thermal runaway in the battery, and thus enhancing the safety of lithium-ion batteries.

[0012] Preferably, for the above-mentioned substituted alkyl or unsubstituted alkyl, the carbon chain length is 1 to 10.

[0013] Preferably, for the above-mentioned substituted alkoxy or unsubstituted alkoxy, the carbon chain length is 1 to 10.

[0014] Preferably, for the above-mentioned substituted aryl or unsubstituted aryl, the carbon chain length is 6 to 26.

[0015] Preferably, for the above-mentioned substituted benzyl or unsubstituted benzyl, the carbon chain length is 7 to 27.

[0016] Preferably, the substituted alkyl is an alkyl substituted by a substituent of halogen one or more times.

[0017] Preferably, the substituted alkoxy is an alkoxy substituted by a substituent of halogen one or more times.

[0018] Preferably, the substituted aryl is an aryl substituted by a substituent of substitution group A one or more times.

[0019] Preferably, the substituted benzyl is a benzyl substituted by a substituent of substitution group A one or more times.

[0020] Preferably, substitution group A is at least one of alkyl, alkoxy, hydroxyl, cyano, and halogen.

[0021] Preferably, the substituted tetrahydrofuranyl is a tetrahydrofuranyl substituted by alkyl or alkoxy one or more times.

[0022] Preferably, the substituted pyranyl group is a pyranyl group substituted by an alkyl group or an alkoxy group one or more times.

[0023] Preferably, in the electrolyte additive composition, calculated by mass percentage, the mass content of the third compound is higher than 10%.

[0024] Preferably, in the electrolyte additive composition, calculated by mass ratio, the first compound: the second compound: the third compound = 1 - 35: 1 - 65: 1 - 85.

[0025] Preferably, the first compound includes at least one of polyethylene glycol, methoxypolyethylene glycol, dimethoxypolyethylene glycol, diethoxypolyethylene glycol, diphenyl ether polyethylene glycol, poly(1,3 - dioxane), polytetrahydrofuran, three - arm polyethylene glycol, four - arm polyethylene glycol, and monooleate polyethylene glycol.

[0026] Preferably, the second compound includes at least one of polyethylene glycol succinate, diethyl polyethylene glycol, polycaprolactone, polybutyrolactone, polystearolactone, polyethylene terephthalate, poly(β - lactide), poly(methoxypolyethylene glycol monomethacrylate), and polytrimethylene carbonate. In industrial production of the above ester compounds, by regulating the ratio of polybasic acid and polyhydric alcohol, one component is preferentially depleted, and then a small - molecule acid or alcohol is added to block the residual active groups, and unreacted monomers and oligomer impurities are removed by purification. Generally, the two ends of the product structural formula usually contain active hydrogen, but when actually using the above ester compounds, the active hydrogen needs to be removed according to the actual application to avoid interfering with the reaction. Therefore, in the structural formula, whether it has active hydrogen does not affect the selection of this material by those skilled in the art.

[0027] Preferably, the third compound includes at least one of dicyclohexylmethane diisocyanate - isophthalic dihydrazide - hexamethylene diisocyanate trimer copolymer, dicyclohexylmethane diisocyanate - succinic dihydrazide - hexamethylene diisocyanate trimer copolymer, and dicyclohexylmethane diisocyanate - adipic dihydrazide - hexamethylene diisocyanate trimer copolymer.

[0028] Preferably, calculated by mass percentage, the raw materials for preparing the polyamide - urea copolymer include 5 - 20% dicyclohexylmethane diisocyanate, 5 - 15% hexamethylene diisocyanate trimer, and 65 - 85% hydrazide compounds.

[0029] Preferably, the preparation method of the third compound is as follows: dicyclohexylmethane diisocyanate, hexamethylene diisocyanate trimer, hydrazide compound, and organotin catalyst are mixed in an organic solvent for 30 minutes to 60 minutes, and then the temperature is raised to 60-100 °C, and the reaction is carried out for 3-24 hours in an anhydrous and oxygen-free environment to obtain a first reaction solution; the first reaction solution is mixed with a precipitant, and then the crude product is obtained by centrifugation, and the crude product is successively subjected to a washing treatment and a drying treatment to obtain a polyamide-urea copolymer.

[0030] Preferably, the hydrazide compound includes at least one of isophthalic dihydrazide, succinic dihydrazide, and adipic dihydrazide.

[0031] Preferably, the addition amount of the organotin catalyst is 0.5-10 wt% of the sum of the addition amounts of dicyclohexylmethane diisocyanate, hexamethylene diisocyanate trimer, and hydrazide compound

[0032] Preferably, the organic solvent includes at least one of toluene, xylene, chloroform, and ethyl acetate.

[0033] Preferably, the organotin catalyst includes dibutyltin dilaurate.

[0034] Preferably, the washing treatment is to wash the crude product with a washing solvent, and the washing solvent includes at least one of ethyl acetate and ethanol.

[0035] Preferably, the drying treatment is carried out under vacuum at 30-90 °C for 12-48 hours.

[0036] Preferably, the molecular weight of the first compound is 500-4000.

[0037] Preferably, the molecular weight of the second compound is 400-10000.

[0038] Preferably, the molecular weight of the third compound is 400-2000.

[0039] In the second aspect of the present application, an electrolyte is provided, which includes the above electrolyte additive composition, and the mass content of the electrolyte additive composition in the electrolyte is 5-30%.

[0040] Preferably, calculated by mass percentage, the electrolyte further includes 50-84% organic solvent and 10-17% lithium salt.

[0041] Preferably, the organic solvent includes at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene carbonate, vinylene carbonate, methyl formate, ethyl formate, ethyl acetate, and methyl propionate.

[0042] Preferably, at least one of lithium nitrate, lithium hexafluorophosphate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(acetato)borate, lithium tetrafluoroborate, and lithium difluorophosphate.

[0043] Preferably, the electrolyte further includes a film-forming additive, and the film-forming additive includes at least one of vinylene carbonate, fluoroethylene carbonate, triethyl phosphite, 1,3-propane sultone, ethylene sulfite, 1,3,2-dioxathiolane 2,2-dioxide, 1,4-butane sultone, phenyl methanesulfonate, adiponitrile, 3-methoxypropionitrile, hexane-1,3,6-tricarbonitrile, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, and trimethylsilyldiethylamine. Further, introducing the film-forming additive helps to form a stable SEI / CEI film, reduce interfacial side reactions, and improve cycling performance, rate performance, charge-discharge performance, and voltage window; or it can consume a small amount of water and free hydrofluoric acid in the electrolyte to improve the safety and stability of the battery cell.

[0044] Preferably, the mass content of the film-forming additive in the electrolyte is 1-6%.

[0045] Preferably, the method for preparing the electrolyte includes the following steps: mixing the raw materials for preparing the electrolyte under a protective gas atmosphere or a dry air atmosphere to obtain the electrolyte.

[0046] Preferably, in the mixing process, the mixing temperature is 0-25°C.

[0047] Preferably, in the mixing process, the mixing time is 0.5-6 hours.

[0048] In the third aspect of the present application, a lithium-ion battery is provided, which includes the above electrolyte additive composition or the above electrolyte.

[0049] Preferably, the electrolyte is injected into the battery cell, and after encapsulation, standing, formation, shaping, and grading, a battery cell containing the electrolyte is obtained.

[0050] Preferably, the encapsulation includes a vacuum encapsulation process, wherein the vacuum degree of the vacuum encapsulation process is 70-120 KPa.

[0051] Preferably, the treatment conditions for standing are: the standing temperature is 25-30°C; and / or, the standing time is 24-70 hours. Detailed Embodiments

[0052] To enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0053] Example 1

[0054] 1. Electrolyte additive composition

[0055] The formula of the electrolyte additive composition provided in this example is shown in Table 1.

[0056] Table 1. Composition of the electrolyte additive composition provided in Example 1

[0057]

[0058]

[0059] Among them, the chemical formula of polyethylene glycol dimethyl ether is The chemical formula of polycaprolactone is The chemical formula of the copolymer of dicyclohexylmethane diisocyanate - succinic dihydrazide - hexamethylene diisocyanate trimer is shown in Formula (VII).

[0060]

[0061] 2. Electrolyte

[0062] The formula of the electrolyte provided in this example is shown in Table 2.

[0063] The steps for preparing the electrolyte are as follows: The above-provided electrolyte additive composition, organic solvent, and lithium salt are mixed according to the formula in Table 2 under a dry air atmosphere, where the mixing temperature is 10°C and the mixing time is 4 hours to obtain the electrolyte. In the organic solvent, calculated by mass ratio, EC:EMC:DEC = 24:70:6.

[0064] Table 2. Composition of the electrolyte provided in Example 1

[0065]

[0066] 3. Lithium-ion battery

[0067] Using NCM811 as the positive electrode, graphite as the negative electrode, and Celgard membrane as the separator, and then injecting the above electrolyte into the battery cell. After encapsulation, standing, formation, shaping, and grading, a lithium-ion battery containing the electrolyte is obtained. Among them, the encapsulation is vacuum encapsulation treatment with a vacuum degree of 100 KPa; the standing temperature is 25 °C and the standing time is 30 hours.

[0068] Example 2

[0069] This example refers to the formula and method provided in Example 1 to prepare the electrolyte additive composition, electrolyte, and lithium-ion battery. The difference from Example 1 is that when preparing the electrolyte additive composition in this example, calculated by mass ratio, the first compound: the second compound: the third compound = 5:5:90 (the total mass fraction remains unchanged). Except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium-ion battery in this example are strictly the same as those in Example 1.

[0070] Example 3

[0071] This example refers to the formula and method provided in Example 1 to prepare the electrolyte additive composition, electrolyte, and lithium-ion battery. The difference from Example 1 is that when preparing the electrolyte additive composition in this example, calculated by mass ratio, the first compound: the second compound: the third compound = 5:10:85 (the total mass fraction remains unchanged). Except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium-ion battery in this example are strictly the same as those in Example 1.

[0072] Example 4

[0073] This example refers to the formula and method provided in Example 1 to prepare the electrolyte additive composition, electrolyte, and lithium-ion battery. The difference from Example 1 is that when preparing the electrolyte additive composition in this example, calculated by mass ratio, the first compound: the second compound: the third compound = 35:64:1 (the total mass fraction remains unchanged). Except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium-ion battery in this example are strictly the same as those in Example 1.

[0074] Example 5

[0075] This example prepares an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formula and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte additive composition, calculated by mass ratio, the first compound: the second compound: the third compound = 35:64.5:0.5 (the total mass fraction remains unchanged). Except for the above differences, the operating steps for preparing the electrolyte additive composition, the electrolyte, and the lithium-ion battery in this example are strictly the same as those in Example 1.

[0076] Example 6

[0077] This example prepares an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formula and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte additive composition, calculated by mass ratio, the first compound: the second compound: the third compound = 30:0.5:69.5 (the total mass fraction remains unchanged). Except for the above differences, the operating steps for preparing the electrolyte additive composition, the electrolyte, and the lithium-ion battery in this example are strictly the same as those in Example 1.

[0078] Example 7

[0079] This example prepares an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formula and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte additive composition, the specific material used for the first compound is polyethylene glycol diethyl ether, and its chemical formula is The specific material used for the second compound is polyethylene terephthalate, and its chemical formula is The specific material used for the third compound is a copolymer of dicyclohexylmethane diisocyanate - adipic dihydrazide - hexamethylene diisocyanate trimer, and its chemical formula is shown in Formula (VIII). Except for the above differences, the operating steps for preparing the electrolyte additive composition, the electrolyte, and the lithium-ion battery in this example are strictly the same as those in Example 1.

[0080]

[0081] Example 8

[0082] This example prepares an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formula and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte additive composition, the specific material used for the first compound is four-arm polyethylene glycol ethyl ether, and its chemical formula is The specific material used for the second compound is poly(methoxypolyethylene glycol monomethacrylate), and its chemical formula is The specific material used for the third compound is a copolymer of dicyclohexylmethane diisocyanate - isophthalic dihydrazide - hexamethylene diisocyanate trimer, and its chemical formula is as shown in Formula (IX). Except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium - ion battery in this example are exactly the same as those in Example 1.

[0083]

[0084] Example 9

[0085] In this example, an electrolyte additive composition, electrolyte, and lithium - ion battery are prepared with reference to the formula and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte additive composition in this example, the specific material used for the first compound is polyethylene glycol diethyl ether; except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium - ion battery in this example are exactly the same as those in Example 1.

[0086] Example 10

[0087] In this example, an electrolyte additive composition, electrolyte, and lithium - ion battery are prepared with reference to the formula and method provided in Example 1. The differences from Example 1 are that when preparing the electrolyte additive composition in this example, the specific material used for the first compound is polyethylene glycol diethyl ether (Example 1); the specific material used for the second compound is polyethylene terephthalate (Example 7); except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium - ion battery in this example are exactly the same as those in Example 1.

[0088] Example 11

[0089] In this example, an electrolyte additive composition, electrolyte, and lithium - ion battery are prepared with reference to the formula and method provided in Example 1. The differences from Example 1 are that when preparing the electrolyte additive composition in this example, the specific material used for the first compound is polyethylene glycol diethyl ether (Example 1); the specific material used for the second compound is polyethylene terephthalate (Example 7); the specific material used for the third compound is a copolymer of dicyclohexylmethane diisocyanate - isophthalic dihydrazide - hexamethylene diisocyanate trimer (Example 8), and its chemical formula is as shown in Formula (VIII); except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium - ion battery in this example are exactly the same as those in Example 1.

[0090] Example 12

[0091] This example prepares an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formulation and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte, a film-forming additive is introduced. The electrolyte formulation provided in this example is shown in Table 3. Except for the above differences, the operating steps for preparing the electrolyte additive composition, electrolyte, and lithium-ion battery in this example are strictly the same as those in Example 1. Among them, in the organic solvent, calculated by mass ratio, EC:EMC:DEC = 24:70:6.

[0092] Table 3. Composition of the electrolyte provided in Example 12

[0093]

[0094] Comparative Example 1

[0095] This comparative example prepares an electrolyte and a lithium-ion battery with reference to the formulation and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte, a first compound with an equal mass percentage content (specific material is polyethylene glycol dimethyl ether, chemical formula: ) is used to replace the electrolyte additive composition. Except for the above differences, the operating steps for preparing the electrolyte and lithium-ion battery in this comparative example are strictly the same as those in Example 1.

[0096] Comparative Example 2

[0097] This comparative example prepares an electrolyte and a lithium-ion battery with reference to the formulation and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte, a second compound with an equal mass percentage content (specific material is polycaprolactone, chemical formula: ) is used to replace the electrolyte additive composition. Except for the above differences, the operating steps for preparing the electrolyte and lithium-ion battery in this comparative example are strictly the same as those in Example 1.

[0098] Comparative Example 3

[0099] This comparative example prepares an electrolyte and a lithium-ion battery with reference to the formulation and method provided in Example 1. The difference from Example 1 is that when preparing the electrolyte, a third compound with an equal mass percentage content (specific material is dicyclohexylmethane diisocyanate - succinic dihydrazide - hexamethylene diisocyanate trimer copolymer, whose chemical formula is shown in Formula (VII)) is used to replace the electrolyte additive composition. Except for the above differences, the operating steps for preparing the electrolyte and lithium-ion battery in this comparative example are strictly the same as those in Example 1.

[0100] Comparative Example 4

[0101] This comparative example prepared an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formula and method provided in Example 1. The difference from Example 1 is that the first compound was not added during the preparation of the electrolyte additive composition. Except for the above difference, the operating steps for preparing the electrolyte additive composition, the electrolyte, and the lithium-ion battery in this comparative example were strictly the same as those in Example 1.

[0102] Comparative Example 5

[0103] This comparative example prepared an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formula and method provided in Example 1. The difference from Example 1 is that the second compound was not added during the preparation of the electrolyte additive composition. Except for the above difference, the operating steps for preparing the electrolyte additive composition, the electrolyte, and the lithium-ion battery in this comparative example were strictly the same as those in Example 1.

[0104] Comparative Example 6

[0105] This comparative example prepared an electrolyte additive composition, an electrolyte, and a lithium-ion battery with reference to the formula and method provided in Example 1. The difference from Example 1 is that the third compound was not added during the preparation of the electrolyte additive composition. Except for the above difference, the operating steps for preparing the electrolyte additive composition, the electrolyte, and the lithium-ion battery in this comparative example were strictly the same as those in Example 1.

[0106] Test Example

[0107] 1. Test Object

[0108] The lithium-ion batteries prepared in Examples 1 to 12 and Comparative Examples 1 to 6.

[0109] 2. Test Method

[0110] (1) Cycling test: At room temperature, the battery cells were subjected to a 1C / 1C cycling test until the capacity retention rate reached 80%, and the number of cycles was recorded.

[0111] (2) Penetration test: Fifty parallel samples were taken. At room temperature, a 3-mm steel needle was used to penetrate the battery cells with 100% SOC at a speed of 40 mm / s. The passing standard for the test was no fire and no explosion, and the test result was expressed as the number of passing samples / the number of tested samples. That is, 50 / 50 means that among the 50 parallel samples, 20 parallel samples all passed the test; 0 / 50 means that among the 50 parallel samples, 0 parallel samples all passed the test. The same applies hereinafter and will not be elaborated.

[0112] (3) Thermal abuse test: Take 50 parallel samples. For the battery cells with 100% SOC, conduct a thermal abuse test at 130 °C. Start from room temperature and heat at a rate of 5 °C / min. After reaching 130 °C, keep the temperature constant for 30 min and then stop. The passing standard for the test is no fire and no explosion. The test result is expressed as the number of passing samples / the number of tested samples.

[0113] (4) Extrusion test: Take 50 parallel samples. For the battery cells with 100% SOC, conduct an extrusion test at a rate of 0.1 mm / s. Stop the test immediately after the pressure reaches 13 KN. The passing standard is no fire and no explosion. The test result is expressed as the number of passing samples / the number of tested samples.

[0114] 3. Test results and analysis

[0115] By comparing the data of Examples 1 to 12 and Comparative Examples 1 to 6, it can be confirmed that by simultaneously introducing the first compound, the second compound, and the third compound, the present application can significantly reduce the risk of battery out-of-control without affecting the electrochemical performance of the battery.

[0116] Specifically, when the temperature inside the battery cell rises and reaches a certain temperature, the above three compounds can quickly transform from the crystalline state to the amorphous state. There are hydrogen bond interactions between the oxygen atoms in the first compound, the ester groups in the second compound, and the amide groups and urea groups in the third compound. In the amorphous state, the segments between the three compounds are intertwined with each other through hydrogen bond interactions to form an interpenetrating and tough polymer network structure. Moreover, there are a large number of heteroatoms (such as N, O) in this polymer network structure. In the amorphous state, the sites of these heteroatoms are largely exposed and can coordinate with Li + to restrict the movement of Li + and thus reduce the rate of electrical energy release when the battery cell fails. In addition, when facing the scenario of mechanical abuse, the tough polymer network structure can effectively reduce the contact area between the positive and negative electrode plates, thereby reducing the short-circuit points and the energy release rate, playing a role in preventing thermal runaway.

[0117] Furthermore, by comparing the data of Examples 1 to 6, it can be found that the stability of the battery will change with the mass ratio of the above three compounds and will fluctuate with the content of the third compound in the electrolyte additive composition.

[0118] It can be found in Examples 1, 7 to 11 that the material combination between the first compound, the second compound, and the third compound can improve the cycle performance of the battery. At the same time, in Example 12, by adding a film-forming additive to the electrolyte, the cycle performance of the battery can be further enhanced.

[0119] Table 4. Test results of this test case

[0120] Group Cyclic Test Pin Prick Test Thermal Abuse Test Crush Test Example 1 386 50 / 50 50 / 50 50 / 50 Example 2 377 35 / 50 34 / 50 36 / 50 Example 3 368 37 / 50 40 / 50 39 / 50 Example 4 372 33 / 50 30 / 50 38 / 50 Example 5 371 30 / 50 32 / 50 33 / 50 Example 6 381 33 / 50 29 / 50 34 / 50 Example 7 440 50 / 50 50 / 50 50 / 50 Example 8 463 50 / 50 50 / 50 50 / 50 Example 9 350 50 / 50 50 / 50 50 / 50 Example 10 336 50 / 50 50 / 50 50 / 50 Example 11 328 50 / 50 50 / 50 50 / 50 Example 12 550 50 / 50 50 / 50 50 / 50 Comparative Example 1 270 5 / 50 7 / 50 11 / 50 Comparative Example 2 354 10 / 50 8 / 50 13 / 50 Comparative Example 3 384 13 / 50 15 / 50 15 / 50 Comparative Example 4 343 20 / 50 20 / 50 19 / 50 Comparative Example 5 336 22 / 50 23 / 50 20 / 50 Comparative Example 6 298 19 / 50 23 / 50 26 / 50

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention rather than limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An electrolyte additive composition, characterized in that, The electrolyte additive composition includes a first compound, a second compound, and a third compound; The chemical structural formula of the first compound is shown as Formula (I) or Formula (II); the chemical structural formula of the second compound is shown as Formula (III) or Formula (IV); the chemical structural formula of the third compound is shown as Formula (V); Wherein: m1, m2, m3, m4, m5 are integers from 1 to 1000; n1, n2, n3, n4, n5, n6, n7 are integers from 0 to 10, and among n2, n3, n4, n5, n6, n7, at least one is a non-zero integer; r1, r2, r3, r4 are each independently selected from a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aromatic ring; r5, r6, r7, r8 are each independently selected from a hydrogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted ester group, or a substituted or unsubstituted aromatic ring; Z1, Z2, Z3, Z4, Z5, Z6 are each independently selected from a carbon atom or a nitrogen atom; Y is shown as Formula (VI); X1, X2 are each independently selected from a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aromatic ring; R1, R2, R3 are each independently selected from a hydrogen atom or a carbonyl group; R4, R5, R6 are each independently selected from an isocyanate group or a substituted or unsubstituted alkyl group; R7, R8, R9, R10, R11, R12 are each independently selected from a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aromatic ring; R13 is selected from a substituted or unsubstituted aryl group, a substituted or unsubstituted benzyl group, a substituted or unsubstituted furyl group, a substituted or unsubstituted tetrahydrofuryl group, or a substituted or unsubstituted pyranyl group; R14 is selected from a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group.

2. The electrolyte additive composition according to claim 1, characterized in that, In the electrolyte additive composition, calculated by mass percentage, the mass content of the third compound is higher than 10%.

3. The electrolyte additive composition according to claim 1 or 2, characterized in that, The first compound includes at least one of polyethylene glycol, methoxypolyethylene glycol, dimethoxypolyethylene glycol, diethoxypolyethylene glycol, diphenyl ether polyethylene glycol, poly(1,3-dioxane), polytetrahydrofuran, three-arm polyethylene glycol, four-arm polyethylene glycol, and polyethylene glycol monooleyl ether.

4. The electrolyte additive composition according to claim 1 or 2, characterized in that, The second compound includes at least one of polyethylene glycol succinate, diethyl polyethylene glycol succinate, polycaprolactone, polybutyrolactone, polyoctadecalactone, polyethylene terephthalate, poly(β-lactide), poly(methoxypolyethylene glycol monomethacrylate), and polytrimethylene carbonate.

5. The electrolyte additive composition according to claim 1 or 2, characterized in that, The third compound includes at least one of dicyclohexylmethane diisocyanate - isophthalic dihydrazide - hexamethylene diisocyanate trimer copolymer, dicyclohexylmethane diisocyanate - succinic dihydrazide - hexamethylene diisocyanate trimer copolymer, and dicyclohexylmethane diisocyanate - adipic dihydrazide - hexamethylene diisocyanate trimer copolymer.

6. An electrolyte, characterized in that, The electrolyte includes the electrolyte additive composition as described in any one of claims 1 to 5, and the mass content of the electrolyte additive composition in the electrolyte is 5 to 30%.

7. The electrolyte according to claim 6, wherein, Calculated by mass percentage, the electrolyte further includes 50 to 84% organic solvent and 10 to 17% lithium salt.

8. The electrolyte according to claim 6 or 7, characterized in that, The electrolyte further includes a film-forming additive, and the film-forming additive includes at least one of vinylene carbonate, fluoroethylene carbonate, triethyl phosphite, 1,3-propane sultone, ethylene sulfite, 1,3,2-dioxathiolane-2,2-dioxide, 1,4-butane sultone, phenyl methanesulfonate, adiponitrile, 3-methoxypropionitrile, hexane-1,3,6-tricarbonitrile, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, and trimethylsilyldiethylamine.

9. The electrolyte according to claim 8, wherein, The mass content of the film-forming additive in the electrolyte is 1 to 6%.

10. A lithium-ion battery, characterized in that, The lithium ion battery includes the electrolyte additive composition as described in any one of claims 1 to 5, or the electrolyte as described in any one of claims 6 to 9.

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