Ternary lithium ion battery electrolyte and application thereof
By introducing additives with specific functional groups to the molecular structure of 1,3-propane sulfonate lactone, the problem of poor storage performance of ternary lithium-ion batteries at high and low temperatures is solved, and the battery maintains good performance in a wide temperature zone is achieved.
Patent Information
- Application Number
- CN202311748961.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-19
- Publication Date
- 2025-06-20
AI Technical Summary
The storage performance of ternary lithium-ion batteries at high and low temperatures is poor, and there are fewer types of additives that take into account high and low temperature performance, which limits their application in the field of new energy vehicles.
By introducing -CH3,-CH3O,-COOH,-CF3,-F and its isomers into the molecular structure of 1,3-propane sulfonate lactone, an additive is prepared that forms different film components at the positive and negative electrode interface, reduces the negative electrode interface impedance and inhibits the side reaction of the electrode/electrolyte interface at high temperatures.
It significantly improves the battery's high-temperature storage performance and improves Li+ transmission at low temperatures, achieving good performance of the battery over a wide temperature range.
Smart Images
Figure BDA0004616497040000021 
Figure BDA0004616497040000031 
Figure BDA0004616497040000103
Abstract
Description
Technical Field
[0001] The present application relates to a ternary lithium-ion battery electrolyte and its application, belonging to the field of lithium-ion batteries. Background Art
[0002] Energy is the material basis for human survival and economic development. Building a safe, efficient, clean, economical and stable energy system is critical to the sustainable development of society. The development of new energy vehicles can not only effectively respond to the challenges of energy crisis and environmental pollution, achieve sustainable development of the automobile industry, but also achieve leapfrog development of China's automobile industry. Pure electric vehicles and hybrid vehicles are important directions for the development of the future automobile industry, and power batteries are the key core technology of new energy vehicles. As the industrialization process of electric vehicles gradually deepens, governments and enterprises of various countries have stepped up efforts to develop the power battery industry. When used in power batteries, compared with lead-acid batteries, nickel-cadmium batteries and nickel-hydrogen batteries, lithium-ion batteries have the advantages of high energy density, long cycle life, good consistency and good safety. Considering the overall performance, cost, industrial maturity and other aspects, lithium-ion power batteries are the best choice for new energy vehicles at this stage and have become the most widely used power batteries for new energy vehicles. Compared with lithium cobalt oxide, lithium iron phosphate and lithium manganese oxide batteries, ternary batteries have high energy density (single energy density is 150~200Wh·kg -1 , the energy density of high nickel ternary lithium battery can reach 300Wh·kg -1 Above), high voltage platform (3.6-3.7V), high tap density (the tap density of ternary materials is about 2.0-2.4g·cm -3 ), good cycle performance (1500-2000 times), electrochemical stability and other characteristics, have obvious advantages in improving the range of new energy vehicles. However, ternary batteries have poor high-temperature storage performance and average low-temperature performance. Comprehensively improving the wide-temperature performance of ternary batteries is crucial to promoting their application in the field of new energy vehicles.
[0003] The electrolyte determines the high and low temperature, high rate, cycle and safety performance of the battery, and is the key to the development of wide temperature range lithium-ion batteries. When the operating temperature is too low, the conductivity of the electrolyte will be greatly reduced, and the Li + As the solvation effect is enhanced, the impedance of the SEI film increases, and the solvent and lithium salt will precipitate; when the temperature is high, various complex side reactions will occur in the electrolyte itself and between the electrode and the electrolyte. It is a more effective method to improve the high and low temperature performance of ternary batteries by adjusting the electrolyte formula. However, most solvents or additives can only improve the low temperature performance or high temperature performance of the battery alone. Electrolytes that take into account both high and low temperature performance are the key to breaking through the wide temperature range lithium-ion battery technology. At present, there are few types of additives that take into account both high and low temperature performance, which deserves further study. Summary of the invention
[0004] The purpose of this application is to provide an additive to improve the wide-temperature performance of ternary lithium-ion batteries. Such additives introduce -CH3, -CH3O, -COOH, -CF3, -F and their isomers into the molecular structure of 1,3-propane sultone. These functional groups affect the different components of the interfacial film formed on the positive and negative electrodes by the additive, mainly affecting the contents of organic sulfides, inorganic sulfides and fluorides. The interfacial impedance of the negative electrode is reduced, which is beneficial to the transport of Li+ at low temperatures. At the same time, there are more inorganic sulfides in the CEI film formed on the positive electrode, which can inhibit the side reactions at the electrode / electrolyte interface at high temperatures, thereby significantly improving the high-temperature storage performance of the battery. Ultimately, the battery has good high and low temperature performance.
[0005] One aspect of this application provides an electrolyte for a ternary lithium-ion battery to improve the high and low temperature performance of the ternary battery.
[0006] Optionally, the composition of the electrolyte for the ternary lithium-ion battery includes:
[0007] Lithium salt, ester solvent and additive;
[0008] The additive includes additive I and additive II;
[0009] The additive I has the structure shown in formula I;
[0010]
[0011] Among them, R is selected from at least one of -CH3, -CH3O, -COOH, -CF3, -F.
[0012] Optionally, the additive I is selected from at least one of the structures shown in a to p;
[0013]
[0014] Optionally, the additive II is selected from at least one of vinylene carbonate (VC), ethylene vinylene carbonate, lithium difluorophosphate, fluorinated ethylene carbonate, and tripropynyl phosphate.
[0015] Optionally, in the electrolyte for the ternary lithium-ion battery, the mass fraction of the additive I is 0.5% to 5%.
[0016] Optionally, in the electrolyte for the ternary lithium-ion battery, the mass fraction of the additive I is 0.5% to 2%.
[0017] Optionally, the mass fraction of the additive I is independently selected from any value of 0.5%, 1%, 2%, 3%, 4%, 5% or the range value between any two of the above.
[0018] Optionally, in the ternary lithium-ion battery electrolyte, the mass fraction of the additive II is 0.1% to 5%.
[0019] Optionally, in the ternary lithium-ion battery electrolyte, the mass fraction of the additive II is 0.5% to 2%.
[0020] Optionally, the mass fraction of the additive II is independently selected from any value of 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or the range value between any two of the above.
[0021] Optionally, the lithium salt package is selected from at least one of LiPF6, LiBF4, LiClO4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI.
[0022] Optionally, the lithium salt is LiPF6.
[0023] Optionally, in the ternary lithium-ion battery electrolyte, the concentration of the lithium salt is 0.8 mol / L to 3 mol / L.
[0024] Optionally, in the ternary lithium-ion battery electrolyte, the concentration of the lithium salt is 1 to 2 mol / L.
[0025] Optionally, the concentration of the lithium salt is independently selected from any value of 0.8 mol / L, 1 mol / L, 2 mol / L, 3 mol / L or the range value between any two of the above.
[0026] Optionally, the ester solvent is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate.
[0027] Optionally, the ester solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.
[0028] In another aspect of the present application, there is provided the use of the above ternary lithium-ion battery electrolyte in a ternary lithium-ion battery, and the temperature range of the use is -40°C to 80°C.
[0029] The beneficial effects that the present application can produce include:
[0030] By introducing -CH3, -CH3O, -COOH, -CF3, -F and their isomers into the molecular structure of 1,3 - propane sultone, the components of the interfacial films formed on the positive and negative electrodes by the additive are affected, mainly influencing the contents of organic sulfides, inorganic sulfides and fluorides. There are more organic sulfides and fluorides in the SEI film formed on the negative electrode, reducing the interfacial impedance of the negative electrode and facilitating the transport of Li+ at low temperatures. Meanwhile, there are more inorganic sulfides in the CEI film formed on the positive electrode, which can inhibit the side reactions at the electrode / electrolyte interface at high temperatures, thus significantly improving the high - temperature storage performance of the battery. Eventually, the battery has good high - and low - temperature performance. Detailed implementation mode
[0031] The following describes the present application in detail with reference to the embodiments, but the present application is not limited to these embodiments.
[0032] Unless otherwise specified, the raw materials in the embodiments of the present application are all purchased through commercial channels.
[0033] Example 1
[0034] Prepare a ternary lithium - ion battery electrolyte: the electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include additive A, VC and LiPO2F2, with mass fractions of 1%, 1% and 1% of the total mass of the electrolyte respectively.
[0035] Among them, additive A is
[0036] The positive electrode of the ternary lithium - ion battery is prepared as follows: the mass ratio of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, conductive carbon black, and PVDF is 94:4:2, which are dissolved in N - methylpyrrolidone and mixed evenly, and then double - side coated on the aluminum foil. The loading of the positive electrode active material is 5 mg / cm 2 , and after vacuum drying, it is cut into rectangular electrode sheets with a length of 200 mm and a width of 146 mm for standby. The negative electrode of the battery is prepared as follows: the mass ratio of graphite, hard carbon, conductive carbon black, and binder is 60:30:8:2, which are dissolved in an appropriate amount of water and mixed evenly, and then double - side coated on the copper foil. The loading of the negative electrode active material is 2.8 mg / cm 2 , and after vacuum drying, it is cut into rectangular electrode sheets with a length of 200 mm and a width of 146 mm for standby. Using SC12 as the separator, multiple soft - pack batteries are assembled in a drying room, 25 g of electrolyte is added, and then the assembled batteries are subjected to high - temperature formation, high - temperature aging, normal - temperature aging, secondary capacitance - division and other test steps to form a complete SEI film on the electrode surface.
[0037] Battery high-temperature storage performance test method:
[0038] 1. At an ambient temperature of 25°C ± 2°C, charge at a constant current of 1C at a constant voltage until 4.2V, with a cut-off current of 0.05C;
[0039] 2. At an ambient temperature of 25°C ± 2°C, stand for 1h;
[0040] 3. At an ambient temperature of 25°C ± 2°C, discharge at a constant current of 1C until 2.8V (record the discharge capacity C1);
[0041] 4. At an ambient temperature of 25°C ± 2°C, stand for 1h;
[0042] 5. At an ambient temperature of 25°C ± 2°C, charge at a constant current of 1C at a constant voltage until 4.2V, with a cut-off current of 0.05C;
[0043] 6. At an ambient temperature of 55°C ± 2°C, stand for 7d;
[0044] 7. At an ambient temperature of 25°C ± 2°C, stand for 24h;
[0045] 8. At an ambient temperature of 25°C ± 2°C, discharge at a constant current of 1C until 2.8V (record the discharge capacity C2);
[0046] 9. At an ambient temperature of 25°C ± 2°C, stand for 1h;
[0047] 10. At an ambient temperature of 25°C ± 2°C, charge at a constant current of 1C at a constant voltage until 4.2V, with a cut-off current of 0.05C;
[0048] 11. At an ambient temperature of 25°C ± 2°C, stand for 1h;
[0049] 12. At an ambient temperature of 25°C ± 2°C, discharge at a constant current of 1C until 2.8V (record the discharge capacity C3);
[0050] Remaining capacity calculation method: (C2 / C1)*100%; Recovery capacity calculation method: (C3 / C1)*100%.
[0051] Battery low-temperature discharge performance test method:
[0052] 1. At an ambient temperature of 25°C ± 2°C, charge at a constant current of 1C at a constant voltage until 4.2V, with a cut-off current of 0.05C;
[0053] 2. At an ambient temperature of 25°C ± 2°C, stand for 1h;
[0054] 3. At an ambient temperature of 25°C ± 2°C, discharge at a constant current of 1C for 42min, that is, adjust to 30% SOC;
[0055] 4. Let it stand still at -30°C ± 2°C for 24 h;
[0056] 5. Discharge with a current of at least 35 A for 2 s.
[0057] The test results are shown in Table 1.
[0058] Example 2
[0059] Prepare the electrolyte for a ternary lithium-ion battery: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include Additive A, VC, and LiPO2F2, and the mass fractions are 2%, 1%, and 1% of the total mass of the electrolyte, respectively;
[0060] where Additive A is
[0061] The test method is the same as that in Example 1;
[0062] The test results are shown in Table 1.
[0063] Example 3
[0064] Prepare the electrolyte for a ternary lithium-ion battery: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include Additive D, VC, and LiPO2F2, and the mass fractions are 1%, 1%, and 1% of the total mass of the electrolyte, respectively;
[0065] where Additive D is
[0066] The test method is the same as that in Example 1;
[0067] The test results are shown in Table 1.
[0068] Example 4
[0069] Prepare the electrolyte for a ternary lithium-ion battery: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include Additive I, VC, and LiPO2F2, and the mass fractions are 1%, 1%, and 1% of the total mass of the electrolyte, respectively;
[0070] where Additive I is
[0071] The test method is the same as that in Example 1;
[0072] The test results are shown in Table 1.
[0073] Example 5
[0074] Prepare the electrolyte for a ternary lithium-ion battery: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include additive E, VC, and LiPO2F2, and the mass fractions are 1%, 1%, and 1% of the total mass of the electrolyte, respectively;
[0075] Additive H is
[0076] The testing method is the same as that in Example 1;
[0077] The testing results are shown in Table 1.
[0078] Example 6
[0079] Prepare the electrolyte for a ternary lithium-ion battery: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include additive F, VC, and LiPO2F2, and the mass fractions are 1%, 1%, and 1% of the total mass of the electrolyte, respectively;
[0080] Additive K is
[0081] The testing method is the same as that in Example 1;
[0082] The testing results are shown in Table 1.
[0083] Example 7
[0084] Prepare the electrolyte for a ternary lithium-ion battery: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include additive H, VC, and LiPO2F2, and the mass fractions are 1%, 1%, and 1% of the total mass of the electrolyte, respectively;
[0085] Additive N is
[0086] The testing method is the same as that in Example 1;
[0087] The testing results are shown in Table 1.
[0088] Example 8
[0089] Preparation of ternary lithium-ion battery electrolyte: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include additive A, VC and LiPO2F2, and the mass fractions are 5%, 1% and 1% of the total mass of the electrolyte respectively.
[0090] Among them, additive A is
[0091] The testing method is the same as that in Example 1;
[0092] The test results are shown in Table 1.
[0093] Comparative Example 1
[0094] The wide-temperature electrolyte is purchased from Guangzhou Tianci, and the model is TC-EFF05;
[0095] The testing method is the same as that in Example 1;
[0096] The test results are shown in Table 1.
[0097] Comparative Example 2
[0098] Preparation of ternary lithium-ion battery electrolyte: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate with a volume ratio of 2:3:5; the additives include VC and LiPO2F2, and the mass fractions are 1% and 1% of the total mass of the electrolyte respectively.
[0099] The testing method is the same as that in Example 1;
[0100] The test results are shown in Table 1.
[0101] Comparative Example 3
[0102] Preparation of ternary lithium-ion battery electrolyte: The electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate with a volume ratio of 2:3:5;
[0103] The additives include additive Q, VC and LiPO2F2, and the mass fractions are 1%, 1% and 1% of the total mass of the electrolyte respectively;
[0104] Additive Q is
[0105] The testing method is the same as that in Example 1;
[0106] The test results are shown in Table 1.
[0107] Table 1 shows the discharge capacity, capacity retention rate and recovery rate of the ternary lithium-ion batteries of Examples 1-7 and Comparative Examples 1-3 before and after storage at a high temperature of 55°C, as well as the cut-off voltage of the batteries at the end of 2 s of discharge at -30°C.
[0108] Comparative Example 4
[0109] Prepare the electrolyte for the ternary lithium-ion battery: the electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, and the volume ratio is 2:3:5; the additives include Additive A, VC and LiPO2F2, and the mass fractions are 10%, 1% and 1% of the total mass of the electrolyte respectively.
[0110] Among them, Additive A is
[0111] The test method is the same as that of Example 1;
[0112] The test results are shown in Table 1.
[0113] Comparative Example 5
[0114] Prepare the electrolyte for the ternary lithium-ion battery: the electrolyte lithium salt is LiPF6, and the concentration of the lithium salt in the electrolyte is 1.0 mol / L; the solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, and the volume ratio is 2:3:5; the additives include Additive C, VC and LiPO2F2, and the mass fractions are 1%, 1% and 1% of the total mass of the electrolyte respectively;
[0115] Among them, Additive C is
[0116] The test method is the same as that of Example 1;
[0117] The test results are shown in Table 1.
[0118] Table 1 shows the discharge capacity, capacity retention rate and recovery rate of the ternary lithium-ion batteries of Examples 1-8 and Comparative Examples 1-5 before and after storage at a high temperature of 55°C, as well as the cut-off voltage of the batteries at the end of 2 s of discharge at -30°C
[0119] Table 1
[0120]
[0121]
[0122] As can be seen from Table 1, in Examples 1 to 7, by introducing -CH3, -CH3O, -COOH, -CF3, -F and their isomers into the molecular structure of 1,3-propanesultone, the interfacial impedance of the negative electrode is reduced, which is beneficial to the transport of Li+ at low temperatures. At the same time, there are more inorganic sulfides in the CEI film formed on the positive electrode, which can inhibit the side reactions at the electrode / electrolyte interface at high temperatures, thereby significantly improving the high-temperature storage performance of the battery. Finally, the battery has good high and low temperature performance. Examples 1, 2 and 8 show that when the content of Additive A is 1% and 2%, the high and low temperature performance of the battery is excellent, and when the content increases to 5%, the high and low temperature performance decreases. Comparative Example 4 shows that when the additive content is 10%, the high and low temperature performance of the battery decreases significantly. It shows that the additive content is crucial for the wide temperature performance of the battery.
[0123] Comparative Example 1 is a commercial electrolyte with the worst performance. Comparative Example 2 is without adding Its performance is relatively poor. The additive in Comparative Example 3 is 1,3-propanesultone, and its performance is worse than that of the examples.
[0124] As can be seen from Example 1 and Comparative Example 5, the change in the position of R in the additive also affects the wide temperature performance of the battery.
[0125] In summary, introducing -CH3, -CH3O, -COOH, -CF3, -F and their isomers onto the 1,3-propanesultone molecule is beneficial to improving the wide temperature performance of the battery.
[0126] The above are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, making some changes or modifications using the disclosed technical content is equivalent to equivalent implementation cases and all belong to the scope of the technical solution.
Claims
1. A ternary lithium-ion battery electrolyte, characterized in that, The composition of the ternary lithium-ion battery electrolyte includes: lithium salt, ester solvent and additives; The additives include additive I and additive II; Additive I has the structure shown in Formula I; Among them, R is selected from at least one of -CH3, -CH3O, -COOH, -CF3, -F.
2. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, Additive I is selected from at least one of the structures shown in a to p; 3. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, Additive II is selected from at least one of vinylene carbonate, ethylene vinylene carbonate, lithium difluorophosphate, fluorinated ethylene carbonate, and tripropynyl phosphate.
4. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, In the ternary lithium-ion battery electrolyte, the mass fraction of additive I is 0.5% to 5%; Preferably, in the ternary lithium-ion battery electrolyte, the mass fraction of additive I is 0.5% to 2%.
5. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, In the ternary lithium-ion battery electrolyte, the mass fraction of additive II is 0.5% to 5%; Preferably, in the ternary lithium-ion battery electrolyte, the mass fraction of additive II is 0.5% to 2%.
6. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, The lithium salt is selected from at least one of LiPF6, LiBF4, LiClO4, LiAsF6, LiBOB, LiODFB, LiFSI, LiTFSI.
7. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, In the ternary lithium-ion battery electrolyte, the concentration of the lithium salt is 0.8 mol / L to 3 mol / L; Preferably, in the ternary lithium-ion battery electrolyte, the concentration of the lithium salt is 1 to 2 mol / L.
8. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, The ester solvent is selected from at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, methyl acetate, ethyl acetate, n-butyl acetate, and isobutyl acetate.
9. The ternary lithium-ion battery electrolyte according to claim 1, characterized in that, The ester solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.
10. Application of the ternary lithium-ion battery electrolyte according to any one of claims 1-9 in a ternary lithium-ion battery, characterized in that, The temperature range of the application is -40°C to 80°C.