Electrolyte solution and its use

Abstract

Electrolyte solution comprising fluoroethylene carbonate and tris(vinyldimethylsilyl) phosphate; wherein, based on a total mass of the electrolyte solution, the mass fraction of fluoroethylene carbonate is in the range of 8% to 15%, and the mass fraction of tris(vinyldimethylsilyl) phosphate is in the range of 0.5% to 2%; and The mass ratio of tris(vinyldimethylsilyl) phosphate to fluoroethylene carbonate is in the range of 1:8 to 1:30.

Description

[0001] The present application claims priority from Chinese patent application No. 2023106680741, filed with the Chinese Patent Office on June 7, 2023, entitled “ELECTROLYTIC SOLUTION AND USE THEREOF”, which is incorporated in full by reference into this document, and claims priority from Chinese patent application No. 2023106680703, filed with the Chinese Patent Office on June 7, 2023, entitled “ELECTROLYTIC SOLUTION AND USE THEREOF”, which is incorporated in full by reference into this document. TECHNICAL AREA

[0002] The present application relates to an electrolyte solution and its use and concerns the technical field of energy. BACKGROUND

[0003] With advancing technology and the diversification of energy demands, conventional energy sources are being depleted at an accelerating rate, and countries worldwide are accelerating their strategic deployment of new energy technologies. Among these technologies, energy batteries are increasingly emerging alongside the development of new energy vehicles, and energy storage batteries are expanding rapidly with the development of clean energy. Since 2017, competition in the new energy vehicle industry has intensified. Various energy battery companies are regularly researching, developing, and updating their products to identify energy systems that are better suited to the market, meeting the demands for high specific energy and battery lifespan, and ultimately replacing conventionally powered passenger cars and buses.

[0004] Lithium-ion batteries are one of the key products in new energy technology. Conventional lithium-ion batteries use graphite to create the negative electrode; however, the specific capacity of graphite is 372 mAh / g. -1This already creates difficulties in meeting the requirements for higher specific energy in lithium-ion batteries. For this reason, researchers worldwide are increasingly focusing on negative silicon electrode materials with high specific capacity. While negative silicon electrode materials can increase the energy density of batteries to a certain extent, they are prone to significant volume expansion during the battery cycling process. Consequently, the interface film between the negative electrode plate and the electrolyte solution is continuously damaged, leading to a constant degradation of the electrolyte solution and ultimately a deterioration of battery performance.

[0005] To solve the problem of battery performance degradation caused by damage to the interface film between the negative electrode plate and the electrolyte solution during the cycling process of batteries containing negative silicon electrode materials, researchers have proposed the development of new electrolyte solution additives to form a stable interface film on the surface of the negative electrode plate, thereby reducing the disadvantages caused by the expansion of negative silicon electrode materials.For example, using fluoroethylene carbonate (FEC) as an electrolyte solution additive can form a stable interface film on the surface of the negative electrode plate, effectively reducing the capacity loss caused by negative silicon electrode materials and lowering the interfacial impedance between the negative electrode plate and the electrolyte solution. However, FEC generates gas at high temperatures, which can lead to battery failure or even explosion. SUMMARY

[0006] A first aspect of the present application provides an electrolyte solution. By using this solution in a battery, the electrolyte solution not only facilitates the formation of a high-quality SEI film on the negative electrode surface, but also exhibits a low tendency to gas at high temperatures. Consequently, this facilitates the battery achieving excellent cycle performance at room temperature, cycle performance at high temperatures, and storage performance at high temperatures simultaneously.

[0007] A second aspect of the present application provides an electrolyte solution. This electrolyte solution has a low acidity and excellent stability. When used in a battery, the electrolyte solution facilitates the formation of a high-quality SEI film (which, for example, is resistant to high temperatures and exhibits low interfacial impedance) on the surface of the negative electrode plate. Consequently, this facilitates the battery achieving excellent electrochemical performance (for example, cycle life at room temperature, cycle life at high temperatures, and storage capacity at high temperatures).

[0008] A third aspect of the present application provides a battery which includes the aforementioned electrolyte solution, thereby exhibiting relatively excellent electrochemical performance.

[0009] The first aspect of the present application provides an electrolyte solution comprising fluoroethylene carbonate and tris(vinyldimethylsilyl) phosphate; Based on the total mass of the electrolyte solution, the mass fraction of fluoroethylene carbonate is in the range of 8% to 15%, and the mass fraction of tris(vinyldimethylsilyl) phosphate is in the range of 0.5% to 2%; and The mass ratio of tris(vinyldimethylsilyl) phosphate to fluoroethylene carbonate is in the range of 1:8 to 1:30.

[0010] The electrolyte solution described above further includes a first lithium salt with a mass fraction in the range of 6% to 14%, and the first lithium salt is lithium hexafluorophosphate.

[0011] The electrolyte solution described above also contains a second lithium salt with a mass fraction in the range of 0.5% to 8%; and The second lithium salt is selected from the group consisting of lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide and a combination thereof.

[0012] The second lithium salt in the electrolyte solution described above is lithium bis(fluorosulfonyl)imide and / or lithium difluorophosphate.

[0013] The electrolyte solution described above contains a mass fraction of lithium bis(fluorosulfonyl)imide in the range of 1% to 8% based on the total mass of the electrolyte solution; and / or

[0014] The mass fraction of lithium difluorophosphate is in the range of 0.5% to 1% based on the total mass of the electrolyte solution.

[0015] The electrolyte solution described above also contains a solvent with a mass fraction in the range of 65% to 86%.

[0016] The electrolyte solution described above also contains a solvent with a mass fraction in the range of 72% to 76%.

[0017] In the electrolyte solution described above, the solvent contains a cyclic carbonate and an acyclic carbonate.

[0018] In the electrolyte solution described above, the mass ratio of cyclic carbonate to acyclic carbonate is in the range of (2 to 3):(5 to 7).

[0019] The electrolyte solution described above also contains a further additive with a mass fraction in the range of 0.003% to 4%; and The further additive is selected from the group consisting of ethylene sulfite, 1,4-butane sultone, prop-1-ene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, maleic anhydride, tris(trimethylsilyl)borate, difluoroethylene carbonate, vinylene carbonate, triphenyl phosphite and a combination thereof.

[0020] The electrolyte solution described above also contains the additional additive with a mass fraction in the range of 0.5% to 3.8%.

[0021] The second aspect of the present application provides an electrolyte solution comprising fluoroethylene carbonate, tris(vinyldimethylsilyl) phosphate and an isocyanate compound.

[0022] The electrolyte solution described above contains a mass fraction of fluoroethylene carbonate in the range of 8% to 20% based on the total mass of the electrolyte solution; and / or The mass fraction of tris(vinyldimethylsilyl) phosphate is in the range of 0.5% to 2% based on the total mass of the electrolyte solution; and / or The mass fraction of the isocyanate compound is in the range of 0.1% to 0.8% based on the total mass of the electrolyte solution.

[0023] In the electrolyte solution described above, the isocyanate compound is selected from the group consisting of hexamethylene diisocyanate (CAS No. 822-06-0), 1,4-phenylene diisocyanate (CAS No.: 109-49-4), trimethylsilyl isocyanate (CAS No.: 1118-02-1), toluene-2,4-diisocyanate (CAS No.: 584-84-9), 3-(isocyanatopropyl)trimethoxysilane (CAS No.: 15396-00-6), 3-(isocyanatopropyl)triethoxysilane (CAS No.: 24801-88-5), 3-(isocyanatopropyl)dimethoxymethylsilane (CAS No.: 26115-72-0), 3-(isocyanatopropyl)diethoxymethylsilane (CAS No.: 33491-28-0), 3-(Isocyanatopropyl)methoxydimethylsilane (CAS No.: 21116-75-6), 1-(Isocyanatomethyl)trimethoxysilane (CAS No.: 78450-75-6), 1-(Isocyanatomethyl)triethoxysilane (CAS No.: 132112-76-6), 1-(Isocyanatomethyl)dimethoxymethylsilane (CAS No.: 406679-89-8) and a combination thereof.

[0024] In the electrolyte solution described above, the isocyanate compound is selected from the group consisting of hexamethylene diisocyanate, 1,4-phenylene diisocyanate, trimethylsilyl isocyanate and a combination thereof.

[0025] The electrolyte solution described above also contains a second lithium salt with a mass fraction in the range of 12.5% ​​to 17%.

[0026] In the electrolyte solution described above, the lithium salt contains a first lithium salt with a mass fraction in the range of 6% to 15% and is the first lithium salt lithium hexafluorophosphate.

[0027] In the electrolyte solution described above, the lithium salt further comprises a third lithium salt and is the third lithium salt lithium bis(fluorosulfonyl)imide and / or lithium difluorophosphate.

[0028] The electrolyte solution described above contains a mass fraction of lithium bis(fluorosulfonyl)imide in the range of 1% to 6% based on the total mass of the electrolyte solution; and / or

[0029] The mass fraction of lithium difluorophosphate is in the range of 0.5% to 1% based on the total mass of the electrolyte solution.

[0030] In the electrolyte solution described above, the solvent is selected from the group consisting of ethylene carbonate and propylene carbonate, and the total mass fraction of ethylene carbonate and propylene carbonate is in the range of 17.46% to 23.22% based on the total mass of the electrolyte solution; and / or The solvent consists of at least two solvents selected from the group comprising ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate, and the total mass fraction of the at least two solvents of ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate is in the range of 40.74% to 54.18% based on the total mass of the electrolyte solution.

[0031] The electrolyte solution described above also contains a further additive with a mass fraction in the range of 0.03% to 4%; and The further additive is selected from the group consisting of ethylene sulfite, 1,4-butane sultone, prop-1-ene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, maleic anhydride, tris(trimethylsilyl)borate, difluoroethylene carbonate, vinylene carbonate and a combination thereof.

[0032] The electrolyte solution described above also contains the additional additive with a mass fraction in the range of 0.5% to 3.8%.

[0033] A third aspect of the present application provides a battery that includes the electrolyte solution as described above.

[0034] The electrolyte solution of the first aspect of the present application has a simple composition. When used in a battery, such as a secondary battery, the electrolyte solution not only facilitates the formation of a denser and more stable SEI film on the surface of the negative electrode plate of the secondary battery, which protects the negative electrode plate, but the electrolyte solution itself also exhibits a low tendency to gas formation at high temperatures. Consequently, this facilitates the secondary battery achieving excellent cycle performance at room temperature, cycle performance at high temperatures, and storage performance at high temperatures simultaneously.

[0035] The electrolyte solution of the second aspect of the present application has a simple composition and excellent stability. When used in a battery, such as a secondary battery, the electrolyte solution not only facilitates the formation of a more temperature-resistant SEI film on the surface of the negative electrode plate of the secondary battery, but also results in a low interfacial impedance between this SEI film and the negative electrode plate. Consequently, the secondary battery achieves excellent electrochemical performance.

[0036] The battery of the third aspect of the present application, which includes the electrode plate of the first aspect, has a dense and stable SEI film on the surface of the negative electrode plate, which further prevents contact damage between the negative electrode plate and the electrolyte solution and gives the battery of the present application a low tendency to gas generation at high temperature. Consequently, the battery of the present application exhibits superior electrochemical performance, such as high-temperature cycle performance, low-temperature cycle performance, and high-temperature storage performance. Furthermore, the electrolyte solution of the second aspect exhibits a high-temperature resistant SEI film on the surface of the negative electrode plate, and the interfacial impedance between the negative electrode plate and the electrolyte solution is low. Consequently, the battery of the present application exhibits superior electrochemical performance, such as high-temperature cycle performance, low-temperature cycle performance, and high-temperature storage performance. DETAILED DESCRIPTION

[0037] To clarify the tasks, technical solutions, and advantages of the present application, the technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, but not all of them. Based on the embodiments in the present application, all other embodiments that the person skilled in the art can implement without creative effort are within the scope of protection of the present application.

[0038] In the prior art, if an electrolyte solution contains FEC, it can form a stable SEI film on the surface of a negative electrode plate, thus facilitating improved cycle performance at room temperature. However, the temperature stability of FEC is poor, and it generates gas at high temperatures. Therefore, if an electrolyte solution containing FEC is used in a battery, it will generate gas at high temperatures, leading to battery failure and negatively impacting the battery's cycle performance at high temperatures. In particular, if the mass fraction of FEC in the electrolyte solution exceeds 2%, the battery's cycle performance at high temperatures is poor, severely affecting its application scenarios.

[0039] In this regard, the first aspect of the present application provides an electrolyte solution comprising fluoroethylene carbonate and tris(vinyldimethylsilyl) phosphate; Based on the total mass of the electrolyte solution, the mass fraction of fluoroethylene carbonate is in the range of 8% to 15%, and the mass fraction of tris(vinyldimethylsilyl) phosphate is in the range of 0.5% to 2%; and

[0040] The mass ratio of tris(vinyldimethylsilyl) phosphate to fluoroethylene carbonate is in the range of 1:8 to 1:30.

[0041] The FEC and the tris(vinyldimethylsilyl) phosphate in the present application can be conventional FEC and tris(vinyldimethylsilyl) phosphate. They can be commercially available or produced in the laboratory.

[0042] The electrolyte solution of the present application contains FEC and tris(vinyldimethylsilyl) phosphate in specific concentrations. Among these, a high concentration of FEC can form a stable SEI film on the surface of the negative electrode plate, which can effectively reduce the interfacial impedance between the negative electrode plate and the electrolyte solution, reduce the negative effects of negative electrode plate expansion, and improve the battery's cycle performance at room temperature. The specific concentration of tris(vinyldimethylsilyl) phosphate can effectively inhibit FEC gas generation at high temperatures, thereby significantly improving the battery's cycle performance and storage capacity at high temperatures.For this reason, the electrolyte solution of the present application can enable the battery to simultaneously achieve excellent cycle performance at room temperature, cycle performance at high temperature, and storage performance at high temperature.

[0043] Furthermore, if the mass ratio of tris(vinyldimethylsilyl) phosphate to fluoroethylene carbonate is in the range of 1:8 to 1:20, the battery achieves even better cycle performance at room temperature, cycle performance at high temperature, and storage performance at high temperature.

[0044] In some embodiments of the present application, the electrolyte solution further comprises a first lithium salt having a mass fraction in the range of 6% to 14% and is the first lithium salt lithium hexafluorophosphate.

[0045] It is understood that the lithium hexafluorophosphate used in this technical context can be conventionally used lithium hexafluorophosphate. Lithium hexafluorophosphate can be commercially available or produced in a laboratory. If the electrolyte solution contains lithium hexafluorophosphate with the aforementioned concentration, the lithium hexafluorophosphate can passivate the current collector with the positive electrode, thereby further improving the electrochemical performance of the battery. Furthermore, since lithium hexafluorophosphate is inexpensive and readily available, the electrolyte solution containing lithium hexafluorophosphate also has the advantage of low cost, making it suitable for a wide range of applications.

[0046] Furthermore, the electrolyte solution also contains a second lithium salt with a mass fraction in the range of 0.5% to 8%; and The second lithium salt is selected from the group consisting of lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide and a combination thereof.

[0047] In the present application, the second lithium salt exhibits excellent temperature stability and the ability to reduce the impedance of the electrolyte solution. Consequently, the electrolyte solution containing the second lithium salt exhibits superior temperature stability, which can effectively improve the battery's cycle life at high temperatures. In particular, the first and second lithium salts act synergistically, which can significantly enhance the battery's lifespan and performance at high temperatures.

[0048] The inventors also discovered during their research that lithium difluorophosphate has lower solubility and can better reduce the battery's impedance; lithium bis(fluorosulfonyl)imide exhibits superior temperature stability. If the second lithium salt is lithium bis(fluorosulfonyl)imide and / or lithium difluorophosphate, the battery's electrochemical performance can be further improved.

[0049] The present application can further select the mass fractions of lithium bis(fluorosulfonyl)imide and lithium difluorophosphate in the electrolyte solution to further improve the electrochemical performance of the battery. For example, in some embodiments of the present application, the mass fraction of lithium bis(fluorosulfonyl)imide is in the range of 1% to 8% based on the total mass of the electrolyte solution; and / or

[0050] The mass fraction of lithium difluorophosphate is in the range of 0.5% to 1% based on the total mass of the electrolyte solution.

[0051] The second lithium salt of the present application may be commercially available or produced in the laboratory.

[0052] In some embodiments of the present application, if the electrolyte solution further includes a solvent with a mass fraction in the range of 65% to 68%, the viscosity of the electrolyte solution is appropriate, which can simplify the manufacturing process and improve the electrochemical performance of the battery.

[0053] Furthermore, if the electrolyte solution also contains a solvent with a mass fraction in the range of 72% to 76%, the battery exhibits more excellent electrochemical performance.

[0054] The present application does not specifically limit the solvent, which may be any solvent conventionally used in the art. For example, the solvent may be at least two selected from the group consisting of acyclic carbonate, cyclic carbonate, fluorinated cyclic carbonate, fluorinated acyclic carbonate, acyclic carboxylate, cyclic carboxylate, and fluorinated acyclic ether. Furthermore, the solvent may be at least two selected from the group consisting of diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, methyl trifluoroethyl carbonate, difluoroethylene carbonate, ethyl acetate, propyl propionate, 1,4-butyrolactone, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and methyl nonafluorobutyl ether.

[0055] In some embodiments of the present application, if the solvent includes a cyclic carbonate and an acyclic carbonate, the electrolyte solution obtained, when applied in a battery, can further improve the electrochemical performance of the battery.

[0056] The present application does not specifically limit the cyclic carbonate, which may be any cyclic carbonate conventionally used in the industry. For example, the cyclic carbonate may be selected from the group consisting of ethylene carbonate, propylene carbonate, and a combination thereof.

[0057] The present application does not specifically limit the acyclic carbonate, which may be any acyclic carbonate conventionally used in the art. For example, the acyclic carbonate may be selected from the group consisting of ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, and a combination thereof.

[0058] Furthermore, if the mass ratio of the cyclic carbonate to the acyclic carbonate is in the range of (2 to 3):(5 to 7), the cyclic carbonate and the acyclic carbonate can act synergistically, thereby improving the electrochemical performance of the battery.

[0059] According to actual requirements, the present application may also add a further additive to the electrolyte solution in addition to the FEC and the tris(vinyldimethylsilyl) phosphate. In some embodiments of the present application, the electrolyte solution further comprises the additional additive in a mass fraction in the range of 0.003% to 4%; and The further additive is selected from the group consisting of ethylene sulfite, 1,4-butane sultone, prop-1-ene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, maleic anhydride, tris(trimethylsilyl)borate, difluoroethylene carbonate, vinylene carbonate, triphenyl phosphite and a combination thereof.

[0060] In the present application, if the electrolyte solution contains, in addition to the FEC and the tris(vinyldimethylsilyl) phosphate, the further additive, the electrochemical performance of the battery can be further effectively improved. Furthermore, the mass fraction of the further additive in the electrolyte solution can be in the range of 0.5% to 3.8%.

[0061] To address the problem of battery failure caused by FEC gassing at high temperatures, adding tris(vinyldimethylsilyl) phosphate to an electrolyte solution can prevent FEC gassing at high temperatures. However, in practical applications, when an electrolyte solution contains both FEC and tris(vinyldimethylsilyl) phosphate, the acidity of the electrolyte solution increases, which can lead to an increase in battery impedance.

[0062] In the prior art, if an electrolyte solution contains tris(vinyldimethylsilyl) phosphate, the tris(vinyldimethylsilyl) phosphate is prone to generating byproducts such as phosphoric acid and fluorosilicone gas during the battery's charging and discharging process. Among these, phosphoric acid simply increases the acidity of the electrolyte solution, causing it to degrade and affecting the battery's electrochemical performance; if an electrolyte solution contains fluoroethylene carbonate (FEC) and an isocyanate compound, it simply increases the battery's impedance.

[0063] In view of this, the second aspect of the present application provides an electrolyte solution comprising fluoroethylene carbonate, tris(vinyldimethylsilyl) phosphate and an isocyanate compound.

[0064] When the electrolyte solution of the present application is used in a battery, the isocyanate compound can, during the battery's charging and discharging process, prevent tris(vinyldimethylsilyl) phosphate from undergoing almost no side reactions, thereby avoiding the generation of phosphoric acid and improving the stability of the electrolyte solution. Furthermore, during the battery's charging and discharging process, the functional phosphate group of tris(vinyldimethylsilyl) phosphate can generate a low-impedance compound containing a phosphate salt, which can be embedded in the elastomer produced by the isocyanate compound, thus resolving the problem of high impedance caused by the isocyanate compound. Therefore, the electrolyte solution containing the isocyanate compound and tris(vinyldimethylsilyl) phosphate can significantly improve the battery's high-temperature stability and reduce its impedance.

[0065] Furthermore, during the battery's charging and discharging process, the combined use of the isocyanate compound and FEC can form a high-quality elastic polymer SEI film on the surface of the negative electrode. This protects the negative electrode and prevents the electrochemical performance of the battery from being affected by the expansion of the negative electrode. Tris(vinyldimethylsilyl) phosphate creates a Si-O-rich polymer film that further covers the surface of the SEI film formed by the FEC and the isocyanate compound, making the SEI film more resistant to high temperatures and thus improving the battery's performance at high temperatures. In summary, the electrolyte solution of the present application can enable the battery to simultaneously achieve excellent cycle performance at high temperature, cycle performance at room temperature and low interfacial impedances.

[0066] The present application can further select the mass fractions of FEC, tris(vinyldimethylsilyl) phosphate, and the isocyanate compound in the electrolyte solution to improve the overall performance of the electrolyte solution, thereby improving the electrochemical performance of the battery. For example, in some embodiments of the present application, the mass fraction of fluoroethylene carbonate is in the range of 8% to 20% based on the total mass of the electrolyte solution; and / or

[0067] The mass fraction of tris(vinyldimethylsilyl) phosphate is in the range of 0.5% to 2% based on the total mass of the electrolyte solution; and / or

[0068] The mass fraction of the isocyanate compound is in the range of 0.1% to 0.8% based on the total mass of the electrolyte solution.

[0069] In the present application, since tris(vinyldimethylsilyl) phosphate contains unsaturated bonds that can effectively form a film when a relatively small amount of the isocyanate compound in the present application is added, tris(vinyldimethylsilyl) phosphate and a small amount of the isocyanate compound can act synergistically to form a uniformly distributed protective film on the electrode surface, thereby improving the electrochemical performance of the battery.

[0070] In particular, if the mass fraction of fluoroethylene carbonate in the electrolyte solution is in the range of 8% to 20%, the mass fraction of tris(vinyldimethylsilyl) phosphate is in the range of 0.5% to 2%, and the mass fraction of the isocyanate compound is in the range of 0.1% to 0.8%, the battery can exhibit more excellent electrochemical performance.

[0071] The present application does not specifically limit the FEC, which may be a conventionally used FEC in the art. For example, the FEC may be commercially available or manufactured in the laboratory.

[0072] The present application does not specifically limit the tris(vinyldimethylsilyl) phosphate, which may be a tris(vinyldimethylsilyl) phosphate conventionally used in the industry. For example, the tris(vinyldimethylsilyl) phosphate may be commercially available or produced in the laboratory.

[0073] The present application does not specifically limit the isocyanate compound, which may be any isocyanate compound conventionally used in the art. For example, the isocyanate compound may be selected from the group consisting of hexamethylene diisocyanate, 1,4-phenylene diisocyanate, trimethylsilyl isocyanate, toluene-2,4-diisocyanate, 3-(isocyanatopropyl)trimethoxysilane, 3-(isocyanatopropyl)triethoxysilane, 3-(isocyanatopropyl)dimethoxymethylsilane, 3-(isocyanatopropyl)diethoxymethylsilane, 3-(isocyanatopropyl)methoxydimethylsilane, 1-(isocyanatomethyl)trimethoxysilane, 1-(isocyanatomethyl)triethoxysilane, 1-(isocyanatomethyl)dimethoxymethylsilane, and a combination thereof.

[0074] Furthermore, if the isocyanate compound is selected from the group consisting of hexamethylene diisocyanate, 1,4-phenylene diisocyanate, trimethylsilyl isocyanate and a combination thereof, the electrochemical performance of the battery can be further improved.

[0075] The above isocyanate compounds of the present application may all be commercially available or produced in the laboratory.

[0076] In some embodiments of the present application, if the electrolyte solution further includes a lithium salt with a mass fraction in the range of 12.5% ​​to 17%, the electrolyte solution can have an appropriate viscosity and improve the ionic conductivity performance of the electrolyte solution.

[0077] The present application does not specifically limit the lithium salt that may be selected from lithium salts conventionally used in the art. For example, the lithium salt may be selected from the group consisting of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluoro(oxalato)borate, and a combination thereof.

[0078] In some embodiments of the present application, the lithium salt includes a first lithium salt having a mass fraction in the range of 6% to 15% and is the first lithium salt lithium hexafluorophosphate.

[0079] It is understood that the lithium hexafluorophosphate used in this technical application can be conventionally used lithium hexafluorophosphate. This lithium hexafluorophosphate can be commercially available or produced in a laboratory. If the electrolyte solution contains lithium hexafluorophosphate with the aforementioned concentration, it can passivate the current collector with the positive electrode, thereby further improving the electrochemical performance of the battery. Furthermore, since lithium hexafluorophosphate is inexpensive and readily available, the electrolyte solution containing it also has the advantage of low cost, making it suitable for a wide range of applications.

[0080] Furthermore, the electrolyte solution also contains a third lithium salt; and is the third lithium salt selected from the group consisting of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide and a combination thereof.

[0081] In the present application, lithium difluorophosphate with lower solubility can effectively reduce the impedance of the electrolyte solution. When the lithium difluorophosphate and lithium hexafluorophosphate act synergistically, the battery's lifespan and impedance can be significantly improved.

[0082] Lithium bis(fluorosulfonyl)imide exhibits superior temperature stability. When lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate act synergistically, the battery's lifespan and performance at high temperatures can be improved without causing corrosion of the aluminum foil.

[0083] In some embodiments, if the third lithium salt includes both lithium difluorophosphate and lithium bis(fluorosulfonyl)imide, the third lithium salt is used in combination with the first lithium salt, which can further improve the electrochemical performance of the battery.

[0084] The present application can further select the mass fractions of lithium bis(fluorosulfonyl)imide and lithium difluorophosphate in the electrolyte solution to further improve the electrochemical performance of the battery. For example, in some embodiments of the present application, the mass fraction of lithium bis(fluorosulfonyl)imide is in the range of 1% to 6% based on the total mass of the electrolyte solution; and / or The mass fraction of lithium difluorophosphate is in the range of 0.5% to 1% based on the total mass of the electrolyte solution.

[0085] The second lithium salt of the present application may be commercially available or produced in the laboratory.

[0086] It is understood that the electrolyte solution of the present application further comprises a solvent. The present application does not specifically limit the solvent. The solvent may be at least two selected from the group consisting of acyclic carbonate, cyclic carbonate, fluorinated cyclic carbonate, fluorinated acyclic carbonate, acyclic carboxylate, cyclic carboxylate, and fluorinated acyclic ether. Furthermore, the solvent may be at least two selected from the group consisting of diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, methyl trifluoroethyl carbonate, difluoroethylene carbonate, ethyl acetate, propyl propionate, 1,4-butyrolactone, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and methyl nonafluorobutyl ether.

[0087] In some embodiments of the present application, if the solvent is at least two selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate, the electrochemical performance of the battery can be further improved.

[0088] Furthermore, the present application may also select the mass fractions of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate in the electrolyte solution to further improve the electrochemical performance of the battery. For example, in some embodiments of the present application, the total mass fraction of ethylene carbonate and propylene carbonate is in the range of 17.46% to 23.22% based on the total mass of the electrolyte solution; and / or The total mass fraction of at least two of ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate is in the range of 40.74% to 54.18% based on the total mass of the electrolyte solution.

[0089] According to actual requirements, the present application may also add a further additive to the electrolyte solution in addition to the FEC, the tris(vinyldimethylsilyl) phosphate, and the isocyanate compound. In some embodiments of the present application, the electrolyte solution further comprises the additional additive in a mass fraction ranging from 0.03% to 4%; and The further additive is selected from the group consisting of ethylene sulfite, 1,4-butane sultone, prop-1-ene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, maleic anhydride, tris(trimethylsilyl)borate, difluoroethylene carbonate, vinylene carbonate and a combination thereof.

[0090] In the present application, if the electrolyte solution contains, in addition to the FEC, the tris(vinyldimethylsilyl) phosphate, and the isocyanate compound, the further additive in specific concentrations, the electrochemical performance of the battery can be further effectively improved. Furthermore, the mass fraction of the further additive in the electrolyte solution can be in the range of 0.5% to 3.8%.

[0091] A third aspect of the present application provides a battery which includes the electrolyte solution of the first aspect and the second aspect of the present application.

[0092] It is understood that, in addition to the aforementioned electrolyte solution, the battery also includes a positive electrode and a negative electrode.

[0093] The present application does not specifically limit the positive electrode, which may be a conventional positive electrode. In some embodiments, the active material(s) for the positive electrode may be selected from the group consisting of lithium cobaltate, lithium iron phosphate, ternary material, and a combination thereof. Furthermore, the active material for the positive electrode may be a ternary material.

[0094] The present application does not specifically limit the negative electrode, which may be a conventional negative electrode. In some embodiments, the active material(s) for the negative electrode may be selected from the group consisting of synthetic graphite, natural graphite, lithium titanate, silicon, silicon-carbon, silicon-oxygen, silicon-metal compounds, and a combination thereof. Furthermore, the active materials for the negative electrode may be silicon-carbon and / or silicon-oxygen.

[0095] Furthermore, if the active material for positive electrodes is a ternary material with a high nickel content and the active material for negative electrodes is a silicon-carbon material, the resulting battery exhibits more excellent electrochemical performance.

[0096] During the specific application, the electrolyte solution of the first aspect of the present application generates a stable SEI film on the surface of the negative electrode, and the electrolyte solution is also prone to gas generation at high temperatures. For this reason, a battery incorporating the electrolyte solution of the present application can simultaneously achieve excellent cycle performance at room temperature, cycle performance at high temperatures, and storage performance at high temperatures.

[0097] During the specific application, the electrolyte solution of the second aspect of the present application forms a high-quality SEI film (for example, resistant to high temperature, with low interfacial impedance) on the surface of the negative electrode, thereby facilitating the battery achieving excellent electrochemical performance (for example, simultaneous cycle performance at room temperature, cycle performance at high temperature and storage performance at high temperature).

[0098] The electrolyte solution of the present application and its application in the specific examples are then presented in detail. Example 1a

[0099] The battery in this example was manufactured according to a process that includes the following steps: (1) Production of the positive electrode plate

[0100] The active material for positive electrodes, NCM811, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene carbon black were mixed according to a mass ratio of 96.5:2:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred using a vacuum stirrer until the raw materials were blended into a positive electrode slurry with uniform fluidity. The positive electrode slurry was applied evenly to both surfaces of an aluminum foil, each 7 µm thick, baked in an oven with five different temperature gradients, and then dried for 8 hours in an oven at 120 °C. This was followed by rolling, with the compression density of the active layer for positive electrodes checked to be 3.5 g / cm³. 3 and cutting to obtain the positive electrode plate. (2) Production of the negative electrode plate

[0101] The active material for negative electrodes is carbon-SiO₂ x / Graphite (the mass fraction of SiO x The mixture consisted of 10% sodium carboxymethylcellulose (CMC-Na), a thickening agent, styrene-butadiene rubber, a conductive agent, carbon black, and a conductive agent, a single-walled carbon nanotube (SWCNT), mixed according to a mass ratio of 95.9:1:2:1:0.1, deionized water was added, and the mixture was stirred using a vacuum stirrer to obtain a negative electrode slurry; and The slurry of the negative electrode was applied evenly to both surfaces of a copper foil with a thickness of 6 µm each, dried (temperature: 85 °C, time: 5 hours), while checking the compression density of the active layer of the negative electrode to be 1.65 g / cm³ 3 rolled and stamped to obtain the negative electrode plate. (3) Preparation of the electrolyte solution

[0102] In a glovebox filled with argon (humidity: <10 ppm, oxygen: <1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC) were uniformly mixed according to a mass ratio of 1.5:1.5:5:2 to obtain a mixed solution. Fully dried LiPF6, lithium difluorophosphate, FEC, and tris(vinyldimethylsilyl) phosphate were rapidly added to the mixed solution to obtain the electrolyte solution. The mass fraction of LiPF6 was 14%, the mass fraction of lithium difluorophosphate was 0.5%, the mass fraction of FEC was 8%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.8% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:10. (4) Production of the lithium-ion battery

[0103] The positive electrode plate from step (1), a separator and the negative electrode plate from step (2) were stacked on top of each other and then wound to obtain an untreated crude cell; The raw cell was placed in an outer packaging film, the electrolyte solution from step (3) was injected into the dried raw cell, and after processes such as vacuum packaging, resting, formation, shaping, and sorting, the desired lithium-ion battery was obtained; and The separator was an 8 µm thick coated polyethylene separator. Example 2a

[0104] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of FEC was 10%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.5% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:20. Example 3a

[0105] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of FEC was 10%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 1% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:10. Example 4a

[0106] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of FEC was 12%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.6% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:20. Example 5a

[0107] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of FEC was 12%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 1.2% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:10. Example 6a

[0108] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of FEC was 12%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 1.5% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:8. Example 7a

[0109] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of FEC was 15%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.5% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:30. Example 8a

[0110] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of FEC was 15%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 1.5% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:10. Example 9a

[0111] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of LiPF6 was 16.9% based on the total mass of the electrolyte solution. Example 10a

[0112] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) lithium bis(fluorosulfonyl)imide was used instead of lithium difluorophosphate and the mass fraction of lithium bis(fluorosulfonyl)imide was 1% based on the total mass of the electrolyte solution. Example 11a

[0113] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3), no lithium difluorophosphate was added based on the total mass of the electrolyte solution. Example 12a

[0114] The manufacturing process for the battery in this example was essentially the same as that in Example 1a, with the following exception: In step (3) the mass fraction of lithium difluorophosphate was 1.2% based on the total mass of the electrolyte solution. Comparative example 1a

[0115] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1a, with the following exception: In step (3) it contained no tris(vinyldimethylsilyl) phosphate and the mass fraction of FEC was 5% based on the total mass of the electrolyte solution. Comparative example 2a

[0116] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1a, with the following exception: In step (3) it contained no tris(vinyldimethylsilyl) phosphate and the mass fraction of FEC was 12% based on the total mass of the electrolyte solution. Comparative example 3a

[0117] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1a, with the following exception: In step (3) the mass fraction of FEC was 5%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.5% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:10. Comparative example 4a

[0118] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1a, with the following exception: In step (3) the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.4% based on the total mass of the electrolyte solution and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:20. Comparative example 5a

[0119] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1a, with the following exception: In step (3) the mass fraction of tris(vinyldimethylsilyl)phosphate was 1.2% based on the total mass of the electrolyte solution and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:6.6. Comparative example 6a

[0120] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1a, with the following exception: In step (3) the mass fraction of FEC was 10%, the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.25% based on the total mass of the electrolyte solution, and the mass ratio of tris(vinyldimethylsilyl)phosphate to FEC was 1:40. Example 1b

[0121] The battery in this example was manufactured according to a process that includes the following steps: (1) Production of the positive electrode plate

[0122] The active material for positive electrodes, NCM811, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene carbon black were mixed according to a mass ratio of 96.5:2:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred using a vacuum stirrer until the raw materials were blended into a positive electrode slurry with uniform fluidity. The positive electrode slurry was applied evenly to both surfaces of an aluminum foil, each 7 µm thick, baked in an oven with five different temperature gradients, and then dried for 8 hours in an oven at 120 °C. This was followed by rolling, with the compression density of the active layer for positive electrodes checked to be 3.5 g / cm³. 3 and cutting to obtain the positive electrode plate. (2) Production of the negative electrode plate

[0123] The active material for negative electrodes is carbon-SiO₂ x / Graphite (the mass fraction of SiO x The mixture consisted of 10% sodium carboxymethylcellulose (CMC-Na), a thickening agent, styrene-butadiene rubber, a conductive agent, carbon black, and a conductive agent, a single-walled carbon nanotube (SWCNT), mixed according to a mass ratio of 95.9:1:2:1:0.1, deionized water was added, and the mixture was stirred using a vacuum stirrer to obtain a negative electrode slurry; and The slurry of the negative electrode was applied evenly to both surfaces of a copper foil with a thickness of 6 µm each, dried (temperature: 85 °C, time: 5 hours), while checking the compression density of the active layer of the negative electrode to be 1.65 g / cm³ 3 rolled and stamped to obtain the negative electrode plate. (3) Preparation of the electrolyte solution

[0124] In a glovebox filled with argon (humidity: <10 ppm, oxygen: <1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC) were uniformly mixed according to a mass ratio of 1.5:1.5:5:2 to obtain a mixed solution. Fully dried LiPF6, FEC, tris(vinyldimethylsilyl) phosphate, and hexamethylene diisocyanate were rapidly added to the mixed solution to obtain the electrolyte solution. The mass fraction of LiPF6 was 14.5%, the mass fraction of FEC was 10%, the mass fraction of Tris(vinyldimethylsilyl)phosphate was 1%, and the mass fraction of Hexamethylene diisocyanate was 0.1% based on the total mass of the electrolyte solution. (4) Production of the lithium-ion battery

[0125] The positive electrode plate from step (1), a separator and the negative electrode plate from step (2) were stacked on top of each other and then wound to obtain an untreated crude cell; The raw cell was placed in an outer packaging film, the electrolyte solution from step (3) was injected into the dried raw cell, and after processes such as vacuum packaging, resting, formation, shaping, and sorting, the desired lithium-ion battery was obtained; and The separator was an 8 µm thick coated polyethylene separator. Example 2b

[0126] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) the mass fraction of hexamethylene diisocyanate was 0.5% based on the total mass of the electrolyte solution. Example 3b

[0127] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) the mass fraction of hexamethylene diisocyanate was 0.8% based on the total mass of the electrolyte solution. Example 4b

[0128] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 1,4-phenylene diisocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of 1,4-phenylene diisocyanate was 0.1% based on the total mass of the electrolyte solution. Example 5b

[0129] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 1,4-phenylene diisocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of 1,4-phenylene diisocyanate was 0.5% based on the total mass of the electrolyte solution. Example 6b

[0130] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 1,4-phenylene diisocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of 1,4-phenylene diisocyanate was 0.8% based on the total mass of the electrolyte solution. Example 7b

[0131] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) trimethylsilyl isocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of trimethylsilyl isocyanate was 0.1% based on the total mass of the electrolyte solution. Example 8b

[0132] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) trimethylsilyl isocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of trimethylsilyl isocyanate was 0.5% based on the total mass of the electrolyte solution. Example 9b

[0133] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) trimethylsilyl isocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of trimethylsilyl isocyanate was 0.8% based on the total mass of the electrolyte solution. Example 10b

[0134] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 3-(isocyanatopropyl)triethoxysilane was used to replace hexamethylene diisocyanate, and the mass fraction of 3-(isocyanatopropyl)triethoxysilane was 0.1% based on the total mass of the electrolyte solution. Example 11b

[0135] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 3-(isocyanatopropyl)triethoxysilane was used to replace hexamethylene diisocyanate, and the mass fraction of 3-(isocyanatopropyl)triethoxysilane was 0.5% based on the total mass of the electrolyte solution. Example 12b

[0136] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 3-(isocyanatopropyl)triethoxysilane was used to replace hexamethylene diisocyanate, and the mass fraction of 3-(isocyanatopropyl)triethoxysilane was 0.8% based on the total mass of the electrolyte solution. Example 13b

[0137] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) the mass fraction of LiPF6 was 18.9% based on the total mass of the electrolyte solution. Example 14b

[0138] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) a third lithium salt, lithium difluorophosphate, was added and the mass fraction of lithium difluorophosphate was 0.5% based on the total mass of the electrolyte solution. Example 15b

[0139] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) the mass fraction of fluoroethylene carbonate was 5% based on the total mass of the electrolyte solution. Example 16b

[0140] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) the mass fraction of tris(vinyldimethylsilyl)phosphate was 0.4% based on the total mass of the electrolyte solution. Example 17b

[0141] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) the mass fraction of hexamethylene diisocyanate was 1% based on the total mass of the electrolyte solution. Example 18b

[0142] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 1,4-phenylene diisocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of 1,4-phenylene diisocyanate was 1% based on the total mass of the electrolyte solution. Example 19b

[0143] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) trimethylsilyl isocyanate was used to replace hexamethylene diisocyanate, and the mass fraction of trimethylsilyl isocyanate was 1% based on the total mass of the electrolyte solution. Example 20b

[0144] The manufacturing process for the battery in this example was essentially the same as that in Example 1b, with the following exception: In step (3) 3-(isocyanatopropyl)triethoxysilane was used to replace hexamethylene diisocyanate, and the mass fraction of 3-(isocyanatopropyl)triethoxysilane was 1% based on the total mass of the electrolyte solution. Comparative example 1b

[0145] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1b, with the following exception: In step (3) Tris(vinyldimethylsilyl) phosphate and hexamethylene diisocyanate were not added. Comparative example 2b

[0146] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1b, with the following exception: In step (3) it did not contain any hexamethylene diisocyanate. Comparative example 3b

[0147] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1b, with the following exception: In step (3) it contained no tris(vinyldimethylsilyl) phosphate and the mass fraction of hexamethylene diisocyanate was 0.1% based on the total mass of the electrolyte solution. Comparative example 4b

[0148] The manufacturing process of the battery from this comparative example was essentially the same as that from example 1b, with the following exception: In step (3) Tris(trimethylsilyl) phosphate was used to replace hexamethylene diisocyanate, and the mass fraction of Tris(trimethylsilyl) phosphate was 0.1% based on the total mass of the electrolyte solution. Performance test

[0149] The batteries from the examples and comparison examples were subjected to the following performance tests and the test results are shown in Tables 1a and 1b; 1) Capacity retention rate after cycling at room temperature

[0150] The battery was charged to 4.2 V at a constant current of 1 C at room temperature (25 °C), charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C, and then discharged to 2.75 V at 1 C. The charge-discharge cycle was repeated for 500 cycles. The discharge capacity at the 500th cycle was tested and recorded, and divided by the discharge capacity at the first cycle to obtain the capacity retention rate. 2) Capacity retention rate after high-temperature cycling

[0151] The battery was charged to 4.2 V at a constant current of 1 C at a high temperature (60 °C), charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C, and then discharged to 2.75 V at 1 C. The charge-discharge cycle was repeated for 400 cycles. The discharge capacity at the 400th cycle was tested and recorded, and divided by the discharge capacity at the first cycle to obtain the capacity retention rate. 3) Thickness test during storage at high temperature

[0152] The battery was charged to 4.2 V at a constant current of 1 C at room temperature (25 °C), charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C, and then discharged to 2.75 V at a constant current of 1 C. The battery thickness was recorded as H1. At room temperature (25 °C), the battery was charged to 4.2 V at a constant current of 1 C, charged at a constant current of 4.2 V until the cutoff current was 0.05 C, then the battery was brought to a high temperature (60 °C) and stored for 7 days. The battery was then removed, and its thickness was tested using a thickness gauge; the thickness value was recorded as H2. Battery thickness change rate=(H2−H1) / H1∗100%. 4) DCIR test at high temperature

[0153] The battery was charged to 4.2 V at a constant current of 1 C at room temperature (25 °C), charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C, and then discharged at a constant current of 1 C for 0.5 hours. After resting for 1 hour, it was discharged at 2 C for 10 seconds. The DCIR of the battery at a state of charge (SOC) of 50% was calculated and recorded as D1. The battery that completed the performance test after 14 days of storage at high temperature (60 °C) was charged to 4.2 V at a constant current of 1 C at room temperature (25 °C), charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C, and then discharged at a constant current of 1 C for 0.5 hours. After resting for 1 hour, it was discharged at 2 C for 10 seconds. The DCIR of the battery at a SOC of 50% was calculated and recorded as D2; battery impedance change rate = (D2 - D1) / D1 * 100%. 5) Impedance change after cycling at room temperature

[0154] The battery was charged to 4.2 V at a constant current of 1 C at room temperature (25 °C), charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C, and then discharged at a constant current of 1 C for 0.5 h. After resting for 1 hour, it was discharged at 2 C for 10 seconds. The DCIR of the battery at a state of charge (SOC) of 50% was calculated and recorded as D3. The battery that completed the 500-cycle performance test at room temperature was charged to 4.2 V at a constant current of 1 C at room temperature (25 °C), charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C, and then discharged at a constant current of 1 C for 0.05 h. After resting for 1 hour, it was discharged at 2 C for 10 seconds. The DCIR of the battery at a SOC of 50% was calculated and recorded as D4. Battery impedance change = (D3 - D4) / D3 * 100%. 6) Acidity of the electrolyte solution after 28 days of storage

[0155] After the electrolyte solution was prepared, it was packaged in aluminum bottles and stored at room temperature (25 °C) for 28 days. A suitable quantity of the electrolyte solution was placed in the glove box, and the moisture content of the electrolyte solution was tested using the low water and triethylamine method with methyl orange as an indicator. 7) Initial Coulomb efficiency

[0156] The battery was first charged at a constant current of 0.1 C at 45 °C for 6.5 h, and the capacity was recorded as D5. Next, it was charged at room temperature at a constant current of 0.1 C to 4.2 V and then charged at a constant voltage of 4.2 V until the cutoff current was 0.05 C. The capacity was recorded as D6. Then, the battery was discharged at 0.2 C to 2.75 V, and the capacity was recorded as D7. Initial Coulomb efficiency = D5 / (D6 + D7) * 100%. Table 1a Thickness change rate after storage at 60 °C (%) Impedance change rate after storage at 60 °C (%) Capacity retention rate after 500 cycles at room temperature (%) Capacity retention rate after 400 cycles at room temperature (%) Example 1a 3,12 2,89 90,68 88,79 Example 2a 12,89 21,12 91,34 78,69 Example 3a 5,99 4,21 93,23 85,99 Example 4a 18,57 31,99 92,47 76,38 Example 5a 6,49 4,94 92,79 84,67 Example 6a 5,99 6,95 89,21 83,98 Example 7a 23,72 43,68 91,84 74,97 Example 8a 7,89 7,82 90,16 80,89 Example 9a 4,34 10,54 88,31 87,79 Example 10a 3,98 3,85 90,79 90,01 Example 11a 4,69 5,03 87,24 84,23 Example 12a 3,01 2,45 91,67 89,15 Comparative example 1a 75,48 50,42 82,45 60,39 Comparative example 2a 131,42 90,27 91,79 10,11 Comparative example 3a 2,46 3,04 69,84 89,01 Comparative example 4a 55,43 42,36 87,46 60,47 Comparative example 5a 2,69 35,81 78,12 74,01 Comparative example 6a 90,49 88,89 91,97 23,24

[0157] Table 1a shows that by adding a specific electrolyte solution to the lithium-ion battery in the examples of the present application, the cycle performance of the lithium-ion battery can be significantly improved at room temperature and at high temperature, and the DCIR of the lithium-ion battery can be reduced.

[0158] Furthermore, examples 1a and 9a demonstrate that by further selecting the concentration of the first lithium salt in the electrolyte solution, the battery's rate of change in impedance and thickness after high-temperature storage can be significantly reduced, while the battery's capacity retention rate after cycling at room temperature and after cycling at high temperature remains almost unchanged. This is because a specific concentration of the lithium salt can result in an electrolyte solution with lower viscosity, thereby improving conductivity and reducing the battery's impedance.

[0159] Examples 1a, 10a, and 11a show that if the electrolyte solution contains a second lithium salt, the battery's thickness change rate and impedance change rate after high-temperature storage can be reduced, and the battery's capacity retention rate after cycling at room temperature and after cycling at high temperature can be improved. Lithium difluorophosphate in the second lithium salt exhibits low impedance and excellent film-forming properties; therefore, lithium difluorophosphate, along with FEC and tris(vinyldimethylsilyl) phosphate, can participate in the formation of the interface film. Based on FEC and tris(vinyldimethylsilyl) phosphate, lithium difluorophosphate reduces the interface impedance, further improving battery performance.Similarly, lithium bis(fluorosulfonyl)imide exhibits good temperature stability and high conductivity and can also reduce battery impedance, improve the conductivity of the electrolyte solution, and thereby improve the electrochemical performance of the battery.

[0160] Examples 1a and 12a demonstrate that by further selecting the concentration of the second lithium salt in the electrolyte solution, the battery's thickness change rate and impedance change rate after high-temperature storage can be reduced, while the battery's capacity retention rate after cycling at room temperature and after cycling at high temperature can be improved. This is because the added second lithium salt, lithium difluorophosphate, participates in the formation of an interface film from the low-impedance electrode to the electrolyte solution. This interface film exhibits stable properties that effectively passivate the electrode interface and enhance the battery's electrochemical performance.

[0161] From Example 1a and the comparative examples 1a and 2a, it can be seen that if the electrolyte solution does not contain tris(vinyldimethylsilyl) phosphate, the capacity retention rate of the battery decreases significantly after high-temperature cycling, and the rate of thickness change and impedance change of the battery increase significantly after high-temperature storage. This is because the FEC gas generation problem is not resolved, leading to severe gas generation within the battery and a significant decrease in battery performance at high temperatures.

[0162] Example 1a and Comparative Example 3a show that by specifically selecting the content of FEC in the electrolyte solution according to the present application, FEC and Tris(vinyldimethylsilyl)phosphate can act synergistically, thereby significantly improving the cycle performance of the battery at room temperature.

[0163] Example 1a and Comparative Example 4a show that a battery with excellent electrochemical performance can only be obtained if the FEC content, the FEC to Tris(vinyldimethylsilyl)phosphate ratio and the Tris(vinyldimethylsilyl)phosphate content are within the specific ranges of the present application.

[0164] Example 1a and comparative examples 5a and 6a show that adjusting the ratio of FEC to Tris(vinyldimethylsilyl)phosphate within a specific range according to the present application effectively improves the electrochemical performance of the battery. Table 1b Acidity of the electrolyte solution after storage for 28 days (HF / ppm) Initial Coulomb efficiency (%) Battery thickness change after storage at 60 °C (%) Capacity retention rate after 400 cycles at high temperature (%) Battery impedance change after 400 cycles (%) Capacity retention rate after 500 cycles at room temperature (%) Battery impedance change after 500 cycles (%) Example 1b 35,98 92,99 5,67 85,88 40,01 91,53 42,34 Example 2b 28,4 92,67 5,23 89,21 45,23 92,07 54,31 Example 3b 24,45 91,87 4,43 90,18 53,23 93,78 58,75 Example 4b 32,77 94,33 5,13 86,13 34,47 91,45 44,05 Example 5b 29,1 93,91 4,54 89,56 44,87 93,12 55,89 Example 6b 23,32 93,13 3,86 93,34 54,69 94,98 62,92 Example 7b 33,98 93,98 5 84,01 38,01 92,02 43,55 Example 8b 29,42 93,24 3,51 88,43 49,23 92,99 54,76 Example 9b 25,65 92,73 2,76 91,96 55,54 93,78 60,62 Example 10b 30,11 93,71 4,97 83,75 38,68 91,7 46,34 Example 11b 26,99 93,06 3,45 87,89 48,76 92,73 59,76 Example 12b 22,24 92,39 2,71 91,14 56,04 93,65 65,43 Example 13b 37,47 93,53 6,88 84,48 45,63 85,14 50,43 Example 14b 34,45 93,36 5,05 86,37 35,21 91,97 36,34 Example 15b 38,92 91,2 2,33 86,84 36,75 85,45 50,89 Example 16b 32,18 92,68 7,89 80,64 44,39 90,01 44,02 Example 17b 20,16 87,02 3,9 80,31 68,41 82,67 67,3 Example 18b 18,89 88,83 3,24 82,41 66,11 87,45 69,99 Example 19b 18,9 89,59 2,13 83,79 64,21 90,16 70,76 Example 20b 17,21 88,11 2,32 80,23 69,98 88,1 71,11 Comparative example 1b 40,87 93,12 130,27 20,5 190,33 90,32 70,77 Comparative example 2b 98 84,89 12,32 75,99 71,34 72,23 79,12 Comparative example 3b 29,67 91,62 50,34 40,67 80,67 91,45 50,66 Comparative example 4b 130 83,77 5,21 74,47 78,23 69,61 80,4

[0165] Table 1b shows that by adding a specific electrolyte solution to the lithium-ion battery in the examples of the present application, the capacity utilization rate of the lithium-ion battery can be significantly improved, the cycle performance of the lithium-ion battery can be increased at room temperature and high temperature, and the impedance of the lithium-ion battery and the acidity of the electrolyte solution can be reduced.

[0166] Furthermore, as can be seen from Examples 1b and 13b, by further selecting the concentration of the first lithium salt in the electrolyte solution, the cycle performance of the lithium-ion battery at room temperature can be significantly improved, the rate of change of impedance of the lithium-ion battery after cycling at high temperature can be reduced, and the acidity of the electrolyte solution, the initial Coulomb efficiency, and the cycle performance of the lithium-ion battery at high temperature remain essentially unchanged. By further selecting the lithium salt in the present application, a lower viscosity electrolyte solution can be obtained, and the impedance of the battery can be reduced; moreover, the synergistic effect between the isocyanate and the tris(vinyldimethylsilyl) phosphate not only suppresses side reactions in the electrolyte solution but also strengthens the interface film formed by FEC.The battery's cycle performance at room temperature is significantly improved, and this improvement has essentially no negative impact on the battery's initial Coulomb efficiency and high-temperature performance.

[0167] As can be seen from Example 1b and Example 14b, when the electrolyte solution contains both the first and second lithium salts, the resulting electrolyte solution has a lower acidity and can further improve the initial Coulomb efficiency, the high-temperature cycle life, and the room-temperature cycle life of the battery, and can reduce the rate of impedance change of the battery after high-temperature cycling. This is because, after the addition of the second lithium salt, lithium difluorophosphate, it can participate in the formation of an interface film from a low-impedance electrode to the electrolyte solution.This interface film exhibits stable properties, effectively passivates the electrode interface, and further enhances the interface film formed by FEC isocyanate tri(vinyldimethylsilyl) phosphate, thereby reducing electrolyte solution degradation on the electrode surface and the deposition of byproducts. Battery impedance growth is effectively suppressed, ultimately improving the battery's electrochemical performance.

[0168] Examples 1b to 3b compared to Example 17b, Examples 4b to 6b compared to Example 18b, Examples 7b to 9b compared to Example 19b, and Examples 10b to 12b compared to Example 20b show that by further selecting the concentration of the isocyanate compound in the electrolyte solution, the initial Coulomb efficiency, the high-temperature cycle life, and the room-temperature cycle life can be significantly improved, and the battery's impedance change rate after cycling at room temperature and the battery's impedance change rate after cycling at high temperature can be reduced. As the isocyanate concentration increases, residual water and RF are removed more thoroughly from the battery, effectively preventing lithium salt degradation and RF damage to the electrode material.Furthermore, the interface film, which forms on the surface of the silicon-based material, becomes more complete and resistant to high temperature fluctuations with the addition of more isocyanate, effectively suppressing side reactions in the battery. The presence of tris(vinyldimethylsilyl) phosphate can generate low-impedance phosphate ester compounds to build the interface film along with the isocyanate. The problem of increased battery impedance caused by the increased amount of isocyanate is also suppressed. The side effects of isocyanate are significantly inhibited, and the electrochemical performance of the battery is considerably improved.

[0169] Examples 1b and 15b demonstrate that further selecting the FEC content in the electrolyte solution can effectively improve the battery's cycle life at room temperature, reduce the impedance change rate after cycling at room temperature, and leave the initial Coulomb efficiency and cycle life at high temperature almost unchanged. This is because, as the FEC content is further selected, the interface film on the electrode surface becomes relatively complete, and the addition of tris(vinyldimethylsilyl) phosphate and the isocyanate to this interface film significantly enhances the battery's cycle life at room temperature.Furthermore, the increased FEC content, with tris(vinyldimethylsilyl) phosphate inhibiting FEC gas generation and isocyanate eliminating side reactions, has no adverse effect on the battery's performance at high temperature; instead, the cycle performance at room temperature is significantly enhanced.

[0170] Examples 1b and 16b show that further selection of the tris(vinyldimethylsilyl) phosphate content in the electrolyte solution slightly improves the initial Coulomb efficiency and cycle life of the battery at room temperature and significantly increases the battery's cycle life at high temperatures. Increasing the tris(vinyldimethylsilyl) phosphate content significantly prevents FEC gas generation, considerably reduces side reactions on the electrode surface, and substantially improves the battery's high-temperature performance. Furthermore, the low-impedance components generated by tris(vinyldimethylsilyl) phosphate also mitigate the problem of increased impedance caused by the isocyanate. Finally, the initial Coulomb efficiency and cycle life of the battery at room temperature are also improved.

[0171] Ultimately, it is understood that the foregoing examples are used only to illustrate the technical solutions of the present application and not to limit them; although the present application has been described in detail with reference to the foregoing examples, the person skilled in the art understands that the technical solutions described in the foregoing examples may still be modified or some or all of the technical features may be replaced; and these modifications or replacements do not cause the nature of the corresponding technical solutions to differ from the scope of the technical solutions of the examples of the present application.

Claims

[1] Electrolyte solution comprising fluoroethylene carbonate and tris(vinyldimethylsilyl) phosphate; wherein, based on a total mass of the electrolyte solution, the mass fraction of fluoroethylene carbonate is in the range of 8% to 15%, and the mass fraction of tris(vinyldimethylsilyl) phosphate is in the range of 0.5% to 2%; and The mass ratio of tris(vinyldimethylsilyl) phosphate to fluoroethylene carbonate is in the range of 1:8 to 1:

30. [2] Electrolyte solution according to claim 1, wherein the electrolyte solution further comprises a first lithium salt with a mass fraction in the range of 6% to 14% and the first lithium salt is lithium hexafluorophosphate. [3] Electrolyte solution according to claim 2, wherein the electrolyte solution further comprises a second lithium salt with a mass fraction in the range of 0.5% to 8%; and the second lithium salt is selected from the group consisting of lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide and a combination thereof. [4] Electrolyte solution according to claim 3, wherein the second lithium salt is lithium bis(fluorosulfonyl)imide and / or lithium difluorophosphate. [5] Electrolyte solution according to claim 4, wherein a mass fraction of the lithium bis(fluorosulfonyl)imide is in the range of 1% to 8% based on a total mass of the electrolyte solution; and / or a mass fraction of the lithium difluorophosphate is in the range of 0.5% to 1% based on a total mass of the electrolyte solution. [6] Electrolyte solution according to any one of claims 1 to 5, wherein the electrolyte solution further comprises a solvent with a mass fraction in the range of 65% to 86%. [7] Electrolyte solution according to claim 6, wherein the electrolyte solution further comprises a solvent with a mass fraction in the range of 72% to 76%. [8] Electrolyte solution according to claim 6 or 7, wherein the solvent comprises a cyclic carbonate and an acyclic carbonate. [9] Electrolyte solution according to claim 8, wherein the mass ratio of the cyclic carbonate to the acyclic carbonate is in the range of (2 to 3):(5 to 7). [10] Electrolyte solution according to any one of claims 1 to 9, wherein the electrolyte solution further comprises a further additive with a mass fraction in the range of 0.003% to 4%; and the further additive is selected from the group consisting of ethylene sulfite, 1,4-butane sultone, prop-1-ene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, maleic anhydride, tris(trimethylsilyl)borate, difluoroethylene carbonate, vinylene carbonate, triphenyl phosphite and a combination thereof. [11] Electrolyte solution according to claim 10, wherein the electrolyte solution further comprises the additional additive with a mass fraction in the range of 0.5% to 3.8%. [12] Electrolyte solution comprising fluoroethylene carbonate, tris(vinyldimethylsilyl) phosphate and an isocyanate compound. [13] Electrolyte solution according to claim 12, wherein the mass fraction of the fluoroethylene carbonate is in the range of 8% to 20% based on a total mass of the electrolyte solution; and / or a mass fraction of tris(vinyldimethylsilyl) phosphate in the range of 0.5% to 2% based on a total mass of the electrolyte solution; and / or The mass fraction of the isocyanate compound is in the range of 0.1% to 0.8% based on the total mass of the electrolyte solution. [14] Electrolyte solution according to claim 12 or 13, wherein the isocyanate compound is selected from the group consisting of hexamethylene diisocyanate, 1,4-phenylene diisocyanate, triisocyanatomethylsilane, toluene-2,5-diisocyanate, 3-(isocyanatopropyl)trimethoxysilane, 3-(isocyanatopropyl)triethoxysilane, 3-(isocyanatopropyl)dimethoxymethylsilane, 3-(isocyanatopropyl)diethoxymethylsilane, 3-(isocyanatopropyl)methoxydimethylsilane, 1-(isocyanatomethyl)trimethoxysilane, 1-(isocyanatomethyl)triethoxysilane, 1-(isocyanatomethyl)dimethoxymethylsilane and a combination thereof. [15] Electrolyte solution according to claim 14, wherein the isocyanate compound is selected from the group consisting of hexamethylene diisocyanate, 1,4-phenylene diisocyanate, triisocyanatomethylsilane and a combination thereof. [16] Electrolyte solution according to any one of claims 12 to 15, wherein the electrolyte solution further comprises a lithium salt with a mass fraction in the range of 12.5% ​​to 17%. [17] Electrolyte solution according to claim 16, wherein the lithium salt comprises a first lithium salt having a mass fraction in the range of 6% to 15% and the first lithium salt is lithium hexafluorophosphate. [18] Electrolyte solution according to claim 17, wherein the lithium salt further comprises a third lithium salt and the third lithium salt is lithium bis(fluorosulfonyl)imide and / or lithium difluorophosphate. [19] Electrolyte solution according to claim 18, wherein a mass fraction of the lithium bis(fluorosulfonyl)imide is in the range of 1% to 6% based on a total mass of the electrolyte solution; and / or a mass fraction of the lithium difluorophosphate is in the range of 0.5% to 1% based on a total mass of the electrolyte solution. [20] Electrolyte solution according to any one of claims 12 to 19, wherein the electrolyte solution further comprises a solvent; the solvent is selected from the group consisting of ethylene carbonate and propylene carbonate and a total mass fraction of ethylene carbonate and propylene carbonate is in the range of 17.46% to 23.22% based on a total mass of the electrolyte solution; and / or The solvent consists of at least two solvents selected from the group comprising ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate, and the total mass fraction of the at least two solvents of ethyl methyl carbonate, diethyl carbonate and dimethyl carbonate is in the range of 40.74% to 54.18% based on the total mass of the electrolyte solution. [21] Electrolyte solution according to any one of claims 12 to 20, wherein the electrolyte solution further comprises a further additive with a mass fraction in the range of 0.03% to 4%; and the further additive is selected from the group consisting of ethylene sulfite, 1,4-butane sultone, prop-1-ene-1,3-sultone, 1,3-propane sultone, ethylene sulfate, maleic anhydride, tris(trimethylsilyl)borate, difluoroethylene carbonate, vinylene carbonate and a combination thereof. [22] Electrolyte solution according to claim 21, wherein the electrolyte solution further comprises the additional additive with a mass fraction in the range of 0.5% to 3.8%. [23] Battery comprising the electrolyte solution according to any one of claims 1 to 22.