Non-aqueous electrolyte, lithium ion battery, and electronic device
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-04-09
- Publication Date
- 2026-08-13
Smart Images
Figure PCTCN2025088146-APPB-I100001 
Figure PCTCN2025088146-APPB-I100002 
Figure PCTCN2025088146-APPB-I100003
Abstract
Description
Non-aqueous electrolytes, lithium-ion batteries and electronic devices Technical Field
[0001] This application relates to the field of energy storage, specifically to a non-aqueous electrolyte, a lithium-ion battery, and an electronic device. Background Technology
[0002] In recent years, information-related or communication equipment (small devices such as personal computers and mobile phones), as well as large-scale equipment such as energy storage systems for applications requiring high energy density, electric vehicles, hybrid vehicles, fuel cell vehicles auxiliary power supplies, and energy storage systems for energy-intensive applications have received considerable attention. As one of the potential candidates, non-aqueous electrolyte batteries such as lithium-ion batteries and sodium-ion batteries have been actively developed.
[0003] While various types of non-aqueous electrolyte batteries have been put into practical use, their characteristics are not yet fully satisfactory for all applications. Especially in automotive applications such as electric vehicles, where high input / output characteristics are required even in hot conditions, improved high-temperature performance is crucial. Furthermore, the ability to minimize the increase in internal resistance when subjected to repeated charging and discharging at high temperatures is also essential.
[0004] As a means to improve the high-temperature characteristics and battery performance under repeated charge-discharge cycles of non-aqueous electrolyte batteries, the optimization of various battery components, primarily the active materials of the positive and negative electrodes, has been studied. Non-aqueous electrolyte technologies are no exception, proposing the use of various additives to suppress the degradation caused by the decomposition of non-aqueous electrolytes on the surfaces of the active positive and negative electrodes. Summary of the Invention
[0005] The problem the invention aims to solve
[0006] The non-aqueous electrolyte batteries disclosed in existing technical literature that use non-aqueous electrolytes cannot fully solve the problems of electrode gas generation, IV resistance, and cycle performance at high temperatures, and there is room for improvement.
[0007] Solution for solving the problem
[0008] In view of the above-mentioned problems, the inventors of this application have conducted in-depth research and disclosed a non-aqueous electrolyte for lithium-ion batteries. This non-aqueous electrolyte is a non-aqueous electrolyte in which lithium salts are dissolved in a non-aqueous solvent. The non-aqueous electrolyte contains specific amounts of lithium difluorophosphate, 1,3,6-hexanetricarbonyl, 1,2,3-tris(2-cyanoethoxy)propane, and boron-containing lithium salt additives. The total content of lithium difluorophosphate and 1,2,3-tris(2-cyanoethoxy)propane in the non-aqueous electrolyte is set within a specific range, and the total content of 1,3,6-hexanetricarbonyl and boron-containing lithium salt additives is set within a specific range. By using this non-aqueous electrolyte, not only can the gas generation of the lithium-ion battery electrodes be improved, but also the IV resistance can be suppressed, significantly improving the high-temperature cycle performance of the lithium-ion battery.
[0009] That is, this application provides the following technical solutions (1) to (3), specifically as follows:
[0010] (1) A non-aqueous electrolyte for lithium-ion batteries, comprising a non-aqueous electrolyte in which lithium salts are dissolved in a non-aqueous solvent, wherein, based on the total mass of the non-aqueous electrolyte, the non-aqueous electrolyte further contains...
[0011] (I) Lithium difluorophosphate with a content of 0.02% by mass or more and 3% by mass or less
[0012] (II) 1,3,6-hexanetrionitrile in a content of 0.4% by mass or more and 4% by mass.
[0013] (III) 1,2,3-tris(2-cyanoethoxy)propane in a content of 0.4% by mass or more and 5% by mass.
[0014] (IV) Boron-containing lithium salt additives with a content of 0.01% by mass or more and 3% by mass or less.
[0015] The total content of (I) and (III) is 0.96% by mass or more and 5.56% by mass or less, and the total content of (II) and (IV) is 0.45% by mass or more and 4.6% by mass or less.
[0016] (2) A lithium-ion battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte is the aforementioned non-aqueous electrolyte; wherein the positive electrode comprises lithium cobalt oxide having at least three elements selected from aluminum, magnesium, titanium, zirconium, lanthanum, iridium, cerium, and tungsten; or wherein the negative electrode comprises at least one selected from lithium metal, lithium alloy, carbon material capable of intercalating and deintercalating lithium, elemental tin, tin compounds, elemental silicon, silicon oxide compounds, silicon carbide compounds, and lithium titanate compounds as a negative electrode active material.
[0017] (3) An electronic device comprising the lithium-ion battery described above.
[0018] The effects of the invention
[0019] By using this non-aqueous electrolyte, not only can the gas generation of the lithium-ion battery electrodes be improved, but also the IV resistance can be suppressed, significantly improving the high-temperature cycle performance of the lithium-ion battery. Detailed Implementation
[0020] Embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application. Unless otherwise expressly stated, the terms used in this application have the meanings described below.
[0021] Non-aqueous electrolyte
[0022] The non-aqueous electrolyte for lithium-ion batteries disclosed in this application is a non-aqueous electrolyte in which lithium salts are dissolved in a non-aqueous solvent. Based on the total mass of the non-aqueous electrolyte, the non-aqueous electrolyte also contains...
[0023] (I) Lithium difluorophosphate with a content of 0.02% by mass or more and 3% by mass or less
[0024] (II) 1,3,6-hexanetrionitrile in a content of 0.4% by mass or more and 4% by mass.
[0025] (III) 1,2,3-tris(2-cyanoethoxy)propane in a content of 0.4% by mass or more and 5% by mass.
[0026] (IV) Boron-containing lithium salt additives with a content of 0.01% by mass or more and 3% by mass or less;
[0027] The total content of (I) and (III) is 0.96% by mass or more and 5.56% by mass or less, and the total content of (II) and (IV) is 0.45% by mass or more and 4.6% by mass or less.
[0028] The non-aqueous electrolyte contains (I) lithium difluorophosphate, (II) 1,3,6-tris(2-cyanoethoxy)propane, (III) 1,2,3-tris(2-cyanoethoxy)propane, and (IV) boron-containing lithium salt additives. More importantly, the total content of lithium difluorophosphate and 1,2,3-tris(2-cyanoethoxy)propane is set within a specific range, and the total content of 1,3,6-tris(2-cyanoethoxy)propane and boron-containing lithium salt is set within a specific range. Although the reason for improving the IV resistance characteristics of lithium-ion batteries and suppressing gas generation is not clear, it is believed that the components (I) to (IV) of the non-aqueous electrolyte react with the active part on the positive electrode surface during the first charge-discharge cycle, forming a stable coating on the positive electrode surface. It is speculated that the coating inhibits the damage of the electrolyte to the positive electrode during charge-discharge cycles and reduces the consumption of active lithium by coating decomposition and regeneration. As a result, by suppressing the increase in electrode interface resistance, it can not only improve the amount of gas generated at the electrode of the lithium-ion battery, but also suppress IV resistance, and significantly improve the high-temperature cycle performance of the lithium-ion battery.
[0029] Specifically, the (IV) boron-containing lithium salt additive is selected from lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium tetracyanoborate, lithium tetra(trifluoromethyl)borate, lithium (trifluoromethyl)trifluoroborate, lithium bis(trifluoromethyl)difluoroborate, lithium pentafluoroethyltrifluoroborate, lithium dicyanoborate borate, lithium dicyanoborate, lithium bis(malonate)borate, lithium (2-fluoromalonate)difluoroborate, lithium malonate oxalate borate, lithium bis(salicylate)borate, lithium bis(catechol)borate, and methoxytricyanoborate. At least one of lithium, lithium ethoxytricyanoborate, lithium tetramethoxyborate, lithium tetraethoxyborate, lithium tetra(trifluoromethoxy)borate, lithium tetra(2,2,2-trifluoroethoxy)borate, lithium polytetra(hydroquinoneoxy)borate, lithium di(trifluoroborate)sulfate, lithium difluoroborate, lithium methane disulfonate difluoroborate, lithium difluorophosphoryloxytrifluoroborate, lithium di(difluorophosphoryloxy)difluoroborate, or lithium tetra(difluorophosphoryloxy)borate, results in excellent stability of the formed coating, further enhancing battery performance. One or more boron-containing lithium salt additives (IV) can be used.
[0030] Specifically, from the viewpoint of improving the IV resistance characteristics of lithium-ion batteries, based on the total mass of the non-aqueous electrolyte, the content of lithium difluorophosphate is 0.02% by mass or more, preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and more preferably 0.11% by mass or more.
[0031] Furthermore, from the viewpoint of suppressing the amount of gas generated by the electrode, the upper limit of the content of lithium difluorophosphate is 3% by mass or less, preferably 2.6% by mass or less, more preferably 1.3% by mass or less, even more preferably 0.85% by mass or less, and particularly preferably 0.56% by mass or less.
[0032] In some embodiments, the lithium difluorophosphate content is set as a1% by mass, where a1 is 0.02, 0.03, 0.05, 0.07, 0.11, 0.13, 0.16, 0.23, 0.32, 0.35, 0.48, 0.56, 0.67, 0.85, 1.1, 1.3, 2, 2.6, 3, or within a range consisting of any two of the above values. For example, 0.02 to 0.11, 0.03 to 0.11, 0.05 to 0.23, 0.11 to 0.56, 0.32 to 1.3, 0.48 to 2.6, 0.56 to 3, 0.85 to 3, 0.32 to 0.85, 0.85 to 2.6. When within the above ranges, it helps to further suppress the amount of gas generated at the electrode.
[0033] Specifically, from the viewpoint of improving the high-temperature cycling performance of lithium-ion batteries, the content of 1,2,3-tris(2-cyanoethoxy)propane is 0.4% by mass or more, preferably 0.6% by mass or more, and more preferably 1.2% by mass or more, based on the total mass of the non-aqueous electrolyte.
[0034] Furthermore, as an upper limit for the content of 1,2,3-tris(2-cyanoethoxy)propane, from the viewpoint of suppressing the amount of gas generated by the electrode, the content of 1,2,3-tris(2-cyanoethoxy)propane is 5% by mass or less, preferably 4.8% by mass or less, more preferably 3.5% by mass or less, even more preferably 2.9% by mass or less, and particularly preferably 2.6% by mass or less.
[0035] In some embodiments, the content of 1,2,3-tris(2-cyanoethoxy)propane is set as a3% by mass, where a3 is 0.4, 0.6, 1.2, 1.7, 1.8, 1.9, 2.1, 2.6, 2.9, 3.5, 4.8, 5, or within a range of any two of the above values. For example, 0.4 to 2.1, 0.6 to 1.9, 1.2 to 3.5, 1.7 to 2.9, 1.8 to 2.6, 1.9 to 4.8, 0.4 to 1.9, when within the above ranges, helps to further improve high-temperature cycling.
[0036] Furthermore, from the viewpoint of suppressing the amount of gas generated by the electrode, the total content of lithium difluorophosphate and 1,2,3-tris(2-cyanoethoxy)propane is 0.96% by mass or more, preferably 1.76% by mass or more, based on the total mass of the non-aqueous electrolyte.
[0037] Furthermore, from the viewpoint of improving electrochemical properties under high-temperature conditions, the upper limit of the total content of lithium difluorophosphate and 1,2,3-tris(2-cyanoethoxy)propane is 5.56% by mass or less, preferably 5.36% by mass or less.
[0038] In some embodiments, the total content of lithium difluorophosphate and 1,2,3-tris(2-cyanoethoxy)propane is set as a1+a3 mass%, where a1+a3 is 0.96, 1.16, 1.76, 1.82, 1.83, 1.85, 1.91, 2.03, 2.12, 2.26, 2.28, 2.36, 2.65, 2.66, 3.1, 3.16, 3.46, 4.05, 4.4, 4.8, 5.36, 5.56, or within a range consisting of any two of the above values. For example, 0.96 to 3.16, 1.16 to 2.65, 1.76 to 2.36, 1.82 to 4.4, 1.85 to 4.8, 1.91 to 5.36, 1.16 to 3.46, 2.03 to 4.4, and 2.12 to 5.36, when within the above ranges, help to further suppress the amount of gas generated by the electrode.
[0039] Specifically, from the viewpoint of improving the high-temperature cycling performance of lithium-ion batteries, the content of 1,3,6-hexanetrionitrile is 0.4% by mass or more, preferably 0.8% by mass or more, and more preferably 1.2% by mass or more, based on the total mass of the non-aqueous electrolyte.
[0040] Furthermore, as an upper limit for the content of 1,3,6-hexanetrionitrile, from the viewpoint of suppressing the amount of gas generated by the electrode, the content of 1,3,6-hexanetrionitrile is 4% by mass or less, preferably 3.8% by mass or less, more preferably 3.4% by mass or less, even more preferably 3.1% by mass or less, and particularly preferably 2.6% by mass or less.
[0041] In some embodiments, the content of 1,3,6-trimethylhexanenitrile is set as a2% by mass, where a2 is 0.4, 0.8, 1.2, 1.6, 1.8, 2.1, 2.6, 3.1, 3.4, 3.8, 4, or within a range of any two of the above values. For example, 0.4 to 2.6, 0.8 to 3.8, 1.2 to 3.4, 1.6 to 3.4, 0.8 to 2.6, 1.2 to 4, 0.4 to 1.8. When within the above ranges, it helps to further suppress the amount of gas generated at the electrode.
[0042] Specifically, from the viewpoint of improving the IV resistance characteristics of lithium-ion batteries, based on the total mass of the non-aqueous electrolyte, the content of boron-containing lithium salt additive is 0.01% by mass or more, preferably 0.03% by mass or more, more preferably 0.07% by mass or more, and even more preferably 0.12% by mass or more.
[0043] Furthermore, from the viewpoint of suppressing the amount of gas generated by the electrode, the upper limit of the content of boron-containing lithium salt additive is 3% by mass or less, preferably 2.5% by mass or less, more preferably 2.1% by mass or less, even more preferably 1.8% by mass or less, and particularly preferably 1.2% by mass or less.
[0044] In some embodiments, the content of the boron-containing lithium salt additive is set as a4% by mass, where a4 is 0.01, 0.03, 0.05, 0.07, 0.08, 0.1, 0.12, 0.15, 0.19, 0.21, 0.27, 0.3, 0.35, 0.4, 0.45, 0.51, 0.6, 0.7, 0.79, 0.9, 1, 1.2, 1.5, 1.8, 2, 2.5, 3, or within a range consisting of any two of the above values. For example, values of 0.01 to 0.12, 0.02 to 0.21, 0.1 to 0.45, 0.51 to 2, 0.6 to 3, 1.2 to 2.5, 0.1 to 0.8, 0.79 to 1.8, 1.5 to 3, 0.12 to 0.45, and 0.35 to 0.79, when within the above ranges, help to further improve the IV resistance characteristics.
[0045] Furthermore, from the viewpoint of suppressing the amount of gas generated by the electrode, the total content of 1,3,6-hexanetrionitrile and boron-containing lithium salt additive is 0.45% by mass or more, preferably 0.85% by mass or more, based on the total mass of the non-aqueous electrolyte.
[0046] Furthermore, from the viewpoint of improving electrochemical properties under high-temperature conditions, the upper limit of the total content of 1,3,6-hexanetrionitrile and boron-containing lithium salt additive is 4.5% by mass or less, preferably 3.7% by mass or less.
[0047] In some embodiments, the total content of 1,3,6-hexamethylenetricarbonyl nitrile and boron-containing lithium salt additive is a2+a4% by mass, where a2+a4 is 0.45, 0.85, 1.25, 1.61, 1.65, 1.79, 1.85, 1.87, 1.95, 2.11, 2.15, 2.39, 2.52, 2.65, 2.8, 3.15, 3.4, 3.45, 3.7, 3.85, 4.05, 4.1, 4.5, or within a range consisting of any two of the above values. For example, 0.45 to 2.8, 0.85 to 3.7, 1.25 to 4.1, 1.95 to 3.15, 0.85 to 3.15, 2.11 to 4.1, 2.15 to 4.5. When within the above ranges, it helps to further suppress the amount of gas generated by the electrode.
[0048] In addition, the non-aqueous electrolyte may also include other nitrile compounds. The inventors also unexpectedly discovered that other nitrile compounds can reduce the resistance of the reaction between the aforementioned substances (I) to (IV) and the active part of the positive electrode surface to form a coating, improve lithium-ion charge transport, further suppress the amount of gas generated by the electrode and improve high-temperature performance.
[0049] Other nitrile compounds include at least one of succinic anion, adiponitrile, ethylene glycol di(propionitrile) ether, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, or 1,2,5-tris(cyanoethoxy)pentane.
[0050] The aforementioned nitrile compounds may be only one type or two or more types. For example, they include succinic anion and adiponitrile; or succinic anion and ethylene glycol di(propionitrile) ether; or adiponitrile and ethylene glycol di(propionitrile) ether.
[0051] Specifically, from the viewpoint of suppressing the amount of gas generated by the electrode, based on the total mass of the non-aqueous electrolyte, the content of other nitrile compounds is 0.3% by mass or more, preferably 0.6% by mass or more, more preferably 0.9% by mass or more, and more preferably 1.4% by mass or more.
[0052] Furthermore, as an upper limit for the content of other nitrile compounds, from the viewpoint of suppressing the amount of gas generated by the electrode, the content of other nitrile compounds is 8% by mass or less, preferably 7.9% by mass or less, more preferably 7.1% by mass or less, even more preferably 6.2% by mass or less, and particularly preferably 5.3% by mass or less.
[0053] In some embodiments, the total content of other nitrile compounds is b% by mass, where b is 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.4, 1.5, 2, 2.5, 3, 3.5, 3.9, 4, 4.6, 5.3, 6.2, 7.1, 7.9, 8, or within a range consisting of any two of the above values. For example, 0.3 to 5.3, 0.6 to 4.6, 0.9 to 3.9, 0.4 to 2, 0.45 to 4.6, 0.8 to 2.5, 1.4 to 3.9, 2.5 to 8, 0.9 to 6.2, 0.45 to 5.3, 0.6 to 1.4. When within the above ranges, it helps to further suppress the amount of gas generated by the electrode.
[0054] In addition, the non-aqueous electrolyte may also include other additives. The inventors also unexpectedly discovered that other additives can inhibit the decomposition and regeneration of the coating formed by the reaction of the aforementioned (I) to (IV) substances with the active part of the positive electrode surface during the charging and discharging process, thereby further improving the IV resistance and suppressing the amount of gas generated by the electrode.
[0055] Other additives include at least one of lithium monofluorophosphate, fluoroethylene carbonate, vinylene carbonate, lithium fluorosulfonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfate, 1,3-propanediol cyclosulfonate, fluorobenzene, cyclohexylbenzene, biphenyl, tris(trimethylsilane) phosphate, or tris(trimethylsilane) borate.
[0056] The other additives mentioned above may be one or more. For example, they may include vinyl sulfate and lithium fluorosulfonate; or lithium monofluorophosphate and fluoroethylene carbonate; or lithium monofluorophosphate and lithium fluorosulfonate; or lithium monofluorophosphate and 1,3-propanesulfonate lactone; or lithium fluorosulfonate and 1,3-propanesulfonate lactone; or vinyl sulfate and 1,3-propanesulfonate lactone; or tris(trimethylsilane) phosphate and vinyl sulfate; or tris(trimethylsilane) borate and vinyl sulfate.
[0057] Specifically, from the viewpoint of suppressing the amount of gas generated by the electrode, based on the total mass of the non-aqueous electrolyte, the content of other additives is 0.3% by mass or more, preferably 0.9% by mass or more, more preferably 1.6% by mass or more, and more preferably 2.8% by mass or more.
[0058] Furthermore, as an upper limit for the content of other additives, from the viewpoint of suppressing the amount of gas generated by the electrode, the content of other additives is 10% by mass or less, preferably 9.7% by mass or less, more preferably 8.2% by mass or less, even more preferably 7.1% by mass or less, and particularly preferably 6.7% by mass or less.
[0059] In some embodiments, the total content of other additives is c% by mass, where c is 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 1.6, 2, 2.5, 2.8, 3, 3.5, 3.9, 4, 4.5, 5, 5.5, 6, 6.5, 7.1, 7.5, 8.2, 8.6, 9, 9.3, 9.7, 10, or within a range consisting of any two of the above values. For example, 0.3 to 18.2, 0.45 to 7.5, 0.6 to 9.7, 5.5 to 9.7, 6 to 8.6, 2.8 to 6.5, 1 to 6.5, 0.7 to 7.1, 1.5 to 9.3, 0.45 to 3.9, 0.7 to 4.5. When within the above ranges, it helps to further suppress the amount of gas generated by the electrode.
[0060] The lithium salts used in the non-aqueous electrolyte of this application include lithium hexafluorophosphate. Based on the total mass of the non-aqueous electrolyte, the content of lithium hexafluorophosphate is 9-15% by mass, preferably 9-13% by mass, and more preferably 9-12% by mass. By setting it within the above content range, the IV resistance characteristics and high-temperature cycle characteristics can be improved more balancedly.
[0061] The non-aqueous electrolyte of this application may further contain any non-aqueous solvent known in the prior art that can be used as a solvent for non-aqueous electrolytes. For example, cyclic carbonates, linear carbonates, cyclic carboxylates, linear carboxylates, cyclic ethers, linear ethers, phosphorus-containing organic solvents, and sulfur-containing organic solvents. Linear carboxylates are preferred, such as ethyl acetate, ethyl fluoroacetate, ethyl propionate, and propyl propionate.
[0062] Lithium-ion battery
[0063] The lithium-ion battery of this application includes a positive electrode, a negative electrode, and the above non-aqueous electrolyte in which a lithium salt is dissolved in a non-aqueous solvent. Components such as the positive electrode and negative electrode other than the non-aqueous electrolyte can be used without particular limitation.
[0064] For example, as the positive electrode active material for lithium-ion batteries, a composite metal oxide containing one or more selected from the group consisting of cobalt, manganese, and nickel and lithium, or a lithium-containing olivine-type phosphate containing one or more selected from iron, cobalt, nickel, and manganese is used. These positive electrode active materials can be used alone or in combination of two or more.
[0065] As such a lithium composite metal oxide, for example, those selected from LiCoO2, LiMn2O4, LiNiO2, LiCo 1-x Ni x O2(0.01 < x < 1), LiNi x Mn y Co z O2(x + y + z = 1), solid solutions of Li2MnO3 and LiMO2 (M is a transition metal such as Co, Ni, Mn, Fe, etc.), LiNi 1 / 2 Mn 3 / 2 O4, LiFePO4, LiMnPO4, and LiMn 1-x FexPO4(0.01 < x < 1), etc. One or more of them are more preferably two or more. A part of these composite metal oxides with lithium or lithium-containing olivine-type phosphates can be substituted with other elements, or a part of cobalt, nickel, manganese, and iron can be substituted with one or two or more elements selected from Co, Mn, Ni, Mg, Al, B, Ti, V, Nb, Cu, Zn, Mo, Ca, Sr, W, and Zr, or coated with a compound or carbon material containing these other elements.
[0066] For example, the positive electrode comprises lithium cobalt oxide having at least three heteroelements selected from aluminum, magnesium, titanium, zirconium, lanthanum, iridium, cerium, and tungsten. From the viewpoint of improving the IV resistance characteristics of lithium-ion batteries, based on the mass of lithium cobalt oxide, the content of any one of the heteroelements is preferably 0.01% by mass or more, preferably 0.03% by mass or more, and more preferably 0.05% by mass or more. Furthermore, as an upper limit for the content of heteroelements, the content of any one of the heteroelements is 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.3% by mass or less, further preferably 0.15% by mass or less, and particularly preferably 0.1% by mass or less.
[0067] If lithium composite metal oxides that operate at high charging voltages are used, their electrochemical properties are prone to decline at high temperatures due to reactions with non-aqueous electrolytes during charging. However, in the lithium-ion battery described in this application, the decline in these electrochemical properties can be suppressed.
[0068] From the viewpoint of high voltage, the positive electrode potential is preferably 4.4V (vs. Li / Li+) or higher, more preferably 4.5V (vs. Li / Li+) or higher, and particularly preferably 4.6V (vs. Li / Li+) or higher.
[0069] There are no particular restrictions on the conductive agent used in the positive electrode, as long as it is an electron-conducting material that does not cause chemical changes. Examples include natural graphite (flake graphite, etc.), artificial graphite, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal cracking black. Furthermore, graphite and carbon black can be appropriately mixed. The preferred amount of conductive agent added to the positive electrode mixture is 1-10% by mass, particularly preferably 1.5-5% by mass.
[0070] The positive electrode can be manufactured as follows: The above-mentioned positive electrode active material is mixed with conductive agents such as acetylene black and carbon black, and binders such as polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, copolymer of styrene and butadiene, and carboxymethyl cellulose. A high-boiling-point solvent such as 1-methyl-2-pyrrolidone is added and the mixture is kneaded to form a positive electrode slurry. This slurry is then coated onto aluminum foil or similar material of the current collector, dried, and pressurized to form a positive electrode slurry layer.
[0071] The density of the positive electrode, excluding the current collector, is typically 3.5 g / cm³. 3 In order to further improve the battery capacity, a value of 3.8 g / cm³ is preferred. 3 The above, more preferably 4g / cm 3 The above is further optimized to 4.1 g / cm³. 3 That's all. Furthermore, as an upper limit, 4.6 g / cm³ is preferred. 3 the following.
[0072] As negative electrode active materials for lithium-ion batteries, the following negative electrode active materials can be used alone or in combination: lithium metal or lithium alloy, and carbon materials capable of intercalating and deintercalating lithium (easily graphitized carbon, difficult-to-graphitize carbon with an interfacial spacing of 0.37 nm or more on the (002) facets, graphite with an interfacial spacing of 0.34 nm or less on the (002) facets, etc.), tin (elemental), SnO x (1≤x<2) Tin compounds, silicon (elemental), SiO x (1≤x<2) and other silicon oxide compounds, silicon carbide compounds, or Li4Ti5O 12 Lithium titanate compounds, etc.
[0073] Regarding the lithium-ion intercalation and deintercalation capabilities, highly crystalline carbon materials such as artificial graphite or natural graphite are preferred. More preferably, carbon materials with a graphitic crystal structure having a lattice plane (002) spacing (d002) of 0.340 nm or less, particularly 0.335–0.337 nm, are preferred. From the viewpoint of improving energy density, silicon oxide compounds, silicon carbide compounds, or mixtures thereof with graphite are preferred.
[0074] The negative electrode can be made as follows: using the same conductive agent, binder, and high-boiling-point solvent as the positive electrode to make a negative electrode slurry, then coating it onto the copper foil of the current collector, drying it, and pressing it to form a negative electrode slurry layer.
[0075] The density of the negative electrode, excluding the current collector, is typically 1.1 g / cm³. 3 In order to further improve the battery capacity, a value of 1.5 g / cm³ is preferred. 3 The above, more preferably 1.7 g / cm³ 3 That's all. Furthermore, as an upper limit, 2.2 g / cm³ is preferred. 3 the following.
[0076] There are no particular restrictions on the structure of lithium batteries; they can be coin-shaped, cylindrical, prismatic, or pouch batteries with single or multiple layers of separators.
[0077] There are no particular restrictions on the use of separators for batteries, but single-layer or multi-layered microporous membranes, woven fabrics, or non-woven fabrics made of polypropylene, polyethylene, or other polyolefins can be used.
[0078] The application of the lithium-ion battery in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the lithium-ion battery of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.
[0079] The preparation of lithium-ion batteries is described below with reference to specific embodiments. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.
[0080] Example
[0081] The following are examples of non-aqueous electrolytes of this application, but this application is not limited to these examples.
[0082] Manufacturing of lithium-ion batteries
[0083] The positive electrode active material (97% by mass) and acetylene black (1.5% by mass) from Table 1-1 were mixed and added to a solution obtained by dissolving 1.5% by mass of polyacrylonitrile in 1-methyl-2-pyrrolidone. This mixture was then used to prepare a positive electrode paste. The paste was coated onto aluminum foil, dried, pressurized, and then cut to the specified size to fabricate the positive electrode. The density of the positive electrode, excluding the current collector, was 4.15 g / cm³. 3 .
[0084] In addition, 96% by mass of the negative electrode active material and 2% by mass of styrene-butadiene rubber from Table 1-1 were mixed and added to a solution obtained by dissolving 2% by mass of lithium carboxymethyl cellulose in deionized water, and then mixed to prepare a negative electrode paste. This negative electrode paste was coated onto copper foil, dried, pressurized, and then cut into specified sizes to fabricate the negative electrode. The density of the negative electrode, excluding the current collector, was 1.6 g / cm³. 3 .
[0085] The positive and negative electrodes prepared as described above were each connected to a wire. The electrodes were then stacked using a 10 μm thick polypropylene porous membrane. Furthermore, LiPF6, serving as the supporting electrolyte, was dissolved in a solution containing (I) lithium difluorophosphate, (II) 1,3,6-trihexamethylenenitrile, (III) 1,2,3-tris(2-cyanoethoxy)propane, (IV) a boron-containing lithium salt additive, and propyl propionate, ethyl propionate, ethylene carbonate, and propylene carbonate (mass ratio 2.3:2:1.2:0.9). Based on 100 parts by mass of the total non-aqueous electrolyte, the contents and composition of (I) to (IV) are shown in Tables 1 and 2, with the LiPF6 content being 14%.
[0086] The laminated body and 3.2g of electrolyte are then housed together in an aluminum laminated casing. The opening of the casing is heat-sealed, and a lithium-ion battery is manufactured through formation, capacity testing, and other steps. This lithium-ion battery is a pouch-shaped structure with a width of 35mm, a height of 48mm, and a thickness of 5mm.
[0087] Table 1
[0088] Table 1 shows the positive and negative electrode materials and electrolyte component codes of the prepared lithium-ion batteries. The detailed composition is shown in Tables 1-1, 1-2, and 1-3, respectively.
[0089] [Revised according to Rule 26, 03.07.2026] Table 1: Positive electrode, negative electrode, and electrolyte composition
[0090] [Corrected according to Rule 26, 03.07.2026] The values in parentheses above are all mass percentages.
[0091] [Revised according to Rule 26, 03.07.2026] Table 1-1 Cathode Component Codes
[0092] [Revised according to Detailed Rule 26, 03.07.2026] Table 1-2 Negative Electrode Component Codes
[0093] [Revised according to Detailed Rules 26, 2003.07.2026] Table 1-3 Electrolyte Component Codes
[0094] Test methods
[0095] Gas generation at the electrode
[0096] The secondary batteries prepared in the examples and comparative examples were left to stand at 25°C for 24 hours. Then, a charge-discharge operation was performed at 25°C, charging to 4.6V at 0.1C and discharging to 3.0V at 0.1C. The battery cells were immersed in flowing paraffin, and the volume X0 of the battery cells was measured. Furthermore, the charge-discharge operation was repeated 1000 times under the same conditions at 60°C. After 1000 cycles, the battery cells were immersed in flowing paraffin, and the volume X1 of the battery cells was measured. The rate of change of battery cell volume ΔX before and after the high-temperature cycling test of 1000 charge-discharge cycles was calculated using ΔX(%) = (X1-X0) / X0×100. The smaller the value of the rate of change of battery cell volume ΔX, the less gas is generated from the electrodes, and the better the electrode's ability to suppress gas generation. The rate of change of battery cell volume ΔX can be divided into the following criteria:
[0097] A: Less than 10%
[0098] B: 10% or more but less than 20%
[0099] C: 20% or more but less than 30%
[0100] D: Over 30%
[0101] IV resistors
[0102] The lithium-ion batteries obtained in the examples and comparative examples were charged at 25°C at 1C [C is a value expressed in rated capacity (mA) / 1h (hour)] to 50% SOC [State of Charge (SOC)]. Then, centered at 50% SOC, the batteries were charged and discharged for 30 seconds at 0.1C, 0.2C, 0.5C, 1C, and 2C, respectively. The battery voltage 10 seconds after discharge was plotted against the current value for each case, and the slope was calculated as the IV resistance (Ω). The obtained IV resistance value (Ω) was evaluated according to the following criteria: a smaller IV resistance value indicates a smaller internal resistance.
[0103] A: IV resistance is less than 80Ω
[0104] B: IV resistance is 80Ω or higher and less than 90Ω
[0105] C: IV resistance is 90Ω or higher and less than 100Ω
[0106] D: IV resistance is 100Ω or higher
[0107] Resistance rise during high-temperature cycling test
[0108] The lithium-ion batteries obtained in the examples and comparative examples were secured with a pressure clamp at a specific pressure of 1 MPa and subjected to a cycle test at 65°C. The cycle test conditions were set as 1C CC+CV charging (4.6V, 1 / 50CCut) and 1C CC discharging (3.0VCut), repeated for 500 charge-discharge cycles. Then, while keeping the pressure clamped, the temperature was lowered to 25°C. The capacity retention rate (%) before and after cycling was calculated (= discharge capacity retention rate after cycle test / discharge capacity retention rate before cycle test × 100) and evaluated according to the following criteria. A higher capacity retention rate before and after cycling indicates a smaller increase in resistance during the cycle test.
[0109] A: Capacity retention rate is above 85%.
[0110] B: Capacity retention rate is above 80% and below 85%.
[0111] C: Capacity retention rate is above 70% and below 80%.
[0112] D: Capacity retention rate less than 70%
[0113] Table 2
[0114] In Table 2, a1 represents the content of (I) lithium difluorophosphate, a2 represents the content of (II) 1,3,6-hexanetricarbonyl nitrile, a3 represents the content of (III) 1,2,3-tris(2-cyanoethoxy)propane, a4 represents the total content of (IV) boron-containing lithium salt additives, b represents the total content of other nitrile compounds, and c represents the total content of other additives.
[0115] [Revised according to Rule 26, 03.07.2026] Table 2: Content of Components Added to Non-Aqueous Electrolytes
[0116] When the non-aqueous electrolyte contains 0.02% to 3% by mass of lithium difluorophosphate, 0.4% to 4% by mass of 1,3,6-hexanetricarbonyl nitrile, 0.4% to 5% by mass of 1,2,3-tris(2-cyanoethoxy)propane, 0.01% to 3% by mass of boron-containing lithium salt additives, a total content of lithium difluorophosphate and 1,2,3-tris(2-cyanoethoxy)propane of 0.96% to 5.56% by mass, and a total content of 1,3,6-hexanetricarbonyl nitrile and boron-containing lithium salt additives of 0.45% to 4.6% by mass, it can not only improve the gas generation of the lithium-ion battery electrode, but also suppress IV resistance and significantly improve the high-temperature cycle performance of the lithium-ion battery.
[0117] In particular, when the non-aqueous electrolyte also contains other nitrile compounds, it can reduce the resistance of the coating formed by the reaction of the aforementioned (I) to (IV) substances with the active part of the positive electrode surface, improve lithium-ion charge transport, suppress the amount of gas generated by the electrode, further suppress IV resistance, and significantly improve the high-temperature cycle performance of lithium-ion batteries.
[0118] In particular, when the non-aqueous electrolyte also contains other additives, the inventors unexpectedly discovered that the other additives can inhibit the decomposition and regeneration of the coating formed by the reaction of the aforementioned (I) to (IV) substances with the active part of the positive electrode surface during the charging and discharging process, suppress the amount of gas generated by the electrode, further suppress IV resistance and improve the high-temperature cycle performance of the lithium-ion battery.
[0119] Throughout this specification, references to "embodiment," "partial embodiment," "one embodiment," "another example," "example," "specific example," or "partial example" mean that at least one embodiment or example in this application includes a specific feature, structure, material, or characteristic described in that embodiment or example. Therefore, descriptions appearing throughout this specification, such as "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a specific example," or "example," do not necessarily refer to the same embodiments or examples in this application. Furthermore, specific features, structures, materials, or characteristics in this application can be combined in any suitable manner in one or more embodiments or examples.
[0120] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.
Claims
1. A non-aqueous electrolyte for lithium-ion batteries, characterized in that, The nonaqueous electrolyte includes a nonaqueous solvent and a lithium salt, and contains (I) lithium difluorophosphate in an amount of 0.02 mass% or more and 3 mass% or less, (II) 1,3,6-hexanetriscarbonitrile in an amount of 0.4 mass% or more and 4 mass% or less, (III) 1,2,3-tris(2-cyanoethoxy)propane in an amount of 0.4 mass% or more and 5 mass% or less, (IV) a lithium salt containing boron in an amount of 0.01 mass% or more and 3 mass% or less; the total amount of the (I) and the (III) is 0.96 mass% or more and 5.56 mass% or less, and the total amount of the (II) and the (IV) is 0.45 mass% or more and 4.6 mass% or less.
2. The nonaqueous electrolyte according to claim 1, characterized by The (IV) includes at least one of lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium tetracyanoborate, lithium tetrakis(trifluoromethyl)borate, lithium (trifluoromethyl)trifluoroborate, lithium bis(trifluoromethyl)difluoroborate, lithium pentafluoroethyltrifluoroborate, lithium dicyano(oxalato)borate, lithium bis(malonato)borate, lithium (2-fluoromalonato)difluoroborate, lithium malonato(oxalato)borate, lithium bis(papaverinato)borate, lithium methoxytricyanoborate, lithium ethoxytricyanoborate, lithium tetramethoxyborate, lithium tetraethoxyborate, lithium tetrakis(trifluoromethoxy)borate, lithium tetrakis(2,2,2-trifluoroethoxy)borate, lithium polytetrakis(papaverinato)borate, lithium bis(trifluoroborate) sulfate, lithium difluoroborate, lithium methanedisulfonato difluoroborate, lithium difluorophosphoryloxytrifluoroborate, lithium bis(difluorophosphoryloxy)difluoroborate, or lithium tetrakis(difluorophosphoryloxy)borate.
3. The nonaqueous electrolyte according to claim 1 or 2, characterized by The amount of the (I) is 0.02 mass% or more and 2.6 mass% or less, or the amount of the (III) is 0.4 mass% or more and 4.8 mass% or less, or the total amount of the (I) and the (III) is 0.96 mass% of more and 5.36 mass% or less, based on the total mass of the nonaqueous electrolyte.
4. The nonaqueous electrolyte according to claim 1 or 2, characterized by The amount of the (I) is 0.02 mass% or more and 0.11 mass% or less, or the amount of the (III) is 0.6 mass% or more and 2.6 mass% or less, or the total amount of the (I) and the (III) 1.16 mass% or more and 3.46 mass% or less, based on the total mass of the nonaqueous electrolyte.
5. The nonaqueous electrolyte according to claim 1 or 2, wherein The total amount of the (I) and the (III) is 2.03 mass% or more and 4.05 mass% or less, based on the total mass of the nonaqueous electrolyte.
6. The nonaqueous electrolyte according to any one of claims 1 to 5, characterized by The content of the (II) is 0.4 mass% or more and 3.4 mass% or less, or the content of the (IV) is 0.03 mass% or more and 2.5 mass% or less, or the total content of the (II) and the (IV) is 1.25 mass% or more and 3.7 mass% or less, based on the total mass of the nonaqueous electrolyte.
7. The nonaqueous electrolyte according to any one of claims 1 to 5, characterized by The content of the (II) is 0.8 mass% or more and 2.6 mass% or less, or the content of the (IV) is 0.05 mass% or more and 1.8 mass% or less, or the total content of the (II) and the (IV) 1.65 mass% or more and 3.85 mass% or less, based on the total mass of the nonaqueous electrolyte.
8. The nonaqueous electrolyte according to any one of claims 1 to 5, characterized by The total content of the (II) and the (IV) is 1.85 mass% or more and 4.5 mass% or less, based on the total mass of the nonaqueous electrolyte.
9. The nonaqueous electrolyte according to any one of claims 1 to 8, characterized by, The nonaqueous electrolyte further includes other nitrile-based compounds, which include at least one of succinonitrile, adiponitrile, ethyleneglycol bis(propionitrile) ether, 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, or 1,2,5-tris(cyanoethoxy)pentane.
10. The nonaqueous electrolyte according to claim 9, wherein The other nitrile-based compounds include succinonitrile and adiponitrile, or the other nitrile-based compounds include succinonitrile and ethyleneglycol bis(propionitrile) ether, or the other nitrile-based compounds include adiponitrile and ethyleneglycol bis(propionitrile) ether.
11. The nonaqueous electrolyte according to claim 9 or 10, characterized by The content of the other nitrile-based compounds is 0.3 mass% or more and 8 mass% or less, based on the total mass of the nonaqueous electrolyte.
12. The nonaqueous electrolyte according to claim 9 or 10, wherein The other nitrile-based compounds include succinonitrile and adiponitrile; or the other nitrile-based compounds include succinonitrile and ethylenegylcol bis(propionitrile) ether; or the other nitrile-based compounds include adiponitrile and ethylenegylcol bis(propionitrile) ether.
13. The nonaqueous electrolyte according to claim 9 or 10, wherein The content of the other nitrile-based compounds 1.4 mass% or more and 6.2 mass% or less, based on the total mass of the nonaqueous electrolyte.
14. The nonaqueous electrolyte according to any one of claims 1 to 13, characterized by The nanaqueous electrolyte further includes other additives, which include at least one of lithium monofluorophosphate, fluoroethylene carbonate, vinylene carbonate, lithium fluorosulfate, 1,3-propane sultone, 1,3-propene sultone, ethylene sulfate, 1,3-propanediol cyclic sulfate, fluorobenzene, cyclohexylbenzene, biphenyl, tris(trimethylsilyl)phosphate, or tris(trimethylsilyl)borate.
15. The nonaqueous electrolyte according to claim 14, wherein The other additive includes vinylsulfate and lithium fluorosulfate; or the other additive includes lithium monofluorophosphate and fluoroethylene carbonate; or the other additive includes lithium monofluorophosphate and 1,3-propane sultone; or the other additive includes lithium fluorosulfate and 1,3-propane sultone; or the other additive includes vinylsulfate and 1,3-propane sultone; or the other additive includes tris(trimethylsilyl)phosphate and vinylsulfate; or the other additive includes tris(trimethylsilyl)borate and vinylsulfate.
16. The nonaqueous electrolyte according to claim 14 or 15, characterized by The content of the other additive is 0.3 mass% or more and 10 mass% or less based on the total mass of the nonaqueous electrolyte solution.
17. The nonaqueous electrolyte according to claim 14 or 15, wherein The content of the other additive is 0.9 mass% or more and 4.6 mass% or less based on the total mass of the nonaqueous electrolyte solution.
18. The nonaqueous electrolyte according to claim 14 or 15, wherein The other additive is present in an amount of 5.3 mass% or more and 8.2 mass% or less based on the total mass of the nonaqueous electrolyte solution.
19. A lithium ion battery which is a lithium ion battery provided with a positive electrode, a negative electrode, and a nonaqueous electrolyte in which an electrolyte salt is dissolved in a nonaqueous solvent, characterized by The nonaqueous electrolyte solution is the nonaqueous electrolyte solution according to any one of claims 1 to 18; the positive electrode contains lithium cobaltate having at least three kinds of elements selected from the group consisting of aluminum, magnesium, titanium, zirconium, lanthanum, iridium, cerium, and tungsten; or the negative electrode contains at least one selected from the group consisting of lithium metal, lithium alloy, carbon material capable of intercalating and deintercalating lithium, elemental tin, tin compound, elemental silicon, silicon oxide compound, silicon carbon compound, and lithium titanate compound as a negative electrode active material.
20. An electronic device, comprising: A lithium ion battery according to claim 18.