Non-aqueous electrolyte and secondary battery

Abstract

In order to overcome the problem that the solid electrolyte interface film formed by unsaturated carbonate has low first coulomb efficiency and poor cycle performance due to insufficient ionic conductivity and large lithium consumption, the application provides a non-aqueous electrolyte and a secondary battery, the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, the additive comprises a first additive, a second additive and a third additive, the first additive comprises a compound shown in structural formula 1, the second additive comprises at least one unsaturated carbonate selected from vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate and 1-methyl-1-vinyl ethylene carbonate, and the third additive comprises one or both of acetone and tert-butyl alcohol; the non-aqueous electrolyte shown in structural formula 1 satisfies the following conditions: 10<=X / Y<=500, 0.1<=Z / X<=30, 10<=X<=1000, 1<=Y<=5 and 10<=Z<=500. The non-aqueous electrolyte provided by the application can control the film forming quality of unsaturated carbonate, and effectively improve the first coulomb efficiency and cycle life of the secondary battery.

Description

Technical Field

[0001] This invention belongs to the field of battery material technology, specifically relating to a non-aqueous electrolyte and a secondary battery. Background Technology

[0002] The increasing global reliance on renewable energy necessitates efficient and reliable energy storage solutions to balance supply and demand. Lithium-ion batteries, due to their high energy conversion efficiency and overall performance, have become the preferred technology for industries such as new energy vehicles, electric light vehicles, power tools, consumer electronics, and new energy storage. Electrolyte, one of the four main materials of lithium-ion batteries, is the carrier for the movement of lithium ions between the positive and negative electrodes. The solvation behavior of the electrolyte has a significant impact on the stability of the solid electrolyte interfacial film.

[0003] In existing research, unsaturated ethylene carbonate containing unsaturated alkenyl groups has been shown to preferentially participate in the formation of a solid electrolyte interfacial film on the negative electrode surface during battery formation, and the formed electrolyte interfacial film has a good effect on inhibiting the decomposition of electrolyte at the negative electrode interface. However, the single unsaturated ethylene carbonate reaction requires a high activation energy, the formed solid electrolyte interfacial film is thick, and a large amount of active lithium is consumed in the process of forming the solid electrolyte interfacial film, resulting in a decrease in battery capacity. Therefore, how to improve the film-forming performance of unsaturated ethylene carbonate is an urgent problem to be solved. Summary of the Invention

[0004] To address the problems of low initial coulombic efficiency and poor cycle performance caused by insufficient ionic conductivity and high lithium consumption in existing solid electrolyte interfacial films formed by unsaturated carbonates, this invention provides a non-aqueous electrolyte and a secondary battery.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] On one hand, the present invention provides a non-aqueous electrolyte comprising a non-aqueous organic solvent, an electrolyte salt, and an additive, wherein the additive comprises a first additive, a second additive, and a third additive, wherein the first additive comprises a compound represented by structural formula 1, the second additive comprises at least one unsaturated carbonate selected from vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, or 1-methyl-1-vinyl ethylene carbonate, and the third additive comprises one or both of acetone or tert-butanol;

[0007]

[0008] Structural Formula 1

[0009] Wherein, n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not... Both are hydrogen, and R1 and R2 can be linked together to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene groups, substituted or unsubstituted C2-C12 alkenyl groups, substituted or unsubstituted C2-C12 alkyne groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 ether groups; when R1, R2, and R3 are substituted, the substituents are alkoxy, hydroxyl, acyl, ester, cyano, or halogen.

[0010] The non-aqueous electrolyte meets the following conditions:

[0011] 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500;

[0012] Where X is the mass content of the first additive in the non-aqueous electrolyte, in ppm;

[0013] Y represents the mass percentage of the second additive in the non-aqueous electrolyte, expressed in % (%).

[0014] Z represents the mass content of the third additive in the non-aqueous electrolyte, expressed in ppm.

[0015] Optionally, the non-aqueous electrolyte meets the following conditions:

[0016] 10≤X / Y≤200, 0.3≤Z / X≤10.

[0017] Optionally, the non-aqueous electrolyte satisfies at least one of the following conditions:

[0018] (1) 20 ≤ X ≤ 500;

[0019] (2) 1.5≤Y≤4;

[0020] (3) 100≤Z≤300.

[0021] Optionally, the compound represented by structural formula 1 satisfies at least one of the following conditions:

[0022] (1) R1 is selected from hydrogen, and R2 is selected from hydrogen. substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl;

[0023] (2) R1 and R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, or substituted or unsubstituted C6-C20 aryl.

[0024] (3) R1 is selected from R2 is selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, or... , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, substituted or unsubstituted C6-C20 aryl, and substituted or unsubstituted C2-C12 ether.

[0025] (4) R1 is selected from , where R 12 R2 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl; R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl or... , where R 13 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, and substituted or unsubstituted C2-C11 alkynyl groups.

[0026] Optionally, the compound represented by structural formula 1 includes one or more of the following compounds:

[0027] .

[0028] Optionally, the additive may also include one or more of cyclic sulfate compounds, sulfonyl lactone compounds, silicon-containing compounds, phosphite compounds, and isocyanate (urea) ester compounds.

[0029] Optionally, the cyclic sulfate compound includes at least one of vinyl sulfate, methyl vinyl sulfate, and 4,4'-divinyl sulfate; and / or

[0030] The sulfonyl lactone compound includes at least one of 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methanedisulfonate; and / or

[0031] The silicon-containing compound includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, hexamethyldisilazane, and heptamethyldisilazane; and / or

[0032] The phosphite compound includes at least one selected from trimethyl phosphite, triethyl phosphite, triphenyl phosphite, and tricresyl phosphite; and / or

[0033] The isocyanate compound includes at least one of trimethyl isocyanurate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene-2,4-diisocyanate, and trimethylsilyl isocyanate.

[0034] Optionally, the non-aqueous electrolyte does not include polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

[0035] In another aspect, the present invention provides a secondary battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0036] Optionally, the positive electrode includes a positive electrode active material, which includes LiFe. 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0037] The non-aqueous electrolyte provided by this invention uses a compound of structural formula 1 as a first additive, an unsaturated carbonate as a second additive, and one or both of acetone or tert-butanol as a third additive. The inventors discovered through research that when the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive satisfy the conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500, the resulting non-aqueous electrolyte, when applied to a secondary battery, can effectively improve the initial coulombic efficiency and cycle life of the secondary battery. This is presumably due to the reduction potential (vs.) of the first additive. The Li / Li+ ratio is lower than that of the second additive, so it preferentially undergoes reduction and decomposition at the negative electrode to form an intermediate product. This intermediate product reduces the activation energy required for the second additive to form a film at the negative electrode. The resulting SEI film is denser and more uniform than that of a secondary battery containing only the second additive, reducing the thickness of the SEI film and thus reducing the consumption of active lithium during the first charge and discharge process, thereby improving the battery's first coulombic efficiency. However, the electrochemical reaction of the first additive leaves behind a small amount of harmful hydroxyl radicals, which consume the effective content of other additives and produce harmful byproducts. The added third additive can react with the free radicals generated by the first additive, thereby neutralizing them and improving the battery's cycle life. Therefore, the first, second, and third additives interact with each other. By adjusting the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive to achieve a synergistic state, it is beneficial to improve the overall performance of the secondary battery. Detailed Implementation

[0038] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] An embodiment of the present invention provides a non-aqueous electrolyte comprising a non-aqueous organic solvent, an electrolyte salt, and an additive. The additive comprises a first additive, a second additive, and a third additive. The first additive comprises a compound represented by structural formula 1. The second additive comprises at least one unsaturated carbonate selected from vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, or 1-methyl-1-vinyl ethylene carbonate. The third additive comprises one or both of acetone and tert-butanol.

[0040]

[0041] Structural Formula 1

[0042] Wherein, n is 0 or 1; R1 and R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1 and R2 are not... Both are hydrogen, and R1 and R2 can be linked together to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene groups, substituted or unsubstituted C2-C12 alkenyl groups, substituted or unsubstituted C2-C12 alkyne groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 ether groups; when R1, R2, and R3 are substituted, the substituents are alkoxy, hydroxyl, acyl, ester, cyano, or halogen.

[0043] The non-aqueous electrolyte meets the following conditions:

[0044] 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500;

[0045] Where X is the mass content of the first additive in the non-aqueous electrolyte, in ppm;

[0046] Y represents the mass percentage of the second additive in the non-aqueous electrolyte, expressed in % (%).

[0047] Z represents the mass content of the third additive in the non-aqueous electrolyte, expressed in ppm.

[0048] The inventors discovered through research that when the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive satisfy the conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500, the resulting non-aqueous electrolyte, when applied to secondary batteries, can effectively improve the initial coulombic efficiency and cycle life of the secondary battery. This is presumably due to the reduction potential (vs.) of the first additive. The Li / Li+ ratio is lower than that of the second additive, so it preferentially undergoes reduction and decomposition at the negative electrode to form an intermediate product. This intermediate product reduces the activation energy required for the second additive to form a film at the negative electrode. The resulting SEI film is denser and more uniform than that of a secondary battery containing only the second additive, reducing the thickness of the SEI film and thus reducing the consumption of active lithium during the first charge and discharge process, thereby improving the battery's first coulombic efficiency. However, the electrochemical reaction of the first additive leaves behind a small amount of harmful hydroxyl radicals, which consume the effective content of other additives and produce harmful byproducts. The added third additive can react with the free radicals generated by the first additive, thereby neutralizing them and improving the battery's cycle life. Therefore, the first, second, and third additives interact with each other. By adjusting the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive to achieve a synergistic state, it is beneficial to improve the overall performance of the secondary battery.

[0049] In a preferred embodiment, the non-aqueous electrolyte satisfies the following conditions:

[0050] 10≤X / Y≤200, 0.3≤Z / X≤10.

[0051] When the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive further meet the above conditions, it is beneficial to further improve the coulombic efficiency and cycle capacity retention of the secondary battery.

[0052] In a specific embodiment, the mass content X of the first additive in the non-aqueous electrolyte can be 10ppm, 30ppm, 50ppm, 80ppm, 100ppm, 150ppm, 200ppm, 250ppm, 300ppm, 350ppm, 400ppm, 450ppm, 500ppm, 550ppm, 600ppm, 650ppm, 700ppm, 750ppm, 800ppm, 850ppm, 900ppm, 950ppm, 1000ppm, or any combination of these values.

[0053] In a preferred embodiment, 20 ≤ X ≤ 500.

[0054] The first additive is used to regulate the film formation quality of the second additive on the negative electrode surface. If the content of the first additive is too small, it is difficult to effectively ensure the density and uniformity of the SEI film on the negative electrode surface, resulting in an excessively thick SEI film and excessive consumption of active lithium. If the content of the first additive is too large, it will promote the generation of too many free radicals in the non-aqueous electrolyte, increase the probability of side reactions with impurities in the non-aqueous electrolyte, and lead to the instability of the properties of the non-aqueous electrolyte itself.

[0055] In a specific embodiment, the mass percentage Y of the second additive in the non-aqueous electrolyte can be 1%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, 2.2%, 2.8%, 3%, 3.2%, 3.8%, 4%, 4.2%, 4.8%, 5%, or any combination of these values.

[0056] In a preferred embodiment, 1.5 ≤ Y ≤ 4.

[0057] The second additive is the main additive component involved in the formation of the negative electrode film. If the content of the second additive is too low, it will be difficult to form a complete SEI film on the surface of the negative electrode, causing the active lithium to be continuously consumed during battery cycling and affecting the battery cycle life. If the content of the second additive is too high, it will easily lead to an excessively thick SEI film, increasing the battery impedance, which is also not conducive to improving the battery cycle performance.

[0058] In a specific embodiment, the mass content Z of the third additive in the non-aqueous electrolyte can be 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 80ppm, 100ppm, 150ppm, 180ppm, 200ppm, 250ppm, 280ppm, 300ppm, 350ppm, 380ppm, 400ppm, 450ppm, 500ppm, or any combination of these values.

[0059] In a preferred embodiment, 100 ≤ Z ≤ 300.

[0060] The third additive is used to eliminate the damage of free radicals generated by the first additive to the non-aqueous electrolyte. Therefore, if the content of the third additive is too small, it is difficult to suppress the deterioration effect of the first additive on the non-aqueous electrolyte, resulting in no significant improvement in battery performance. However, the third additive is also prone to causing side reactions of the non-aqueous electrolyte under high voltage conditions when the content is high. Therefore, the content of the third additive should be based on the content of the first additive.

[0061] In the description of this invention, the term "C1-C12 alkyl" includes straight-chain alkyl, branched alkyl, and cycloalkyl; similarly, the term "C2-C12 alkenyl" includes straight-chain alkenyl, branched alkenyl, and cycloalkenyl; the term "C2-C12 alkynyl" includes straight-chain alkynyl, branched alkynyl, and cycloalkenyl; the term "C1-C12 alkylene" includes straight-chain alkylene, branched alkylene, and cycloalkenyl; the term "C2-C12 alkenyl" includes straight-chain alkenyl, branched alkenyl, and cycloalkenyl; and the term "C2-C12 alynyl" includes straight-chain alynyl, branched alynyl, and cycloalynyl.

[0062] In the description of this invention, the term "C1-C12 acyl" should be interpreted broadly. Specifically, it can be understood as one or more carbon atoms in a C1-C12 alkyl group being surrounded by a carbonyl group. The substitution group is obtained, and the position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the acyl group of C1-C12 is selected from... , where R 14 Selected from single-bonded or C1-C11 alkyl groups, R 15 Alkyl groups selected from C1-C11.

[0063] In the description of this invention, the term "C2-C12 alkoxyacyl" should be interpreted broadly. Specifically, it can be understood as a C2-C12 alkyl group in which one or more carbon atoms are... The substituted group is obtained, and the position of the substituted carbon atom is not particularly limited. In a preferred embodiment, the C2-C12 alkoxyacyl group is selected from... , where R 16 Selected from single-bonded or C1-C11 alkyl groups, R 17 Alkyl groups selected from C1-C11.

[0064] In the description of this invention, the term "C2-C12 ether group" should be interpreted broadly. Specifically, it can be understood as a connection between two adjacent carbon atoms in a C2-C12 alkyl group. The resulting groups can have one or more oxygen atoms.

[0065] In some embodiments, in the compound represented by structural formula 1, R1 is selected from hydrogen, and R2 is selected from… substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, wherein R 10 Selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, substituted or unsubstituted C2-C11 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0066] At this point, the compound represented by structural formula 1 is a hydroperoxide or an organic peroxy acid. When the compound represented by structural formula 1 is a hydroperoxide or an organic peroxy acid, its high oxygen content can remove reducing impurities in the electrolyte in advance, reduce the amount of gas generated during formation, improve the initial coulombic efficiency, and increase the initial discharge capacity of the secondary battery.

[0067] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0068] .

[0069] In some embodiments, in the compound represented by structural formula 1, R1 and R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl.

[0070] At this point, the compound represented by structural formula 1 is a dihydrocarbon peroxide. When the compound represented by structural formula 1 is a dihydrocarbon peroxide, it inhibits solvent molecule co-intercalation and improves the interfacial compatibility between the electrolyte and the negative electrode.

[0071] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0072] .

[0073] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, or... , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, substituted or unsubstituted C2-C11 alkynyl groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 etheryl groups.

[0074] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... R2 is selected from , where R 11 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, substituted or unsubstituted C2-C11 alkynyl groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 etheryl groups.

[0075] At this point, the compound represented by structural formula 1 is a diacyl peroxide. When the compound represented by structural formula 1 is a diacyl peroxide, in addition to improving battery cycle life, it can also decompose to form inert carbon dioxide during battery thermal runaway to dilute the explosion limits of flammable gases, which is beneficial to improving battery safety performance.

[0076] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0077] .

[0078] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl, wherein R 11 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, substituted or unsubstituted C2-C11 alkynyl groups, substituted or unsubstituted C6-C20 aryl groups, and substituted or unsubstituted C2-C12 etheryl groups.

[0079] At this point, the compound represented by structural formula 1 is a peroxy ester. When the compound represented by structural formula 1 is a peroxy ester, it can improve the wettability of the electrolyte to the electrode, reduce the ohmic internal resistance of the battery, and improve the discharge performance of the battery.

[0080] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0081] .

[0082] In some embodiments, in the compound represented by structural formula 1, R1 is selected from... , where R 12 R2 is selected from substituted or unsubstituted C1-C11 alkyl, substituted or unsubstituted C2-C11 alkenyl, and substituted or unsubstituted C2-C11 alkynyl; R2 is selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl or... , where R 13 Selected from substituted or unsubstituted C1-C11 alkyl groups, substituted or unsubstituted C2-C11 alkenyl groups, and substituted or unsubstituted C2-C11 alkynyl groups.

[0083] At this point, the compound represented by structural formula 1 is a peroxycarbonate or a peroxydicarbonate. When the compound represented by structural formula 1 is a peroxycarbonate or a peroxydicarbonate, it promotes lithium-ion solvation and improves lithium diffusion performance inside the battery.

[0084] As an example, the compound represented by structural formula 1 may be selected from the following compounds:

[0085] .

[0086] In some embodiments, the compound represented by structural formula 1 includes one or more of the following compounds:

[0087] .

[0088] In the description of this invention, the term "unsaturated carbonate" refers to a carbonate structure containing an unsaturated hydrocarbon group.

[0089] In some embodiments, the additive further includes one or more of cyclic sulfate compounds, sulfonyl lactone compounds, silicon-containing compounds, phosphite compounds, and isocyanate (urea) ester compounds.

[0090] In some embodiments, the cyclic sulfate compound includes at least one of vinyl sulfate, methyl vinyl sulfate, and 4,4'-divinyl sulfate.

[0091] In some embodiments, the sulfonyl lactone compound includes at least one of 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

[0092] In some embodiments, the silicon-containing compound includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and hexamethyldisilazane.

[0093] In some embodiments, the phosphite compound includes at least one of trimethyl phosphite, triethyl phosphite, triphenyl phosphite, and tricresyl phosphite.

[0094] In some embodiments, the isocyanate compound includes at least one of trimethyl isocyanurate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene-2,4-diisocyanate, and trimethylsilyl isocyanate.

[0095] It should be noted that, unless otherwise specified, the content of any optional substance in the additive in the non-aqueous electrolyte is generally less than 10%, preferably 0.01-5%, and more preferably 0.1% to 2%. Specifically, the content of any optional substance in the additive can be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of these values.

[0096] In some embodiments, the mass content of the non-aqueous organic solvent is 65% to 90% based on the total mass of the non-aqueous electrolyte being 100%.

[0097] Specifically, based on the total mass of the non-aqueous electrolyte as 100%, the mass content of the non-aqueous organic solvent can be 65%, 68%, 71%, 74%, 76%, 78%, 79%, 80%, 81.5%, 82%, 84%, 85%, 86%, 87%, 89%, 90%, or any combination of these values.

[0098] In some embodiments, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0099] In some embodiments, the ether solvent includes cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. The cyclic ethers may specifically include, but are not limited to, at least one of 1,3-dioxolane, 1,4-dioxolane, crown ethers, tetrahydrofuran, 2-methyltetrahydrofuran, and 2-trifluoromethyltetrahydrofuran. The chain ethers may specifically include, but are not limited to, dimethoxymethane, diethoxymethane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. Ether compounds can be used alone or in any combination and ratio of two or more. There are no special restrictions on the content of ether compounds. It can be arbitrary within the range that does not significantly impair the effect of the high-pressure lithium-ion battery of the present invention. When the volume ratio of non-aqueous solvent is 100%, the volume ratio is usually 1% or more, preferably 2% or more, and more preferably 3% or more. In addition, the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less.

[0100] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0101] In some embodiments, the carbonate solvent includes cyclic carbonates or chain carbonates. Cyclic carbonates may specifically include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC); chain carbonates may specifically include, but are not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of cyclic carbonates is not particularly limited and is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of this invention. However, when using only one type, its content is typically 3% or more, preferably 5% or more, by volume relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less by volume. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby contributing to enhanced stability during high-temperature storage. The content of the chain carbonate is not particularly limited, but relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 15% or more by volume, preferably 20% or more, and more preferably 25% or more. Furthermore, it is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By keeping the chain carbonate content within the above range, it is easier to achieve an appropriate viscosity for the non-aqueous electrolyte, suppressing the decrease in ionic conductivity, and thus contributing to achieving a good range of output characteristics for the non-aqueous electrolyte battery. When using two or more chain carbonates in combination, it is sufficient to ensure that the total amount of chain carbonate meets the above range.

[0102] In some embodiments, fluorine-containing chain carbonates (hereinafter referred to as "fluorinated chain carbonates") are also preferably used. There is no particular limitation on the number of fluorine atoms in a fluorinated chain carbonate as long as it is 1 or more, but it is generally 6 or less, preferably 4 or less. When a fluorinated chain carbonate has multiple fluorine atoms, these fluorine atoms can be bonded to the same carbon atom or to different carbon atoms. Examples of fluorinated chain carbonates include dimethyl fluorinated carbonate derivatives, methyl ethyl fluorinated carbonate derivatives, and diethyl fluorinated carbonate derivatives.

[0103] Carboxylic acid ester solvents include cyclic carboxylic acid esters and / or chain carbonates. Examples of cyclic carboxylic acid esters include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, propyl propionate, and butyl propionate.

[0104] In some embodiments, the sulfone solvent includes cyclic sulfones and chain sulfones. Preferably, in the case of cyclic sulfones, it is typically a compound with 3 to 6 carbon atoms, more preferably 3 to 5 carbon atoms; in the case of chain sulfones, it is typically a compound with 2 to 6 carbon atoms, more preferably 2 to 5 carbon atoms. The content of the sulfone solvent is not particularly limited and is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of the present invention. Relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume. Furthermore, it is typically 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume. When using two or more sulfone solvents in combination, the total amount of sulfone solvent should satisfy the above range. When the content of the sulfone solvent is within the above range, a non-aqueous electrolyte with excellent high-temperature storage stability is preferred.

[0105] In some embodiments, the electrolyte salt is selected from lithium salts, including LiPF6, LiODFP, LiODFB, LiBOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, and Li2B. 10 Cl 10 At least one of lithium chloroborane, lithium trioxazophosphate, lithium lower aliphatic carboxylic acid having four or fewer carbon atoms, or lithium tetraphenylborate.

[0106] In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol / L to 4 mol / L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2.5 mol / L. Specifically, in the non-aqueous electrolyte, the concentration of the lithium salt can be 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1.0 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.45 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L, or any combination of these values.

[0107] It should be emphasized that the non-aqueous electrolyte provided in this application is not a precursor to a gel electrolyte or solid electrolyte, nor is it suitable as a precursor to a gel electrolyte or solid electrolyte. The reason is that the improvement of the electrochemical performance of the secondary battery in this application relies on the compound shown in Formula 1 participating in the formation of the solid electrolyte interphase (SEI) film on the negative electrode surface during the battery charge-discharge formation stage, and the compound shown in Formula 1 remaining in the electrolyte continuously repairing the damaged solid electrolyte interphase (SEI) film during long-term battery cycling. However, as a precursor to a gel electrolyte or solid electrolyte, there is a polymerization operation to form a gel electrolyte before the battery charge-discharge formation. In this polymerization operation, the organic peroxide shown in Formula 1 acts as an initiator and reacts with the polymerizable monomer, resulting in the consumption of the compound shown in Formula 1, thus preventing it from playing a corresponding role in the charge-discharge formation and battery charge-discharge cycling process.

[0108] In some embodiments, the non-aqueous electrolyte does not include polymerizable monomers and / or prepolymers obtained by polymerizing polymerizable monomers.

[0109] In some embodiments, the polymerizable monomers include one or more of the following: acrylate monomers (such as methyl acrylate, ethyl acrylate, butyl acrylate), acrylamide monomers (such as acrylamide, N,N'-methylenebisacrylamide), vinyl compound monomers (such as polyvinyl alcohol, vinylpyrrolidone, vinylimidazole), epoxy resin monomers (such as bisphenol A epoxy resin), polyethylene oxide monomers, polyacrylonitrile monomers, and siloxane monomers.

[0110] In some embodiments, the non-aqueous electrolyte does not undergo polymerization under light or heating conditions.

[0111] In some embodiments, the non-aqueous electrolyte is in a liquid state after formation.

[0112] Another embodiment of the present invention provides a secondary battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte as described above.

[0113] In some embodiments, the secondary battery is a lithium-ion battery.

[0114] In some embodiments, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes one or more of the following: lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel oxide (e.g., lithium nickel oxide), lithium manganese oxide (e.g., spinel-type lithium manganese oxide, layered lithium manganese oxide, etc.), lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, and doped / coated modified compounds thereof. Preferably, the positive electrode active material includes LiFe... 1-x’ M' x’ PO4, LiMn2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0115] In a preferred embodiment, the positive electrode active material is selected from LiFe. 1-x’ M' x’ PO4, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V, or Ti, and 0 ≤ x' < 1. The lithium-ion battery described has a high specific capacity, thereby effectively improving the battery's energy density. Furthermore, the battery's charging cut-off voltage can reach 3.8V, exhibiting a high discharge plateau and good cycle stability within a conventional voltage window. Moreover, since iron is relatively abundant and inexpensive globally, compared to rare and expensive metals such as cobalt, nickel, and manganese, using the aforementioned positive electrode active material helps reduce costs and alleviate dependence on limited resources.

[0116] In a more preferred embodiment, the positive electrode active material is selected from LiFe. 1-x’ Mn x’ PO4, where 0 ≤ x' ≤ 0.5.

[0117] In some specific embodiments, the positive electrode active material may include LiCoO2, LiFePO4, LiFe 0.4 Mn 0.6 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.8 Co 0.15 Al 0.05O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al 0.3 One or more of O2.

[0118] In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode material layer.

[0119] The positive electrode binder includes at least one of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylidene, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0120] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0121] In some embodiments, the positive current collector comprises a metallic material capable of conducting electrons. Preferably, the positive current collector comprises at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive current collector is selected from aluminum foil.

[0122] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes at least one of carbon-based negative electrode, silicon-based negative electrode, tin-based negative electrode, and lithium negative electrode. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.; the tin-based negative electrode may include tin, tin-carbon, tin oxide, and tin metal compounds; the lithium negative electrode may include metallic lithium or lithium alloys. Specifically, the lithium alloy may be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy.

[0123] In a more preferred embodiment, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, graphene, and silicon-carbon composite materials.

[0124] In some embodiments, the silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon thin films, 3D porous silicon, and hollow porous silicon.

[0125] In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector. The negative electrode current collector includes a metallic material capable of conducting electrons. Preferably, the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0126] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.

[0127] The negative electrode binder includes at least one of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylidene, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0128] The negative electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0129] In some embodiments, the secondary battery further includes a separator located between the positive electrode and the negative electrode.

[0130] The diaphragm can be a conventional diaphragm, such as a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, or an inorganic-organic composite diaphragm, including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and triple-layer PP / PE / PP diaphragms.

[0131] The present invention will be further illustrated by the following examples.

[0132] Table 1

[0133]

[0134]

[0135] Example 1

[0136] This embodiment illustrates the lithium-ion battery and its preparation method disclosed in this invention, and includes the following steps:

[0137] (1) Preparation of non-aqueous electrolyte:

[0138] The solvents ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 5:2:5:8. Then, 1 mol / L lithium hexafluorophosphate (LiPF6) was added as the electrolyte salt. Based on the total weight of the non-aqueous electrolyte as 100%, the first, second, and third additives were added in the weight percentages shown in Table 1. After homogenization by shaking, the mixture was filtered and allowed to stand for later use.

[0139] (2) Electrolyte injection and formation of the battery cell:

[0140] In a glove box with a water content <10ppm and an oxygen content <50ppm, the non-aqueous electrolyte prepared above was injected into a dry cell with lithium iron phosphate as the positive electrode and artificial graphite as the negative electrode. The cell was held under a vacuum of 20 kPa for 10 minutes, and the encapsulated battery was aged at 45°C for 48 hours. Then, the first charge was performed using the following conventional formation process: 0.05C constant current charging for 2 hours, 0.1C constant current charging for 1 hour, 0.2C constant current charging for 1 hour, and resting for 24 hours. After formation, the cells were vacuumed, vented, and sealed. Subsequently, the cells were further charged at 0.2C constant current to 100% SOC, then charged at a constant voltage to 0.03C (cutoff), and finally discharged at 0.2C constant current to 0% SOC to obtain a secondary battery.

[0141] Examples 2-23

[0142] Examples 2-23 illustrate the lithium-ion battery and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences:

[0143] It is composed of the first additive, the second additive and the third additive shown in Table 1.

[0144] Comparative Examples 1-14

[0145] Comparative Examples 1-14 are used to illustrate the lithium-ion battery and its preparation method disclosed in this invention, including most of the operation steps in Example 1, the difference being:

[0146] It is composed of the first additive, the second additive and the third additive shown in Table 1.

[0147] Performance testing

[0148] The lithium-ion batteries prepared above were subjected to the following performance tests:

[0149] 1. During the battery formation process, record the first discharge capacity and the first charge capacity, and calculate the first coulombic efficiency; the first coulombic efficiency (%) = first discharge capacity / first charge capacity * 100%, and calculate the median of the parallel samples.

[0150] 2. DC Internal Resistance Test During Charging: 1) Charge to 100% SOC (cutoff current 0.05 C) using a 0.5C constant current and constant voltage method, discharge to 50% SOC using a 0.5C constant current method, and let stand for 30 min. 2) Charge to 10s using a 0.1C constant current method, let stand for 40s, discharge to 10s using a 0.1C constant current method, let stand for 40s; charge to 10s using a 0.5C constant current method, let stand for 40s, discharge to 10s using a 0.5C constant current method, let stand for 40s; charge to 10s using a 1C constant current method, let stand for 40s, discharge to 10s using a 1C constant current method, and let stand for 40s. Based on Ohm's law, the DCIR during battery discharge is calculated using the three-point method, thus obtaining the battery impedance.

[0151] 3. Battery room temperature cycle test: After capacity grading, the battery is placed in a constant temperature environment of 25℃, briefly rested, and then charged at 1C constant current and constant voltage to 100% SOC, with a cutoff current of 0.05C. After a brief rest, it is discharged at 1.5C constant current to 0% SOC. This charge-discharge cycle is repeated 2000 times. The discharge capacity of each cycle is recorded, and the capacity retention rate (%) is calculated as: discharge capacity of the 2000th cycle / discharge capacity of the first cycle * 100%. The average value between parallel samples is also calculated.

[0152] (1) The test results obtained from Examples 1-17 and Comparative Examples 1-14 are filled in Table 2.

[0153] Table 2

[0154]

[0155] The test results from Examples 1-17 and Comparative Examples 1-14 show that in a non-aqueous electrolyte system using the compound shown in structural formula 1 as the first additive, unsaturated carbonate as the second additive, and one or both of acetone or tert-butanol as the third additive, when the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive are controlled to satisfy the conditions 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500, the resulting lithium-ion battery exhibits higher initial coulombic efficiency, lower impedance, and higher cycle capacity retention. This is presumably due to the reduction potential (vs) of the first additive. The Li / Li+ ratio is lower than that of the second additive, so it preferentially undergoes reduction and decomposition at the negative electrode to form an intermediate product. This intermediate product reduces the activation energy required for the second additive to form a film at the negative electrode. The resulting SEI film is denser and more uniform than that of a secondary battery containing only the second additive, reducing the thickness of the SEI film and thus reducing the consumption of active lithium during the first charge and discharge process, thereby improving the battery's first coulombic efficiency. However, the electrochemical reaction of the first additive leaves behind a small amount of harmful hydroxyl radicals, which consume the effective content of other additives and produce harmful byproducts. The added third additive can react with the free radicals generated by the first additive, thereby neutralizing them and improving the battery's cycle life. Therefore, the first, second, and third additives interact with each other. By adjusting the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive to achieve a synergistic state, it is beneficial to improve the overall performance of the secondary battery.

[0156] As can be seen from the test results of Examples 1 to 17, when the mass content X of the first additive, the mass percentage content Y of the second additive, and the mass content Z of the third additive further satisfy the conditions 10≤X / Y≤200, 0.3≤Z / X≤10, and 20≤X≤500, 1.5≤Y≤4, and 100≤Z≤300, the resulting lithium-ion battery has higher coulombic efficiency and cycle capacity retention.

[0157] The test results from Comparative Examples 1 to 14 show that when the X, Y, and Z values ​​do not meet the limits of 10≤X / Y≤500 and 0.1≤Z / X≤30, or when the X, Y, and Z values ​​are too high or too low, the cycle performance of the lithium-ion battery will deteriorate. This indicates that there is an interaction between the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive. Only when the three reach a good balance can they significantly improve the ionic conductivity and cycle stability of the negative electrode solid electrolyte interface film.

[0158] (2) The test results obtained in Examples 1-6 and 18-23 are filled in Table 3.

[0159] Table 3

[0160]

[0161] As can be seen from the test results of Examples 1-6 and 18-23, in the electrolyte system provided by the present invention, when different first additives, different second additives, or different third additives are used, and when the mass content X of the first additive, the mass percentage Y of the second additive, and the mass content Z of the third additive satisfy the conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, and 10≤Z≤500, it also plays a positive role in improving the coulombic efficiency and cycle performance of lithium-ion batteries. This indicates that the battery system provided by the present invention is applicable to different first additives, second additives, and third additives.

[0162] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nonaqueous electrolyte, characterized by comprising: The non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt, and additives including a first additive, a second additive, and a third additive, the first additive includes a compound shown in structural formula 1, the second additive includes at least one unsaturated carbonate of vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, or 1-methyl-1-vinyl ethylene carbonate, and the third additive includes one or both of acetone or t-butanol; Structural formula 1 wherein n is 0 or 1; R1, R2 are each independently selected from hydrogen, substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, substituted or unsubstituted C6-C20 aryl, substituted or unsubstituted C1-C12 acyl, substituted or unsubstituted C2-C12 alkoxyacyl, substituted or unsubstituted C2-C12 ether, and R1, R2 are not hydrogen at the same time, and R1, R2 can be connected to each other to form a ring or not; R3 is selected from substituted or unsubstituted C1-C12 alkylene, substituted or unsubstituted C2-C12 alkenylene, substituted or unsubstituted C2-C12 alkynylene, substituted or unsubstituted C6-C20 aryl, and substituted or unsubstituted C2-C12 ether; when R1, R2, R3 are substituted, the substituent is alkoxy, hydroxyl, acyl, ester, cyano, or halogen; The non-aqueous electrolyte satisfies the following conditions: 10≤X / Y≤500, 0.1≤Z / X≤30, and 10≤X≤1000, 1≤Y≤5, 10≤Z≤500; wherein X is the mass content of the first additive in the non-aqueous electrolyte, in ppm; Y is the mass percentage content of the second additive in the non-aqueous electrolyte, in %; Z is the mass content of the third additive in the non-aqueous electrolyte, in ppm.

2. The nonaqueous electrolyte according to claim 1, characterized by The non-aqueous electrolyte satisfies the following conditions: 10≤X / Y≤200, 0.3≤Z / X≤10.

3. The nonaqueous electrolyte according to claim 1, characterized by The non-aqueous electrolyte satisfies at least one of the following conditions: （1）20≤X≤500； （2）1.5≤Y≤4； （3）100≤Z≤300。 4. The nonaqueous electrolyte according to claim 1, characterized by The compound shown in structural formula 1 satisfies at least one of the following conditions: (1) R1is selected from hydrogen, R2is selected from , substituted or unsubstituted C1-C12alkyl, substituted or unsubstituted C2-C12alkenyl, substituted or unsubstituted C2-C12alkynyl, substituted or unsubstituted C6-C20aryl, wherein R 10 is selected from substituted or unsubstituted C1-C11alkyl, substituted or unsubstituted C2-C11alkenyl, substituted or unsubstituted C2-C11alkynyl, substituted or unsubstituted C6-C20aryl; (2) R1, R2 are each independently selected from substituted or unsubstituted C1-C12 alkyl, substituted or unsubstituted C2-C12 alkenyl, substituted or unsubstituted C2-C12 alkynyl, and substituted or unsubstituted C6-C20 aryl; (3) R1is selected from ; R2is selected from substituted or unsubstituted C1-C12alkyl, substituted or unsubstituted C2-C12alkenyl, substituted or unsubstituted C2-C12alkynyl, substituted or unsubstituted C6-C20aryl, or wherein R 11 is selected from substituted or unsubstituted C1-C11alkyl, substituted or unsubstituted C2-C11alkenyl, substituted or unsubstituted C2-C11alkynyl, substituted or unsubstituted C6-C20aryl, substituted or unsubstituted C2-C12ether; (4) R1is selected from wherein R 12 is selected from substituted or unsubstituted C1-C11alkyl, substituted or unsubstituted C2-C11alkenyl, substituted or unsubstituted C2-C11alkynyl; R2is selected from hydrogen, substituted or unsubstituted C1-C12alkyl, substituted or unsubstituted C2-C12alkenyl, substituted or unsubstituted C2-C12alkynyl, substituted or unsubstituted C6-C20aryl, or wherein R 13 is selected from substituted or unsubstituted C1-C11alkyl, substituted or unsubstituted C2-C11alkenyl, substituted or unsubstituted C2-C11alkynyl.

5. The nonaqueous electrolyte according to claim 1, wherein The compound shown in structural formula 1 includes one or more of the following compounds: 。 6. The nonaqueous electrolyte according to claim 1, wherein The additives further include one or more of a cyclic sulfate compound, a sulfonic acid lactone compound, a silicon-containing compound, a phosphite compound, and an isocyanate compound.

7. The nonaqueous electrolyte according to claim 6, wherein The cyclic sulfate compound includes at least one of vinyl sulfate, vinyl methyl sulfate, and 4,4'-vinylene disulfate; and / or The sulfonic acid lactone compound includes at least one of 1,3-propane sulfonic acid lactone, 1,3-propylene sulfonic acid lactone, and methane disulfonate methylene; and / or The sulfonic acid lactone compound includes at least one of 1,3-propane sulfonic acid lactone, 1,3-propylene sulfonic acid lactone, and methane disulfonate methylene; and / or The silicon-containing compound includes at least one of tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, hexamethyldisilazane, heptamethyldisilazane; and / or The phosphite compound includes at least one of trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tricresyl phosphite; and / or The isocyanurate compound includes at least one of trimethyl isocyanurate, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, toluene-2,4-diisocyanate, trimethylsilyl isocyanate.

8. The nonaqueous electrolyte according to claim 1, wherein The non-aqueous electrolyte does not include a polymerizable monomer and / or a prepolymer obtained by polymerization of a polymerizable monomer.

9. A secondary battery characterized by comprising: The non-aqueous electrolyte includes a positive electrode, a negative electrode, and the non-aqueous electrolyte according to any one of claims 1 to 8.

10. The secondary battery according to claim 9, characterized by The positive electrode includes a positive electrode active material including LiFe 1-x’ M’ x’ PO4, LiMn 2-y’ M y’ O4, and LiNi x Co y Mn z M 1-x-y-z O2, wherein M’ is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V, or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V, or Ti, and 0≤x’<1, 0≤y’≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

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