Secondary battery and electronic device

Abstract

The invention provides a secondary battery, the secondary battery comprises a negative electrode plate, an electrolyte and a positive electrode plate, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer, the negative electrode material layer comprises a negative electrode active material, and the negative electrode active material comprises a graphite material matrix and amorphous carbon arranged on at least part of the surface of the graphite material matrix. In a Raman spectrogram of the negative electrode active material, ID / IG is greater than or equal to 0.2 and less than or equal to 0.8. The electrolyte comprises at least one of a compound shown in a formula I and a compound shown in a formula II and vinylene carbonate, based on the mass of the electrolyte, the total mass content of the compound shown in the formula I and the compound shown in the formula II is y%, y is larger than or equal to 0.001 and smaller than or equal to 3, the mass content of vinylene carbonate is z%, and (ID / IG) / (y + z) is larger than or equal to 0.015 and smaller than or equal to 72.73. The secondary battery meeting the characteristics has relatively good rapid charging performance and rate capability, and also has relatively good high-temperature storage performance and cycle performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] Lithium-ion batteries have significant advantages such as high energy density, miniaturization and light weight, and are widely used in mobile phones, laptops, tablets, drones, electric vehicles, power tools, power storage systems, etc. As the application of lithium-ion batteries becomes more and more extensive, the requirements for the fast charging performance and rate performance of lithium-ion batteries are also getting higher and higher.

[0003] Carbon coating of graphite materials, the negative electrode active materials, can improve the fast charging performance and rate performance of lithium-ion batteries. However, carbon coating will increase the defectivity of the negative electrode active materials, increase the active reaction area of ​​the negative electrode active materials and the electrolyte, increase the side reactions, and further lead to a large impedance growth rate during the high-temperature storage and gas production and cycle of lithium-ion batteries. Therefore, it is necessary to provide a lithium-ion battery that has good fast charging performance and rate performance, as well as good high-temperature storage performance and cycle performance. Summary of the invention

[0004] The purpose of this application is to provide a secondary battery and an electronic device, so that the secondary battery has good fast charging performance and rate performance, as well as good high temperature storage performance and cycle performance. The specific technical solution is as follows:

[0005] The first aspect of the present application provides a secondary battery, which includes a negative electrode plate, an electrolyte and a positive electrode plate, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer includes a negative electrode active material, wherein the negative electrode active material includes a graphite material matrix and amorphous carbon disposed on at least a portion of the surface of the graphite material matrix. In the Raman spectrum of the negative electrode active material, at 1300 cm -1 Up to 1400cm -1 There is a peak intensity of I in the range D The first characteristic peak at 1550cm -1 Up to 1650cm -1 There is a peak intensity of I in the range G The second characteristic peak, 0.2≤I D / I G ≤0.8. The electrolyte comprises at least one of the compound of formula I and the compound of formula II and vinylene carbonate:

[0006]

[0007] Among them, R 11 , R 12 , R13 and R 14 are each independently selected from a hydrogen atom, a halogen atom, a cyano group, an acetyl group, a substituted or unsubstituted C 1 To C 10 Alkyl, substituted or unsubstituted C 2 To C 10 Alkenyl, substituted or unsubstituted C 2 To C 10 Alkynyl, substituted or unsubstituted C 1 To C 10 Heteroatom-containing alkyl, substituted or unsubstituted C 2 To C 10 heteroatom-containing alkenyl, substituted or unsubstituted C 2 To C 10 Ester group, substituted or unsubstituted C 2 To C 10 An ester group containing a heteroatom; R 11 , R 12 , R 13 and R 14 Two adjacent groups in can be connected to form a ring;

[0008] R 21 is selected from substituted or unsubstituted C 1 To C 10 The alkyl group, R 22 is selected from substituted or unsubstituted C 2 To C 10 alkenyl, n=1, 2 or 3;

[0009] When each group is substituted, the substituent is a halogen atom or a carbonyl group; the heteroatom is selected from Si, O or N. Based on the mass of the electrolyte, the total mass content of the compound of formula I and the compound of formula II is y%, 0.001≤y≤3, and the mass content of vinylene carbonate is z%, 0.015≤(I D / I G ) / (y+z)≤72.73, preferably, 0.033≤(I D / I G ) / (y+z)≤54.55, more preferably, 0.057≤(I D / I G ) / (y+z)≤45.45. By regulating the Raman spectrum of the negative electrode active material I D / I G The value of, the type and mass content of the compound of formula I and the compound of formula II in the electrolyte, the sum of the mass content of the compound of formula I and the compound of formula II and vinylene carbonate and I D / I GThe relationship between the values ​​of and is within the scope of the present application, which can enable the secondary battery to have good fast charging performance and rate performance as well as good high temperature storage performance and cycle performance.

[0010] In one embodiment of the present application, 0.01≤z≤3. By regulating the value of z within the scope of the present application, vinylene carbonate has a suitable mass content, and vinylene carbonate and at least one of the compounds of formula I and formula II can play a synergistic role with each other, effectively improving the problems of increased gas production during high-temperature storage and impedance growth during the cycle of the coated graphite system, and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0011] In one embodiment of the present application, the compound of formula I includes at least one of the following compounds:

[0012]

[0013]

[0014] The compound of formula I is selected. The compound of formula I can play a synergistic role with the vinylene carbonate in the electrolyte, effectively improving the problems of increased gas production during high-temperature storage and impedance growth during the cycle of the coated graphite system, and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0015] In one embodiment of the present application, the compound of formula II includes at least one of the following compounds:

[0016]

[0017] The compound of formula II is selected. The compound of formula II can play a synergistic role with the vinylene carbonate in the electrolyte, effectively improving the problems of increased gas production during high-temperature storage and impedance growth during the cycle of the coated graphite system, and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0018] In one embodiment of the present application, the mass ratio of the graphite material matrix to the amorphous carbon is 100:(0.1 to 5). By regulating the mass ratio of the graphite material matrix to the amorphous carbon within the scope of the present application, the graphite material matrix and the amorphous carbon have a suitable mass content, which can further improve the fast charging performance and rate performance of the secondary battery.

[0019] In one embodiment of the present application, the secondary battery satisfies at least one of the following characteristics: (1) the compaction density of the negative electrode material layer is fg / cm 3 , 1.5≤f≤1.8; (2) the graphite material matrix includes at least one of natural graphite or artificial graphite.

[0020] In one embodiment of the present application, the electrolyte further includes a sulfur-oxygen double bond compound; the sulfur-oxygen double bond compound includes at least one of methane disulfonic acid methylene ester, 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, vinyl sulfate, 1,3-propane disulfonic anhydride, 2-methylbutane sultone or 1,3-propylene glycol cyclic sulfate. Since the above-mentioned sulfur-oxygen double bond compounds have strong antioxidant capacity, the stability of the positive electrode interface can be effectively improved; on the other hand, the sulfur-oxygen double bond compounds have poor anti-reduction ability, and preferentially form a solid electrolyte interface (SEI) film on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte at the negative electrode interface. Therefore, the use of sulfur-oxygen double bond compounds can further improve the cycle performance of secondary batteries.

[0021] Based on the mass of the electrolyte, the mass content of the sulfur-oxygen double bond compound is g%, 0.005≤g≤5. By regulating the mass content of the sulfur-oxygen double bond compound within the scope of this application, the sulfur-oxygen double bond compound has a suitable mass content, and the sulfur-oxygen double bond compound can effectively reduce the reaction of the electrolyte at the positive electrode and the negative electrode; it can also better improve the stability of the positive electrode interface and the negative electrode interface, and at the same time, it can make the electrolyte have a suitable viscosity, so that the secondary battery has good cycle performance and high temperature storage performance.

[0022] In one embodiment of the present application, the electrolyte further includes a lithium-containing additive, and the lithium-containing additive includes at least one of lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium dioxalate borate, lithium tetrafluoroborate or lithium difluorooxalate borate. The electrolyte further includes a lithium-containing additive, and the above-mentioned lithium-containing additive is selected. The above-mentioned lithium-containing additive can form a film at the interface of the positive electrode and the negative electrode, effectively protecting the positive electrode interface and the negative electrode interface. The lithium-containing additive and the compound of formula I or the compound of formula II produce a synergistic effect, which can further improve the cycle performance of the secondary battery.

[0023] Based on the mass of the electrolyte, the mass content of the lithium-containing additive is h%, 0.005≤h≤2. By regulating the mass content of the lithium-containing additive within the scope of this application, the lithium-containing additive can effectively protect the electrode interface and effectively improve the cycle performance of the secondary battery.

[0024] In one embodiment of the present application, the electrolyte further comprises at least one of the compounds of formula III:

[0025]

[0026] Among them, R 31 , R 33 Each independently selected from C 1 To C 4 The alkyl group, R 32 Selected from C 1 To C4 of alkylene.

[0027] Based on the mass of the electrolyte, the mass content of the compound of formula III is i%, 0.001≤i≤5. By regulating the mass content of the compound of formula III within the scope of this application, the compound of formula III can improve the wettability of the electrolyte at the interface of the positive electrode and the negative electrode, and improve the fast charging performance, rate performance and cycle performance of the secondary battery.

[0028] In one embodiment of the present application, the compound of formula III includes at least one of the following compounds:

[0029]

[0030] The compound of formula III is selected to improve the wettability of the electrolyte at the interface between the positive electrode and the negative electrode, and further improve the fast charging performance, rate performance and cycle performance of the secondary battery.

[0031] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. Therefore, the electronic device provided by the present application has good fast charging performance and rate performance, as well as good high temperature storage performance and cycle performance.

[0032] Beneficial effects of this application:

[0033] The present application provides a secondary battery and an electronic device, wherein the secondary battery comprises a negative electrode sheet, an electrolyte and a positive electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer comprises a negative electrode active material, wherein the negative electrode active material comprises a graphite material matrix and amorphous carbon disposed on at least a portion of the surface of the graphite material matrix. In the Raman spectrum of the negative electrode active material, at 1300 cm -1 Up to 1400cm -1 There is a peak intensity of I in the range D The first characteristic peak at 1550cm -1 Up to 1650cm -1 There is a peak intensity of I in the range G The second characteristic peak, 0.2≤I D / I G ≤0.8. The electrolyte comprises at least one of the compound of formula I and the compound of formula II and vinylene carbonate, wherein the total mass content of the compound of formula I and the compound of formula II is y%, 0.001≤y≤3, and the mass content of vinylene carbonate is z%, 0.015≤(I D / I G) / (y+z)≤72.73. The secondary battery meets the above characteristics, and can have good high-temperature storage performance and cycle performance while having good fast charging performance and rate performance.

[0034] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. DETAILED DESCRIPTION

[0035] The technical solutions in this application will be described clearly and completely below in conjunction with the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application belong to the scope of protection of this application.

[0036] It should be noted that in the specific implementation manner of the present application, the present application is explained by taking a lithium-ion battery as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium-ion battery.

[0037] Using amorphous carbon to coat graphite materials can improve the fast charging performance and rate performance of secondary batteries. However, carbon coating will cause the defects of the negative electrode active materials to become larger, increase the active reaction area of ​​the negative electrode active materials and the electrolyte, increase side reactions, and further lead to an increase in the impedance growth rate during the high-temperature storage and cycling of the secondary battery.

[0038] The present application provides a secondary battery and an electronic device, wherein vinylene carbonate and at least one of the compounds of formula I and formula II containing at least one silicon-oxygen bond are simultaneously added to the electrolyte of the secondary battery, and at least one of the compounds of formula I and formula II can play a synergistic role with vinylene carbonate, quickly form a film on the negative electrode interface, cover the active sites on the surface of the negative electrode active material, reduce the reaction area between the negative electrode active material and the electrolyte, and effectively improve the high-temperature storage gas production increase and impedance growth problems of the coated graphite system during the cycle. By adding vinylene carbonate, at least one of the compounds of formula I and formula II with a specific content in the secondary battery, and matching the graphite negative electrode containing a carbon coating layer, the ion and electron conductivity of the secondary battery can be simultaneously improved, and the consumption rate of the electrolyte can be reduced, so that the secondary battery has good fast charging performance and rate performance, as well as good high-temperature storage performance and cycle performance.

[0039] The first aspect of the present application provides a secondary battery, which includes a negative electrode plate, an electrolyte and a positive electrode plate, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer includes a negative electrode active material, wherein the negative electrode active material includes a graphite material matrix and amorphous carbon disposed on at least a portion of the surface of the graphite material matrix. In the Raman spectrum of the negative electrode active material, at 1300 cm -1 Up to 1400cm -1 There is a peak intensity of I in the range D The first characteristic peak at 1550cm -1 Up to 1650cm -1 There is a peak intensity of I in the range G The second characteristic peak, 0.2≤I D / I G ≤0.8. The electrolyte comprises at least one of the compound of formula I and the compound of formula II and vinylene carbonate:

[0040]

[0041] Among them, R 11 , R 12 , R 13 and R 14 are each independently selected from a hydrogen atom, a halogen atom, a cyano group, an acetyl group, a substituted or unsubstituted C 1 To C 10 Alkyl, substituted or unsubstituted C 2 To C 10 Alkenyl, substituted or unsubstituted C 2 To C 10 Alkynyl, substituted or unsubstituted C 1 To C 10 Heteroatom-containing alkyl, substituted or unsubstituted C 2 To C 10 heteroatom-containing alkenyl, substituted or unsubstituted C 2 To C 10 Ester group, substituted or unsubstituted C 2 To C 10 An ester group containing a heteroatom; R 11 , R 12 , R 13 and R 14 Two adjacent groups in can be connected to form a ring;

[0042] R 21 is selected from substituted or unsubstituted C 1 To C 10 The alkyl group, R 22 is selected from substituted or unsubstituted C 2 To C10 alkenyl, n=1, 2 or 3;

[0043] When each group is substituted, the substituent is a halogen atom or a carbonyl group; the heteroatom is selected from Si, O or N. The halogen atom includes a fluorine atom. Based on the mass of the electrolyte, the total mass content of the compound of formula I and the compound of formula II is y%, 0.001≤y≤3, and the mass content of vinylene carbonate is z%, 0.015≤(I D / I G ) / (y+z)≤72.73, preferably, 0.033≤(I D / I G ) / (y+z)≤54.55, more preferably, 0.057≤(I D / I G ) / (y+z)≤45.45. Exemplarily, I D / I G The value of can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or a range consisting of any two of the above values; (I D / I G The value of ) / (y+z) can be 0.015, 0.033, 0.057, 1, 3, 5, 7, 10, 11, 13, 15, 17, 20, 21, 23, 25, 27, 30, 31, 33, 35, 37, 40, 45.45, 54.55, 72.73, or a range consisting of any two of the above values; the value of the total mass content y can be 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, or a range consisting of any two of the above values.

[0044] The inventors have found that by regulating the Raman spectrum of the negative electrode active material I D / I G The value of, the type and mass content of the compound of formula I and the compound of formula II in the electrolyte, the sum of the mass content of the compound of formula I and the compound of formula II and vinylene carbonate and I D / I G The relationship between the values ​​of and is within the scope of the present application, which can enable the secondary battery to have good fast charging performance and rate performance as well as good high temperature storage performance and cycle performance.

[0045] In one embodiment of the present application, 0.01≤z≤3. Exemplarily, the value of the mass content z can be 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3 or a range consisting of any two of the above values. By regulating the value of z within the scope of the present application, vinylene carbonate has a suitable mass content, and vinylene carbonate and at least one of the compounds of formula I and formula II can play a synergistic role, effectively improving the high-temperature storage gas production increase and impedance growth problems of the coated graphite system during the cycle, and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0046] In one embodiment of the present application, the compound of formula I includes at least one of the following compounds:

[0047]

[0048] The compound of formula I is selected. The compound of formula I can play a synergistic role with the vinylene carbonate in the electrolyte, effectively improving the problems of increased gas production during high-temperature storage and impedance growth during the cycle of the coated graphite system, and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0049] In one embodiment of the present application, the compound of formula II includes at least one of the following compounds:

[0050]

[0051] The compound of formula II is selected. The compound of formula II can play a synergistic role with the vinylene carbonate in the electrolyte, effectively improving the problems of increased gas production during high-temperature storage and impedance growth during the cycle of the coated graphite system, and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0052] In one embodiment of the present application, the mass ratio of the graphite material matrix to the amorphous carbon is 100:(0.1 to 5). Exemplarily, the mass ratio of the graphite material matrix to the amorphous carbon can be 100:0.1, 100:0.5, 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, 100:5 or a range consisting of any two of the above values. By regulating the mass ratio of the graphite material matrix to the amorphous carbon within the scope of the present application, the graphite material matrix and the amorphous carbon have a suitable mass content, which can further improve the fast charging performance and rate performance of the secondary battery.

[0053] In one embodiment of the present application, the graphitization degree of the negative electrode active material is e%, 94≤e≤96. By adjusting the graphitization degree of the negative electrode active material within the scope of the present application, the graphite particles can have better embedding and extraction capabilities with lithium ions, further improving the cycle performance of the secondary battery.

[0054] In one embodiment of the present application, the compaction density of the negative electrode material layer is fg / cm 3 , 1.5≤f≤1.8. By adjusting the compaction density of the negative electrode material layer within the scope of the present application, the volume energy density of the secondary battery can be further improved.

[0055] In one embodiment of the present application, the graphite material matrix includes at least one of natural graphite or artificial graphite. The use of the above graphite material matrix can enable the secondary battery to have better fast charging performance and rate performance.

[0056] In one embodiment of the present application, the electrolyte further includes a sulfur-oxygen double bond compound; the sulfur-oxygen double bond compound includes at least one of methane disulfonic acid methylene ester, 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, vinyl sulfate, 1,3-propane disulfonic anhydride, 2-methylbutane sultone or 1,3-propylene glycol cyclic sulfate. Since the above-mentioned sulfur-oxygen double bond compounds have strong antioxidant ability, the stability of the positive electrode interface can be effectively improved; on the other hand, the sulfur-oxygen double bond compounds have poor anti-reduction ability, and preferentially form an SEI film on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte at the negative electrode interface. Therefore, the use of sulfur-oxygen double bond compounds can further improve the cycle performance of secondary batteries.

[0057] Based on the mass of the electrolyte, the mass content of the sulfur-oxygen double bond compound is g%, 0.005≤g≤5. Exemplarily, the value of the mass content g can be 0.005, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or a range consisting of any two of the above values. By regulating the mass content of the sulfur-oxygen double bond compound within the scope of this application, the sulfur-oxygen double bond compound has a suitable mass content, and the sulfur-oxygen double bond compound can effectively reduce the reaction of the electrolyte at the positive electrode and the negative electrode; it can also better improve the stability of the positive electrode interface and the negative electrode interface, and at the same time, it can make the electrolyte have a suitable viscosity, so that the secondary battery has good cycle performance and high temperature storage performance.

[0058] In one embodiment of the present application, the electrolyte further includes a lithium-containing additive, and the lithium-containing additive includes at least one of lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium dioxalate borate, lithium tetrafluoroborate or lithium difluorooxalate borate. The electrolyte further includes a lithium-containing additive, and the above-mentioned lithium-containing additive is selected. The above-mentioned lithium-containing additive can form a film at the interface of the positive electrode and the negative electrode, effectively protecting the positive electrode interface and the negative electrode interface. The lithium-containing additive and the compound of formula I or the compound of formula II produce a synergistic effect, which can further improve the cycle performance of the secondary battery.

[0059] Based on the mass of the electrolyte, the mass content of the lithium-containing additive is h%, 0.005≤h≤2. Exemplarily, the value of the mass content h can be 0.005, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2 or a range consisting of any two of the above values. By regulating the mass content of the lithium-containing additive within the scope of this application, the lithium-containing additive can effectively protect the electrode interface and effectively improve the cycle performance of the secondary battery.

[0060] In one embodiment of the present application, the electrolyte further comprises at least one of the compounds of formula III:

[0061]

[0062] Among them, R 31 , R 33 Each independently selected from C 1 To C 4 The alkyl group, R 32 Selected from C 1 To C 4 of alkylene.

[0063] Based on the mass of the electrolyte, the mass content of the compound of formula III is i%, 0.001≤i≤5. Exemplarily, the value of the mass content i can be 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or a range consisting of any two of the above values. By regulating the mass content of the compound of formula III within the scope of this application, the compound of formula III can improve the wettability of the electrolyte at the interface of the positive electrode and the negative electrode, and improve the fast charging performance, rate performance and cycle performance of the secondary battery.

[0064] In one embodiment of the present application, the compound of formula III includes at least one of the following compounds:

[0065]

[0066] The compound of formula III is selected to improve the wettability of the electrolyte at the interface between the positive electrode and the negative electrode, and further improve the fast charging performance, rate performance and cycle performance of the secondary battery.

[0067] In the present application, the features of the different components contained in the above-mentioned electrolyte can be combined, and the implementation modes covered by the above-mentioned combination are all within the protection scope of the present application.

[0068] In the present application, the electrolyte includes a non-aqueous organic solvent and an electrolyte salt. The non-aqueous organic solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound or an aprotic solvent. The carbonate compound may include at least one of dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate or di-2,2,2-trifluoroethyl carbonate. The carboxylate compound may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate (EP), propyl propionate (PP), butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, γ-butyrolactone, 2,2-difluoroethyl acetate, valerolactone, butyrolactone, ethyl 2-fluoroacetate, ethyl 2,2-difluoroacetate or trifluoroacetic acid ethyl ester. The ether compound may include at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran or bis-2,2,2-trifluoroethyl ether. The aprotic solvent may include, but is not limited to, at least one of trimethyl phosphate, triethyl phosphate or trioctyl phosphate. In the present application, the electrolyte salt may include at least one of an organic lithium salt or an inorganic lithium salt. Exemplarily, the electrolyte salt may include lithium hexafluorophosphate (LiPF 6 ), Lithium Bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ) 2 , abbreviated as LiTFSI), lithium bis(fluorosulfonyl)imide (Li(N(SO 2 F) 2 ), LiFSI, LiCsF 6 ), lithium perchlorate (LiClO 4 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ) at least one of.

[0069] The present application has no particular restrictions on the mass content of the electrolyte salt and the non-aqueous organic solvent in the electrolyte, as long as the purpose of the present application can be achieved. For example, based on the mass of the electrolyte, the mass content of the electrolyte salt can be 5% to 20%, and the mass content of the remaining non-aqueous organic solvent, except for the compound of formula I and the compound of formula II, vinylene carbonate and the electrolyte salt, can be 62% to 94%.

[0070] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, electrolyte salt and non-aqueous organic solvent; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate and electrolyte salt is as described above, and the mass content of the non-aqueous organic solvent is 74% to 94% based on the mass of the electrolyte. The secondary battery including the above electrolyte has good fast charging performance and rate performance, as well as good high temperature storage performance and cycle performance.

[0071] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, a sulfur-oxygen double bond compound, an electrolyte salt, and a non-aqueous organic solvent; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate, a sulfur-oxygen double bond compound, and an electrolyte salt is as described above, and the mass content of the non-aqueous organic solvent is 69% to 94% based on the mass of the electrolyte. The sulfur-oxygen double bond compound has a strong antioxidant capacity and can effectively improve the stability of the positive electrode interface; on the other hand, the sulfur-oxygen double bond compound has a poor anti-reduction ability and preferentially forms an SEI film on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte at the negative electrode interface, further enhancing the stability of the interface, and further improving the cycle performance of the secondary battery.

[0072] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, lithium-containing additives, electrolyte salts and non-aqueous organic solvents; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate, lithium-containing additives and electrolyte salts is as described above, and the mass content of the non-aqueous organic solvent is 72% to 94% based on the mass of the electrolyte. The lithium-containing additive can form a film at the interface of the positive electrode and the negative electrode, effectively protecting the positive electrode interface and the negative electrode interface, and the lithium-containing additive has a synergistic effect with the compound of formula I or the compound of formula II, which can further improve the cycle performance of the secondary battery.

[0073] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, a compound of formula III, an electrolyte salt and a non-aqueous organic solvent; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate, a compound of formula III and an electrolyte salt is as described above, and the mass content of the non-aqueous organic solvent is 69% to 94% based on the mass of the electrolyte. The compound of formula III can improve the wettability of the electrolyte at the interface of the positive electrode and the negative electrode, and further improve the fast charging performance, rate performance and cycle performance of the secondary battery.

[0074] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, sulfur-oxygen double bond compounds, lithium-containing additives, electrolyte salts and non-aqueous organic solvents; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate, sulfur-oxygen double bond compounds, lithium-containing additives and electrolyte salts is as described above, and the mass content of the non-aqueous organic solvent is 67% to 94% based on the mass of the electrolyte. The sulfur-oxygen double bond compound has a strong antioxidant capacity and can effectively improve the stability of the positive electrode interface; on the other hand, the sulfur-oxygen double bond compound has a poor anti-reduction ability and preferentially forms an SEI film on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte at the negative electrode interface, further enhancing the stability of the interface, and further improving the cycle performance of the secondary battery. The lithium-containing additive can form a film at the interface of the positive electrode and the negative electrode, effectively protecting the positive electrode interface and the negative electrode interface. The lithium-containing additive has a synergistic effect with the compound of formula I or the compound of formula II, which can further improve the cycle performance of the secondary battery.

[0075] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, a sulfur-oxygen double bond compound, a compound of formula III, an electrolyte salt and a non-aqueous organic solvent; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate, a sulfur-oxygen double bond compound, a compound of formula III and an electrolyte salt is as described above, and the mass content of the non-aqueous organic solvent is 64% to 94% based on the mass of the electrolyte. The sulfur-oxygen double bond compound has a strong antioxidant capacity and can effectively improve the stability of the positive electrode interface; on the other hand, the sulfur-oxygen double bond compound has a poor anti-reduction ability and preferentially forms an SEI film on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte at the negative electrode interface, further enhancing the stability of the interface, and further improving the cycle performance of the secondary battery. The compound of formula III can improve the wettability of the electrolyte at the positive and negative electrode interfaces, and further improve the fast charging performance, rate performance and cycle performance of the secondary battery.

[0076] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, lithium-containing additives, compounds of formula III, electrolyte salts and non-aqueous organic solvents; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate, lithium-containing additives, compounds of formula III and electrolyte salts is as described above, and the mass content of the non-aqueous organic solvent is 67% to 94% based on the mass of the electrolyte. The lithium-containing additive can form a film at the interface of the positive electrode and the negative electrode, effectively protecting the positive electrode interface and the negative electrode interface, and the lithium-containing additive and the compound of formula I or the compound of formula II produce a synergistic effect, which can further improve the cycle performance of the secondary battery. The compound of formula III can improve the wettability of the electrolyte at the interface of the positive electrode and the negative electrode, and further improve the fast charging performance, rate performance and cycle performance of the secondary battery.

[0077] In one embodiment of the present application, the electrolyte may include at least one of the compounds of formula I and formula II, vinylene carbonate, a sulfur-oxygen double bond compound, a lithium-containing additive, a compound of formula III, an electrolyte salt and a non-aqueous organic solvent; the mass content of at least one of the compounds of formula I and formula II, vinylene carbonate, a sulfur-oxygen double bond compound, a lithium-containing additive, a compound of formula III and an electrolyte salt is as described above, and the mass content of the non-aqueous organic solvent is 62% to 94% based on the mass of the electrolyte. The sulfur-oxygen double bond compound has a strong antioxidant capacity and can effectively improve the stability of the positive electrode interface; on the other hand, the sulfur-oxygen double bond compound has a poor anti-reduction ability and preferentially forms an SEI film on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte at the negative electrode interface, further enhancing the stability of the interface, and further improving the cycle performance of the secondary battery. The lithium-containing additive can form a film at the interface of the positive electrode and the negative electrode, effectively protecting the positive electrode interface and the negative electrode interface. The lithium-containing additive has a synergistic effect with the compound of formula I or the compound of formula II, which can further improve the cycle performance of the secondary battery. The compound of formula III can improve the wettability of the electrolyte at the interface between the positive electrode and the negative electrode, and further improve the rapid charging performance, rate performance and cycle performance of the secondary battery.

[0078] In the present application, the secondary battery includes a negative electrode plate, and the negative electrode plate includes a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer arranged on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be arranged on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the negative electrode current collector or a partial area of ​​the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the negative electrode current collector, as long as the purpose of this application can be achieved. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or a composite current collector, etc.

[0079] The present application has no particular limitation on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved, for example, the thickness of the negative electrode current collector is 1 μm to 16 μm. The present application has no particular limitation on the thickness of the negative electrode material layer, as long as the purpose of the present application can be achieved, for example, the thickness of the single-sided negative electrode material layer is 10 μm to 120 μm.

[0080] The negative electrode material layer of the present application may also include a binder. The present application has no particular restrictions on the binder in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the binder may include lithium polyacrylate, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose (CMC-Na), polyvinyl acetate, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyaniline, polyimide, polyamide-imide, polysiloxane, epoxy resin, polyester resin, polyurethane resin or polyfluorene, etc. At least one of the above. The negative electrode material layer of the present application may also include a conductive agent. The present application has no particular restrictions on the conductive agent in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent may include at least one of conductive carbon black, lamellar graphite, graphene, carbon nanotubes, carbon nanowires or carbon fibers. The above-mentioned conductive carbon black may include at least one of Super P, acetylene black or Ketjen black. The above-mentioned carbon nanotubes may include but are not limited to at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes or few-walled carbon nanotubes. The above-mentioned carbon fiber may include but is not limited to at least one of vapor-grown carbon fiber (VGCF) or nano-carbon fiber. The present application has no particular restrictions on the mass ratio of the negative electrode active material, binder and conductive agent in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0081] Optionally, the negative electrode plate may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, which may be at least one of the above conductive agent and the above binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art may select according to actual needs, as long as the purpose of the present application can be achieved.

[0082] In the present application, the secondary battery includes a positive electrode plate, and the positive electrode plate includes a positive electrode collector and a positive electrode material layer arranged on at least one surface of the positive electrode collector. The above-mentioned "positive electrode material layer arranged on at least one surface of the positive electrode collector" means that the positive electrode material layer can be arranged on one surface of the positive electrode collector along the thickness direction of itself, or on two surfaces of the positive electrode collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the positive electrode collector or a partial area of ​​the positive electrode collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the positive electrode collector, as long as the purpose of this application can be achieved. For example, it can include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0083] The positive electrode material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance that can reversibly embed and extract active ions such as lithium ions. The positive electrode material layer can be one layer or more layers, and each layer of the multi-layer positive electrode material layer can contain the same or different positive electrode active materials. The present application has no particular restrictions on the positive electrode active material, as long as the purpose of the present application can be achieved. For example, the positive electrode active material can include but is not limited to lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO 2 ), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate. The above-mentioned lithium nickel cobalt manganese oxide may include LiNi 0.95 Co 0.03 Mn 0.02 O 2 (Ni95), LiNi 0.91 Co 0.03 Mn 0.06 O 2 (Ni91), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O 2(NCM622), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 At least one of (NCM111). The above-mentioned lithium manganese iron phosphate may include LiMn 0.6 Fe 0.4 PO 4 . The positive electrode material layer of the present application may further include a binder. The present application has no special restrictions on the binder in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the binder may be at least one of the above-mentioned binders. The positive electrode material layer of the present application may further include a conductive agent. The present application has no special restrictions on the conductive agent in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent may be at least one of the above-mentioned conductive agents. The present application has no special restrictions on the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0084] The present application has no particular limitation on the thickness of the positive electrode current collector, as long as the purpose of the present application can be achieved, for example, the thickness of the positive electrode current collector is 1 μm to 20 μm. The present application has no particular limitation on the thickness of the positive electrode material layer, as long as the purpose of the present application can be achieved, for example, the thickness of the single-sided positive electrode material layer is 10 μm to 120 μm.

[0085] Optionally, the positive electrode plate may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, which may be at least one of the above conductive agent and the above binder. The present application has no particular restrictions on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art may select according to actual needs, as long as the purpose of the present application can be achieved.

[0086] In the present application, the secondary battery also includes a diaphragm, which is used to separate the positive electrode plate and the negative electrode plate, prevent the internal short circuit of the secondary battery, allow the electrolyte ions to pass freely, and do not affect the electrochemical charge and discharge process. The present application has no special restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include but is not limited to polyethylene (PE), polypropylene-based polyolefins (PO), polyesters (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0087] In the present application, the diaphragm may include a substrate and a surface treatment layer. The substrate may be a non-woven fabric or a composite film having a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. For example, polyethylene may be selected from at least one of high-density polyethylene, low-density polyethylene or ultra-high molecular weight polyethylene. Preferably, the material of the substrate may include polyethylene and polypropylene. The selection of polyethylene and polypropylene as the material of the substrate has a good effect on preventing short circuits, and can improve the stability of the secondary battery through the shutdown effect. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder. The present application has no particular restrictions on the above-mentioned inorganic particles, for example, it may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The present application has no particular restrictions on the binder in the inorganic layer, for example, it may be at least one of the aforementioned binders. The inorganic layer can improve the heat resistance, oxidation resistance and electrolyte wetting performance of the diaphragm, and enhance the adhesion between the diaphragm and the pole piece. The polymer layer contains a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene). The surface treatment layer may be a porous layer. In some embodiments of the present application, the pores of the diaphragm have a diameter in the range of about 0.01 μm to 1 μm. The present application has no particular limitation on the thickness of the separator, as long as the purpose of the present application can be achieved. For example, the thickness of the separator may be 3 μm to 20 μm.

[0088] The secondary battery of the present application also includes a packaging bag for accommodating a positive electrode plate, a separator, a negative electrode plate and an electrolyte, as well as other components known in the art in the secondary battery, and the present application does not limit the above-mentioned other components. The present application has no special restrictions on the packaging bag, which can be a packaging bag known in the art, as long as it can achieve the purpose of the present application. For example, the packaging bag can be a rigid packaging bag or a flexible packaging bag. The rigid packaging bag can be metal; the flexible packaging bag can be a metal plastic film, and the metal plastic film can be an aluminum plastic film or a steel plastic film.

[0089] The present application does not particularly limit the type of secondary battery, which may include any device that undergoes an electrochemical reaction. In the present application, the secondary battery may include, but is not limited to: a lithium metal secondary battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery or a lithium ion polymer secondary battery (lithium ion polymer battery), etc.

[0090] The preparation process of the secondary battery of the present application is well known to those skilled in the art, and the present application has no special restrictions. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and then fixing the four corners of the entire stacked structure with tape to obtain an electrode assembly of a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain a secondary battery. In addition, overcurrent protection elements, guide plates, etc. may also be placed in the packaging bag as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.

[0091] The second aspect of the present application provides an electronic device, which includes the secondary battery in any of the above embodiments. Therefore, the electronic device provided by the present application has good fast charging performance and rate performance, as well as good high temperature storage performance and cycle performance.

[0092] The present application does not particularly limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device can include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0093] Example

[0094] The following examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0095] Test methods and equipment:

[0096] Fast charging performance test:

[0097] Place the lithium-ion battery in a 25°C constant temperature environment and leave it for 30 minutes to allow the lithium-ion battery to reach a constant temperature. Charge the lithium-ion battery that has reached a constant temperature at a constant current of 3C to a voltage of 4.3V, then charge it at a constant current of 1C to 4.35V, and then charge it at a constant voltage until the current is less than or equal to 0.05C. Record the charging time T of this process.

[0098] Rate performance test:

[0099] The lithium-ion battery was placed in a 25°C constant temperature environment and allowed to stand for 30 minutes to reach a constant temperature. The constant temperature lithium-ion battery was charged at a 1C constant current to a voltage of 4.3V, then charged at a 4.3V constant voltage to a current of less than or equal to 0.05C, allowed to stand for 5 minutes, and discharged at a 1C constant current to 2.5V, and the 1C discharge capacity of the lithium-ion battery was obtained.

[0100] The lithium-ion battery is charged at a constant current of 1C to a voltage of 4.3V, then charged at a constant voltage of 4.3V to a current of less than or equal to 0.05C, left to stand for 5 minutes, and discharged at a constant current of 5C to 2.5V to obtain the 5C discharge capacity of the lithium-ion battery. The 5C discharge capacity is divided by the 1C discharge capacity to obtain the 5C capacity retention rate.

[0101] 5C capacity retention rate (%) = 5C discharge capacity / 1C discharge capacity × 100%.

[0102] Cycle performance test:

[0103] Place the lithium-ion battery in a constant temperature environment at 25°C and let it stand for 30 minutes to allow the lithium-ion battery to reach a constant temperature. Charge the lithium-ion battery that has reached a constant temperature at a constant current of 1C to a voltage of 4.3V, then charge it at a constant voltage of 4.3V to a current of less than or equal to 0.05C, let it stand for 5 minutes, and then discharge it at a constant current of 1C to a voltage of 2.5V. This is a charge and discharge cycle. The discharge capacity obtained at this time is recorded as the first discharge capacity C0. With the first discharge capacity as 100%, repeat the charge and discharge cycle. When the cycle is 800 times, stop the test and record the discharge capacity of the lithium-ion battery at this time, which is recorded as the discharge capacity C1 after 800 cycles. Calculate the cycle capacity retention rate of the lithium-ion battery according to the following formula.

[0104] Cycle capacity retention rate (%) = C1 / C0×100%.

[0105] High temperature storage performance test:

[0106] Place the lithium-ion battery in a constant temperature environment of 25°C and let it stand for 30 minutes to allow the lithium-ion battery to reach a constant temperature. Charge the lithium-ion battery that has reached a constant temperature to 4.3V at a constant current of 1C, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.05C, then let it stand for 5 minutes, then discharge it to 2.5V at a constant current of 1C, then charge it to 4.3V at a constant current of 1C, then charge it to a current of less than or equal to 0.05C at a constant voltage of 4.3V, and record the thickness of the lithium-ion battery at this time, which is recorded as the initial thickness. Then transfer the lithium-ion battery to a 60°C constant temperature box for storage for 90 days. After 90 days of storage, take out the lithium-ion battery and observe and test its thickness, which is recorded as the thickness after high-temperature storage. Calculate the high-temperature storage thickness expansion rate of the lithium-ion battery according to the following formula, and use it as an indicator to evaluate the high-temperature storage performance of the lithium-ion battery.

[0107] High temperature storage thickness expansion ratio (%) = (thickness after high temperature storage - initial thickness) / initial thickness × 100%.

[0108] I D / I G test:

[0109] An area of ​​100 μm × 100 μm was selected on the negative electrode material layer, and the particles in the area were scanned using a laser microscopic confocal Raman spectrometer (Raman, HR Evolution, HORIBA Scientific Instrument Division) to obtain the D peak and G peak of all particles within the area. The data were processed using LabSpec software to obtain the peak intensities of the D peak and G peak of each particle, which were I D and I G The laser wavelength of the Raman spectrometer can be in the range of 532nm to 785nm. D / I G The value is the I of all particles measured in this range. D and I G The average value of the ratio.

[0110] Compaction density test of negative electrode material layer:

[0111] Disassemble the lithium-ion battery to obtain the negative electrode sheet (double-sided coating), and cut the area of ​​the negative electrode sheet coated with the negative electrode material layer to 1540.25mm 2 Weigh the small disc m 1 And test its thickness d 1 At the same time, the blank collector area of ​​the negative electrode sheet is cut to an area of ​​1540.25mm2 Weigh the small disc m 0 And test its thickness d 0 , compacted density = (m 1 -m 0 ) / [1540.25×(d 1 -d 0 )].

[0112] Example 1-1

[0113] <Preparation of positive electrode sheet>

[0114] The positive electrode active material LiMn 0.6 Fe 0.4 PO 4 , acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder are mixed in a mass ratio of 96:2:2, and N-methylpyrrolidone (NMP) is added as a solvent. The system is stirred under the action of a vacuum mixer until the system becomes a uniform positive electrode slurry with a solid content of 75wt%. The positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil; the coated aluminum foil is dried at 85°C, and then after cold pressing, cutting, and slitting, it is dried under vacuum conditions at 85°C for 4h to obtain a positive electrode sheet.

[0115] <Preparation of negative electrode active material>

[0116] (1) Crushing: Crushing the coke precursor petroleum coke to obtain single particles;

[0117] (2) Granulation: The primary single particles are mixed with phenolic resin and transferred to an inert atmosphere of nitrogen for granulation at a temperature of 500° C. for 2 h to obtain secondary particles; wherein the mass ratio of the primary single particles to the phenolic resin is 100:3;

[0118] (3) Graphitization: The secondary particles are graphitized at a temperature of 3000° C. for 40 h to obtain a graphite material matrix;

[0119] (4) Coating: coating the graphite material substrate with carbon source asphalt to obtain coated particles;

[0120] (5) Carbonization: The coated particles are calcined in an inert atmosphere of nitrogen at a temperature of 1000°C for 3 hours, and then naturally cooled to room temperature to obtain a negative electrode active material of artificial graphite coated with an amorphous carbon layer.

[0121] The negative electrode active material includes a graphite material matrix, artificial graphite, and amorphous carbon disposed on the surface of the artificial graphite. The mass ratio of the graphite material matrix and the amorphous carbon is shown in Table 1.

[0122] <Preparation of negative electrode sheet>

[0123] The negative electrode active material, conductive agent Super P, thickener sodium carboxymethyl cellulose (CMC-Na), and binder styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:2:0.8:1.2, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer, wherein the solid content of the negative electrode slurry was 54wt%; the negative electrode slurry was stirred at a negative electrode active material area density of 7.8mg / cm 2 The negative electrode is evenly coated on the negative electrode current collector copper foil; the coated copper foil is dried at 85°C, and then cold pressed, cut and slit, and then dried at 120°C under vacuum conditions for 12 hours to obtain a negative electrode sheet.

[0124] <Preparation of Electrolyte>

[0125] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate, ethyl methyl carbonate, and ethyl acetate were mixed in a mass ratio of 3:3:4 to obtain a base solvent, and then an electrolyte salt, lithium hexafluorophosphate (LiPF 6 ), vinylene carbonate and the compound of formula I-1 are uniformly mixed to obtain an electrolyte. Wherein, based on the mass of the electrolyte, the mass content of the electrolyte salt is 12.5%, the mass content of vinylene carbonate is z% is 1.5%, the mass content of the compound of formula I is y% is 0.5%, and the balance is the base solvent.

[0126] <Preparation of Separator>

[0127] A polyethylene (PE) film with a thickness of 15 μm (provided by Celgard) was used.

[0128] <Preparation of lithium-ion batteries>

[0129] The negative electrode sheet, separator, positive electrode sheet and separator prepared above are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, and after drying, the electrolyte is injected, and a lithium-ion battery is obtained through vacuum packaging, standing, formation, degassing and trimming processes.

[0130] Example 1-2 to Example 1-23

[0131] Except for adjusting the relevant preparation parameters in <Preparation of negative electrode active material>, <Preparation of negative electrode sheet>, and <Preparation of electrolyte> according to Table 1, the rest is the same as Example 1-1. Among them, when the mass content of the compound of formula I and / or the compound of formula II and vinylene carbonate changes, the mass content of the basic solvent changes accordingly, the mass ratio of vinyl carbonate, ethyl methyl carbonate, and ethyl acetate remains unchanged, and the mass content of the electrolyte salt remains unchanged.

[0132] Example 2-1 to Example 2-10

[0133] Except for further adding at least one of the sulfur-oxygen double bond compound (mass content is g%), the lithium-containing additive (mass content is h%), and the compound of formula III (mass content is i%) in <Preparation of electrolyte>, the rest is the same as Example 1-1. Among them, when the mass content of at least one of the sulfur-oxygen double bond compound, the lithium-containing additive, and the compound of formula III changes, the mass content of the base solvent changes accordingly, the mass ratio of ethylene carbonate, ethyl methyl carbonate, and ethyl acetate remains unchanged, and the mass content of the electrolyte salt, the compound of formula I and / or the compound of formula II, and vinylene carbonate remains unchanged.

[0134] Comparative Example 1-1 to Comparative Example 1-3

[0135] Except for adjusting the relevant preparation parameters in <Preparation of Electrolyte> according to Table 1, the rest is the same as Example 1-1. Among them, when the mass content of the compound of formula I and / or the compound of formula II and vinylene carbonate changes, the mass content of the base solvent changes accordingly, the mass ratio of vinyl carbonate, ethyl methyl carbonate and ethyl acetate remains unchanged, and the mass content of the electrolyte salt remains unchanged.

[0136] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 and 2.

[0137] Table 1

[0138]

[0139] Note: In Table 1, “ / ” indicates no relevant preparation parameters.

[0140] Referring to Table 1, it can be seen from Examples 1-1 to 1-23 and Comparative Examples 1-1 to 1-3 that by adjusting the Raman spectrum of the negative electrode active material, D / I G The value of, the type and mass content of the compound of formula I and the compound of formula II in the electrolyte, the sum of the mass content of the compound of formula I and the compound of formula II and vinylene carbonate and I D / I G The relationship between the values ​​of is within the scope of this application, the charging time of the lithium-ion battery is short, the 5C capacity retention rate is high, the high-temperature storage thickness expansion rate is low, and the cycle capacity retention rate is high, which means that the lithium-ion battery has good fast charging performance and rate performance, as well as good high-temperature storage performance and cycle performance.

[0141] The mass ratio of the graphite material matrix to the amorphous carbon usually affects the fast charging performance and rate performance of the lithium-ion battery. It can be seen from Examples 1-1 to 1-3 that when the mass ratio of the graphite material matrix to the amorphous carbon is within the scope of this application, the charging time of the lithium-ion battery is shorter, the 5C capacity retention rate is higher, the high-temperature storage thickness expansion rate is lower, and the cycle capacity retention rate is higher, indicating that the lithium-ion battery has good fast charging performance and rate performance, as well as good high-temperature storage performance and cycle performance.

[0142] The mass content of vinylene carbonate usually affects the high temperature storage performance and cycle performance of lithium-ion batteries. It can be seen from Examples 1-6 to 1-17 that when the mass content of vinylene carbonate is within the scope of this application, the charging time of the lithium-ion battery is shorter, the 5C capacity retention rate is higher, the high temperature storage thickness expansion rate is lower, and the cycle capacity retention rate is higher, indicating that the lithium-ion battery has good high temperature storage performance and cycle performance, as well as good fast charging performance and rate performance.

[0143] It can be seen from Examples 1-18 to 1-21 that by selecting the compound of formula I and / or the compound of formula II of the present application, the charging time of the lithium ion battery is shorter, the 5C capacity retention rate is higher, the high-temperature storage thickness expansion rate is lower, and the cycle capacity retention rate is higher, indicating that the lithium ion battery has good fast charging performance and rate performance, as well as good high-temperature storage performance and cycle performance.

[0144] The compaction density of the negative electrode material layer usually affects the volume energy density of the lithium-ion battery. It can be seen from Examples 1-1, 1-22 and 1-23 that when the compaction density of the negative electrode material layer is within the scope of this application, the charging time of the lithium-ion battery is shorter, the 5C capacity retention rate is higher, the high-temperature storage thickness expansion rate is lower, and the cycle capacity retention rate is higher, indicating that the lithium-ion battery has good fast charging performance and rate performance, as well as good high-temperature storage performance and cycle performance, and also has a higher volume energy density.

[0145] Table 2

[0146]

[0147]

[0148] Note: In Table 2, “ / ” indicates no relevant preparation parameters.

[0149] The electrolyte also includes a sulfur-oxygen double bond compound, and the type and mass content of the sulfur-oxygen double bond compound usually affect the cycle performance and high-temperature storage performance of the lithium-ion battery. It can be seen from Example 2-1 to Example 2-3 that when the type and mass content of the sulfur-oxygen double bond compound are within the scope of this application, the charging time of the lithium-ion battery is shorter, the 5C capacity retention rate is higher, the high-temperature storage thickness expansion rate is lower, and the cycle capacity retention rate is higher, indicating that the lithium-ion battery has good cycle performance and high-temperature storage performance, as well as good fast charging performance and rate performance.

[0150] The electrolyte also includes a lithium-containing additive, and the type and mass content of the lithium-containing additive usually affect the cycle performance of the lithium-ion battery. It can be seen from Examples 2-4 to 2-6 that when the type and mass content of the lithium-containing additive are within the scope of this application, the charging time of the lithium-ion battery is shorter, the 5C capacity retention rate is higher, the high-temperature storage thickness expansion rate is lower, and the cycle capacity retention rate is higher, indicating that the lithium-ion battery has good cycle performance, and also has good high-temperature storage performance, fast charging performance and rate performance.

[0151] The electrolyte also includes a compound of formula III, and the type and mass content of the compound of formula III usually affect the fast charging performance, rate performance and cycle performance of the lithium ion battery. It can be seen from Examples 2-7 to 2-9 that when the type and mass content of the compound of formula III are within the scope of this application, the charging time of the lithium ion battery is shorter, the 5C capacity retention rate is higher, the high-temperature storage thickness expansion rate is lower, and the cycle capacity retention rate is higher, indicating that the lithium ion battery has good fast charging performance, rate performance and cycle performance, and also has good high-temperature storage performance.

[0152] It can be seen from Example 2-2, Example 2-5, Example 2-8, and Example 2-10 that when the electrolyte includes a sulfur-oxygen double bond compound, a lithium-containing additive, and a compound of formula III, and the mass contents of the sulfur-oxygen double bond compound, the lithium-containing additive, and the compound of formula III are within the scope of the present application, the charging time of the lithium-ion battery is short, the 5C capacity retention rate is high, the high-temperature storage thickness expansion rate is low, and the cycle capacity retention rate is high, indicating that the lithium-ion battery has good fast charging performance and rate performance, as well as good high-temperature storage performance and cycle performance.

[0153] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method or article.

[0154] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0155] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A secondary battery, comprising a negative electrode sheet, an electrolyte and a positive electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer comprises a negative electrode active material, wherein the negative electrode active material comprises a graphite material matrix and amorphous carbon disposed on at least a portion of the surface of the graphite material matrix; In the Raman spectrum of the negative electrode active material, at 1300 cm -1 Up to 1400cm -1 There is a peak intensity of I in the range D The first characteristic peak at 1550cm -1 Up to 1650cm -1 There is a peak intensity of I in the range G The second characteristic peak, 0.2≤I D / I G ≤0.8; The electrolyte comprises at least one of a compound of formula I and a compound of formula II and vinylene carbonate: in, R 11 , R 12 , R 13 and R 14 are each independently selected from a hydrogen atom, a halogen atom, a cyano group, an acetyl group, a substituted or unsubstituted C1 to C 10 alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 alkynyl, substituted or unsubstituted C1 to C 10 alkyl containing heteroatoms, substituted or unsubstituted C2 to C 10 heteroatom-containing alkenyl, substituted or unsubstituted C2 to C 10 ester group, substituted or unsubstituted C2 to C 10 An ester group containing a heteroatom; R 11 , R 12 , R 13 and R 14 Two adjacent groups in can be connected to form a ring; R 21 is selected from substituted or unsubstituted C1 to C 10 The alkyl group, R 22 is selected from substituted or unsubstituted C2 to C 10 alkenyl, n=1, 2 or 3; When each group is substituted, the substituent is a halogen atom or a carbonyl group; the heteroatom is selected from Si, O or N; Based on the mass of the electrolyte, the total mass content of the compound of formula I and the compound of formula II is y%, 0.001≤y≤3, and the mass content of the vinylene carbonate is z%, 0.015≤(I D / I G ) / (y+z)≤72.

73.

2. The secondary battery according to claim 1, wherein 0.033≤(I D / I G ) / (y+z)≤54.55。 3. The secondary battery according to claim 2, wherein: 0.057≤(I D / I G ) / (y+z)≤45.45。 4. The secondary battery according to claim 1, wherein 0.01≤z≤3。 5. The secondary battery according to claim 1, wherein The compound of formula I comprises at least one of the following compounds:

6. The secondary battery according to claim 1, wherein The compound of formula II includes at least one of the following compounds:

7. The secondary battery according to claim 1, wherein The mass ratio of the graphite material matrix to the amorphous carbon is 100:(0.1 to 5).

8. The secondary battery according to claim 1, which satisfies at least one of the following characteristics: (1) The compaction density of the negative electrode material layer is fg / cm 3 , 1.5≤f≤1.8; (2) The graphite material matrix includes at least one of natural graphite or artificial graphite.

9. The secondary battery according to claim 1, wherein The electrolyte further comprises a sulfur-oxygen double bond compound; the sulfur-oxygen double bond compound comprises at least one of methanedisulfonic acid methylene ester, 1,3-propane sultone, 1,4-butane sultone, propenyl-1,3-sultone, vinyl sulfate, 1,3-propanedisulfonic anhydride, 2-methylbutane sultone or 1,3-propylene glycol cyclic sulfate; Based on the mass of the electrolyte, the mass content of the sulfur-oxygen double bond compound is g%, and 0.005≤g≤5.

10. The secondary battery according to claim 1, wherein The electrolyte further includes a lithium-containing additive, wherein the lithium-containing additive includes at least one of lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium dioxalate borate, lithium tetrafluoroborate or lithium difluorooxalate borate; Based on the mass of the electrolyte, the mass content of the lithium-containing additive is h%, and 0.005≤h≤2.

11. The secondary battery according to claim 1, wherein The electrolyte further comprises at least one of the compounds of formula III: Among them, R 31 , R 33 are each independently selected from C1 to C4 alkyl groups, R 32 an alkylene group selected from C1 to C4; Based on the mass of the electrolyte, the mass content of the compound of formula III is i%, and 0.001≤i≤5.

12. The secondary battery according to claim 11, wherein The compound of formula III includes at least one of the following compounds: 13 . An electronic device comprising the secondary battery according to claim 1 .

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