Electrolyte for secondary battery, secondary battery, battery module, battery pack, and electrical device using the same

Abstract

The present application relates to an electrolyte for a secondary battery, a secondary battery, a battery module, a battery pack, and an electric device. The electrolyte for the secondary battery includes an oxygen free radical scavenger. The oxygen free radical scavenger in the electrolyte can capture the oxygen-containing free radicals generated by side reactions in the secondary battery and suppress the generation of oxygen, thereby improving the safety and stability of the secondary battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and particularly relates to an electrolyte for a secondary battery, a secondary battery, a battery module, a battery pack, and an electrical device. Background Art

[0002] Secondary batteries such as lithium-ion batteries have the advantages of high energy density, no memory effect, and good cycle performance, and are widely used. However, the active materials in secondary batteries are prone to side reactions to generate gas at the interface between the electrode and the electrolyte, thus affecting the safety and cycle stability of secondary batteries. Summary of the Invention

[0003] Based on the above problems, the present application provides an electrolyte for a secondary battery, a secondary battery, a battery module, a battery pack, and an electrical device, which can improve the gas generation, especially the oxygen generation problem of secondary batteries, and enhance the safety and stability of secondary batteries.

[0004] In one aspect of the present application, there is provided an electrolyte for a secondary battery, including an oxygen free radical scavenger.

[0005] The above electrolyte for a secondary battery includes an oxygen free radical scavenger, which can capture the oxygen-containing free radicals generated by side reactions in the secondary battery, curb the generation of oxygen, and enhance the safety and stability of the secondary battery.

[0006] In some embodiments, the oxygen free radical scavenger is an organic nitrogen oxide. Organic nitrogen oxides have high reactivity with oxygen-containing free radicals and can effectively improve the problem of gas generation from side reactions in the above electrolyte for a secondary battery.

[0007] In some embodiments, the oxygen free radical scavenger includes at least one of the compounds represented by Formula I, Formula II, and Formula III:

[0008]

[0009] Wherein, R1 is selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted phenyl, heteroaryl, and ester group; R2 is selected from one of substituted or unsubstituted alkyl and substituted or unsubstituted phenyl; R3 is selected from one of H and substituted or unsubstituted alkyl;

[0010] R4 is selected from one of H, aldehyde group, cyano group, substituted or unsubstituted alkyl, and substituted or unsubstituted phenyl; R5 is selected from one of substituted or unsubstituted alkyl, ester group, phosphonic acid group, amide group, vinyl, and substituted or unsubstituted phenyl; R6 is selected from one of H and substituted or unsubstituted alkyl;

[0011] R7 is selected from one of H, amino, amido, cyano, isothiocyanato, carboxyl, ester, hydroxyl, and alkoxy.

[0012] In some embodiments, R1 is selected from one of halo C1-C6 alkyl, substituted or unsubstituted phenyl, C4-C5 heteroaryl, and C2-C6 ester; R2 is selected from one of unsubstituted C1-C6 linear alkyl, unsubstituted C3-C6 cyclic alkyl, and substituted or unsubstituted phenyl; R3 is selected from one of H and unsubstituted C1-C6 alkyl.

[0013] R4 is selected from one of H, aldehyde, cyano, unsubstituted C1-C6 alkyl, and substituted or unsubstituted phenyl; R5 is selected from one of unsubstituted C1-C6 alkyl, C1-C6 ester, phosphonic acid, amido, vinyl, and unsubstituted phenyl; R6 is selected from one of H and unsubstituted C1-C6 alkyl.

[0014] In some embodiments, in formula I: R1 is selected from one of halo C1-C6 alkyl, substituted or unsubstituted phenyl, pyridyl, pyridyl-N-oxide, and C2-C6 ester, R2 is selected from unsubstituted C1-C6 alkyl, and R3 is selected from one of H and methyl; or, R1 is selected from one of substituted or unsubstituted phenyl and C4-C5 heteroaryl, R2 is selected from substituted or unsubstituted phenyl, and R3 is H.

[0015] In some embodiments, in formula II, R4 is H, R5 is selected from one of unsubstituted C1-C6 alkyl, C1-C6 ester, phosphonic acid, amido, and unsubstituted phenyl, and R6 is selected from one of H and unsubstituted C1-C6 alkyl; or, R4 is selected from unsubstituted C1-C6 alkyl, R5 is selected from one of unsubstituted C1-C6 alkyl, vinyl, and unsubstituted phenyl, and R6 is selected from one of H and unsubstituted C1-C6 alkyl; or, R4 is selected from substituted or unsubstituted phenyl, R5 is selected from unsubstituted C1-C6 alkyl, and R6 is selected from unsubstituted C1-C6 alkyl.

[0016] In some embodiments, R1 is a phenyl substituted by substituent R 11 wherein the substituent R 11 is selected from one of alkyl, halogen, alkoxy, nitro, and amino.

[0017] In some embodiments, R2 is a phenyl substituted by substituent R 21 wherein the substituent R 21 is selected from one of alkyl and halogen.

[0018] In some of these embodiments, R4 is a substituted phenyl group, and the substituent is a halogen.

[0019] In some of these embodiments, the oxygen radical scavenger is selected from at least one of the compounds represented by the following structural formulas:

[0020]

[0021]

[0022]

[0023]

[0024]

[0025] By selecting the oxygen radical scavenger with the above structure, the electrolyte for secondary batteries has good oxygen radical reaction activity, which can improve the safety and stability of secondary batteries.

[0026] In some of these embodiments, in the electrolyte for secondary batteries, the mass percentage of the oxygen radical scavenger is 0.01% - 20%;

[0027] Optionally, in the electrolyte for secondary batteries, the mass percentage of the oxygen radical scavenger is 0.1% - 10%;

[0028] Optionally, in the electrolyte for secondary batteries, the mass percentage of the oxygen radical scavenger is 2% - 5%.

[0029] By controlling the mass percentage of the oxygen radical scavenger within the above range, the electrolyte has good ability to capture oxygen-containing radicals, can significantly improve the gas generation problem of secondary batteries, and does not affect the capacity performance of secondary batteries.

[0030] In some of these embodiments, the electrolyte for secondary batteries includes an electrolyte salt, and the electrolyte salt is a lithium salt. By selecting a lithium salt as the electrolyte salt, the above electrolyte can be used to prepare secondary batteries such as lithium-ion batteries.

[0031] In some of these embodiments, the electrolyte for secondary batteries is an electrolytic solution, and the electrolytic solution further includes an organic solvent.

[0032] In a second aspect, the present application provides a secondary battery, including the above-mentioned electrolyte for secondary batteries. The secondary battery using the above electrolyte has good safety and stability.

[0033] In some of these embodiments, the secondary battery includes a positive electrode plate, and the positive electrode active material layer of the positive electrode plate contains a positive electrode active material and a positive electrode lithium supplement agent. The positive electrode lithium supplement agent can provide an excessive lithium source, make up for the consumption of lithium due to the formation of the SEI film on the positive electrode and the negative electrode, and improve the energy density, first-cycle Coulombic efficiency and cycling performance of the secondary battery.

[0034] In some of these embodiments, the positive electrode lithium supplement agent is selected from at least one of Li6CoO4, Li5FeO4, Li3VO4, Li2MoO3, Li2RuO3, Li2MnO3, Li2MnO2, Li2NiO2, Li2CuO2, Li2Cu x Ni 1-x M y O2, where 0 < x < 1, 0 ≤ y < 0.1, and M is selected from at least one of Zn, Sn, Mg, Fe, and Mn.

[0035] In some of these embodiments, the mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 0.1% to 10%;

[0036] Optionally, the mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 1% to 8%;

[0037] Optionally, the mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 1% to 5%.

[0038] The positive electrode lithium supplement agent within the above mass range percentage can supplement a sufficient lithium source, improve the energy density, first-cycle Coulombic efficiency and cycling performance of the secondary battery.

[0039] In some of these embodiments, the ratio of Dv50 of the positive electrode lithium supplement agent to Dv50 of the positive electrode active material is 1 to 10;

[0040] Optionally, the ratio of Dv50 of the positive electrode lithium supplement agent to Dv50 of the positive electrode active material is 2 to 8. Controlling the ratio of Dv50 of the positive electrode lithium supplement agent to Dv50 of the positive electrode active material within the above range, the positive electrode plate has appropriate ion conduction performance, fewer side reactions, and better capacity performance of the secondary battery.

[0041] In some of these embodiments, the molar ratio of the oxygen radical scavenger to the positive electrode lithium supplement agent is (0.02 to 20):1;

[0042] Optionally, the molar ratio of the oxygen radical scavenger to the positive electrode lithium supplement agent is (1 to 10):1;

[0043] Optionally, the molar ratio of the oxygen radical scavenger to the positive electrode lithium supplement agent is (3 to 10):1.

[0044] By controlling the molar ratio of the oxygen free radical scavenger to the cathode lithium supplement within the above range, the oxygen generation from side reactions of the secondary battery can be effectively reduced, and the specific capacity of the secondary battery can be prevented from decreasing.

[0045] In a third aspect, the present application provides a battery module including the above secondary battery.

[0046] In a fourth aspect, the present application provides a battery pack including the above battery module.

[0047] In a fifth aspect, the present application provides an electrical device including at least one selected from the above secondary battery, the above battery module, and the above battery pack.

[0048] The above description is only an overview of the technical solutions of the present application. In order to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present application more obvious and understandable, the following specifically describes the embodiments of the present application. Description of the Drawings

[0049] By reading the following detailed description of the optional embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the optional embodiments and are not considered as a limitation of the present application. And in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0050] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0051] Figure 2 is Figure 1 an exploded view of the secondary battery according to an embodiment of the present application shown in ;

[0052] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0053] Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0054] Figure 5 is Figure 4 an exploded view of the battery pack according to an embodiment of the present application shown in ;

[0055] Figure 6 is a schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source;

[0056] Description of the Reference Numerals:

[0057] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Cover plate. Detailed implementation manner

[0058] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure content of the present application more thorough and comprehensive.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0060] Unless otherwise stated or there is a contradiction, the terms or phrases used herein have the following meanings:

[0061] As used herein, the term "alkyl" refers to a monovalent residue formed by removing one hydrogen atom from a saturated hydrocarbon containing primary (normal) carbon atoms, or secondary carbon atoms, or tertiary carbon atoms, or quaternary carbon atoms, or a combination thereof. A phrase containing this term, for example, "C1-9 alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, which may independently be a C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl or C9 alkyl each time it appears. Suitable examples include, but are not limited to: methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(CH3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (-CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH(CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3) and octyl (-(CH2)7CH3).

[0062] The term "cycloalkyl" refers to a non-aromatic hydrocarbon containing cyclic carbon atoms, which can be a monocyclic alkyl group, a spirocyclic alkyl group, or a bridged cyclic alkyl group. A phrase containing this term, for example, "C3-C9 cycloalkyl" refers to a cycloalkyl group containing 3 to 9 carbon atoms, and each occurrence can independently be a C3 cycloalkyl group, a C4 cycloalkyl group, a C5 cycloalkyl group, a C6 cycloalkyl group, a C7 cycloalkyl group, a C8 cycloalkyl group, or a C9 cycloalkyl group. Suitable examples include, but are not limited to: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl. Additionally, "cycloalkyl" can also contain one or more double bonds, and representative examples of cycloalkyl groups containing double bonds include cyclopentenyl, cyclohexenyl, cyclohexadienyl, and cyclobutadienyl.

[0063] In this article, the term "heteroaryl" refers to an aryl group in which at least one carbon atom is replaced by a non-carbon atom, and the non-carbon atom can be an N atom, an O atom, an S atom, etc. For example, "C3-C 10 heteroaryl" refers to a heteroaryl group containing 3 to 10 carbon atoms, and each occurrence can independently be a C3 heteroaryl group, a C4 heteroaryl group, a C5 heteroaryl group, a C6 heteroaryl group, a C7 heteroaryl group, a C8 heteroaryl group, a C9 heteroaryl group, or a C10 heteroaryl group. Suitable examples include, but are not limited to: furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetrazole, indole, carbazole, pyrroloimidazole, pyrrolopyrrole, thiophenopyrrole, thiophenothiophene, furanopyrrole, furanofuran, thiophenofuran, benzisoxazole, benzisothiazole, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, phthalazine, quinoxaline, phenanthridine, peridine, quinazoline, and quinazolinone.

[0064] "Amino" refers to the residue formed by an amine losing at least one hydrogen atom, and it can be a primary amino group, a secondary amino group, or a tertiary amino group. Taking a monovalent amino group as an example, it has the structural feature of the formula -N(X)2, where each "X" is independently H, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted heterocyclic group, etc. Non-limiting types of amino groups include -NH2, -N(alkyl)2, -NH(alkyl), -N(cycloalkyl)2, -NH(cycloalkyl), -N(heterocyclic group)2, -NH(heterocyclic group), -N(aryl)2, -NH(aryl), -N(alkyl)(aryl), -N(alkyl)(heterocyclic group), -N(cycloalkyl)(heterocyclic group), -N(aryl)(heteroaryl), -N(alkyl)(heteroaryl), etc.

[0065] "Halogen" or "halo group" refers to F, Cl, Br, or I.

[0066] During the charge and discharge process of secondary batteries such as lithium-ion batteries, the active material on the positive electrode plate is prone to side reactions to generate gas at the interface between the electrode plate and the electrolyte, especially the problem of oxygen generation. The oxygen generated by the side reaction is likely to react with the electrolyte, affecting the safety performance and cycle stability of the secondary battery, and posing a great threat to the normal use of the secondary battery.

[0067] In addition, during the first charge and discharge process of the secondary battery, an SEI film will be formed on the surface of the electrode plate. The formation of the SEI film consumes the lithium source in the secondary battery, resulting in a decrease in the capacity of the secondary battery. Therefore, an excessive lithium source is usually provided by adding a positive electrode lithium supplement agent to the secondary battery to ensure the capacity of the secondary battery. However, the release of lithium ions from the positive electrode lithium supplement agent is usually accompanied by a side reaction of oxygen generation, which also affects the safety and cycle stability of the secondary battery.

[0068] To improve the above problems, the present application provides an electrolyte for a secondary battery, a secondary battery using the electrolyte, a battery module, a battery pack, and an electrical device. Such secondary batteries are applicable to various electrical devices using batteries, such as mobile phones, portable devices, laptop computers, battery cars, electric toys, electric tools, electric vehicles, ships, and spacecrafts. For example, spacecrafts include airplanes, rockets, space shuttles, and spaceships, etc.

[0069] An embodiment of the present application provides an electrolyte for a secondary battery, including an electrolyte salt and an oxygen free radical scavenger.

[0070] The above electrolyte includes an oxygen free radical scavenger, which can capture the oxygen-containing free radicals generated by side reactions in the secondary battery and suppress the generation of oxygen, thereby improving the safety and stability of the secondary battery.

[0071] In some of these embodiments, the oxygen free radical scavenger is an organic nitrogen oxide. Organic nitrogen oxides have high reactivity with oxygen-containing free radicals and can effectively improve the problem of gas generation from side reactions in the above electrolyte for secondary batteries.

[0072] In some of these embodiments, the oxygen free radical scavenger includes at least one of the compounds represented by Formula I, Formula II, and Formula III:

[0073]

[0074] Among them, R1 is selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted phenyl, heteroaryl, and ester groups; R2 is selected from one of substituted or unsubstituted alkyl and substituted or unsubstituted phenyl; R3 is selected from one of H and substituted or unsubstituted alkyl.

[0075] R4 is selected from one of H, aldehyde group, cyano group, substituted or unsubstituted alkyl group, and substituted or unsubstituted phenyl group; R5 is selected from one of substituted or unsubstituted alkyl group, ester group, phosphonic acid group, amide group, vinyl group, and substituted or unsubstituted phenyl group; R6 is selected from one of H and substituted or unsubstituted alkyl group;

[0076] R7 is selected from one of H, amino group, amide group, cyano group, isothiocyanato group, carboxyl group, ester group, hydroxyl group, and alkoxy group.

[0077] Furthermore, the oxygen radical scavenger includes at least one of the compounds shown in the above formula I and formula II. Compared with the compound shown in formula III, the compounds shown in formula I and formula II have higher oxygen free radical reaction activities.

[0078] In some embodiments, R1 is selected from one of substituted or unsubstituted C1-C6 alkyl group, substituted or unsubstituted phenyl group, C4-C5 heteroaryl group, and C2-C6 ester group; R2 is selected from one of substituted or unsubstituted C1-C6 alkyl group and substituted or unsubstituted phenyl group; R3 is selected from one of H and substituted or unsubstituted C1-C6 alkyl group;

[0079] R4 is selected from one of H, aldehyde group, cyano group, substituted or unsubstituted C1-C6 alkyl group, and substituted or unsubstituted phenyl group; R5 is selected from one of substituted or unsubstituted C1-C6 alkyl group, C2-C6 ester group, phosphonic acid group, amide group, vinyl group, and substituted or unsubstituted phenyl group; R6 is selected from one of H and substituted or unsubstituted C1-C6 alkyl group.

[0080] In some embodiments, R1 is selected from one of halogenated C1-C6 alkyl group, substituted or unsubstituted phenyl group, C4-C5 heteroaryl group, and C2-C6 ester group; R2 is selected from one of unsubstituted C1-C6 linear alkyl group, unsubstituted C3-C6 cyclic alkyl group, and substituted or unsubstituted phenyl group; R3 is selected from one of H and unsubstituted C1-C6 alkyl group;

[0081] R4 is selected from one of H, aldehyde group, cyano group, unsubstituted C1-C6 alkyl group, and substituted or unsubstituted phenyl group; R5 is selected from one of unsubstituted C1-C6 alkyl group, C1-C6 ester group, phosphonic acid group, amide group, vinyl group, and unsubstituted phenyl group; R6 is selected from one of H and unsubstituted C1-C6 alkyl group.

[0082] In some embodiments, in formula I: R1 is selected from one of halogenated C1-C6 alkyl group, substituted or unsubstituted phenyl group, pyridyl group, pyridine-N-oxide group, and C2-C6 ester group, R2 is selected from unsubstituted C1-C6 alkyl group, and R3 is selected from one of H and methyl group; or, R1 is selected from one of substituted or unsubstituted phenyl group and C4-C5 heteroaryl group, R2 is selected from substituted or unsubstituted phenyl group, and R3 is H;

[0083] In some of these embodiments, in Formula II, R4 is H, R5 is selected from one of unsubstituted C1-C6 alkyl, C1-C6 ester group, phosphonic acid group, amide group, and unsubstituted phenyl, and R6 is selected from one of H and unsubstituted C1-C6 alkyl; or, R4 is selected from unsubstituted C1-C6 alkyl, R5 is selected from one of unsubstituted C1-C6 alkyl, vinyl, and unsubstituted phenyl, and R6 is selected from one of H and unsubstituted C1-C6 alkyl; or, R4 is selected from substituted or unsubstituted phenyl, R5 is selected from unsubstituted C1-C6 alkyl, and R6 is selected from unsubstituted C1-C6 alkyl.

[0084] In some of these embodiments, R1 is a phenyl substituted by the substituent R 11 substituted phenyl, and the substituent R 11 is selected from one of alkyl, halogen, alkoxy, nitro, and amino.

[0085] In some of these embodiments, R2 is a phenyl substituted by the substituent R 21 substituted phenyl, and the substituent R 21 is selected from one of alkyl and halogen.

[0086] In some of these embodiments, R4 is a substituted phenyl, and the substituent is halogen.

[0087] In some of these embodiments, the oxygen radical scavenger is selected from at least one of the compounds represented by the following structural formulas:

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] By using the oxygen radical scavenger having the above structure, the electrolyte has good oxygen radical reaction activity and can improve the safety and stability of the secondary battery.

[0094] In some of these embodiments, in the electrolyte for a secondary battery, the mass percentage of the oxygen radical scavenger is 0.01% to 20%. If the content of the oxygen radical scavenger is too low, the effect of inhibiting oxygen production is relatively poor; if the content of the oxygen radical scavenger is too high, side reactions occur with the electrode sheet, reducing the capacity of the secondary battery. By controlling the mass percentage of the oxygen radical scavenger within the above range, the electrolyte has a good ability to capture oxygen radicals, can significantly improve the gas generation problem of the secondary battery, and does not affect the capacity of the secondary battery. Optionally, in the electrolyte for a secondary battery, the mass percentage of the oxygen radical scavenger is 0.01%, 0.1%, 0.5%, 1%, 3%, 6%, 8%, 10%, 12%, 15%, 18% or 20%. Further, in the electrolyte for a secondary battery, the mass percentage of the oxygen radical scavenger is 0.1% to 10%. Still further, in the electrolyte, the mass percentage of the oxygen radical scavenger is 2% to 5%.

[0095] In some of these embodiments, the electrolyte salt is a lithium salt. By selecting a lithium salt as the electrolyte salt, the above electrolyte can be used to prepare secondary batteries such as lithium ion batteries. In some of these embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro(bis(oxalato))phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0096] In some of these embodiments, the concentration of the lithium salt is 0.8 mol / L to 1.5 mol / L.

[0097] The electrolyte for the secondary battery of the present application can be liquid, gel or all-solid state. In some of these embodiments, the electrolyte for the secondary battery is an electrolytic solution, and the electrolytic solution further includes an organic solvent.

[0098] In some of these embodiments, the organic solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0099] In some of these embodiments, the electrolyte may optionally further include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain battery performance, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0100] Another embodiment of the present application further provides a method for preparing an electrolyte for a secondary battery, comprising the following steps:

[0101] Mix an electrolyte salt and an oxygen radical scavenger.

[0102] The above method for preparing the electrolyte is simple in operation, low in cost, easy to achieve large-scale production, and the prepared electrolyte can effectively improve the gas generation problem of the secondary battery and enhance the safety and stability of the secondary battery.

[0103] In addition, the secondary battery, battery module, battery pack and electrical device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0104] In one embodiment of the present application, a secondary battery is provided.

[0105] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charging and discharging process of the battery, active ions are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows ions to pass through.

[0106] [Positive Electrode Plate]

[0107] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0108] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0109] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0110] In some of these embodiments, the positive electrode active material in the positive electrode active material layer may employ positive electrode active materials for batteries that are well-known in the art. By way of example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates having an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone, or two or more of them may be used in combination. Among them, examples of the lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (which may also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which may also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which may also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which may also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which may also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and their modified compounds, and at least one of the like. Examples of the lithium-containing phosphates having an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (which may also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon, and at least one of the like.

[0111] In some of these embodiments, a positive electrode lithium supplement is further included in the positive electrode active material layer of the positive electrode tab. The positive electrode lithium supplement can provide an excessive lithium source, make up for the consumption of lithium due to the formation of the SEI film on the positive electrode and the negative electrode, and improve the energy density, first-cycle Coulombic efficiency, and cycling performance of the secondary battery.

[0112] In some of these embodiments, the positive electrode lithium supplement is selected from at least one of Li6CoO4, Li5FeO4, Li3VO4, Li2MoO3, Li2RuO3, Li2MnO3, Li2MnO2, Li2NiO2, Li2CuO2, Li2Cu x Ni 1-x M y O2, where 0 < x < 1, 0 ≤ y < 0.1, and M is selected from at least one of Zn, Sn, Mg, Fe, and Mn.

[0113] In some of these embodiments, the mass percentage of the positive electrode lithium supplement in the positive electrode active material layer is 0.1% to 10%. The positive electrode lithium supplement within the above mass range percentage can supplement sufficient lithium sources and improve the energy density, first-cycle Coulombic efficiency, and cycling performance of the secondary battery. Optionally, the mass percentage of the positive electrode lithium supplement in the positive electrode active material layer is 0.1%, 0.5%, 1%, 2%, 4%, 5%, 6%, 8%, or 10%. Further, the mass percentage of the positive electrode lithium supplement in the positive electrode active material layer is 1% to 8%. Still further, the mass percentage of the positive electrode lithium supplement in the positive electrode active material layer is 1% to 5%.

[0114] In some of these embodiments, the ratio of the Dv50 of the positive electrode lithium supplement to the Dv50 of the positive electrode active material is 1 to 10. Dv50 represents the average particle size with a volume distribution of 50%. As an example, Dv50 can be conveniently measured by a laser particle size analyzer with reference to GB / T 19077-2016 Laser diffraction method for particle size distribution, such as the Mastersizer2000E type laser particle size analyzer of Malvern Instruments Limited, UK. Controlling the ratio of the Dv50 of the positive electrode lithium supplement to the Dv50 of the positive electrode active material within the above range, the positive electrode has suitable ion conduction performance, fewer side reactions, and better capacity performance of the secondary battery. Optionally, the ratio of the Dv50 of the positive electrode lithium supplement to the Dv50 of the positive electrode active material is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. Further, the ratio of the Dv50 of the positive electrode lithium supplement to the Dv50 of the positive electrode active material is 2 to 8.

[0115] In some of these embodiments, the molar ratio of the oxygen radical scavenger to the cathode lithium supplementing agent is (0.02 to 20):1. By controlling the molar ratio of the oxygen radical scavenger to the cathode lithium supplementing agent within the above range, the oxygen generation from side reactions of the secondary battery can be effectively reduced, and the specific capacity per gram of the secondary battery can be prevented from decreasing. It can be understood that, depending on the type of the cathode lithium supplementing agent, the amount of oxygen-containing free radicals generated therefrom is different, and thus the molar ratio of the oxygen radical scavenger to the cathode lithium supplementing agent can be adjusted accordingly. Optionally, the molar ratio of the oxygen radical scavenger to the cathode lithium supplementing agent is 0.02:1, 1:1, 2:1, 4:1, 5:1, 8:1, 10:1, 12:1, 15:1 or 20:1. Further, the molar ratio of the oxygen radical scavenger to the cathode lithium supplementing agent is (1 to 10):1. Still further, the molar ratio of the oxygen radical scavenger to the cathode lithium supplementing agent is (3 to 10):1.

[0116] In some of these embodiments, the cathode active material layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0117] In some of these embodiments, the cathode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] In some of these embodiments, the cathode electrode sheet can be prepared in the following manner: Dispersing the components for preparing the cathode electrode sheet, such as the cathode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a cathode slurry; coating the cathode slurry on the cathode current collector, and after processes such as drying and cold pressing, the cathode electrode sheet can be obtained.

[0119] [Negative electrode sheet]

[0120] The negative electrode sheet includes a negative current collector and a negative active material layer provided on at least one surface of the negative current collector, and the negative active material layer includes a negative active material.

[0121] As an example, the negative current collector has two surfaces opposite to each other in its own thickness direction, and the negative active material layer is provided on either or both of the two opposite surfaces of the negative current collector.

[0122] In some of these embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0123] In some of these embodiments, the negative electrode active material can be a negative electrode active material for batteries known in the art. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials can be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0124] In some of these embodiments, the negative electrode active material layer may also optionally include a binder. The binder can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0125] In some of these embodiments, the negative electrode active material layer may also optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some of these embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0127] In some of these embodiments, the negative electrode plate can be prepared by the following method: dispersing the above components for preparing the negative electrode plate, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0128] [Electrolyte]

[0129] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate, and the electrolyte for the secondary battery provided by the first aspect of the present application is adopted.

[0130] [Separator]

[0131] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0132] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0133] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator can be made into an electrode assembly by a winding process or a stacking process.

[0134] In some embodiments, the secondary battery may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0135] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, and as plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0136] The present application does not particularly limit the shape of the secondary battery, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 is a secondary battery 5 with a square structure as an example.

[0137] In some embodiments, referring to Figure 2 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of the electrode assemblies 52 included in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0138] In some of these embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries included in the battery module may be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0139] Figure 3 is a battery module 4 as an example. Referring to Figure 3 , in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0140] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0141] In some of these embodiments, the above battery module may be further assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0142] Figure 4 and Figure 5 is a battery pack 1 as an example. Referring to Figure 4 and Figure 5 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0143] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but is not limited thereto.

[0144] As the electrical device, the secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0145] Figure 6 is an electrical device as an example. The electrical device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or battery module can be adopted.

[0146] Another example of the device can be a mobile phone, a tablet computer, a laptop computer, etc. The device usually requires being thin and light, and a secondary battery can be used as the power source.

[0147] Embodiment

[0148] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation of the present application. For those techniques or conditions not specified in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0149] In the specific implementation manner of the present application, the type of the electrolyte is an electrolytic solution, and the electrolytic solution contains an oxygen free radical scavenger with the following structural formula respectively.

[0150] Table 1 Structures of oxygen free radical scavengers

[0151]

[0152]

[0153]

[0154] Embodiment 1:

[0155] (1) Preparation of the positive electrode sheet: The positive electrode active material lithium iron phosphate (Dv50 = 1.4 μm), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are dissolved in the solvent N-methylpyrrolidone (NMP) according to a mass ratio of 97:2:1, and after being fully stirred and mixed evenly, a positive electrode paste is obtained; then the positive electrode paste is evenly coated on the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0156] (2) Preparation of the negative electrode sheet: The negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water as the solvent and uniformly mixed with deionized water as the solvent to prepare a negative electrode paste; then the negative electrode paste is evenly coated on the negative electrode current collector copper foil, and after drying, a negative electrode film is obtained, and then through cold pressing and slitting, a negative electrode sheet is obtained.

[0157] (3) Preparation of electrolyte: In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), several compounds 2-1 and LiPF6 were dissolved in an organic solvent (EC / DMC / EMC with a mass ratio of 1:1:1) in sequence, and stirred evenly to obtain an electrolyte containing 2wt% of compound 2-1 and 1mol / L LiPF6.

[0158] (4) Preparation of secondary batteries: stack the positive electrode sheet, separator (polypropylene film), and negative electrode sheet in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wind them to obtain an electrode assembly; place the electrode assembly in a battery case, dry it, inject the electrolyte, and then go through formation, standing, and other processes to obtain a secondary battery.

[0159] Embodiment 2:

[0160] (1) Preparation of positive electrode sheet: The positive electrode active material lithium iron phosphate (Dv50 = 1.4 μm), the positive electrode replenisher (Dv50 = 6 μm), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of (97-W1): W1: 2: 1, and the positive electrode slurry is obtained after being fully stirred and mixed; the positive electrode slurry is then evenly coated on the positive electrode current collector, and then dried, cold pressed, and cut to obtain a positive electrode sheet. Wherein W1 is the mass percentage of the positive electrode replenisher in the positive electrode active material layer.

[0161] (2) Preparation of negative electrode sheet: same as step (2) in Example 1.

[0162] (3) Preparation of electrolyte: In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), several compounds 1-1 and LiPF6 were dissolved in an organic solvent (EC / DMC / EMC=1 / 1 / 1) in turn and stirred evenly to obtain an electrolyte containing 2wt% of compound 1-1 and 1mol / L LiPF6.

[0163] (4) Preparation of secondary batteries: stack the positive electrode sheet, separator (polypropylene film), and negative electrode sheet in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wind them to obtain an electrode assembly; place the electrode assembly in a battery case, dry it, inject the electrolyte, and then go through formation, standing, and other processes to obtain a secondary battery.

[0164] Embodiments 3 to 22:

[0165] The secondary battery of this embodiment is different from that of Embodiment 2 in that the structure of the oxygen free radical scavenger in step (3) is different.

[0166] Embodiment 12:

[0167] (1) Preparation of the positive electrode sheet: The positive active material lithium iron phosphate (Dv50 = 1.4 μm), the positive lithium supplement agent (Dv50 = 6 μm), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black are dissolved in the solvent N-methylpyrrolidone (NMP) in a mass ratio of (97 - W1):W1:2:1, and stirred and mixed evenly to obtain the positive electrode slurry; then the positive electrode slurry is evenly coated on the positive current collector, and then dried, cold-pressed, and slit to obtain the positive electrode sheet. Where W1 is the mass percentage of the positive lithium supplement agent in the positive active material layer.

[0168] (2) Preparation of the negative electrode sheet: The same as step (2) of Example 1.

[0169] (3) Preparation of the electrolyte: In a glove box under an argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm), several compounds 2-1 and LiPF6 are successively dissolved in an organic solvent (EC / DMC / EMC with a mass ratio of 1:1:1), and stirred evenly to obtain an electrolyte containing 2 wt% of compound 2-1 and 1 mol / L of LiPF6.

[0170] (4) Preparation of the secondary battery: The positive electrode sheet, the separator (polypropylene film), and the negative electrode sheet are stacked in sequence, with the separator placed between the positive and negative electrode sheets to play a role in isolation, and then wound to obtain the electrode assembly; the electrode assembly is placed in the battery case, dried, injected with the electrolyte, and then processed through processes such as formation and standing to obtain the secondary battery.

[0171] Comparative Example 1:

[0172] The difference between the secondary battery of Comparative Example 1 and that of Example 1 is that in step (3), the electrolyte does not contain an oxygen radical scavenger.

[0173] Comparative Example 2:

[0174] The difference between the secondary battery of Comparative Example 2 and that of Example 2 is that in step (3), the electrolyte does not contain an oxygen radical scavenger.

[0175] The preparation parameters of the secondary batteries of Examples 1 to 22 and Comparative Examples 1 to 2 are shown in Table 2 specifically.

[0176] Table 2 Preparation parameters of the secondary batteries of Examples 1 to 22 and Comparative Examples 1 to 2

[0177]

[0178]

[0179] Examples 23 to 27:

[0180] Examples 23 to 27 are different from Example 12 in that the proportion of the positive electrode lithium supplement in the positive electrode active material layer in step (1) is different.

[0181] Examples 28 to 34:

[0182] Examples 28 to 34 are different from Example 12 in that the proportion of Compound 2-1 in the electrolyte in step (3) is different.

[0183] For the preparation parameters of the secondary batteries of Examples 23 to 34, see Table 3.

[0184] Table 3 Preparation parameters of the secondary batteries of Examples 12, 23 to 34

[0185]

[0186]

[0187] Examples 35 to 38:

[0188] Examples 35 to 38 are different from Example 12 in that different types of positive electrode lithium supplements are used in step (1). For the preparation parameters of the secondary batteries of Examples 35 to 38, see Table 4 specifically.

[0189] Table 4 Preparation parameters of the secondary batteries of Examples 35 to 38

[0190]

[0191] Examples 39 to 43:

[0192] Examples 39 to 43 are different from Example 12 in that the Dv50 of the positive electrode lithium supplement in step (1) is different. For the preparation parameters of the secondary batteries of Examples 39 to 43, see Table 5 specifically.

[0193] Table 5 Preparation parameters of the secondary batteries of Examples 12, 39 to 43

[0194]

[0195] Test part:

[0196] Secondary battery capacity test:

[0197] At 25 °C, the secondary battery is charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V until the current is less than 0.05C, and then the lithium-ion battery is discharged at a constant current of 0.33C to 2.5V, and its actual capacity C0 (mAh) is recorded. The specific capacity of the secondary battery is C0 / W3 (mAh / g), where W3 is the total mass (g) of the positive electrode active material and the positive electrode lithium supplement.

[0198] Gas composition test:

[0199] The secondary battery is charged on a formation gas generation instrument, and the process settings are as follows: at 45 °C, the secondary battery is charged at a constant current of 0.1C for 7 minutes, then left standing for 1 minute, then the lithium-ion battery is charged at a constant current of 0.33C until 3.65V, after standing for 1 minute, the battery is charged at a constant current of 0.1C until 4.5V, and then charged at a constant voltage of 4.5V until the current is less than 0.05C to obtain the data of the total gas production, and the gas composition is tested by GC-MS.

[0200] Table 6 Performance test results of secondary batteries of Examples 1 to 43 and Comparative Examples 1 to 2

[0201]

[0202] From the relevant data in Table 6, it can be seen that compared with the secondary battery of Comparative Example 1, in the secondary battery of Example 1, the electrolyte added Compound 2-1 as an oxygen free radical scavenger, and while ensuring the rated capacity of the secondary battery, the oxygen production of the secondary battery was significantly reduced.

[0203] Compared with Comparative Example 1, the positive electrode sheet of the secondary battery of Comparative Example 2 also added a positive electrode lithium supplement LiCu 0.6 Ni 0.4 O2, the specific capacity of the secondary battery increased, but the oxygen production of the secondary battery also increased. Compared with the secondary battery of Comparative Example 2, in the secondary batteries of Examples 2 to 22, the electrolyte added the oxygen free radical scavengers shown in Table 1, the specific capacity of the secondary battery remained basically unchanged, while the oxygen content in the gas decreased from 51.3 wt% to 4.8 wt% - 29.5%, and the oxygen production of the secondary battery decreased significantly.

[0204] In the secondary batteries of Examples 23 to 27, as the mass content of the positive electrode lithium supplement in the positive electrode active material layer increased, the specific capacity of the secondary battery increased, and the oxygen production also increased.

[0205] In the secondary batteries of Examples 28 to 34, the content of Compound 2-1 in the electrolyte was 0.01 wt% - 20 wt%. As the content of the oxygen free radical scavenger increased, the oxygen production of the secondary battery decreased. However, the increase in the content of the oxygen free radical scavenger also had a certain impact on the specific capacity of the secondary battery. Controlling the mass content of the oxygen free radical scavenger at 0.1% - 10%, or 2% - 5% can achieve a better oxygen production inhibition effect while ensuring a relatively high specific capacity of the secondary battery.

[0206] In the secondary batteries of Examples 35 to 38, different types of positive electrode lithium supplements were used respectively, in combination with the electrolyte in the secondary battery, the oxygen production of the secondary battery was less, and the specific capacity was relatively high.

[0207] In the secondary batteries of Examples 39 to 43, the ratio of the positive electrode lithium supplement Dv50 to the positive electrode active material Dv50 is different. It can be seen from the performance of the secondary batteries of Examples 39 to 43 that the ratio of the positive electrode lithium supplement Dv50 to the positive electrode active material Dv50 has a certain influence on the specific capacity of the secondary battery. In Examples 40 to 42, the ratio of the positive electrode lithium supplement Dv50 to the positive electrode active material Dv50 is 2 to 8, and the specific capacity of the secondary battery is slightly increased compared with Examples 39 and 43.

[0208] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0209] The above-described embodiments only represent several implementation manners of the present application, which are convenient for understanding the technical solutions of the present application specifically and in detail, but should not be construed as a limitation on the protection scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided in the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the content of the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. An electrolyte for a secondary battery, characterized in that, Comprising an oxygen free radical scavenger, the oxygen free radical scavenger comprising at least one of the compounds represented by Formula I, Formula II, and Formula III: Wherein, R1 is selected from one of substituted or unsubstituted alkyl, substituted or unsubstituted phenyl, heteroaryl, and ester group; R2 is selected from one of substituted or unsubstituted alkyl and substituted or unsubstituted phenyl; R3 is selected from one of H and substituted or unsubstituted alkyl; R4 is selected from one of H, aldehyde group, cyano group, substituted or unsubstituted alkyl, and substituted or unsubstituted phenyl; R5 is selected from one of substituted or unsubstituted alkyl, ester group, phosphonic acid group, amide group, vinyl, and substituted or unsubstituted phenyl; R6 is selected from one of H and substituted or unsubstituted alkyl; R7 is selected from one of amino group, amide group, cyano group, isothiocyanato group, carboxyl group, ester group, hydroxyl group, and alkoxy group.

2. The electrolyte for a secondary battery according to claim 1, wherein The R1 is selected from one of halogenated C1-C6 alkyl, substituted or unsubstituted phenyl, C4-C5 heteroaryl, and C2-C6 ester group; the R2 is selected from one of unsubstituted C1-C6 linear alkyl, unsubstituted C3-C6 cyclic alkyl, and substituted or unsubstituted phenyl; the R3 is selected from one of H and unsubstituted C1-C6 alkyl; The R4 is selected from one of H, aldehyde group, cyano group, unsubstituted C1-C6 alkyl, and substituted or unsubstituted phenyl; the R5 is selected from one of unsubstituted C1-C6 alkyl, C1-C6 ester group, phosphonic acid group, amide group, vinyl, and unsubstituted phenyl; the R6 is selected from one of H and unsubstituted C1-C6 alkyl.

3. The electrolyte for a secondary battery according to claim 2, characterized in that, In the Formula I: The R1 is selected from one of halogenated C1-C6 alkyl, substituted or unsubstituted phenyl, pyridyl, pyridine N-oxide group, and C2-C6 ester group, the R2 is selected from unsubstituted C1-C6 alkyl, and the R3 is selected from one of H and methyl; or, the R1 is selected from one of substituted or unsubstituted phenyl and C4-C5 heteroaryl, the R2 is selected from substituted or unsubstituted phenyl, and the R3 is H; And / or, in the Formula II, the R4 is H, the R5 is selected from one of unsubstituted C1-C6 alkyl, C1-C6 ester group, phosphonic acid group, amide group, and unsubstituted phenyl, and the R6 is selected from one of H and unsubstituted C1-C6 alkyl; or, the R4 is selected from unsubstituted C1-C6 alkyl, the R5 is selected from one of unsubstituted C1-C6 alkyl, vinyl, and unsubstituted phenyl, and the R6 is selected from one of H and unsubstituted C1-C6 alkyl; or, the R4 is selected from substituted or unsubstituted phenyl, the R5 is selected from unsubstituted C1-C6 alkyl, and the R6 is selected from unsubstituted C1-C6 alkyl.

4. The electrolyte for a secondary battery according to claim 1, characterized in that, The R1 is a phenyl group substituted by a substituent R 11 The substituent R 11 is selected from one of alkyl, halogen, alkoxy, nitro and amino; And / or, said R2 is a substituent R 21 Substituted phenyl, said substituent R 21 Selected from one of alkyl and halogen; And / or, the R4 is a substituted phenyl, and the substituent is a halogen.

5. The electrolyte for a secondary battery according to claim 1, wherein The oxygen free radical scavenger is selected from at least one of the compounds represented by the following structural formulas:

6. The electrolyte for a secondary battery according to any one of claims 1 to 5, characterized in that, In the electrolyte for the secondary battery, the mass percentage of the oxygen free radical scavenger is 0.01% to 20%.

7. The electrolyte for a secondary battery according to claim 6, wherein In the electrolyte for the secondary battery, the mass percentage of the oxygen free radical scavenger is 0.1% to 10%.

8. The electrolyte for a secondary battery according to claim 7, wherein In the electrolyte for the secondary battery, the mass percentage of the oxygen free radical scavenger is 2% to 5%.

9. The electrolyte for a secondary battery according to any one of claims 1 to 5, characterized in that, The electrolyte for the secondary battery includes an electrolyte salt, and the electrolyte salt is a lithium salt; and / or, the electrolyte for the secondary battery is an electrolytic solution, and the electrolytic solution further includes an organic solvent.

10. A secondary battery, characterized in that, It includes the electrolyte for the secondary battery according to any one of claims 1 to 9.

11. The secondary battery according to claim 10, characterized in that, The secondary battery includes a positive electrode plate, and the positive electrode active material layer of the positive electrode plate contains a positive electrode active material and a positive electrode lithium supplement agent.

12. The secondary battery according to claim 11, wherein The positive electrode lithium supplement is selected from at least one of Li6CoO4, Li5FeO4, Li3VO4, Li2MoO3, Li2RuO3, Li2MnO3, Li2MnO2, Li2NiO2, Li2CuO2, Li2Cu x Ni 1-x M y O2, where 0 < x < 1, 0 ≤ y < 0.1, and M is selected from at least one of Zn, Sn, Mg, Fe, and Mn.

13. The secondary battery according to claim 11 or 12, characterized in that, The mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 0.1% to 10%.

14. The secondary battery according to claim 13, characterized in that, The mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 1% to 8%.

15. The secondary battery according to claim 14, wherein The mass percentage of the positive electrode lithium supplement agent in the positive electrode active material layer is 1% to 5%.

16. The secondary battery according to claim 11 or 12, characterized in that, The ratio of the Dv50 of the positive electrode lithium supplement agent to the Dv50 of the positive electrode active material is 1 to 10.

17. The secondary battery according to claim 16, wherein The ratio of the Dv50 of the positive electrode lithium supplement agent to the Dv50 of the positive electrode active material is 2 to 8.

18. The secondary battery according to claim 11 or 12, characterized in that, The molar ratio of the oxygen free radical scavenger to the positive electrode lithium supplement agent is (0.02 to 20):

1.

19. The secondary battery according to claim 18, wherein The molar ratio of the oxygen free radical scavenger to the positive electrode lithium supplement agent is (1 to 10):

1.

20. The secondary battery according to claim 19, wherein, The molar ratio of the oxygen free radical scavenger to the positive electrode lithium supplement agent is (3 to 10):

1.

21. A battery module, characterized in that, It includes the secondary battery according to any one of claims 10 to 20.

22. A battery pack, characterized in that, It includes the battery module according to claim 21.

23. An electrical device, characterized in that, It includes at least one selected from the secondary battery according to any one of claims 10 to 20, the battery module according to claim 21, and the battery pack according to claim 22.

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