Electrolyte, secondary battery, and electric device

Abstract

The application discloses an electrolyte, a secondary battery and a power utilization device, wherein the electrolyte comprises a lithium salt, an organic solvent and an additive, and the additive comprises a compound shown in formula I: wherein R1, R2 and R3 are independently selected from hydrogen, C 1～10 alkyl, C 1～10 halogenated alkyl, phenyl, C 1～10 alkenyl, C 1～10 alkynyl or halogen. The application adds the compound shown in formula I into the electrolyte, so that the defects of strong oxidizability, poor structural order, poor material conductivity, poor kinetic performance, easy Li + / Ni 2+ mixing arrangement to form rock salt phase change and the like in a material bulk phase of a low-cobalt ternary positive electrode material with low cobalt content are improved, and the battery performance is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to an electrolyte, a secondary battery and an electric device. BACKGROUND

[0002] At present, secondary batteries have been widely used in technical products such as automobiles and mobile phones. However, in recent years, as the requirement for high performance of electronic devices is getting higher and higher, the requirement for high capacity, high output, high temperature storage characteristics and cycle characteristics of the secondary batteries applied is also getting higher and higher.

[0003] The pursuit of high specific energy density is an important research and development direction of secondary batteries today, and accelerating the development of high-energy and high-safety performance ternary materials is the trend of the times. The Co element in ternary materials accounts for a large proportion of the cost, and the high cost hinders people's pace of promoting green and low-carbon travel. At present, by reducing the content of Co element in ternary positive electrode material, the manufacturing cost of secondary battery can be effectively reduced, but problems such as too much increase of battery dynamics impedance and too fast capacity attenuation during use of electric vehicles are also caused.

[0004] Therefore, it is necessary to develop a new electrolyte which can improve the battery dynamics performance. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the first aspect of the present application provides an electrolyte which can effectively improve the battery dynamics performance.

[0006] The second aspect of the present application further provides a secondary battery.

[0007] The third aspect of the present application provides an electric device.

[0008] The electrolyte according to the first aspect of the present application comprises a lithium salt, an organic solvent and an additive, and the additive comprises a compound represented by Formula I:

[0009]

[0010] wherein R1, R2 and R3 are independently selected from hydrogen, C1-6alkyl, C1-6haloalkyl, phenyl, C1-6alkenyl, C1-6alkynyl or halogen. 1～10 1～10 1～10 1～10

[0011] The electrolyte according to the embodiments of the present application has at least the following beneficial effects:

[0012] ​​​​The application adds a compound shown in formula I into an electrolyte, which has an unsaturated conjugated double bond with nitrogen asymmetry and a benzene ring conjugated delocalized pi bond, has a higher HOMO energy level and a lower LUMO energy level, is prone to electrochemical reaction on the surface of a positive electrode and a negative electrode to form a uniform and dense stable passivation protective film rich in electrons during charging and discharging of a lithium ion battery, and has a certain steric hindrance effect due to introduction of an alkyl aromatic functional group and the like side chain, so that the density of the passivation protective film can be controlled, the lithium ion conductivity can be effectively improved, and the high active sites on the surface of a low-cobalt (Co%≤20%) ternary positive electrode material can be further covered, so that the strong oxidation, poor structural order, instability, poor conductivity, poor kinetics, and Li + / Ni 2+ Mixing to form rock salt phase change and the like defects.

[0013] According to some embodiments of the application, the halogen refers to at least one of fluorine, chlorine, bromine and iodine.

[0014] According to some embodiments of the application, R1, R2 and R3 are independently selected from hydrogen, C 1～5 haloalkyl, C 1～5 alkenyl.

[0015] According to some embodiments of the application, the compound shown in formula I includes one of the following:

[0016]

[0017] According to some embodiments of the application, the additive further includes a compound shown in formula II:

[0018]

[0019] The A is B, P or Al.

[0020] The compound shown in formula II in the application and the compound shown in formula I also have a synergistic effect, which greatly reduces the DCR growth during battery cycling, and further reduces the polarization during battery charging and discharging.

[0021] According to some embodiments of the application, the compound shown in formula II includes one of the following:

[0022]

[0023] According to some embodiments of the present invention, the compound represented by Formula I has a mass percentage content of 0.01% to 10% in the electrolyte, calculated based on the total mass of the electrolyte. For example, it may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 5%, 7%, 10%, or a range consisting of two of these values.

[0024] According to some embodiments of the present invention, the compound represented by Formula I has a mass percentage content of 0.1% to 3% in the electrolyte, calculated based on the total mass of the electrolyte.

[0025] When the content of the compound shown in Formula I is less than 0.1%, its concentration is too low to effectively polymerize and form a uniform and dense passivation film on the cathode. It cannot effectively cover the active sites on the surface of the low-cobalt ternary cathode material and cannot significantly improve the cycle life of the battery system. When its content is higher than 3%, the high concentration of the compound shown in Formula I has conjugated double bonds, which are prone to free radical polymerization reactions during the charging and discharging of lithium batteries. This results in a very thick and highly dense interfacial film formed at the cathode interface, which has an excessively strong interfacial effect on the cathode. As a result, the battery system has a large interfacial impedance and deteriorates the cycle kinetics performance of the low-cobalt system.

[0026] According to some embodiments of the present invention, the compound represented by Formula II has a mass percentage content of 0.01% to 7% in the electrolyte, calculated based on the total mass of the electrolyte. For example, it can be 0.01%, 0.1%, 0.5%, 1%, 3%, 5%, 7%, or a range consisting of two of these values.

[0027] According to some embodiments of the present invention, the compound represented by Formula II has a mass percentage content of 0.1% to 3% in the electrolyte, calculated based on the total mass of the electrolyte.

[0028] When the content of the compound shown in Formula II is less than 0.1%, the film-forming efficiency is insufficient and it cannot significantly improve the battery DCR performance. When its content is higher than 3%, the improvement of battery DCR after interfacial film formation is limited, and the increase in content leads to higher electrolyte cost.

[0029] According to some embodiments of the present invention, the mass percentage ratio of the compound represented by Formula I and the compound represented by Formula II in the electrolyte is 0.02 to 100. For example, it can be 0.02, 0.14, 0.20, 0.33, 2, 6, 10, 14, 20, 40, 60, 80, 100 or a range consisting of two of these values.

[0030] According to some embodiments of the present invention, the additive further includes at least one of vinyl sulfate (DTD), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), 1-propylene-1,3-sulfonate lactone (PST), methanedisulfonate methylene ester (MMDS), ethylene ethylene carbonate (VEC), tris(trimethylsilyl) phosphate (TMSP), and tris(trimethylsilyl) phosphite.

[0031] According to some embodiments of the present invention, the organic solvent may be selected from at least one of carbonates, carboxylic acid esters, sulfates, phosphates, amides, nitriles, and ethers. For example, ethylene carbonate (also known as ethylene carbonate), propylene carbonate (also known as propylene carbonate), dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, dimethyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, fluorinated cyclic organic esters, and sulfur-containing cyclic organic esters, or one or more of these. The organic solvent may have a mass percentage content of 60% to 80% in the electrolyte.

[0032] According to some embodiments of the present invention, the carbonate includes cyclic carbonates and chain carbonates.

[0033] According to some embodiments of the present invention, the cyclic carbonate includes at least one of ethylene carbonate (EC), fluoroethylene carbonate (FEC), and propylene carbonate (PC).

[0034] According to some embodiments of the present invention, the chain carbonate includes at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

[0035] According to some embodiments of the present invention, the lithium salt is selected from LiPF6, LiBF4, LiBOB (lithium difluorooxalatoborate), LiDFOB (lithium difluorooxalatoborate), LiAsF6, LiPO2F2, LiN(CF3SO2)2, LiCF3SO3, LiClO4, LiN(C x F 2x+1 SO2)(C y F 2y+1 One or more combinations of SO2, wherein LiN(C) x F 2x+1 SO2)(C y F 2y+1In the electrolyte (SO2), x and y are natural numbers. Considering the battery's energy density, power characteristics, and cycle life, LiPF6, LiN(SO2F)2, and LiBF4 are preferred. The lithium salt molar concentration in the electrolyte is 0.1–3 mol / L. Preferably, the lithium salt molar concentration is 0.3–2 mol / L. A higher lithium salt concentration makes it less prone to dissociation in the solvent system; a lower lithium salt concentration results in more dissociated Li... + It is produced in small quantities and has low electrical conductivity.

[0036] A second aspect of the present invention provides a secondary battery, comprising a negative electrode, a positive electrode, a separator, and the electrolyte described above.

[0037] According to some embodiments of the present invention, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0038] According to some embodiments of the present invention, the negative electrode sheet includes at least one negative electrode active material, wherein the Raman R value of the negative electrode active material is ≥0.1.

[0039] It should be noted that the Raman R value is 1360 cm⁻¹ in argon-ion laser Raman spectroscopy. -1 Peak intensity and 1580cm -1 The ratio of peak intensity.

[0040] According to some embodiments of the present invention, the negative electrode active material may 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 material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

[0041] According to some embodiments of the present invention, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0042] According to some embodiments of the present invention, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (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.).

[0043] According to some embodiments of the present invention, the negative electrode film layer may optionally include a binder. The binder may 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).

[0044] According to some embodiments of the present invention, the negative electrode film layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0045] According to some embodiments of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. For example, the positive current collector includes two opposing surfaces in its thickness direction, and the positive active material layer is stacked on either or both of the two surfaces of the positive current collector.

[0046] According to some embodiments of the present invention, the positive electrode sheet includes a positive electrode active material, and the general structural formula of the positive electrode active material includes LiaNixCoyMzO2, wherein 0.9≤a≤1.1, y≤0.2, x+y+z=1, and M includes one or both of Al and Mn.

[0047] According to some embodiments of the present invention, the positive electrode sheet includes a positive electrode active material, and the general structural formula of the positive electrode active material includes LiaNixCoyMzO2, wherein 0.9≤a≤1.1, 0.05≤y≤0.15, x+y+z=1, and M includes one or both of Al and Mn.

[0048] According to some embodiments of the present invention, the lithium metal battery of the present invention does not have any particular limitation on the separator, and any known porous structure separator with electrochemical stability and chemical stability can be selected, such as one or more single-layer or multi-layer films of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0049] A third aspect of the present invention provides an electrical device comprising the aforementioned secondary battery.

[0050] According to some embodiments of the present invention, the electrical equipment includes mobile phones, computers, wearable devices, power banks, electric vehicles, and energy storage devices, etc.

[0051] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Detailed Implementation

[0052] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0053] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0054] Example 1

[0055] Example 1 provides an electrolyte, the composition of which is shown in Table 1, and the preparation method is as follows:

[0056] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh organic solvent (ethylene carbonate, diethyl carbonate, methyl ethyl carbonate (mass ratio 4:3:3)) into a sample bottle. Add 12.5% ​​LiPF6 (1M) and 1% ethylene sulfate (DTD) of the total mass to the sample bottle, then add the compounds shown in Formula I and Formula II, and mix thoroughly to obtain the prepared electrolyte.

[0057] Examples 2-6

[0058] Examples 2-6 also provide a series of electrolytes, the component contents of which are shown in Table 1, and the preparation methods are as follows:

[0059] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh organic solvent (ethylene carbonate, diethyl carbonate, methyl ethyl carbonate (mass ratio 4:3:3)) into a sample bottle. Add 12.5% ​​LiPF6 (1M) and 1% ethylene sulfate (DTD) of the total mass to the sample bottle, then add the compounds shown in Formula I and Formula II, and mix thoroughly to obtain the prepared electrolyte.

[0060] Table 1 Component content of Examples 1-6

[0061]

[0062] Examples 7-11

[0063] Examples 7-11 also provide a series of electrolytes, the component contents of which are shown in Table 2, and the preparation methods are as follows:

[0064] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh organic solvent (ethylene carbonate, diethyl carbonate, methyl ethyl carbonate (mass ratio 4:3:3)) into a sample bottle. Add 12.5% ​​LiPF6 (1M) and 1% ethylene sulfate (DTD) of the total mass to the sample bottle, then add the compounds shown in Formula I and Formula II, and mix thoroughly to obtain the prepared electrolyte.

[0065] Table 2 Component content of Examples 7-11

[0066] Example 7 Example 8 Example 9 Example 10 Example 11 Compounds of formula la 1％ 1％ 1％ 1％ 1％ Compounds of formula Ila 0.01％ 0.1％ 3％ 5％ 7％ LiPF6 12.5％ 12.5％ 12.5％ 12.5％ 12.5％ Vinyl sulfate 1％ 1％ 1％ 1％ 1％ Organic solvent balance balance balance balance balance balance

[0067] Examples 12-17 and Comparative Examples 1-2

[0068] Examples 12-17 and Comparative Examples 1-2 also provide a series of electrolytes, the component contents of which are shown in Table 3, and the preparation methods are as follows:

[0069] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh organic solvent (ethylene carbonate, diethyl carbonate, methyl ethyl carbonate (mass ratio 4:3:3)) into a sample bottle. Add 12.5% ​​LiPF6 (1M) and 1% ethylene sulfate (DTD) of the total mass to the sample bottle, then add the compounds shown in Formula I and Formula II, and mix thoroughly to obtain the prepared electrolyte.

[0070] Table 3. Component content of Examples 12-17 and Comparative Examples 1-2

[0071]

[0072] Experimental Examples 1-17 and Control Experimental Examples 1-2

[0073] Experimental Examples 1-17 and Comparative Examples 1-2 provide a series of batteries, which are prepared by the following methods:

[0074] Preparation of positive electrode sheet:

[0075] LiNi, the positive electrode active material 0.65 Co 0.05 Mn 0.3 O2 (lithium nickel cobalt manganese) and conductive agent acetylene black (Super P) are mixed evenly in a mixing tank. Then, N-methylpyrrolidone (NMP) and binder polyvinylidene fluoride (PVDF) are added and stirred evenly to obtain a black slurry. This slurry is coated on aluminum foil, baked, rolled, and cut into sheets to obtain the positive electrode sheet. The mass ratio of the positive electrode active material, conductive agent, and binder is (96:3:1).

[0076] Negative electrode preparation:

[0077] The negative electrode active material graphite and the conductive agent acetylene black (Super P) are mixed evenly in a mixing tank. Then, the binder SBR and deionized water are added and stirred evenly to obtain a black slurry. This slurry is coated on copper foil, baked, rolled, and cut into sheets to obtain the negative electrode sheet. The ratio of active material, conductive agent and binder is (96:1:3).

[0078] Battery making:

[0079] The obtained positive electrode sheet, negative electrode sheet, and separator are stacked in the order of positive electrode, separator, and negative electrode. After winding, hot pressing and shaping, and electrode tab welding, a bare cell is obtained. The top and side are sealed with aluminum-plastic film. After the process, the battery is placed in an oven at 85±10℃ for 24h±12h to ensure that the water content of the electrode sheet is qualified. Then, the electrolyte of Examples 1 to 17 and Comparative Examples 1 to 2 is injected. After depressurization encapsulation, standing, formation, shaping and other processes, the batteries of Experimental Examples 1 to 17 and Comparative Examples 1 to 2 are obtained.

[0080] Experimental Example 18

[0081] Example 18 provides a battery prepared in the same manner and in the same amount as in Example 1, except that its positive electrode active material is LiNi. 0.63 Co 0.08 Mn 0.29 O2.

[0082] Experimental Example 19

[0083] Experimental Example 19 provides a battery whose preparation method and dosage are the same as those in Experimental Example 1, except that its positive electrode active material is LiNi. 0.63 Co 0.15 Mn 0.22 O2.

[0084] Performance testing

[0085] I. Loop Testing:

[0086] Room temperature cycling: The batteries of Experimental Examples 1-19 and Comparative Examples 1-2 were subjected to charge-discharge cycle tests at 25°C with a charge-discharge rate of 1C / 1C in the range of 2.8-4.35V. The initial discharge capacity and the discharge capacity after each cycle were recorded. The cycle was 1000 cycles. The capacity retention rate was calculated as (discharge capacity per cycle / initial discharge capacity of the battery) * 100%. The cycle termination condition was 80% SOC. The recorded data are shown in Table 4.

[0087] High-temperature cycling: The batteries of Experimental Examples 1-19 and Comparative Examples 1-2 were placed in a 45℃ chamber for 120 min, and then charged and discharged in a 45℃ constant temperature chamber at a charge / discharge rate of 1C / 1C within the range of 2.8-4.25V. The initial discharge capacity and the discharge capacity after each cycle were recorded. The cycle was 500 cycles. The capacity retention rate was calculated as (discharge capacity per cycle / initial discharge capacity of the battery) * 100%. The cycle termination condition was 80% SOC. The recorded data are shown in Table 4.

[0088] II. High-temperature storage:

[0089] The batteries from Experimental Examples 1-19 and Controlled Examples 1-2 were fully charged and stored in a 60°C constant temperature chamber. Every 10 days, they were removed, fully charged again, and stored in the 60°C constant temperature chamber for another 120 days. The recoverable capacity was then tested. The method for testing the recoverable capacity is as follows:

[0090] 1. Discharge at a constant current of 1C to 2.8V, then let stand for 10 minutes;

[0091] 2. Charge the 1C CC-CV to 4.25V, with a cutoff current of 0.05C, and let it stand for 10 minutes;

[0092] 3. Discharge at a constant current of 1C to 2.8V, and record the discharged capacity as the recoverable capacity.

[0093] High-temperature storage capacity retention rate = recoverable capacity after storage / recoverable capacity of fresh battery * 100%, and the recorded data is shown in Table 4.

[0094] III. Volume expansion experiment: The batteries of Experimental Examples 1-19 and Comparative Experimental Examples 1-2 were charged to 4.25V at 1C. The volume was measured by the water displacement method. The initial volume and the volume after 7 days of storage at 85℃ were recorded. The volume expansion rate = (volume after 7 days of storage at 85℃ - initial volume) / initial volume * 100%. The storage termination condition was 80% SOC. The results are shown in Table 4.

[0095] IV. DCR Test:

[0096] The batteries from Experimental Examples 1-19 and Controlled Examples 1-2 were charged to 4.25V at 1C CC-CV with a cutoff current of 0.05C, then discharged at 1C capacity for 30 minutes, and adjusted to 50% SOC.

[0097] Afterwards, the sample was placed at 25℃ for 2 hours, and then a pulse program was executed. The sample was discharged at a constant current of 5C for 10 seconds, and then allowed to stand for 10 minutes to complete the test. The DCR was calculated as (voltage before pulse discharge - voltage after pulse discharge) / discharge current * 100%. The recorded results are shown in Table 4.

[0098] Table 4. Data from Experimental Examples 1-18 and Comparative Experimental Examples 1-3

[0099]

[0100]

[0101] The data from Experimental Examples 1-19 and Comparative Examples 1-2 show that the compound shown in Formula I readily undergoes an electrochemical catalytic reaction on the cathode surface during the charging and discharging process of lithium-ion batteries to form a uniform and dense passivation protective film. Simultaneously, the introduction of side chains containing alkyl aromatic functional groups provides a certain steric hindrance effect, allowing for the control of the density of the formed passivation protective film, thus generating an effective protective film through the electrocatalytic reaction. Furthermore, the three-dimensional spatial structure of the alkyl aromatic side chains in the compound shown in Formula I forms a three-dimensional channel with lithium-ion conduction capabilities, significantly improving the cycle dynamics and storage performance of lithium batteries. The formed protective film further covers the highly active sites on the surface of the low-cobalt ternary cathode material, effectively isolating the highly oxidized cathode material from direct contact with the electrolyte, preventing violent electrolyte decomposition reactions, and further improving the battery's high-temperature storage and gas generation.

[0102] By comparing Experimental Examples 1-6 with Comparative Experiment 1, it was found that when Compound I was added, the volume expansion rate could be appropriately reduced and the cycle improved. However, when the content was too high, the cycle would be worsened and the DCR would be increased, and the volume expansion rate could not be further reduced. Therefore, an appropriate amount of Compound I has a more balanced overall performance.

[0103] As can be seen from Examples 1, 7-11 and 15, adding an appropriate amount of compound II can improve the cycle and reduce the DCR, but excessive amount of compound II will worsen the cycle.

[0104] The experimental results of Examples 12-14 show that other types of compounds represented by Formula I and Formula II also have the same synergistic effect of improving high-temperature storage and high-temperature gas production, as well as reducing impedance.

[0105] As can be seen from Comparative Experiment 1, when the compound shown in Formula I is not added, high-temperature gas production leads to a high volume expansion rate and a decrease in cycle performance.

[0106] As can be seen from Comparative Experiment 2, when the compounds shown in Formula I and Formula II are not added, the volume expansion rate, cycle performance and DCR performance are all poor.

[0107] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. An electrolyte, characterized in that, It includes lithium salts, organic solvents, and additives, wherein the additives include compounds represented by Formula I and compounds represented by Formula II: 、 Among them, R1, R2, and R3 are independently selected from hydrogen, C 1~10 alkyl, C 1~10 Halogenated alkyl, phenyl, C 1~10 alkenyl, C 1~10 alkynyl or halogen; Based on the total mass of the electrolyte, the compound represented by Formula I has a mass percentage content of 0.1% to 3% in the electrolyte; the compound represented by Formula II has a mass percentage content of 0.1% to 3% in the electrolyte.

2. The electrolyte according to claim 1, characterized in that, The compound represented by Formula I includes one of the following: 、 、 。 3. The electrolyte according to claim 1, characterized in that, The mass percentage ratio of the compound represented by Formula I to the compound represented by Formula II in the electrolyte is 0.02 to 100.

4. The electrolyte according to any one of claims 1 to 3, characterized in that, The additives also include at least one of vinyl sulfate, vinylene carbonate, 1,3-propanesulfonate lactone, 1-propylene-1,3-sulfonate lactone, methanedisulfonate, ethylene ethylene carbonate, tris(trimethylsilyl) phosphate, and tris(trimethylsilyl) phosphite.

5. A secondary battery, characterized in that, It includes a negative electrode, a positive electrode, a separator, and the electrolyte according to any one of claims 1 to 4.

6. The secondary battery according to claim 5, characterized in that, The positive electrode sheet includes a positive electrode active material, and the general structural formula of the positive electrode active material includes Li. a Ni x Co y M z O2, where 0.9≤a≤1.1, y≤0.2, x+y+z=1, and M includes one or both of Al and Mn.

7. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 5 or 6.

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