Electrolyte, secondary battery, and electric device

Abstract

The application discloses an electrolyte, a secondary battery and a power utilization device, and belongs to the battery field. The electrolyte comprises a first additive, and a chemical structural formula of the first additive comprises a heterocyclic ring and a thiourea group. The electrolyte disclosed by the application can improve the high-temperature storage performance, low-temperature discharge performance and cycle performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrolyte, a secondary battery, and an electrical device. Background Technology

[0002] Secondary batteries, especially lithium-ion batteries, are widely used in portable electronic devices, electric vehicles, and other fields due to their advantages such as high specific capacity, long cycle life, high operating voltage, small size, and no memory effect. However, with the continuous development of science and technology, people have also placed higher demands on the energy density of lithium-ion batteries.

[0003] Currently, the commonly used cathode materials for lithium-ion batteries are mainly ternary materials such as lithium iron phosphate and lithium nickel cobalt manganese oxide. Among them, lithium nickel cobalt manganese oxide ternary layered materials have high theoretical capacity, as well as advantages such as low cost and low toxicity. In particular, the high nickel content of ternary materials can further significantly improve the energy density of lithium-ion batteries and enhance the product's range. However, with the increase of nickel (Ni) content, the oxidizability of the cathode material surface also increases, causing the electrolyte to easily undergo oxidative decomposition and gas generation on the cathode surface. At the same time, during high-nickel cathode materials, the transition metals react chemically with the electrolyte during high-temperature storage and cycling, leading to the dissolution of excess metals and their deposition at the negative electrode interface, which also causes a decrease in the conductivity of the interface. This results in a significant deterioration in the battery's high-temperature storage performance, low-temperature discharge performance, and cycle performance. Summary of the Invention

[0004] The purpose of this application is to provide an electrolyte that can suppress the oxidation reaction of the electrolyte on the surface of the positive electrode, reduce the dissolution of transition metals, and thus solve the above-mentioned problems.

[0005] To achieve the above objectives, the present application adopts the following technical solution.

[0006] This application provides an electrolyte comprising a first additive, wherein the chemical structure of the first additive comprises a heterocyclic ring and a thiourea group.

[0007] Optionally, in some embodiments of this application, the chemical structural formula of the first additive includes the structure shown in Formula I:

[0008]

[0009] R1, R2, and R3 are each independently selected from at least one of hydrogen atoms, halogen atoms, alkyl groups having 1 to 7 carbon atoms, cycloalkyl groups having 3 to 5 carbon atoms, alkenyl groups having 2 to 5 carbon atoms, alkynyl groups having 2 to 5 carbon atoms, aryl groups having 6 to 10 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, and haloalkyl groups having 1 to 12 carbon atoms.

[0010] Optionally, in some embodiments of this application, the electrolyte further includes a second additive, the second additive comprising a cyclic phosphate ester compound, and the chemical structural formula of the second additive comprising the structure shown in Formula II:

[0011]

[0012] R4 is selected from S or O;

[0013] R5, R6, and R7 are each independently selected from at least one of cyano, hydrogen, nitro, halogen, alkyl having 1 to 5 carbon atoms, cycloalkyl having 3 to 6 carbon atoms, alkenyl having 2 to 6 carbon atoms, alkynyl having 2 to 6 carbon atoms, aryl having 6 to 10 carbon atoms, alkoxy having 1 to 7 carbon atoms, and haloalkyl having 1 to 12 carbon atoms.

[0014] Optionally, in some embodiments of this application, the first additive includes at least one of the following compounds:

[0015]

[0016] Optionally, in some embodiments of this application, the second additive includes at least one of the following compounds:

[0017]

[0018] Optionally, in some embodiments of this application, the first additive accounts for 0.1 wt% to 1 wt% of the mass percentage of the electrolyte.

[0019] Optionally, in some embodiments of this application, the second additive accounts for 0.2wt% to 2wt% of the mass percentage of the electrolyte, and the mass ratio of the first additive to the second additive is 1:(2 to 5).

[0020] Optionally, in some embodiments of this application, the electrolyte comprises a lithium salt. The lithium salt comprises lithium hexafluorophosphate and / or an auxiliary lithium salt. The auxiliary lithium salt comprises at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium difluorodi(oxalato)phosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0021] Optionally, in some embodiments of this application, the lithium hexafluorophosphate accounts for 12.0 wt% to 15.0 wt% of the electrolyte by mass. The auxiliary lithium salt accounts for 0.1 wt% to 1.0 wt% of the electrolyte by mass.

[0022] Optionally, in some embodiments of this application, the electrolyte comprises an organic solvent. The organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, acetonitrile, and sulfolane.

[0023] Correspondingly, this application also provides a secondary battery, including the electrolyte described above.

[0024] In addition, this application also provides an electrical device, including the above-mentioned secondary battery, wherein the secondary battery serves as the power supply for the electrical device.

[0025] The beneficial effects of this application are as follows:

[0026] The electrolyte provided in this application includes a first additive, the chemical formula of which includes heterocyclic rings and thiourea groups, significantly improving the battery's high-temperature storage performance, low-temperature discharge performance, and cycle performance. Specifically, the first additive can stabilize the positive electrode interface, inhibiting the interfacial reaction between the electrolyte and the positive electrode under high-temperature conditions. Simultaneously, the first additive can preferentially reduce at the negative electrode to form a low-resistance interfacial film, significantly improving the battery's cycle life and low-temperature performance. Furthermore, the electrolyte of this application also includes a second additive, which can further significantly improve the battery's high-temperature storage performance, low-temperature discharge performance, and cycle performance. Specifically, the second additive can form a stable interfacial film on the positive electrode surface, thereby improving the battery's cycle performance and high-temperature storage performance. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0028] It should be noted that the term "comprising" in this document means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of this application may exist in the form of a range; it should be understood that a description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that a range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range. The sizes and numerical values ​​disclosed herein should not be construed as strictly limited to the stated precise numerical values. Rather, unless otherwise specified, various sizes are intended to represent the referenced numerical values ​​and ranges functionally equivalent to the stated numerical values.

[0029] During the research process, the inventors of this application discovered that the commonly used electrolyte formulation design approach is mainly to alleviate the degradation of the cathode material by adding some additives with excellent film-forming properties. However, these additives usually increase the impedance of the cathode interface, resulting in poor low-temperature performance and rate performance.

[0030] Therefore, the inventors of this application have developed an electrolyte that can simultaneously take into account the cycling performance and high and low temperature performance of high-nickel ternary electrolytes.

[0031] This application provides an electrolyte comprising a first additive, the first additive having a chemical structure including heterocyclic rings and thiourea groups. In this embodiment, the thiourea groups in the first additive can stabilize the positive electrode interface and suppress the interfacial reaction between the electrolyte and the positive electrode under high-temperature conditions. The heterocyclic structure can stabilize the electrolyte, further improving the high-temperature stability of the electrolyte. Simultaneously, the first additive can preferentially reduce at the negative electrode to form a low-impedance interfacial film, which can significantly improve the cycle life and low-temperature performance of the battery.

[0032] In some embodiments, the chemical structural formula of the first additive includes the structure shown in Formula I:

[0033]

[0034] R1, R2, and R3 are each independently selected from at least one of the following: hydrogen atom, halogen atom, alkyl group having 1 to 7 carbon atoms, cycloalkyl group having 3 to 5 carbon atoms, alkenyl group having 2 to 5 carbon atoms, alkynyl group having 2 to 5 carbon atoms, aryl group having 6 to 10 carbon atoms, alkoxy group having 1 to 7 carbon atoms, and haloalkyl group having 1 to 12 carbon atoms. The first additive of this embodiment exhibits higher stability; its application in the electrolyte can effectively improve the high and low temperature stability of the electrolyte, thereby enhancing battery performance.

[0035] In some embodiments, the first additive comprises at least one of the following compounds:

[0036]

[0037] The materials described in this embodiment are widely available, the preparation process is mature, and they have a better effect on improving battery performance.

[0038] In some embodiments, the electrolyte further includes a second additive, the second additive comprising a cyclic phosphate ester compound, the chemical structure of the second additive comprising the structure shown in Formula II:

[0039]

[0040] R4 is selected from S or O;

[0041] R5, R6, and R7 are each independently selected from at least one of the following: cyano, hydrogen, nitro, halogen, alkyl with 1 to 5 carbon atoms, cycloalkyl with 3 to 6 carbon atoms, alkenyl with 2 to 6 carbon atoms, alkynyl with 2 to 6 carbon atoms, aryl with 6 to 10 carbon atoms, alkoxy with 1 to 7 carbon atoms, and haloalkyl with 1 to 12 carbon atoms. Using cyclic phosphate compounds as a second additive in the electrolyte can synergistically improve the high and low temperature stability of the electrolyte with the first additive, thereby further enhancing the battery's high-temperature storage performance, low-temperature discharge performance, and cycle performance. Cyclic phosphate compounds can undergo oxidation on the positive electrode surface to form phosphate compounds. These compounds remain stable at high voltages, effectively preventing the continuous decomposition of the electrolyte on the positive electrode surface, thus improving the battery's high-temperature performance.

[0042] In some embodiments, the second additive comprises at least one of the following compounds:

[0043]

[0044] The cyclic phosphate ester compounds described in this embodiment have a better effect on improving battery performance. Combining these cyclic phosphate ester compounds with the first additive can effectively protect both the positive and negative electrodes of the battery, further improving the battery's cycle stability.

[0045] In some embodiments, the first additive accounts for 0.1 wt% to 1 wt% of the electrolyte by mass; for example, the first additive may account for one or any two of the following ranges: 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%. If the content of the first additive is too low, it will not be able to suppress the reaction between the active material in the positive electrode and the electrolyte, nor will it be able to improve the stability of the electrolyte. If the content of the first additive is too high, it will cause the passivation film formed on the surface of the positive and negative electrodes to be too thick, increasing the battery impedance.

[0046] In some embodiments, the second additive accounts for 0.2 wt% to 2 wt% of the electrolyte by mass, and the mass ratio of the first additive to the second additive is 1:(2-5). For example, the mass percentage of the second additive in the electrolyte can be any one or any two of the following: 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 1.8 wt%, 1.9 wt%, or 2 wt%. When the content of the second additive is within the above range, it will improve the density of the passivation film at the positive electrode interface, thus stabilizing the interface. In addition, when the mass ratio of the first additive to the second additive is within the above range, it can further enhance the synergistic effect of the first additive and the second additive, promoting further improvement in battery performance.

[0047] In some embodiments, the electrolyte comprises a lithium salt. The lithium salt includes lithium hexafluorophosphate and an auxiliary lithium salt. Further, the auxiliary lithium salt comprises at least one selected from lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium difluorodioxalatophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. In this application, the application of the above-mentioned lithium salts can further effectively passivate the interface and improve the cycle performance of the battery.

[0048] Further, the lithium hexafluorophosphate constitutes 12.0 wt% to 15.0 wt% of the electrolyte by mass; for example, the lithium hexafluorophosphate may be any one or any two of the following: 12.0 wt%, 12.5 wt%, 13.0 wt%, 13.5 wt%, 14.0 wt%, 14.5 wt%, or 15.0 wt%. When the lithium salt content is too low, the ionic conductivity of the electrolyte decreases, affecting the battery's cycle performance; when the content is too high, the viscosity of the electrolyte increases, affecting the battery's kinetic performance.

[0049] Further, the auxiliary lithium salt accounts for 0.1 wt% to 1.0 wt% of the electrolyte by mass; for example, the auxiliary lithium salt can be one or any two of the following: 0.1 wt%, 0.2%, 0.5 wt%, and 1.0 wt%.

[0050] In some embodiments, the electrolyte comprises an organic solvent. Further, the organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butenyl carbonate, fluoroethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, diphenyl carbonate, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, acetonitrile, and sulfolane. Using the above-mentioned organic solvent can improve the stability of the electrolyte, which is beneficial for increasing the migration rate of lithium ions and improving the cycle stability of the battery.

[0051] This application also provides a secondary battery, including the electrolyte described above. Furthermore, the secondary battery further includes a positive electrode, a negative electrode, and a separator.

[0052] In some embodiments, the positive electrode sheet includes a positive electrode active material, which includes a ternary layered oxide. In some embodiments, the ternary layered oxide includes Li. a Ni x Mn y Co z O2, 0.8 < a < 1.2, 0.7 < x < 1, 0 < y < 0.3, 0 < a < 0.2. Using this range of nickel content can improve the energy density of the positive electrode active material, increase the specific capacity of the battery, and extend the discharge time of the battery.

[0053] This application embodiment also provides an electrical device, including the above-mentioned secondary battery, wherein the secondary battery serves as the power supply for the electrical device.

[0054] This application has undergone multiple experiments, and some of the test results are presented here for reference to further describe the invention in detail. The following is a detailed description in conjunction with specific embodiments.

[0055] Example 1

[0056] This embodiment provides an electrolyte comprising a lithium salt, an organic solvent, a first additive, and a second additive. The first additive has a chemical structure including a heterocyclic ring and a thiourea group, and the second additive has a cyclic phosphate ester structure. The first additive is compound 1, and the second additive is compound 7. The specific amounts of the additives are shown in Table 1.

[0057] The secondary battery of this embodiment includes a positive electrode, a negative electrode, and an electrolyte.

[0058] The method for preparing the secondary battery in this embodiment includes the following steps:

[0059] (1) Preparation of electrolyte:

[0060] At room temperature, in an argon-filled glove box (H2O < 1 ppm, O2 < 1 ppm), EC, EMC, and DEC were mixed uniformly at a mass ratio of 3:5:2 to obtain a mixed solvent. LiPF6 was added to the mixed solvent sequentially, followed by lithium difluorophosphate, ultimately yielding a colorless and transparent liquid. Additives were then added to the above colorless and transparent liquid at a specific mass ratio and stirred until homogeneous to obtain the final electrolyte. The electrolyte contained 12.5% ​​LiPF6 by mass and 0.3% lithium difluorophosphate by mass. The specific types and contents of the additives are shown in Table 1, where the content of each additive in Table 1 is a mass percentage calculated based on the total mass of the electrolyte.

[0061] (2) Preparation of the positive electrode sheet:

[0062] The positive electrode active material Li(Ni) 0.8 Mn 0.1 Co 0.1 O2 (NMC811), conductive agent acetylene black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of NMC811:Super P:PVDF = 94:3:3. Then, 1-methyl-2-pyrrolidone (NMP) is added and evenly dispersed to form a uniform black slurry. The mixed slurry is coated on both sides of aluminum foil, and after baking, rolling, and cutting, the positive electrode sheet is obtained.

[0063] (3) Preparation of negative electrode sheet:

[0064] The negative electrode active material graphite, conductive agent acetylene black (Super P) and binder SBR are mixed evenly in a mass ratio of graphite:SuperP:SBR = 94:3:3, and then evenly dispersed in deionized water to form a uniform black slurry. The mixed slurry is coated on both sides of copper foil, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet.

[0065] (4) Fabrication of pouch batteries:

[0066] The prepared positive and negative electrode sheets are stacked in sequence, with the separator in the middle of the positive and negative electrode sheets. After winding, hot pressing and shaping, and welding of the tabs, a bare cell is obtained. The bare cell is placed in an outer packaging aluminum-plastic film and baked in an oven at 85±10℃ for 24 hours. The electrolyte prepared above is injected into the dried battery, and the battery is allowed to stand, form, and be capacity tested to complete the preparation of the lithium-ion soft pack battery.

[0067] Examples 2 to 8

[0068] Examples 2 through 8 each provide a method for preparing a secondary battery, which differs from Example 1 in that the contents of the first additive and the second additive are not exactly the same, as detailed in Table 1. Other conditions are the same as in Example 1.

[0069] Examples 9-16

[0070] Examples 9 through 16 each provide a method for preparing a secondary battery. The difference between these examples and Example 1 is that the specific compounds of the first and second additives are not entirely the same, as detailed in Table 1. Other conditions are the same as in Example 1.

[0071] Example 17

[0072] Similar to Example 1, except that no second additive was added during the preparation of the electrolyte.

[0073] Table 1. Additives and their contents in the examples and comparative examples.

[0074]

[0075]

[0076] The specific compound structures of the first additive (compounds 1-6) and the second additive (compounds 7-12) in the embodiments of this application are as follows:

[0077]

[0078] Examples 18-27

[0079] Examples 18 to 27 each provide a method for preparing a secondary battery. The difference from Example 1 is that the type and content of lithium salt are adjusted. The specific differences are shown in Table 2.

[0080] Table 2

[0081]

[0082] Comparative Example 1

[0083] Comparative Example 1 provides a secondary battery that differs from Example 1 in that: no second additive was used in Comparative Example 1, and the first additive used was dimethylthiourea. All other conditions were the same as in Example 1.

[0084] Comparative Example 2

[0085] Comparative Example 2 provides a secondary battery that differs from Example 1 in that the first additive used in Comparative Example 1 is vinyl sulfite (ES), and the other conditions are the same as in Example 1.

[0086] Comparative Example 3

[0087] Comparative Example 3 provides a secondary battery that differs from Example 1 in that the additives in Comparative Example 1 include a second additive but do not include a first additive. Specific compound types and contents are detailed in Table 1. Other conditions are the same as in Example 1.

[0088] Experimental Example 1

[0089] To verify the performance of the product of this application, the soft-pack batteries prepared in Examples 1-26 and Comparative Examples 1-3 were subjected to room temperature cycling, high temperature storage and low temperature discharge performance tests. The specific methods are as follows, and the results are shown in Table 2.

[0090] Room temperature DCR test: At 25±2℃, the soft pack batteries obtained in Examples 1 to 16 and Comparative Examples 1 to 3 were charged to 4.3V at 1C, then discharged at 1C capacity for 30 minutes. After adjusting to 50% SOC, they were pulsed discharged at 5C constant current for 10 seconds and then charged for 10 seconds. The DCR was calculated as (voltage before pulse discharge and voltage after pulse discharge) / discharge current * 100%. The results are shown in Table 2.

[0091] Room temperature cycle performance test: At 25±2℃, the pouch batteries obtained in Examples 1-26 and Comparative Examples 1-3 were subjected to charge-discharge cycle tests at a charge-discharge rate of 1C / 1C within the range of 2.8-4.3V. The discharge specific capacity of the battery in the first cycle and the discharge specific capacity after 500 cycles were recorded. The capacity retention rate after 500 cycles = discharge specific capacity after 500 cycles / discharge specific capacity in the first cycle * 100%. The recorded data are shown in Table 2.

[0092] High-temperature storage performance: The pouch batteries obtained in Examples 1-26 and Comparative Examples 1-3 were placed at 60±2℃ and subjected to charge-discharge tests at a charge-discharge rate of 1C / 1C within the range of 2.8-4.3V. The discharge specific capacity of the batteries in the first week was recorded. Afterwards, the batteries were stored at 60±2℃ for 30 days, and the charge-discharge tests were performed again, with the discharge specific capacity recorded. High-temperature storage capacity retention rate = discharge specific capacity after 30 days / discharge specific capacity in the first week * 100%. The recorded data are shown in Table 2.

[0093] Low-temperature discharge performance test: The soft-pack batteries obtained in Examples 1-26 and Comparative Examples 1-3 were placed at 25°C and charged at a constant current of 1C to 4.3V, then charged at a constant voltage to a cutoff current of 0.05C, and left to rest for 10 minutes. Then, they were discharged at a constant current of 1C to 2.8V, and the discharge capacity at 25°C was recorded. The batteries were then charged at a constant current of 1C to 4.3V, then charged at a constant voltage to a cutoff current of 0.05C, and placed in a 20°C low-temperature chamber for 2 hours. They were then discharged at a constant current of 1C to 2.8V, and the discharge capacity at -20°C was recorded. The -20°C discharge capacity retention rate = -20°C discharge capacity / 25°C discharge capacity * 100%. The recorded data are shown in Table 2.

[0094] Table 2

[0095]

[0096]

[0097] As shown in Table 2, the analysis of the test results of Examples 1-16 and Comparative Examples 1-3 shows that in Examples 1-16 of this application, the soft-pack batteries obtained by using the first additive and the second additive in the electrolyte have better initial DCR, room temperature cycle performance, high temperature storage performance and low temperature discharge performance than Comparative Examples 1-3.

[0098] As shown in Table 2, the data from Example 17 and Comparative Examples 1 and 2 show that electrolytes containing only thiourea groups or only heterocyclic rings exhibit significantly lower battery performance compared to electrolytes containing both thiourea groups and heterocyclic rings.

[0099] As shown in Table 2, the analysis of the test results of Examples 1-16 and Comparative Example 3 shows that by adding the first additive in Examples 1-11, the initial DCR, low-temperature discharge performance and cycle performance are significantly better than those of Comparative Example 3.

[0100] In summary, the electrolyte of this application, through the addition of a first additive having heterocyclic and thiourea groups and a second additive having a cyclic phosphate ester structure, can improve the high-temperature storage performance, low-temperature discharge performance and cycle performance of the battery.

[0101] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0102] The above description is only a preferred embodiment of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An electrolyte, characterized in that, The electrolyte is used in a secondary battery, which includes a high-nickel cathode material. The electrolyte includes a first additive and a second additive, wherein the mass ratio of the first additive to the second additive is 1:(2~5); the chemical structure of the first additive includes heterocyclic rings and thiourea groups; the chemical structure of the first additive includes the structure shown in Formula I. （I） R1 is selected from at least one of halogen atoms, alkyl groups having 1 to 7 carbon atoms, cycloalkyl groups having 3 to 5 carbon atoms, alkenyl groups having 2 to 5 carbon atoms, alkynyl groups having 2 to 5 carbon atoms, aryl groups having 6 to 10 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, and haloalkyl groups having 1 to 12 carbon atoms. R2 and R3 are each independently selected from at least one of hydrogen atoms, halogen atoms, alkyl groups having 1 to 7 carbon atoms, cycloalkyl groups having 3 to 5 carbon atoms, alkenyl groups having 2 to 5 carbon atoms, alkynyl groups having 2 to 5 carbon atoms, aryl groups having 6 to 10 carbon atoms, alkoxy groups having 1 to 7 carbon atoms, and haloalkyl groups having 1 to 12 carbon atoms. The first additive accounts for 0.1 wt% to 1 wt% of the mass percentage of the electrolyte; The second additive comprises a cyclic phosphate ester compound, and the chemical structure of the second additive includes the structure shown in Formula II: (II) R4 is selected from S or O; R5, R6, and R7 are each independently selected from at least one of cyano, hydrogen atom, nitro, halogen atom, alkyl having 1 to 5 carbon atoms, cycloalkyl having 3 to 6 carbon atoms, alkenyl having 2 to 6 carbon atoms, alkynyl having 2 to 6 carbon atoms, aryl having 6 to 10 carbon atoms, alkoxy having 1 to 7 carbon atoms, and haloalkyl having 1 to 12 carbon atoms. The second additive accounts for 0.2wt% to 2wt% of the electrolyte by mass.

2. The electrolyte according to claim 1, characterized in that, The first additive includes at least one of the following compounds: 。 3. The electrolyte according to claim 1, characterized in that, The second additive includes at least one of the following compounds: 。 4. The electrolyte according to claim 1, characterized in that, The electrolyte comprises a lithium salt, which includes lithium hexafluorophosphate and / or an auxiliary lithium salt; the auxiliary lithium salt includes at least one of lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium difluorodi(oxalato)phosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

5. The electrolyte according to claim 4, characterized in that, The lithium hexafluorophosphate accounts for 12.0 wt% to 15.0 wt% of the electrolyte by mass.

6. The electrolyte according to claim 4, characterized in that, The auxiliary lithium salt accounts for 0.1 wt% to 1.0 wt% of the electrolyte by mass.

7. A secondary battery, characterized in that, Includes the electrolyte as described in any one of claims 1 to 6.

8. Electrical equipment, characterized in that, Includes the secondary battery as described in claim 7, wherein the secondary battery serves as the power supply for the electrical equipment.

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