Electrolyte, battery, battery pack and electric equipment

Abstract

The invention provides an electrolyte, a battery, a battery pack and electric equipment, the electrolyte comprises an organic solvent, an electrolyte salt and an additive, the additive comprises a compound represented by a formula I and / or a formula II, x1, X2, X3 and X4 are respectively and independently selected from one of halogen, substituted or unsubstituted C1-C5 alkyl groups, substituted or unsubstituted C1-C5 alkoxy groups and substituted or unsubstituted aryl groups; r1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15 and R16 are respectively and independently selected from one of H, halogen, substituted or unsubstituted alkyl of C1-C5, substituted or unsubstituted unsaturated alkyl of C1-C5, substituted or unsubstituted alkoxy of C1-C5, and substituted or unsubstituted aryl. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to an electrolyte, in particular to an electrolyte, a battery, a battery pack and an electrical device, belonging to the technical field of secondary batteries. Background Art

[0002] Lithium-ion batteries are a vital part of the current secondary battery field. As the requirements for battery energy density become higher and higher, the conventional operating voltage range is difficult to meet the requirements. However, as the operating voltage increases, the positive electrode active material has a high oxidizing property, and the electrolyte side reaction at the positive electrode interface intensifies, causing the battery to produce gas and swell, which is particularly serious under high temperature conditions. In addition, the transition metal ions dissolved in the positive electrode active material will destroy the protective film (SEI) on the surface of the negative electrode, which will cause the battery to experience a sharp capacity decay and increased impedance.

[0003] During the use of lithium-ion batteries, the ability to balance high and low temperature performance has always been the focus of battery research. Under low temperature conditions, conventional electrolytes have increased viscosity, decreased conductivity, slower lithium ion migration, and increased battery interface impedance, which leads to increased battery polarization and decreased charge and discharge capacity. For charging under low temperature conditions, severe lithium precipitation may even affect battery safety. At present, most of the electrolyte industry uses a combination of multiple functional additives to balance the high and low temperature performance of the battery, but this also increases the cost of the electrolyte.

[0004] Therefore, it is of great significance to develop and use electrolyte additives that can simultaneously and efficiently improve the high and low temperature performance of batteries. Summary of the invention

[0005] The present invention provides an electrolyte, which can enable a battery to exhibit excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

[0006] The present invention provides a battery having excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

[0007] The present invention provides a battery pack having excellent high temperature cycle performance, high temperature storage performance and low temperature discharge performance.

[0008] The present invention also provides an electrical device, which includes a battery. The electrical device has high high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance, which is conducive to the application of the electrical device in high-temperature and low-temperature environments.

[0009] In one aspect, the present invention provides an electrolyte solution, comprising an organic solvent, an electrolyte salt and an additive, wherein the additive comprises a compound represented by Formula I and / or Formula II:

[0010]

[0011] In Formula I and Formula II, X1, X2, X3, and X4 are each independently selected from halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, and substituted or unsubstituted aryl; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 Each is independently selected from one of H, halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, substituted or unsubstituted C1-C5 alkoxy group, and substituted or unsubstituted aryl group.

[0012] In the electrolyte as described above, the additive comprises one or more of the following compounds:

[0013]

[0014] In the electrolyte as described above, based on the total mass of the electrolyte, the mass content of the compound represented by Formula I and / or Formula II is 0.1% to 10%.

[0015] In the electrolyte as described above, based on the total mass of the electrolyte, the mass content of the compound represented by Formula I and / or Formula II is 0.3% to 5%.

[0016] In the electrolyte solution described above, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalatoborate, lithium bisfluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethylsulfonyl)imide and bisfluorosulfonyl imide electrolyte salts.

[0017] In the electrolyte solution as described above, the concentration of the electrolyte salt is 0.5 to 2 mol / L.

[0018] In the electrolyte as described above, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate.

[0019] Another aspect of the present invention provides a battery, comprising the electrolyte as described above.

[0020] According to another aspect of the present invention, a battery pack is provided, comprising the battery as described above.

[0021] Another aspect of the present invention provides an electrical device, comprising the battery or the battery pack as described above.

[0022] The electrolyte provided by the present invention includes a compound of a "spiro" structure shown in Formula I and / or Formula II, which can be preferentially oxidized and decomposed on the surface of the positive electrode to form a complete, dense and uniform protective film (CEI), thereby effectively reducing the contact between the electrolyte and the active material, reducing the gas production of the positive electrode side reaction, inhibiting the dissolution of transition metal ions, and improving the cycle life and storage performance of lithium-ion batteries; and can participate in the film formation (SEI) at the negative electrode, decompose in the first cycle, adjust and modify the negative electrode SEI film components and morphology, and achieve uniform SEI film thickness and high ion conductivity through dosage regulation, which can effectively reduce the negative electrode interface impedance, thereby improving the low temperature performance of the battery. On the other hand, the compound can react with trace water in the electrolyte to avoid the dissolution and damage of the positive and negative electrode passivation films by impurities such as HF generated by the reaction of LiPF6 and H2O; it can combine with the Lewis acid PF5 generated by the decomposition of LiPF6 at high temperature to avoid the decomposition reaction of the PF5 catalytic solvent. The lithium-ion battery prepared using this electrolyte can maintain excellent low-temperature performance, cycle performance, high-temperature storage performance and the effect of inhibiting battery gas production at high voltage. At the same time, it can inhibit the impedance growth during the battery cycle and further improve the low-temperature performance. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0024] In one aspect, the present invention provides an electrolyte solution, comprising an organic solvent, an electrolyte salt and an additive, wherein the additive comprises a compound represented by Formula I and / or Formula II:

[0025]

[0026] In Formula I and Formula II, X1, X2, X3, and X4 are each independently selected from halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, and substituted or unsubstituted aryl; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R13 , R 14 , R 15 , R 16 Each is independently selected from one of H, halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 unsaturated hydrocarbon group, substituted or unsubstituted C1-C5 alkoxy group, and substituted or unsubstituted aryl group.

[0027] In the embodiment of the present invention, the substituted or unsubstituted C1~C5 alkyl group refers to a substituted or unsubstituted chain alkyl group with 1-5 carbon atoms, or a substituted or unsubstituted cycloalkyl group with 3-5 carbon atoms; wherein the chain alkyl group can be a straight chain alkyl group without branches, or an isomeric alkyl group with branches; illustratively, the carbon number of the C1~C5 alkane group can be 1, 2, 3, 4 or 5.

[0028] Alkoxy is usually represented by RO-, where R represents an alkyl group, and the alkyl group is a chain alkyl group or a cycloalkyl group composed of carbon and hydrogen atoms. In the embodiments of the present invention, the substituted or unsubstituted C1-C5 alkoxy group refers to an alkoxy group in which the alkyl part consists of 1 to 5 carbon atoms, and the alkyl group may be unsubstituted or substituted.

[0029] In the embodiments of the present invention, the substituted or unsubstituted aryl group refers to an aryl group having a substituent or being unsubstituted.

[0030] The substituents in all the above substituted or unsubstituted groups can be C1-C5 alkyl, aryl, etc. The substitution positions of the substituents in the above substituted or unsubstituted groups can be selected according to actual needs.

[0031] R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 The groups may be partially or entirely the same, or entirely different.

[0032] According to the above scheme provided by the present invention, after the electrolyte is applied to the battery, the battery has excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance. The inventor analyzed this and believed that the reason may be that: on the one hand, the electrolyte provided by the present invention includes a compound of a "spiro" structure shown in Formula I and / or Formula II, which can be preferentially oxidized and decomposed on the surface of the positive electrode to form a complete, dense and uniform protective film (CEI), thereby effectively reducing the contact between the electrolyte and the active material, reducing the gas production of the positive electrode side reaction, inhibiting the dissolution of transition metal ions, and improving the cycle life and storage performance of lithium-ion batteries; on the other hand, the compound of the "spiro" structure shown in Formula I and / or Formula II can participate in film formation (SEI) at the negative electrode, decompose in the first cycle, adjust and modify the negative electrode SEI film components and morphology, and achieve uniform SEI film thickness and high ionic conductivity through dosage regulation, which can effectively reduce the negative electrode interface impedance, thereby improving the low temperature performance of the battery. On the other hand, the compound can react with trace water in the electrolyte to prevent impurities such as HF produced by the reaction of LiPF6 and H2O from dissolving and damaging the positive and negative electrode passivation films; it can combine with the Lewis acid PF5 produced by the decomposition of LiPF6 at high temperatures to prevent the PF5-catalyzed solvent from decomposing. The lithium-ion battery prepared with this electrolyte can maintain excellent low-temperature performance, cycle performance, high-temperature storage performance and inhibit battery gas production at high voltages, and can also inhibit the impedance growth during the battery cycle, further improving the low-temperature performance.

[0033] Further, in one embodiment of the present invention, the additive comprises one or more of the following compounds:

[0034]

[0035] The present invention does not limit the sources of Formula I-1, Formula I-2, Formula II-1 and Formula II-2, which can be purchased through commercial channels or prepared by themselves.

[0036] In a specific embodiment, Formula I-1 is obtained by reacting the compounds represented by Formula 1 and Formula 2 under the action of a basic catalyst.

[0037]

[0038] In another specific embodiment, the compound shown in Formula II-1 is obtained by reacting the compound shown in Formula 3 with phosphorus trichloride and anhydrous dichloromethane to obtain an intermediate shown in Formula 4, and then the intermediate is reacted with antimony trifluoride under a nitrogen atmosphere to obtain the compound shown in Formula II-1.

[0039]

[0040] When the above-mentioned types of additives are used, the additives can better participate in the construction of the CEI film and the SEI film, making the CEI film more stable, thereby better protecting the positive electrode active material, further improving the high-temperature cycle performance and high-temperature storage performance of the battery, and the impedance of the SEI film is lower, which makes the impedance of the battery lower, thereby making the low-temperature discharge performance of the battery better.

[0041] Furthermore, in a specific embodiment of the present invention, based on the total mass of the electrolyte, the mass content of the compound represented by Formula I and / or Formula II is 0.1% to 10%, preferably 0.3% to 5%.

[0042] In detail, the mass content of the compound represented by Formula I and / or Formula II includes but is not limited to 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range between any two thereof.

[0043] When the mass content of the compound represented by Formula I and / or Formula II is within the above range, the thickness of the CEI film and SEI film constructed by the compound is appropriate, so that the positive electrode active material can be adequately protected, and the CEI film and SEI film can be prevented from being too thick, resulting in an increase in the impedance of the battery, thereby better improving the high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance of the battery.

[0044] Preferably, the mass content of the compound represented by Formula I and / or Formula II is 0.3%-5%. When it is within this range, the compound can play a better role and make the performance of the battery more excellent.

[0045] It can be understood that when the electrolyte includes the compounds represented by Formula I and Formula II at the same time, the mass relationship between the compound represented by Formula I and the compound represented by Formula II can be adjusted according to actual needs.

[0046] Further, in a specific embodiment of the present invention, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalatoborate, lithium bisfluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethylsulfonyl)imide and bisfluorosulfonyl imide electrolyte salts.

[0047] The above-mentioned types of electrolyte salts provide lithium ions, which migrate between the positive and negative electrodes through the electrolyte during the battery charging and discharging process to achieve battery energy storage and release. In addition, the presence of electrolyte salts can reduce side reactions and decomposition phenomena during battery operation, further improving the stability of the battery.

[0048] The appropriate electrolyte salt mass content can be selected according to actual needs. In a specific embodiment, the concentration of the electrolyte salt is 0.5-2 mol / L. For example, the concentration of the electrolyte salt includes but is not limited to 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2.0 mol / L or a range between any two of them.

[0049] When the concentration of the electrolyte salt is within the above range, it can effectively support the movement of ions in the electrolyte, ensure that the electrolyte has a high conductivity, and achieve effective ion conduction.

[0050] Preferably, the concentration of the electrolyte salt is 0.9-1.3 mol / L. When the concentration of the electrolyte salt is within this range, the conductivity and stability are higher.

[0051] Further, in a specific embodiment of the present invention, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate.

[0052] When the organic solvent includes the above-mentioned types, it can effectively dissolve the compounds shown in Formula I and / or Formula II, electrolyte salts and vinylene carbonate, etc., providing a basis for ion migration in the electrolyte. At the same time, the above-mentioned types of organic solvents have good electrochemical stability, further improving the high-temperature storage performance, high-temperature cycle performance and low-temperature discharge performance of the battery.

[0053] It can be understood that the overall viscosity of the electrolyte can be adjusted by controlling the mass content of the organic solvent in the electrolyte.

[0054] The embodiment of the present invention does not limit the preparation method of the electrolyte. In a specific implementation, it is sufficient to mix the compound represented by Formula I and / or Formula II, electrolyte salt, vinylene carbonate, organic solvent, etc. in a specified ratio.

[0055] Another aspect of the present invention provides a battery, comprising the electrolyte as described above.

[0056] Since the battery provided by the present invention includes the above-mentioned electrolyte, the battery exhibits excellent high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.

[0057] It can be understood that the battery also includes a positive electrode plate, a negative electrode plate, a separator, etc.

[0058] In a specific embodiment, the battery is a lithium-ion battery, and the positive electrode plate specifically includes a positive electrode current collector and a positive electrode active layer formed of a positive electrode active material and disposed on the surface of the positive electrode current collector.

[0059] Among them, the positive electrode current collector and positive electrode active material commonly used in the art can be selected.

[0060] The negative electrode sheet specifically includes a negative electrode current collector and a negative electrode active layer formed of a negative electrode active material and arranged on the surface of the negative electrode current collector.

[0061] Among them, the negative electrode current collector and negative electrode active material commonly used in the art can be selected.

[0062] The present invention does not strictly limit the material selection of the diaphragm, and the diaphragm material commonly used at present can be used.

[0063] The common methods in the art can be used to make the battery. In a specific embodiment, the positive electrode sheet, the negative electrode sheet and the separator are made into a pole core through the Z-stack process. After the pole core is loaded into an aluminum-plastic film packaging shell, the electrolyte as described above is injected, and then sealed in sequence. After standing, hot and cold pressing, formation, capacity separation and other processes, the battery is manufactured.

[0064] Another aspect of the present invention provides a battery pack including the above-mentioned battery.

[0065] The battery pack has the same advantages as the above-mentioned electrolyte, which will not be described in detail.

[0066] Generally, a battery pack includes a plurality of the above-mentioned batteries, which are connected as single cells to form a battery pack. The batteries can be electrically connected by conventional methods in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0067] Another aspect of the present invention provides an electrical device including the battery as described above.

[0068] The electrical equipment in the embodiments of the present invention can be conventional electrical equipment in the field, such as power equipment (such as electric vehicles, electric cars), electronic equipment (such as mobile phones, tablet computers, laptops, digital cameras, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), energy storage power stations, etc., without special restrictions.

[0069] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] The present invention is further described below by specific examples and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, conventional materials and conventional instruments, which can be commercially available, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0071] Example 1

[0072] The preparation method of the electrolyte of this embodiment comprises the following steps:

[0073] An electrolyte is prepared in a glove box, which is filled with argon gas with a purity of 99.999%, the moisture in the glove box is controlled at ≤0.1ppm, and the temperature is controlled at room temperature. Ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) are mixed in a mass ratio of EC:DMC:DEC=3:2:5, and then lithium hexafluorophosphate (LiPF6) is added to a molar concentration of 1.1 mol / L, and then the additives shown in Formula I and / or Formula II are added to obtain an electrolyte.

[0074] The preparation methods of the electrolytes of Examples 2-13 and Comparative Examples 1-3 are basically the same as that of Example 1, but there are certain differences in the types of additives, types of electrolyte salts, and the contents of each component, as shown in Table 1.

[0075] Among them, the electrolyte provided in Comparative Example 1 includes the compound shown in Formula III, and the electrolyte provided in Comparative Example 2 includes the compound shown in Formula IV.

[0076]

[0077] Table 1

[0078]

[0079] Test example

[0080] The electrolyte of the embodiment and the comparative example is combined with a positive electrode sheet, a negative electrode sheet and a separator to prepare a lithium ion battery. Specifically, the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), conductive material CNT, conductive carbon black and binder (polyvinylidene fluoride) PVDF are dispersed in solvent NMP in a mass ratio of 94:2:2:2 to obtain a positive electrode active material layer slurry; the positive electrode active material layer slurry is evenly coated on the surface of the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained after drying, rolling, baking, slitting and spot welding of the pole ears.

[0081] The negative electrode active material artificial graphite, conductive agent conductive carbon black, CNT, sodium carboxymethyl cellulose and binder SBR are dispersed in deionized water in a mass ratio of 95:1.25:1.25:1.25:1.25, and stirred evenly to obtain a negative electrode active material layer slurry; the negative electrode active material layer slurry is evenly coated on the surface of the negative electrode current collector copper foil, and the negative electrode sheet is obtained after drying, rolling, baking, slitting and spot welding of the electrode ears.

[0082] The prepared positive electrode sheet, negative electrode sheet and separator are stacked in order, a ceramic coated separator is selected as the separator, and the separator is placed between the positive electrode sheet and the negative electrode sheet. After winding, the battery cell is placed in an aluminum-plastic film package, dried, and sealed by injecting electrolyte. After standing, forming, secondary sealing, capacity division and other processes, a lithium-ion battery is obtained.

[0083] The following battery performance tests were performed on lithium batteries including the electrolytes of the embodiments and comparative examples, and the test methods were as follows:

[0084] (1) Low temperature (-20℃) discharge capacity ratio

[0085] After the battery is charged to 4.45V at 1C constant current at 25℃, it is switched to constant voltage charging to a cutoff current of 0.05C, left to stand for 0.5h, and then discharged to 2.5V at 1C constant current. This discharge capacity is calculated as C0; after the battery is charged to 4.45V at 1C constant current at 25℃, it is switched to constant voltage charging to a cutoff current of 0.05C, left to stand for 0.5h, the battery is transferred to a -20℃ environmental box, left for 6h, and then discharged to 2.5V at 0.2C constant current. This discharge capacity is calculated as C1; low temperature (-20℃) discharge capacity ratio (%) = (C1 / C0) × 100%, specific test results are shown in Table 2.

[0086] (2) High temperature (45°C) cycle test

[0087] In a 45°C constant temperature box, the battery is charged to 4.45V at a constant current of 1C, then switched to constant voltage charging to a cutoff current of 0.05C, left to stand for 0.5h, and then discharged to 2.5V at a constant current of 1C, which is recorded as one charge and discharge cycle. Then, 500 cycles are performed according to the above conditions; the discharge capacity of the first cycle is recorded as C0, and the discharge capacity of the 500th cycle is recorded as C1; high temperature (45°C) cycle capacity retention rate (%) = (C1 / C0) × 100%; specific test results are shown in Table 2.

[0088] (3) High temperature (55°C) storage test

[0089] The lithium-ion battery was charged to 4.45V at 25°C with a constant current of 1C to a constant voltage, and then the battery was cut off at 0.05C, and then the battery was left standing for 0.5h, and then the battery was discharged to 2.5V at a constant current of 1C. The discharge capacity was calculated as the initial capacity C0, and the battery thickness before storage was measured as H0. The battery was transferred to a high-temperature test cabinet and stored at 55°C for 28 days. After the storage was completed, the test battery was taken out and left at room temperature for 10h, and the battery thickness after storage was measured as H1, and then the battery was discharged to 2.5V at a constant current of 1C, and the discharge capacity C1 was recorded. After leaving for 2h, the battery was charged to 4.45V at a constant current of 1C to a constant voltage, and then the battery was cut off at 0.05C. After leaving for 0.5h, the battery was discharged to 2.5V at a constant current of 1C, and the discharge capacity C2 was recorded.

[0090] High temperature (55°C) storage capacity remaining rate (%) = (C1 / C0)*100%;

[0091] High temperature (55°C) storage capacity recovery rate (%) = (C2 / C0)*100%.

[0092] Battery thickness growth rate (%) = [(H1-H0) / H0]*100%

[0093] The specific test results are shown in Table 2.

[0094] Table 2

[0095]

[0096]

[0097] Comparing the data of Examples 1 to 4, it can be seen that when the mass content of the compound shown in Formula I and / or Formula II in the electrolyte is less than 0.3%, a complete passivation film cannot be formed at the positive and negative electrodes, and the high and low temperature performance is relatively poor, but the high temperature cycle and high temperature storage are still improved to a certain extent compared with the non-added group (Comparative Example 3). As the mass percentage of the compound shown in Formula I and / or Formula II increases, the high and low temperature performance is significantly improved; when the addition amount is increased to 2% by comparing Example 3 with Example 4, in addition to participating in the film formation of the positive and negative electrodes, it also plays a "water removal and acid suppression" effect, further inhibiting the increase in the thickness of the battery core, but at the same time, due to the corresponding increase in the number of additives participating in the negative electrode film formation reaction, the SEI film formed on the negative electrode surface is thickened, and the interface impedance is improved to a certain extent, thereby deteriorating the low temperature performance of the battery.

[0098] Comparing the data of Example 3 with Example 5, and Example 6 with Example 7, it can be seen that different substituents on the P atom of the hexacyclic heterocycle have different effects. From the comparison of "fluorine substitution" and "methoxy substitution", the two are very similar in high-temperature cycling performance, but "fluorine substitution" has better low-temperature performance, while "methoxy substitution" has better high-temperature storage performance and is also better in suppressing gas production. Comparing the data of Example 3 with Example 6, and Example 5 with Example 7, it can be seen that the "P=O" bond also has a significant effect on the effect. The presence of "P=O" can improve high-temperature storage performance and has a certain degree of degradation on low-temperature discharge.

[0099] By comparing Example 3 with Comparative Example 1, and Example 6 with Comparative Example 2, it can be seen that by designing to connect two dioxaphosphorinane compounds in the form of a "spirocycle", the new compound has obvious advantages when used as an additive for lithium-ion battery electrolyte and achieves good application effects.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte comprising an organic solvent, an electrolyte salt and an additive, characterized in that: The additives include compounds shown in Formula I and / or Formula II: In Formula I and Formula II, X1, X2, X3, and X4 are each independently selected from halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 alkoxy, and substituted or unsubstituted aryl; R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 Each is independently selected from one of H, halogen, substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C1-C5 unsaturated hydrocarbon group, substituted or unsubstituted C1-C5 alkoxy group, and substituted or unsubstituted aryl group.

2. The electrolyte according to claim 1, characterized in that The additives include one or more of the following compounds:

3. The electrolyte according to claim 1 or 2, characterized in that Based on the total mass of the electrolyte, the mass content of the compound represented by Formula I and / or Formula II is 0.1% to 10%.

4. The electrolyte according to claim 3, characterized in that Based on the total mass of the electrolyte, the mass content of the compound represented by Formula I and / or Formula II is 0.3% to 5%.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bisfluorooxalatoborate, lithium bisfluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium bis(trifluoromethylsulfonyl)imide, and bisfluorosulfonyl imide electrolyte salts.

6. The electrolyte according to claim 5, characterized in that The concentration of the electrolyte salt is 0.5 to 2 mol / L.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The organic solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate.

8. A battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 7.

9. A battery pack, characterized in that: Comprising the battery as claimed in claim 8.

10. An electrical device, characterized in that: Comprising the battery according to claim 8 or the battery pack according to claim 9.

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