Electrolyte, battery, battery pack and electric equipment

Abstract

The invention provides an electrolyte, a battery, a battery pack and electric equipment. The electrolyte comprises a first additive and a second additive, wherein the first additive is a phosphine leaf rid compound, and the second additive is an aldehyde group compound. After the electrolyte is applied to the battery, the cycle performance and the rate capability of the battery can be remarkably improved.

Description

Technical Field

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

[0002] Secondary batteries consist of positive electrodes, negative electrodes, electrolytes, separators and other components, among which the electrolyte plays a vital role in secondary batteries. The electrolyte is not only a medium for ion conduction, but also plays a key role in the overall performance, safety and life of the battery.

[0003] Adding functional additives to the electrolyte can help form a stable solid electrolyte cross-section layer, inhibit side reactions, and significantly improve the performance of secondary batteries. However, most functional additives have relatively single functions. For example, the commonly used functional additive vinyl carbonate can improve the high-temperature cycle stability of the battery, but its film formation impedance is large and it cannot take into account power performance. The SEI film formed by functional additives such as fluoroethylene carbonate and DTD has low impedance and good power performance, but the high-temperature stability is insufficient and gas production is serious.

[0004] How to achieve both high temperature performance and rate performance has become a technical problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0005] The present invention provides an electrolyte, which comprises a first additive and a second additive with a specific structural formula. Under the synergistic effect of the first additive and the second additive, a battery has excellent high-temperature cycle performance and rate performance.

[0006] The present invention also provides a battery, which comprises the above electrolyte and thus has excellent high-temperature cycle performance and rate performance.

[0007] The present invention also provides a battery pack, which includes the battery and has excellent high-temperature cycle performance and rate performance.

[0008] The present invention also provides an electrical device, which comprises the battery or battery pack and has excellent performance.

[0009] In one aspect, the present invention provides an electrolyte comprising a first additive and a second additive;

[0010] The chemical formula of the first additive is shown in Formula 1, and the chemical formula of the second additive is shown in Formula 2:

[0011]

[0012] Wherein, R1, R2, R3, and R4 are each independently selected from at least one of H, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted epoxyalkyl, substituted or unsubstituted boroxyalkyl, substituted or unsubstituted aryl, substituted or unsubstituted keto, substituted or unsubstituted ester, and substituted or unsubstituted nitrile.

[0013] The electrolyte as described above, wherein R1, R2, R3, and R4 are selected from substituted or unsubstituted aryl groups, and the number of carbon atoms of R1, R2, R3, and R4 are independently selected from 6 to 12;

[0014] And / or, R1, R2, R3, and R4 are each independently selected from at least one of an alkyl group, a cycloalkyl group, an epoxyalkyl group, a boroxyalkyl group, an aryl group, an alkoxy group, a substituted or unsubstituted keto group, a substituted or unsubstituted ester group, and a substituted or unsubstituted nitrile group, and the number of carbon atoms of R1, R2, R3, and R4 are each independently selected from 6 to 12.

[0015] In the electrolyte as described above, the first additive includes at least one of triphenylphosphine ylide, cyanomethylene triphenylphosphine ylide, triphenylphosphine methyl ylide, methoxycarbonylmethylene triphenylphosphine, isocyanoimino triphenylphosphine, and allyl triphenylphosphine ylide;

[0016] And / or, the second additive includes at least one of benzylaldehyde, cinnamaldehyde, phenylethylaldehyde, p-methylcinnamaldehyde, α-hexylcinnamaldehyde, and 2-pentenal.

[0017] For the electrolyte as described above, based on the mass of the electrolyte, the sum of the mass proportions of the first additive and the second additive is 0.1% to 5%.

[0018] In the electrolyte as described above, the molar ratio of the first additive to the second additive is (0.8-1.2):1.

[0019] The electrolyte as described above further comprises a lithium salt, wherein the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium perchlorate;

[0020] Based on the mass of the electrolyte, the mass proportion of the lithium salt is 0.1% to 13%.

[0021] The electrolyte as described above further comprises a solvent, wherein the solvent is selected from at least one of carbonate solvents, carboxylic acid ester solvents, and ether solvents;

[0022] Based on the mass of the electrolyte, the mass proportion of the solvent is 10%-90%.

[0023] Another aspect of the present invention provides a battery, comprising the electrolyte as described above.

[0024] According to another aspect of the present invention, a battery pack is provided, comprising the battery as described above.

[0025] Another aspect of the present invention provides an electrical device, comprising the battery or the battery pack as described above.

[0026] The electrolyte provided by the present invention combines a first additive as shown in Formula 1 and a second additive as shown in Formula 2 to exert the synergistic effect of the first additive and the second additive. On the one hand, a flexible [-R-CHO-]n polymer is generated to alleviate and improve the high-temperature cycle performance of the battery. On the other hand, a SEI / CEI film rich in inorganic Li3PO4 can be formed on the surface of the positive electrode sheet and the negative electrode sheet. Li3PO4 has good lithium ion conductivity, can effectively conduct lithium ions, reduce interface impedance, and improve the rate performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Cyclic voltammetry test curves of batteries prepared with the electrolytes provided in Example 3 of the present invention and Comparative Example 1;

[0028] Figure 2 A partial enlarged view of the cyclic voltammetry test curve of the battery prepared with the electrolyte provided in Example 3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of 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.

[0030] The poor high-temperature cycle performance and rate performance of the battery are usually related to the properties of the electrolyte and the behavior of the electrode material. In a high-temperature environment, the electrolyte is prone to decomposition reactions, generating gases and other byproducts, and the electrode material is also prone to volume changes, resulting in structural damage and affecting the battery's cycle performance. In a low-temperature environment, the ion mobility will be relatively low, and low temperatures will also increase the resistance of the SEI film, resulting in poor high-temperature cycle performance and rate performance of the battery.

[0031] If the electrolyte can protect the electrode through a stable SEI film on the electrode surface under high temperature conditions and increase the lithium ion transmission channel, the high temperature cycle performance and rate performance of the battery will be improved.

[0032] In one aspect, the present invention provides an electrolyte comprising a first additive and a second additive;

[0033] The chemical formula of the first additive is shown in Formula 1, and the chemical formula of the second additive is shown in Formula 2:

[0034]

[0035] Wherein, R1, R2, R3, and R4 are each independently selected from at least one of H, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted epoxyalkyl, substituted or unsubstituted boroxyalkyl, substituted or unsubstituted aryl, substituted or unsubstituted keto, substituted or unsubstituted ester, and substituted or unsubstituted nitrile.

[0036] The first additive provided by the present invention is a phosphine ylide compound.

[0037] Substitution in the present invention means that the hydrogen atom on the group is replaced by other atoms or groups, while unsubstituted means that the hydrogen atom on the group is not replaced by other atoms or groups. For example, the unsubstituted keto group in the present invention refers to a simple keto structure, usually a carbon atom connected to an oxygen atom (C=O) through a double bond, and this carbon atom is connected to two other carbon atoms. Substituted keto means that one or two carbon atoms connected to the carbon atom on the keto are replaced by other groups, and these substituents can be alkyl, aryl, etc. Unsubstituted ester refers to a basic ester structure, for example, ethyl acetate. Substituted ester means that R or R' in the ester is replaced by other groups, and these substituents can be more complex hydrocarbon groups or other functional groups. Unsubstituted nitrile refers to a simple nitrile structure, usually a carbon atom connected to a nitrogen atom (C≡N) through a triple bond. Substituted nitrile means that the hydrogen atom connected to the carbon atom on the nitrile is replaced by other groups, and these substituents can be alkyl, aryl, etc.

[0038] According to the above scheme provided by the present invention, when the electrolyte includes the first additive and the second additive, the battery has excellent high-temperature cycle performance and rate performance. On the one hand, the carbon anion part of the first additive having the structural formula shown in Formula 1 attacks the carbonyl carbon in the second additive in an electrochemical reduction environment, and finally generates α, β unsaturated aldehyde RCH=CHO after a series of reactions. This substance is very easy to polymerize to generate a flexible [-R-CHO-]n polymer, which improves the high-temperature cycle performance of the battery. The carbonyl carbon in the polymer has good lithium ion conductivity and is also conducive to the transmission of lithium ions. On the other hand, the first additive and the second additive react to generate triphenylphosphine oxide, which can form a SEI / CEI film rich in inorganic substances Li3P and Li3PO4 on the surface of the positive electrode and the negative electrode, which is beneficial to reduce the interface impedance and improve the rate performance of the battery.

[0039] In one embodiment, R1, R2, R3, and R4 are selected from substituted or unsubstituted aryl groups, and the number of carbon atoms of R1, R2, R3, and R4 are independently selected from 6 to 12;

[0040] In another specific embodiment, R1, R2, R3, and R4 are each independently selected from at least one of an alkyl group, a cycloalkyl group, an epoxyalkyl group, a boroxyalkyl group, an aryl group, an alkoxy group, a substituted or unsubstituted keto group, a substituted or unsubstituted ester group, and a substituted or unsubstituted nitrile group, and the number of carbon atoms of R1, R2, R3, and R4 are each independently selected from 6 to 12.

[0041] When the number of carbon atoms in R1, R2, R3 and R4 is within the above range, the reaction between the two additives is more likely to occur, more effective film-forming components are generated, and the effect is more obvious.

[0042] In a specific embodiment, the first additive is selected from at least one of triphenylphosphine ylide, cyanomethylene triphenylphosphine ylide, triphenylphosphine methyl ylide, (methoxycarbonylmethylene) triphenylphosphine, (isocyanimino) triphenylphosphine, and allyl triphenylphosphine ylide.

[0043] When the first additive is selected from the above types, it has a certain steric hindrance, which affects the reaction selectivity of the first additive, prevents certain unnecessary side reactions, and improves the selectivity of the target reaction. In addition, the above type of first additive can effectively disperse the charge through the conjugated system and increase the stability of the compound.

[0044] In another specific embodiment, the second additive is selected from at least one of benzylaldehyde, cinnamaldehyde, phenylethylaldehyde, p-methylcinnamaldehyde, α-hexylcinnamaldehyde, and 2-pentenal.

[0045] When the second additive is selected from the above types, the conjugated system in the aromatic group in the second additive can help disperse the charge and improve the stability of the second additive. In addition, the second additive has high reactivity and can improve the reaction efficiency with the first additive, thereby improving battery performance.

[0046] In a specific embodiment, the first additive is triphenylphosphine methyl ylide, the second additive is R4CHO, and the chemical formula of the reaction between the first additive and the second additive is shown in Formula 3.

[0047] C6H5CH=PPh3+R4CHO→C6H5CH=CHR4+Ph3PO Formula 3.

[0048] As important functional components, the mass content of the first additive and the second additive in the electrolyte will have a certain impact on the high temperature cycle performance and rate performance of the battery. In a specific embodiment, based on the mass of the electrolyte, the sum of the mass proportions of the first additive and the second additive is 0.1% to 5%.

[0049] In detail, the sum of the mass proportions of the first additive and the second additive includes but is not limited to 0.1%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or a range between any two of them.

[0050] When the sum of the mass proportions of the first additive and the second additive is within the above range, the amount of film-forming products of the two additives is controlled within the optimal range, so that high and low temperature performance can be taken into account. Too much addition will cause the additive film to be thicker, which will have an adverse effect on power. Too little addition will cause insufficient film formation and poor high temperature performance.

[0051] Since the related products formed by the reaction of the first additive and the second additive in the electrolyte affect the high temperature cycle performance and rate performance of the battery, it is necessary to control the amount of substance between the first additive and the second additive. In a specific embodiment, the molar ratio of the first additive to the second additive is (0.8-1.2):1.

[0052] In detail, the molar ratio of the first additive to the second additive includes but is not limited to 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1 or a range between any two thereof.

[0053] Preferably, in one embodiment, the molar ratio of the first additive to the second additive is 1:1.

[0054] When the molar ratio of the first additive to the second additive is within the above range, it is easier to achieve reaction equilibrium, improve reaction efficiency and product selectivity, and avoid the adverse effects of excessive residual first additive and second additive on the electrolyte.

[0055] For lithium-ion batteries, lithium ions move between the positive electrode and the negative electrode during the charge and discharge process, and lithium salt is the main source of lithium ions in the electrolyte. In a specific embodiment, the electrolyte further includes a lithium salt, which is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium perchlorate.

[0056] Based on the mass of the electrolyte, the mass proportion of lithium salt is 0.1% to 13%.

[0057] The above-mentioned types of lithium salts have good electrical conductivity and chemical stability, and will not produce excessive by-products in high temperature and low temperature environments to affect battery performance.

[0058] In detail, the mass proportion of lithium salt includes but is not limited to 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 13% or a range between any two of them.

[0059] When the mass proportion of lithium salt is within the above range, lithium salt can achieve a balance between optimizing the conductivity and stability of the electrolyte while ensuring cost-effectiveness.

[0060] Furthermore, in a specific embodiment, the concentration of the lithium salt is 0.1 mol / L to 5 mol / L.

[0061] In detail, the lithium salt concentration includes but is not limited to 0.1 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L or a range between any two of them.

[0062] When the lithium salt concentration is within the above range, the electrolyte can usually provide sufficient lithium ion conductivity to support efficient charge transfer and battery performance. In addition, the appropriate lithium salt concentration helps to form a stable solid electrolyte interface (SEI) layer on the electrode surface. This protective film can prevent direct contact between the electrolyte and the electrode material, thereby improving the cycle life and safety of the battery.

[0063] In a specific embodiment, it further comprises a solvent, and the solvent is selected from at least one of carbonate solvents, carboxylic acid esters, and ether solvents;

[0064] Based on the mass of the electrolyte, the mass of the solvent accounts for 10%-90%.

[0065] The carbonate solvent is a cyclic or chain carbonate and its derivatives, preferably, one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, and ethyl butyrate are selected; the carboxylate solvent is a linear or branched carboxylate and its derivatives, preferably, one or more of γ-butyrolactone, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate are selected; the ether solvent may include glycol ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, etc., diethylene glycol ethers such as diethylene glycol dimethyl ether, etc., triethylene glycol ethers such as triethylene glycol dimethyl ether, etc., and tetraethylene glycol ethers such as tetraethylene glycol dimethyl ether, etc.

[0066] The above-mentioned types of solvents can serve as solvent carriers for electrolytes, helping to separate cations and anions in the electrolyte and transfer charges between electrodes. At the same time, they can improve the conductivity of the entire electrolyte, which is beneficial to the charge and discharge efficiency and energy density of the battery.

[0067] In detail, the mass proportion of the solvent includes but is not limited to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or a range between any two thereof.

[0068] When the mass percentage of the solvent is within the above range, the conductivity of the electrolyte can be further improved, thereby improving the cycle performance of the battery to a greater extent.

[0069] Another aspect of the present invention provides a battery, comprising the electrolyte as described above.

[0070] Since the electrolyte is included, the battery has excellent high-temperature cycle performance and rate performance.

[0071] In a specific embodiment, in addition to the electrolyte provided by the present invention, it also includes a positive electrode sheet, a negative electrode sheet and a separator. During the charge and discharge process of the battery, active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the short circuit between the positive electrode sheet and the negative electrode sheet, and at the same time to allow ions to pass through.

[0072] Another aspect of the present invention provides a battery pack, comprising the battery as described above, so as to have high temperature cycle performance and rate performance.

[0073] Another aspect of the present invention provides an electrical device, comprising the battery or the battery pack as described above.

[0074] The present invention does not limit the specific types of electrical equipment, and may include electric vehicles, mobile phones, smart homes, robots, drones, electronic cigarettes, speakers, and any other equipment that requires batteries to power them.

[0075] The electrical equipment provided by the present invention comprises the above-mentioned battery or battery pack, and thus has good performance.

[0076] The electrolyte provided by the present invention is introduced below through specific embodiments.

[0077] Example 1

[0078] The preparation method of the electrolyte provided in this embodiment comprises the following steps:

[0079] In a glove box filled with argon, 1.0 mol / L lithium hexafluorophosphate (LiPF6) was weighed and dissolved in a mixed solvent with a volume ratio of ethylene carbonate (EC): diethyl carbonate (EMC): dimethyl carbonate (DMC) = 1:1:1 to obtain an electrolyte base liquid, and then triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde were added thereto to obtain an electrolyte, wherein, based on the mass of the electrolyte, the total mass of triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde accounted for 0.5% of the mass percentage of the electrolyte, and the molar ratio of triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde was 1:1; the mass content of lithium hexafluorophosphate was 12.9%, and the mass proportion of the mixed solvent was 86.6%.

[0080] Example 2

[0081] The preparation method of the electrolyte provided in this embodiment is basically the same as that in embodiment 1, except that:

[0082] The total mass percentage of triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde in the electrolyte is 1%; the mass content of lithium hexafluorophosphate is 12.8%; and the mass percentage of the mixed solvent is 86.2%.

[0083] Example 3

[0084] The preparation method of the electrolyte provided in this embodiment is basically the same as that in embodiment 1, except that:

[0085] The total mass percentage of triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde in the electrolyte is 2%; the mass content of lithium hexafluorophosphate is 12.7%; and the mass percentage of the mixed solvent is 85.3%.

[0086] Example 4

[0087] The preparation method of the electrolyte provided in this embodiment is basically the same as that in embodiment 1, except that:

[0088] The total mass of triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde accounts for 5% of the mass percentage of the electrolyte; the mass content of lithium hexafluorophosphate is 12.3%; and the mass percentage of the mixed solvent is 82.7%.

[0089] Example 5

[0090] The preparation method of the electrolyte provided in this embodiment is basically the same as that in embodiment 3, except that:

[0091] The triphenylphosphine ylide Ph3P=CH2 was replaced by cyanomethylenetriphenylphosphine ylide.

[0092] Example 6

[0093] The preparation method of the electrolyte provided in this embodiment is basically the same as that in embodiment 3, except that:

[0094] Benzylaldehyde was replaced by cinnamaldehyde.

[0095] Example 7

[0096] The preparation method of the electrolyte provided in this embodiment is basically the same as that in embodiment 1, except that:

[0097] The molar ratio of triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde is 1.2:1.

[0098] Example 8

[0099] The preparation method of the electrolyte provided in this embodiment is basically the same as that in embodiment 1, except that:

[0100] The total mass of triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde accounts for 8% of the mass percentage of the electrolyte; the mass content of lithium hexafluorophosphate is 12%; and the mass percentage of the mixed solvent is 80%.

[0101] Comparative Example 1

[0102] The preparation method of the electrolyte provided in this comparative example is basically the same as that in Example 1, except that:

[0103] Triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde were not added.

[0104] Comparative Example 2

[0105] The preparation method of the electrolyte provided in this comparative example is basically the same as that in Example 1, except that:

[0106] Triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde were replaced by vinylene carbonate (VC).

[0107] Comparative Example 3

[0108] The preparation method of the electrolyte provided in this comparative example is basically the same as that in Example 1, except that:

[0109] The triphenylphosphine ylide Ph3P=CH2 and benzylaldehyde were replaced by 1,3-propane sultone (PS).

[0110] Comparative Example 4

[0111] The preparation method of the electrolyte provided in this comparative example is basically the same as that in Example 1, except that:

[0112] No triphenylphosphine ylide was added.

[0113] Comparative Example 5

[0114] The preparation method of the electrolyte provided in this comparative example is basically the same as that in Example 1, except that:

[0115] No benzyl aldehyde added.

[0116] Test Case

[0117] The electrolytes provided in all the embodiments and comparative examples are used in sequence to prepare a lithium battery, comprising the following steps:

[0118] 1) Preparation of negative electrode sheets for lithium-ion batteries: Graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose (CMC), and adhesive styrene-butadiene rubber (SBR) are mixed into a slurry at a mass ratio of 50:1:1:1.5, and the slurry is evenly coated on a copper foil as a negative electrode current collector, dried at 85°C under vacuum for 24 hours, and then cold pressed, and then trimmed, cut, and striped, and then dried at 110°C under vacuum for 4 hours, and the tabs are welded to prepare negative electrode sheets for lithium-ion batteries;

[0119] 2) Preparation of positive electrode sheets for lithium-ion batteries: lithium cobalt oxide LiCoO2 (LCO), conductive agent Super P and adhesive PVDF are mixed into a uniform positive electrode slurry at a mass ratio of 50:1:1, and evenly coated on an aluminum foil as a positive electrode current collector, dried at 80°C under vacuum for 24 hours, and then cold pressed, and then trimmed, cut, and striped, and then dried at 110°C under vacuum for 4 hours, and the tabs are welded to make positive electrode sheets for lithium-ion batteries;

[0120] 3) Preparation of soft-pack battery B1: The prepared positive and negative electrodes and separators of the lithium-ion battery are wound to obtain an LCO / graphite soft-pack lithium-ion battery. In an argon glove box with a water content of less than 5 ppm, the prepared electrolyte is injected into the soft-pack battery with an airbag, left to stand for 24 hours, and then a cycle test is performed;

[0121] 4) Preparation of button cell B1: Assemble the prepared negative electrode sheet, lithium sheet, electrolyte and diaphragm into a button cell of model CR2016 for testing the reduction potential of the electrolyte. The oxidation potential test of the electrolyte uses a stainless steel sheet to assemble the lithium sheet into a button half-cell for testing;

[0122] 5) Formation process: The whole battery is first charged to 1.9V at 0.05C current and maintained at 1.9V for 10 hours to fully wet the battery electrode sheet. After the constant voltage is completed, the battery is initially charged at a smaller current of 0.01C for 10 hours to form a stable and dense SEI film, then charged to 4.4V at 0.05C current, and finally discharged to 2.75V.

[0123] (1) Additive reduction and oxidation potential test

[0124] The fresh button cells in the examples and comparative examples were subjected to cyclic voltammetry tests using an Autolab electrochemical workstation, with a scan rate of 0.2 mV / s and a scan range of 0.005 to 3 V. The results are shown in Table 1, where: Figure 1 and Figure 2 The linear sweep voltammetry and cyclic voltammetry test result curves and local magnified diagrams of Example 3 and Comparative Example 1 are shown respectively.

[0125] Table 1

[0126]

[0127] From Table 1, Figure 1 , Figure 2 The results show that the reduction potential of the electrolyte of the present invention to lithium is between 1.37 and 1.45 V, which is higher than the reduction potential of Comparative Examples 1-3 and Comparative Example 5, and the oxidation potential is between 4.01 and 4.05, which is lower than the oxidation potential of Comparative Examples 1 and 2. Therefore, the electrolyte of the present invention can preferentially undergo oxidation and reduction reactions to form SEI / CEI films, thereby further protecting the solvent, reducing the consumption of the solvent, and further reducing the consumption of active lithium, thereby improving the cycle performance of the battery. While the reduction potential of Comparative Example 4 can reach 1.44, the electrolyte provided in the comparative example cannot be oxidized to form a SEI / CEI film, and the cycle performance is poor.

[0128] (2) Battery high temperature cycle test

[0129] The batteries made of the electrolytes provided in the embodiments and comparative examples (10 batteries of each type were selected and the results were averaged) were cycled 200 times at 1C current between 2.75V and 4.4V using a domestic Blue Electric or Xinwei high temperature test cabinet. The high temperature cycle test was carried out in a constant temperature box at 45°C. The capacity retention rate (%) was calculated as the percentage obtained by dividing the discharge capacity at the 200th cycle by the initial discharge capacity at the first cycle. The high temperature cycle test results are shown in Table 2.

[0130] (3) Battery impedance test

[0131] The batteries in the embodiment and comparative example (10 batteries for each condition, the results are averaged) were cycled 120 times at 500mA (1C) between 2.75V and 4.5V. After the batteries were discharged to 2.75V, the AC impedance at -10°C was measured. The above experimental results are shown in Table 2.

[0132] Table 2 High temperature cycle test and low temperature AC impedance test results

[0133]

[0134] As can be seen from Table 2, the battery capacity retention rates of Examples 1-8 are significantly higher than those of the batteries provided in Comparative Examples 1-5, indicating that the electrolyte in the present invention can significantly improve the high-temperature cycle performance of the battery. The battery capacity retention rates of Examples 1, 2, and 5 are significantly lower than those of Examples 3, 4, and 8, indicating that within the experimental range, the increase in the additive content is beneficial to improving the high-temperature cycle performance of the battery. Compared with Comparative Examples 2 and 3, Examples 1, 5, and 6 with the same amount of additives added all show higher cycle retention rates, indicating that the electrolyte including specific structural additives in the present invention is beneficial to improving the cycle performance of the battery.

[0135] As can be seen from Table 2, the impedance of Comparative Examples 2 and 3 is relatively large. VC and PS will increase the low-temperature impedance of the battery while improving the high-temperature cycle performance of the battery. The electrolyte of the present invention has a significant inhibitory effect on the growth of impedance. The impedance of Examples 2 and 5 is the lowest, indicating that the additives of the specific structure in the present invention are conducive to reducing the film formation impedance. The same amount of additives in Examples 1, 5 and 6 are lower than the same amount of additives in Comparative Examples 2 and 3, indicating that the present electrolyte has a lower low-temperature impedance than VC and PS. Although the impedance of the electrolyte provided in Examples 4 and 8 is slightly higher after being used in the battery, the cycle performance of Examples 4 and 8 is excellent, and it can still be considered that the performance is relatively excellent.

[0136] 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, characterized in that: including a first additive and a second additive; The chemical formula of the first additive is shown in Formula 1, and the chemical formula of the second additive is shown in Formula 2: Wherein, R1, R2, R3, and R4 are each independently selected from at least one of H, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted epoxyalkyl, substituted or unsubstituted boroxyalkyl, substituted or unsubstituted aryl, substituted or unsubstituted keto, substituted or unsubstituted ester, and substituted or unsubstituted nitrile.

2. The electrolyte according to claim 1, characterized in that The R1, R2, R3, and R4 are selected from substituted or unsubstituted aryl groups, and the number of carbon atoms of R1, R2, R3, and R4 are each independently selected from 6 to 12; And / or, R1, R2, R3, and R4 are each independently selected from at least one of an alkyl group, a cycloalkyl group, an epoxyalkyl group, a boroxyalkyl group, an aryl group, an alkoxy group, a substituted or unsubstituted keto group, a substituted or unsubstituted ester group, and a substituted or unsubstituted nitrile group, and the number of carbon atoms of R1, R2, R3, and R4 are each independently selected from 6 to 12.

3. The electrolyte according to claim 1 or 2, characterized in that The first additive comprises at least one of triphenylphosphine ylide, cyanomethylene triphenylphosphine ylide, triphenylphosphine methyl ylide, (methoxycarbonylmethylene) triphenylphosphine, (isocyanimino) triphenylphosphine, and allyl triphenylphosphine ylide; And / or, the second additive includes at least one of benzylaldehyde, cinnamaldehyde, phenylethylaldehyde, p-methylcinnamaldehyde, α-hexylcinnamaldehyde, and 2-pentenal.

4. The electrolyte according to any one of claims 1 to 3, characterized in that Based on the mass of the electrolyte, the sum of the mass proportions of the first additive and the second additive is 0.1% to 5%.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The molar ratio of the first additive to the second additive is (0.8-1.2):

1.

6. The electrolyte according to any one of claims 1 to 5, characterized in that Also includes a lithium salt, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethylsulfonyl imide), lithium trifluoromethylsulfonate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium tetrafluoroborate and lithium perchlorate; Based on the mass of the electrolyte, the mass proportion of the lithium salt is 0.1% to 13%.

7. The electrolyte according to any one of claims 1 to 6, characterized in that Also includes a solvent, the solvent is selected from at least one of carbonate solvents, carboxylic acid esters, and ether solvents; Based on the mass of the electrolyte, the mass proportion of the solvent is 10%-90%.

8. A battery, characterized in that: The electrolyte comprising 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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