High-voltage electrolyte additive, electrolyte and lithium ion battery

Abstract

The invention discloses a high-voltage electrolyte additive, an electrolyte and a lithium ion battery, and belongs to the technical field of lithium ion batteries. The structural general formula of the additive is as follows: # imgabs0 # R1, R2 and R3 are respectively and independently selected from one of substituted or unsubstituted phenyl, substituted or unsubstituted C1-C7 straight chain or branched chain structure alkyl, alkoxy, alkenyl and alkynyl; the structural formula of the additive is as follows: # imgabs0 # R1, R2 and R3 are respectively and independently selected from one of substituted or unsubstituted phenyl, substituted or unsubstituted C1-C7 straight chain or branched chain structure alkyl, alkoxy, alkenyl and alkynyl; and R4 is selected from one of substituted or unsubstituted trimethylsilyl, phenyl, alkyl of C1-C7, alkoxy, alkenyl and alkynyl. When being added into the electrolyte, the composite material can be preferentially oxidized and decomposed with the electrolyte in the charging and discharging process of the lithium ion battery, so that an electrode / electrolyte interfacial film is constructed, the stability of the lithium ion battery is improved, the oxygenolysis of the electrolyte is further inhibited, the interface impedance is effectively reduced, and the cycle performance of the lithium ion battery is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a high-voltage electrolyte additive, an electrolyte and a lithium ion battery. Background Art

[0002] As people's expectations for lithium battery capacity continue to rise, the requirements for its energy density are also increasing. Various portable devices such as smartphones and laptops are required to have longer standby time; other electrical equipment, such as energy storage equipment, power tools and electric vehicles, are also constantly developing lithium batteries with light weight, small size, higher output voltage and higher power density. Therefore, high-voltage and high-energy-density lithium batteries are an important research and development direction for the lithium battery industry.

[0003] However, under high voltage conditions, the performance of lithium batteries will decline in many aspects. Under high pressure, the products formed by the decomposition of the electrolyte adhere to the surface of the material, hindering the migration of lithium ions and causing the battery performance to decline; the gas produced during the oxidation and decomposition of the electrolyte causes the battery to swell, the internal pressure to increase, and the safety performance to decline; the high voltage causes more lithium ions to escape, making the structural stability of the positive electrode material worse, and the side reactions between the surface of the positive electrode material and the electrolyte promote the surface structure phase change, leading to problems such as transition metal dissolution and oxygen loss, accelerating the performance decline of the positive electrode material. Therefore, the matching of the electrolyte is crucial. Summary of the invention

[0004] One of the purposes of the present invention is to provide a high voltage electrolyte additive which decomposes into a film before the electrolyte is oxidized under high voltage conditions, thereby solving the problem of high battery impedance;

[0005] A second object of the present invention is to provide an electrolyte comprising a high voltage electrolyte additive;

[0006] A third object of the present invention is to provide a lithium ion battery.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] In a first aspect, a high voltage electrolyte additive is provided, wherein the general structural formula of the high voltage electrolyte additive is as shown in Formula I:

[0009]

[0010] wherein R1, R2 and R3 are each independently selected from a substituted or unsubstituted phenyl group, a substituted or unsubstituted C1-C7 straight chain or branched chain alkyl group, a substituted or unsubstituted C1-C7 straight chain or branched chain alkoxy group, a substituted or unsubstituted C1-C7 straight chain or branched chain alkenyl group, or a substituted or unsubstituted C1-C7 straight chain or branched chain alkynyl group;

[0011] R4 is selected from a substituted or unsubstituted trimethylsilyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted C1-C7 alkyl group, a substituted or unsubstituted C1-C7 alkoxy group, a substituted or unsubstituted C1-C7 alkenyl group, and a substituted or unsubstituted C1-C7 alkynyl group.

[0012] Furthermore, R4 is one of trimethylsilyl, phenyl, ethyl, and trifluoromethyl.

[0013] In one embodiment, optional high voltage electrolyte additives of formula I include but are not limited to:

[0014]

[0015] In a second aspect, an electrolyte includes an organic solvent, a lithium salt, and the high-voltage electrolyte additive as described above.

[0016] Furthermore, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0017] Furthermore, the organic solvent is one or more combinations of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, and vinylene carbonate.

[0018] Furthermore, in the electrolyte, the mass percentage of lithium salt is 8wt%-20wt%.

[0019] Furthermore, the amount of the high voltage electrolyte additive is 0.1wt%-5wt% of the total mass of the electrolyte.

[0020] In a third aspect, a lithium-ion battery comprises the electrolyte as described above.

[0021] Furthermore, the voltage of the lithium-ion battery is 4.45V.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a high-voltage electrolyte additive, which, when added to the electrolyte, can preferentially undergo oxidative decomposition with the electrolyte during the charge and discharge process of the lithium-ion battery, thereby constructing an electrode / electrolyte interface film, improving the stability of the lithium-ion battery, further inhibiting the oxidative decomposition of the electrolyte, effectively reducing the interface impedance, and improving the cycle performance of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 It is a relationship diagram between the cycle number and capacity retention rate of Li||NCM button batteries prepared with the electrolytes of Example 2 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0027] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0028] Example 1

[0029] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula II;

[0030]

[0031] The electrolyte is prepared by the following steps:

[0032] In an argon atmosphere glove box with moisture and oxygen both less than 0.1ppm, ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1:1 as an organic solvent, lithium hexafluorophosphate (LiPF6) is added thereto to obtain a lithium hexafluorophosphate solution with a mass percentage of 13wt%, and then a high-voltage electrolyte additive shown in (Formula II) is added in an amount of 0.1wt% of the total mass of the lithium hexafluorophosphate solution, and the mixture is mixed evenly to obtain an electrolyte.

[0033] Example 2

[0034] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula II;

[0035] The difference between the electrolyte and Example 1 is that the amount of the high voltage electrolyte additive is 0.5wt% of the total mass of the lithium hexafluorophosphate solution, and the other steps and parameters remain the same.

[0036] Example 3

[0037] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula II;

[0038] The difference between the electrolyte and Example 1 is that the amount of the high voltage electrolyte additive is 1wt% of the total mass of the lithium hexafluorophosphate solution, and the other steps and parameters remain the same.

[0039] Example 4

[0040] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula II;

[0041] The difference between the electrolyte and Example 1 is that the amount of the high voltage electrolyte additive is 2 wt % of the total mass of the lithium hexafluorophosphate solution, and the other steps and parameters remain the same.

[0042] Example 5

[0043] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula II;

[0044] The difference between the electrolyte and Example 1 is that the amount of the high voltage electrolyte additive is 5wt% of the total mass of the lithium hexafluorophosphate solution, and the other steps and parameters remain the same.

[0045] Example 6

[0046] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula III;

[0047]

[0048] The electrolyte is prepared by the following steps:

[0049] In an argon atmosphere glove box with moisture and oxygen both less than 0.1ppm, ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1:1 as an organic solvent, lithium hexafluorophosphate (LiPF6) is added thereto to obtain a lithium hexafluorophosphate solution with a mass percentage of 13wt%, and then a high-voltage electrolyte additive shown in formula III is added in an amount of 0.5wt% of the total mass of the lithium hexafluorophosphate solution, and the mixture is mixed evenly to obtain an electrolyte.

[0050] Example 7

[0051] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula IV;

[0052]

[0053] The electrolyte is prepared by the following steps:

[0054] In an argon atmosphere glove box with moisture and oxygen both less than 0.1ppm, ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1:1 as an organic solvent, lithium hexafluorophosphate (LiPF6) is added thereto to obtain a lithium hexafluorophosphate solution with a mass percentage of 13wt%, and then a high-voltage electrolyte additive shown in formula IV is added in an amount of 0.5wt% of the total mass of the lithium hexafluorophosphate solution, and the mixture is mixed evenly to obtain an electrolyte.

[0055] Example 8

[0056] This embodiment provides an electrolyte, including a high voltage electrolyte additive as shown in Formula V;

[0057]

[0058] The electrolyte is prepared by the following steps:

[0059] In an argon atmosphere glove box with moisture and oxygen both less than 0.1ppm, ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1:1 as an organic solvent, lithium hexafluorophosphate (LiPF6) is added thereto to obtain a lithium hexafluorophosphate solution with a mass percentage of 13wt%, and then a high-voltage electrolyte additive shown in formula V is added in an amount of 0.5wt% of the total mass of the lithium hexafluorophosphate solution, and the mixture is mixed evenly to obtain an electrolyte.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that the high voltage electrolyte additive shown in Formula II is not added.

[0062] Performance Testing:

[0063] Preparation of button half-cell (Li||NCM button cell): The positive electrode of the CR2032 button half-cell adopts a nickel cobalt manganese oxide electrode, the negative electrode adopts a lithium sheet, and the separator adopts Celgard 2400. During the assembly process, the electrolytes in Examples 1 to 8 and Comparative Example 1 are added respectively.

[0064] Electrochemical performance test: The prepared Li||NCM button battery was charged to 4.45V at 0.2C constant current and constant voltage, and discharged to 3.0V at constant current, and the cycle was repeated twice; then the battery was charged to 4.45V at 1C constant current and constant voltage, and discharged to 3.0V at constant current for 100 cycles. After 100 cycles, the capacity retention rate of the battery is shown in Table 1.

[0065] Table 1

[0066]

[0067] The cycle times and capacity retention rates of the Li||NCM button batteries prepared by the electrolytes of Example 2 and Comparative Example 1 are as follows: Figure 1 shown.

[0068] Table 1 and Figure 1 By analyzing the data in, it can be seen that the lithium-ion batteries formed by the high-voltage electrolytes prepared in Examples 1 to 8 have a better capacity retention rate than that of Comparative Example 1.

[0069] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0070] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high voltage electrolyte additive, characterized in that: The general structural formula of the high voltage electrolyte additive is shown in Formula I: wherein R1, R2 and R3 are each independently selected from a substituted or unsubstituted phenyl group, a substituted or unsubstituted C1-C7 straight chain or branched chain alkyl group, a substituted or unsubstituted C1-C7 straight chain or branched chain alkoxy group, a substituted or unsubstituted C1-C7 straight chain or branched chain alkenyl group, or a substituted or unsubstituted C1-C7 straight chain or branched chain alkynyl group; R4 is selected from a substituted or unsubstituted trimethylsilyl group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted C1-C7 alkyl group, a substituted or unsubstituted C1-C7 alkoxy group, a substituted or unsubstituted C1-C7 alkenyl group, and a substituted or unsubstituted C1-C7 alkynyl group.

2. A high voltage electrolyte additive according to claim 1, characterized in that: The R4 is one of trimethylsilyl, phenyl, ethyl and trifluoromethyl.

3. An electrolyte, characterized in that: The invention comprises an organic solvent, a lithium salt and a high voltage electrolyte additive as claimed in any one of claim 1 and claim 2.

4. An electrolyte according to claim 3, characterized in that: The lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

5. An electrolyte according to claim 3, characterized in that: The organic solvent is one or more combinations of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, and vinylene carbonate.

6. An electrolyte according to claim 3, characterized in that: In the electrolyte, the mass percentage of lithium salt is 8wt%-20wt%.

7. An electrolyte according to claim 3, characterized in that: The amount of the high voltage electrolyte additive is 0.1wt%-5wt% of the total mass of the electrolyte.

8. A lithium ion battery, characterized in that: Comprising the electrolyte described in any one of claims 3 to claim 7.

9. A lithium ion battery according to claim 8, characterized in that: The voltage of the lithium ion battery is 4.45V.

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