Application of dioxazolone compounds in battery electrolytes

Abstract

The present invention belongs to the technical field of battery electrolyte additives, and proposes a technical solution for the application of dioxazolone compounds in battery electrolytes. The battery electrolyte includes an organic solvent, a lithium salt, and an additive. The additive includes a mass ratio of 1: (0.2-0.5) dioxazolone compounds and an amount of dioxazolone compounds of 2-10% of the mass of the battery electrolyte; the structural formula of the dioxazolone compound is: or R is a methyl, phenyl or fluorine-substituted phenyl, and R1 and R2 are not hydrogen or methyl at the same time. Through the above technical solution, the problem that the battery electrolyte is not resistant to high pressure in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery electrolyte additives and relates to the application of dioxazolone compounds in battery electrolytes. Background Art

[0002] In recent years, people's demand for electronic devices has been increasing. With the continuous development of energy storage technology, people's requirements for lithium-ion high-energy density batteries have also become higher and higher. Commonly used lithium secondary batteries include an anode made of a carbon material that can embed or extract lithium ions, a cathode made of a lithium-containing oxide, and a non-aqueous electrolyte solution prepared by dissolving an appropriate amount of lithium salt in a mixed organic solvent. In order to improve the energy density of lithium-ion batteries, researchers usually use the development of high-capacity, high-working voltage positive electrode materials to solve this problem, such as increasing the working voltage of lithium-cobalt composite oxides and lithium-manganese composite oxides, and developing high-working voltage lithium-nickel-manganese composite oxides. However, the commonly used electrolytes have a higher positive electrode oxidation activity at a voltage higher than 4V, and non-aqueous electrolytes are prone to electrochemical oxidation reactions on the positive electrode surface, thereby generating gas. At the same time, at high voltages, the transition metals in the positive electrode material dissolve and migrate to the negative electrode to consume active lithium, resulting in deterioration of the electrochemical properties of lithium ions and failure, and then a decrease in battery performance. The current solution is to add film-forming additives to the electrolyte to improve the interface stability between the electrolyte and the positive electrode. However, film-forming additives will increase the interface impedance, resulting in reduced lithium ion migration and diffusion kinetics in the battery, thereby causing the storage performance and cycle performance of the lithium-ion battery to decay. Therefore, in-depth research on high-voltage electrolyte additives is needed. Summary of the invention

[0003] The present invention provides a technical solution for applying a dioxazolone compound in a battery electrolyte, thereby solving the problem that the battery electrolyte is not resistant to high voltage in the prior art.

[0004] The technical solution of the present invention is achieved as follows: the use of a dioxazolone compound in a battery electrolyte, the battery electrolyte comprising an organic solvent, a lithium salt, and an additive, the additive comprising a dioxazolone compound and a lithium salt in a mass ratio of 1: (0.2-0.5) The dosage of the dioxazolone compound is 2-10% of the mass of the battery electrolyte; the structural formula of the dioxazolone compound is: R is methyl, phenyl or phenyl substituted with fluorine, and R1 and R2 are not hydrogen or methyl at the same time.

[0005] Furthermore, the battery electrolyte comprises lithium salt, organic solvent and additive in a mass ratio of (15-20):(70-80):(2-10).

[0006] Further, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl trifluoroacetate, ethyl trifluoroacetate, and butyl trifluoroacetate.

[0007] Furthermore, the lithium salt includes one or more of LiPF6, LiBF4, LiSO3CF3, LiClO4, LiN(CF3SO2)2, LiC(CF3SO2)3, LiODCB, and LiBOB.

[0008] The working principle and beneficial effects of the present invention are:

[0009] 1. In the present invention, by designing a battery electrolyte additive, a dioxazolone compound is mixed with The combined use improves the cycle stability of lithium-ion batteries at high voltages above 4.5V, and also improves the high-temperature storage and cycle performance of lithium-ion batteries.

[0010] 2. In the present invention, the dioxazolone compound and The dioxazolone compound is added into the battery electrolyte at a mass ratio of 1:(0.2-0.5), and the amount of the dioxazolone compound is 2-10% of the mass of the battery electrolyte, which can synergistically inhibit the decomposition of the electrolyte, reduce the DC impedance, and improve the high voltage cycle performance. DETAILED DESCRIPTION

[0011] 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.

[0012] Example 1

[0013] The battery electrolyte includes a lithium salt, an organic solvent and a battery electrolyte additive in a mass ratio of 18:80:2. The lithium salt is LiBOB with a concentration of 1 mol / L, the organic solvent is ethylene carbonate and propylene carbonate in a mass ratio of 1:1, and the battery electrolyte additive is The added amount is 2% of the battery electrolyte mass.

[0014] Example 2

[0015] The battery electrolyte includes a lithium salt, an organic solvent and a battery electrolyte additive in a mass ratio of 15:75:10. The lithium salt is LiBF4 with a concentration of 1 mol / L, the organic solvent is γ-butyrolactone and diethyl carbonate in a mass ratio of 1:2, and the battery electrolyte additive is The added amount is 10% of the battery electrolyte mass.

[0016] Example 3

[0017] The battery electrolyte includes a lithium salt, an organic solvent and a battery electrolyte additive in a mass ratio of 20:75:5. The lithium salt is LiN(CF3SO2)2 and LiC(CF3SO2)3 in a mass ratio of 1:2, and the concentration is 1 mol / L. The organic solvent is methyl trifluoroacetate in a mass ratio. The battery electrolyte additive is The added amount is 5% of the battery electrolyte mass.

[0018] Example 4

[0019] The battery electrolyte includes lithium salt, organic solvent and battery electrolyte additive in a mass ratio of 17.5:80:2.5. The lithium salt LiSO3CF3 has a concentration of 1 mol / L, the organic solvent is propyl propionate and ethylene carbonate in a mass ratio of 1:1, and the battery electrolyte additive is The added amount is 2.5% of the battery electrolyte mass.

[0020] Example 5

[0021] The battery electrolyte includes a lithium salt, an organic solvent and a battery electrolyte additive in a mass ratio of 17:80:3. The lithium salt is LiODCB with a concentration of 1 mol / L, the organic solvent is ethyl methyl carbonate, and the battery electrolyte additive is The added amount is 3% of the battery electrolyte mass.

[0022] Example 6

[0023] The battery electrolyte includes a lithium salt, an organic solvent and a battery electrolyte additive in a mass ratio of 19:79:2. The lithium salt is LiPF6 with a concentration of 1 mol / L, the organic solvent is ethylene carbonate and γ-valerolactone in a mass ratio of 2.5:1, and the battery electrolyte additive is The added amount is 2% of the battery electrolyte mass.

[0024] Comparative Example 1

[0025] Compared with Example 1, the only difference is that

[0026] Comparative Example 2

[0027] Compared with Example 1, the only difference is that

[0028] Comparative Example 3

[0029] Compared with Example 1, the only difference is that

[0030] Performance Testing

[0031] Lithium cobalt oxide is used as the positive electrode material, graphite is used for the negative electrode, aluminum foil and copper foil are used for the positive and negative current collectors, and ceramic diaphragms are used to form soft-pack batteries. After injecting the electrolyte, the soft-pack batteries are assembled in the glove box and tested after standing for 8 hours. The electrolyte is prepared by dissolving LiODCB in a mixed solvent of propylene carbonate and γ-butyrolactone in a volume ratio of 2:1 to obtain a 1.0M solution, and the solution is used as the basic electrolyte, and the basic electrolyte is used as the blank group for battery performance comparison.

[0032] 1. High temperature storage performance test of lithium-ion batteries

[0033] At 25°C, the lithium-ion battery is charged at a constant current of 1C to a voltage of 4.4V, then charged at a constant voltage of 4.5V to a current of 0.05C, and then discharged at a constant current of 1C to a voltage of 2.8V. The discharge capacity of the lithium-ion battery at this time is tested and recorded as C0; then the lithium-ion battery is charged at a constant current of 1C to a voltage of 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.05C, and the lithium-ion battery is placed in a constant temperature box at 60°C for 90 and 120 days, and the lithium-ion battery is taken out and discharged at a constant current of 1C to a voltage of 2.8V. The discharge capacity of the lithium-ion battery at this time is tested and recorded as C1. The capacity retention rate (%) of the lithium-ion battery after storage at 60°C for 90 and 120 days = C1 / C0×100%, and the test results are shown in Table 1.

[0034] 2. Room temperature DC resistance (DCR) test of lithium-ion batteries

[0035] The state of charge (SOC) of the lithium-ion battery is adjusted to 50% of the full charge capacity at 25°C, and the battery is left to stand for 2 hours. The voltage of the lithium-ion battery at this time is tested and recorded as U1, and then the battery is discharged at a rate of 0.3C for 10s, and the voltage of the lithium-ion battery after discharge is tested and recorded as U2.

[0135] The DCR of the lithium-ion battery at 25°C = (U1-U2) / I, where I represents the current. The test results are shown in Table 1.

[0036] Table 1

[0037]

[0038] From the test results of Comparative Examples 1-3 and Example 1, it can be seen that only adding Lithium-ion batteries have poor high-temperature storage capacity and high room-temperature DC impedance. The coordinated effect can improve the high-temperature storage capacity of lithium-ion batteries and reduce the DC impedance at room temperature.

[0039] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Application of dioxazolone compounds in battery electrolyte, the battery electrolyte comprising an organic solvent, a lithium salt, and an additive, characterized in that: The additives include a dioxazolone compound and a The dosage of the dioxazolone compound is 2.07-6.67% of the mass of the battery electrolyte; the structural formula of the dioxazolone compound is: R is a phenyl group or a fluorine-substituted phenyl group, R1 is a hydrogen atom, and R2 is a methyl group.

2. The method according to claim 1, characterized in that: The battery electrolyte comprises lithium salt, organic solvent and additive in a mass ratio of (15-20):(70-80):(2-10).

3. The method according to claim 1, characterized in that: The organic solvent includes one or more of ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl trifluoroacetate, ethyl trifluoroacetate, and butyl trifluoroacetate.

4. The method according to claim 1, characterized in that: The lithium salt includes one or more of LiPF6, LiBF4, LiSO3CF3, LiClO4, LiN(CF3SO2)2, LiC(CF3SO2)3, LiODCB, and LiBOB.

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