阅读说明：本技术 一种锂电池电解液及其制备方法和应用 (Lithium battery electrolyte and preparation method and application thereof ) 是由 袁峰 于 2020-05-29 设计创作，主要内容包括：本发明提出了一种锂电池电解液,其特征在于,包括锂盐、乙二醇二丁醚、含氟有机溶剂、耐高低温添加剂、咪唑基离子液体。本发明制得锂电池电解液能形成较为稳定的钝化膜,该层钝化膜随存储时间延长的增长得到抑制,从而显著提高锂电池的存储性能和存储寿命。同时,该电解液具有较低的凝固点和高温不燃烧性,并且同时赋予电解液很强的耐燃能力,同时还能增强电池的快充性能,能够广泛应用于快充性锂电池中。(The invention provides a lithium battery electrolyte which is characterized by comprising lithium salt, ethylene glycol dibutyl ether, a fluorine-containing organic solvent, a high and low temperature resistant additive and an imidazolyl ionic liquid. The electrolyte of the lithium battery prepared by the invention can form a relatively stable passive film, and the passive film of the layer is inhibited from increasing along with the prolonging of the storage time, so that the storage performance and the storage life of the lithium battery are obviously improved. Meanwhile, the electrolyte has lower freezing point and high-temperature incombustibility, and simultaneously gives the electrolyte strong flame resistance, and simultaneously can enhance the quick charge performance of the battery, and can be widely applied to quick charge lithium batteries.)

1. The lithium battery electrolyte is characterized by comprising lithium salt, ethylene glycol dibutyl ether, a fluorine-containing organic solvent, a high and low temperature resistant additive and an imidazolyl ionic liquid.

2. The electrolyte for a lithium battery of claim 1 wherein the lithium salt is LiBF₄And lithium bis (oxalate) borate in a mass ratio of 1: (1-2).

3. The lithium battery electrolyte as claimed in claim 1, wherein the fluorine-containing organic solvent is one or more selected from methyl-nonafluorobutyl ether, sevoflurane, glycidyl ether hexadecafluorononyl ether and octafluoropentyl allyl ether.

4. The electrolyte for the lithium battery as claimed in claim 1, wherein the high and low temperature resistant additives are dihydropyridine, laurone and fluoroethylene carbonate, and the mass ratio of the dihydropyridine to the laurone to the fluoroethylene carbonate is 1: (0.5-2): (3-7).

5. The electrolyte for a lithium battery as claimed in claim 1, wherein the cation in the imidazolyl ionic liquid has the following structure of formula i:

6. the lithium battery electrolyte as claimed in claim 1, wherein the imidazole-based ionic liquid has a BF anion₄ ^-Or PF₆ ^-。

7. A method of manufacturing a lithium battery electrolyte as claimed in any one of claims 1 to 6, characterized in that it comprises the following steps:

s1, respectively connecting high-purity aluminum sheets for the positive electrode and the negative electrode in an anhydrous environment, and connecting a voltage-stabilized power supply for electrolysis for 10-15h to remove water in the imidazolyl ionic liquid and the fluorine-containing organic solvent;

s2, dissolving lithium salt in the imidazolyl ionic liquid obtained in the step S1, and uniformly mixing to obtain a solution A;

s3, adding ethylene glycol dibutyl ether and the high and low temperature resistant additive into the fluorine-containing organic solvent obtained in the step S1, and uniformly mixing to obtain a solution B;

and S4, mixing the solution A and the solution B at the temperature of 30-40 ℃, and homogenizing to obtain the lithium battery electrolyte.

8. The method according to claim 7, wherein the voltage in step S1 is 3-6V.

9. The method as claimed in claim 7, wherein the homogenizing condition in step S4 is 10000-12000r/min for 1-2 min.

10. Use of the lithium battery electrolyte according to claims 1-6 for the preparation of a fast-charging lithium ion battery.

Technical Field

The invention relates to the technical field of electrochemistry, in particular to a lithium battery electrolyte and a preparation method and application thereof.

Background

Lithium ion batteries have witnessed the modern, briskly developed electronic technology and become an essential part of modern ubiquitous portable electronic devices. Lithium electrochemical cells, more commonly referred to as batteries (packs), are widely used in a variety of military and commercial products. Many of these products use high energy and high power batteries. Due in part to the miniaturization of portable electronic devices, it is desirable to develop smaller lithium batteries with increased power capacity and service life

In the lithium batteryIn the cell, after the metal lithium contacts the electrolyte, a passivation layer (SEI film) is formed on the surface of the lithium metal, and the passivation film prevents the metal lithium from further reacting with the electrolyte, so that the lithium battery has low self-discharge rate and long storage life. However, in some cases, such as long-term storage at normal temperature and high-temperature storage, the passive film often grows excessively, which causes severe passivation and high self-discharge rate of the battery, and causes battery failure. In order to improve the storage performance of lithium batteries, common methods such as adding a certain amount of sulfur dioxide SO into the electrolyte₂Or adding transition metal macrocyclic compound, organic polymer additive, anode coating treatment and the like.

In addition, in general, most lithium ion batteries include a polyolefin-based separator, a liquid organic electrolyte (including ethylene carbonate, diethyl carbonate, and dimethyl carbonate), a lithium salt, and positive and negative electrodes. Among them, low thermal stability and flammability of the separator and the electrolyte are generally considered to be the main causes of combustion and explosion of the lithium ion battery.

Therefore, it is necessary to develop a safe and stable electrolyte for improving the storage performance of lithium batteries to meet the needs of modern people.

Disclosure of Invention

The invention aims to provide a lithium battery electrolyte, a preparation method and application thereof, which can form a relatively stable passive film, and the passive film can be inhibited from increasing along with the prolonging of storage time, so that the storage performance and the storage life of a lithium battery are obviously improved.

The technical scheme of the invention is realized as follows:

the invention provides a lithium battery electrolyte, which comprises lithium salt, ethylene glycol dibutyl ether, a fluorine-containing organic solvent, a high and low temperature resistant additive and an imidazolyl ionic liquid.

Further, the feed additive is prepared from the following raw materials in parts by weight: 5-12 parts of lithium salt, 1-3 parts of ethylene glycol dibutyl ether, 30-50 parts of a fluorine-containing organic solvent, 2-5 parts of a high-temperature and low-temperature resistant additive and 10-15 parts of an imidazolyl ionic liquid.

As a further improvement of the invention, the lithium salt is LiBF₄And bis (oxalato) boronic acidLithium in a mass ratio of 1: (1-2).

As a further improvement of the invention, the fluorine-containing organic solvent is one or a mixture of several of methyl-nonafluorobutyl ether, sevoflurane, glycidyl ether hexadecafluorononyl ether and octafluoropentyl allyl ether.

As a further improvement of the invention, the high and low temperature resistant additive is dihydropyridine, laurone and fluoroethylene carbonate, and the mass ratio of the dihydropyridine to the laurone to the fluoroethylene carbonate is 1: (0.5-2): (3-7).

As a further improvement of the invention, the cation in the imidazolyl ionic liquid has the following structure shown in formula I:

as a further improvement of the invention, the anion in the imidazolyl ionic liquid is BF₄ ^-Or PF₆ ^-。

The preparation method of the ionic liquid is shown in the following references: synthesis and application of liuhongxia, xuqu, alkyl imidazole ionic liquid [ J ], journal of chinese medical industry, 2006,37 (9): 644-648.

The method comprises the following specific steps:

reacting N-methylimidazole with N-butyl bromide in N-heptane at 80 ℃ for 18h to obtain [ bmim]Br is added. The latter reacts with ammonium fluoroborate in methanol in equal molar ratio to obtain the product [ bmim]BF₄。

The invention further provides a preparation method of the lithium battery electrolyte, which comprises the following steps:

s1, respectively connecting high-purity aluminum sheets for the positive electrode and the negative electrode in an anhydrous environment, and connecting a voltage-stabilized power supply for electrolysis for 10-15h to remove water in the imidazolyl ionic liquid and the fluorine-containing organic solvent;

s2, dissolving lithium salt in the imidazolyl ionic liquid obtained in the step S1, and uniformly mixing to obtain a solution A;

s3, adding ethylene glycol dibutyl ether and the high and low temperature resistant additive into the fluorine-containing organic solvent obtained in the step S1, and uniformly mixing to obtain a solution B;

and S4, mixing the solution A and the solution B at the temperature of 30-40 ℃, and homogenizing to obtain the lithium battery electrolyte.

As a further improvement of the invention, the voltage in step S1 is 3-6V.

As a further improvement of the invention, the homogenization condition in step S4 is 10000-12000r/min for homogenization for 1-2 min.

The invention further protects the application of the lithium battery electrolyte in the preparation of the fast-charging lithium ion battery.

The invention has the following beneficial effects: the lithium bis (oxalato) borate adopted by the invention has the advantages of low cost, high thermal stability, high safety and stable electrochemical property, and the LiBF is added₄The ionic conductivity can be improved, the stability of the electrolyte and the positive and negative electrode interfaces is improved, and the combination of the electrolyte and the positive and negative electrode interfaces has good conductivity, high and low temperature resistance, low cost, safety and stability and synergistic effect;

the addition of the high and low temperature resistant additive is beneficial to enhancing the compatibility of the electrolyte and the carbon cathode and simultaneously enhancing the interface stability of the electrolyte and the cathode, so that the electrolyte can carry out heavy current discharge at the low temperature of-40 ℃; the interface stability of the lithium ion electrolyte and a negative electrode under the conditions of low temperature and high temperature is obtained through long-term research of an inventor; the electrolyte is ensured to have a lower freezing point and high-temperature incombustibility, and is endowed with strong flame resistance, and the quick charging performance of the battery can be enhanced;

the imidazolyl ionic liquid has the characteristics of high solubility to lithium salt, no combustion, no explosion, difficult oxidation, good thermal stability and the like, and has the advantages of wider liquid range, stronger dissolving capacity, lower vapor pressure, more proper viscosity, higher conductivity, wider electrochemical window and the like when being added into the electrolyte, so that the imidazolyl ionic liquid has wide application prospect. The application of the imidazolyl ionic liquid in the lithium battery can change the composition and structure of a passivation film to form a stable passivation film, the growth of the passivation film is inhibited along with the prolonging of the storage time, and meanwhile, the high-temperature discharge performance of the lithium battery can be obviously improved;

the electrolyte of the lithium battery prepared by the invention can form a relatively stable passive film, and the passive film of the layer is inhibited from increasing along with the prolonging of the storage time, so that the storage performance and the storage life of the lithium battery are obviously improved. Meanwhile, the electrolyte has lower freezing point and high-temperature incombustibility, and simultaneously gives the electrolyte strong flame resistance, and simultaneously can enhance the quick charge performance of the battery, and can be widely applied to quick charge lithium batteries.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

LiBF₄CAS number: 14283-07-9.

Lithium bis (oxalato) borate, CAS No.: 409071-16-5.

Dihydropyridines, CAS number: 1149-23-1.

Laurone, CAS No.: 59227-89-3.

Fluoroethylene carbonate, CAS number: 114435-02-8.

Ethylene glycol dibutyl ether, CAS number: 112-48-1.

Methyl-nonafluorobutyl ether, CAS No.: 163702-07-6. The chemicals are purchased from the national medicine group.

Imidazolyl ionic liquids are all available from Reynolds Biotechnology, Inc., Guangzhou. The preparation method of the ionic liquid is shown in the following references: synthesis and application of liuhongxia, xuqu, alkyl imidazole ionic liquid [ J ], journal of chinese medical industry, 2006,37 (9): 644-648.

The preparation method specifically comprises the following steps:

reacting N-methylimidazole with N-butyl bromide in N-heptane at 80 ℃ for 18h to obtain [ bmim]Br is added. The latter is reacted with ammonium fluoroborate in the same molar ratio in the methanol to obtain the product[bmim]BF₄。

The preparation method specifically comprises the following steps:

reacting N-methylimidazole with N-butyl bromide in N-heptane at 80 ℃ for 18h to obtain [ bmim]Br is added. The latter reacts with potassium hexafluorophosphate in methanol in equal molar ratio to obtain the product bmim]PF₆。