CN103165939A - A kind of lithium-ion battery high voltage electrolyte - Google Patents

Abstract

The invention discloses high voltage electrolyte of a lithium ion battery. The high voltage electrolyte of the lithium ion battery comprises lithium salt, organic solvent and additives. The organic solvent is a mixture of chain-shaped carbonic acid ester and ring-shaped carbonic acid ester. The additives are composed of double oxalic acid lithium boric acid (LiBOB) and nitrile solvent. On the basis of adopting nitrile compounds as functional additives, the moderate LiBOB is added. On one hand, the LiBOB serves as a film-forming additive, so that side reactions between the electrolyte and electrodes are reduced. On the other hand, solubility between the nitrile solvent and a negative electrode is improved due to the fact that the LiBOB is added. The high voltage electrolyte of the lithium ion battery is high in conductivity and low in viscosity. Besides, the lithium ion battery using the high voltage electrolyte is better in cycle performance.

Description

A kind of lithium-ion battery high voltage electrolyte

technical field

The invention relates to the field of lithium-ion batteries, in particular to a high-voltage electrolyte for lithium-ion batteries.

Background technique

Lithium-ion batteries have the advantages of high working voltage and specific energy density, good cycle performance, and no memory effect. They are widely used in energy storage batteries for portable devices, and have great potential in new energy vehicle power batteries. Electrolyte is an important part of lithium-ion batteries, which has an important impact on the cycle performance and safety performance of batteries. The currently widely used LiPF ₆ electrolyte system can only guarantee stable use in the range below 4.5V, and as the positive electrode material LiNi _0.5 Mn _1.5 O ₄ under development, its maximum charge cut-off voltage can reach 5.2V. Oxidative decomposition will occur under this condition, resulting in a decrease in battery performance. Therefore, the development of an electrolyte that matches the high-voltage cathode material will help to broaden the application range and market size of lithium-ion batteries.

The high-voltage electrolyte solvent system requires high-voltage resistance, non-toxicity, good solubility for lithium salts, and good compatibility with the positive and negative electrodes of the battery. The use of functional additives is the most cost-effective way to develop high-voltage electrolytes. Nitrile solvents are one of the ideal choices as additives due to their wide electrochemical window and high dielectric constant. Documents J Power Sources (2009,189:576-579) and patent CN102496737A have shown that nitrile compounds can be used as lithium-ion batteries. Solvents or additives have broad application prospects. However, pure nitrile solvents have poor compatibility with low-potential negative electrodes such as graphite or lithium metal of lithium-ion batteries, and polymerization reactions easily occur on the surface of negative electrodes.

Contents of the invention

The present invention aims to provide a high-voltage electrolyte solution for lithium-ion batteries, which includes the following components: lithium salt, organic solvent and additive; the organic solvent is a mixture of chain carbonate and cyclic carbonate; the additive consists of diethyl Composed of lithium borate diacid (LiBOB) and nitrile solvent.

The lithium salt is one or more of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ .

The chain carbonate is one of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and ethylene propyl carbonate (EPC). one or more species.

The cyclic carbonate is one or more of ethylene carbonate (EC) and propylene carbonate (PC).

The nitrile solvent is one or more of succinonitrile, glutaronitrile (GLN), adiponitrile (ADN), and acrylonitrile (ANN).

The lithium salt concentration is 0.8-1.2mol/L.

The volume ratio of the cyclic carbonate to chain carbonate is 1: (1-3).

 The mass ratio of lithium bisoxalate borate (LiBOB) to nitrile solvent is 1:0.8-1.5.

The dosage of the additive is 0.5-5% of the mass of the organic solvent.

Beneficial effects of the present invention:

Because pure nitrile solvents have poor compatibility with low-potential negative electrodes such as graphite or metal lithium of lithium-ion batteries, polymerization reactions easily occur on the surface of the negative electrode, and the polymerized products will prevent the deintercalation of lithium ions. The present invention uses nitrile compounds as On the basis of functional additives, an appropriate amount of LiBOB is added: on the one hand, LiBOB is used as a film-forming additive to reduce the side reaction between the electrolyte and the electrode; on the other hand, the addition of LiBOB can improve the compatibility between the nitrile solvent and the negative electrode. The electrolytic solution of the invention has higher electrical conductivity and lower viscosity, and the lithium ion battery using the electrolytic solution has better cycle performance.

Description of drawings

Figure 1 is a comparison chart of the normal temperature cycle performance of the battery produced in Example 1 of the present invention and the comparative example.

Detailed ways

The present invention will be further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

Example 1

The electrolyte salt of the electrolyte in this example is 1M LiPF ₆ , and the organic solvent is composed of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with a volume ratio of 1:1:1 , the additive is composed of LiBOB and succinonitrile with a mass ratio of 1:0.8, and the amount of the additive is 2% of the mass of the organic solvent. When preparing the above-mentioned lithium-ion battery electrolyte, the above-mentioned organic solvent, lithium salt and additives must be added once in a glove box filled with high-purity argon, and then stirred evenly to obtain the lithium-ion battery electrolyte of the present invention.

The positive electrode active material is made of LiNi _0.5 Mn _1.5 O ₄ , according to the mass ratio of LiNi _0.5 Mn _1.5 O ₄ : conductive agent (SP): binder (PVDF) = 8:1:1, mix well and add a certain amount of NMP Positive electrode slurry is coated, pressed, and cut to make positive electrode sheets, and the lithium sheet is used as the negative electrode. The electrolyte prepared in Example 1 is injected into the CR-2016 button battery in a glove box, and after standing for 4 hours To be tested. The charge-discharge cycle performance test adopts LANDIAN tester, the test current rate is 0.5C, and the charge-discharge voltage range is 3.5-4.9V.

Example 2

The electrolyte salt of the electrolyte in this example is 1M LiPF ₆ , and the organic solvent is composed of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) with a volume ratio of 1:1:1. , the additive is composed of LiBOB and succinonitrile with a mass ratio of 1:1, and the amount of the additive is 3% of the mass of the organic solvent.

The method of preparing lithium-ion battery electrolyte and assembling the button is similar to that of Example 1.

Example 3

The electrolyte salt of the electrolyte in this example is 1.2M LiPF ₆ , and the organic solvent consists of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC) with a volume ratio of 3:1:3:3 ), ethyl methyl carbonate (EMC), the additive consists of LiBOB and glutaronitrile (GLN) with a mass ratio of 1:1, and the amount of the additive is 2.5% of the mass of the organic solvent.

The method of preparing lithium-ion battery electrolyte and assembling button battery is similar to that of Example 1.

Example 4

The electrolyte salt of the electrolyte in this example is 0.8M LiClO ₄ , and the organic solvent is composed of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) with a volume ratio of 2:1:3.5:3.5 ), ethyl methyl carbonate (EMC), the additive is composed of LiBOB and adiponitrile (ADN) with a mass ratio of 1:1.5, and the amount of the additive is 5% of the mass of the organic solvent. The method of preparing lithium-ion battery electrolyte and assembling button battery is similar to that of Example 1.

Comparative example

The electrolyte salt of the electrolyte in this example is 1M LiPF ₆ , and the organic solvent is composed of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) with a volume ratio of 1:1:1 . When preparing the above-mentioned lithium-ion battery electrolyte, the above-mentioned organic solvent and lithium salt must be added once in a glove box filled with high-purity argon, and then stirred evenly to obtain the lithium-ion battery electrolyte of the present invention.

The positive electrode active material is LiNi _0.5 Mn _1.5 O ₄ , weighed according to the mass ratio of LiNi _0.5 Mn _1.5 O ₄ : conductive agent (SP): binder (PVDF) = 8:1:1, mix well, and add a certain amount of NMP Make the positive electrode slurry, make the positive electrode sheet by coating, pressing and slitting, take the lithium sheet as the negative electrode, inject the electrolyte prepared in the comparative proportion, assemble it into a CR-2016 button battery in the glove box, and let it stand for 4 hours to be tested later. The charge-discharge cycle performance test adopts LANDIAN tester, the test current rate is 0.5C, and the charge-discharge voltage range is 3.5-4.9V.

Claims (9)

1. a lithium ion battery high-voltage electrolyte, is characterized in that: comprise following composition: lithium salts, organic solvent and additive; Described organic solvent is the mixture of linear carbonate and cyclic carbonate; Described additive is comprised of biethyl diacid lithium borate (LiBOB) and nitrile solvents.

2. lithium ion battery high-voltage electrolyte according to claim 1, is characterized in that, described lithium salts is LiPF ₆, LiBF ₄, LiClO ₄, LiAsF ₆In one or more.

3. lithium ion battery high-voltage electrolyte according to claim 1, it is characterized in that, described linear carbonate is one or more in dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonic acid ester (EPC).

4. lithium ion battery high-voltage electrolyte according to claim 1, is characterized in that, described cyclic carbonate is one or more in ethylene carbonate (EC) and propene carbonate (PC).

5. lithium ion battery high-voltage electrolyte according to claim 1, is characterized in that, described nitrile solvents is one or more in succinonitrile, glutaronitrile (GLN), adiponitrile (ADN), acrylonitrile (ANN).

6. lithium ion battery high-voltage electrolyte according to claim 1, is characterized in that, described lithium salt is 0.8-1.2mol/L.

7. lithium ion battery high-voltage electrolyte according to claim 1, is characterized in that, the volume ratio of described cyclic carbonate and linear carbonate is 1:(1-3).

8. lithium ion battery high-voltage electrolyte according to claim 1, is characterized in that, the mass ratio 1:0.8-1.5 of described biethyl diacid lithium borate (LiBOB) and nitrile solvents.

9. lithium ion battery high-voltage electrolyte according to claim 1, is characterized in that, the consumption of described additive is the 0.5-5% of organic solvent quality.

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