US-20260128375-A1 - ELECTROLYTE ADDITIVE FOR SECONDARY BATTERY, NON-AQUEOUS ELECTROLYTE FOR LITHIUM SECONDARY BATTERY INCLUDING SAME AND LITHIUM SECONDARY BATTERY INCLUDING SAME

US20260128375A1US 20260128375 A1US20260128375 A1US 20260128375A1US-20260128375-A1

Abstract

The present invention relates to a novel electrolyte additive, a non-aqueous electrolyte for a lithium secondary battery comprising the novel electrolyte additive, and a lithium secondary battery comprising the non-aqueous electrolyte. More specifically, the present invention relates to a non-aqueous electrolyte for a lithium secondary battery comprising an additive capable of forming a stable film on an electrode surface. The present invention also relates to a lithium secondary battery comprising such a non-aqueous electrolyte, thereby, a high temperature lifespan of the lithium secondary battery is not deteriorated, resistance does not increase when the lithium secondary battery is stored at a high temperature, and expansion of a volume (thickness) of the lithium secondary battery is suppressed when the lithium secondary battery is stored at a high temperature.

Inventors

Jung Woo Park
Ji Hoon Yang
Jeong Hun PARK
Sun Hwa Lee
Su Wan LEE

Assignees

DUKSAN ELECTERA CO., LTD.

Dates

Publication Date: 20260507
Application Date: 20251231
Priority Date: 20230707

Claims (8)

1 . A non-aqueous electrolyte for a lithium secondary battery comprising: an additive, an additional additive, a lithium salt, and a non-aqueous organic solvent, wherein the additive is a compound containing a imidazole group and a benzene ring.
2 . The non-aqueous electrolyte for a lithium secondary battery according to claim 1 , wherein the additive is a compound represented by chemical formula 1 below.
3 . The non-aqueous electrolyte for a lithium secondary battery according to claim 1 , wherein the additive is included in an amount of 0.05% to 20% by weight based on the total weight of the non-aqueous electrolyte for a lithium secondary battery.
4 . The non-aqueous electrolyte for a lithium secondary battery according to claim 1 , wherein the additional additive is one or more selected from the group composed of a halogen-substituted or unsubstituted carbonate-based compound, a nitrile-based compound, a borate-based compound, a lithium salt-based compound, a phosphate-based compound, a sulfite-based compound, a sulfone-based compound, a sulfate-based compound, and a sultone-based compound.
5 . A lithium secondary battery comprising: the non-aqueous electrolyte for a lithium secondary battery according to claim 1 , a positive electrode, a negative electrode, and a separator.
6 . The lithium secondary battery according to claim 5 , wherein the negative electrode comprises a carbon-based negative electrode active material and a silicon-based negative electrode active material.
7 . The lithium secondary battery according to claim 6 , wherein the carbon-based negative electrode active material and the silicon-based negative electrode active material are comprised in a weight ratio of 97:3 to 50:50.
8 . The lithium secondary battery according to claim 7 , wherein the carbon-based negative electrode active material and the silicon-based negative electrode active material are comprised in a weight ratio of 90:10 to 60:40.

Description

TECHNICAL FIELD The present invention relates to an electrolyte additive for a secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte additive with excellent effectiveness in removing decomposition products generated from lithium salts, and a non-aqueous electrolyte for a lithium secondary battery including the additive. The present invention relates to a non-aqueous electrolyte additive capable of forming a firm solid electrolyte interphase (SEI) on the surface of a negative electrode, and a non-aqueous electrolyte for a lithium secondary battery including the additive. The present invention also relates to a lithium secondary battery including the non-aqueous electrolyte. The high-temperature performance of the lithium secondary battery of the present invention is improved by including the non-aqueous electrolyte. BACKGROUND ART Lithium secondary batteries are used not only as portable power sources for mobile phones, notebook computers, etc., but are also expanding their applications to medium and large power sources for electric bicycles, electric vehicles (EV), and the like. With the expansion of such application fields, there is a demand for a lithium secondary battery capable of maintaining excellent performance not only at room temperature but also in harsher external environments such as high or low temperature environments. Lithium secondary batteries that are currently widely used include, in general, a carbon-based negative electrode capable of intercalating and deintercalating lithium ions, a transition metal oxide-based positive electrode containing lithium, a non-aqueous electrolyte in which lithium salt is dissolved in a mixed carbonate-based organic solvent, and a separator that prevents contact between the positive electrode and the negative electrode. In a lithium secondary battery, during charging, lithium atoms in the positive electrode are ionized into lithium ions and electrons, and the electrons move to the negative electrode through an external circuit and the lithium ions cross the non-aqueous electrolyte and the separator to move to the negative electrode part and are inserted into the carbon negative electrode. During discharging, the electrons move to the positive electrode through the external circuit, and at the same time, the lithium ions are deintercalated from the carbon negative electrode and cross the non-aqueous electrolyte and the separator to move to the positive electrode. The lithium ions and the electrons meet at the positive electrode to form lithium atoms in a stable state. A lithium secondary battery generates electrical energy while repeating such charging and discharging. In a lithium secondary battery, metal ions are eluted from the surface of the positive electrode as the positive electrode active material is structurally destroyed during charging and discharging. The metal ions eluted from the positive electrode are electrodeposited on the negative electrode and deteriorate the negative electrode. The deterioration of the negative electrode tends to be further accelerated when the potential of the positive electrode is high or the secondary battery is exposed to high temperature. In order to solve this problem, a method of adding compounds capable of forming a film, that is, a solid electrolyte interphase (SEI) on the surface of the negative electrode to the non-aqueous electrolyte has been proposed. However, the addition of these electrolyte additives may cause other side effects such as deterioration in lifespan performance of the secondary battery and deterioration in high-temperature stability of the secondary battery. Thus, another problem arises in that overall performance of the lithium secondary battery is reduced. As a lithium salt of a lithium secondary battery, LiPF6 is mainly used to realize suitable characteristics of a secondary battery. It is known that the PF6− anion of LiPF6 is very vulnerable to heat and is thermally decomposed when the secondary battery is exposed to high temperature to generate Lewis acid such as PF5. PF5 thus generated not only causes decomposition of organic solvents such as ethylene carbonate, but also generates hydrofluoric acid (HF) to accelerate the elution of transition metals from the positive electrode active material. The transition metal thus eluted electrodeposited on the positive electrode and causes an increase in the resistance of the positive electrode, is electrodeposited on the negative electrode and causes self-discharge of the negative electrode, or destroys the solid electrolyte interphase (SEI) on the negative electrode, thereby further decomposes the electrolyte. This causes an increase in the resistance of the secondary battery and deterioration in its lifespan. This decomposition reaction of the electrolyte also causes gas to be generated inside the secondary battery. For this reason, when the lithium secondary battery is stored at high temperatures in a f