EP-4738516-A1 - LITHIUM SECONDARY BATTERY

EP4738516A1EP 4738516 A1EP4738516 A1EP 4738516A1EP-4738516-A1

Abstract

A lithium secondary battery according to embodiments of the present invention includes: an electrode assembly including a cathode containing a lithium-transition metal oxide in which a molar ratio of lithium to all metal elements is greater than 1, and an anode disposed opposite the cathode; and an electrolyte solution that impregnates the electrode assembly and includes a fluorine-based additive having a terminal difluorophosphite group (-OPF 2 ). By using the fluorine-based additive, side reactions of the electrolyte solution may be suppressed, and the high-voltage charging stability of the cathode active material may be improved.

Inventors

CHO, IN HAENG
KIM, SEUNG HYUN
PARK, YOUNG UK
KIM, JEONG YUN
SHIM, YU NA
CHO, YONG HYUN

Assignees

SK On Co., Ltd.

Dates

Publication Date: 20260506
Application Date: 20240722

Claims (14)

A lithium secondary battery comprising: an electrode assembly comprising a cathode including a lithium-transition metal oxide in which the molar ratio of lithium to all metal elements is greater than 1, and an anode disposed opposite the cathode; and an electrolyte solution that impregnates the electrode assembly and includes a fluorine-based additive having a terminal difluorophosphite group (-OPF 2 ).
The lithium secondary battery according to claim 1, wherein the fluorine-based additive comprises a compound in which the terminal difluorophosphite group is bonded to a branched saturated hydrocarbon group.
The lithium secondary battery according to claim 2, wherein the fluorine-based additive comprises a compound represented by chemical formula 1 or chemical formula 2 below: (in chemical formulae 1 and 2, R 1 , R 2 , R 3 and R 4 are each independently a C1-C10 alkyl group).
The lithium secondary battery according to claim 3, wherein in chemical formula 1, R 1 is a C4-C10 alkyl group, and R 2 , R 3 and R 4 are each independently a C1-C3 alkyl group.
The lithium secondary battery according to claim 3, wherein the fluorine-based additive comprises a compound represented by chemical formula 1-1 or chemical formula 2-1 below:
The lithium secondary battery according to claim 1, wherein the electrolyte solution further comprises an organic solvent and a lithium salt, and wherein the fluorine-based additive is included in an amount of 0.1% by weight to 5.0% by weight, based on the total weight of the electrolyte solution.
The lithium secondary battery according to claim 6, wherein the fluorine-based additive is included in an amount of 0.5% by weight to 2.0 % by weight, based on the total weight of the electrolyte solution.
The lithium secondary battery according to claim 6, wherein the electrolyte solution further comprises at least one auxiliary additive selected from the group consisting of a cyclic carbonate compound, a fluorine-substituted cyclic carbonate compound, a sultone compound, and a cyclic sulfonate compound.
The lithium secondary battery according to claim 8, wherein the auxiliary additive is included in an amount of 0.01% by weight to 5% by weight, based on the total weight of the electrolyte solution.
The lithium secondary battery according to claim 6, wherein the organic solvent comprises at least one selected from the group consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).
The lithium secondary battery according to claim 1, wherein the molar ratio of lithium to all metal elements in the lithium-transition metal oxide is greater than 1.1.
The lithium secondary battery according to claim 1, wherein the lithium-transition metal oxide further comprises nickel and manganese.
The lithium secondary battery according to claim 12, wherein the molar ratio of manganese in the lithium-transition metal oxide is greater than the molar ratio of nickel.
The lithium secondary battery according to claim 13, wherein the molar fraction of manganese to all elements excluding lithium and oxygen in the lithium-transition metal oxide is 0.5 or more.

Description

[Technical Field] The disclosure of the present application relates to a lithium secondary battery. More specifically, the present disclosure relates to a lithium secondary battery including an electrode assembly and an electrolyte. [Background Art] Secondary batteries are batteries that can be repeatedly charged and discharged. With the development of information and communication and display industries, they have been widely applied as power sources for portable electronic communication devices, such as camcorders, mobile phones, and laptop PCs. In addition, battery packs including secondary batteries have recently been developed and applied as power sources for eco-friendly vehicles, such as electric vehicles. Examples of secondary batteries may include a lithium secondary battery, a nickelcadmium battery, a nickel-hydrogen battery and the like. Among them, the lithium secondary battery has a high operating voltage and a high energy density per unit weight, making it advantageous in terms of charging speed and weight reduction. In this regard, the lithium secondary battery has been actively developed and applied to various industrial fields. For example, the lithium secondary battery may include: an electrode assembly including a cathode, an anode, and a separation membrane (separator); and an electrolyte that impregnates the electrode assembly. The lithium secondary battery may further include, for example, a pouch-type outer case that accommodates the electrode assembly and the electrolyte. As the application scope of lithium secondary batteries expands, demands for longer cycle life, higher capacity, and operational stability are increasing. Accordingly, lithium secondary batteries that provide consistent output and capacity even during repeated charge and discharge cycles are desirable. For example, the chemical composition of a cathode active material may be designed to implement a high-capacity lithium secondary battery. However, the stability of the battery may be deteriorated due to impurities remaining in the cathode active material and side reactions with the electrolyte. Therefore, the electrolyte used in the lithium secondary battery also needs to be manufactured to provide stable operation over a high-capacity, high-voltage charge/discharge range. [Summary of Invention] [Problems to be Solved by Invention] An object of the present disclosure is to provide a lithium secondary battery having improved capacity characteristics and operational stability. [Means for Solving Problems] A lithium secondary battery according to embodiments of the present disclosure includes: an electrode assembly including a cathode containing a lithium-transition metal oxide in which the molar ratio of lithium to all metal elements is greater than 1, and an anode disposed opposite the cathode; and an electrolyte solution that impregnates the electrode assembly and includes a fluorine-based additive having a terminal difluorophosphite group (-OPF2). In some embodiments, the fluorine-based additive may include a compound in which the terminal difluorophosphite group is bonded to a branched saturated hydrocarbon group. In some embodiments, the fluorine-based additive may include a compound represented by chemical formula 1 or chemical formula 2 below. (in chemical formulae 1 and 2, R1, R2, R3 and R4 are each independently a C1-C10 alkyl group). In some embodiments, in chemical formula 1, R1 is a C4-C10 alkyl group, and R2, R3 and R4 may each independently be a C1-C3 alkyl group. In some embodiments, the fluorine-based additive may include a compound represented by chemical formula 1-1 or chemical formula 2-1 below. In some embodiments, the electrolyte solution may further include an organic solvent and a lithium salt, and the fluorine-based additive may be included in an amount of 0.1% by weight to 5.0% by weight, based on the total weight of the electrolyte solution. In some embodiments, the fluorine-based additive may be included in an amount of 0.5% by weight to 2.0 % by weight, based on the total weight of the electrolyte solution. In some embodiments, the electrolyte solution may further include at least one auxiliary additive selected from the group consisting of a cyclic carbonate compound, a fluorine-substituted cyclic carbonate compound, a sultone compound, and a cyclic sulfonate compound. In some embodiments, the auxiliary additive may be included in an amount of 0.01% by weight to 5% by weight, based on the total weight of the electrolyte solution. In some embodiments, the organic solvent may include at least one selected from the group consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). In some embodiments, the molar ratio of lithium to all metal elements in the lithium-transition metal oxide may be greater than 1.1. In some embodiments, the lithium-transition metal oxide may further include nickel and manganese. In some embodiments, t