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EP-4742352-A1 - ELECTROLYTE FOR LITHIUM-SULFUR BATTERY

EP4742352A1EP 4742352 A1EP4742352 A1EP 4742352A1EP-4742352-A1

Abstract

The present disclosure relates to an electrolyte for use in a lithium-sulfur battery, including a non-aqueous solvent, a lithium salt and an additive, wherein the additive includes a nitrate salt and a Li 2 S x -P 2 S 5 composite (1 ≤ x) to improve Coulombic efficiency and life of the lithium-sulfur battery.

Inventors

  • PARK, SO-DAM

Assignees

  • LG Energy Solution, Ltd.

Dates

Publication Date
20260513
Application Date
20241212

Claims (13)

  1. An electrolyte for a lithium-sulfur battery, comprising: a non-aqueous solvent, a lithium salt and an additive, wherein the non-aqueous solvent includes an acyclic ether and a conjugated heterocyclic compound, wherein the lithium salt includes a fluorine-containing compound, wherein the additive includes a nitrate salt and a Li2Sx-P2S5 composite (1≤x), and wherein the Li2Sx-P2S5 composite is included in an amount of 0.1 to 2.5 parts by weight based on total 100 parts by weight of the non-aqueous solvent and the lithium salt.
  2. The electrolyte for the lithium-sulfur battery according to claim 1, wherein the Li2Sx-P2S5 composite includes a composite where 1<x≤8.
  3. The electrolyte for the lithium-sulfur battery according to claim 1, wherein the Li2Sx- P2S5 composite is included in an amount of 0.5 to 1.5 parts by weight based on total 100 parts by weight of the non-aqueous solvent and the lithium salt.
  4. The electrolyte for the lithium-sulfur battery according to claim 1, wherein a molar ratio of the Li2SX and the P2S5 in the Li2Sx-P2S5 composite ranges from 1:1 to 1:5.
  5. The electrolyte for the lithium-sulfur battery according to claim 1, wherein the acyclic ether is included in an amount of 60 vol% or more based on a total volume of the non-aqueous solvent.
  6. The electrolyte for the lithium-sulfur battery according to claim 1, wherein the acyclic ether includes dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, diisobutyl ether, ethyl methyl ether, ethyl propyl ether, ethyl tertbutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, dimethoxypropane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol dimethyl ether, butylene glycol ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, diethylene glycol tertbutyl ethyl ether, ethylene glycol ethyl methyl ether or a mixture thereof, and preferably dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether or a mixture thereof.
  7. The electrolyte for the lithium-sulfur battery according to claim 1, wherein the conjugated heterocyclic compound includes furan, 2-methylfuran, 3-methylfuran, 2-ethylfuran, 2-propylfuran, 2-butylfuran, 2,3-dimethylfuran, 2,4-dimethylfuran, 2,5-dimethylfuran, 2H-pyran, 4H-pyran, 2-methylpyran, 3-methylpyran, 4-methylpyran, benzofuran, 2-(2-nitrovinyl)furan, thiophene, 2-methylthiophene, 2-ethylthiophene, 2-propylthiophene, 2-butylthiophene, 2,3-dimethylthiophene, 2,4-dimethylthiophene, 2,5-dimethylthiophene, benzothiophene or a mixture thereof.
  8. The electrolyte for the lithium-sulfur battery according to claim 1, wherein the fluorine-containing compound includes LiBF4, LiPF6, LiAsF6, LiSbF6, LiN(SO2F)2, LiCF3SO3, LiCF3CO2, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2F)2, LiC(SO2CF3)3 or a mixture thereof.
  9. The electrolyte for the lithium-sulfur battery according to claim 1, wherein a molar concentration of the lithium salt in the non-aqueous solvent and the lithium salt is 1.0 M or less.
  10. A lithium-sulfur battery comprising: the electrolyte for the lithium-sulfur battery according to any one of claims 1 to 9, a positive electrode, a negative electrode, a separator between the negative electrode and the positive electrode and a battery case, wherein the positive electrode includes a sulfur-based compound containing a sulfur (S)-sulfur (S) bond as an active material, and wherein the negative electrode includes a lithium metal layer.
  11. The lithium-sulfur battery according to claim 10, wherein the active material of the positive electrode includes a sulfur-carbon composite in which the sulfur-based compound is loaded onto at least one of an outer surface of a porous carbon material and an inside of pores of the porous carbon material.
  12. The lithium-sulfur battery according to claim 10, wherein the lithium metal layer includes a lithium metal (Li) foil or a lithium alloy foil.
  13. The lithium-sulfur battery according to claim 10, wherein the lithium-sulfur battery includes a coin-type battery, a pouch-type battery or a cylindrical battery.

Description

TECHNICAL FIELD The present disclosure relates to an electrolyte that may be used in a lithium-sulfur battery. This application is based on and claims priority from Korean Patent Application No. 2023-0186235, filed on December 19, 2023, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. BACKGROUND As lithium secondary batteries are used in a wide range of applications including not only portable electronic devices but also electric vehicles (EV) and energy storage systems (ESS), there is an increasing demand for lithium secondary batteries with higher capacity, higher energy density and longer life. Among lithium secondary batteries, lithium-sulfur batteries are a battery system using a sulfur-based material containing a sulfur-sulfur bond as a positive electrode active material, and a lithium metal, a carbon-based material in which intercalation/deintercalation of lithium ions takes place, or silicon or tin that forms an alloy with lithium as a negative electrode active material. In lithium-sulfur batteries, the theoretical specific capacity based on conversion reaction (S8 +16Li+ +1 6e- → 8Li2S) between lithium ions and sulfur in the positive electrode amounts to 1,675 mAh/g, and when lithium metal is used as the negative electrode, the theoretical energy density is 2,600 Wh/kg. Because this value is higher than the theoretical energy density of other battery systems currently being studied (Ni-MH battery: 450 Wh/kg, Li-FeS battery: 480 Wh/kg, Li-MnO2 battery: 1,000 Wh/kg, Na-S battery: 800 Wh/kg) and lithium ion batteries (250 Wh/kg), lithium-sulfur batteries are gaining attention as a high-capacity, eco-friendly and low-cost lithium secondary battery among secondary batteries developed so far. However, during charging of lithium-sulfur batteries, lithium ions may be reduced into lithium metal on solid electrolyte interphase (SEI) surface on the negative electrode to form an uneven surface of the negative electrode, causing uneven resistance distribution. When the process of charging and discharging is repeatedly performed, lithium deposits unevenly to form dendrites and inactive lithium. The dendrites are the major cause of separator damage and short circuits, and in these circumstances, many studies are being made to achieve uniform lithium ion stripping and lithium plating on negative electrode surface of lithium-sulfur batteries. DISCLOSURE Technical Problem To solve the above-described problems, the present disclosure is directed to providing an electrolyte of a new composition for suppressing and preventing the growth of lithium dendrites on a negative electrode. Specifically, the present disclosure is directed to providing an electrolyte of a new composition that is advantageous in forming a solid electrolyte interphase to suppress and prevent the growth of lithium dendrites on negative electrode surface. The present disclosure is further directed to providing a lithium-sulfur battery with improved battery life and Coulombic efficiency. Technical Solution To achieve the above-described objective, according to an aspect of the present disclosure, there is provided an electrolyte for a lithium-sulfur battery of the following embodiments. The electrolyte according to a first embodiment includes: a non-aqueous solvent, a lithium salt and an additive, wherein the non-aqueous solvent includes an acyclic ether and a conjugated heterocyclic compound, wherein the lithium salt includes a fluorine-containing compound, wherein the additive includes a nitrate salt and a Li2Sx-P2S5 composite (1≤x), and wherein the Li2Sx-P2S5 composite is included in an amount of 0.1 to 2.5 parts by weight based on total 100 parts by weight of the non-aqueous solvent and the lithium salt. According to a second embodiment, in the first embodiment, the Li2Sx-P2S5 composite may include a composite where 1<x≤8. According to a third embodiment, in the first or second embodiment, the Li2Sx- P2S5 composite may be included in an amount of 0.5 to 1.5 parts by weight based on total 100 parts by weight of the non-aqueous solvent and the lithium salt. According to a fourth embodiment, in any one of the first to third embodiments, a molar ratio of the Li2SX and the P2S5 in the Li2Sx-P2S5 composite may range from 1:1 to 1:5. According to a fifth embodiment, in any one of the first to fourth embodiments, the acyclic ether may be included in an amount of 60 vol% or more based on a total volume of the non-aqueous solvent. According to a sixth embodiment, in any one of the first to fifth embodiments, the acyclic ether may include dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, diisobutyl ether, ethyl methyl ether, ethyl propyl ether, ethyl tertbutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, dimethoxypropane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glyco