Search

US-12620574-B2 - Lithium secondary battery

US12620574B2US 12620574 B2US12620574 B2US 12620574B2US-12620574-B2

Abstract

Provided is a lithium secondary battery including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material comprising lithium iron phosphate particles, and the positive electrode has a loading amount of 450 mg/25 cm 2 to 740 mg/25 cm 2 , and the non-aqueous electrolyte includes a lithium salt, an organic solvent, and an additive, wherein the organic solvent includes ethylene carbonate, and dimethyl carbonate, and the dimethyl carbonate is included in 5 vol % to 75 vol % in the organic solvent, and the additive contains vinylene carbonate, and the weight ratio of the vinylene carbonate to the dimethyl carbonate is greater than 0 to 0.2 or less.

Inventors

  • Jun Hyeok HAN
  • Chul Haeng Lee
  • Kyoung Ho AHN
  • Young Ho Oh
  • You Kyeong JEONG
  • Yoon Seok KO

Assignees

  • LG ENERGY SOLUTION, LTD.

Dates

Publication Date
20260505
Application Date
20231103
Priority Date
20221104

Claims (19)

  1. 1 . A lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein: the positive electrode comprises a positive electrode active material, wherein the positive electrode active material comprises lithium iron phosphate particles, and the positive electrode has a loading amount of 500 mg/25 cm 2 to 740 mg/25 cm 2 ; and the non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, wherein the organic solvent comprises a cyclic carbonate-based solvent and a linear carbonate-based solvent, wherein the cyclic carbonate-based solvent comprises ethylene carbonate, and the linear carbonate-based solvent comprises dimethyl carbonate, the additive comprises vinylene carbonate, and the dimethyl carbonate is included in 5 vol % to 75 vol % in the organic solvent, and a weight ratio of the vinylene carbonate to the dimethyl carbonate is greater than 0 to 0.2 or less.
  2. 2 . The lithium secondary battery of claim 1 , wherein the positive electrode has a loading amount of 500 mg/25 cm 2 to 700 mg/25 cm 2 .
  3. 3 . The lithium secondary battery of claim 1 , wherein the positive electrode has a loading amount of 500 mg/25 cm 2 to 600 mg/25 cm 2 .
  4. 4 . The lithium secondary battery of claim 1 , wherein the vinylene carbonate is included in 0.01 wt % to 7 wt % in the non-aqueous electrolyte.
  5. 5 . The lithium secondary battery of claim 1 , wherein a volume ratio of the cyclic carbonate-based solvent to the linear carbonate-based solvent is 10:90 to 50:50.
  6. 6 . The lithium secondary battery of claim 1 , wherein the linear carbonate-based solvent further comprises ethylmethyl carbonate.
  7. 7 . The lithium secondary battery of claim 4 , wherein the organic solvent comprises 10 vol % to 50 vol % of the ethylene carbonate, 5 vol % to 55 vol % of the dimethyl carbonate, and 20 vol % to 70 vol % of the ethylmethyl carbonate.
  8. 8 . The lithium secondary battery of claim 1 , wherein the lithium salt comprises at least one of LiCl, LiBr, LiI, LiBF 4 , LiClO 4 , LiAlO 4 , LiAlCl 4 , LiPF 6 , LiSbF 6 , LiAsF 6 , LiB 10 Cl 10 , LiBOB (LiB(C 2 O 4 ) 2 ), LiCF 3 SO 3 , LiTFSI (LiN(SO 2 CF 3 ) 2 ), LiFSI (LiN(SO 2 F) 2 ), LiCH 3 SO 3 , LiCF 3 CO 2 , LiCH 3 CO 2 , or LiBETI (LiN(SO 2 CF 2 CF 3 ) 2 ).
  9. 9 . The lithium secondary battery of claim 1 , wherein the lithium salt is included in 0.8 M to 3.0 M in the non-aqueous electrolyte.
  10. 10 . The lithium secondary battery of claim 1 , wherein the lithium iron phosphate particles comprise a compound represented by Formula A: Li 1+a Fe 1-s M s (PO 4-b )X b [Formula A] wherein in Formula A, M is one or more elements selected from the group consisting of Co, Ni, Mn, Al, Mg, Ti, and V, and X is F, S, or N, wherein: 0≤s≤0.5; −0.5≤a≤+0.5; and 0≤b≤0.1.
  11. 11 . The lithium secondary battery of claim 1 , wherein the lithium iron phosphate particles comprise LiFePO 4 .
  12. 12 . The lithium secondary battery of claim 1 , wherein: the lithium iron phosphate particles are in the form of a primary particle; and the lithium iron phosphate particles have an average particle size (D 50 ) of 0.2 μm to 3.0 μm.
  13. 13 . The lithium secondary battery of claim 1 , wherein the lithium iron phosphate particles have a carbon coating layer on a surface.
  14. 14 . The lithium secondary battery of claim 1 , wherein the positive electrode active material does not comprise a lithium nickel-based oxide.
  15. 15 . The lithium secondary battery of claim 1 , wherein the negative electrode comprises a carbon-based active material.
  16. 16 . The lithium secondary battery of claim 15 , wherein the carbon-based active material comprises at least one of natural graphite or artificial graphite.
  17. 17 . A method for preparing a lithium secondary battery, the method comprising: preparing an electrode assembly comprising a positive electrode, a negative electrode, and a separator, wherein the positive electrode comprises a positive electrode active material comprising lithium iron phosphate particles, and the positive electrode has a loading amount of 500 mg/25 cm 2 to 740 mg/25 cm 2 ; accommodating the electrode assembly in a battery case; preparing a non-aqueous electrolyte comprising a lithium salt, an organic solvent, and an additive, wherein the organic solvent comprises a cyclic carbonate-based solvent and a linear carbonate-based solvent, the cyclic carbonate-based solvent comprises ethylene carbonate, and the linear carbonate-based solvent comprises dimethyl carbonate, wherein the additive comprises vinylene carbonate, and wherein the dimethyl carbonate is included in 5 vol % to 75 vol % in the organic solvent, and a weight ratio of the vinylene carbonate to the dimethyl carbonate is greater than 0 to 0.2 or less; and injecting or impregnating the non-aqueous electrolyte prepared into the battery case.
  18. 18 . A lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein: the positive electrode comprises a positive electrode active material, wherein the positive electrode active material comprises lithium iron phosphate particles, and the positive electrode has a loading amount of 450 mg/25 cm 2 to 740 mg/25 cm 2 ; and the non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, wherein the organic solvent comprises a cyclic carbonate-based solvent and a linear carbonate-based solvent, wherein the cyclic carbonate-based solvent comprises ethylene carbonate, and the linear carbonate-based solvent comprises dimethyl carbonate, and wherein a volume ratio of the cyclic carbonate-based solvent to the linear carbonate-based solvent is 10:90 to 35:65, the additive comprises vinylene carbonate, and the dimethyl carbonate is included in 5 vol % to 75 vol % in the organic solvent, and a weight ratio of the vinylene carbonate to the dimethyl carbonate is greater than 0 to 0.2 or less.
  19. 19 . A lithium secondary battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein: the positive electrode comprises a positive electrode active material, wherein the positive electrode active material comprises lithium iron phosphate particles, and the positive electrode has a loading amount of 450 mg/25 cm 2 to 740 mg/25 cm 2 ; and the non-aqueous electrolyte comprises a lithium salt, an organic solvent, and an additive, wherein the organic solvent comprises a cyclic carbonate-based solvent and a linear carbonate-based solvent, wherein the cyclic carbonate-based solvent comprises ethylene carbonate, and the linear carbonate-based solvent comprises dimethyl carbonate, and wherein the organic solvent does not comprise propylene carbonate, the additive comprises vinylene carbonate, and the dimethyl carbonate is included in 5 vol % to 75 vol % in the organic solvent, and a weight ratio of the vinylene carbonate to the dimethyl carbonate is greater than 0 to 0.2 or less.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from Korean Patent Application No. 10-2022-0146438 filed on Nov. 4, 2022, the disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates to a lithium secondary battery. Description of the Related Art As personal IT devices and computer networks have been developed due to the development of an information society and the society's reliance on electric energy is increased overall, there is a need for the development of a technology for efficiently storing and utilizing electric energy. A secondary battery is a technology most suitable for various uses among developed technologies, and among these secondary batteries, there is a growing interest in a lithium secondary battery, which can be made small enough to be applied to personal IT devices and the like, and also, has the highest energy density. In general, a lithium secondary battery is manufactured by injecting or impregnating a non-aqueous electrolyte into an electrode assembly composed of a positive electrode, a negative electrode, and a porous separator. A carbon-based active material, a silicon-based active material, or the like is considered as a negative electrode active material of the lithium secondary battery. Meanwhile, the use of a lithium-containing cobalt oxide, LiMnO2 of a layered crystal structure, LiMn2O4 of a spinel crystal structure, a lithium-containing nickel oxide (LiNiO2), or the like is being considered as a positive electrode active material. Recently, the use of a lithium iron phosphate (e.g., LiFePO4)-based active material, which has excellent thermal stability and is relatively inexpensive, has been considered as a positive electrode active material. However, the lithium iron phosphate-based active material has a lower specific capacity than lithium cobalt oxide, lithium nickel oxide, and the like, so that in order to increase the energy density of a positive electrode and a lithium secondary battery including the same, the lithium iron phosphate-based active material should be used in a high loading amount, but a high-loading lithium iron phosphate positive electrode has a problem in that it is difficult for a non-aqueous electrolyte to be sufficiently impregnated into the positive electrode, so that there is a problem in that it is difficult to express capacity, resistance is increased, and lifespan is degraded. BRIEF SUMMARY An aspect of the present invention provides a lithium secondary battery including lithium iron phosphate particles as a positive electrode active material, and a positive electrode having a specific loading amount or greater, wherein the lithium secondary battery has an excellent capacity expression effect, excellent lifespan performance, and a resistance reduction effect by improving negative electrode reduction stability while improving impregnation properties of the positive electrode with respect to the non-aqueous electrolyte. According to an aspect of the present invention, there is provided a lithium secondary battery including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the positive electrode includes a positive electrode active material, wherein the positive electrode active material includes lithium iron phosphate particles, and the positive electrode has a loading amount of 450 mg/25 cm2 to 740 mg/25 cm2, the non-aqueous electrolyte includes a lithium salt, an organic solvent, and an additive, wherein the organic solvent includes a cyclic carbonate-based solvent and a linear carbonate-based solvent, wherein the cyclic carbonate-based solvent contains ethylene carbonate, and the linear carbonate-based solvent contains dimethyl carbonate, and the dimethyl carbonate is included in 5 vol % to 75 vol % in the organic solvent, and the additive contains vinylene carbonate, and the ratio of the weight of the vinylene carbonate to the weight of the dimethyl carbonate is greater than 0 to 0.2 or less. DETAILED DESCRIPTION First, before describing the present invention, it will be understood that terms or words used in the present specification and claims shall not be construed as being limited to having meanings defined in commonly used dictionaries, but should be interpreted as having meanings and concepts consistent with the technical idea of the present invention based on the principle that an inventor may appropriately define concepts of the terms to best explain the invention. Meanwhile, the terms used herein are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. It will be further understood that the terms “include,” “comprise,” or “have” when used in the present specification, specify the presence of stated features, numbers, steps, elements, or combinatio