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JP-7856340-B2 - Non-aqueous electrolyte for lithium secondary batteries and lithium secondary batteries containing the same

JP7856340B2JP 7856340 B2JP7856340 B2JP 7856340B2JP-7856340-B2

Inventors

  • ジョン・ウ・オ
  • チュル・ヘン・イ
  • ユ・ハ・アン
  • スン・グク・パク

Assignees

  • エルジー エナジー ソリューション リミテッド

Dates

Publication Date
20260511
Application Date
20221208
Priority Date
20211215

Claims (12)

  1. Lithium salts and Non-aqueous organic solvents, A first additive containing a compound represented by the following chemical formula 1, A second additive containing ethyldi(propa-2-in-1-yl)phosphate (EDP), A third additive comprising a cyclic carbonate compound excluding vinylethylene carbonate (VEC), a compound represented by the following chemical formula 2, or a mixture thereof, Includes, The first and second additives are included in a weight ratio of 1: 5 to 1:30 in a non-aqueous electrolyte for lithium secondary batteries: [Chemical formula 1] In the aforementioned chemical formula 1, R is a substituted or unsubstituted alkylene group having 1 to 3 carbon atoms. R1 to R3 are each independently hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CN. [Chemical formula 2] In the aforementioned chemical formula 2, n is an integer, either 1 or 2.
  2. The R is a substituted or unsubstituted alkylene group having 1 or 2 carbon atoms. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein R1 to R3 are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms.
  3. The compound represented by the aforementioned chemical formula 1 is the compound represented by the following chemical formula 1a, the non-aqueous electrolyte for lithium secondary batteries according to claim 1: [Chemical formula 1a]
  4. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the first additive is present in an amount of 0.05% to 5% by weight based on the total weight of the non-aqueous electrolyte.
  5. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the first additive and the second additive are contained in a weight ratio of 1: 5 to 1:15.
  6. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, wherein the second additive further comprises vinyl ethylene carbonate (VEC).
  7. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the cyclic carbonate compound is vinylene carbonate (VC).
  8. The compound represented by chemical formula 2 is 1,3-propane sultone (PS) or 1,4-butane sultone, as described in claim 1, for a non-aqueous electrolyte for a lithium secondary battery.
  9. The non-aqueous electrolyte for a lithium secondary battery according to claim 1, wherein the third additive is a mixture containing vinylene carbonate (VC) and a compound represented by chemical formula 2.
  10. The non-aqueous electrolyte for lithium secondary batteries according to claim 1, further comprising at least one fourth additive selected from the group consisting of halogen-substituted carbonate compounds, sulfate compounds, phosphate or phosphite compounds, borate compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds.
  11. A lithium secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and a non-aqueous electrolyte for a lithium secondary battery according to any one of claims 1 to 10.
  12. The lithium secondary battery according to claim 11, wherein the positive electrode comprises a positive electrode active material consisting of a lithium transition metal oxide containing lithium and one or more metals selected from cobalt, manganese, nickel, and aluminum.

Description

This application claims priority under Korean Patent Application No. 10-2021-0180099 dated December 15, 2021, and Korean Patent Application No. 10-2022-0169868 dated December 7, 2022, and all content disclosed in the documents of said Korean patent applications is incorporated herein by reference. This invention relates to a non-aqueous electrolyte for lithium secondary batteries containing an additive with excellent decomposition product removal and SEI enhancement effects, and to a lithium secondary battery in which high-temperature durability is improved by including this electrolyte. In recent years, with the development of personal IT devices and computer networks in the information society, society's overall dependence on electrical energy has increased, creating a need for technological development to efficiently store and utilize electrical energy. In particular, as interest in solving environmental problems and realizing a sustainable, circular society has grown, research on lithium-ion rechargeable batteries, which are attracting attention as a clean energy source with low carbon dioxide emissions, is being conducted extensively. Lithium-ion rechargeable batteries can be miniaturized to a degree suitable for personal IT devices, and they have the advantages of high energy density and operating voltage. They are used not only as power sources for laptops and mobile phones, but also as power storage devices and electric vehicle power sources. On the other hand, a lithium-ion secondary battery comprises a positive electrode mainly composed of a lithium-containing transition metal oxide, a negative electrode using a carbonaceous material such as a lithium alloy or graphite, a separator interposed between the positive and negative electrodes, and a non-aqueous electrolyte. The non-aqueous electrolyte is a medium through which Li ions move, and is typically a solution in which an electrolyte such as lithium hexafluoride phosphate ( LiPF6 ) is dissolved in a high dielectric constant organic solvent such as ethylene carbonate or dimethyl carbonate. However, electrolytes such as lithium hexafluoride phosphate ( LiPF6 ) are vulnerable to heat and moisture, and therefore react with moisture present in the cell or undergo thermal decomposition to generate Lewis acids such as PF5 . Such Lewis acids not only cause the decomposition of organic solvents such as ethylene carbonate, but can also erode the passivation film formed at the electrode-electrolyte interface, inducing further decomposition of the electrolyte and the elution of transition metal ions from the positive electrode. The eluted transition metal ions either accelerate gas generation by promoting the decomposition of the electrolyte, or re-deposit onto the positive electrode, increasing its resistance. Furthermore, they migrate to the negative electrode via the electrolyte and then electrodeposit onto it, causing self-discharge of the negative electrode, and leading to additional lithium ion consumption and increased resistance due to the breakdown and regeneration of the SEI (solid electrolyte interface) film. Therefore, there is a need for a non-aqueous electrolyte composition that can improve not only safety but also battery performance, such as high-rate charge-discharge characteristics, by removing by-products (such as HF and PF5 ) generated by the thermal decomposition of lithium salts, forming a stable film on the electrode surface to suppress the dissolution of transition metals, or suppressing the electrodeposition of dissolved transition metal ions onto the negative electrode. The present invention will be described in more detail below. The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention. In this specification, when words such as "includes,""composes,""consistsof," or "has" are used, other parts may be added unless "only" is used. When a component is expressed singularly, it includes cases where it includes multiple components unless otherwise explicitly stated. In this specification, "%" means weight percent unless otherwise explicitly indicated. Furthermore, in this specification, the term "alkylene group" refers to a branched or unbranched divalent unsaturated hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group includes, but is not limited to, methylene, ethylene, propylene, isopropylene, butylene, isobutylene, tert-butylene, pentylene, and 3-pentylene groups, and these may be selectively substituted in other embodiments. Generally, lithium secondary batteries ensure high-temperature storage characteristics by forming a passivation film