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KR-102963361-B1 - POSITIVE ELECTRODE AND SECONDARY BATTERY USING THE SAME

KR102963361B1KR 102963361 B1KR102963361 B1KR 102963361B1KR-102963361-B1

Abstract

The present invention relates to a positive electrode and a secondary battery. The positive electrode comprises a positive electrode current collector; A first positive active material layer disposed on the positive current collector and comprising a first positive active material; and a second positive active material layer disposed on the first positive active material layer and comprising a second positive active material; wherein the first positive active material comprises lithium iron phosphate, and the second positive active material comprises lithium iron phosphate and lithium nickel oxide, and the lithium nickel oxide may be a compound of the following chemical formula 2. [Chemical Formula 2] Li 2+a2 Ni x2 M 2 1-x2 O 2+y2 In the above chemical formula 2, M2 is at least one element selected from the group consisting of P, B, C, Al, Sc, Sr, Ti, V, Zr, Mn, Fe, Co, Cu, Zn, Cr, Mg, Nb, Mo, and Cd, and -0.5≤a2≤0.5, 0<x2≤1, 0≤y2<0.3.

Inventors

  • 최정훈
  • 이석우
  • 강용희
  • 장민철
  • 정병효

Assignees

  • 주식회사 엘지에너지솔루션

Dates

Publication Date
20260511
Application Date
20220520

Claims (7)

  1. Positive current collector; A first positive active material layer disposed on the above positive current collector and comprising a first positive active material; and A second positive active material layer disposed on the first positive active material layer and comprising a second positive active material; The above-mentioned first positive active material comprises lithium iron phosphate, and The second positive electrode active material comprises lithium iron phosphate and lithium nickel oxide, and The above lithium nickel oxide is an anode that is a compound of the following chemical formula 2. [Chemical Formula 2] Li 2+a2 Ni x2 M 2 1-x2 O 2+y2 In the above chemical formula 2, M2 is at least one element selected from the group consisting of P, B, C, Al, Sc, Sr, Ti, V, Zr, Mn, Fe, Co, Cu, Zn, Cr, Mg, Nb, Mo, and Cd, and -0.5≤a2≤0.5, 0<x2≤1, 0≤y2<0.3.
  2. In claim 1, A positive electrode characterized in that the first positive electrode active material layer does not contain lithium nickel oxide.
  3. In claim 1, The above lithium iron phosphate is an anode that is a compound of the following chemical formula 1. [Chemical Formula 1] Li 1+a1 Fe 1-x1 M 1 x1 (PO 4-b1 )X b1 (In the above chemical formula 1, M1 is at least one element selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, X comprises one or more elements selected from the group consisting of F, S, and N, and a1, b1, and x1 are each -0.5≤a1≤0.5, 0≤b1≤0.1, and 0≤x1≤0.5.)
  4. In claim 1, In the above second positive active material, A cathode in which the weight ratio of the lithium iron phosphate and the lithium nickel oxide is 90:10 to 95:5.
  5. A secondary battery comprising: the positive electrode of claim 1; and a negative electrode comprising a negative electrode active material.
  6. In claim 5, The above negative electrode active material is a secondary battery containing graphite.
  7. In claim 6, The above negative electrode active material is a secondary battery further comprising SiO X (0≤X<2).

Description

Positive electrode and secondary battery using the same The present invention relates to a cathode comprising lithium iron phosphate and lithium nickel oxide in a second cathode active material layer, and a secondary battery comprising the same. As technology development and demand for electric vehicles and Energy Storage Systems (ESS) increase, the demand for batteries as energy sources is rapidly increasing, and accordingly, various studies are being conducted on batteries that can meet diverse requirements. In particular, research on lithium secondary batteries, which have high energy density and excellent lifespan and cycle characteristics, is actively underway as a power source for these devices. Lithium cobalt oxide (LCO), lithium nickel-cobalt-manganese oxide (LNCMO), and lithium iron phosphate (LFP) are used as cathode active materials for lithium secondary batteries. Lithium iron phosphate is inexpensive because it contains iron, a resource-abundant and low-cost material. Additionally, due to its low toxicity, using lithium iron phosphate can reduce environmental pollution. Furthermore, because lithium iron phosphate possesses an olivine structure, its active material structure can be maintained stably at high temperatures compared to layered lithium transition metal oxides. Consequently, high-temperature stability and high-temperature lifespan characteristics can be improved. However, since lithium iron phosphate has high charge/discharge efficiency, when a cathode containing lithium iron phosphate is used in combination with a negative electrode containing graphite, which has low charge/discharge efficiency, there is a problem of low battery capacity because the discharge capacity of the cathode cannot be fully utilized. In addition, in order to maximize battery capacity, most of the discharge capacity of the negative electrode must be utilized; however, in this case, the potential of the negative electrode may become excessively high, which can lead to excessive decomposition/formation reactions of the SEI layer during battery operation. Consequently, reducing gas is generated within the battery, which leads to a problem of reduced battery life. Therefore, when using a cathode containing lithium iron phosphate, there is a need for a technology that can improve battery capacity, reduce the generation of reducing gases by suppressing the decomposition/formation reaction of the SEI layer, and improve battery life. The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components. Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in a meaning that is commonly understood by those skilled in the art to which the present invention pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terms used herein are for describing the embodiments and are not intended to limit the invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text. As used herein, "comprises" and/or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned. In this specification, when a part is described as including a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. In this specification, the description "A and/or B" means A, or B, or A and B. In this specification, "%" means weight percent unless otherwise explicitly indicated. In this specification, D 50 refers to the particle size corresponding to 50% of the volume accumulation in the particle size distribution curve. The D 50 can be measured, for example, using a laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron region to several millimeters, and can obtain results with high reproducibility and high resolution. In this specification, "specific surface area" is measured by the BET method, and specifically, can be calculated from the amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77K) using BEL SORP-mino II of BEL Japan. In this specification, "weight-average molecular wei