JP-2023550285-A - Positive electrode active material, positive electrode, and lithium secondary battery using the same

JP2023550285AJP 2023550285 AJP2023550285 AJP 2023550285AJP-2023550285-A

Abstract

Inventors

チョンユギョン
グォンヨンファン
シンジョンソン
チェムンホ
チェユンヨン
キムジワン
キムサンヒョク

Assignees

エコプロビーエムカンパニーリミテッド
エコプロビーエムカンパニーリミテッド

Dates

Publication Date: 20231201
Application Date: 20221004
Priority Date: 20211015

Claims (20)

A bimodal type positive electrode active material comprising a first lithium composite oxide as small particles and a second lithium composite oxide as large particles, The first lithium composite oxide and the second lithium composite oxide each independently include at least one unit particle, The number of unit particles constituting the first lithium composite oxide is smaller than that of the second lithium composite oxide, A positive electrode active material, wherein the ratio of the major axis length r1 to the minor axis length r2 of the unit particles constituting the first lithium composite oxide is 1.3 to 2.1.
The first lithium composite oxide exists as a single unit particle in a non-agglomerated form, The positive electrode active material according to claim 1, wherein the second lithium composite oxide exists as secondary particles in the form of agglomerated unit particles.
The positive electrode active material according to claim 1, wherein a lithium ion diffusion path is formed in the unit particles constituting the first lithium composite oxide along the long axis direction of the unit particles.
The major axis length r1 of the unit particle constituting the first lithium composite oxide corresponds to the major axis length of a first crystal plane corresponding to the (003) plane in the crystal structure of the unit particle, The short axis length r2 of the unit particles constituting the first lithium composite oxide corresponds to the short axis length perpendicular to the long axis length r1 of the first crystal plane, The positive electrode active material according to claim 1, wherein a lithium ion diffusion path is formed in the unit particles constituting the first lithium composite oxide along the long axis direction of the first crystal plane.
At least one second crystal plane different from the (003) plane is present in the unit particles constituting the first lithium composite oxide, 5. The positive electrode active material according to claim 4, wherein the lithium ion diffusion path is formed to be oriented toward the second crystal plane.
The positive electrode active material according to claim 5, wherein the second crystal plane includes at least one crystal plane selected from a (012) plane and a (104) plane.
The positive electrode active material according to claim 1, wherein the first lithium composite oxide and the second lithium composite oxide are each independently represented by the following chemical formula 1. [Chemical formula 1] Li w Ni 1-(x+y+z) Co x M1 y M2 z O 2 (here, M1 is at least one selected from Mn and Al, M2 is P, Sr, Ba, B, Ce, Cr, Mn, Mo, Na, Ca, K, Ti, Zr, Al, Hf, Ta, Mg, V, Zn, Si, Y, Sn, Ge, Nb , W and Cu, M1 and M2 are different from each other, 0.5≦w≦1.5, 0≦x≦0.20, 0≦y≦0.20, 0≦z≦0.20. )
8. The positive electrode active material according to claim 7, wherein a molar ratio of nickel to the first lithium composite oxide and the second lithium composite oxide calculated by the following formula 1 is 0.6 or more. [Formula 1] Ni (molar ratio) = Ni (mol%) / (Ni (mol%) + Co (mol%) + M1 (mol%) + M2 (mol%))
The positive electrode active material according to claim 1, wherein the first lithium composite oxide has an average particle size of 2.5 μm to 5.0 μm.
The positive electrode active material according to claim 1, wherein the second lithium composite oxide has an average particle size of 10 μm to 18 μm.
The positive electrode active material according to claim 10, wherein the unit particles constituting the second lithium composite oxide have an average particle size of 0.1 μm to 5.0 μm.
The ratio of the peak intensities attributed to the (003) plane and the (012) plane obtained by X-ray diffraction analysis using Cu-Kα rays on the unit particles constituting the first lithium composite oxide is as follows: The positive electrode active material according to claim 1, which satisfies relational expression 1. [Relational expression 1] 0.090≦I(012)/I(003)≦0.120
The ratio of the peak intensities attributed to the (003) plane and the (104) plane obtained by X-ray diffraction analysis using Cu-Kα rays on the unit particles constituting the first lithium composite oxide is as follows: The positive electrode active material according to claim 1, which satisfies relational expression 2. [Relational expression 2] 0.420≦I(104)/I(003)≦0.540
further comprising a first coating layer that covers at least a portion of the surface of the unit particle constituting the first lithium composite oxide, The cathode active material according to claim 1, wherein the first coating layer includes at least one metal oxide represented by Chemical Formula 2 below. [Chemical formula 2] Lia A b O c (here, A is Ni, Mn, Co, Fe, Cu, Nb, Mo, Ti, Al, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, B, P, Eu, Sm, W, V , Ba, Ta, Sn, Hf, Ce, Gd and Nd, and 0≦a≦10, 0≦b≦8, 2≦c≦15, and a and b are at the same time Not 0. )
15. The positive electrode active material according to claim 14, wherein there is a concentration gradient in which the concentration of the element A of the chemical formula 2 decreases from the surface of the unit particle toward the center of the unit particle.
further comprising a second coating layer that covers at least a portion of the surface of the unit particle constituting the second lithium composite oxide, The positive electrode active material according to claim 1, wherein the second coating layer includes at least one metal oxide represented by Chemical Formula 2 below. [Chemical formula 2] Lia A b O c (here, A is Ni, Mn, Co, Fe, Cu, Nb, Mo, Ti, Al, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, B, P, Eu, Sm, W, V , Ba, Ta, Sn, Hf, Ce, Gd and Nd, and 0≦a≦10, 0≦b≦8, 2≦c≦15, and a and b are at the same time Not 0. )
17. The positive electrode active material according to claim 16, wherein there is a concentration gradient in which the concentration of the element A of the chemical formula 2 decreases from the surface of the unit particle toward the center of the unit particle.
The second lithium composite oxide exists as secondary particles in the form of aggregates of a plurality of unit particles, 16. The metal oxide is present in a diffused state along grain boundaries defined between adjacent unit particles from the surface of the secondary particle toward the center of the secondary particle. The positive electrode active material described in .
In the positive electrode active material, when w1 is the weight percent of the first lithium composite oxide and w2 is the weight percent of the second lithium composite oxide, w2/w1 is 1.5 to 9.0. Item 1. Positive electrode active material according to item 1.
A positive electrode comprising the positive electrode active material according to any one of claims 1 to 19.

Description

The present invention relates to a positive electrode active material and a lithium secondary battery using the same, and more specifically, the present invention relates to a positive electrode active material and a lithium secondary battery using the same. bimodal) type positive electrode active material, which improves lithium ion transport ability by controlling the shape and crystal structure of the small particles contained in the positive electrode active material, and further improves the particle stability of the small particles. The present invention relates to a positive electrode active material, a positive electrode, and a lithium secondary battery using the same, which can alleviate or prevent early deterioration and shortened life of the bimodal type positive electrode active material caused by the small particles by increasing the properties of the positive electrode active material. . Batteries store electricity by using materials capable of electrochemical reactions in the positive and negative electrodes. A typical example of such batteries is a lithium secondary battery that stores electrical energy through the difference in chemical potential when lithium ions are intercalated/deintercalated at the positive and negative electrodes. There is. The lithium secondary battery uses a material capable of reversible intercalation/deintercalation of lithium ions as a positive electrode and negative electrode active material, and an organic electrolyte or a polymer electrolyte is provided between the positive electrode and the negative electrode. Fill and manufacture. Lithium composite oxides are used as positive electrode active materials for lithium secondary batteries, and composite oxides such as LiCoO 2 , LiMn 2 O 4 , LiNiO 2 , and LiMnO 2 are being studied as examples thereof. Among the positive electrode active materials, LiCoO 2 has excellent life characteristics and charge/discharge efficiency, and is most commonly used. However, it is expensive due to resource limitations of cobalt used as a raw material, so it is not competitive in price. It has the disadvantage of having limited power. Lithium manganese oxides such as LiMnO 2 and LiMn 2 O 4 have the advantages of excellent thermal safety and low cost, but have the problems of small capacity and poor high temperature characteristics. In addition, although LiNiO 2 -based positive electrode active materials exhibit battery characteristics of high discharge capacity, they are difficult to synthesize due to the cation mixing problem between Li and transition metals, and as a result, the rate There are major problems with its characteristics. Note that the lithium composite oxide contained in the positive electrode active material undergoes a volume change due to intercalation/deintercalation of lithium ions with respect to the lithium composite oxide during charging and discharging. Usually, lithium composite oxide is in the form of secondary particles, which are agglomerated multiple unit particles (primary particles). When these particles accumulate, cracks may occur within the primary particles and/or secondary particles, or the crystal structure may collapse or change (phase transition). These problems ultimately act as a cause of decreasing the stability and reliability of the positive electrode active material, so it is necessary to reduce the volume change of the lithium composite oxide during charging and discharging, and to minimize the stress generation due to volume change. Various studies are ongoing to prevent particle damage. Furthermore, recently, in order to increase the capacity of lithium secondary batteries, bimodal type positive electrode active materials in which small particles and large particles having different average particle sizes are mixed are often used. When mixing small particles and large particles, by filling the voids between the large particles with small particles with a relatively small average particle size, the accumulation density of lithium composite oxide within a unit volume is improved, and the density of lithium composite oxide per unit volume is increased. can increase the energy density of However, such a bimodal type positive electrode active material contains small particles and large particles with different average particle sizes and particle size distributions, so if the stability of any one of the small particles and large particles decreases, There is a problem in that the bimodal type positive electrode active material may deteriorate prematurely or shorten its lifespan. Korean Patent Publication No. 10-2010-0131921 For convenience, certain terms are defined herein in order to more easily understand the present invention. Unless otherwise defined herein, scientific and technical terms used in the present invention have meanings that are commonly understood by one of ordinary skill in the art. Also, unless the context dictates otherwise, singular terms should be understood to include t