Nickel-Rich Cathode Composition with Core-Shell Stability Control
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Solution Overview
Problem
The development of high-capacity and high-voltage cathode materials for lithium ion batteries is hindered by issues such as Li/Ni mixing, structural degradation, reduced thermal stability, and increased residual alkali, leading to capacity degradation and poor structural stability.
Innovation Solution
A cathode material with a chemical formula of Li n Ni 1-x-y M x Mn y O 2, where 0.9≤n≤1.2, 0<x<1, 0<y<1, and M is Co and/or Al, featuring first particles ≤1.5 µm and second particles ≥2.5 µm, with controlled molar ratios of Ni and Mn elements, and a precursor with specific XRD diffraction peaks, enhancing structural stability and lithium storage sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content is increased in ternary cathode material to improve capacity, then specific capacity is improved, but Li/Ni mixing occurs causing structural degradation and reduced thermal stability
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high nickel content (0.8-1.0) for high capacity, while the shell region has reduced nickel content (0.5-0.8) to prevent Li/Ni mixing and structural degradation. This spatial differentiation of nickel concentration allows the material to simultaneously achieve high specific capacity and maintain structural stability during cycling.
2Reliability
If nickel content is reduced to avoid Li/Ni mixing and structural degradation, then structural stability is improved, but specific capacity and initial efficiency are sacrificed
Solution Approach 1:
The patent segments the cathode material into distinct core and shell regions with different nickel compositions. The core segment provides high capacity through high nickel content, while the shell segment provides structural protection through lower nickel content. This segmentation allows each region to perform its specialized function without compromising the other, achieving both high capacity and structural stability.
3Ease of manufacture
If uniform element distribution is maintained during sintering, then manufacturing simplicity is preserved, but dislocation defects from Li/Ni mixing cannot be effectively reduced
Solution Approach 1:
The patent applies preliminary action by pre-forming the core-shell structure with differentiated nickel distribution before the final sintering process. The oxide precursor is designed with a core region of high nickel content and a shell region of lower nickel content, which is then sintered with lithium salt. This preliminary structuring allows the final product to achieve precise element distribution control without requiring complex in-situ segregation during sintering, thus maintaining manufacturing simplicity while achieving high precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves structural stability, reduces particle collapse, and enhances cycle performance and capacity retention by controlling particle sizes and element distributions, while maintaining high nickel content without lattice defects.
Implementation Method 1
performing primary sintering on a mixture including an oxide precursor of the cathode material, a lithium source and a metal M-containing dopant
Implementation Method 2
the oxide precursor of the cathode material has diffraction peaks both at 34.4° to 36.4° and at 42.3° to 44.3°
Data Source
Figure 1~2a
Figure 2b~2c
Figure 2d~3a
AI summary
A cathode material, a preparation method thereof and a battery provided. The cathode material has a chemical formula of LinNi1-x-yMxMnyO2, where 0.9≤n≤1.2, 0<x<1, 0<y<1, and M is selected from Co and/or Al, the cathode material includes first particles with the maximum diameter of ≤1.5 µm and second particles with the maximum diameter of 22.5 µm, by characterizing the first particles through energy dispersive spectroscopy (EDS), an average value of molar ratios of Ni element and Mn element is denoted as R1, and by characterizing the second particles through energy dispersive spectroscopy (EDS), an average value of molar ratios of Ni element and Mn element is denoted as R2, where 0<R2-R1. Regarding the cathode material, the specific capacity and the initial efficiency performance as well as the structural stability and the cycle performance of the cathode material are effectively improved.