Core-Shell Lithium Nickel Oxide Particles for Battery Stability
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Solution Overview
Problem
Current lithium secondary batteries face challenges with low structural stability, capacity, and high-temperature performance due to the instability of lithium-nickel-based oxides like LiNiO2, and lithium-nickel-manganese-cobalt-based oxides have inferior rate capability and lifespan characteristics at high temperatures.
Innovation Solution
A positive electrode active material comprising two types of lithium-nickel oxide particles with different sizes and strengths, where the first particle has an average size of 8-20 μm and a strength of 100-250 MPa, and the second particle has an average size of 8 μm or less and a strength of 50-100 MPa, with a specific composition and concentration gradient to enhance structural stability and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-nickel-based oxide (LiNiO2) is used as positive electrode active material, then discharge capacity is improved, but structural stability deteriorates
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core region and outer shell region have different compositions. The core contains LiNiO2 with high nickel content for high capacity, while the shell has modified composition with reduced nickel content and added elements (such as Li1-x-y-zNixCoyMnzO2 or Li1-x-y-zNixCoyMn1-w-zO2) to provide structural stability. This spatial differentiation of material properties resolves the contradiction between high capacity and structural stability.
Solution Approach 2:
The patent uses composite materials by combining LiNiO2 core with a shell layer of lithium-nickel-manganese-cobalt oxide or similar compounds. This composite structure allows the inner core to provide high discharge capacity while the outer shell provides structural stability and resistance to phase transformation during charging-discharging cycles, thereby resolving the contradiction between capacity and stability.
2Quantity of substance
If lithium-nickel-manganese-cobalt-based oxide Li(NixCoyMnz)O2 is used, then capacity and voltage are improved, but rate capability and lifespan characteristic at high temperature deteriorate
Solution Approach 1:
The patent applies local quality by designing a core-shell structure where the core region uses Li(NixCoyMnz)O2 for high capacity and voltage, while the shell region uses a different composition (such as Li1-x-y-zNixCoyMnzO2 with optimized ratios or LiMn2O4 spinel structure) that provides better thermal stability and lifespan characteristics. This localized differentiation allows the battery to achieve both high capacity and improved reliability at high temperatures.
3Stability of the object's composition
If cobalt is added to LiNiO2 to stabilize structure, then structural stability is improved, but capacity decreases
Solution Approach 1:
The patent applies local quality by concentrating the cobalt addition in the outer shell region rather than uniformly throughout the material. The core maintains high nickel content (0.8 ≤ x ≤ 1.0 in Li1-x-y-zNixCoyMnzO2) for high capacity, while the shell has reduced nickel content and added cobalt (0 < y ≤ 0.2) to provide structural stability. This spatial separation allows the material to achieve both high capacity and structural stability without the capacity loss associated with uniform cobalt doping.
Data Source
AI summary
The present invention provides a positive electrode active material for a secondary battery, a positive electrode for a secondary battery, and a secondary battery including the same, the positive electrode active material including a first lithium-nickel oxide particle having an average particle size (D50) of more than 8 μm to 20 μm or less, and a second lithium-nickel oxide particle having an average particle size (D50) of 8 μm or less, wherein the first lithium-nickel oxide particle has a particle strength of 100 MPa to 250 MPa, the second lithium-nickel oxide particle has a particle strength of 50 MPa to 100 MPa, a ratio r of the strength of the first lithium-nickel oxide particle to the strength of the second lithium-nickel oxide particle satisfies Equation 1 set forth herein.