Ni-Rich Cathode Material with Al-Co Gradient for Cycle Stability
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Solution Overview
Problem
Existing Ni-based cathode active materials for lithium secondary batteries suffer from structural instability and performance degradation due to micro-cracks and side reactions, limiting their ability to achieve high energy density and long cycle life.
Innovation Solution
A lithium nickel-based transition metal oxide particle with a concentration gradient region, where the concentrations of aluminum and cobalt atoms change from the surface to the center, and the absolute value of the cobalt atom concentration change exceeds that of aluminum, stabilized by titanium, sodium, and sulfur substitution, ensuring structural stability and high energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni-based cathode active materials are synthesized by co-precipitation method to achieve high reversible capacity, then nickel content can be increased to 50 mol% or more, but micro-cracks form inside secondary particles during long-term charge/discharge cycles leading to performance degradation
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different composition and properties than the core. The surface is enriched with Al and Co while the core maintains high Ni content, providing both high capacity and surface stability to prevent micro-crack formation during cycling.
Solution Approach 2:
The patent uses composite materials by combining multiple transition metals (Ni, Co, Al) in a structured arrangement. The core-shell configuration creates a composite structure where the Ni-rich core provides capacity while the Al-Co enriched shell provides structural stability and prevents degradation.
2Quantity of substance
If electrode density is increased to > 3.3 g/cc to achieve high energy density, then battery energy density improves, but secondary particles collapse inducing side reactions with electrolyte and rapid drop in initial battery life
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different composition and properties than the core. The surface is enriched with Al and Co while the core maintains high Ni content, providing both high capacity and surface stability to prevent micro-crack formation during cycling.
Solution Approach 2:
The patent employs beforehand cushioning by pre-forming a stable surface layer enriched with Al and Co that acts as a protective barrier before the particle is subjected to high density conditions. This surface layer cushions against the mechanical stresses and chemical reactions that would otherwise cause particle collapse and electrolyte degradation.
3Stability of the object's composition
If single-crystal Ni-based cathode active materials are used to prevent particle collapse at high electrode density, then structural stability improves, but structural and thermal instability occurs during electrochemical evaluation due to unstable Ni3+
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the surface region has different composition and properties than the core. The surface is enriched with Al and Co while the core maintains high Ni content, providing both high capacity and surface stability to prevent micro-crack formation during cycling.
Solution Approach 2:
The patent uses intermediary elements (Al and Co) that mediate between the unstable Ni3+ in the core and the electrolyte/environment. These intermediary elements in the surface layer stabilize the structure and prevent direct exposure of unstable Ni3+ to conditions that would cause degradation, while still allowing electrochemical function.
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 cathode active material achieves high energy density and stable cycle life by preventing particle fracture and stabilizing Ni ions, even at high electrode densities, with improved lithium mobility and conductivity.
Implementation Method 1
includes from 400 ppm to less than 1,000 ppm of titanium (Ti) substituted at transition metal sites within a crystal structure
Implementation Method 2
the lithium nickel-based transition metal oxide particle includes a concentration gradient region in which respective concentrations of aluminum (Al) atoms and cobalt (Co) atoms each change from a surface of the particle to a center of the particle
Implementation Method 3
solid-state mixing the lithium nickel-based transition metal oxide precursor compound with a Co precursor compound and an Al precursor compound, and then performing second sintering
Data Source
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AI summary
Provided are a cathode active material, a method of preparing the same, and a secondary battery including the same, the cathode active material including a lithium nickel-based transition metal oxide particle including 96 mol% or more of nickel, not including manganese, including from 400 ppm to less than 1,000 ppm of titanium (Ti) substituted at transition metal sites within a crystal structure, and including a concentration gradient region in which respective concentrations of aluminum (Al) and cobalt (Co) atoms each change from a surface of the particle toward a center of the particle, and wherein, in the concentration gradient region, an absolute value (A) of a slope of the cobalt atom concentration change and an absolute value (B) of a slope of the aluminum atom concentration change satisfy A > B.