Nickel Cathode Particle Structure for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Rechargeable lithium batteries face issues with high energy density and lithium ion permeability, leading to dendrite formation and safety risks, particularly during high-rate charging, due to porosity challenges and electrical resistance.
Innovation Solution
A positive active material for lithium batteries with a dense inner structure and protruding portions on the surface, featuring a nickel-based transition metal oxide with specific composition and morphology, enhances lithium ion mobility and structural stability, allowing for high-rate charging without damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If higher porosity is used to increase lithium ion mobility, then lithium ion permeability is improved, but electrical contact surface area decreases and energy density is lowered
Solution Approach 1:
The patent applies local quality by creating distinct regions within the positive electrode particles: a porous outer layer with high porosity (30-70%) for lithium ion mobility, and a dense inner core with low porosity (10-30%) for electrical contact and structural stability. This spatial differentiation of porosity allows each region to optimize its function without compromising the other.
Solution Approach 2:
The patent segments the electrode particle structure into multiple functional zones: an outer porous layer for ion transport and an inner dense core for electrical conductivity and mechanical strength. This segmentation resolves the contradiction by assigning different porosity characteristics to different segments of the same particle.
2Speed
If higher porosity is used to increase lithium ion mobility, then lithium ion permeability is improved, but electrical contact surface area decreases
Solution Approach 1:
The patent creates a core-shell structure where the outer shell has high porosity to facilitate lithium ion diffusion, while the inner core maintains low porosity to preserve electrical contact pathways. The core region acts as a conductive backbone that remains in intimate contact with the conductive agent, while the porous shell provides ion transport channels.
3Productivity
If high charge rate is applied to achieve fast charging, then charging speed is improved, but lithium precipitation and dendrite formation occur
Solution Approach 1:
The patent performs preliminary action by pre-forming a porous outer layer on the electrode particles before the charging process. This porous structure is prepared in advance to provide abundant lithium ion insertion sites and reduce ion transport resistance, thereby preventing lithium precipitation during high-rate charging before it can occur.
Solution Approach 2:
The porous outer layer acts as a cushioning structure that absorbs and distributes the stress of rapid lithium ion insertion during fast charging. This pre-formed porous network prevents localized overvoltage and lithium precipitation by providing multiple pathways for ion distribution, thereby cushioning against dendrite formation.
4Quantity of substance
If dense structure is used to increase energy density, then energy density is improved, but lithium ion permeability decreases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the outer shell has high porosity (30-70%) to facilitate lithium ion diffusion, while the inner core has low porosity (10-30%) to maintain high density and energy storage capacity. This spatial differentiation allows the outer region to optimize ion transport while the inner region optimizes energy density.
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 material improves lithium ion diffusion, enhances energy density, and ensures stable charging performance by suppressing dendrite formation and maintaining structural integrity, thereby supporting high-rate charging capabilities.
Implementation Method 1
the inner portion has a dense structure having a higher density than the outer portion... exhibiting high energy density while having high lithium ion permeability to an inner portion of particles thereof
Data Source
AI summary
Disclosed is a positive active material for a rechargeable lithium battery including secondary particles of a nickel-based transition metal oxide composed of an inner portion and an outer portion, wherein the inner portion has a dense structure having a higher density than the outer portion, the secondary particles of the nickel-based transition metal oxide have a plurality of protruding portions on the surface thereof, and the positive active material has an area ratio of 25% to 30% occupied by the protruding portions calculated by Equation 1 based on a cross-section of the secondary particles of the nickel-based transition metal oxide.