Porous Cathode Active Material for Fast-Charging Li-Ion Batteries
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Solution Overview
Problem
Lithium cobalt composite oxides used in lithium secondary batteries suffer from performance degradation during rapid charging due to unstable crystal structures and high cost, limiting their use in applications like electric vehicles.
Innovation Solution
A method involving the formation of carbon-introduced precursor particles with controlled cavity formation through sintering, creating a lithium transition metal oxide with 5-20% cavity ratio, enhancing surface area and contact with electrolyte solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If lithium cobalt composite oxide is used as positive electrode active material, then high functional voltage and charging efficiency are achieved, but thermal stability deteriorates and cost increases
Solution Approach 1:
The patent uses a composite material structure where lithium cobalt oxide particles are coated with a lithium nickel manganese cobalt oxide layer. This composite structure combines the high voltage and charging efficiency of LiCoO2 with the thermal stability of LiNi0.8Co0.1Mn0.1O2, resolving the contradiction between power and reliability
Solution Approach 2:
The patent applies local quality by creating a core-shell structure where the inner core (LiCoO2) provides high functional voltage and charging efficiency, while the outer shell (LiNi0.8Co0.1Mn0.1O2) provides thermal stability. Each region has different composition and properties optimized for its specific function
2Loss of time
If rapid charging is performed, then charge time is reduced, but performance degradation increases
Solution Approach 1:
The patent introduces porous structures on the particle surfaces of the positive electrode active material. These porous structures increase the surface area and provide more pathways for lithium ion diffusion, enabling rapid charging while reducing concentration gradients that cause performance degradation during fast charging
3Quantity of substance
If particle density is increased, then energy density is improved, but surface area to volume ratio decreases
Solution Approach 1:
The patent creates porous structures on the particle surfaces, which increase the effective surface area without significantly increasing particle volume. This allows maintaining high energy density while providing sufficient surface area for electrolyte contact and lithium ion exchange
Solution Approach 2:
The patent introduces surface roughness and porous structures that add dimensional complexity to the particle surfaces. This transforms smooth spherical particles into particles with increased surface area through crevices, pores, and irregularities, effectively increasing surface area without increasing volume
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 method improves output characteristics and minimizes performance degradation during rapid charging by increasing the surface area of the positive electrode active material, facilitating better electrolyte interaction.
Implementation Method 1
the carbon introduced to the precursor particles is volatilized by the sintering of the third step to form cavities in the positive electrode active material particles
Implementation Method 2
mixing the carbon-introduced precursor particles and a lithium raw material and sintering the mixture at a temperature of 750° C. to 950° C. to prepare positive electrode active material particles
Data Source
AI summary
A positive electrode active material includes a lithium transition metal oxide and the positive electrode active material comprises cavities in a region within a distance of 0.3R or more from a center of the particle when the distance from the center of the particle to the surface is R. The positive electrode active material particles have a cavity ratio of 5-20%.