Nickel-Rich Cathode Particle Structure for Crack-Resistant Cycle Life
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Solution Overview
Problem
Existing lithium nickel-based oxide positive electrode active materials for rechargeable lithium batteries suffer from decreased long-term cycle-life, increased resistance, and unsatisfactory capacity characteristics due to cracking during charging and discharging.
Innovation Solution
A lithium nickel-based composite oxide positive electrode active material is designed with a secondary particle structure where primary particles are radially arranged, featuring an inner portion with irregularly arranged primary particles and pores, and an outer portion with radially arranged primary particles, having a specific aspect ratio distribution to enhance lithium diffusion and mitigate volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium nickel-based oxide is used as positive electrode active material, then high energy density is achieved, but long-term cycle-life decreases and resistance increases due to cracking during charging and discharging
Solution Approach 1:
The positive electrode active material is divided into multiple primary particles that aggregate to form secondary particles. This segmentation reduces the overall volume change during lithium insertion/extraction, minimizing internal stress and preventing cracking that would otherwise reduce cycle-life. The multi-particle structure allows each primary particle to undergo smaller dimensional changes independently.
Solution Approach 2:
Different regions of the secondary particle structure are designed with different properties: the inner portion contains irregularly arranged primary particles for high capacity, while the outer portion contains radially arranged plate-shaped primary particles for structural stability and stress resistance. This local differentiation allows the material to simultaneously achieve high energy density and improved cycle-life.
2Use of energy by moving object
If lithium nickel-based oxide is used as positive electrode active material, then high energy density is achieved, but capacity characteristics do not reach satisfactory level
Solution Approach 1:
The inner portion of the secondary particle contains primary particles with higher nickel content for high capacity, while the outer portion has radially arranged plate-shaped particles for structural stability. This local quality differentiation enables the material to achieve both high capacity characteristics and satisfactory performance.
Solution Approach 2:
The positive electrode active material uses a composite structure combining different types of lithium nickel-based oxide particles with varying shapes and arrangements. This composite approach allows optimization of both capacity characteristics and structural stability, achieving satisfactory overall performance.
3Reliability
If primary particles are radially arranged in outer portion of secondary particle, then stress resistance and cycle-life are improved, but manufacturing complexity increases
Solution Approach 1:
The secondary particle is segmented into an inner portion with irregular arrangement and an outer portion with radial arrangement. This segmentation allows the complex radial structure to be confined to only the outer region, reducing overall manufacturing complexity while still providing the stress resistance benefits.
Solution Approach 2:
The radial arrangement of primary particles is applied locally only to the outer portion of the secondary particle, rather than throughout the entire structure. This localized application reduces manufacturing complexity compared to a fully radial structure, while still providing sufficient stress resistance and cycle-life improvement.
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 structured active material achieves high initial charge/discharge efficiency, improved room-temperature and high-temperature cycle-life characteristics, and increased capacity by minimizing stress and resistance during charge-discharge cycles.
Implementation Method 1
at least a portion of the primary particles are radially arranged in the outer portion, a number ratio of the primary particles having an aspect ratio of greater than or equal to about 4 in the outer portion of the secondary particle is greater than or equal to about 18%
Implementation Method 2
heat-treating a mixture of a positive electrode active material precursor including a nickel-based composite hydroxide and a lithium raw material, wherein the heat-treating includes a temperature-raising process and a temperature-maintaining process
Data Source
AI summary
Provided are a positive electrode active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery including the same. The positive electrode active material for a rechargeable lithium battery includes a lithium nickel-based composite oxide, wherein the positive electrode active material is in a form of a secondary particle in which a plurality of primary particles are aggregated together and at least a portion of the primary particles are radially arranged, the secondary particle includes an inner portion and an outer portion, the inner portion of the secondary particle is a region from a center of the secondary particle to 50±5 length % of the total distance from the center to the surface of the secondary particle, and is a region in which primary particles and pores are irregularly arranged.