Cathode Active Material Structure for Longer Lithium Battery Cycle Life
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Solution Overview
Problem
Conventional cathode active materials for lithium secondary batteries suffer from decreased long-term cycle-life, increased resistance, and unsatisfactory capacity characteristics due to cracks and irreversible reactions during charging and discharging, particularly when nickel content is increased to enhance capacity.
Innovation Solution
A cathode active material comprising secondary particles formed from aggregates of primary particles with a primary particle coefficient greater than or equal to 30 μm−1 and total circumferential length of 200 μm to 450 μm, primary particles sized between 0.1 μm and 1.0 μm, and a radial arrangement structure, along with a specific composition of Lia(Ni1-x-y-zCoxMnyMz)O2, where M is selected from certain elements, to facilitate lithium ion intercalation and deintercalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content is increased to enhance capacity, then capacity characteristics are improved, but cracks are generated and long-term cycle-life is decreased
Solution Approach 1:
The cathode active material is divided into primary particles (0.1-1.0 μm) that aggregate to form secondary particles (5-30 μm). This segmentation allows high nickel content to be distributed in smaller units with radial arrangements, reducing internal stress and crack formation while maintaining high capacity
Solution Approach 2:
The invention uses a composite structure where primary particles with specific crystal orientations aggregate into secondary particles. The composite nature of these aggregated structures provides both high nickel content for capacity and structural integrity for cycle-life
2Ease of manufacture
If conventional cathode active materials are used, then manufacturing is simple, but resistance increases and capacity characteristics are unsatisfactory
Solution Approach 1:
The invention changes critical parameters including primary particle size (0.1-1.0 μm), secondary particle size (5-30 μm), and primary particle coefficient (≥30 μm−1). These parameter changes optimize lithium ion diffusion paths and contact areas, improving capacity characteristics while maintaining manufacturability through controlled aggregation
3Area of stationary object
If primary particle size is reduced to increase surface area, then lithium ion intercalation is facilitated, but particle strength decreases
Solution Approach 1:
Multiple weak primary particles (0.1-1.0 μm) are merged through aggregation to form stronger secondary particles (5-30 μm). The radial arrangement of primary particles within secondary particles creates a robust structure that maintains high surface area for lithium ion intercalation while achieving sufficient particle strength (≥55 MPa)
Solution Approach 2:
The invention transitions from considering only primary particle size to a two-level hierarchical structure. The radial arrangement of primary particles in three-dimensional space within secondary particles provides both high surface area and structural strength that cannot be achieved by primary particle size alone
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 solution provides a cathode active material with improved stability and electrochemical properties, enabling efficient lithium ion utilization, reduced resistance, and enhanced cycle-life characteristics by controlling particle size, contact area, and density without increasing nickel content, thus stabilizing the battery.
Implementation Method 1
easily intercalates/deintercalates lithium ions
Data Source
AI summary
Provided are a cathode active material for a lithium secondary battery, and a cathode and a lithium secondary battery including the same, the cathode active material including secondary particles including an aggregate of two or more primary particles, and a primary particle coefficient is greater than or equal to 30 μm−1 and a total circumferential length of the primary particles is greater than or equal to 220 μm.