Cobalt-Free Cathode Composition Balancing Capacity and Cycle Life
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Solution Overview
Problem
The demand for high-capacity rechargeable lithium batteries is increasing, but cobalt-free positive active materials face challenges in maintaining structural stability and achieving long cycle-life characteristics due to the depletion of cobalt, a rare and expensive metal, and the trade-off between capacity, efficiency, and cycle-life in layered cobalt-free materials.
Innovation Solution
A layered cobalt-free positive active material comprising a combination of first and second lithium nickel-based composite oxides with specific particle sizes and nickel concentrations, where the first material has an average particle diameter of 8-20 µm and the second material has an average particle diameter of 1-7 µm, with a higher nickel molar content, is used to balance lithium migration rates and structural stability, thereby enhancing capacity, efficiency, and cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cobalt-free positive active materials with layered structure are used to increase lithium content and capacity, then capacity and efficiency characteristics are improved, but structural stability deteriorates and cycle-life characteristics worsen
Solution Approach 1:
The patent applies composite materials by combining layered cobalt-free lithium nickel-based composite oxide with high lithium content (for capacity) with olivine-based or spinel cobalt-free lithium nickel-based composite oxide (for structural stability). This composite structure allows the battery to achieve both high capacity and long cycle-life by leveraging the advantages of different crystal structures.
2Ease of manufacture
If cobalt is removed from positive active materials to reduce cost and increase availability, then manufacturing cost decreases and material availability improves, but structural defects increase and performance deteriorates
Solution Approach 1:
The patent uses composite materials combining layered structure (for capacity) with olivine-based or spinel structure (for stability) to compensate for the structural defects caused by cobalt removal, thereby maintaining performance while achieving cost reduction and increased material availability.
Solution Approach 2:
The patent changes the crystal structure parameters and composition ratios of the composite oxide materials to optimize the balance between capacity and stability. By adjusting the lithium content, nickel content, and crystal structure type, the patent achieves high performance without cobalt.
3Use of energy by moving object
If layered cobalt-free positive active material with high lithium content is used to achieve high capacity, then energy density increases, but structural deterioration during charging and discharging increases and cycle-life decreases
Solution Approach 1:
The patent combines layered cobalt-free lithium nickel-based composite oxide (providing high lithium content and energy density) with olivine-based or spinel cobalt-free lithium nickel-based composite oxide (providing structural stability during cycling). This composite approach enables the battery to achieve both high energy density and long cycle-life by distributing the functional requirements across different material phases.
Data Source
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AI summary
Disclosed are a positive active material for a rechargeable lithium battery, and a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same, the positive active material including a first positive active material including a layered cobalt-free lithium nickel-based composite oxide, being in a form of secondary particles in which a plurality of primary particles are aggregated, and having an average particle diameter (D50) of about 8 µm to about 20 µm; and a second positive active material including a layered cobalt-free lithium nickel-based composite oxide, being in a form of single particles, and having an average particle diameter (D50) of about 1 µm to about 7 µm, wherein a molar content of nickel based on the total elements excluding lithium and oxygen in the second positive active material is about 1 mol% to about 10 mol% more than a molar content of nickel based on the total elements excluding lithium and oxygen in the first positive active material.