Positive Electrode Active Material for Dense High-Capacity Li-Ion Cathodes
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Solution Overview
Problem
Current lithium secondary batteries face challenges in achieving high energy density, stability at high temperatures, and cost-effectiveness due to issues with nickel-based and cobalt-based active materials, including low mixture density, high manufacturing costs, and brittleness, which affect capacity and safety.
Innovation Solution
A positive electrode active material comprising a combination of lithium cobalt-based and lithium nickel cobalt-based materials, where the lithium cobalt-based material has a larger particle size and content, and the lithium nickel cobalt-based material is a one-body active material with a smaller particle size, improving mixture density and stability, and reducing gas generation and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-based active material is utilized, then high intrinsic capacity is achieved, but mixture density becomes difficult to achieve due to large average particle diameter and hard spherical shape
Solution Approach 1:
The patent uses a composite material system consisting of lithium cobalt oxide particles (first particles) and lithium nickel cobalt oxide particles (second particles). The lithium cobalt oxide provides high intrinsic capacity while the lithium nickel cobalt oxide with smaller particle size improves packing density. This composite approach allows the positive electrode to achieve both high capacity and suitable mixture density by combining materials with complementary properties.
2Ease of manufacture
If cobalt-based positive electrode active material is used, then manufacturing cost is high, but reduced manufacturing costs are desired
Solution Approach 1:
The patent applies local quality by using different materials in different proportions within the composite. The lithium nickel cobalt oxide (which has lower cost than pure cobalt-based materials) constitutes 30-80 wt% of the mixture, while lithium cobalt oxide (higher cost but higher capacity) makes up 20-70 wt%. This localized distribution of materials with different cost-capacity characteristics allows optimization of both manufacturing cost and capacity.
3Manufacturing precision
If lithium nickel cobalt-based active material with smaller particle size is used, then mixture density is improved, but particle brittleness increases
Solution Approach 1:
The patent creates a composite where smaller lithium nickel cobalt oxide particles (3-10 μm) are combined with larger lithium cobalt oxide particles (10-20 μm). The smaller particles improve mixture density and packing efficiency, while the larger, more robust lithium cobalt oxide particles provide structural strength and reduce overall brittleness. The composite structure balances the weaknesses of each individual material.
Data Source
AI summary
A lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode, and an electrolyte located therebetween. The positive electrode active material includes a lithium cobalt-based active material and a lithium nickel cobalt-based active material, wherein the lithium cobalt-based active material is larger in size and amount than the lithium nickel cobalt-based active material, and the lithium nickel cobalt-based active material is a one-body positive electrode active material.