Zirconium-Coated Cathode Particles for Longer Li-Ion Cycle Life
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Solution Overview
Problem
Existing positive active materials for rechargeable lithium batteries, such as lithium nickel-based oxides, suffer from structure collapse and cracking during repeated charges and discharges, leading to deteriorated long-term cycle-life and increased resistance, which limits their capacity and energy density.
Innovation Solution
A positive active material comprising a first secondary particle with aggregated primary particles and a second single particle coated with zirconium, where the zirconium content on the single particle surface is higher relative to the secondary particle, optimized in a ratio of about 1.5 to 3.0, enhancing the coating efficiency and balancing degradation rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional positive active materials (lithium nickel-based oxide, lithium nickel manganese cobalt composite oxide) are used, then high energy density is achieved, but structure collapse and cracks occur during repeated charges and discharges, deteriorating long-term cycle-life and increasing resistance
Solution Approach 1:
The patent applies local quality by creating a non-uniform zirconium coating distribution where single particles have higher Zr content (1.5 to 3.0 times more than secondary particles) on their surface. This localized enhancement of coating quality on single particles specifically addresses their higher reactivity and degradation rate, while maintaining the energy density benefits of the overall high-nickel composite oxide structure.
Solution Approach 2:
The patent uses composite materials by combining lithium nickel-based composite oxide with zirconium coating to create a hybrid structure. The zirconium forms a protective layer on the particle surfaces, particularly on single particles, creating a composite material that maintains the high capacity of nickel-based oxides while adding the stability and resistance properties of zirconium.
2Ease of manufacture
If uniform zirconium coating is applied to all particles, then coating simplicity is maintained, but the different degradation rates of single particles and secondary particles are not addressed, resulting in suboptimal cycle-life improvement
Solution Approach 1:
The patent implements local quality by establishing a controlled non-uniform coating distribution where single particles receive 1.5 to 3.0 times more zirconium than secondary particles. This is achieved through a simplified one-step coating process that naturally creates the differential coating based on particle characteristics, combining manufacturing simplicity with targeted protection where it is most needed.
Solution Approach 2:
The coating process operates on self-service principles where the single particles and secondary particles automatically receive appropriate coating amounts based on their inherent properties during a single coating operation. The process self-regulates to provide higher coating to the more reactive single particles without requiring complex multi-step procedures or manual intervention.
3Productivity
If only secondary particles are used, then manufacturing efficiency is maintained, but the higher reactivity and faster degradation of single particles are not addressed, limiting cycle-life improvement
Solution Approach 1:
The patent applies local quality by maintaining the efficient secondary particle structure for most of the material while identifying and providing enhanced protection specifically to the single particles that constitute only a portion of the composition. This targeted approach preserves the overall manufacturing efficiency of using secondary particles while locally addressing the cycle-life issue at single particle sites.
Solution Approach 2:
The patent uses partial action by applying the enhanced zirconium coating selectively only to single particles rather than uniformly to all particles. This partial enhancement focuses resources on the specific subset of particles (single particles) that require additional protection, achieving disproportionate cycle-life improvement relative to the amount of additional coating material used.
Data Source
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AI summary
Disclosed are a positive active material for a rechargeable lithium battery, and rechargeable lithium battery including the same. The positive active material for a rechargeable lithium battery includes a first positive active material including a secondary particle including lithium nickel-based composite oxide wherein in the secondary particle, a plurality of primary particles are aggregated, and zirconium on the surface of the secondary particle, and a second positive active material including a single particle including lithium nickel-based composite oxide and zirconium on the surface of the single particle, wherein a ratio of a Zr content (at%) relative to all elements on the surface of the single particle of the second positive active material to a Zr content (at%) to all elements on the surface of the secondary particle of the first positive active material is about 1.5 to about 3.0.