Low-Cobalt Cathode Composition for High-Temperature Li-Ion Life
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Solution Overview
Problem
Lithium secondary batteries using lithium metal oxide particles with low cobalt content face challenges in high-temperature storage characteristics and life-span characteristics due to unstable crystal structures and increased side reactions with electrolytes.
Innovation Solution
A cathode active material layer is designed with lithium metal oxide particles containing minimal cobalt, controlled within specific diameter and length ranges (DA≤4 μm and LA≥47 μm) to enhance packing properties and reduce side reactions, incorporating a conductive material and binder to maintain stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium metal oxide particles with low cobalt content are used, then manufacturing cost is reduced, but high-temperature storage characteristics and life-span characteristics deteriorate due to unstable crystal structures and increased side reactions
Solution Approach 1:
The patent applies parameter changes by precisely controlling the cobalt content within a specific range (0.003 to 0.02 mole fraction) rather than simply reducing it to zero. This optimized parameter range maintains sufficient crystal structure stability for high-temperature storage while minimizing cobalt content to reduce manufacturing costs. The specific parameter threshold resolves the contradiction between cost reduction and performance maintenance.
Solution Approach 2:
The patent employs composite materials by combining lithium metal oxide particles with controlled low cobalt content with specific conductive materials and binders in the cathode active material layer. This composite structure compensates for the reduced structural stability from low cobalt content through the synergistic effects of the additional materials, thereby maintaining reliability while achieving cost reduction through minimized cobalt usage.
2Ease of manufacture
If lithium metal oxide particles with low cobalt content are used, then manufacturing cost is reduced, but life-span characteristics deteriorate due to increased side reactions with electrolytes
Solution Approach 1:
The patent uses parameter changes by establishing a minimum cobalt content threshold (0.003 mole fraction) that prevents excessive side reactions with electrolytes. This lower bound parameter ensures sufficient surface stability and electrochemical performance for long cycle life, while the upper bound (0.02) keeps costs low. The optimized parameter range resolves the contradiction between cost and lifespan.
Solution Approach 2:
The patent introduces conductive materials and binders as intermediary substances in the cathode active material layer. These intermediaries protect the low-cobalt lithium metal oxide particles from direct contact with electrolytes, reducing side reactions and extending battery lifespan while allowing the use of low-cobalt materials for cost reduction.
3Ease of manufacture
If cobalt content is reduced to minimize cost, then manufacturing cost decreases, but crystal structure stability decreases leading to increased side reactions
Solution Approach 1:
The patent applies parameter changes by identifying and controlling the critical cobalt content parameter within a narrow optimal range (0.003 to 0.02 mole fraction). This parameter optimization ensures the crystal structure maintains sufficient stability to prevent Jahn-Teller distortion and phase transitions, while minimizing cobalt content for cost reduction. The specific parameter thresholds directly resolve the contradiction between stability and cost.
Data Source
AI summary
Cathodes and lithium secondary batteries including the cathodes are disclosed. In some implementations, a cathode may include a cathode current collector and a cathode active material layer disposed on the cathode current collector and including cathode active material particles such that the cathode active material layer satisfies a specific equation. The cathode active material particles may include lithium metal oxide particles that include nickel, and may have a mole fraction of cobalt of 0.02 or less with respect to all elements except for lithium and oxygen.