Lithium-Ion Electrode Balance for Overcharge Resistance and Durability
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving both high resistance to overcharge and high leaving durability, as conventional materials either reduce performance upon overcharge or compromise durability.
Innovation Solution
The lithium ion secondary battery incorporates a positive electrode with Li a Ni x Co y M z O 2 as the active material and a negative electrode with non-graphitic carbon, where the basis weight ratio of the positive active material to the negative active material satisfies 0.65 ≤ P/N ≤ 1.05.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive electrode materials are used, then overcharge resistance is improved, but leaving durability is lowered
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compositional parameters of the lithium nickel cobalt manganese oxide (Li a Ni x Co y M z O 2) positive electrode material, where 0.9 ≤ a ≤ 1.2, 0.3 ≤ x ≤ 0.8, and 0.2 ≤ y + z ≤ 0.7. Additionally, the basis weight ratio of positive to negative active material is optimized to 0.65 ≤ P/N ≤ 1.05. These parameter optimizations enable the battery to achieve both high overcharge resistance and high leaving durability simultaneously.
2Reliability
If protection circuit is used to prevent overcharge, then safety is improved, but device complexity is increased
Solution Approach 1:
The patent applies the self-service principle by designing the battery itself to inherently resist overcharge through its material composition and structure. The lithium nickel cobalt manganese oxide positive electrode material combined with non-graphitic carbon negative electrode and optimized basis weight ratio enables the battery to automatically prevent overcharge damage without requiring external protection circuits, thus maintaining safety while reducing device complexity.
Data Source
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AI summary
The present embodiment provides a lithium ion secondary battery including a positive electrode containing LiaNixCoyMzO2 (0.9 ≤ a ≤ 1.2, 0.3 ≤ x ≤ 0.8, 0.2 ≤ y + z ≤ 0.7, where M is a metal element other than Li, Ni, and Co) as a positive active material, and a negative electrode containing non-graphitic carbon as a negative active material. In this lithium ion secondary battery, at a portion where the positive electrode and the negative electrode face each other, a basis weight (P) of the positive active material and a basis weight (N) of the negative active material satisfy a relational expression of 0.65 ≤ P/N ≤ 1.05.