Lithium Secondary Battery Cathode Density Gradient Near the Tab
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Solution Overview
Problem
Lithium secondary batteries face issues with lithium ion precipitation and reduced operational reliability due to varying lithium ion movement speeds, leading to decreased lifespan and stability.
Innovation Solution
The battery design includes a cathode and anode with distinct electrode density gradients, specifically a higher density near the tab and lower density further away, along with a separator structure to manage lithium ion movement uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform electrode density is used throughout the cathode and anode, then manufacturing is simpler, but lithium ion movement speed varies causing precipitation and reduced reliability
Solution Approach 1:
The patent applies local quality by creating different electrode densities in different regions of the cathode and anode. Specifically, the first electrode portion adjacent to the tab has a first density, while the second electrode portion spaced from the tab has a second density that differs by 1.5 to 6%. This non-uniform density distribution optimizes lithium ion movement speed in different regions, preventing precipitation and improving operational reliability.
2Productivity
If lithium ion movement speed is increased for faster charging, then charging speed improves, but lithium precipitation occurs reducing lifespan
Solution Approach 1:
The patent uses local quality to create region-specific electrode densities that control lithium ion movement speeds. The first electrode portion near the tab and the second electrode portion spaced from it have different densities (differing by 1.5 to 6%), which creates optimized ion transport pathways. This prevents excessive ion accumulation and precipitation while maintaining fast charging capability, thereby extending battery lifespan.
Solution Approach 2:
The patent applies parameter changes by modifying the electrode density parameter in different spatial regions. By controlling the density difference between the first and second electrode portions to be within 1.5 to 6%, the patent optimizes lithium ion transport kinetics. This parameter optimization enables faster charging without causing lithium precipitation, thus preserving battery lifespan.
3Reliability
If electrode density near the tab is increased, then lithium ion movement is controlled, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements local quality by specifying different density requirements for different electrode regions. The first electrode portion adjacent to the tab and the second electrode portion spaced from it are controlled to have densities differing by 1.5 to 6%. This approach improves stability by controlling lithium ion movement while maintaining achievable manufacturing precision through defined density ranges.
Data Source
AI summary
The lithium secondary battery includes a cathode which includes a cathode active material layer including a cathode current collector, a cathode tab protruding from one end thereof in a longitudinal direction of the cathode current collector, a second cathode portion disposed spaced apart from the cathode tab on the cathode current collector, and a first cathode portion disposed adjacent to the cathode tab on the cathode current collector and having an electrode density higher than that of the second cathode portion, and an anode disposed to face the cathode. Life-span characteristics of the lithium secondary battery may be improved by controlling the electrode density in the peripheral part of the cathode tab.