Wound Secondary Battery Tab Layout for Fast Charging Safety
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Solution Overview
Problem
Existing lithium-ion secondary batteries face challenges in achieving high safety, high-speed charge and discharge, and reduced charge and discharge times while maintaining high capacity.
Innovation Solution
A wound secondary battery design with specific tab configurations and a positive electrode active material comprising regions with varying compositions, including lithium, cobalt, oxygen, and optionally magnesium and nickel, with a high volume resistivity, is employed to inhibit internal short circuits and enhance safety and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the capacity of lithium-ion secondary battery is increased, then the energy storage is improved, but the charge and discharge time increases
Solution Approach 1:
The positive electrode active material is designed with non-uniform composition: a first region containing lithium, cobalt, and oxygen, and a second region containing lithium, cobalt, magnesium, and oxygen. This local quality variation optimizes both capacity and charge/discharge rate by having different regions serve different functional purposes.
Solution Approach 2:
The patent changes the compositional parameters of the positive electrode active material by introducing magnesium into a second region, creating distinct chemical environments that facilitate both high capacity storage and rapid ion transport, thereby reducing charge/discharge time while maintaining high capacity.
2Quantity of substance
If the positive electrode active material composition is optimized for high capacity, then the energy storage is improved, but the thermal stability deteriorates
Solution Approach 1:
Different regions of the positive electrode active material have different compositions: the first region (lithium, cobalt, oxygen) provides high capacity, while the second region (lithium, cobalt, magnesium, oxygen) enhances thermal stability. This spatial separation of functions resolves the contradiction between capacity and safety.
Solution Approach 2:
The positive electrode active material is a composite structure with two distinct regions having different chemical compositions. This composite approach allows combining the high-capacity characteristics of one region with the thermal-stability characteristics of another region, achieving both high capacity and high safety simultaneously.
3Productivity
If the tab configuration is optimized for current collection, then the charge and discharge speed is improved, but the internal short circuit risk increases
Solution Approach 1:
The current collector is divided into multiple tabs (first tab, second tab, third tab, fourth tab) positioned at different locations. This segmentation distributes current collection points, improving charge/discharge speed while reducing current density at any single point, thereby lowering internal short circuit risk.
Solution Approach 2:
Instead of concentrating current collection at a single point or along one line, the tabs are distributed across two dimensions on the current collector surface. This dimensional distribution optimizes both current collection efficiency and safety by spreading the electrical load across multiple spatial locations.
Data Source
AI summary
To provide a secondary battery that has both high safety and a short charge and discharge time. The secondary battery is a wound secondary battery, and a positive electrode current collector of a positive electrode includes a first tab and a second tab, and a negative electrode current collector of a negative electrode includes a third tab and a fourth tab. The first tab is positioned in a portion closer to a center of a winding than the second tab is, and the third tab is positioned in a portion closer to the center of the winding than the fourth tab is. The first tab and the second tab are bonded in a first bonding portion, and the third tab and the fourth tab are bonded in a second bonding portion. The positive electrode active material includes a first region and a second region positioned on a surface side of the positive electrode active material. The first region contains lithium, cobalt, and oxygen. The second region contains lithium, cobalt, magnesium, and oxygen.