Wound Electrode Body Moisture Control for SEI and Thermal Stability
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Solution Overview
Problem
In large secondary batteries with a wound electrode body, moisture distribution varies significantly along the winding axis, leading to decreased thermal stability due to local imbalances in moisture content, which affects the formation of the solid electrolyte interface film and increases the risk of gas generation and battery deterioration.
Innovation Solution
The electrode body design ensures a uniform moisture distribution by maintaining an average moisture content of 80 to 150 ppm with a difference of less than ±20 ppm between the central and end parts, achieved by controlling manufacturing conditions such as humidity and drying processes, thereby promoting homogeneous SEI film formation and reducing metal corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the electrode body is made long in width for large secondary batteries, then the battery capacity increases, but the moisture distribution becomes uneven leading to decreased thermal stability
Solution Approach 1:
The patent applies local quality by differentiating moisture control between the central part and end parts of the electrode body. Specifically, it maintains moisture content in the central part at 50-100 ppm and at the end parts at 100-150 ppm, creating localized moisture gradients that ensure uniform SEI film formation across the entire electrode surface, thereby resolving the thermal stability issue in large-capacity batteries.
Solution Approach 2:
The patent changes the moisture content parameter differently across various regions of the electrode body. By setting specific moisture content ranges for the central part (50-100 ppm) versus end parts (100-150 ppm), and controlling the moisture difference to be 20-50 ppm, it optimizes thermal stability while maintaining high battery capacity.
2Duration of action of stationary object
If moisture content is increased to improve cycle durability, then cycle durability improves, but thermal stability decreases due to excessive moisture
Solution Approach 1:
The patent optimizes the moisture content parameter within a precise range (central part: 50-100 ppm, end parts: 100-150 ppm) to simultaneously achieve good cycle durability and thermal stability. This controlled parameter change avoids both insufficient moisture (which harms cycle durability) and excessive moisture (which harms thermal stability).
Solution Approach 2:
The patent implements feedback control by measuring and adjusting moisture content in different parts of the electrode body to maintain the optimal difference of 20-50 ppm between central and end parts. This feedback mechanism ensures that moisture levels remain within the range that promotes both cycle durability and thermal stability.
3Ease of manufacture
If moisture enters only through end parts in wound electrode bodies, then manufacturing is simplified, but moisture distribution becomes uneven causing local thermal instability
Solution Approach 1:
The patent applies local quality by creating different moisture content zones within the electrode body. Although moisture enters only through end parts during manufacturing, the patent controls the distribution to achieve 100-150 ppm at end parts and 50-100 ppm in the central part, ensuring uniform SEI film formation and thermal stability throughout.
Solution Approach 2:
The patent changes the moisture content parameter across different spatial locations of the electrode body. By controlling end part moisture at 100-150 ppm and central part moisture at 50-100 ppm with a difference of 20-50 ppm, it transforms the uneven moisture distribution from a manufacturing limitation into a controlled parameter that ensures thermal stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the thermal stability of the secondary battery by ensuring consistent moisture levels, improving the quality and uniformity of the solid electrolyte interface film, thus reducing resistance and enhancing overall battery performance.
Implementation Method 1
an average of a central part moisture amount and an end part moisture amount in the winding axis direction is 80 ppm or more and 150 ppm or less and a difference between the central part moisture amount and the end part moisture amount in the winding axis direction is less than ±20 ppm
Data Source
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AI summary
In an electrode body (20) disclosed herein, a positive electrode (22) with a band shape and a negative electrode (24) with a band shape are stacked in an insulated state and wound in a longitudinal direction (LD). An average of a central part moisture amount and an end part moisture amount in a winding axis (WL) direction is 80 ppm or more and 150 ppm or less and a difference between the central part moisture amount and the end part moisture amount in the winding axis (WL) direction is less than ±20 ppm. A corresponding method of manufacturing is also disclosed.