Flat Cell Sheath Inclined Wall Pressure Distribution
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Solution Overview
Problem
In flat cells, uneven surface pressure distribution leads to varied intervals between electrode plates, causing uneven degradation of electrode active materials, particularly in laminate-type cells used in vehicles, which affects the cell's performance and strength of the sheath member.
Innovation Solution
A flat cell design featuring a sheath member with a flat wall and inclined walls that curve inward when evacuated, ensuring uniform pressure distribution and maintaining the strength of the sheath member by molding the inclined walls at an angle of 45° to 80°, and optionally including corner portions to further equalize pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sheath member is formed by heat-sealing sheets without previous molding, then the manufacturing process is simple, but the surface pressure distribution becomes uneven
Solution Approach 1:
The sheath member is pre-formed with a convex shape including a flat wall and inclined walls before the power-generating element is inserted. This preliminary shaping allows uniform pressure distribution during evacuation while maintaining manufacturing simplicity through subsequent heat-sealing
Solution Approach 2:
The sheath member features a flat wall portion that contacts the power-generating element directly, creating a localized region of uniform pressure distribution. This local structural modification addresses the pressure distribution issue without complicating the overall manufacturing process
2Strength
If vertical walls are molded in the sheath member to accommodate the power-generating element, then the structure provides good support, but wrinkles are caused during evacuation reducing strength
Solution Approach 1:
The sheath member uses inclined walls with curved surfaces instead of sharp vertical walls. The curved transition between the flat wall and outer periphery prevents stress concentration and wrinkle formation during evacuation, maintaining both structural support and wrinkle resistance
Solution Approach 2:
The sheath member is pre-formed with a convex shape that anticipates the pressure changes during evacuation. This preliminary shaping creates a structure that resists wrinkle formation by distributing stresses uniformly before evacuation occurs
3Quantity of substance
If the intervals between electrode plates are small in the outer periphery, then the cell capacity increases, but the degradation distribution becomes uneven
Solution Approach 1:
The flat wall portion of the sheath member creates a localized region where uniform pressure is applied to the power-generating element. This ensures consistent intervals between electrode plates across the entire cell, achieving uniform degradation distribution while maintaining high cell capacity
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 design equalizes the degradation distribution of electrode active materials, reduces impedance, and maintains the strength of the sheath member by ensuring uniform surface pressure across the power-generating element, enhancing the cell's capacity and reducing wrinkles.
Implementation Method 1
when the inside of the cell is evacuated, the inclined wall is curved toward the inside of the cell
Data Source
AI summary
A flat cell of the present invention has: a power-generating element which includes a positive plate, a negative plate, and a separator provided between the positive and negative plates; a sheath member which is composed of a upper sheath member and a lower sheath member and accommodates the power-generating element; and positive and negative terminals connected to the power-generating element through a plurality of collectors and extended from a outer periphery of the sheath member. The upper sheath member includes a flat wall in a portion accommodating the power-generating element and an inclined wall between the flat wall and the outer periphery of the sheath member. When the inside of the cell is evacuated, the inclined wall is curved toward the inside of the cell.