Asymmetric Battery Case Sidewall for Lithium-Ion Safety
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Solution Overview
Problem
Secondary batteries face challenges in achieving high energy density while ensuring safety, particularly in on-vehicle applications where space and weight are critical, and there is a risk of overcharge leading to heat generation and gas formation.
Innovation Solution
A lithium-ion secondary battery design featuring a wound electrode body with strip-shaped positive and negative electrode sheets and separators, where the positive electrode sheet has an uncoated portion and a thicker sidewall on the battery case facing this portion, enhancing safety and energy density by allowing for a larger internal space and efficient heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a heat releasing member is disposed between the battery case and the battery elements, then safety is improved, but volumetric energy density deteriorates due to reduced space for battery elements
Solution Approach 1:
The invention extracts the heat releasing function from a separate component (heat releasing member) and integrates it into the battery case structure itself through the thicker sidewall design. This eliminates the need for additional space-consuming heat releasing components while maintaining the safety function.
Solution Approach 2:
The invention merges the structural support function and heat releasing function into a single integrated component (the battery case sidewall). The thicker sidewall simultaneously provides mechanical support and acts as a heat sink, combining multiple functions into one element to save space.
2Reliability
If the space for accommodating battery elements is reduced to make room for safety components, then safety is improved, but energy density deteriorates
Solution Approach 1:
The invention applies local quality by making only the specific sidewall facing the uncoated portion thicker, rather than uniformly thickening the entire battery case. This localized thickening provides safety where needed while minimizing the impact on overall battery capacity and energy density.
3Reliability
If a thicker sidewall is provided on the battery case facing the uncoated portion, then safety against heat and deformation is improved, but device complexity increases
Solution Approach 1:
The invention employs asymmetry by providing different sidewall thicknesses at different locations of the battery case. The sidewall facing the uncoated portion is thicker to handle heat and deformation risks, while other sidewalls maintain standard thickness, creating an asymmetric structure optimized for safety where needed.
Data Source
AI summary
In a lithium-ion secondary battery (100), a battery case (300) has sidewalls (300A, 300B) facing toward side ends of a wound electrode body (200), the side ends being at opposite lateral sides of the positive electrode sheet (220), and of the sidewalls (300A, 300B), one of the sidewalls (300A) (positive-electrode-side sidewall) facing toward an uncoated portion (222) of the positive electrode sheet (220) is thicker than the other sidewall (300B) (negative-electrode-side sidewall). In other words, the relationship between the thickness A of the one sidewall (300A) facing toward the uncoated portion (222) of the positive electrode sheet (220) and the thickness B of the other sidewall (300B) is A>B.