Structural Battery Pack Adhesive Recessing for Weld Stress Relief
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Solution Overview
Problem
Conventional vehicle battery packs face reliability issues due to stress concentrations at weld joints and edges, leading to mechanical failure and electrolyte leaks, which can be exacerbated by the use of adhesives that reduce cell serviceability and increase the risk of thermal runaway during abuse conditions.
Innovation Solution
The battery pack design incorporates a recessed adhesive layer between the housing and cells, with a void along the lateral walls to reduce stress concentrations, and may include additional features like increased bond line thickness, thermal conductivity, and L-shaped brackets to distribute loads and enhance structural integration, thereby reducing mechanical stress and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If cells are bonded with adhesives to the pack housing to increase structural stiffness, then the overall pack mass and volume are reduced, but the adhesive pulls cells open in high stress areas leading to reliability issues
Solution Approach 1:
The patent removes the adhesive layer from high stress areas (edges and corners of cells) while maintaining it in lower stress areas. This selective extraction of adhesive from critical regions prevents the adhesive from pulling cells open during mechanical shock and vibration, while still providing structural bonding where needed.
Solution Approach 2:
The patent applies different bonding strategies to different regions of the cell housing. High stress areas (edges and corners) are left unbonded or use alternative bonding methods, while lower stress areas use traditional adhesive bonding. This local differentiation of bonding quality optimizes both structural integrity and reliability under mechanical loading.
2Strength
If cells are bonded with adhesives to achieve structural integration, then the pack stiffness increases, but cell serviceability is lost
Solution Approach 1:
By removing adhesive from high stress areas, the patent creates natural separation zones that facilitate cell removal and replacement during servicing, while maintaining sufficient structural bonding in other areas to preserve pack stiffness during normal operation.
Solution Approach 2:
The bonding strategy is segmented into different regions: fully bonded areas for structural stability, partially bonded areas for balanced performance, and unbonded areas for serviceability. This segmentation allows the pack to maintain stiffness while enabling cell replacement when needed.
3Quantity of substance
If thin cell housings are used to maintain energy density, then the cells are more susceptible to mechanical failure at weld joints and edges, but energy density is maintained
Solution Approach 1:
The patent removes adhesive from the edges and corners of thin cell housings where stress concentrations occur during mechanical shock and vibration. This prevents the adhesive from creating additional stress points that could lead to mechanical failure of the thin-walled cells, while maintaining bonding in areas where it provides structural support.
Solution Approach 2:
The patent strategically places adhesive bonds in locations that provide structural reinforcement before mechanical loads are applied, while avoiding locations where adhesive would create stress concentrations. This beforehand cushioning through selective bonding protects thin-walled cells from mechanical failure during abuse conditions.
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 enhances the reliability and structural integrity of battery packs by minimizing stress on cell edges and weld joints, reducing the risk of mechanical failure and thermal runaway, while maintaining energy density and compactness.
Implementation Method 1
stress concentrations that originate from mechanical shock and vibration are located near welds or other sensitive areas on the cell
Implementation Method 2
the adhesive comprises a thermally conductive adhesive
Data Source
AI summary
A battery pack can include a plurality of battery cells arranged adjacent one another in a row. The battery pack can include a first spacer plate aligned with and positioned adjacent the first cell of the plurality of battery cells, a second spacer plate aligned with and positioned adjacent the last cell of the plurality of battery cells, and a housing enclosing the plurality of battery cells. The housing can include a first sidewall positioned adjacent the first spacer plate and a second sidewall positioned adjacent the second spacer plate such that the plurality of battery cells can be positioned between the first sidewall and the second sidewall. The battery pack can include a cover. A layer of adhesive can be disposed between the battery cells and the cover. Various techniques can be employed to improve the durability of the battery pack.