Prismatic Battery Cell Pack Compression for Cell Expansion Control
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Solution Overview
Problem
Lithium ion battery packs face challenges in accommodating the elastic and plastic expansion and contraction of battery cells during charging and discharging, which can lead to physical dimension changes of up to 50% over their service life, requiring a system to manage these deformations effectively.
Innovation Solution
A battery cell pack is designed with a prismatic frame and interposed deformable separators that exert compressive force on subsets of battery cells, using compressible springs and barrier layers to manage cyclic and acyclic expansion and contraction, while also incorporating thermal insulation and mitigation materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rigid outer periphery is used for battery cells, then structural stability is improved, but ability to accommodate expansion and contraction deteriorates
Solution Approach 1:
The battery cell is divided into an inner pouch containing electrodes and electrolyte, and an outer rigid periphery. The inner pouch is allowed to expand and contract independently while the outer periphery maintains structural stability. This segmentation allows the system to simultaneously achieve rigidity and adaptability.
Solution Approach 2:
The inner pouch envelope is designed as a flexible structure that can deform elastically and plastically during charging and discharging cycles. This flexible inner shell accommodates volume changes while the rigid outer periphery provides structural support, resolving the contradiction between stability and adaptability.
2Adaptability or versatility
If deformable separators are introduced to accommodate cell deformation, then adaptability is improved, but device complexity increases
Solution Approach 1:
Deformable separators are implemented as thin, flexible planar structures that can bend and deform with the battery cells during expansion and contraction. These separators maintain electrical isolation while accommodating deformation through their inherent flexibility, adding minimal structural complexity.
Solution Approach 2:
The separators are designed with variable geometric parameters including thickness, width, and material properties that allow them to deform in response to cell expansion and contraction. By adjusting these parameters, the separators can accommodate a range of deformation magnitudes without requiring complex mechanical structures.
3Object-affected harmful factors
If compressive force is applied to battery cells, then thermal runaway prevention is improved, but cell deformation increases
Solution Approach 1:
Compressive force is applied to the battery cells and separators in advance to maintain pre-compression during charging and discharging cycles. This preliminary compressive action prevents thermal runaway by ensuring intimate contact between components, while the deformable separators accommodate the resulting deformation through their elastic and plastic properties.
Solution Approach 2:
The separators are constructed as composite structures combining rigid and flexible materials, allowing them to transmit compressive force for thermal safety while simultaneously deforming to accommodate cell expansion and contraction. The composite nature enables both force transmission and shape adaptation.
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
The solution ensures stable operation by uniformly distributing compressive force over the surface area of battery cells, accommodating expansion and contraction, and providing thermal insulation to prevent thermal runaway, thus extending the service life and safety of the battery pack.
Implementation Method 1
each of the plurality of deformable separators having a compressible spring arranged within a spring holding structure
Implementation Method 2
The plurality of deformable separators exert compressive force on the subsets of the plurality of battery cells along a longitudinal axis
Implementation Method 3
the outer layer of the barrier layer being a thermal insulation layer
Data Source
AI summary
A battery cell pack has a plurality of battery cells that are assembled into a prismatic frame, with deformable separators interposed to accommodate elastic and plastic deformation caused by cyclic and acyclic expansion and contraction thereof during charging and discharging over the life of the battery cell pack. The battery cells are arranged in a horizontal stack within the prismatic frame, and the deformable separators are interposed between subsets of the battery cells. The deformable separators exert compressive force on the subsets of the battery cells along a longitudinal axis that is defined by the horizontal stack. The compressive force exerted by the deformable separators is at least a minimum force over a service life of the battery cell pack.