Flexible Battery Module Interconnects for Cell Expansion Stability
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Solution Overview
Problem
The 'deep breathing' effect in lithium metal batteries causes significant volume changes, leading to non-uniform thickness, slip between battery cells and PCBs, potentially breaking the PCB and tabs, resulting in battery pack failure and poor reliability and safety.
Innovation Solution
A battery module design using flexible first and second connection members, replacing the integral PCB, which absorb expansion by deforming to prevent tab separation and ensure stable connections, with the module shape approximating a cuboid for improved stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multiple battery cells are disposed within the battery pack and connected through an integral PCB, then the energy density is improved, but the PCB and tabs may be broken due to the deep breathing effect causing slip and dislocation
Solution Approach 1:
The integral PCB is segmented into multiple independent connection members (first connection members and second connection members). Each connection member independently connects adjacent battery cells, allowing them to deform separately to accommodate the deep breathing effect while maintaining electrical connections. This segmentation prevents the rigid PCB from breaking due to differential expansion and contraction of individual cells.
Solution Approach 2:
The connection members are designed with bending portions that enable dynamic deformation. The bending portions allow the connection members to flex and adapt to the volume changes of battery cells during charging and discharging cycles. This dynamic capability maintains stable electrical connections despite the deep breathing effect, preventing tab detachment and PCB failure.
2Strength
If restraints are added to four side surfaces of the battery cell to prevent PCB and tabs from breaking, then the structural strength is improved, but the slip phenomenon between battery cells and PCB cannot be prevented
Solution Approach 1:
The restraint structure is segmented into multiple connection members distributed across different locations. Each connection member provides localized restraint and support to adjacent battery cells. This distributed segmentation allows the structure to accommodate differential expansion and contraction, preventing slip while maintaining overall structural strength.
Solution Approach 2:
The connection members are designed as flexible thin-film structures with bending portions. These flexible structures provide restraint and support while being able to deform with the battery cells during volume changes. The flexibility allows the connection members to maintain contact and restraint without causing slip or dislocation.
3Reliability
If the first connection member and second connection member are made flexible to absorb expansion, then the reliability is improved, but the external restraint structural member is required to provide compaction
Solution Approach 1:
The connection members serve dual functions: they provide electrical connections between battery cells and simultaneously act as restraint structures. The first connection members connect tabs of adjacent cells, while the second connection members connect the bending portions of first connection members. This merging of connection and restraint functions reduces the need for separate external restraint structures, simplifying the overall device complexity while maintaining reliability.
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 flexible connection members alleviate slip and deformation, enhancing the reliability and safety of the battery module by preventing open circuits and reducing deformation, while also allowing for a lightweight design.
Implementation Method 1
the first connection member and the second connection member can more easily absorb the expansion of the battery cell by generating deformation
Implementation Method 2
The multiple first connection members and the multiple second connection members are flexible members
Data Source
AI summary
Provided are a battery module and a battery pack. The battery module includes multiple battery cells, multiple first connection members and multiple second connection members. A battery cell has an end surface, and the end surface is provided with a tab. The multiple first connection members and the multiple second connection members are flexible members. A first connection member has a first connection portion, a second connection portion and a bend. Two ends of the bend are connected to the first connection portion and the second connection portion, separately. The multiple battery cells are disposed in a superimposed manner. The first connection portion is connected to tabs of two adjacent battery cells. The second connection member is connected between second connection portions of two adjacent first connection members, the first connection portion and the second connection portion are superimposed on the end surface.