Battery Pack Spacer Structure for Swelling and Heat Isolation
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Solution Overview
Problem
High-capacity secondary batteries in vehicle applications experience swelling and heat generation issues during charging and discharging cycles, leading to performance deterioration and potential heat conduction problems between adjacent batteries, which existing heat conduction suppressing members fail to adequately address.
Innovation Solution
A battery pack design featuring spacers with a two-layer structure, where the first part has an elastic modulus of 1 MPa to 10 MPa and the second part includes a porous material with high heat resistance and low elastic modulus, allowing for effective absorption of battery swelling and suppression of heat conduction between adjacent batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat conduction suppressing member with high elastic modulus is used to suppress heat conduction between secondary batteries, then heat resistance is improved, but the ability to absorb battery swelling deteriorates
Solution Approach 1:
The spacer is divided into two distinct parts: a first part with high elastic modulus (5 MPa to 500 MPa) for heat resistance, and a second part with low elastic modulus (0.01 MPa to 5 MPa) for swelling absorption. This segmentation allows each part to perform its specific function optimally without compromising the other.
Solution Approach 2:
The spacer combines materials with different elastic moduli into a composite structure. The first part uses rigid heat-resistant materials while the second part uses soft swelling-absorbing materials, creating a composite spacer that simultaneously achieves both heat resistance and swelling absorption capabilities.
2Stability of the object's composition
If a rigid spacer structure is used to maintain battery pack stability, then structural stability is improved, but the ability to accommodate battery expansion deteriorates
Solution Approach 1:
The spacer is segmented into a first part for structural stability and a second part for expansion accommodation. The first part maintains the battery pack's overall stability while the second part flexibly accommodates battery expansion through its low elastic modulus and porous structure.
Solution Approach 2:
Different regions of the spacer have different mechanical properties: the first part has high rigidity for stability, while the second part has low rigidity and high porosity for expansion accommodation. This local quality differentiation allows the spacer to simultaneously provide stability and adaptability.
3Adaptability or versatility
If a porous material with low elastic modulus is used to absorb battery swelling, then swelling absorption is improved, but heat resistance deteriorates
Solution Approach 1:
The porous low elastic modulus material is confined to the second part of the spacer, while the first part uses high elastic modulus heat-resistant material. This segmentation ensures that the porous material provides swelling absorption only where needed, without compromising overall heat resistance.
Solution Approach 2:
The spacer combines porous low elastic modulus materials (for swelling absorption) with dense high elastic modulus heat-resistant materials in a composite structure. This composite approach allows the porous material to perform its swelling absorption function while being complemented by heat-resistant materials that prevent thermal degradation.
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 spacer design stabilizes the battery pack by absorbing swelling and reducing heat conduction, thereby improving the battery's performance and preventing overheating, as demonstrated by reduced thickness changes and absence of lithium precipitation after cycling tests.
Implementation Method 1
the elastic modulus is a value obtained as an inclination of an approximation line in a range of a compression ratio from 1 to 20% from a compression load-compression ratio curve... formed by performing compression until a compression load becomes 3.9 MPa
Implementation Method 2
the second part includes a porous part, 50 mass % or more of the entire porous part is occupied by a material that satisfies both the following conditions: (1) a classification of heat resistance based on JIS K 6380 (2014) of Japanese Industrial Standards is E or more
Data Source
AI summary
A battery pack disclosed herein includes a plurality of rectangular secondary batteries that are disposed along an arrangement direction, and a spacer that is disposed between the rectangular secondary batteries that are adjacent in the arrangement direction. The spacer includes a first part and a second part, the first part has an elastic modulus of 1 MPa or more and 10 MPa or less, the second part includes a porous part, and 50 mass % or more of the entire porous part is occupied by a material that satisfies both the following conditions: a classification of heat resistance based on JIS K 6380 (2014) is E or more; and the elastic modulus in the arrangement direction is 0.02 MPa or more and 0.9 MPa or less.