Expandable Graphite Thermal Blocking Sheet for Battery Heat Spread
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Solution Overview
Problem
Existing technologies have not fully resolved the risk of fire or uncontrolled overheating in lithium-ion batteries, particularly in electric vehicles where multiple cells are packed closely, increasing the risk of heat spread and potential fires.
Innovation Solution
A thermal blocking sheet comprising a first layer and a second layer of expandable graphite, where the expandable graphite expands when exposed to heat exceeding a threshold temperature, and the first layer is configured to compress, deform, or melt to accommodate the expanded graphite, thereby reducing heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple battery cells are packed closely together to increase energy density, then productivity and space utilization are improved, but the risk of heat spread and fire increases
Solution Approach 1:
A thermal blocking sheet is introduced as an intermediary layer between adjacent battery cells. The sheet remains thin during normal operation to maintain close cell spacing, but expands when exposed to heat to create thermal insulation, thereby mediating between the need for high energy density and the risk of heat spread.
Solution Approach 2:
The thermal blocking sheet undergoes a parameter change in its thickness and thermal conductivity. During normal operation, it maintains a thin profile with low thermal resistance to allow heat dissipation. When exposed to threshold temperatures, it expands to increase thickness and reduce thermal conductivity, thereby adapting its thermal blocking capability based on temperature conditions.
2Reliability
If thermal blocking materials are placed between battery cells to prevent fire spread, then safety is improved, but the space between cells increases reducing energy density
Solution Approach 1:
The thermal blocking sheet transitions from a static thin layer to a dynamic structure that expands when needed. During normal operation, the sheet remains thin to minimize space occupation. When heat exposure occurs, it dynamically expands to provide effective thermal blocking, thereby maintaining high energy density under normal conditions while ensuring fire safety when required.
Solution Approach 2:
The thermal blocking sheet utilizes a phase transition or chemical reaction that causes it to expand when exposed to threshold temperatures. This phase change allows the material to transform from a compact state during normal operation to an expanded insulating state during thermal events, providing fire protection without permanently occupying additional space.
3Object-affected harmful factors
If expandable graphite is used as thermal blocking material, then thermal insulation effectiveness is improved, but the structural complexity increases
Solution Approach 1:
The thermal blocking sheet is constructed as a composite material combining expandable graphite particles within a polymer or binder matrix. This composite structure provides both mechanical integrity in the unexpanded state and effective thermal blocking when expanded, achieving high thermal insulation performance without requiring complex multi-layer constructions.
Solution Approach 2:
The expandable graphite creates a porous or cellular structure when expanded, trapping air or gas within the expanded matrix. This porous structure significantly reduces thermal conductivity by introducing thermal resistance through the trapped gases, thereby achieving effective thermal insulation through the material's internal structure rather than through complex external design.
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 thermal blocking sheet effectively limits the spread of heat or fire by expanding to create insulation, reducing the risk of overheating and fire in batteries and other applications, such as photovoltaic cells and building structures.
Implementation Method 1
if the thermal blocking sheet is exposed to heat exceeding a threshold temperature the expandable graphite is configured to expand
Implementation Method 2
The thermal blocking sheet effectively limits the spread of heat or fire by expanding to create insulation
Implementation Method 3
the first layer is configured to compress, deform, or melt to accommodate the expanded graphite
Implementation Method 4
the first layer is configured to compress, deform, or melt to accommodate the expanded graphite
Data Source
AI summary
A thermal blocking sheet for reducing the spread of fire or heat, the thermal blocking sheet comprising a first layer and a second layer of expandable graphite. If the thermal blocking sheet is exposed to heat exceeding a threshold temperature the expandable graphite is configured to expand.