Expandable Graphite Flame-Retardant Layer for Battery Module Venting
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Solution Overview
Problem
Battery modules face thermal runaway issues due to excessive heat generation, which can trigger cascading thermal events among adjacent cells, posing a significant safety risk and requiring effective flame retardant solutions to manage hot gases and heat dissipation.
Innovation Solution
Incorporating an expandable graphite flame retardant layer within the battery module's outer shell, which expands during thermal events to create channels for hot gas egress through strategically positioned ports, utilizing a ceramic membrane to facilitate expansion without blocking pathways, and potentially combining with intercalated flame retardant materials and a polymeric binder for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flame retardant layer with expandable graphite is added to the battery module, then flame retardancy and thermal safety are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The expandable graphite particles are nested within a polymeric binder matrix to form a composite flame retardant layer. The binder encapsulates the graphite particles, creating a nested structure where the graphite is contained within the polymer matrix, allowing the flame retardant layer to function as an integrated unit that combines structural support and flame retardancy.
Solution Approach 2:
The flame retardant layer is constructed as a composite material combining expandable graphite particles with a polymeric binder. This composite structure leverages the high thermal stability and expansion characteristics of graphite alongside the adhesive and structural properties of the polymer matrix, achieving enhanced flame retardancy while maintaining layer integrity.
2Reliability
If the expandable graphite layer is made thicker to improve flame retardancy, then thermal safety is improved, but the volume of the battery module increases
Solution Approach 1:
The expandable graphite particles undergo a phase transition when exposed to thermal runaway conditions, expanding from a compact state to a voluminous expanded state. This phase transition allows the flame retardant layer to provide thick protective characteristics during thermal events without requiring a physically thick layer during normal operation, thus maintaining battery module compactness while ensuring thermal safety.
Solution Approach 2:
The flame retardant layer is designed to be dynamic in thickness - thin during normal operation to maintain battery module compactness, and thick during thermal events when the expandable graphite expands. This dynamic characteristic allows the system to adapt its protective thickness based on operational conditions without permanently increasing battery module volume.
3Reliability
If the expandable graphite particles are made larger to improve expansion effectiveness, then flame retardancy is improved, but manufacturing precision and uniformity decrease
Solution Approach 1:
The patent employs a bimodal particle size distribution where different regions of the flame retardant layer contain different proportions of large and small graphite particles. This local quality variation allows larger particles to provide effective expansion in critical areas while smaller particles ensure uniform distribution and filling of voids, maintaining manufacturing precision while achieving effective flame retardancy.
Solution Approach 2:
The patent changes the particle size parameter by using a distribution of different sizes rather than a single uniform size. This parameter change allows the system to benefit from both large particles (which expand more effectively) and small particles (which distribute more uniformly), resolving the contradiction between expansion effectiveness and manufacturing precision.
4Productivity
If the expandable graphite expands rapidly during thermal events, then hot gas egress is improved, but the risk of blocking exit ports increases
Solution Approach 1:
The flame retardant layer is designed with spatially varying properties, including gradients in particle size distribution and binder composition. This local quality variation ensures that expansion occurs in a controlled manner with different regions expanding at different rates, creating channels that guide hot gas flow toward exit ports while preventing uniform blocking of all egress paths.
Solution Approach 2:
The polymeric binder acts as an intermediary that controls the expansion behavior of the graphite particles. The binder matrix modulates the expansion rate and pattern, allowing graphite particles to expand while the binder maintains structural integrity and creates controlled pathways. This intermediary role prevents uncontrolled expansion that would block exit ports while still enabling effective hot gas egress.
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 expandable graphite layer effectively channels hot gases to exit ports, mitigating thermal runaway by directing heat away from sensitive areas and reducing the risk of spreading thermal events to adjacent cells, thereby enhancing the safety and reliability of battery modules.
Implementation Method 1
The expandable graphite is operative to expand during a thermal event that results in an increase in battery module temperature
Implementation Method 2
the expandable graphite undergoes exfoliation during a thermal event
Implementation Method 3
the flame retardant layer is arranged to contact a thermal distribution plate that has a higher coefficient of thermal conductivity than a material used in the outer wall
Data Source
AI summary
Disclosed herein is a battery module comprising a plurality of battery cells encased in an outer shell. The outer shell has disposed on an inner surface a flame retardant layer that comprises expandable graphite. The expandable graphite is operative to expand during an thermal event that results in an increase in battery module temperature. Disclosed herein too is a method comprising disposing in a battery module a flame retardant layer; where the battery module comprises a plurality of battery cells encased in an outer shell. The outer shell has disposed on an inner surface a flame retardant layer that comprises expandable graphite. The expandable graphite is operative to expand during an thermal event that results in an increase in battery module temperature.