Single-Cell Case Coating to Prevent Thermal Runaway Melting
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Solution Overview
Problem
High energy-density lithium-ion batteries face significant safety challenges due to thermal runaway, which can cause the aluminum case to melt, leading to electrolyte leakage and thermal propagation to neighboring cells, with existing thermal barriers being ineffective at high temperatures.
Innovation Solution
A composite case with a double-layer structure coating is introduced, featuring an inner aerogel layer with ultra-low thermal conductivity and an outer barrier layer to prevent electrolyte solvent permeation, applied to a hard aluminum substrate or soft aluminum laminate film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional relief valve is used to vent gas and reduce pressure during thermal runaway, then the internal pressure is reduced, but the aluminum case melts at high temperatures (700-800°C) before the valve opens, causing thermal propagation to neighboring cells
Solution Approach 1:
A thermal barrier layer is introduced as an intermediary substance between the aluminum case and the external environment. This layer mediates the thermal interaction by absorbing and insulating heat, preventing the aluminum case from reaching its melting point even when the internal temperature reaches 700-800°C during thermal runaway events.
Solution Approach 2:
The patent employs a composite material structure consisting of the aluminum case combined with a thermal barrier layer. This composite structure leverages the mechanical strength of aluminum while adding the thermal insulation properties of the barrier layer, creating a system that resists both pressure and extreme temperatures.
2Strength
If the aluminum case is used to provide structural strength, then the cell maintains structural integrity, but the case melts at high temperatures causing electrolyte leakage and thermal propagation
Solution Approach 1:
The thermal barrier layer serves as a protective intermediary between the aluminum case and the thermal runaway environment. It absorbs the harmful thermal energy before it can reach the aluminum case, preventing melting and subsequent electrolyte leakage while maintaining the case's structural strength.
Solution Approach 2:
The thermal barrier layer provides beforehand cushioning by being pre-applied to the aluminum case. This protective layer is in place before thermal runaway occurs, cushioning the case against thermal damage and preventing the chain reaction of melting, leakage, and thermal propagation to neighboring cells.
3Reliability
If a thermal barrier is provided between single cells to stop thermal propagation, then thermal spread is prevented, but the barrier cannot stop thermal propagation when the aluminum case melts at high temperatures
Solution Approach 1:
The patent uses a composite material system where the thermal barrier layer is integrated with the aluminum case. This composite structure provides continuous thermal protection that remains effective even when exposed to the extreme temperatures of thermal runaway, preventing both direct thermal propagation and indirect propagation through melted aluminum.
Solution Approach 2:
The thermal barrier layer is designed to sacrificially absorb thermal energy during thermal runaway events. It may degrade or consume itself in the process of protecting the aluminum case and preventing thermal propagation, serving as a disposable protective element that sacrifices itself for the safety of the entire battery pack.
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 composite case effectively prevents the aluminum case from melting during thermal runaway, significantly reducing heat transfer to the case and preventing thermal propagation between cells, thereby enhancing safety and reliability.
Implementation Method 1
an inner layer proximal to the substrate, containing an aerogel material which has an ultra-low thermal conductivity
Implementation Method 2
an outer layer distal to the substrate and coated on the inner layer, containing a barrier material which may prevent an electrolyte solvent from permeating into the inner layer
Data Source
AI summary
The present invention relates to a case having a thermal barrier layer for a single cell. The composite case comprises a substrate and a double-layer structure coating on the substrate, wherein the double-layer structure coating includes an inner layer containing an aerogel material which has a ultra-low thermal conductivity, and an outer layer containing a barrier material which may prevent an electrolyte solvent from permeating into the inner layer. According to the present invention, the composite case can preserve cases in a prismatic or pouch cell from melting when cell goes to thermal runaway.