Porous Insulators Mitigating Thermal Runaway in Battery Packs
Solution Overview
Problem
Thermal runaway in battery cells can lead to heat propagation and failure, limiting the use of high-energy battery cells due to the risk of thermal runaway propagation in multi-cell battery packs, which existing thermal insulation materials fail to adequately address.
Innovation Solution
The development of thermal insulators with an inorganic thermally-insulating material having a porous structure and a binder that volatilizes at a specific temperature, reducing thermal conductivity and enhancing mechanical strength, including the use of nanoparticles like silica, zirconia, and titania, and a polymer coating to improve thermal insulation and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing thermal insulation materials are used between battery cells, then thermal insulation is provided, but they fail to adequately prevent thermal runaway propagation
Solution Approach 1:
The insulator's thermal conductivity parameter dynamically changes from higher values at low temperatures to lower values at high temperatures through binder volatilization. This parameter transformation enables the insulator to provide adequate thermal insulation during normal operation while effectively blocking heat propagation during thermal runaway events.
Solution Approach 2:
The insulator transitions from a static thermal insulation material to a dynamic one that changes its thermal properties in response to temperature. The binder volatilizes at elevated temperatures to create additional porosity, dynamically adapting the insulator's heat blocking capability to match the thermal threat level.
2Strength
If the binder content is increased to at least 10 vol% for mechanical strength, then mechanical strength is improved, but thermal conductivity may increase before volatilization
Solution Approach 1:
The binder is pre-loaded into the porous structure at sufficient concentrations (at least 10 vol%) to provide necessary mechanical strength during handling and installation. The binder's subsequent volatilization at elevated temperatures then eliminates the thermal conductivity issue, converting the potential disadvantage into an advantage.
Solution Approach 2:
The binder undergoes phase transition from liquid/solid state to vapor state through volatilization at elevated temperatures. This phase change removes the binder material that initially increased thermal conductivity, transforming the insulator into a more effective heat barrier during thermal runaway while maintaining mechanical integrity during normal operation.
3Temperature
If nanoparticle size is reduced to enhance thermal insulation, then thermal conductivity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The insulator utilizes a porous structure formed by nanoparticle aggregation, where the porous network itself provides the thermal insulation mechanism. The porosity, rather than individual particle size, is the critical parameter for thermal performance, allowing flexibility in nanoparticle size selection while maintaining manufacturing feasibility.
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 insulators effectively reduce thermal conductivity after binder volatilization, providing enhanced mechanical strength and thermal insulation, thereby mitigating thermal runaway propagation and improving the safety and energy density of battery packs.
Implementation Method 1
A binder is disposed within the porous structure and configured to volatilize at a volatilization temperature
Implementation Method 2
an inorganic thermally-insulating material having a porous structure
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
Insulators and polymer-coated insulators are provided. The insulators can include thermally-insulating nanoparticles and a binder configured to volatilize at a volatilization temperature. Insulators can also include an inorganic thermally-insulating material forming a porous structure. The porous structure can be configured to reduce the mean free path of gases in the insulator as compared to gases outside the porous structure. Polymer-coated insulators including an inorganic thermally-insulating material and a polymer coating disposed on the surface of the inorganic thermally-insulating material are also provided. Insulators can also include thermally-insulating nanoparticles and an opacifier. The opacifier can include a carbonaceous material coated with a refractory material that inhibits oxidation of the carbonaceous material at a carbon oxidation temperature. The insulators or polymer-coated insulators can be disposed between battery cells or battery cell blocks in an apparatus.