In recent years, the rapid growth of the electric vehicle (EV) industry, particularly in China, has highlighted the critical need for advanced safety measures in EV power battery systems. As the primary energy source for electric vehicles, EV power batteries are susceptible to thermal runaway events, which can lead to fires, explosions, and severe risks to occupants. My research focuses on addressing these challenges by developing an innovative thermal insulation and flame retardant solution centered on SiO2 aerogel materials. This study aims to design, simulate, and experimentally validate a protective scheme that enhances the safety of China EV battery systems, ensuring they meet stringent performance requirements under extreme conditions.
The increasing adoption of electric vehicles worldwide, driven by environmental concerns and technological advancements, has placed EV power battery safety at the forefront of automotive engineering. Thermal runaway in lithium-ion batteries, often triggered by high temperatures or mechanical impacts, can propagate rapidly through battery modules, resulting in catastrophic failures. Traditional insulation materials, such as foam, glass wool, or vacuum insulation panels, fall short in providing adequate protection due to their limited thermal stability and high thermal conductivity. In contrast, SiO2 aerogel stands out as a superior material due to its nano-porous structure, which minimizes heat transfer through conduction, convection, and radiation. This paper presents a comprehensive approach to integrating SiO2 aerogel into EV power battery designs, leveraging finite element simulations and experimental tests to demonstrate its efficacy in delaying heat propagation and ensuring occupant safety.
The design of the thermal insulation and flame retardant scheme for China EV battery systems involves strategic placement of SiO2 aerogel layers within the battery pack. Typically, an EV power battery pack consists of multiple battery modules, each containing numerous cells, along with cooling systems, management units, and structural components. In my approach, SiO2 aerogel mats are positioned between individual cells and on the upper and lower surfaces of the battery modules. This configuration not only impedes lateral heat transfer between cells but also blocks upward heat flow toward the vehicle interior, thereby containing thermal events and providing valuable time for emergency responses. The lightweight and flexible nature of SiO2 aerogel allows for seamless integration without significantly increasing the pack’s weight or volume, which is crucial for maintaining the overall efficiency of EV power battery systems.
To quantify the performance of this design, I employed numerical simulations using ANSYS Fluent software, incorporating a multi-source multi-destination (MSMD) algorithm to model the electro-thermal behavior of lithium-ion batteries. The simulation setup included a simplified geometry representing two adjacent battery cells separated by a 3 mm thick SiO2 aerogel layer, with an additional 5 mm layer above the cells to mimic the insulation against the vehicle floor. The initial conditions were set at room temperature (15°C), with one cell subjected to a short-circuit scenario reaching up to 1000°C over a 300-second period. This model accounted for key heat generation mechanisms in batteries, such as electrochemical reactions, polarization, Joule heating, and internal short circuits, as described by the pseudo-two-dimensional (P2D) model. The governing equations for heat transfer, including Fourier’s law for conduction and Newton’s law for convection, were applied to simulate transient thermal behavior. For instance, the heat conduction equation is given by:
$$ \phi = -\lambda A \frac{dt}{dx} $$
where $\phi$ represents the heat flux, $\lambda$ is the thermal conductivity, $A$ is the area, and $\frac{dt}{dx}$ is the temperature gradient. Similarly, the energy conservation equation for non-steady-state heat transfer in three dimensions is expressed as:
$$ \frac{\partial t}{\partial \tau} = \frac{\lambda}{\rho c_i} \left( \frac{\partial^2 t}{\partial x^2} + \frac{\partial^2 t}{\partial y^2} + \frac{\partial^2 t}{\partial z^2} \right) $$
Here, $\tau$ denotes time, $\rho$ is density, and $c_i$ is specific heat capacity. The material properties for the lithium-ion battery components and SiO2 aerogel were defined based on experimental data, as summarized in the tables below. For example, the thermal conductivity of SiO2 aerogel varies with temperature, ranging from 0.020 W/(m·K) at 20°C to 0.061 W/(m·K) at 1000°C, which significantly influences its insulation performance.
| Parameter | Meaning | Unit | Al Foil | Positive Electrode | Separator | Negative Electrode | Cu Foil |
|---|---|---|---|---|---|---|---|
| $\sigma$ | Density | kg/m³ | 2700 | 2860 | 220 | 1200 | 8960 |
| $C_p$ | Constant Pressure Heat Capacity | J/(kg·K) | 897 | 1150 | 2050 | 1437.4 | 385 |
| $\lambda$ | Thermal Conductivity | W/(m·K) | 240 | 0.4 | 0.025 | 0.4 | 395 |
| $\sigma_s^{eff}$ | Effective Solid Phase Conductivity | S/m | $\sigma_s \epsilon^{1.5}$ | $\sigma_s / \epsilon^{1.5}$ | $\sigma_s$ | $\sigma_s$ | $\sigma_s$ |
Additionally, the properties of SiO2 aerogel are critical for accurate simulation, as shown in the following table:
| Temperature (°C) | Thermal Conductivity (W/(m·K)) | Density (kg/m³) | Specific Heat Capacity (J/(kg·K)) |
|---|---|---|---|
| 20 | 0.020 | 190 | 502.08 |
| 100 | 0.011 | – | – |
| 200 | 0.014 | – | – |
| 300 | 0.016 | – | – |
| 400 | 0.018 | – | – |
| 500 | 0.021 | – | – |
| 600 | 0.026 | – | – |
| 700 | 0.032 | – | – |
| 800 | 0.039 | – | – |
| 900 | 0.049 | – | – |
| 1000 | 0.061 | – | – |
The finite element model was meshed using SOLID185 elements, resulting in 4800 elements and 34,800 nodes to ensure computational accuracy. Simulation results revealed that without the SiO2 aerogel insulation, heat from a short-circuited cell propagated rapidly, reaching adjacent cells and the vehicle interior within seconds. In contrast, with the aerogel layers in place, the temperature rise on the opposite side of the insulation was significantly delayed. For instance, after 300 seconds, the temperature at the center of an adjacent cell with a 3 mm aerogel layer was approximately 355.9°C, representing a 64.4% reduction compared to the unprotected case. Similarly, the exterior surface temperature with a 5 mm aerogel layer was around 130.8°C, an 83.2% decrease. These findings underscore the effectiveness of SiO2 aerogel in enhancing the thermal management of EV power battery systems, particularly in the context of China EV battery applications where safety standards are increasingly stringent.
To validate the simulation results, I conducted experimental tests using SiO2 aerogel毡 samples synthesized via a sol-gel process, followed by aging and CO2 supercritical drying. The aerogel毡 exhibited a nano-porous structure with uniform fiber distribution, as confirmed by scanning electron microscopy (SEM). This structure contributes to its low thermal conductivity and high thermal stability, making it ideal for EV power battery insulation. In the experiments, I installed 3 mm and 5 mm thick SiO2 aerogel layers in a representative battery pack setup and monitored temperature changes under controlled conditions. Initially, tests were performed using a battery system monitoring platform to assess insulation performance at temperatures up to 60°C, with cooling mechanisms activated to prevent damage. For more extreme validation, I used a flame torch to apply a 1000°C heat source to the aerogel surface for 300 seconds, measuring temperature at multiple points on both the heated and opposite sides.
The experimental data closely aligned with the simulation predictions. For example, at the central point of the heated surface, the temperature-time curve from experiments showed a similar trend to the simulation, with a maximum error of 8.9%. On the opposite side, the temperature rise was gradual, reaching about 130°C after 300 seconds, which matched the simulated value within a 7.1% error. This consistency confirms the reliability of the electro-thermal model and the insulation scheme. Moreover, the aerogel毡 maintained structural integrity after repeated heating cycles, demonstrating its durability for long-term use in China EV battery systems. The comparison of different insulation materials further highlights the superiority of SiO2 aerogel, as summarized below:
| Material | Flame Retardant Grade | Thermal Conductivity at Room Temp (W/(m·K)) | Density (kg/m³) | Temperature Range (°C) | Lifespan | Hydrophobicity | Compressive Strength |
|---|---|---|---|---|---|---|---|
| Foam | A | 0.053 | 80-500 | -20 to 120 | Short | Good | Poor |
| Plastic Foam | B1 | 0.015 | 10-1100 | ≤120 | Long | Good | Poor |
| Ultra-Fine Glass Wool | A | 0.038 | 20 | -100 to 450 | Long | Poor | Good |
| High-Silica Wool | A | 0.06 | 90-170 | ≤1000 | Long | Good | Good |
| Vacuum Insulation Panel | A | 0.004 | 160 | -30 to 60 | Short | Good | Poor |
| Aerogel | A | 0.02 | 160-240 | ≤1100 | Long | Good | Good |
In conclusion, my research demonstrates that the integration of SiO2 aerogel-based thermal insulation and flame retardant layers in EV power battery systems significantly enhances safety by delaying heat propagation during thermal runaway events. The numerical simulations and experimental validations confirm that this design can extend the escape time for occupants to over 300 seconds, far exceeding the capabilities of traditional materials. This is particularly relevant for the evolving China EV battery market, where reliability and safety are paramount. The electro-thermal model developed in this study provides a robust tool for optimizing battery designs, and the experimental methods offer practical guidelines for real-world applications. Future work could explore hybrid aerogel composites or scalable manufacturing techniques to further improve the cost-effectiveness and performance of EV power battery insulation solutions.
Overall, the advancements presented here contribute to the broader goal of making electric vehicles safer and more reliable. As the demand for EVs continues to grow, especially in regions like China with ambitious electrification targets, innovations in battery technology will play a crucial role. The use of SiO2 aerogel not only addresses immediate safety concerns but also aligns with sustainability goals due to its eco-friendly properties. By continuing to refine these designs, we can ensure that EV power battery systems meet the highest standards of performance and protection, paving the way for a safer automotive future.