Battery pack connection wire: Detailed explanation of magnesium hydroxide anti thermal runaway diffusion test

With the rapid development of the new energy vehicle industry and the widespread application of high-energy density batteries, how to effectively prevent the spread of thermal runaway has become a core issue in battery system design.

1、 What is thermal runaway? Why is it necessary to prevent its spread?

Thermal runaway refers to the process in which the temperature inside a battery rises sharply due to factors such as short circuits, overcharging, mechanical damage, or high temperatures, triggering a chain reaction and releasing a large amount of heat and gas. Once thermal runaway occurs, it can not only cause damage to individual batteries, but also quickly affect the entire battery module or even the entire battery pack, and in severe cases, can lead to fire or explosion.

Therefore, in battery system design, in addition to improving the stability of the battery cells themselves, it is also necessary to suppress the propagation path of thermal runaway through structural design, material selection, and other methods to ensure the safety of the entire vehicle.

2、 Analysis of flame retardant properties of magnesium hydroxide

Magnesium hydroxide (Mg (OH) ₂), as a common inorganic flame retardant, has been widely used in the fire protection design of battery systems in recent years due to its excellent flame retardant performance, environmental friendliness, and good thermal stability.

1. Flame retardant mechanism

Magnesium hydroxide absorbs a large amount of heat and releases water vapor during thermal decomposition:

Mg(OH)2→MgO+H2OMg(OH)2→MgO+H2O

This process has the following characteristics:

·Heat absorption and cooling: reduce local temperature and delay the spread of thermal runaway;

·Generating water vapor: diluting the concentration of combustible gases and suppressing combustion;

·Formation of magnesium oxide layer: Covering the surface of the material, it plays a role in insulation and oxygen barrier.

2. Environmental advantages

Compared with halogenated flame retardants, magnesium hydroxide does not release toxic gases during combustion, which meets the dual requirements of environmental protection and safety for current new energy vehicles.

3、 Application background of magnesium hydroxide in battery pack connecting wires

The battery pack connecting wire is an important electrical connecting component between battery modules, usually using copper or aluminum bars as conductor materials. Because it is between battery modules, once a module is out of control, this area is very easy to become a "bridge" for heat conduction, accelerating the diffusion of heat loss in the entire battery pack.

To solve this problem, more and more battery manufacturers are introducing flame-retardant materials around the connecting wires, among which magnesium hydroxide has become one of the ideal choices due to its excellent thermal stability and flame retardant properties.

The specific application methods include:

·Wrap a composite flame retardant layer containing magnesium hydroxide outside the connecting wire;

·Add magnesium hydroxide to the plastic material of the connecting wire bracket or fixture;

·Fill the connection channels between battery modules with magnesium hydroxide based fire-resistant material.

4、 Detailed explanation of magnesium hydroxide anti thermal runaway diffusion testing method

To verify whether magnesium hydroxide can effectively delay the diffusion of thermal runaway in battery connection lines, a series of simulation tests are required. The following are typical testing processes and evaluation metrics:

1. Test objectives

·Verify the thermal response characteristics of magnesium hydroxide material at high temperatures;

·Evaluate its barrier effect on thermal runaway flames and high-temperature gases;

·Compare the thermal diffusion rate between using and not using magnesium hydroxide material.

2. Testing equipment and conditions

·Heating device: Simulate the high-temperature environment caused by thermal runaway;

·Thermal imaging instrument: real-time monitoring of temperature changes;

·Gas detector: Analyze the gas components released during the combustion process;

·Data acquisition system: records key parameters such as temperature, time, pressure, etc.

3. Testing steps

1. Sample preparation: Prepare connecting wire components separately with magnesium hydroxide flame retardant material and without flame retardant material;

2. Initial state recording: Measure and record physical parameters such as initial temperature and impedance of the sample;

3. Heat source application: Apply heat to one side of the sample under simulated thermal runaway conditions;

4. Observation record: Record the time curve of temperature changes on the other side;

5. Result comparison: Compare the differences between the two samples in terms of thermal conductivity rate, peak temperature, etc.

4. Analysis of Test Results

Experimental data shows that the connecting wire components made of magnesium hydroxide material exhibit better thermal insulation capacity in thermal runaway simulation tests

·The rate of temperature rise has significantly slowed down;

·The peak temperature was about 30% lower than the control group;

·The flame propagation distance is shortened;

·The concentration of combustible gases has significantly decreased.

These data fully demonstrate that magnesium hydroxide can indeed play an effective role in fire prevention and flame retardancy in battery connection wires.

At present, some new energy vehicle companies have introduced magnesium hydroxide flame retardant technology in their battery systems, especially in high-end models or long-range versions.

In the future, with the further improvement of battery energy density and the development of fast charging technology, thermal management and fire protection design will become the top priority in battery system engineering. Magnesium hydroxide, as a green and efficient flame retardant material, will play a role in more application scenarios.