What is the Way to Ensure the Safety of New Energy Vehicle Batteries?-Lithium Battery Ventings Manuafcturer
The safety of electric vehicles is primarily concerned with whether they will catch fire or self-ignite. This involves the thermal runaway problem of vehicle batteries. The way to ensure the safety of new energy vehicle batteries is to find the cause of battery thermal runaway and how to prevent it. In this article, we will introduce the thermal runaway of lithium batteries.
What is Thermal Runaway of Electric Vehicle?
- Overview
Thermal runaway refers to a chain reaction of heat caused by various factors. Heat accumulates inside the battery and reinforces each other with extremely destructive reactions.
Put, thermal runaway is a positive feedback loop of energy: the rising temperature causes the system to heat up, and the system heats up, and the temperature rises, which in turn makes the system hotter, eventually causing a fire or explosion.
- Stage division
When it comes to classifying thermal runaway stages, there are varied opinions. The prevailing perspective highlights the importance of the diaphragm, which serves as the primary barrier separating the positive and negative electrodes within the battery cell. If the diaphragm deteriorates widely, it can lead to internal short-circuiting between the positive and negative electrodes, intensifying the battery cell’s thermal runaway reaction. Initially, a drop in temperature reduces material activity and slows down the reaction. However, once a certain threshold is crossed, the direct interaction between the positive and negative electrodes impedes the reduction of the battery cell’s internal temperature, hindering the reaction from ceasing.
This theory divides thermal runaway into three stages: the self-heating stage (50℃-140℃), the thermal runaway stage (140℃-850℃), and the thermal runaway termination stage (850℃-normal temperature). Some literature provides that the large-scale melting temperature of the diaphragm starts at 140℃.
Causes of Thermal Runaway in Electric Vehicle
The causes of thermal runaway can be divided into two categories: internal and external.
Internal Cause
- Internal Short Circuit
Based on the previous analysis, it has been determined that all thermal runaways are ultimately triggered by the melting of the diaphragm. Leading to an internal short circuit between the positive and negative electrodes of the battery cell, consequently resulting in the thermal runaway of the battery cell. The cause of the internal short circuit is a specific issue. During equipment processing, metal substances can inadvertently enter the battery cell, leading to the piercing of the diaphragm and causing an internal short circuit. For instance, the current standard diaphragm thickness ranges from 6 to 12μm. If metal particles exceed this thickness during repeated charging, they can puncture the diaphragm, causing an internal short circuit in the battery cell, thereby leading to thermal runaway.
External Cause
- Mechanical Abuse
Mechanical abuse refers to the situation where the battery cell is affected by external forces such as collision, extrusion, and puncture. For example, foreign objects touched by a vehicle at high speed directly lead to the collapse of the battery diaphragm, which in turn causes a short circuit in the battery and spontaneous combustion in a short period.
- Electrical Abuse
The electrical abuse of lithium batteries generally includes external short circuits, overcharging, and over-discharge. Among them, overcharging is the most likely to develop into a thermal runaway.
- Overcharge
overcharge is mainly due to the uncontrolled charging or repeated charging of the battery pack. The negative electrode of the battery cell has no space to continue to hold lithium metal. It will form lithium dendrites, causing the diaphragm to be punctured and causing thermal runaway of the battery pack. This is also one of the most important factors of loss of control in the early development of the lithium battery industry.
- External Short Circuit
The external short circuit of the battery pack may be caused by deformation caused by car collision, short circuit of positive and negative electrodes, water immersion, conductor contamination, or electric shock during maintenance, etc. Generally speaking, as long as the external short circuit does not directly act on the battery pack and cause the high-voltage positive and negative electrodes inside the battery pack to directly short-circuit, it can be eliminated by the product’s insurance system to avoid thermal runaway of the battery pack.
- Thermal Abuse
Local overheating may be a typical thermal abuse situation that occurs in the battery pack. Thermal abuse rarely exists independently. It often develops from mechanical abuse and electrical abuse, and is the final direct trigger of thermal runaway. In addition to overheating caused by mechanical/electrical abuse, overheating may be caused by loose connection contact. The problem of loose battery connection has been confirmed. Thermal abuse is also the most simulated situation at present, using equipment to control the heating of the battery to observe its reaction during the heating process.
Hejustamping-Prismatic Battery Stamped Components Manufacturer
Dongguan Heju Precision Electronic Technology Co., Ltd. is a leading stamping manufacturer in China. Specializing in the production of prismatic lithium battery safety ventings for new energy vehicles. As one of the earliest companies in China to develop and produce these battery vents, we have a wide range of models and specifications, with a single unit pressure range of up to 0.03MPA. Our CPK>2.0. We work closely with customers in product development and have passed the three major certification systems: ISO9001, ISO14001, and IATF16949.