With the continuous advancement of new energy technology, lithium ion batteries are increasingly widely used in electric vehicles, energy storage systems and portable electronic devices. The safety performance of the battery is directly related to the personal safety of users and the stable operation of the equipment. Therefore, the national standard TGB/T 31485 "battery thermal diffusion and safety protection requirements" came into being, aiming at standardizing the battery diffusion behavior and safety protection measures under the condition of thermal runaway, ensure the safe operation of the battery system. This article will introduce the core content, technical requirements and application significance of this standard in detail.

I. Overview of standards

TGB/T 31485 standard mainly aims at the thermal diffusion phenomenon that may occur in the process of thermal runaway of power batteries and their systems, and the corresponding safety protection measures. Thermal diffusion refers to the sharp rise of temperature caused by internal short circuit or external environment abnormality of battery monomer, which in turn causes the temperature rise of adjacent batteries, forming chain reaction, and finally causing safety accidents such as fire or explosion. This standard promotes battery manufacturers to strengthen thermal management and safety design and reduce the risk of battery thermal runaway by clarifying the test methods and limit requirements of thermal diffusion.

II. Thermal diffusion test requirements

1. Test purpose

the core purpose of thermal diffusion test is to evaluate the speed and degree of heat spreading to adjacent batteries under the condition of local thermal runaway, and to judge the overall safety performance of the battery pack. By simulating the situation of monomer thermal runaway, whether the chain reaction caused by thermal diffusion is within the controllable range is detected.

2. Test method

the test usually uses heating or short circuit to induce the thermal runaway of the single battery, monitors whether the high temperature generated by it causes the temperature rise of the adjacent battery, and measures the temperature change curve, time and related parameters. The test environment must be strictly controlled to ensure the accuracy and repeatability of data.

3. Key indicators

• thermal diffusion time: it is defined as the time interval between the temperature of the thermal runaway battery and the adjacent Battery reaching a certain threshold, reflecting the heat propagation speed.
• Peak temperature: assess the severity of thermal diffusion adjacent to the maximum temperature reached by the battery.
• Thermal diffusion trigger probability: in many tests, the frequency of thermal runaway of adjacent batteries reflects the safety and stability of the battery pack.

The standard sets clear limits on the above indexes to ensure that the battery pack can effectively curb thermal diffusion and avoid chain explosion accidents when the heat is out of control.

1. Thermal management system

the standard emphasizes that the battery pack must be equipped with an efficient thermal management system to ensure that the battery temperature is kept within a safe range under normal and abnormal working conditions. The thermal management system can adopt technologies such as liquid cooling, air cooling, phase change materials or thermal conductive materials to improve the heat dissipation efficiency and reduce the risk of thermal diffusion.

2. Security isolation measures

an effective insulation layer or firewall should be set in the design of the battery pack to physically block the diffusion of heat to adjacent batteries. Isolation materials should have good high temperature resistance and flame retardant properties, and can play a key protective role in thermal runaway events.

3. Monitoring and early warning functions

complete temperature monitoring sensors and early warning systems should be configured to monitor battery temperature and abnormal behavior in real time. Once abnormal temperature rise is detected, the system can timely start safety protection measures, such as power failure, cooling or alarm, to prevent accidents from expanding.

4. Battery management system (BMS)

IV. Test equipment and technical means

the TGB/T 31485 standard requires the performance and precision of the test equipment to ensure the scientificity of the thermal diffusion test results. Common equipment includes high-precision thermocouple, infrared imaging devices, environmental temperature control box, etc. During the testing process, the data acquisition system should be used to record the temperature changes in real time to facilitate the analysis of the thermal diffusion law.

In addition, the standard encourages the use of advanced simulation technology to assist testing, predict thermal diffusion behavior through numerical simulation, and optimize battery pack design and protection strategies.

V. Key considerations in standard implementation

1. Test environment control

the test environment temperature, humidity, air pressure and other parameters should meet the standard requirements to avoid interference from external factors on the test results. The stability of environmental conditions is the premise to ensure the validity of test data.

2. Sample preparation and selection

the tested battery pack shall represent the typical configuration and status of the actual application, including the complete protection system. The manufacturing process and State of the sample directly affect the accuracy of the test results.

3. Multiple tests and data statistics

in order to ensure the reliability of data, the standard requires repeated tests to count the triggering probability of thermal diffusion and related parameters, eliminate incidental errors, and improve the representativeness of test conclusions.

VI. Application significance

the implementation of TGB/T 31485 standard is helpful to promote battery manufacturing enterprises to strengthen thermal safety design, improve safety detection system and improve the safety performance of battery products. By standardizing thermal diffusion and safety protection requirements, the risk of accidents caused by battery thermal runaway is reduced, and the safety of users' lives and property is guaranteed.

In addition, the standards provide scientific safety assessment basis for relevant regulatory agencies and promote the healthy and orderly development of the industry. For battery system integrators and end users, selecting and accepting products according to this standard can also effectively improve the level of safety assurance.

TGB/T 31485 battery thermal diffusion and safety protection requirements are the guarantee important technical specifications for safety performance. It systematically controls and reduces the chain diffusion risk of battery thermal runaway by clarifying thermal diffusion testing methods and safety design requirements. The standard covers multi-level security measures from thermal diffusion testing to thermal management, isolation protection, monitoring and early warning, providing solid technical support for battery safety.