In a fully automatic lithium battery pack assembly line, the temperature uniformity of the hot-pressing process directly affects the battery's energy density, cycle life, and safety performance. Uneven temperature distribution can lead to poor bonding between the electrode and separator interfaces, and localized overheating may cause material decomposition or short circuit risks, while excessively low temperatures prevent effective bonding. Therefore, achieving precise temperature control in the hot-pressing process through multi-dimensional technical means is crucial for ensuring the efficient operation of a fully automatic lithium battery pack assembly line.
The temperature control system of the hot-pressing equipment is fundamental. Modern fully automatic lithium battery pack assembly lines employ high-precision heating plates and multi-point temperature monitoring technology. Embedded sensors collect real-time temperature data from the heating area, and PID control algorithms dynamically adjust the heating power. For example, the equipment can arrange a dense array of thermocouples inside the heating plate to control temperature fluctuations within ±0.5℃. Simultaneously, some high-end equipment incorporates infrared thermal imaging technology to perform non-contact scanning of the cell surface temperature, forming a three-dimensional temperature field distribution map, providing data support for process parameter optimization.
The coordinated control of pressure and temperature is a key breakthrough. During the hot-pressing process, pressure distribution directly affects temperature conduction efficiency. The fully automated assembly line achieves precise matching of pressure-temperature curves through the linkage of a servo pressure control system and a temperature module. For example, a low-temperature, low-pressure mode is used in the initial pressurization stage to allow the binder to melt slowly; after entering the pressure holding stage, the temperature and pressure are increased simultaneously to promote deep bonding between the electrode and the separator. This staged control strategy avoids temperature distortion caused by localized stress concentration, ensuring uniform heating of the entire cell.
Optimized preheating technology significantly improves initial temperature consistency. The fully automatic lithium battery pack assembly line is equipped with a tunnel-type preheating furnace before hot pressing, using hot air circulation or contact heating methods to ensure that the cells reach the preset temperature range before entering the hot pressing station. The preheating furnace's interior uses a baffle design to create laminar airflow, eliminating temperature dead zones; simultaneously, a variable frequency fan dynamically adjusts the airflow speed according to the cell size, ensuring a preheating accuracy of ±2℃ for products of different specifications. This pretreatment method significantly shortens the hot pressing cycle and reduces the final temperature difference caused by differences in the initial temperature of the cells.
Material compatibility technology is customized for different battery systems. For high-nickel ternary lithium batteries, the assembly line employs a low-temperature hot-pressing process, controlling the upper temperature limit below 90℃ to prevent nickel precipitation. Lithium iron phosphate batteries, on the other hand, can enhance interfacial bonding strength by increasing the hot-pressing temperature to 100℃. Furthermore, for high-expansion materials such as silicon-based anodes, the equipment incorporates a dynamic pressure compensation system, adjusting the pressure in real-time based on material volume changes during hot pressing to prevent localized temperature increases caused by material shrinkage.
An intelligent monitoring system enables full-process traceability and closed-loop control. The fully automatic lithium battery pack assembly line integrates a Manufacturing Execution System (MES) to collect and store temperature, pressure, and time parameters for each hot-pressing station in real time. Through a big data analytics platform, historical batch data can be traced, temperature fluctuation patterns identified, and process optimization suggestions automatically generated. For example, when the system detects that the edge temperature of three consecutive batches of cells is too low, it triggers an alert and adjusts the heating plate zone power, forming a closed-loop control chain of "monitoring-analysis-adjustment."
Innovative design of the hot-pressing mold further eliminates edge effects. Traditional flat-press molds tend to cause pressure and temperature attenuation at the cell edges, while new curved-surface molds optimize the curvature of the contact surface, resulting in more uniform pressure distribution. Simultaneously, the mold surface undergoes a nano-coating treatment to improve heat conduction efficiency and reduce temperature gradients caused by differences in thermal resistance between the mold and the cell. Some leading companies have also developed segmented molds, implementing differentiated hot-pressing strategies for different areas of the cell to achieve precise zoned temperature control.
From the equipment level to the system level, the fully automatic lithium battery pack assembly line, through the synergistic effect of improved hardware precision, optimized process strategies, adapted material properties, and intelligent management, constructs a multi-dimensional temperature uniformity assurance system. This systematic solution not only improves the consistency of battery products but also lays the technological foundation for the large-scale production of high-energy-density, high-safety lithium batteries. With the advancement of research and development of new cell systems such as solid-state batteries, temperature control technology in the hot-pressing process will continue to evolve towards higher precision and greater adaptability.
