Power Battery Manufacturing Process: Laser Welding Technology Explained

Against the backdrop of the rapid development of the new energy vehicle industry, the manufacturing quality of power batteries, as a core component of the vehicle, directly affects the vehicle's safety, cycle life, and energy density. Power battery systems typically consist of cells, battery modules, and battery packs (PACKs). Their internal structure involves numerous metal material connections, including electrode tabs, conductive connecting pieces, battery casings, and encapsulation structures. Among these critical connection links, laser welding, with its high energy density, non-contact processing, and high automation adaptability, has gradually become one of the important processes in power battery manufacturing. Especially in aluminum alloy casing structures, such as Battery Aluminum Housing or Prismatic Cell Cases, laser welding can achieve high-precision sealed connections, providing a stable and reliable encapsulation environment for the battery's interior.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The manufacturing process of power batteries typically includes multiple stages, such as cell production, mid-stage assembly, and back-end PACK integration. In these stages, laser welding is widely used in key processes such as tab welding, electrode spot welding, cell pre-welding, casing and top cover sealing welding, and liquid injection port sealing. Meanwhile, in the downstream module and PACK assembly stage, processes such as connecting piece welding, explosion-proof valve welding, and battery terminal welding also need to be completed. These structures are often directly integrated into structural components such as aluminum alloy prismatic battery cases or aluminum shells for lithium ion battery cells. Therefore, welding quality plays a decisive role in the battery's sealing performance, structural strength, and thermal stability.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In the cell structure, the sealing welding between the battery casing and the cover plate is one of the most critical manufacturing steps. Power battery casings are typically made of 3003 series aluminium alloy, with a thickness generally controlled between 0.6 and 0.8 mm. High-quality welds between the casing and the cover plate can be achieved through low-power pulsed laser welding, thus forming a stable, sealed space. For prismatic cells, this structure is typically represented as a prismatic cell aluminium shell or an aluminium shell for a prismatic lithium-ion battery. In actual production, welding defects mainly include incomplete penetration, porosity, and weld collapse. These defects directly affect the sealing performance and pressure resistance of the battery casing, thereby affecting battery life and safety performance. Battery terminal welding is a crucial connection structure for current conduction in power batteries. Terminals are generally divided into positive and negative electrodes, with the positive electrode typically made of aluminium and the negative electrode of copper.

 

Multiple cells can be connected in series or parallel using welding connectors to form a complete battery module. Terminals are usually integrated with the battery cover and installed in the top structure of the lithium cell aluminium shell or the lithium cell battery aluminium shell. In actual welding, terminal welding is prone to defects such as pores, mainly due to the small diameter of the welding area and the tendency for impurities such as stamping oil or cleaning agents to remain. Under high-energy-density laser irradiation, these impurities rapidly vaporise to form bubbles, which escape and create weld voids. Therefore, pre-welding cleaning and laser power curve optimisation are particularly important.

 

Explosion-proof valve welding is an important component of the safety structure of power batteries. Explosion-proof valves are usually installed on the battery cover, and their function is to actively rupture and release pressure when the internal pressure of the battery abnormally increases, thus preventing battery explosion accidents. Explosion-proof valves are typically constructed from two layers of aluminium sheets laser-welded together, with their detonation pressure usually controlled between 0.4 and 0.7 MPa. This structure is often integrated into the packaging of New Energy Vehicle Aluminium Battery Cases or Battery Packs with Aluminium Housings, thus requiring extremely strict control over weld sealing and heat input. Excessive or insufficient welding energy can lead to unstable trigger pressures in the explosion-proof valve, affecting the overall safety performance of the battery.

 

During battery module manufacturing, adapter welding is a crucial process connecting the battery cell to the cover plate. The adapter not only needs good conductivity but also must withstand significant current loads and mechanical stresses. In practical designs, the adapter is typically welded to a Deep Drawn Aluminium Battery Housing or Pack Aluminum Housing, forming a stable connection with the cell's tabs. Because copper has low laser absorption and high reflectivity, higher energy density is required during copper-aluminium dissimilar metal welding to ensure weld penetration and bond strength. Simultaneously, strict control of spatter is necessary to prevent particles from entering the battery cell and causing short circuits.

 

In power battery pack systems, the welding quality of battery modules directly affects the current uniformity and thermal management performance of the entire system. A battery module consists of multiple cells connected in series and parallel, and also requires a battery management system (BMS) for monitoring and protection. In this complex structure, welding of connecting pieces typically requires high-power laser equipment to achieve stable welding of thick copper or aluminium materials. For example, in large-scale energy storage systems or new energy vehicle packs, the connecting structure is usually installed within the structural framework of an aluminium shell for lithium iron phosphate cells or an aluminium shell for a prismatic lithium ion battery to ensure the structural strength and electrical reliability of the module.

 

Although laser welding has significant advantages in power battery manufacturing, several technical challenges remain in the welding of aluminium alloy materials. First, there is the issue of porosity. Due to the high solubility of hydrogen in the molten aluminium alloy pool, hydrogen pores are easily formed during rapid solidification. Furthermore, pinhole collapse during laser welding can also create porosity defects. Second, there is the issue of hot cracking. Since aluminium alloys are typical eutectic alloys, grain boundary liquefaction cracks are prone to occurring during welding cooling, thereby reducing the strength of the weld joint. These problems are particularly common in the welding of critical structural components such as aluminium shells for lithium-ion battery cells or aluminium alloy prismatic battery cases.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Another common defect is welding spatter, also known as "splatter." This phenomenon is usually caused by surface contamination of materials, excessively high laser energy density, or insufficient laser beam stability. When there are pores or protrusions on the material surface in the welding area, the high-energy laser can rapidly cause localised evaporation, resulting in metal spatter. For battery modules installed in prismatic cell aluminum shells or battery aluminium housing structures, spatter entering the cell can lead to insulation failure or short circuit risks. Therefore, in actual production, spatter problems need to be reduced by optimising laser parameters, improving material cleanliness, and properly controlling the spot size.

 

Welding processes also differ in different battery structures. For example, in the tab welding process of pouch batteries, special tooling is needed to press the tabs tightly to ensure a stable welding gap, thereby achieving an S-shaped or spiral welding trajectory. For cylindrical batteries, welding is mainly concentrated in the positive electrode connection area because the negative electrode shell is thinner and prone to burn-through. Prismatic batteries primarily employ a shell-and-cap encapsulation welding method, typically divided into top-welded and side-welded structures. Side-welded methods reduce the risk of spatter entering the cell, but require higher standards of material cleanliness and equipment stability. Top-welded methods are more suitable for mass production, but require more precise shell processing techniques. These welding structures are commonly used in battery casing structures, such as aluminium shells for prismatic lithium-ion batteries or new energy vehicle aluminium battery cases.

 

Overall, with the development of new energy vehicles and energy storage industries, power battery manufacturing is evolving towards higher precision, automation, and intelligence. Laser welding technology, with its advantages of high efficiency, low heat impact, and applicability to complex structures, has become a key manufacturing process in power battery production. From cell packaging to module assembly and PACK system integration, laser welding technology runs through the entire manufacturing process and forms a high degree of synergy with key structural components such as lithium cells, aluminium shells and battery packs with aluminium housings.

 

 

In the power battery manufacturing process, high-quality battery casings not only need excellent material properties but also need to be able to adapt to precision welding processes. Our company specialises in the research, development and manufacturing of structural components for new energy batteries, providing a variety of high-precision battery housing solutions, including Deep Drawn Aluminium Battery Housing, Prismatic Cell Case, and Aluminum shells for lithium-ion battery cells. These components are made of high-strength aluminium alloy and manufactured through precision stamping and deep drawing processes, meeting the stringent requirements of power batteries in terms of sealing, structural strength, and weldability.

 

Our products are widely used in new energy vehicle power battery systems, energy storage battery systems, and high-performance battery modules, providing customers with reliable Battery Aluminium Housing and Pack Aluminium Housing solutions to help improve the safety and manufacturing efficiency of battery systems.