百层之上，锂电焊接工艺走到哪一步了？

Core Viewpoint - Welding is transitioning from a backend process to a front-line capability in lithium battery manufacturing, significantly impacting internal resistance, temperature performance, yield stability, and production costs [2][3]. Group 1: Current Challenges in Welding Technology - The mainstream welding methods for multi-layer current collectors and covers typically use a "three-step" or "two-step" process, which is becoming less viable as cell capacities increase and layer counts rise [3][4]. - Traditional welding processes are revealing issues such as lengthy procedures, accumulated defects, and increased difficulty in stability control, particularly as the number of layers continues to rise [5][6]. Group 2: Technical Aspects of Pressure Melting Welding - Pressure melting welding seeks to balance heating and pressure to achieve atomic bonding by breaking down surface layers, with a focus on high energy density and controllability [6][7]. - This method involves simultaneous application of pressure and electrical current, utilizing the Joule effect for localized melting, which distinguishes it from traditional resistance welding [6][7]. Group 3: Performance and Validation of Pressure Melting Welding - In tests involving over a hundred layers, pressure melting welding achieved stable welds without splatter or defects, with mechanical strength exceeding the industry standard of 120N and a peel residual rate of 100% [9][10]. - The process demonstrated a peak temperature rise of less than 100°C during welding, ensuring minimal thermal risk to surrounding components [9][10]. Group 4: Innovations and Future Applications - Pressure melting welding is not only applicable to multi-layer current collectors but also enhances existing two-step or three-step production lines by reducing debris generation [10]. - The technology is adaptable for lightweight and miniaturized designs, and it offers new manufacturing possibilities for dissimilar metal welding, which is crucial as the industry shifts towards manufacturing capability-driven innovations [10].