1. The meaning of infinite loop
Traditional tab design: Current is drawn out of the positive and negative terminals of the battery by welding one or more metal tabs. Typically, a traditional cylindrical battery (such as an 18650) has one positive and one negative tab.
The current path is long, and the internal resistance is high;
Excessive local current density makes thermal management difficult.
Tabletless (full tab) design: Eliminates the separate tab structure and directly uses the entire circumferential edge of the blank area of the current collector (aluminum foil or copper foil) of the positive/negative electrode as a conductive channel, saving the tab welding process.
Core mechanism: Current is transmitted laterally through the current collector, rather than flowing longitudinally to a single tab point.
Results: Effective conduction area increased by 10-20 times, and internal resistance decreased by more than 54% (Tesla 4680 data).
2. Structural characteristics of tabless large cylindrical batteries
Size advantage: Typical specifications are 46mm in diameter and 80mm or larger in height (such as Tesla 4680 and CATL's planned 4695), and each unit can store higher energy (about 21-30Ah).
Electrode Design: The blank areas of the positive and negative electrodes are formed into continuous conductive surfaces through laser etching or ultrasonic flattening processes, eliminating the need for die-cut electrode tabs.
Cell connection method: The positive aluminum foil end face is directly connected to the top cover, and the negative copper foil end face is connected to the shell.
3. Core advantages of tabless design
Low internal resistance and high rate performance:
The current path is shortened by 60%-80% (in traditional designs, the current needs to flow through the length of the tabs; the internal resistance of the Tesla 4680 is reduced to 1.45mΩ).
Supports 6C-9C fast charging (capacity retention rate ≥90%).
Improved heat dissipation and safety:
More even heat distribution, reducing circulating temperature rise by 15-20℃;
It is compatible with full life cycle thermal monitoring to delay thermal runaway.
Manufacturing efficiency and economy:
Eliminate the tab welding process (reduce costs by 20%);
Simplify the requirements for electrode alignment accuracy;
Production efficiency increased by 7 times (Tesla dry electrode technology combined with tabless process).
4. Technical Challenges and Solutions
Flattening process control: The edges of the electrode sheet need to be precisely flattened (pressure 100-300N) to ensure the flatness of the conductive surface. This is achieved through laser online detection combined with servo closed-loop feedback control.
Electrolyte wetting optimization: The full tab design increases the interface between the electrode edge and the diaphragm, requiring an increase in the injection vacuum (≤-95kPa) and an extension of the impregnation time (≥24h).
Interface contact resistance: By filling the gap between the electrode and the top cover with conductive adhesive (such as silver-containing epoxy resin), the resistance is reduced by 30%-50%.
Summarize
The tabless cylindrical battery, through its innovative all-tab design, replaces the traditional welded tabs with direct current conduction of the current collector, significantly improving power density, production efficiency, and safety. It represents the core technology direction for the next generation of high-energy-density power batteries.
