Optimizing Current Terminals of 18 650 Lithium‐Ion Power Batteries under High Discharge Current

Nowadays, battery fabrication technology is critical in determining the cell durability especially for 18650 power batteries. We report here to design three types of electrode tabs serving as the current terminals of 18650 full cells, including: i) the most common way that one positive tab located counter to the negative tab; ii) the more common way that one positive tab located in the middle while the negative tab located at the end; iii) the optimal way that two negative tabs in parallel while one positive tab located in the middle. Among them, the batteries with type iii tab configuration, owning the smallest ohmic resistance, exhibit superior capacity retention of ~86% at 7 C discharge current, much better than the ones with common tab configuration (only 47%). Besides, the optimized batteries can effectively suppress the decomposition of the electrolyte and the lithium loss of the cathode materials, enabling excellent long-term cycling stability (~91% capacity retention over 1000 cycles). The electrochemical degradation mechanism is also investigated. After the cycling test, the batteries with optimal tab configurations show the lowest impedance rise, the slightest cracks of the cathode materials, and the best structure integrity of the graphite anode than the other two counterparts.