Optimizing Current Terminals of 18650 Lithium-Ion Power Batteries under High Discharge Current

摘要

Nowadays, technology for the fabrication of batteries is critical in determining cell durability, especially for 18650 power batteries. We report herein on the design of three types of electrode tabs serving as the current terminals of 18650 full cells, including: one, the most common configuration in which one positive tab is located opposite to the negative tab; two, the more common configuration in which one positive tab is located in the middle, whereas the negative tab is located at the end; three, the optimal configuration in which two negative tabs are in parallel, whereas one positive tab is located in the middle. Among them, batteries with the type 3 tab configuration, owing to the smallest ohmic resistance, exhibit superior capacity retention of approximately 86% at a discharge current of 7C, which is much better than batteries with the common tab configuration (only 47%). Besides, the optimized batteries could effectively suppress the decomposition of the electrolyte and loss of lithium from the cathode materials, which enabled excellent long-term cycling stability (approximate to 91% capacity retention over 1000 cycles). The electrochemical degradation mechanism was also investigated. After the cycling test, the batteries with the optimal tab configuration showed the lowest increase in the impedance, the slightest cracks of the cathode materials, and the best structure integrity of the graphite anode than the two other counterparts.