Low-Resistance Mechanism of Nanoflake Crystalline Aromatic Dicarboxylates with Selective Defects for Safe and Fast Charging Negative Electrodes.

Low resistance of Li-intercalated negative electrodes is important for the safe and fast charging required for large-scale batteries. Here, we demonstrated that nanosized two-dimensional crystalline aromatic dicarboxylate negative electrode materials synthesized spray drying exhibit low internal resistances at approximately 0.7 V Li/Li, while retaining flat potential profiles. The spray-dried sample with a hollow structure is crushed into nanoflakes during ink preparation for electrode coating and forms a uniform and highly dispersed electrode structure. The charge-discharge evaluation indicates that the nanoflake sample showed smaller charge-discharge polarization than the bulk sample with stable cycling characteristics, resulting in significant high-rate property enhancement. Charge-transfer resistance of the nanoflake sample exhibits the lowest value ( 2.2 Ω cm) among those reported for existing intercalation electrodes (5.2 to 235 Ω cm). In comparison of the negative electrodes, the estimated maximum current density without Li deposition ( 316 mA cm) is more than 1 order of magnitude higher than that for currently used graphite ( 11 mA cm) and is also higher than those for high-rate oxides (137-298 mA cm). The resistance-crystal correlation using multiple regression analysis predictions and its verification reveal that this low resistance is owing to an improved Li acceptability associated with selective structural defects induced by the loss of incorporated crystallized water during drying. The crystal plane exposed by the selective structural defects is perpendicular to electronic and ionic conduction directions inside the solid, resulting in improved kinetics. Therefore, the proposed negative electrode allows safe and fast charging, with easy scale-up and sustainable resources.