Superior stability and electrochemical performance of Li2ZnTi3O8 anode enabled by the derivatives from the isomers of trithiocyanuric acid

Abstract

Rechargeable Li-ion batteries with fast-charging performance, long cycle life and safety are desirable. Herein, an efficient hydrothermal avenue was adopted to modify Li2ZnTi3O8 (LZTO) with trithiocyanuric acid (TCA). The two isomers of keto and enol TCA undergo different evolutions in the hydrothermal and electrochemical processes. For the enol TCA in the hydrothermal process, the HS– bonds close to LZTO react with LZTO to introduce superficial S-doping to facilitate electron conductance, and the others oxidize into –SO3– groups which transform into –SO3Li groups in lithiation process to favor Li+ migration. The keto TCA is stable in the hydrothermal process, yet the CS groups oxidize into –SO3– groups in anodic process and yield –SO3Li groups in subsequent cathodic process for Li+ diffusion. Despite these changes, the six-membered cyclic structures in both the keto and enol TCA are stable and coordinate with LZTO to create coating layer. The organic coating with good mechanical performance and strong interaction with PVDF protects LZTO from electrolyte corrosion and side reactions. Therefore, the TCA-modified LZTO demonstrates accelerated Li-ion migration and electron transfer, significantly enhanced rate capability and cycling stability.