Freeze-Drying-Assisted ZIF-67 Template-Derived Co@NCS Porous Composite as Sulfur Cathode Host for Improved Li–S Battery Performance: Deconvolution of Diffusive and Capacitive Li⁺ Storage

Abstract

A zeolitic imidazole framework (ZIF-67) templatederived cobalt@nitrogen-doped carbon−sulfur composite (ZIF-Co@ NCS) was synthesized using a freeze-drying method and explored for lithium−sulfur (Li−S) batteries. Material characterizations confirmed the formation of the ZIF-Co@NCS composite. To fabricate the Li−S battery in a coin-type CR-2032 cell, the as-synthesized ZIF-Co@NCS composite having a sulfur content of ∼65% was used as a cathode material and coupled with a lithium metal anode. This battery demonstrated exceptional cycling stability over 600 charge−discharge cycles with a steady capacity of 550 mAh g −1 at 0.05 C-rate. The good electrochemical performance of the cathode was ascribed to the nanofeatures associated with the freeze-dried porous carbon structure, which offered enough space for the sulfur cathode. The enhanced trapping of polysulfide facilitated by the presence of the Co−N sites in the ZIF-Co@NCS composite led to excellent cycling stability. The derived cathode composite showed a high specific capacity, outstanding rate capability, and excellent cyclic stability rendering it a promising candidate for high-performance Li−S batteries. Detailed Li + ion charge storage examined by means of Dunn's method revealed a significant capacitive mode of charge storage both at peak currents and nonpeak currents. The post-mortem analysis of the cycled cathode using X-ray diffraction and scanning electron microscopy at different depth-of-discharge (DOD) values revealed the stepwise formation of discharge products.

Sea Urchin-Like NiO-CoO Heterostructure as High-Energy Supercapattery Electrode: Laboratory Prototype to Field Application of Pouch-type Device

“…They can be fitted to the equivalent circuit shown in the inset of Figure S8. It is observed that the shunt resistance ( R s ) and charge transfer resistance ( R ct ) values increased after conducting the cycle life analysis, implying a bit degradation of the electrode and electrolyte, as generally reported in the literature . The low R ct value observed indicates the smooth charge transfer reaction facilitated by the sea-urchin like NiO-CoO heterostructure electrode.…”