Deconvolution of capacitive and diffusive charge/lithium storage in lyophilized NiCo₂S₄–NiCo₂O₄ composite for supercapattery and lithium-ion battery

Abstract

In this work, spinel-type metal sulfide/oxide (NiCo2S4-NiCo2O4) composite where the NiCo2S4-NiCo2O4 anchored on graphene oxide was synthesized by a simple freeze-drying method has been explored as electrode for both supercapattery...

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

“…As the C-rate increases, it is clear that the discharge capacity gradually deteriorates, as has been observed . This is due to the difficulty of the electrolyte ions to readily migrate into the electrode material because the active material utilization is restricted at higher current densities, resulting in capacity fading . Interestingly, at each C-rate, the cathode shows an almost similar discharge capacity in the studied cycles, implying a high rate capability as well as reversibility.…”

“…3 This is due to the difficulty of the electrolyte ions to readily migrate into the electrode material because the active material utilization is restricted at higher current densities, resulting in capacity fading. 17 Interestingly, at each C-rate, the cathode shows an almost similar discharge capacity in the studied cycles, implying a high rate capability as well as reversibility. The initial discharge capacity of the Li−S battery is observed to be 1180 mA h g −1 at 0.02 C-rate, and when switched back to the 0.02 Crate after being subjected to various C-rates, the capacity is almost restored, implying the high reversibility and rate capability of the ZIF-Co@NCS cathode sulfur host.…”

“…Using the Power law, it is possible to qualitatively state whether the charge storage in an electrode is dominated by the capacitive-type or the diffusive-type process from the current response of a CV profile recorded at different scan rates. According to the Power law, the peak current response of a CV profile is related to the scan rate, as shown below 17,35…”

“…Using the Power law, it is possible to qualitatively state whether the charge storage in an electrode is dominated by the capacitive-type or the diffusive-type process from the current response of a CV profile recorded at different scan rates. According to the Power law, the peak current response of a CV profile is related to the scan rate, as shown below , i peak ( V ) = a ν b goodbreak0em1em⁣ or goodbreak0em1em⁣ log ( i peak ) = log ( a ) + b nobreak0em0.1em⁡ log ( ν ) where i peak represents the response of the peak current observed in the CV curves, ν is the scan rate, and a and b are two parameters that could be obtained by mathematical operation. The value of parameter b gives insights into the Li + charge storage kinetics: if the value of parameter b is ∼0.5, it is considered that the mode of charge storage is dominated by diffusion-limited processes (Faradaic), whereas parameter b ∼ 1 indicates the capacitive dominance due to surface electrosorption.…”

“…As the tendency of elemental cobalt to attract ‘S’ is pronounced, having cobalt along with the MOF porous carbon would facilitate polysulfide trapping, which is desirable for a better-performing cathode sulfur host. Freeze-drying is a facile and effective method that is used in the synthesis of functional materials and offers benefits for designing the desired morphology as well as surface features. , This synthetic route does not require harsh conditions such as high temperature or high pressure or the use of other specific reagents during the synthesis. As far as we know, currently, there are no reports on the synthesis of ZIF-Co@NCS composites using the freeze-drying technique for Li–S batteries.…”