Observation of Pseudocapacitive Effect and Fast Ion Diffusion in Bimetallic Sulfides as an Advanced Sodium‐Ion Battery Anode

Abstract

Sodium‐ion batteries (SIBs) are promising next‐generation alternatives due to the low cost and abundance of sodium sources. Yet developmental electrodes in SIBs such as transition metal sulfides have huge volume expansion, sluggish Na+ diffusion kinetics, and poor electrical conductivity. Here bimetallic sulfide (Co9S8/ZnS) nanocrystals embedded in hollow nitrogen‐doped carbon nanosheets are demonstrated with a high sodium diffusion coefficient, pseudocapacitive effect, and excellent reversibility. Such a unique composite structure is designed and synthesized via a facile sulfidation of the CoZn‐MOFs followed by calcination and is highly dependant on the reaction time and temperature. The optimized Co1Zn1‐S(600) electrode exhibits excellent sodium storage performance, including a high capacity of 542 mA h g−1 at 0.1 A g−1, good rate capability at 10 A g−1, and excellent cyclic stability up to 500 cycles for half‐cell. It also shows potential in full‐cell configuration. Such capabilities will accelerate the adoption of sodium‐ion batteries for electrical energy applications.

Encapsulation of CoSx Nanocrystals into N/S Co‐Doped Honeycomb‐Like 3D Porous Carbon for High‐Performance Lithium Storage

“…As shown in Figure 7b, contrary to the EIS pattern, the PC and CS samples have the maximum and minimum slope values, respectively, so the composite of pure cobalt sulfide and porous carbon has a moderate slope, which means a lager lithium ions diffusion coefficient. This outcome is consistent with the GITT test, which was performed to elucidate the effect of multi‐step lithiation/delithiation on ion diffusion and conductivity properties 61. The corresponding diffusion coefficients at different discharge/charge voltages were calculated according to Equation (S2) (see details in the Supporting Information), and the results of the first two laps are shown in Figure 7c.…”

“…The value of b varies from 0.5 (diffusion‐controlled process) to 1.0 (capacitive‐controlled process) and is calculated by the slope of log ( I ) versus log ( v ) plot (Figure 6b) 59. And the b values for peaks 1 and 2 are 0.72 and 0.74, respectively, indicating surface capacitive‐controlled process kinetically favored the CS@PC electrode 60, 61. According to Equation (3), by plotting I ( V )/ v 1/2 versus v 1/2 at different potentials, one can calculate the values of k 1 (slope) and k 2 (intercept) from the straight lines.…”

In Situ Fabrication of Branched TiO2/C Nanofibers as Binder‐Free and Free‐Standing Anodes for High‐Performance Sodium‐Ion Batteries

“…The difference was more obvious in the higher voltage range than in the lower range, which implied the better kinetic property of BT/C NFs . The calculated Na + diffusion kinetics ( D Na + ) during the discharge process were clearly presented in Figure S11c (Supporting information), and the calculation could be found in Figure S11b (Supporting information) . Both electrodes showed a progressively decreasing D Na + with the sodiation proceeding, which was associated with the sloping characteristics of the discharge profiles.…”

Highly Reversible Phase Transition Endows V6O13 with Enhanced Performance as Aqueous Zinc‐Ion Battery Cathode

“…In addition, the biphasic material may contribute to high electronic conductivity and pseudocapacitive effect, leading to the fast ion diffusion kinetics. Moreover, the biphasic material with stepwise redox reactions can effectively reduce the solid‐state diffusion and thus relieve the stress during the insertion of ions . Remarkably, many zinc vanadates were demonstrated to exhibit superior electrochemical behavior as aqueous ZIB cathodes, especially the Zn 0.25 V 2 O 5 · n H 2 O material reported by Nazar and co‐workers, whose study revealed that Zn 0.25 V 2 O 5 · n H 2 O can perform at a high capacity and demonstrate excellent long‐term cyclic stability in virtue of its favorable structure.…”