Robust Pseudocapacitive Sodium Cation Intercalation Induced by Cobalt Vacancies at Atomically Thin Co_1−xSe₂/Graphene Heterostructure for Sodium‐Ion Batteries

Abstract

Electronic structure engineering on electrode materials could bring in a new mechanism to achieve high energy and high power densities in sodium ion batteries. Herein, we design and create Co vacancies at the interface of atomically thin CoSe2/graphene heterostructure and obtain Co1−xSe2/graphene heterostructure electrode materials that facilitate significant Na+ intercalation pseudocapacitance. Density functional theory (DFT) calculation suggests that the Na+ adsorption energy is dramatically increased, and the Na+ diffusion barrier is remarkably reduced due to the introduction of Co vacancy. The optimized electrode delivers a superior capacity of 673.6 mAh g−1 at 0.1 C, excellent rate capability of 576.5 mAh g−1 at 2.0 C and ultra‐long life up to 2000 cycles. Kinetics analysis indicates that the enhanced Na+ storage is mainly attributed to the intercalation pseudocapacitance induced by Co vacancies. This work suggests that the creation of cation vacancy could bestow heterostructured electrode materials with pseudocapacitive Na+ intercalation for high‐capacity and high‐rate energy storage.

Synergistic Engineering of Se Vacancies and Heterointerfaces in Zinc‐Cobalt Selenide Anode for Highly Efficient Na‐Ion Batteries

“…Generally, the charge storage is comprised of ion diffusion-controlled contribution and pseudocapacitive-controlled charge. [6,57] According to the power-law formula between peak current (i) and scan rate (v) as below, the capacity contribution can be determined:…”

“…The high pseudo-capacitive contribution to the overall capacity could be mainly associated with the effective exposure of active sites, excellent interfacial properties, enhanced electronic conductivity, and accelerated ion diffusion rate endowed by the high-quality heterostructure and Se vacancies introduced in situ within the typical sample, which provides additional shuttle paths for sodium ions and promotes the kinetics of the electrochemical reaction. [57] Ex situ XRD measurement and SEM images at different stages of the electrochemical reaction were conducted to further reveal the possible superior Na + -storage mechanism of ZnSe/CoSe 2 -CN. Figure S18a, Supporting Information shows the initial discharge and charge states at potentials between 0.4 and 3.0 V at 0.1 A g -1 .…”

Manipulating Spin Polarization of Defected Co3O4 for Highly Efficient Electrocatalysis

“…As shown in Fig. 3a, the intensity distribution of the spherical aberration-corrected STEM image along the selected area suggests the existence of vacancies in the surface lattice, which should be the cobalt defect [40,41].…”

Topological transformation construction of a CoSe2/N-doped carbon heterojunction with a three-dimensional porous structure for high-performance sodium-ion half/full batteries

“…In addition, with increasing scanning rates, the slight shift of the redox peaks is due to the existence of polarization. To qualitatively analyze the electrochemical reaction process, the connection between peak current i and scanning rate v is described by the following formula: 48…”