Respective Roles of Inner and Outer Carbon in Boosting the K⁺ Storage Performance of Dual‐Carbon‐Confined ZnSe

Abstract

Potassium-ion batteries (PIBs) have been considered as potential alternatives for lithium-ion batteries since there is a demand for better anode with superior energy, excellent rate capability, and long cyclability. The high-capacity zinc selenide (ZnSe) anode, which combines the merits of conversion and alloying reactions, is promising for PIBs but suffers from poor cyclability and low electronic conductivity. To effectively boost electrochemical performance of ZnSe, a "dual-carbon-confined" structure is constructed, in which an inner N-doped microporous carbon (NMC)-coated ZnSe wrapped by outer-rGO (ZnSe@i-NMC@o-rGO) is synthesized. Combining finite element simulation, dynamic analysis, and density functional theory calculations, the respective roles of inner-and outer-carbon in boosting performance are revealed. The inner-NMC increased the reactivity of ZnSe with K + and alleviated the volume expansion of ZnSe, while outer-rGO further stabilized the structure and promoted the reaction kinetics. Benefiting from the synergistic effect of dual-carbon, ZnSe@i-NMC@o-rGO exhibited a high specific capacity 233.4 mAh g −1 after 1500 cycles at 2.0 A g −1 . Coupled with activated carbon, a potassium-ion hybrid capacitor displayed a high energy density of 176.6 Wh kg −1 at 1800 W kg −1 and a superior capacity retention of 82.51% at 2.0 A g −1 after 11000 cycles.

Research progress on ZnSe and ZnTe anodes for rechargeable batteries

“…73 Worth noting is that these conductive materials not only reduce resistance but also serve as buffers to alleviate volumetric changes during repeated charging/discharging. 46,74 Furthermore, the strategies of structural control and hybridization with conductive materials are usually integrated (e.g., ZnSe/C hollow polyhedra, 46,47 ZnSe/MWCNTs, 75,76 ZnSe embedded in N-doped carbon nanofibers, 77,78 willow-leaf-like ZnSe@NC, 33 ZnSe nanoparticles embedded in N-doped porous carbon nanosheets, 79 3D ordered porous ZnSe/N-doped carbon hybrid, 54 "dual-carbon-confined" ZnSe@i-NMC@o-rGO 80 ), thus for synergistic effects to boost the overall electrochemical performance.…”

“…Potassium-ion batteries (PIBs) are considered as another candidate to replace LIBs, owing to the low redox potential and high abundance of K in the Earth's crust (similar abundance but lower redox potential compared with Na). 35,50,56,80,88 However, the relatively large K + ions require specific active materials to avoid or alleviate the sluggish reaction kinetics and undesirable structural collapse; thus, considerable effort has been made in material design and electrode engineering, including typical transition-metal chalcogenides (TMCs) such as ZnSe-and ZnTe-based anode materials (see Table 3), owing to their appropriate potential plateau, high theoretical capacity, high electrical conductivity and low cost.…”

“…However, the electronic conductivity and structural stability need to be further improved for an enhanced electrochemical performance. 80 Incorporation with carbon is a facile but most effective way to boost the performance of ZnSe-based PIBs, and most studies are now focused on ZIF-8-derived ZnSe hybrids. 50,132 Besides the nanoparticles, some other low-dimensional nanostructures have also been designed to address these problems, e.g., 1D ZnSe@C porous nanorods and nanofibers.…”

“…The enhanced performance may be attributed to the increased K + reactivity and alleviated volume expansion with/of ZnSe via the introduction of an inner carbon layer along with the stabilized structure and promoted reaction kinetics caused by the outer rGO matrix, i.e., the so-called synergistic effect of the dual-carbon. 80 Some similarly constructed mixed-metal selenide hybrid structures also exhibited Fig. 18 (a) Schematic illustration of the synthesis of ZnSe@i-NMC@o-rGO.…”

“…FFT: fast Fourier transform. Reprinted from ref 80. under the terms of the Creative Commons CC BY 4.0 license, Copyright 2021, Published by Wiley-VCH GmbH.…”