Anti‐Aggregation of Nanosized CoS₂ for Stable K‐Ion Storage: Insights into Aggregation‐Induced Electrode Failures

Abstract

As promising conversion‐type anode materials for potassium‐ion storage, transition metal chalcogenides (TMCs) exhibit high energy density but suffer severe capacity fading, which is generally ascribed to their large volume expansion and the associated structural degradation. Instead, this study emphasizes that the aggregation of nanosized TMCs during conversion reaction is a more crucial reason for the following serious electrode failures. This issue has not received enough attention, and especially the detailed aggregation mechanism and its relationship to electrode failures remains unclear. Thus, by combining in situ and ex‐situ electron microscopies, the aggregation evolution of nanosized CoS2 is systematically investigated from micro to macro scale. The aggregation originates from the coalescence of the K2S matrix during potassiation, which constantly develops into larger‐scale agglomerates as the cycling continues, eventually leading to electrode fragmentation, etc. To address this issue, an anti‐aggregation strategy is proposed through isolating CoS2 nanoparticles inside individual carbon nanoshells. Impressively, the CoS2 aggregation is strictly confined within each nanoshell, which prevents their extensive aggregation across the electrode, resulting in the superior structural and electrochemical stability. This work reveals the mechanism of aggregation‐induced electrode failures and proposes the necessity of anti‐aggregation of nanosized active materials for the design of high‐capacity electrodes.

Accelerated Diffusion Kinetics in ZnTe/CoTe2 Heterojunctions for High Rate Potassium Storage

“…Amongst these, transition metal tellurides (TMTs) are of particular research interest because of distinctive ionic transfer kinetics, safe potential plateau, and multiple electrochemical reactions, i.e., conversion and alloying. [12,13] TMTs present greater lattice parameters and have better electrical conductivity than sulfides, and selenides because of the larger atomic number and lower electronegativity of Te, with the expectation of boosted kinetics. [14] Additionally, TMTs have a higher density than corresponding sulfides and selenides, and therefore contribute to a greater volumetric capacity.…”

Insight into Highly Graphitic Hollow Spheres for Superior Potassium Ion Batteries

“…In addition to the structural configuration that can adapt to the drastic volume deformation and shorten K + diffusion paths, HGHS also has sufficient active sites, endowing HGHS anodes with excellent electrochemical performance. [54][55][56] The electrochemical performance of HGHS as PIBs anode was assessed in the CR2032 coin half-cell, with the counter electrode of potassium metal and electrolyte of 3M potassium bis(fluorosulfonyl)imide in dimethyl ether. [57][58][59] Its cyclic voltammetry (CV) revealed the storage behavior of K + in HGHS.…”

Constructing Active BN Sites in Carbon Nanosheets for High‐Capacity and Fast Charging Toward Potassium Ion Storage

“…where k 1 ν and k 2 ν 1/2 represent the surface-driven process and diffusion-controlled behavior, respectively. [56,57] For example, at the scan rate of 0.5 mV s −1 , the calculated capacitance percentage of BNC-2 is about 63.4%, higher than that of NC (55.6%) and BNC-1 (59.6%), but lower than that of BNC-3 (72.2%) (Figure 4c and Figure S11, Supporting Information). This implies that the attendance of B can modulate the storage kinetics via the regulation on storage behavior, which is consistent with Figure 4b.…”