Hierarchical Triple‐Shelled MnCo₂O₄ Hollow Microspheres as High‐Performance Anode Materials for Potassium‐Ion Batteries

Abstract

Metal oxide anode materials generally possess high theoretical capacities. However, their further development in potassium‐ion batteries (KIBs) is limited by self‐aggregation and large volume fluctuations during charge/discharge processes. Herein, hierarchical MnCo2O4 hollow microspheres (ts‐MCO HSs) with three porous shells that consist of aggregated primary nanoparticles are fabricated as anode materials of KIBs. The porous shells are in favor of reducing the diffusion path of K‐ions and electrons, and thus the rate performance can be enhanced. The unique triple‐shelled hollow structure is believed to provide sufficient contact between electrolyte and metal oxides, possess additional active storage sites for K‐ions, and buffer the volume change during K‐ions insertion/extraction. A high specific capacity of 243 mA h g−1 at 100 mA g−1 in the 2nd cycle and a highly improved rate performance of 153 mA h g−1 at 1 A g−1 are delivered when cycled between 0.01 and 3.0 V. In addition, the transformation of substances during charging/discharging processes are intuitively demonstrated by the in situ X‐ray diffraction strategy for the first time, which further proves that the unique structure of ts‐MCO HSs with three porous shells can significantly enhance the potassium ions storage performance.

Water‐Soluble Salt Template‐Assisted Anchor of Hollow FeS2 Nanoparticle Inside 3D Carbon Skeleton to Achieve Fast Potassium‐Ion Storage

“…[ 16,18,29 ] Particularly for electrode materials, the 3D hollow configuration including yolk‐shell structure, capsule‐like architecture, hollow tubular skeleton, and hierarchical hollow structure have been extensively studied to boost K‐ions storage properties. [ 10,29–34 ] The nanoscale hollow configuration can not only shorten the K‐ions and electrons diffusion path, but also provide enough space to accommodate volume expansion and avoid exfoliation of active materials from the electrodes. [ 16,35 ] Based on the aforementioned considerations, it would be of great interests by integrating these advantages into one alliance to optimize their potential for high‐performance K‐ions storage.…”

Crystal Facet and Architecture Engineering of Metal Oxide Nanonetwork Anodes for High-Performance Potassium Ion Batteries and Hybrid Capacitors

“…The interconnected structure can provide a continuous transition path for electrons and ion diffusion, enabling efficient charge carriers in electrochemical reactions and being beneficial toward reducing the polarization caused by current changes. In the radar chart of Figure g, the comparison of various metal oxide anodes without assistance of carbonaceous materials in five aspects, including initial Coulombic efficiency (ICE), low rate specific capacity at 50 mA g –1 (SCL), high rate specific capacity at 500 mA g –1 (SCH), and cyclability such as cycle number and capacity retention rate (CR), are shown. − Owing to the inevitable capacity loss inherent from the conversion mechanism, the irreversible reaction involved in the first cycle requires that the ICE of all metal oxides is less than 60%. The BiSbO 4 networks not only deliver high gravimetric capacity at both low and high current densities but also accomplish a cycle stability of up to 1000 cycles due to intercommunicated diffusion tunnels and the robust framework of oxygen layer in BiSbO 4 nanonetwork.…”

Defects and sulfur-doping design of porous carbon spheres for high-capacity potassium-ion storage

“…All samples show a typical type I isotherm, conrming a porous structure dominated by micropores (<2 nm) with a small number of mesopores (2-3 nm) coexisting. 11 The presence of micropores can provide active sites and facilitate the rapid transmission of ions, while mesopores can accommodate the volume expansion during the electrochemical cycle and promote the rapid diffusion of the electrolyte. As shown in Fig.…”

“…Numerous efforts have been devoted to exploring anode materials for KIBs, including carbonaceous materials, 7,8 metal alloys, 9,10 transition-metal oxides/suldes 11,12 and MXene-based materials. 13,14 Carbonaceous materials are considered as the most promising anode candidate because of their high capacity, superior electrical conductivity, and stable physical/chemical properties.…”