Layered transition-metal (TM) oxides have drawn ever-growing interest as positive electrode materials in potassium-ion batteries (PIBs). Nevertheless, the practical implementation of these positive electrode materials is seriously hampered by their inferior cyclic property and rate performance. Reported here is a self-templating strategy to prepare homogeneous P2-K0.6CoO2 (KCO) microcubes. Benefiting from the unusual microcube architecture, the interface between the electrolyte and the active material is considerably diminished. As a result, the KCO microcubes manifest boosted electrochemical properties for potassium storage including large reversible capacity (87.2 mAh g–1 under 20 mA g–1), superior rate performance, and ultralong cyclic steady (an improved capacity retention of 86.9% under 40 mA g–1 after 1000 cycles). More importantly, the fabrication approach can be effectively extended to prepare other layered TM oxide (P3-K0.5MnO2, P3-K0.5Mn0.8Fe0.2O2, P2-K0.6Co0.67Mn0.33O2, and P2-K0.6Co0.66Mn0.17Ni0.17O2) microcubes and nonlayered TM oxide (KFeO2) microcubes.

No abstract

No abstract

Covalent organic frameworks (COFs) are attractive candidates for low-cost potassium-ion battery (PIB) electrode materials due to their inherent porosity, well-organized channel structure, and excellent thermochemical stability. Herein, a Schiff-base COF/carbon nanotubes (TP-COF/CNTs) composite is synthesized by a condensation reaction between 1,3,5-triformylbenzene (TFB) and pphenylenediamine (PPD) on the surface of CNTs as an anode for PIBs. The introduction of CNTs not only assumes the role of a conductive network in improving the kinetics of potassium ions (K + ) but also induces the growth of COFs through π−π interactions, leading to more exposure of more active sites. In consequence, the core−shell-structured TP-COF/CNTs exhibit advanced K storage performance (290 mA h g −1 after 200 cycles at 0.1 A g −1 ) and fine rate capability (169 mA h g −1 at 1 A g −1 ), outperforming most COF materials. Furthermore, X-ray photoelectron spectroscopy, ex situ infrared analysis, and density functional theory calculations indicate that the storage of K + depends on electroactive C�N groups and the π−K + effect. This work supplies PIBs with a promising high-performance anode material and may benefit the development of COFs for PIBs.

No abstract