FeSb2 Nanoparticles Embedded in 3D Porous Carbon Framework: An Robust Anode Material for Potassium Storage with Long Activation Process.

Due to their characteristics of high capacity and appropriate potassiation/depotassiation potential, Sb-based materials have become a class of promising anode materials for potassium ion batteries (PIBs). However, the huge strain induced by potassiation/depotassiation limits their ability to periodically accept/release K+ . Herein, a composite with FeSb2 nanoparticles embedded in a 3D porous carbon framework (FeSb2 @3DPC) is successfully constructed as an extremely stable anode material for PIBs. Benefiting from the synergistic effect of the design of nano and porous structures, the introduction of the inactive metal Fe, the firm anchoring of the FeSb2 nanoparticles by the carbon material, and the incomplete reaction of the FeSb2 , the FeSb2 @3DPC can achieve an ultra-long cycle life of over 4000 cycles at a current density of 500 mA g-1 . Furthermore, ex situ X-ray diffraction and transmission electron microscopy reveal a gradual activation process of FeSb2 for potassium storage. Fortunately, after activation, the electrochemical polarization of the FeSb2 @3DPC anode gradually alleviates and the capacitance-controlled charge storage mode further dominates compared with the diffusion-controlled mode, all of which promote the FeSb2 @3DPC to maintain the stable potassium storage capability.

Nitrogen-coordinated antimony atom anchored on carbon matrix as efficient active sites to enhance sodium/potassium ion storage.

Carbon-based anode materials have become a research hotspot for alkali metal ion batteries. Crucially, the electrochemical performance of carbon materials must be improved by appropriate means such as micro-nano structure design and atomic doping. Herein, antimony doped hard carbon materials are prepared by anchoring Sb atoms on nitrogen-doped carbon (SbNC). The coordination of non-metal atoms can better disperse Sb atoms on the carbon matrix, and the synergistic effect between Sb atoms, coordinated non-metal atoms, and hard carbon matrix endows SbNC anode with good electrochemical performance. When used in sodium-ion half-cells, the SbNC anode showed high rate capacity of 109 mAh g-1 at 20 A g-1 and good cycling performance (254 mAh g-1 at 1 A g-1 after 2000 cycles). In addition, when used in potassium-ion half-cells, the SbNC anode exhibited initial charge capacity of 382 mAh g-1 at 0.1 A g-1 and rate capacity of 152 mAh g-1 at 5 A g-1. This research shows that compared with ordinary nitrogen doping, Sb-N coordination active sites on carbon matrix can provide much more adsorption capacity, improve ion filling and diffusion properties as well as enhance the kinetics of electrochemical reaction for the sodium/potassium storage.

Dual-Carbon confinement strategy of antimony anode material enabling advanced potassium ion storage.

Antimony (Sb) has attracted considerable attention as an anode material for potassium ion batteries (PIBs) because of its high theoretical capacity. Nevertheless, owing to the large radius of K+, apparent volume expansion occurs during the reaction between Sb and K+, which will undermine the stability of the electrode. Accordingly, a dual-carbon confinement strategy is regarded as an effective method for handling this issue. Herein, Sb is firstly captured by mesoporous carbon sphere (MCS) to form a composite of Sb/MCS, and then reduced graphene oxide (rGO) is adopted as an outer layer to wrap the Sb/MCS to obtain the dual-carbon confinement material (Sb/MCS@rGO). Given the synergistic confinement effects of the MCS and rGO, the Sb/MCS@rGO electrode realizes an excellent rate capacity of 341.9 mAh g-1 at 1000 mA g-1 and prominent cycling stability with around 100% retention at 50 mA g-1 after 100 cycles. Besides, the discussion on galvanostatic charge-discharge test, cyclic voltammetry and ex-situ XRD illustrates the stepwise potassium storage mechanism of Sb. Benefiting from the dual-carbon confinement effects, the Sb/MCS@rGO electrode processes promising electrochemical reaction kinetics. Furthermore, the application of the Sb/MCS@rGO in full cells also demonstrates its superior rate capacity (212.3 mAh g-1 at 1000 mA g-1).

Construction of three-dimensional nitrogen doped porous carbon flake electrodes for advanced potassium-ion hybrid capacitors.

It is of great significance to develop a new kind of green and environmentally friendly potassium ion energy storage device, with stable structures and large specific capacity. In this manuscript, a facile and robust way is reported to construct nitrogen doped porous carbon flake (NPCF) through NaCl template and pyrolysis method. 3D porous structures can be formed and interconnected NPCF are used as potassium ion batteries (PIBs) anode. High content of pyridinic N/pyrrolic N and enlarged interlayer distance of NPCF are obtained. Specifically, the anode delivers a high reversible capacity of 326.3 mAh g-1 at the current density of 50 mA g-1, and shows up outstanding cycle stability and represents long cycle life of 10,000 cycles at a current density of 5000 mA g-1. Moreover, the cyclic voltammetry kinetic analysis shows that the main capacitive process plays a leading role in the potassium storage mechanism. Consequently, equipped with activate carbon (AC) as cathode and NPCF as anode, the assembled potassium ion hybrid capacitors (PIHCs) achieve an energy density of 65.8 Wh kg-1 at 100 mA g-1, and maintains 30 Wh kg-1 even at a high current density of 5000 mA g-1.

High Capacity and Fast Kinetics of Potassium-Ion Batteries Boosted by Nitrogen-Doped Mesoporous Carbon Spheres.

In view of rich potassium resources and their working potential, potassium-ion batteries (PIBs) are deemed as next generation rechargeable batteries. Owing to carbon materials with the preponderance of durability and economic price, they are widely employed in PIBs anode materials. Currently, porosity design and heteroatom doping as efficacious improvement strategies have been applied to the structural design of carbon materials to improve their electrochemical performances. Herein, nitrogen-doped mesoporous carbon spheres (MCS) are synthesized by a facile hard template method. The MCS demonstrate larger interlayer spacing in a short range, high specific surface area, abundant mesoporous structures and active sites, enhancing K-ion migration and diffusion. Furthermore, we screen out the pyrolysis temperature of 900 °C and the pore diameter of 7 nm as optimized conditions for MCS to improve performances. In detail, the optimized MCS-7-900 electrode achieves high rate capacity (107.9 mAh g-1 at 5000 mA g-1) and stably brings about 3600 cycles at 1000 mA g-1. According to electrochemical kinetic analysis, the capacitive-controlled effects play dominant roles in total storage mechanism. Additionally, the full-cell equipped MCS-7-900 as anode is successfully constructed to evaluate the practicality of MCS.

Carbon Hollow Tube-Confined Sb/Sb2S3 Nanorod Fragments as Highly Stable Anodes for Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) have attracted widespread attention in recent years due to their potential advantages such as low cost and high energy density. However, the large radius of K+ and the low potassium storage capacity of some electrode materials limit their development. Antimony (Sb)-based materials are considered to be promising anode materials for PIBs in view of their high K storage capacity and low potassiation potential. Nonetheless, the huge volume variation caused by potassiation/depotassiation often leads to their failure. Previous works have proved that carbon coating and nanostructure design are important means to alleviate the volume effect. Herein, the carbon-coating technology and nanostructure design were combined to prepare a Sb-based nanomaterial with Sb/Sb2S3 hybrid nanorod fragments confined in a carbon hollow tube (Sb/Sb2S3@CHT). Such a nanostructure is beneficial to alleviate the volume change of the Sb/Sb2S3 hybrids while facilitating the kinetics of the electrochemical reaction. As a consequence, the Sb/Sb2S3@CHT anode electrode exhibits high rate performance and outstanding cycle stability characterized by retaining a high specific capacity of 400.9 mA h g-1 after cycling for 200 cycles at 200 mA g-1.

In-Depth Mechanism Understanding for Potassium-Ion Batteries by Electroanalytical Methods and Advanced In Situ Characterization Techniques.

The advancement of potassium ion batteries (PIBs) stimulated by the dearth of lithium resources is accelerating. Major progresses on the electrochemical properties are based on the optimization of electrode materials, electrolytes, and other components. More significantly, the prerequisites for optimizing these key compositions are in-depth and comprehensive exploration of electrochemical reaction processes, including the evolution of morphology and structure, phase transition, interface behaviors, and K+ movement, etc. As a result, the obtained K+ storage mechanism via analyzing aforementioned reaction processes sheds light on furthering practical application of PIBs. Typical electrochemical analysis methods are capable of obtaining physical and chemical characteristics. The advent of in situ electrochemical measurements enables dynamic observation and monitoring, thereby gaining extensive insights into the intricate mechanism of capacity degradation and interface kinetics. By coupling with these powerful electrochemical characterization techniques, inspiring works in PIBs will burgeon into wide realms of energy storage fields. In this review, some typical electroanalytical tests and in situ hyphenated measurements are described with the main concentration on how these techniques play a role in investigating the potassium storage mechanism for PIBs and achieving encouraging results.

Advanced Anode Materials of Potassium Ion Batteries: from Zero Dimension to Three Dimensions.

Potassium ion batteries (PIBs) with the prominent advantages of sufficient reserves and economical cost are attractive candidates of new rechargeable batteries for large-grid electrochemical energy storage systems (EESs). However, there are still some obstacles like large size of K+ to commercial PIBs applications. Therefore, rational structural design based on appropriate materials is essential to obtain practical PIBs anode with K+ accommodated and fast diffused. Nanostructural design has been considered as one of the effective strategies to solve these issues owing to unique physicochemical properties. Accordingly, quite a few recent anode materials with different dimensions in PIBs have been reported, mainly involving in carbon materials, metal-based chalcogenides (MCs), metal-based oxides (MOs), and alloying materials. Among these anodes, nanostructural carbon materials with shorter ionic transfer path are beneficial for decreasing the resistances of transportation. Besides, MCs, MOs, and alloying materials with nanostructures can effectively alleviate their stress changes. Herein, these materials are classified into 0D, 1D, 2D, and 3D. Particularly, the relationship between different dimensional structures and the corresponding electrochemical performances has been outlined. Meanwhile, some strategies are proposed to deal with the current disadvantages. Hope that the readers are enlightened from this review to carry out further experiments better.