Nature of FeSe₂/N‐C Anode for High Performance Potassium Ion Hybrid Capacitor

Abstract

In addition, in-depth understanding of the nature of electrode material is an essential step in the development of electrode materials. [21][22][23][24] The electrode materials play a vital role in the battery. [25,26] During the deintercalation and conversion reactions, the electrode material is subjected to various physical and chemical changes, such as phase transitions and electrochemical reorganization. [27] These series of physical and chemical changes will affect the electrochemical performance. [28] Therefore, it is necessary to optimize and improve the electrochemical performance of the battery by studying the reaction mechanism. [29][30][31][32] Transition metal dichalcogenides (TMDs) have gained comprehensive attention in the field of energy storage due to their unique electrochemical properties, high electrical conductivity, and high capacity. [33][34][35][36][37][38][39][40] The inadequacies are also obvious, including volume expansion, agglomeration, low ion-diffusion coefficient, and side reaction during discharge/charge, resulting in the rapid decay of capacity. [41] To achieve high performance rechargeable batteries, it is important to understand the physical and chemical changes in electrode materials during the charge/discharge process. Researchers have made remarkable progress. [42] Usually TMDs involve a multi-step reaction mechanism as anode material for lithium ion batteries and sodium ion batteries (intercalation and conversion). [43][44][45] However, the physical and chemical changes in these TMDs in the potassium ion batteries are still not clear, which hinders the design and development of electrode materials. Therefore, exploring the reaction mechanism of metal selenide not only allows us to understand the relationship between TMDs and K + , but also achieve a long life cycle that would be a breakthrough for large-scale energy storage equipment.Herein, we successfully synthesized carbon-coated FeSe 2 clusters via a solvothermal method. The FeSe 2 clusters are well wrapped by the carbon layer, which improves electron conductivity and alleviates volume expansion. Benefiting from the unique structure, FeSe 2 /N-C exhibit ultra-stable cycle performance with a reversible capacity of up to 170 mAh g −1 at a high current of 2000 mA g −1 , which remains ≈158 mAh g −1 after 2000 cycles. The capacity retention is close to 100%. The electrodes also show remarkable rate performance. Furthermore, first-principles calculations, in situ X-ray diffraction, and ex situ transmission electron microscopy (in situ XRD and ex-TEM) Potassium ion hybrid capacitors have great potential for large-scale energy devices, because of the high power density and low cost. However, their practical applications are hindered by their low energy density, as well as electrolyte decomposition and collector corrosion at high potential in potassium bis(fluoro-sulfonyl)imide-based electrolyte. Therefore, anode materials with high capacity, a suitable voltage platform, and stability become a key factor. Here, N-doping carbon-co...

Pitch‐Derived Soft Carbon as Stable Anode Material for Potassium Ion Batteries

“…[ 18 ] Besides, the construction of 3D structure with heteroatoms could also achieve high capacity and stabilize the structure. [ 19 ] The electrochemical profile of hard carbon usually showed a sloping curve with capacity contribution largely from the high voltage region (>1 V), [ 9,20,21 ] while the capacity from high voltage region (>1 V) will unfortunately diminish its potential as a possible high‐energy anode material. It is therefore in urgent need that materials innovation on KIB anodes be enforced to not only ensure structural integrity, but also guarantee a well‐tamed electrochemical behavior for high energy density.…”

Cucurbit[6]uril‐Derived Nitrogen‐Doped Hierarchical Porous Carbon Confined in Graphene Network for Potassium‐Ion Hybrid Capacitors

“…[5][6][7] Among them, potassium-ion hybrid capacitors (PIHCs) exhibit broader economic prospects due to the profuse natural abundance of potassium and the similar reduction potential and physical properties of potassium and lithium. [8][9][10][11][12][13][14][15] However, PIHCs suffer from severe kinetics failures and cyclability dilemmas since the large ionic size of K + (1.38 Å). [10,[13][14][15] In the view of PIHCs system, the anode side based on sluggish battery-type reactions is the short-board to achieve high-performance PIHCs.…”

Heterostructures of 2D Molybdenum Dichalcogenide on 2D Nitrogen‐Doped Carbon: Superior Potassium‐Ion Storage and Insight into Potassium Storage Mechanism

“…[ 1–5 ] Among various alkali metals ion batteries, potassium‐ion batteries (KIBs) exhibit many advantages for large‐scale energy storage system applications including: [ 6,7 ] 1) the low manufacturing costs because of the natural abundance of their raw materials; 2) much lower redox potential of K/K + (−2.93 V vs standard hydrogen electrode) leading to higher open‐circuit voltage and higher energy density compared with sodium‐ion batteries (SIBs). [ 8–10 ] According to the advantages and properties of low production costs and high energy density, the KIB is considered as a promising energy storage system for large‐scale energy storage application. However, KIBs suffer from inferior cyclic stability and insufficient power density resulting from the structure collapse of electrode materials due to the bigger K + insertion/extraction in/from the electrode.…”