High Potassium Storage Capability of H₂V₃O₈ in a Non‐Aqueous Electrolyte

Abstract

Potassium‐ion batteries (KIBs) are one of the potential candidates for large‐scale energy storage devices with low cost due to the abundance of potassium resources. However, the development of cathode materials with high capacity and structural stability has been a challenge due to the difficulties of intercalation of the large size of K‐ions into host materials. In this work, H2V3O8 (or V3O7⋅H2O) is reported as a new cathode material for KIBs. It shows reversible potassium‐intercalation behavior with the first discharge capacity of 168 mAh g−1 at 5 mA g−1 and an average discharge voltage of ∼2.5 V (vs. K/K+) in 0.5 M KPF6 in EC/DEC (1:1 v/v). The specific capacity increases up to 181 mAh g−1 for the third cycle and gradually decreases with 75% of the capacity retention after 100 cycles. The chemical formula of the potassiated phase is K1.77H2V3O8. However, scan‐rate dependent cyclic voltammetry and elemental analyses suggest that ∼28% of the capacity comes from the surface K ions on the H2V3O8 particles; thus, the bulk‐intercalated phase can be formulated as K1.27H2V3O8. The crystal structure is stable during the electrochemical cycling, keeping the structural water, confirming that H2V3O8 can be considered as one of the high‐capacity cathode materials for KIBs.

Modified H2V3O8 to Enhance the Electrochemical Performance for Li‐ion Insertion: The Influence of Prelithiation and Mo‐Substitution

“…62–6) [22] . It consists of V 3 O 8 layers, where each layer consists of edge‐ and corner‐shared VO 6 octahedra and VO 5 square pyramids (see Figure 1a) [23–25] . Table S1 gives a general overview over previous syntheses and studies of HVO for different insertion ions, since the open framework of HVO offers not only insertion possibilities for Li + , but also for Na + , Mg 2+ , or Zn 2+ [21,23,26–28] .…”

Recent Progress and Prospects of Layered Cathode Materials for Potassium‐ion Batteries

“…With the various modifications achieved by researchers, such as element doping, surface coating, and ion exchange, layered transition metal oxides show improved cycling stability. [137][138][139][140][141] However, most of layered materials still face the challenges of low capacity, low working voltage (< 3.0 V), and K deficiency (K/M < 1) in PIBs. The key issue is the strong K + ÀK + repulsion caused by large ion size of K + .…”

Recent Developments and Challenges of Vanadium Oxides (VxOy) Cathodes for Aqueous Zinc‐Ion Batteries

“…The adjacent V 3 O 8 layers are connected mainly by hydrogen bonds, which contribute significantly to the formation of an elastic space with buffering capacity. In addition, the mixed‐valence of V and the weak hydrogen bonding between the layers facilitate the generation of high electrical conductivity while it confers the ability to store Zn 2+ in H 2 V 3 O 8 [80] …”

“…In addition, the mixed-valence of V and the weak hydrogen bonding between the layers facilitate the generation of high electrical conductivity while it confers the ability to store Zn 2 + in H 2 V 3 O 8 . [80] Reproduced with permission. [78] Copyright 2021, Elsevier.…”