Prepotassiated V₂O₅ as the Cathode Material for High‐Voltage Potassium‐Ion Batteries

Abstract

The voltage and capacity of cathodes are critical factors for energy density of batteries. However, the cutoff voltage of cathode materials in potassium‐ion batteries (PIBs) is usually 4.0 V, causing structural transformations in the electrode materials in the course of repeated insertion/extraction of K+ ions with a large radius (1.38 Å). Materials with large interlayer spacing and short ion diffusion paths show promise to overcome this issue. K0.486V2O5 nanobelts, prepared by preinserting K+ ions into V2O5, are used as cathode materials in high‐voltage PIBs. Various analysis methods are used to understand the insertion/extraction behavior of K+ ions in K0.486V2O5 cathodes cycled between 1.5 and 4.2 V. The analyses reveal the highly reversible structural evolution of K0.486V2O5, in which the chemically inserted K+ ions partially remain between VO layers charged at high voltage serving as stabilizing species to prevent phase transformations. K0.486V2O5 cathodes exhibit a high specific capacity of 159 mAh g−1 at 20 mA g−1 with good cycling stability of 67.4% after 100 cycles at 100 mAh g−1 in the half K‐ion cell. The results provide guidelines for designing layered transition metal oxides to be used as cathode materials for high‐voltage PIBs with high energy density.

Challenges and Strategies toward Cathode Materials for Rechargeable Potassium‐Ion Batteries

“…This cathode delivered a capacity of 90 mAh g −1 at 10 mA g −1 in the voltage range of 1.5-3.8 V versus K/K + , good rate capability with a capacity of 60 mAh g −1 at 200 mA g −1 , and good cycling stability with 81% capacity retention after 250 cycles at 100 mA g −1 . [56] It is worth noting that the cutoff voltage of most K x MO 2 rarely exceeds 4 V. [43,46] Recently, Yuan et al [57] reported that the pre-inserted K + ions that partially remained between the V and O layers of V 2 O 5 at a high voltage served as stabilizing species to prevent phase [58] Copyright 2018, Elsevier. b) Typical charge/discharge profile and c) enlarged parts of the ex situ XRD pattern of the K 0.83 V 2 O 5 electrode during the first two cycles at 10 mA g −1 .…”

Organic Electrode Materials for Non-aqueous K-Ion Batteries

“…This review also provides the half-cell/full battery performances of all the organic materials we mentioned. restricts the energy density of K-ion full batteries [51][52][53]. In this case, organic cathode materials with high capacity and potential are essential for KIBs and have become an important topic in the current research.…”

Potassium-ion batteries: outlook on present and future technologies

“…For example, Hironaka et al 73 confirmed that the P2-type KxCoO2 could deliver a high reversible capacity of 60 mAh g -1 between 2.0-3.9 V. Masese et al reported a high voltage (4.3 V vs. K + /K) honeycomb layered cathodes P2-type K2NiCoTeO6 for rechargeable PIBs due to the virtue of its moderately inductive TeO6 6framework 74 , and also attributed to a honeycomb-layered K2Ni2TeO6 cathode with a high average discharge voltage of 3.6 V versus K + /K; and a reversible capacity of about 70 mAh g -1 . Various potassium vanadate compounds, including K2V3O8 and K0.486V2O5, were also reported as novel active materials for K storage with suitable reversible capacity 75,76 . The development of novel layered transition metal oxides cathode materials is still imperative and important for the improvement of PIBs.…”