K_0.83V₂O₅: A New Layered Compound as a Stable Cathode Material for Potassium-Ion Batteries

Abstract

Recently, potassium-ion batteries (PIBs) are being actively investigated. The development of PIBs calls for cathode materials with a rigid framework, reversible electrochemical reactivity, and a high amount of extractable K ions, which is extremely challenging due to the large size of potassium. Herein, a new layered compound K0.83V2O5 is reported as a potential cathode material for PIBs. It delivers an initial depotassiation capacity of 86 mAh g–1 and exhibits a reversible capacity of 90 mAh g–1 with a high redox potential of 3.5 V (vs K+/K) and a capacity retention of more than 80% after 200 cycles. Experimental investigations combined with theoretical calculation indicate that depotassiation–potassiation is accommodated by contraction–expansion of the interlayer spacing along with unpuckering–puckering of the layers. Additionally, the calculated electronic structure suggests the (semi)­metallic feature of K x V2O5 (0 < x ≤ 0.875) and K-ion transport in the material is predicted to be one-dimensional with the experimentally estimated chemical diffusion coefficient in the order of 10–15–10–12 cm2 s–1. Finally, a K-ion full cell consisting of the K0.83V2O5 cathode and a graphite anode is demonstrated to deliver an energy density of 136 Wh kg–1. This study will provide insights for further designing novel layered cathodes with high K-ion content for PIBs.

A Low‐Strain Potassium‐Rich Prussian Blue Analogue Cathode for High Power Potassium‐Ion Batteries

“…The time versus voltage curve for a single titration is shown in the Supporting Information, Figure S10. The calculated K + diffusion coefficients of KNiHCF were between 10 −11 and 10 −9 cm 2 s −1 during the charge/discharge processes (Figure 4 a), which are higher than those of most reported cathode materials (Supporting Information, Figure S11), indicating the fast K + diffusion kinetics [17, 40–46] . The high K + diffusion coefficient is responsible for the outstanding rate performance of KNiHCF electrode.…”

“…In the subsequent discharging process,t he peaks shift towards higher angle and return to the original position after fully discharge to 2.0 V, which elucidates the highly reversible phase change.The lattice parameters during charge and discharge are summarized in Figure 3c.K NiHCF achieves ultrasmall lattice change (1.9 %) and cell volume expansion (5.9 %) during the charge/discharge process,which are smaller than those of most of the reported cathode materials (Supporting Information, Figure S8). [22,34,36,39,40] Figure 2. a) CV curves and b) charge/discharge curves of KNiHCF electrodes.c)Comparison of discharge voltages of the KNiHCF electrodes with other as-reported cathodes for PIBs (S, [29] K 0.7 Fe 0.5 Mn 0.5 O 2 , [30] 3,4,9,10-perylene-tetracarboxylicacid-dianhydride(PTCDA), [31] K 0.6 CoO 2 , [32] [33] Na 3 V 2 (PO 4 ) 2 F 3 , [34] [35] and KVPO 4 F [36] ).…”

“…Thec alculated K + diffusion coefficients of KNiHCF were between 10 À11 and 10 À9 cm 2 s À1 during the charge/discharge processes (Figure 4a), which are higher than those of most reported cathode materials (Supporting Information, Figure S11), indicating the fast K + diffusion kinetics. [17,[40][41][42][43][44][45][46] Theh igh K + diffusion coefficient is responsible for the outstanding rate performance of KNiHCF electrode.M oreover,t he batteries possess low charge-transfer resistance (Supporting Information, Figure S12), which is also beneficial for improving the rate performance.…”

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

“…Recently, a new layered compound K 0.83 V 2 O 5 with a higher K content was synthesized by Zhang et al, via the chemical potassiation of γ‐V 2 O 5 . [ 82 ] This material delivered an initial charge capacity of 86 mAh g −1 (extraction of 0.68 eq. K + ) and a discharge capacity of 97 mAh g −1 , with a high cycling stability of over 200 cycles (84.2%).…”

Morphology control and interface characteristics of well-dispersed nanomaterials in K-ion batteries

“…KIBs, which have a working mechanism similar to that of LIBs, have drawn much interest as power sources for large-scale grid energy storage because of their low cost and the abundance of potassium resources. [10][11][12] Since perovskite uoride had been proved to be a potential electrode material for LIBs and sodium ion batteries (NIBs), this provided a reference for studying such materials in KIBs. Due to its abundant reserves and environmental friendliness, manganese-based materials have received extensive attention as electrode materials for various types of batteries such as LIBs, 13 NIBs 14,15 and ow batteries.…”