Defect-free potassium manganese hexacyanoferrate cathode material for high-performance potassium-ion batteries

Abstract

Potassium-ion batteries (KIBs) are promising electrochemical energy storage systems because of their low cost and high energy density. However, practical exploitation of KIBs is hampered by the lack of high-performance cathode materials. Here we report a potassium manganese hexacyanoferrate (K2Mn[Fe(CN)6]) material, with a negligible content of defects and water, for efficient high-voltage K-ion storage. When tested in combination with a K metal anode, the K2Mn[Fe(CN)6]-based electrode enables a cell specific energy of 609.7 Wh kg−1 and 80% capacity retention after 7800 cycles. Moreover, a K-ion full-cell consisting of graphite and K2Mn[Fe(CN)6] as anode and cathode active materials, respectively, demonstrates a specific energy of 331.5 Wh kg−1, remarkable rate capability, and negligible capacity decay for 300 cycles. The remarkable electrochemical energy storage performances of the K2Mn[Fe(CN)6] material are attributed to its stable frameworks that benefit from the defect-free structure.

Structural complexity in Prussian blue analogues

“…58 Conversely, larger cations replace interstitial water: hence the limiting stoichiometry K 2 Mn[Fe] is anhydrous. 60 Since interstitial water is relatively labile on heating, the drying conditions used in PBA synthesis can by itself alter their structure. 61 For example, the system Na 2 Mn [Mn] switches between an open monoclinic form and a dense rhombohedral form with the loss of two formula units of H 2 O [Fig.…”

“…We have already seen that this system displays many of the complexities covered in our article, and we now argue that understand-ing the interplay of these various aspects will be key to optimising its performance as a K-ion cathode material. We consider in turn the two key strategies currently proposed in the literature: namely, eradicating vacancies altogether, 60 and actively including vacancies in concentrations as large as 15%. 53 The first strategy is based on the assumption that, by removing vacancies from the structure, one can at once both maximise capacity and remove water entirely from the framework.…”

Lignin-Based Materials for Sustainable Rechargeable Batteries

“…Over the last decades, LIB technology has advanced tremendously, enhancing the energy density, cycle life, safety, and cost-efficiency [17][18][19][20][21][22][23]. Simultaneously, researchers actively pursue post-LIB technology such as solid-state, alkaline metal/ion (Na, K), and multivalent-ion (Mg, Ca, Al) batteries for further development [24][25][26][27][28][29][30]. Even though batteries are beneficial for the environment, many components in the battery are synthetic chemicals that are harmful to the environment during production and processing.…”

Potassium manganese hexacyanoferrate with improved lifespan in Zn(CF3SO3)2 electrolyte for aqueous zinc-ion batteries

“…M-HCFs are widely used in various metal-ion batteries as cathode materials, such as Li-, 17,18 Na-, 19–21 K-, 22–24 and Zn-ion batteries, 16,25,26 providing excellent energy storage performance. Until now, several M-HCFs, for instance, Zn-HCF, 27,28 Cu-HCF, 26,29 and Co-HCF, 13,30 have been developed as cathode materials in the ARZIBs.…”

“…Mn-HCF with two redox-active sites, which has a high operating potential and long cycle life in Na-ion and K-ion batteries, 22,31 would also be a promising cathode material for ARZIBs. Deng et al 22 developed a potassium manganese hexacyanoferrate material with negligible vacancy defects and water for K-ion batteries, achieving 80% capacity retention after 7800 cycles. However, the application of Mn-HCF in ARZIBs still needs further exploration.…”