High‐Rate and Ultralong Cycle‐Life Potassium Ion Batteries Enabled by In Situ Engineering of Yolk–Shell FeS₂@C Structure on Graphene Matrix

Abstract

expected to be a promising candidate for emerging smart grid technology in the near future. Nevertheless, the scarcity and uneven distribution of lithium resources hamper its further development. In pursuit of alternatives to LIBs for large-scale applications, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have great potential, owing to the low cost and high abundance of Na (2.36 wt%) and K (2.09 wt%) in the Earth's crust, as well as its similar chemical properties to those of lithium. [1][2][3][4][5] Much work so far has focused on SIBs, and significant progress has been achieved in the past few years. [6][7][8] On the contrary, the development of PIBs is still in its infancy, probably due to the larger ionic radius of K + (1.38 Å) than those of Na + (1.02 Å) and Li + (0.76 Å). [9] However, PIBs possess several advantages compared with SIBs, such as the more negative standard potential of K + /K (−2.93 V vs SHE, compared with −2.71 V for Na + / Na), reversible intercalation/deintercalation of K + in graphite (theoretical capacity of 279 mA h g −1 ), and fast ionic conductivity of K + in liquid electrolyte. [10][11][12] These properties of PIBs offer exciting opportunities to achieve low-cost batteries with high energy density and good rate performance. Nevertheless, it remains challenging to fabricate suitable electrode materials, The potassium-ion battery (PIB) represents a promising alternative to the lithium-ion battery for large-scale energy storage owing to the abundance and low cost of potassium. The lack of high performance anode materials is one of the bottlenecks for its success. The main challenge is the structural degradation caused by the huge volume expansion from insertion/extraction of potassium ions which are much larger than their lithium counterparts.Here, this challenge is tackled by in situ engineering of a yolk-shell FeS 2 @C structure on a graphene matrix. The yolk-shell structure provides interior void space for volume expansion and prevents the aggregation of FeS 2 . The conductive graphene matrix further enhances the charge transport within the composite. The PIB fabricated using this anode delivers high capacity, good rate capability (203 mA h g −1 at 10 A g −1 ), and remarkable long-term stability up to 1500 cycles at high rates. The performance is superior to most anode materials reported to date for PIBs. Further in-depth characterizations and density functional theory calculations reveal that the material displays reversible intercalation/deintercalation and conversion reactions during cycles, as well as the low diffusion energy barriers for the intercalation process. This work provides a new avenue to allow the proliferation of PIB anodes.

A Robust Solid Electrolyte Interphase Layer Augments the Ion Storage Capacity of Bimetallic‐Sulfide‐Containing Potassium‐Ion Batteries

“…[19] Xie et al prepared MoS 2 /reduced graphene oxide (RGO) composites by as olvothermal route,which delivered ah igh initial reversible specific capacity of 353 mAh g À1 at 100 mA g À1 . [21] Nevertheless,a sac onsequence of sluggish electrochemical reaction kinetics most transition-metal sulfides cannot meet the requirements of high capacity,g ood rate capability,a nd long cycling life typically demonstrated by NIBs. [21] Nevertheless,a sac onsequence of sluggish electrochemical reaction kinetics most transition-metal sulfides cannot meet the requirements of high capacity,g ood rate capability,a nd long cycling life typically demonstrated by NIBs.…”

“…[20] Zhao et al synthesized yolk-shell FeS 2 @C structure composites by awet-chemical method with thermal treatment;the material maintained acapacity of 270 mAh g À1 at 300 mA g À1 after 1000 cycles. [21] Nevertheless,a sac onsequence of sluggish electrochemical reaction kinetics most transition-metal sulfides cannot meet the requirements of high capacity,g ood rate capability,a nd long cycling life typically demonstrated by NIBs.…”

Interlayer Expanded SnS2 Anchored on Nitrogen‐Doped Graphene Nanosheets with Enhanced Potassium Storage

“…[19][20][21][22] More importantly, the typical narrow-band gap semiconductor characteristic and intrinsic stacked interlayer nanostructure are more preferable to the (de)intercalation process of alkali-ion, showing a great potential application in PIB. [19,20] For examples, Ren has synthesized a two-dimensional layered MoS 2 as anode for PIB, exhibiting a superior capacity retention of 97.5 % after 200 cycles at 0.2 A g À 1 . [21] Gao has prepared CoS nanoclusters anchored on graphene ultrathin sheets to provide a sturdy structure and alleviate the electrochemical deteriorate, these composite could deliver an excellent capacity of 310.8 mAh g À 1 after 100 cycles.…”

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

“…[28] Therefore, it is necessary to optimize and improve the electrochemical performance of the battery by studying the reaction mechanism. [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. [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.…”