Enhanced Potassium Ion Battery by Inducing Interlayer Anionic Ligands in MoS_1.5Se_0.5 Nanosheets with Exploration of the Mechanism

Abstract

potential high energy density, resulting from the low standard reduction potential of potassium (−2.93 V vs the standard hydrogen potential, E 0 ), close to that of lithium (−3.04 V vs E 0 ). [1][2][3][4] Based on ab initio molecular dynamics simulations, it has been proven that the diffusion coefficient of K + is about three times larger than that of Li + . [3] Meanwhile, K + has high ion mobility and ionic conductivity in propylene carbonate (PC) electrolyte. Nevertheless, facing the issues arising from it having the largest atomic radius (1.38 Å) compared to lithium (0.68 Å), sodium (0.97 Å), and calcium (1.18 Å), [5][6][7] it is quite challenging to design suitable materials with the capability of highly reversible and long-term K + insertion and extraction processes. [8,9] Based on global academic research, various materials have been explored and designed for KIBs, such as transition metal oxides, carbon-based materials, and polyanion based materials, all of which showed signs of potential higher performance. [10][11][12][13][14][15][16][17][18][19][20][21] Due to their overwhelming advantages, such as large interlayer spacing and reversible conversion efficiency, 2D materials were paid much more attention than bulk materials, and various strategies have been devised to optimize their performance by morphology and physical structure control. [11,[22][23][24][25] Taking molybdenum disulfide (MoS 2 ) as an example, it possesses a graphene-like lamellar structure consisting of metal atoms sandwiched between two layers of chalcogens by weak van der Waals forces. [26][27][28] According to the Randles-Sevcik equation, however, the K + diffusion coefficient will be gradually decreased with higher K + intercalation and MoS 2 reduction, which results in a sluggish kinetic reaction rate and unsatisfactory energy conversion efficiency, particularly at high current density. [25][26][27][28] In additional, MoS 2 nanosheets usually tend to exfoliate and pulverize because of the obvious volumetric changes in the course of long-term ion intercalation, thus resulting in rapid capacity fading and unsatisfactory cycling stability. Here, a desirable approach is used to narrow interlayer energy band of MoS 2 and thus achieve advanced metallic properties by anionic Se doping to form S 1.5 Se 0.5 interlayer ligands, at which an expanded interlayer spacing benefiting for optimal van der Waals forces can be realized as well. This combines the complementary advantages from two kinds of anion ligands with high conductivity and good affinity with The strategy of inducing interlayer anionic ligands in 2D MoS 1.5 Se 0.5 nanosheets is employed to consolidate the interlayer band gap and optimize the electronic structure for the potassium ion battery. It combines complementary advantages from two kinds of anionic ligands with high conductivity and good affinity with potassium ions. The potassium ion diffusion rate is accelerated as well by an optimized lower energy barrier for ion diffusion pathways, with the formation of highly reversible...

Realizing Fast Charge Diffusion in Oriented Iron Carbodiimide Structure for High-Rate Sodium-Ion Storage Performance

“…Transition metal compounds, such as sulfides and oxides, have been extensively investigated as high-performance electrode materials in secondary ion batteries in recent years. These materials present high theoretical storage capacity as well as excellent catalytic properties with improved activity toward electrochemical reactions − with additional charge and discharge capacity. , Nevertheless, transition metal sulfides and oxides usually suffer from drawbacks such as intrinsic weak conductivity during the charge transfer process. This disadvantage often leads to poor kinetics during their electrochemical reactions with faded capacity under high rate storage process.…”

Construction of Novel Bimetallic Oxyphosphide as Advanced Anode for Potassium Ion Hybrid Capacitor

“…The following cycle demonstrates reversible intercalation/deintercalation and conversion reaction respectively between metal oxide/phosphide and K 2 O/K 3 P, which also resulted in the previous report. [28,32] The first-principles calculation based on density functional theory (DFT) was performed in Figure 4 to clarify the mechanism for the mix-anions on the electron properties and K + storage performance enhancement of the NCOP. Notably, one oxygen atom was replaced with a phosphorus atom in the NCO unit cell to understand the structure change trend.…”

“…The following cycle demonstrates reversible intercalation/deintercalation and conversion reaction respectively between metal oxide/phosphide and K 2 O/K 3 P, which also resulted in the previous report. [ 28 , 32 ]…”

Two‐Dimensional Transition Metal Oxides and Chalcogenides for Advanced Photocatalysis: Progress, Challenges, and Opportunities

“…For some layered materials that have interlayer cations or anions to maintain the charge balance, these primary intercalated ions can be replaced by ion exchange to incorporate ions of a larger radius or an altered charge, to thus expand the interlayer distance and weaken the interlayer interaction. The cation exchange‐assisted solution‐phase exfoliation has been explored for KMnO 2 or Na–MnO 2 with interlayer Na + or K + , [ 87 ] H 1.07 Ti 1.73 O 4 ·H 2 O with interlayer H + , [ 88 ] KCa 2 Nb 3 O 10 with interlayer K + , [ 68 ] K 0.4 MoS 2 or K 2 MoS 4 with interlayer K + , [ 89 ] and Li x /Na x /K 0.6 VS 2 with interlayer Li + /Na + /K + . [ 90 ] In the case of Na–MnO 2 , [71b] ion exchange of Na + by H + is conducted by immersing the bulk Na–MnO 2 in 0.1 mol L −1 HCl at room temperature to give the bulk H–MnO 2 precursor.…”