A Layered Inorganic–Organic Open Framework Material as a 4 V Positive Electrode with High‐Rate Performance for K‐Ion Batteries

Abstract

K‐ion batteries (KIBs) are promising for large‐scale energy storage owing to various advantages like the high abundance of potassium resources in the Earth's crust, high operational potentials, and high power due to fast diffusion of K+ ions. However, to realize the practical application of KIBs, electrode materials are needed with high operational voltage, good capacity, long cycle life, and low‐cost. This work reports a layered open framework material, K2[(VOHPO4)2(C2O4)], composited with reduced graphene oxide (rGO) as a 4 V positive electrode material for KIBs. The material is prepared by a simple precipitation reaction at room temperature. The material demonstrates reversible K‐extraction/insertion with conventional carbonate ester KPF6 solutions; however, with low specific capacity and low Coulombic efficiency. A high discharge capacity of >100 mAh g−1 with good cycling stability and higher Coulombic efficiency is achieved in a highly concentrated electrolyte, 7 mol kg−1 of potassium bis(fluorosulfonyl)amide (KFSA) in dimethoxyethane (DME) at 0.1 C rate. Due to the facile migration of K+ ions in the framework, the material exhibits excellent rate capability with a discharge capacity of 80 mAh g−1 at 10 C rate, and a good capacity retention of 67% after 500 cycles at 2 C rate.

Review on Recent Advances of Cathode Materials for Potassium‐ion Batteries

“…In terms of anode materials, so far carbonaceous materials, [25,[29][30][31][32][33][34] alloy-based materials, [35][36][37][38][39] conversion-type materials, [40,41] and organic materials [42,43] have been widely studied. As for cathodes materials, there are mainly four categories which have been developed and evaluated, that is, Prussian blue (PB) and its analogs, [44][45][46][47][48][49][50][51][52][53][54] layered metal oxides, [55][56][57][58][59][60][61][62][63][64][65][66] poly-anion oxides, [67][68][69][70][71][72][73][74] and organic compounds. [75][7...…”

“…In terms of anode materials, so far carbonaceous materials, alloy‐based materials, conversion‐type materials, and organic materials have been widely studied. As for cathodes materials, there are mainly four categories which have been developed and evaluated, that is , Prussian blue (PB) and its analogs, layered metal oxides, poly‐anion oxides, and organic compounds . Though high capacities (e.g., ≥300 mAh g −1 ) can be readily achieved for the anode materials, the inferior capacities for cathodes, which is usually less than of 100 mAh g −1 , dramatically drive the energy densities of the full PIBs to an unsatisfactory level.…”

A phosphite-based layered framework as a novel positive electrode material for Na-ion batteries

“…[19][20][21] These metal organic phosphate/phosphite open frameworks (MOPOFs) were reported earlier as reversible Li-ion and K-ion hosts with excellent electrochemical properties. [21][22][23][24] For example, K-half cells with rGO/K 2 [(VOHPO 4 ) 2 (C 2 O 4 )] composite as a positive electrode delivered a reversible capacity of >100 mAh g -1 at an average voltage of ~3.85 V and a superior rate performance. 22 In addition, an oxalate sulphate framework material, Na 2 Fe(C 2 O 4 )SO 4 ⋅H 2 O demonstrated 3 V operation as a positive electrode for SIBs.…”

“…[21][22][23][24] For example, K-half cells with rGO/K 2 [(VOHPO 4 ) 2 (C 2 O 4 )] composite as a positive electrode delivered a reversible capacity of >100 mAh g -1 at an average voltage of ~3.85 V and a superior rate performance. 22 In addition, an oxalate sulphate framework material, Na 2 Fe(C 2 O 4 )SO 4 ⋅H 2 O demonstrated 3 V operation as a positive electrode for SIBs. 25 With two distinct channels of 5.907 and 4.126 Å, the material demonstrates facile Na migration and delivered a capacity close to its theoretical value of 88 mAh g −1 and good cycle stability over 500 cycles.…”

A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion storage

“…For KIB technologies, several families have been explored as anode materials with high capacity and long cyclability, including intercalation-type, conversion-type, and alloying type materials [8][9][10][11][12][13][14][15][16]. In comparison, the development of ideal cathode materials, such as Prussian blue analogues (PBAs), oxides, polyanions, and organics [17][18][19][20][21][22] are sluggish. For instance, despite of enormous investigations on PBAs, of which the three-dimensional (3D) open framework structure is promising for K-ion storage, the preparation of defect-free and water-free PBAs is difficult, which deteriorates the electrochemical performance of PBAs in terms of kinetics, Coulombic efficiency (CE), and cycling life [23][24][25][26].…”