Expanded MoSe₂ Nanosheets Vertically Bonded on Reduced Graphene Oxide for Sodium and Potassium-Ion Storage

Abstract

The cost-efficient and plentiful Na and K resources motivate the research on ideal electrodes for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). Here, MoSe2 nanosheets perpendicularly anchored on reduced graphene oxide (rGO) are studied as an electrode for SIBs and PIBs. Not only does the graphene network serves as a nucleation substrate for suppressing the agglomeration of MoSe2 nanosheets to eliminate the electrode fracture but also facilitates the electrochemical kinetics process and provides a buffer zone to tolerate the large strain. An expanded interplanar spacing of 7.9 Å is conducive to fast alkaline ion diffusion, and the formed chemical bondings (C–Mo and C–O–Mo) promote the structure integrity and the charge transfer kinetics. Consequently, MoSe2@5%rGO exhibits a reversible specific capacity of 458.3 mAh·g–1 at 100 mA·g–1, great cyclability with a retention of 383.6 mAh·g–1 over 50 cycles, and excellent rate capability (251.3 mAh·g–1 at 5 A·g–1) for SIBs. For PIBs, a high first specific capacity of 365.5 mAh·g–1 at 100 mA·g–1 with a low capacity fading of 51.5 mAh·g–1 upon 50 cycles and satisfactory rate property are acquired for MoSe2@10%rGO composite. Ex situ measurements validate that the discharge products are Na2Se for SIBs and K5Se3 for PIBs, and robust chemical bonds boost the structure stability for Na- and K-ion storage. The full batteries are successfully fabricated to verify the practical feasibility of MoSe2@5%rGO composite.

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

“…12:K V 5 O 13 @reduced graphene (rGO)//V 2 O 3Àx @rGO, [55] Ref. 13:KFe[Fe-(CN) 6 ]//hard carbon, [50] Ref. 14:K 0.5 V 2 O 5 //Nb 2 O 5Àx @rGO [56] ).…”

“…[8,9] Recently, potassium-ion batteries (PIBs) have received tremendous interests owing to the low redox potential of K + /K in organic electrolyte (À2.93 Vversus standard hydrogen electrode), the abundance of potassium resources,t he weaker Lewis acidity of K + and the practicability of graphite anode. [10][11][12][13] Unfortunately,t he large ionic radius of K + (1.38 )c ould result in large voltage hysteresis and sluggish K + -diffusion kinetics. [14] Furthermore,t he large size of K + generally causes large volume change and high lattice strain during charge/discharge processes and thus deteriorates the cycling performance of host materials.…”

“…However, the limited Li resources and ever‐increasing cost unavoidably hinder the large‐scale application of LIBs in the smart grid [8, 9] . Recently, potassium‐ion batteries (PIBs) have received tremendous interests owing to the low redox potential of K + /K in organic electrolyte (−2.93 V versus standard hydrogen electrode), the abundance of potassium resources, the weaker Lewis acidity of K + and the practicability of graphite anode [10–13] . Unfortunately, the large ionic radius of K + (1.38 Å) could result in large voltage hysteresis and sluggish K + ‐diffusion kinetics [14] .…”

“…11:K 1.92 Fe[Fe-(CN) 6 ] 0.94 •0.5 H 2 O//dipotassium terephthalate@carbonn anotube,[49] Ref. 12:K V 5 O 13 @reduced graphene (rGO)//V 2 O 3Àx @rGO,[55] Ref 13[50] Ref.…”

Research progress of metal selenides anode materials for sodium-ion batteries

“…随着"碳中和、碳达峰"概念的提出，新能源的 重要性日益凸显。作为新能源中应用最广泛的一种， 锂离子电池已经广泛渗透进了人类的日常生活 [1][2] 。 然而，地球上锂资源的储量十分有限，且其分布的不 均匀性导致我国锂离子电池的发展十分容易受到 "卡 脖子"的风险。因此，寻求新型的低成本、资源丰富 的高性能二次电池体系以替代锂离子电池成为能源 可持续发展的关键。钠与锂属于同族元素，从而具有 很多相似的性质， 且钠在地球上储量丰富， 成本低廉， 因此， 钠离子电池已成为未来储能电池发展的重要方 向之一 [3][4][5] [6][7][8][9] 。因此，新型高容量、长循环 寿命的负极材料的研发尤为重要。近年来，碳材料、 合金材料、金属氧/硫/硒化物等均被广泛研究，其中 碳材料循环性能稳定但容量低 [10] ； 合金材料具有高的 理论容量，但存在巨大的体积膨胀 [11] ；金属氧化物理 论容量较高，但电导率较低 [12] 。理想的钠离子电池负 极材料需要满足高导电性、 较小的体积膨胀以及长循 环寿命等要求，因此，金属硫族化合物开始逐渐进入 人们的视野。 图 1 钠离子电池负极材料 [13][14][15][16][17][18] Figure 1 Anode materials of sodium ion batteries 金属硫族化合物包括金属硫化物与金属硒化物， 具有较大的层间距以及较高的理论容量， 因此被认为 是最有应用前景的钠离子电池负极材料。 而硒相比硫 具有更大的原子半径以及更强的金属性， 且金属硒化 物具有更窄的带隙和线宽， 因此具有更高的导电性以 及更大的层间距 [19][20] 。同时，金属硒化物在电化学脱 嵌钠过程中发生转化/合金型反应机理，从而表现出 很高的储钠容量。金属硒化物可以分为层状结构(包 括 MoSe2，SnSe，SnSe2，WSe2，TiSe2 等)及非层状 结构(包括 FeSe2，ZnSe，CoSe2，NiSe2 等) 。层状 结构金属硒化物通常是由金属原子 M 夹在两层硒 (Se)原子之间形成的三层结构(Se-M-Se) ，层间以 共价键相连，而每个结构之间则是以范德华力结合， 钠离子很容易在其中嵌入与脱出； 而非层状金属硒化 物大多可以从天然矿石中提出， 具有低成本以及高理 论容量的优势 [21][22] [26] ； (b) DR-MoSe2 和 DF-MoSe2 的 BET 测试 [27] ； (c) MoSe2-MoO3/C 的 HRTEM 图像 [28] ；(d) MoSe2@rGO 的微观键合，(e) Mo、C 元素分峰图 [29] 。 Figure 2 (a) The migration path of Na between and on the surface of MoS2 [26] ; (b) BET of DR-MoSe2 and DF-MoSe2 [27] ; (c) HRTEM image of MoSe2-MoO3/C [28] ; (d) Microscopic bonding of MoSe2@rGO, (e) XPS fitting curves of Mo and C elements [29] .…”