Direct Growth of MoO₂/Reduced Graphene Oxide Hollow Sphere Composites as Advanced Anode Materials for Potassium‐Ion Batteries

Abstract

Hollow MoO2/reduced graphene oxide (MoO2/rGO) sub‐microsphere composites have been fabricated through a simple hydrothermal approach followed by a heat treatment process. When employed as an anode material for potassium‐ion batteries, the as‐synthesized MoO2/rGO composite can deliver an initial charge specific capacity of 367.2 mAh g−1 at 50 mA g−1, and its reversible capacity is 218.9 mAh g−1 after 200 cycles. Even when cycled at 500 mA g−1, a high charge specific capacity of 104.2 mAh g−1 is achieved after 500 cycles. The excellent cycling capability and rate performance may be ascribed to the synergistic effects of the reduced graphene oxide and the hollow MoO2 spheres, which can increase the electrical conductivity of the composite, as well as resisting the strain arising from the repeated discharge–charge processes. These results indicate that the MoO2/rGO hollow sphere composites are promising negative electrode materials for potassium‐ion batteries.

Nature of Bimetallic Oxide Sb2MoO6/rGO Anode for High‐Performance Potassium‐Ion Batteries

“…In the subsequent scans, these two peaks disappear. However, a strong cathodic peak of the MoO 2 /rGO composites around 0.01 V corresponding to the insertion of K + into the K–Mo–O matrix and an anodic peak located at about 0.29 V indexed to the extraction of K + from the K–Mo–O matrix are retained …”

“…The option of the KFSI electrolyte is according to the previous study, [46][47][48] which could form a highly stable inorganic solid-electrolyte interphase (SEI) layer that is different from the SEI film primarily composed of organic components generated from the traditional KPF 6 suppressing the development of potassium dendrites, avoiding excessive side reactions, and reducing the polarization. [29,30] The typical charge/discharge curves of Sb 2 MoO 6 /rGO electrode at a current density of 100 mA g −1 are shown in Figure 3b. In the first cathodic scan, a broad peak appears at 0.50 V, which is primarily associated with the intercalation of K + into Sb 2 MoO 6 crystal, formation of SEI, and reduction of Sb 3+ to Sb.…”

“…Besides the carbonaceous anodes (graphite, soft carbon, hard carbon, etc.) which are being explored vigorously but yield a relatively low specific capacity, metal oxides, such as iron oxides, molybdenum oxides, niobium pentoxides, tin oxides, and titanium oxides, are interesting anode candidates considering their high gravimetric and volumetric specific capacity, which are able to provide high performance anodes for KIBs . For example, antimony oxide (Sb 2 O 3 ) possesses a theoretical capacity as high as 1103 mAh g −1 for KIBs through both conversion reactions and alloy reactions.…”

“…[1][2][3][4][5] Because of the natural abundance of potassium, a similar redox potential of potassium to lithium, and the low cost, potassiumion batteries (KIBs) serve as a promising substitution to LIBs, [6][7][8][9][10][11] especially attractive in the largescale energy storage systems which strive intensively to lower the price to be competitive with other energy storage techniques. which are being explored vigorously but yield a relatively low specific capacity, [17][18][19][20][21][22][23][24][25][26][27] metal oxides, such as iron oxides, [28] molybdenum oxides, [29,30] niobium pentoxides, [31] tin oxides, [32] and titanium oxides, [33] are interesting anode candidates considering their high gravimetric and volumetric specific capacity, which are able to provide high performance anodes for KIBs. [12][13][14][15][16] Therefore, searching for the high performance KIBs anode (a critical component of KIBs) to alleviate the dramatic volume change is highly demanded to build high performance KIBs.…”

“…which are being explored vigorously but yield a relatively low specific capacity, [17][18][19][20][21][22][23][24][25][26][27] metal oxides, such as iron oxides, [28] molybdenum oxides, [29,30] niobium pentoxides, [31] tin oxides, [32] and titanium oxides, [33] are interesting anode candidates considering their high gravimetric and volumetric specific capacity, which are able to provide high performance anodes for KIBs. which are being explored vigorously but yield a relatively low specific capacity, [17][18][19][20][21][22][23][24][25][26][27] metal oxides, such as iron oxides, [28] molybdenum oxides, [29,30] niobium pentoxides, [31] tin oxides, [32] and titanium oxides, [33] are interesting anode candidates considering their high gravimetric and volumetric specific capacity, which are able to provide high performance anodes for KIBs.…”