Constructing MoO₂ Porous Architectures Using Graphene Oxide Flexible Supports for Lithium Ion Battery Anodes

Abstract

the theoretical capacity of graphite electrodes is 372 mAh g −1 , resulted in an obstacle for their potential applications. The strategies to develop alternative anode materials with improved capacity have been achieved for several decades. [1][2][3][4][5][6][7][8] Among them, nanoscale metal oxides, including MnO, [9] SnO 2 , [10,11] Co 3 O 4 , [12] NiO, [13] and Fe 3 O 4 , [14,15] used as anode active materials for LIBs have been paid much attention attributed to their promising theoretical capacity. However, in most cases, the capacity decays rapidly as cycled due to high electrical resistivity and mechanism failure. [16] Molybdenum oxide (MoO 2 ) is different from other metal oxides. It possesses metallic conductivity (its electrical resistivity is 8.8 × 10 −5 Ω cm at 300 K in bulk sample), with a theoretical capacity as high as 836 mAh g −1 . [17] However, the capacity of bulk MoO 2 is low due to sluggish lithiation/delithiation kinetics. [17][18][19][20] On the other hand, the nanoporous structure constructed with lots of interconnect nanounits to form numbers of nanoscale pore provides adequate spaces for electrochemical reaction and connected pathways for ion diffusion. [21,22] The nano-MoO 2 porous structures have been synthesized by using mesoporous silica as hard templates, followed removing this hard templates by hydrofluoric acid, [23] or by a sulfur-assisted decomposition process. [24] The prepared MoO 2 porous materials have displayed improved capacity for LIBs. However, the capacity fade after charge/discharge process is attributed to the pure MoO 2 skeleton that will be possibly collapsed. The cycle stability needs to be improved further. It should be desired for the MoO 2 porous structure with flexible supports via retarding the pulverization from pure MoO 2 skeleton.Carbon nanomaterials, especially, graphene with large specific surface area and high toughness, are suitable for both substrates and supports for MoO 2 electrode active materials. However, owing to graphene being liable to stack together, it is difficult to prepare well distributed graphene templated metal oxide architectures. The strategies, including solid-state graphenothermal reduction method, [25] microwave-assisted hydrothermal process, [26] and soft-templated hydrothermal method, [27] have been used to synthesize MoO 2 /C nanocomposites, exhibiting promising performance for LIBs. In our present

Formation of hollow MoO 2 @C nano‐octahedrons using polyoxometalate‐based metal‐organic framework as a template for enhanced lithium‐ion batteries

“…The capacity fade of the MoO 2 @C electrode during the first 20 cycles is related to an activation process that is normally occurring to nanoscale MoO 2 . The phenomenon has also been reported by other groups and may be attributed to partial crystallinity loss of the material or the transformation from a crystalline state to an amorphous‐like structure during cycling 14,55,73‐75 . On the other hand, it is also generally attributed to the reversible growth of a polymeric gel‐like film resulting from kinetically activated electrolyte degradation with the increase of cycling times 76‐79 …”

“…The phenomenon has also been reported by other groups and may be attributed to partial crystallinity loss of the material or the transformation from a crystalline state to an amorphous-like structure during cycling. 14,55,[73][74][75] On the other hand, it is also generally attributed to the reversible growth of a polymeric gel-like film resulting from kinetically activated electrolyte degradation with the increase of cycling times. [76][77][78][79] The enhanced capacity of the prepared MoO 2 @C material is the result of its hollow structure which guarantees full contact between the electrode and the electrolyte, good infiltration of the electrolyte, short lithium-ion diffusion distance and excellent structural integrity.…”

“…372 mAh g −1 , which cannot meet the current needs of high efficiency and energy saving. [14][15][16] So that many potential anode materials are reported over the past decades, such as TiO 2 20,[24][25][26][27][28][29][30] ZnO, 17,18,31,32 MnO 2 , 33,34 NiO, 26,35,36 CuO 37,38 and MoO 2 . 39,40 MoO 2 , which bears discrepant crystallinity and shows unique boundaries, can improve the diffusion of Li + ions.…”

“…But, the traditional graphite anode material of LIB shows a poor theoretical capacity of ca. 372 mAh g −1 , which cannot meet the current needs of high efficiency and energy saving 14‐16 . So that many potential anode materials are reported over the past decades, such as TiO 2 17‐18, Fe 2 O 3 19‐21 SnO 2 ,22,23 Co 3 O 4 , 20,24‐30 ZnO, 17,18,31,32 MnO 2 , 33,34 NiO, 26,35,36 CuO 37,38 and MoO 2 39,40 .…”

Natural‐Light‐Initiated 3D Macro Zigzag Architecture of Graphene‐Reinforced Polystyrene for Gravity‐Driven Oil and Water Separation

“…Recently, 2D graphene and its derivatives have received extraordinary attention due to their unique physicochemical properties. Graphene and its derivatives are extensively used to improve the chemical, electrical, mechanical, and thermal behavior of materials . Graphene, apart from its excellent electrochemical properties, also possesses amazing hydrophobic properties .…”