Exfoliated Graphene Oxide/MoO₂ Composites as Anode Materials in Lithium-Ion Batteries: An Insight into Intercalation of Li and Conversion Mechanism of MoO₂

Abstract

Exfoliated graphene oxide (EG)/MoO2 composites are synthesized by a simple solid-state graphenothermal reduction method. Graphene oxide (GO) is used as a reducing agent to reduce MoO3 and as a source for EG. The formation of different submicron sized morphologies such as spheres, rods, flowers, etc., of monoclinic MoO2 on EG surfaces is confirmed by complementary characterization techniques. As-synthesized EG/MoO2 composite with a higher weight percentage of EG performed excellently as an anode material in lithium-ion batteries. The galvanostatic cycling studies aided with postcycling cyclic voltammetry and galvanostatic intermittent titrations followed by ex situ structural studies clearly indicate that Li intercalation into MoO2 is transformed into conversion upon aging at low current densities while intercalation mechanism is preferably taking place at higher current rates. The intercalation mechanism is found to be promising for steady-state capacity throughout the cycling because of excess graphene and higher current density even in the operating voltage window of 0.005-3.0 V in which MoO2 undergoes conversion below 0.8 V.

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

“…The capacity of the pure MoO 2 particle baseline displays a continuous decrease to 356 mAh g −1 until the 17th cycle then gradually increase afterward, the capacity reaches to 470 mAh g −1 at the 100th cycle, which is consistent with MoO 2 with the size in microscale. [25,26] As we have already discussed above, the micrometer MoO 2 /GO also exhibits an induced activation process. The discharge capacity of the micrometer MoO 2 /GO decreases to 801 mAh g −1 at the 7th cycle then continuously increases to 901 mAh g −1 at the 100th cycle.…”

“…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 …”

Copper ferrites@reduced graphene oxide anode materials for advanced lithium storage applications

“…The voltage plateau originally seen at 1.2 V is no longer seen. The voltage drops slowly from 3 to 1 V, and then slopes downward till 0.02 V. Moreover, the initial discharge capacity of CuFeO 2 @rGO (985 mAh g −1 ) is remarkably higher than the theoretical capacity of CuFeO 2 (708 mAh g −1 ), which have been found in other metal oxides 12, 13, 32, 47, 57 . The higher initial discharge capacity may be ascribed to structural destruction upon Li insertion and decomposition of the solvent in the electrolyte, subsequent formation of large area solid electrolyte interphase (SEI) layer and nano Cu and Fe in Li 2 O matrix.…”

“…In addition, two well-resolved bands at 1360 and 1590 cm −1 for CuFeO 2 @rGO are attributed to the D band (k-point phonon of A 1 g symmetry) and G band (E 2 g phonon of carbon) of graphene, respectively. Compared with GO ( I D / I G  = 0.86), the increased ratio of the D band to G band ( I D / I G  = 0.97) in CuFeO 2 @rGO suggests the reduction of graphene, which can be ascribed to smaller but more numerous sp 2 domains in carbon 57 . Moreover, the presence of 2D band at 2694 cm −1 and (D + G) band at 2953 cm −1 in Fig.…”

Amorphous Vanadium Oxide Thin Films as Stable Performing Cathodes of Lithium and Sodium-Ion Batteries

“…The values of various circuit elements shown in the corresponding equivalent circuits are furnished in Table 6 for LIBs and Table 7 for SIBs. The circuits shown contain electrolyte-electrode contact resistance R e , resistance due to surface film formation R sf , resistance to charge transfer R ct , bulk (substrate) resistance R b , capacitance components due to surface film formation CPE sf , double layer of charge formation CPE dl , bulk phase CPE b and ionic intercalation C i [31, 39–44]. In case of LIBs cycling, R sf and R ct values varied as 13 Pa < 30 Pa < 6 Pa whilst CPE dl value varied as 30 Pa < 6 Pa < 13 Pa.…”