TY - JOUR
T1 - Solvent-directed sol-gel assembly of 3-dimensional graphene-tented metal oxides and strong synergistic disparities in lithium storage
AU - Ye, Jianchao
AU - An, Yonghao
AU - Montalvo, Elizabeth
AU - Campbell, Patrick G.
AU - Worsley, Marcus A.
AU - Tran, Ich C.
AU - Liu, Yuanyue
AU - Wood, Brandon C.
AU - Biener, Juergen
AU - Jiang, Hanqing
AU - Tang, Ming
AU - Wang, Y. Morris
N1 - Funding Information:
Discussion with J. Lee, T. van Buuren, A. Wittstock, M. D. Merrill, and B. Sadigh is acknowledged. The work was performed under the auspices of the US Department of Energy by LLNL under contract No. DE-AC52-07NA27344. The project is supported by the Laboratory Directed Research and Development (LDRD) programs of LLNL (12-ERD-053). Y. L. acknowledges the support by US Department of Energy under Contract No. DE-AC36-08GO28308. The ?rst-principles calculations were performed by using NREL Peregrine supercomputer, as well as LLNL CAB supercomputer. H. J. acknowledges the support from NSF CMMI-1067947 and CMMI-1162619. M.T. acknowledges support from DOE Office of Basic Energy Sciences Physical Behavior of Materials Program under grant number DESC0014435.
Publisher Copyright:
© The Royal Society of Chemistry 2016.
PY - 2016
Y1 - 2016
N2 - Graphene/metal oxide (GMO) nanocomposites promise a broad range of utilities for lithium ion batteries (LIBs), pseudocapacitors, catalysts, and sensors. When applied as anodes for LIBs, GMOs often exhibit high capacity, improved rate capability and cycling performance. Numerous studies have attributed these favorable properties to a passive role played by the exceptional electronic and mechanical properties of graphene in enabling metal oxides (MOs) to achieve near-theoretical capacities. In contrast, the effects of MOs on the active lithium storage mechanisms of graphene remain enigmatic. Via a unique two-step solvent-directed sol-gel process, we have synthesized and directly compared the electrochemical performance of several representative GMOs, namely Fe2O3/graphene, SnO2/graphene, and TiO2/graphene. We observe that MOs can play an equally important role in empowering graphene to achieve large reversible lithium storage capacity. The magnitude of capacity improvement is found to scale roughly with the surface coverage of MOs, and depend sensitively on the type of MOs. We define a synergistic factor based on the capacity contributions. Our quantitative assessments indicate that the synergistic effect is most achievable in conversion-reaction GMOs (Fe2O3/graphene and SnO2/graphene) but not in intercalation-based TiO2/graphene. However, a long cycle stability up to 2000 cycles was observed in TiO2/graphene nanocomposites. We propose a surface coverage model to qualitatively rationalize the beneficial roles of MOs to graphene. Our first-principles calculations further suggest that the extra lithium storage sites could result from the formation of Li2O at the interface with graphene during the conversion-reaction. These results suggest an effective pathway for reversible lithium storage in graphene and shift design paradigms for graphene-based electrodes.
AB - Graphene/metal oxide (GMO) nanocomposites promise a broad range of utilities for lithium ion batteries (LIBs), pseudocapacitors, catalysts, and sensors. When applied as anodes for LIBs, GMOs often exhibit high capacity, improved rate capability and cycling performance. Numerous studies have attributed these favorable properties to a passive role played by the exceptional electronic and mechanical properties of graphene in enabling metal oxides (MOs) to achieve near-theoretical capacities. In contrast, the effects of MOs on the active lithium storage mechanisms of graphene remain enigmatic. Via a unique two-step solvent-directed sol-gel process, we have synthesized and directly compared the electrochemical performance of several representative GMOs, namely Fe2O3/graphene, SnO2/graphene, and TiO2/graphene. We observe that MOs can play an equally important role in empowering graphene to achieve large reversible lithium storage capacity. The magnitude of capacity improvement is found to scale roughly with the surface coverage of MOs, and depend sensitively on the type of MOs. We define a synergistic factor based on the capacity contributions. Our quantitative assessments indicate that the synergistic effect is most achievable in conversion-reaction GMOs (Fe2O3/graphene and SnO2/graphene) but not in intercalation-based TiO2/graphene. However, a long cycle stability up to 2000 cycles was observed in TiO2/graphene nanocomposites. We propose a surface coverage model to qualitatively rationalize the beneficial roles of MOs to graphene. Our first-principles calculations further suggest that the extra lithium storage sites could result from the formation of Li2O at the interface with graphene during the conversion-reaction. These results suggest an effective pathway for reversible lithium storage in graphene and shift design paradigms for graphene-based electrodes.
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U2 - 10.1039/c5ta10730j
DO - 10.1039/c5ta10730j
M3 - Article
AN - SCOPUS:84960539770
SN - 2050-7488
VL - 4
SP - 4032
EP - 4043
JO - Journal of Materials Chemistry A
JF - Journal of Materials Chemistry A
IS - 11
ER -