Supporting Information Self-supported Ultrathin Mesoporous Nanosheet Arrays Assembled From Nanowires with Enhanced Lithium Storage Performance Jiwei Wang, Hui Zhang, XiaoxinLv, KaiqiNie, XuejieGao, Jun Zhong and Xuhui Sun* Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University,Suzhou, Jiangsu 215123, P.R.China Figure S1 SEM images of CoO nanowires(a), Fe2O3/Co2(CO3)(OH)2 nanowires(b) , CoFe2O4/CoO nanosheets(c) and magnified image of nanosheets grown on Ni foam. Figure S2 TEM images of the CoFe2O4/CoO NSs at different magnification. Figure S3 XRD patterns of Co2(CO3)(OH)2 NWs, pure CoO NWs and CoFe2O4/CoO NSs. Figure S4 Equivalent circuit for the electrochemical impedance spectroscopy, Re: The electrolyte resistance, Rct: The charge transfer resistance, Zw: The Warburg diffusion resistance, Cdl: The double layer capacitance, RMO: The internal resistance of metal oxides, CMO: The pseudo-capacitance of metal oxides. Figure S5 SEM images of CoO NWs and CoFe2O4/CoO NSs after 50 cycles at 0.5C Table S1. Summary of electrochemical performance data for CoOx-based anodes in LIBs Reversible capacity after Current CoOx-based anodes Reference -1 (W) cycles (mAhg ) density(A g-1) SiO2/CoO NWs on Cu foil 1250 after 200 cycles 0.716  CoO@C wall arrays on Ni foam 804 after 60 cycles 0.5  CoO nanosheet arrays on Ni foam 1495 after 100 cycles 1  Branched Co3O4/Fe2O3 NWs 980 after 60 cycles 0.1  Mesoporous NiCo2O4 NWs/Carbon Textiles 854 after 100 cycles 0.5  CoO/carbon nanofiber networks 633 after 52 cycles 0.1  Hollow CoO 832 after 50 cycles 0.0716  CoFe2O4/CoO NSs on Ni foam 1043 after 50 cycles 0.358 This work 1 K Cao, L Jiao, Y Liu, H Liu, Y Wang, H Yuan, (2015). Ultra-High Capacity Lithium-Ion Batteries with Hierarchical CoO Nanowire Clusters as Binder Free Electrodes. Advanced Functional Materials, 25(7): 1082-1089. 2 F Wu, X Ma, J Feng, Y Qian, S Xiong, (2014). 3D Co3O4and CoO@C wall arrays: morphology control, formation mechanism, and lithium-storage properties. Journal of Materials Chemistry A, 2(30): 11597. 3 D Li, L-X Ding, S Wang, D Cai, H Wang, (2014). Ultrathin and highly-ordered CoO nanosheet arrays for lithium-ion batteries with high cycle stability and rate capability. Journal of Materials Chemistry A, 2(16): 5625. 4 H Wu, M Xu, Y Wang, G Zheng, (2013). Branched Co3O4/Fe2O3 nanowires as high capacity lithium-ion battery anodes. Nano Research, 6(3): 167-173. 5 L Shen, Q Che, H Li, X Zhang, (2014). Mesoporous NiCo2O4Nanowire Arrays Grown on Carbon Textiles as Binder-Free Flexible Electrodes for Energy Storage. Advanced Functional Materials, 24(18): 2630-2637. 6 M Zhang, E Uchaker, S Hu, et al., (2013). CoO-carbon nanofiber networks prepared by electrospinning as binder-free anode materials for lithium-ion batteries with enhanced properties. Nanoscale, 5(24): 12342-12349. 7 Z Wen, F Zheng, Z Jiang, M Li, Y Luo, (2012). Solvothermal synthesis of solid and hollow CoO nanospheres and their electrochemical properties in lithium-ion battery. Journal of Materials Science, 48(1): 342-347.