Encapsulation of Nanoscale Metal Oxides into Ultra-thin Ni Matrix for Superior Li-Ion Batteries: A Versatile Strategy

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1 Electronic Supplementary Material (ESI) for Nanoscale. This journal is The Royal Society of Chemistry 14 Nanoscale Dynamic Article Links Cite this: DOI:.39/cxxx ARTICLE TYPE Encapsulation of Nanoscale Metal Oxides into Ultra-thin Ni Matrix for Superior Li-Ion Batteries: A Versatile Strategy Jianhui Zhu, a, b Jian Jiang, a, b Wei Ai, a Zhanxi Fan, c Xintang Huang, b Hua Zhang c and Ting Yu* a, d a Division of Physics and Applied Physics, School of Physical andmathematical Sciences, Nanyang Technological University, , Singapore. YuTing@ntu.edu.sg; b Institute of Nanoscience and Nanotechnology, Department of Physics, Central China Normal University, Wuhan, 4379, Hubei, P.R. China. c School of Materials Science and Engineering, Nanyang Technological University, , Singapore; d Graphene Research Centre, National University of Singapore, 11746, Singapore Experimental Details: 1.1 Preparation of Ni(OH) 2 film:.3g Ni(NO 3 ) 2 6H 2 O and.7g hexamethylenetetramine (HMT) were dissolved in ml distilled water. After 3 min ultrasonication treatment, the transparent suspension was then transferred into a sealed container (8 ml) and held at 9 o C for 6 h. The pure Ni(OH) 2 films can be harvested after wash for several times. 1.2 Preparation of Fe 3 O hybrids: Single-crystalline Fe 3 O 4 hexagonal nanoplates were synthesized by referring to the previous work. 17 In brief, a green mixture of FeSO 4 7H 2 O (.4 g), NaOH (.3 g), ethylene glycol (4 ml) and distilled water (1 ml) was treated by ultrasonication for 3 min, transferred into a Teflonlined stainless steel autoclave and held at 9 o C for h. The as-formed Fe 3 O 4 precipitation was then washed, dried and collected as raw materials for later fabrication. In typical synthesis of Fe 3 O hybrids,.1 g Fe 3 O 4 nanoplates,.7 g HMT,.3 g Ni(NO 3 ) 2 6H 2 O and ml distilled water were mixed and dissolved by ultrasonication for 1 min. The obtained suspension was then transferred into a sealed container (8 ml) and held at 9 o C for 6 h. Later, the Fe 3 O 2 intermediate was collected and washed by distilled water several times. The reduction procedure was performed in a horizontal, quartz tube-furnace system..3 g Fe 3 O 2 (pre-dispersed into ml distilled water, dropped onto a ceramic wafer and dried at 6 o C) were placed into the centre of a quartz tube (tube diameter: 2 inch). 1. ml of ethylene glycol (EG) loaded in an alumina boat was put at the upstream zone of quartz tube. Before heating, the tube reactor was sealed and flushed by Ar gas ( sccm) for min. The furnace was then heated to 6±K at a heating rate of ~ K min -1 under a constant Ar flow of 8 sccm, kept for 1 min and allowed to cool down to room temperature naturally. [journal], [year], [vol], 1

2 1. 3 Preparation of C/CoFeO NWAs: The C/CoFeO x NWAs were applied a directly as raw materials and synthesized according to our previouss work. In brief, one piece of Fe-Co-Ni alloy substrate with C/CoFeO NWAs (area: cm 2 ) grown on was immersed into a 8 ml container wherein there was a ml homogeneous aqueous solution containing.1 g Ni(NO 3 ) 2 6H 2 O and.3 g HMT. The container was then sealed and held at 9 o C for 6 h. The obtained C/CoFeO x NWAs were fetched out, rinsed and dried at 6 o C. The next reduction treatment was exactly the same with that of Fee 3 O hybrids except that the C/ /CoFeO 2 NWAs replaced the above Fee 3 O 2. O x 2. Figures 1 Fig. S1 (A-C) SEM and (D) TEM observations onn sheet-like ultra-thin Ni( (OH) 2 nanofilms. (E) XRD pattern of as-formed Ni( OH) 2 products. Inset in Fig. S1(D) shows their SAED spectrum. 2 2 Journal Name, [year], [vol],

3 Fig. S2 XRD patterns showing the evolution processs of core-shell hybrid nanowires. Fig. S3 (A-B) TEM and (C) HRTEM images of the MnO 2 intermediate. 1 Journal Name, [year], [vol], 3

4 (a) 1 1 Mn Ka Counts (a.u.) 9 6 O Ka Mnn Kb Ni Ka 3 Ni Kb 1 Energy (kev) (b) 4 1 Counts (a.u.) Ni 3 CO Energy (kev) 4 6 Fig.S4 (a) EDS spectrum of MnO@Ni core-shell hybrid NWs; (b) EDS spectrum and SEM image (inset) of Ni products evolved from pure Ni(OH) 2 thin films Journal Name, [year], [vol],

5 Fig. S (A) XRD patterns monitoring the evolution process of Fe 3 O hybrid. SEM observations toward samples within different evolution stages: (B-C) the pristine Fe 3 O4 nanoplates, (D-E) the intermediate Fe 3 O 2 and (F) the final products of Fe 3 3O hybrid. 1 Fig.S6 XRD patternn of CoO@Ni core-shell hybrid h NWs.. Journal Name, [year], [vol],

6 Fiig. S7 SEM M observationns monitorin ng the overa rall evolution n of C/CoFeOx@Ni NW WAs: (A-B) the pristinee C//CoFeOx NW WAs, (C-D)) the interm mediate C/C CoFeOx@Ni(OH)2 NWA As and (E-FF) the final products of o C/ /CoFeOx@N Ni NWAs. Fig. S8 (A-B) SEM and (C-D) TEM T images of MnO@Ni hybrids afteer chargge-discharge cycles. 6 JJournal Name, [year], [vol], This journal is The Royyal Society of Chemistry C [yearr]

7 8 6 MnO@Ni Nanowires Pure MnO Nanowires -Z'' (ohm) Z' (ohm) 1 14 Fig.S9 EIS spectra of pure MnO and MnO@Ni hybrid nanowires. Fig. S (A) Cyclic comparison off pure CoFeO x NWAs, C/CoFeO x NWAs N and C/CoFeO NWAs at a constant current density of ~3 ma/g; (B) Charge/discharge profiles of C/CoFeOO NWAs in a voltage window of.-3v at ~3 ma/g; (C) Charge/discharge profiles of C/CoFeOC NWAs performed under varied current densities; (D) Comparison of rate capabilities on bare CoFeOC x NWAs, C/CoFeO x NWAs and C/CoFeO NWAs. Journal Name, [year], [vol], 7