Supplementary Information s52

Supplementary Information

Cu/Li4Ti5O12 scaffold as superior anode for lithium-ion batteries

Xi Wang,1,2 Dequan Liu,1,2 Qunhong Weng,1 Jiangwei Liu,1 Qifeng Liang3 and Chao Zhang1

E-mail: wang xicas @ gmail.com or [email protected] Synthetic process of 3D nanoporous Cu/LTO scaffold electrode:

Etching 1) Growth

2) Annealing

under Ar/H2

AlCu alloys Nanoporous Cu scaffolds (NPCu) Cu/LTO scaffold hybrids

Ti3+ Ti3+

Hydrogenation

Al Cu Li4Ti5O12 (LTO NPs) nanoparticles

Figure S1. Schematic illustration of the fabrication process for nanoporous

Cu/Li4Ti5O12 hybrid materials by de-alloying Cu50Al50 (at%) using NaOH and then directly growing Li4Ti5O12 (purple) onto nanoporous Cu, followed by annealing treatment under Ar/H2. Note that hydrogenation effect in presence of H2 could cause the reduction of partial Ti4+ to Ti3+ ions in the formation process of LTO, and thereby further enhance the electronic conductivity. Cu/LTO scaffolds * Cu Rutile TiO ) * 2 0 ) 0 ) . 4 1

( * u 1 ) . ) 1 0 ( ) ) 1 a 4 3 1 ( 1 ) 4

3 3 3 1 ( ( 3 5 3 y ( (

t 3 ( i s n e t Li4Ti5O12 n I

10 20 30 40 50 60 70 2(degree)

Figure S2. XRD pattern: XRD pattern of as-synthesized Cu/LTO in the 2θ range of

10-70° 500 nm

Figure S3. Large-scale SEM image of Copper scaffold template. a) Cu : (111) plane: 0.21 nm b) LTO: (111) plane: 0. 47 nm

LTO (111)

Cu (111)

Figure S4. DFT calculations of surface energies of LTO and Cu and the relaxed interfacial structure: a) The cubic structure of Copper (space group Fm333 m), where the pink color plane indicates the (111) plane of Cu. b) The spinel structure of

Li4Ti5O12 (space group Fd333 m), where the yellow color plane corresponds to the (111) plane of LTO. c) The calculated surface energy of Copper on the different exposed planes. d) The relaxed interfacial structure between LTO (111) and Cu (111) simulated by DFT calculations. 300 ) g

/ 200 h A m (

i 100 Charge c Discharge a p a C 0

0 25 50 Cycles (n)

Figure S5. The cycling performance of Cu/LTO at 0.1C. a) b) 3+ LTO nanoparticles Ti Cu/LTO scaffolds ) . ) u . .

u 3+ a .

t s i n s e n t e n t I n I e- Ti3+ Ti3+ e-

468 466 464 462 460 458 456 454 468 466 464 462 460 458 456 454 Binding Energy (eV) Binding Energy (eV) Figure S6. a) The normalized XPS Ti2p overlay spectra of as-made Cu/LTO and LTO nanoparticles (NPs), b) The difference in their spectra (“Cu/LTO” minus “LTO NPs” shown in Figure S6a). Compared with the XPS spectrum of Ti 2p of LTO NPs, a small negative shift can be observed in the XPS spectrum of hydrogenated Cu/LTO, demonstrating that treatment with hydrogen caused a change of surface bonding of LTO NPs. 3 LTO (111) ) i L / +

. s v 1 V (

t 0 l o V -1 4 5 6 7 8 9

x in LixTi5O12 Figure S7. The calculated voltage profile based on DFT1: The calculated voltage profile for LTO (111) in the Li4Ti5O12-LixTi5O12 system. The blue dash corresponds to the total number of the inserted Li ion when the LTO discharges to 1V and 0 V. 1. S. Ganapathy, et al. ACS Nano 2012, 6, 8702. (111) stepped

Figure S8. STEM-HAADF image of the edge of Cu/LTO, which has the highly exposed (111) facets with atomic kinks. Scale bar: 1 nm.