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"Reviving the lithium metal anode for high-energy batteries" — Dingchang Lin: Yayuan Liu & Yi Cui; Nat Nano, 03/07/17.
Lithium-ion batteries have had a profound impact on our daily life, but inherent limitations make it difficult for Li-ion chemistries to meet the growing demands for portable electronics, electric vehicles and grid-scale energy storage. Therefore, chemistries beyond Li-ion are currently being investigated and need to be made viable for commercial applications. The use of metallic Li is one of the most favoured choices for next-generation Li batteries, especially Li–S and Li–air systems. After falling into oblivion for several decades because of safety concerns, metallic Li is now ready for a revival, thanks to the development of investigative tools and nanotechnology-based solutions. In this Review, we first summarize the current understanding on Li anodes, then highlight the recent key progress in materials design and advanced characterization techniques, and finally discuss the opportunities and possible directions for future development of Li anodes in applications.
"Theoretical Investigation of 2D Layered Materials as Protective Films for Lithium and Sodium Metal Anodes" — Hongzhen Tian: Zhi Wei Seh, Kai Yan, Zhongheng Fu, Peng Tang, Yingying Lu, Ruifeng Zhang, Dominik Legut, Yi Cui, and Qianfan Zhang; Advanced Energy Materials, 02/17/17.
Rechargeable batteries based on lithium (sodium) metal anodes have been attracting increasing attention due to their high capacity and energy density, but the implementation of lithium (sodium) metal anode still faces many challenges, such as low Coulombic efficiency and dendrites growth. Layered materials have been used experimentally as protective films (PFs) to address these issues. In this work, the authors explore using first-principles computations the key factors that determine the properties and feasibility of various 2D layered PFs, including the defect pattern, crystalline structure, bond length, and metal proximity effect, and perform the simulations on both aspects of Li+ (Na+) ion diffusion property and mechanical stability. It is found that the introduction of defect, the increase in bond length, and the proximity effect by metal can accelerate the transfer of Li+ (Na+) ion and improve the ionic conductivity, but all of them make negative influences on the stiffness of materials against the suppression of dendrite growth and weaken both critical strains and critical stress. The results provide new insight into the interaction mechanism between Li+ (Na+) ions and PF materials at the atomic level and shed light onto exploring a variety of layered PF materials in metal anode battery systems.
"A half-wave rectified alternating current electrochemical method for uranium extraction from seawater" — Chong Liu: Po-Chun Hsu, Jin Xie, Jie Zhao, Tong Wu, Haotian Wang, Wei Liu, Jinsong Zhang, Steven Chu and Yi Cui; Nature Energy, 02/17/17.
In total there is hundreds of times more uranium in sea water than on land, but extracting it for use in nuclear power generation is challenging due to its low concentration (∼3 ppb) and the high salinity background. Current approaches based on sorbent materials are limited due to their surface-based physicochemical adsorption nature. Here we use a half-wave rectified alternating current electrochemical (HW-ACE) method for uranium extraction from sea water based on an amidoximefunctionalized carbon electrode. The amidoxime functionalization enables surface specific binding to uranyl ions, while the electric field can migrate the ions to the electrode and induce electrodeposition of uranium compounds, forming charge-neutral species. Extraction is not limited by the electrode surface area, and the alternating manner of the applied voltage prevents unwanted cations from blocking the active sites and avoids water splitting. The HW-ACE method achieved a ninefold higher uranium extraction capacity (1,932 mg g−1 ) without saturation and fourfold faster kinetics than conventional physicochemical methods using uranium-spiked sea water
"Ubiquitous strong electron–phonon coupling at the interface of FeSe/SrTiO3" — Chaofan Zhang: Zhongkai Liu, Zhuoyu Chen, Yanwu Xie, Ruihua He, Shujie Tang, Junfeng He, Wei Li, Tao Jia, Slavko N. Rebec, Eric Yue Ma, Hao Yan, Makoto Hashimoto, Donghui Lu, Sung-Kwan Mo, Yasuyuki Hikita, Robert G. Moore, Harold Y. Hwang, Dunghai Lee & Zhixun Shen; Nature Communications, 02/10/17.
The observation of replica bands in single-unit-cell FeSe on SrTiO3(STO)(001) by angle-resolved photoemission spectroscopy (ARPES) has led to the conjecture that the coupling between FeSe electrons and the STO phonons are responsible for the enhancement of Tc over other FeSe-based superconductors. However the recent observation of a similar superconducting gap in single-unit-cell FeSe/STO(110) raised the question of whether a similar mechanism applies. Here we report the ARPES study of the electronic structure of FeSe/STO(110). Similar to the results in FeSe/STO(001), clear replica bands are observed. We also present a comparative study of STO(001) and STO(110) bare surfaces, and observe similar replica bands separated by approximately the same energy, indicating this coupling is a generic feature of the STO surfaces and interfaces. Our findings suggest that the large superconducting gaps observed in FeSe films grown on different STO surface terminations are likely enhanced by a common mechanism.
"Coexistence of Replica Bands and Superconductivity in FeSe Monolayer Films" — S. N. Rebec: T. Jia, C. Zhang, M. Hashimoto, D.-H. Lu, R. G. Moore, and Z.-X. Shen; Physical Review Letters, 02/10/17.
To elucidate the mechanisms behind the enhanced Tc in monolayer (1 ML) FeSe on SrTiO3 (STO), we grew highly strained 1 ML FeSe on the rectangular (100) face of rutile TiO2, and observed the coexistence of replica bands and superconductivity with a Tc of 63 K. From the similar Tc between this system and 1ML FeSe on STO (001), we conclude that strain and dielectric constant are likely unimportant to the enhanced Tc in these systems. A systematic comparison of 1 ML FeSe on TiO2 with other systems in the FeSe family shows that while charge transfer alone can enhance Tc, it is only with the addition of interfacial electron-phonon coupling that Tc can be increased to the level seen in 1 ML FeSe on STO.
"Magnetism and local symmetry breaking in a Mott insulator with strong spin orbit interactions" — L. Lu: M. Song, W. Liu, A. P. Reyes, P. Kuhns, H. O. Lee, I. R. Fisher & V. F. Mitrović; Nature Communications, 02/09/17.
Study of the combined effects of strong electronic correlations with spin-orbit coupling (SOC) represents a central issue in quantum materials research. Predicting emergent properties represents a huge theoretical problem since the presence of SOC implies that the spin is not a good quantum number. Existing theories propose the emergence of a multitude of exotic quantum phases, distinguishable by either local point symmetry breaking or local spin expectation values, even in materials with simple cubic crystal structure such as Ba2NaOsO6. Experimental tests of these theories by local probes are highly sought for. Our local measurements designed to concurrently probe spin and orbital/lattice degrees of freedom of Ba2NaOsO6 provide such tests. Here we show that a canted ferromagnetic phase which is preceded by local point symmetry breaking is stabilized at low temperatures, as predicted by quantum theories involving multipolar spin interactions.
"Core–Shell Nanoparticle Coating as an Interfacial Layer for Dendrite-Free Lithium Metal Anodes" — Wei Liu: Weiyang Li, Denys Zhuo, Guangyuan Zheng, Zhenda Lu, Kai Liu, and Yi Cui; ACS Central Science, 02/08/17.
Lithium metal based batteries represent a major challenge and opportunity in enabling a variety of devices requiring high-energy-density storage. However, dendritic lithium growth has limited the practical application of lithium metal anodes. Here we report a nanoporous, flexible and electrochemically stable coating of silica@poly(methyl methacrylate) (SiO2@ PMMA) core−shell nanospheres as an interfacial layer on lithium metal anode. This interfacial layer is capable of inhibiting Li dendrite growth while sustaining ionic flux through it, which is attributed to the nanoscaled pores formed among the nanospheres. Enhanced Coulombic efficiencies during lithium charge/ discharge cycles have been achieved at various current densities and areal capacities.
"Strong ferromagnetic exchange interaction under ambient pressure in BaFe2S3" — Meng Wang: S. J. Jin, Ming Yi, Yu Song, H. C. Jiang, W. L. Zhang, H. L. Sun, H. Q. Luo, A. D. Christianson, E. Bourret-Courchesne, D. H. Lee, Dao-Xin Yao, and R. J. Birgeneau; Phys. Rev. B, 02/03/17.
Inelastic neutron scattering measurements have been performed to investigate the spin waves of the quasione-dimensional antiferromagnetic ladder compound BaFe2S3, where a superconducting transition was observed under pressure [H. Takahashi et al., Nat. Mater. 14, 1008 (2015); T. Yamauchi et al., Phys. Rev. Lett. 115, 246402 (2015)]. By fitting the spherically averaged experimental data collected on a powder sample to a Heisenberg Hamiltonian, we find that the one-dimensional antiferromagnetic ladder exhibits a strong nearest-neighbor ferromagnetic exchange interaction (SJR = −71 ± 4 meV) along the rung direction, an antiferromagnetic SJL = 49 ± 3 meV along the leg direction, and a ferromagnetic SJ2 = −15 ± 2 meV along the diagonal direction. Our data demonstrate that the antiferromagnetic spin excitations are a common characteristic for the iron-based superconductors, while specific relative values for the exchange interactions do not appear to be unique for the parent states of the superconducting materials.
"Sulﬁphilic Nickel Phosphosulﬁde Enabled Li2S Impregnation in 3D Graphene Cages for Li–S Batteries" — Guangmin Zhou: Jie Sun, Yang Jin, Wei Chen, Chenxi Zu, Rufan Zhang, Yongcai Qiu, Jie Zhao, Denys Zhuo, Yayuan Liu, Xinyong Tao, Wei Liu, Kai Yan, Hye Ryoung Lee, and Yi Cui; Advanced Materials, 01/30/17.
A 3D graphene cage with a thin layer of electrodeposited nickel phosphosulfide for Li2S impregnation, using ternary nickel phosphosulphide as a highly conductive coating layer for stabilized polysulfide chemistry, is accomplished by the combination of theoretical and experimental studies. The 3D interconnected graphene cage structure leads to high capacity, good rate capability and excellent cycling stability in a Li2S cathode.
"Modular soft x-ray spectrometer for applications in energy sciences and quantum materials" — Yi-De Chuang: Yu-Cheng Shao, Alejandro Cruz, Kelly Hanzel, Adam Brown, Alex Frano, Ruimin Qiao, Brian Smith, Edward Domning, Shih-Wen Huang, L. Andrew Wray, Wei-Sheng Lee, Zhi-Xun Shen, Thomas P. Devereaux, Jaw-Wern Chiou, Way-Faung Pong, Valeriy V. Yashchuk, Eric Gullikson, Ruben Reininger, Wanli Yang, Jinghua Guo, Robert Duarte, and Zahid Hussain; Review of Scientific Instruments, 01/27/17.
Over the past decade, the advances in grating-based soft X-ray spectrometers have revolutionized the soft X-ray spectroscopies in materials research. However, these novel spectrometers are mostly dedicated designs, which cannot be easily adopted for applications with diverging demands. Here we present a versatile spectrometer design concept based on the Hettrick-Underwood optical scheme that uses modular mechanical components. The spectrometer’s optics chamber can be used with gratings operated in either inside or outside orders, and the detector assembly can be reconfigured accordingly. The spectrometer can be designed to have high spectral resolution, exceeding 10 000 resolving power when using small source (∼1 µm) and detector pixels (∼5 µm) with high line density gratings (∼3000 lines/mm), or high throughput at moderate resolution. We report two such spectrometers with slightly different design goals and optical parameters in this paper. We show that the spectrometer with high throughput and large energy window is particularly useful for studying the sustainable energy materials. We demonstrate that the extensive resonant inelastic X-ray scattering (RIXS) map of battery cathode material LiNi1/3Co1/3Mn1/3O2 can be produced in few hours using such a spectrometer. Unlike analyzing only a handful of RIXS spectra taken at selected excitation photon energies across the elemental absorption edges to determine various spectral features like the localized dd excitations and non-resonant fluorescence emissions, these features can be easily identified in the RIXS maps. Studying such RIXS maps could reveal novel transition metal redox in battery compounds that are sometimes hard to be unambiguously identified in X-ray absorption and emission spectra. We propose that this modular spectrometer design can serve as the platform for further customization to meet specific scientific demands.