Yutao Li

Plating a Dendrite-Free Lithium Anode with a Polymer/Ceramic/Polymer Sandwich Electrolyte

A cross-linked polymer containing pendant molecules attached to the polymer framework is shown to form flexible and low-cost membranes, to be a solid Li(+) electrolyte up to 270 °C, much higher than those based on poly(ethylene oxide), to be wetted by a metallic lithium anode, and to be not decomposed by the metallic anode if the anions of the salt are blocked by a ceramic electrolyte in a polymer/ceramic membrane/polymer sandwich electrolyte (PCPSE). In this sandwich architecture, the double-layer electric field at the Li/polymer interface is reduced due to the blocked salt anion transfer. The polymer layer adheres/wets the lithium metal surface and makes the Li-ion flux at the interface more homogeneous. This structure integrates the advantages of the ceramic and polymer. With the PCPSE, all-solid-state Li/LiFePO4 cells showed a notably high Coulombic efficiency of 99.8-100% over 640 cycles.

Optimizing Li+ conductivity in a garnet framework

The garnet-related oxides with the general formula Li7−xLa3Zr2−xTaxO12 (0 ≤ x ≤ 1) were prepared by conventional solid-state reaction. X-ray diffraction (XRD), neutron diffraction and AC impedance were used to determine phase formation and the lithium-ion conductivity. The lattice parameter of Li7−xLa3Zr2−xTaxO12 decreased linearly with increasing x. Optimum Li-ion conductivity in the Li-ion garnets Li7−xLa3Zr2−xTaxO12 is found in the range 0.4 ≤ x ≤ 0.6 for samples fired at 1140 °C in an alumina crucible. A room-temperature σLi ≈ 1.0 × 10−3 S cm−1 for x = 0.6 with an activation energy of 0.35 eV in the temperature range of 298–430 K makes this Li-ion solid electrolyte attractive for a new family of Li-ion rechargeable batteries.

A chemistry and material perspective on lithium redox flow batteries towards high-density electrical energy storage

Electrical energy storage system such as secondary batteries is the principle power source for portable electronics, electric vehicles and stationary energy storage. As an emerging battery technology, Li-redox flow batteries inherit the advantageous features of modular design of conventional redox flow batteries and high voltage and energy efficiency of Li-ion batteries, showing great promise as efficient electrical energy storage system in transportation, commercial, and residential applications. The chemistry of lithium redox flow batteries with aqueous or non-aqueous electrolyte enables widened electrochemical potential window thus may provide much greater energy density and efficiency than conventional redox flow batteries based on proton chemistry. This Review summarizes the design rationale, fundamentals and characterization of Li-redox flow batteries from a chemistry and material perspective, with particular emphasis on the new chemistries and materials. The latest advances and associated challenges/opportunities are comprehensively discussed.

Low-Cost High-Energy Potassium Cathode

Potassium has as rich an abundance as sodium in the earth, but the development of a K-ion battery is lagging behind because of the higher mass and larger ionic size of K+ than that of Li+ and Na+, which makes it difficult to identify a high-voltage and high-capacity intercalation cathode host. Here we propose a cyanoperovskite KxMnFe(CN)6 (0 ≤ x ≤ 2) as a potassium cathode: high-spin MnIII/MnII and low-spin FeIII/FeII couples have similar energies and exhibit two close plateaus centered at 3.6 V; two active K+ per formula unit enable a theoretical specific capacity of 156 mAh g-1; Mn and Fe are the two most-desired transition metals for electrodes because they are cheap and environmental friendly. As a powder prepared by an inexpensive precipitation method, the cathode delivers a specific capacity of 142 mAh g-1. The observed voltage, capacity, and its low cost make it competitive in large-scale electricity storage applications.

Hybrid Polymer/Garnet Electrolyte with a Small Interfacial Resistance for Lithium-Ion Batteries

Li7 La3 Zr2 O12 -based Li-rich garnets react with water and carbon dioxide in air to form a Li-ion insulating Li2 CO3 layer on the surface of the garnet particles, which results in a large interfacial resistance for Li-ion transfer. Here, we introduce LiF to garnet Li6.5 La3 Zr1.5 Ta0.5 O12 (LLZT) to increase the stability of the garnet electrolyte against moist air; the garnet LLZT-2 wt % LiF (LLZT-2LiF) has less Li2 CO3 on the surface and shows a small interfacial resistance with Li metal, a solid polymer electrolyte, and organic-liquid electrolytes. An all-solid-state Li/polymer/LLZT-2LiF/LiFePO4 battery has a high Coulombic efficiency and long cycle life; a Li-S cell with the LLZT-2LiF electrolyte as a separator, which blocks the polysulfide transport towards the Li-metal, also has high Coulombic efficiency and kept 93 % of its capacity after 100 cycles.

Photocatalytic CO2 Reduction by Carbon-Coated Indium-Oxide Nanobelts

Indium-oxide (In2O3) nanobelts coated by a 5-nm-thick carbon layer provide an enhanced photocatalytic reduction of CO2 to CO and CH4, yielding CO and CH4 evolution rates of 126.6 and 27.9 μmol h-1, respectively, with water as reductant and Pt as co-catalyst. The carbon coat promotes the absorption of visible light, improves the separation of photoinduced electron-hole pairs, increases the chemisorption of CO2, makes more protons from water splitting participate in CO2 reduction, and thereby facilitates the photocatalytic reduction of CO2 to CO and CH4.

A high-performance all-metallocene-based, non-aqueous redox flow battery

Here, a class of organometallic compounds, metallocenes, are explored to serve as both catholyte and anolyte redox species for non-aqueous lithium-based redox flow battery (Li-RFB) applications. The prototype of all-metallocene-based Li-RFB exploits ferrocene (FeCp2) and cobaltocene (CoCp2) as the redox-active cathode and anode, respectively. The reaction rate constants of metallocenes are determined to be as high as 10−3 cm s−1, two orders greater than most redox-active materials applied in conventional redox flow batteries. This designed Li-RFB yields a working potential of 1.7 V, and by introduction of methyl groups on the ligand rings of CoCp2, the working potential can be further increased to 2.1 V. The fabricated full cell shows capacity retention of over 99% per cycle with a coulombic efficiency (CE) of >95% and an energy efficiency of >85%. These results demonstrate a generic design route towards high performance non-aqueous RFBs via rational screening and functionalization of metallocenes.

Solvent-mediated directionally self-assembling MoS2 nanosheets into a novel worm-like structure and its application in sodium batteries

Ultralong worm-like MoS2 nanostructures were assembled with a solvent-mediated solvothermal process by controlling the composition ratio of the miscible precursors in solution. The formation mechanism of worm-like MoS2 nanostructures was proposed and the as-prepared materials as anodes in sodium ion batteries delivered a good discharge–charge capacity, superior cycling stability and excellent coulombic efficiency. This work provides an efficient and economic approach to tailor the nanostructure of layered transition metal oxides and transition-metal dichalcogenides simply by controlling the chemical composition and physical properties in a solvothermal process.

Experimental visualization of lithium conduction pathways in garnet-type Li 7La 3Zr 2O 12

The evolution of the Li-ion displacements in the 3D interstitial pathways of the cubic garnet-type Li(7)La(3)Zr(2)O(12), cubic Li(7)La(3)Zr(2)O(12), was investigated with high-temperature neutron diffraction (HTND) from RT to 600 °C; the maximum-entropy method (MEM) was applied to estimate the Li nuclear-density distribution. Temperature-driven Li displacements were observed; the displacements indicate that the conduction pathways in the garnet framework are restricted to diffusion through the tetrahedral sites of the interstitial space.

Sulfur passivation of GaAs metal-semiconductor field-effect transistor

A passivation technique consisting of a (NH4)2S dip followed by GaS deposition has been applied to a GaAs microwave-power metal–semiconductor field-effect transistor (MESFET). The breakdown characteristic of the MESFET is greatly improved upon the (NH4)2S treatment, and a stable passivation effect can be achieved by GaS film deposition. It is found that the FET current–voltage characteristics are closely related to variations in the pinning position of the GaAs surface Fermi level. With the surface passivated, a depletion layer can be properly formed and protected, which is of benefit to the control of the device parameters.