Amorphous oxide and oxynitride lithium electrolyte thin films were synthesized by r.f. magnetron sputtering of lithium silicates and lithium phosphates in Ar, Ar + O2, Ar + N2, or N2. The composition, structure, and electrical properties of the films were characterized using ion and electron beam, X-ray, optical, photoelectron, and a.c. impedance techniques. For the lithium phosphosilicate films, lithium ion conductivities as high as 1.4 × 10−6 S/cm at 25 °C were observed, but none of these films selected for extended testing were stable in contact with lithium. On the other hand, a new thin-film lithium phosphorus oxynitride electrolyte, synthesized by sputtering Li3PO4 in pure N2, was found to have a conductivity of 2 × 10-6 S/cm at 25 °C and excellent long-term stability in contact with lithium. Thin-films cells consisting of a 1 μm thick amorphous V2O5 cathode, a 1 μm thick oxynitride electrolyte film, and a 5 μm thick lithium anode were cycled between 3.7 and 1.5 V using discharge rates of up to 100 μA/cm2 and charge rates of up to 20 μA/cm2. The open-circuit voltage of 3.6 to 3.7 V of fully-charged cells remained virtually unchanged after months of storage.

Fabrication and characterization of amorphous lithium electrolyte thin films and rechargeable thin-film batteries

Lithium–sulfur batteries (Li–S) have become a viable alternative to future energy storage devices. The electrochemical reaction based on lithium and sulfur promises an extraordinary theoretical energy density, which is far higher than current commercialized Li-ion batteries. However, the principal disadvantage impeding the success of Li–S batteries lies in the severe leakage and migration of soluble lithium polysulfide intermediates out of cathodes upon cycling. The loss of active sulfur species incurs significant capacity decay and poor battery lifespans. Considerable efforts have been devoted to developing various sulfur host materials that can effectively anchor lithium polysulfides. Herein, a comprehensive review is presented of recent advances in sulfur host materials. On the basis of the electrochemistry of Li–S batteries, the strategies for anchoring polysulfides are systematically categorized into physical confinement and chemical bonding. The structural merits of various sulfur host materials are highlighted, and the interaction mechanisms with sulfur species are discussed in detail, which provides valuable insights into the rational design and engineering of advanced sulfur host materials facilitating the commercialization of Li–S batteries. Future challenges and promising research prospects for sulfur host materials are proposed at the end of the review.

Host Materials Anchoring Polysulfides in Li–S Batteries Reviewed

Review on comprehending and enhancing the initial Coulombic efficiency of anode materials in lithium-ion/sodium-ion batteries

As we all know, environmental protection and sustainable energy utilization are significant challenges for us. Due to their many excellent characteristics, carbon materials have been playing a very important role in energy and environmental applications. Biomass is the only renewable carbon source and crucial precursor of carbonaceous materials and has the advantages of a unique structure, a wide range of sources, biodegradability, and low cost. Developing high-performance carbonaceous materials from biomass is a significant research subject. Biomass-derived porous graphitic carbon materials (BPGCs) have received extensive attention as novel high-performance sustainable carbon materials owing to its well-developed porous structure, good graphitic structure, and heteroatom doping. Here, this review firstly focuses on the principal synthesis methodologies of BPGCs. Next, three electrochemical energy storage and conversion systems that utilize BPGCs are intensively investigated, including supercapacitors (SCs), lithium-ion batteries (LIBs) and fuel cells (FCs). Then, BPGCs are further reviewed in terms of their application in the field of environmental protection, which is also the first systematic summary of BPGCs in environmental applications. Finally, this review points out the direction that is worthy of further research in the future and the essential issues that have not yet been resolved.

Biomass-derived porous graphitic carbon materials for energy and environmental applications

Lithium–sulfur batteries (Li–S) have attracted considerable attention because of their high theoretical energy density (2600 W h kg−1). However, practical commercial applications of Li–S batteries are limited by the low conductivity of sulfur and discharge products, severe polysulfide shuttling effect, and large sulfur volume expansion during discharge. Various nanostructured carbon materials have been used as sulfur host materials to overcome these problems. Carbon nanotubes (CNTs) are superior to other nanostructured carbon materials because of their unique 1D nanostructure, good conductivity, excellent flexibility, and stable chemical properties. This article reviews the application of CNT-based materials, including simple CNT materials and CNT-based nanocomposites, in Li–S batteries and the particular roles of CNTs in this system. First, general information about the function of CNTs in Li–S batteries and the preparation method of CNT/sulfur composite is provided. Second, various simple CNTs are described, and their inherent characteristics are discussed. Third, CNT-based nanocomposites, including carbon material@CNTs, chemisorption host material@CNTs, and nanocomposites based on in situ formed CNTs, are summarized. The synergistic effect of components and the function of CNTs in the composite are discussed specifically. Fourth, further treatments for CNT/S nanocomposites to better control the diffusion of polysulfides are summarized. Finally, future directions and prospects are discussed.

Carbon nanotube-based materials for lithium–sulfur batteries

Lithium-ion batteries (LIBs) continue to draw vast attention as a promising energy storage technology due to their high energy density, low self-discharge property, nearly zero-memory effect, high open circuit voltage, and long lifespan. In particular, high-energy density lithium-ion batteries are considered as the ideal power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs) in the automotive industry, in recent years. This review discusses key aspects of the present and the future battery technologies on the basis of the working electrode. We then discuss how lithium-ion batteries evolve to meet the growing demand on high charge capacity and electrode stability. An account of a stand-alone energy device (off-grid system) that combines an energy harvesting technology with a lithium-ion battery is also provided. The main discussion is categorized into three perspectives such as the evolution from the conventional to the advanced LIBs (e.g., Li-rich transition metal oxide and Ni-rich transition metal oxide batteries), to the state-of-the-art LIBs (e.g., Li–air, Li–sulfur batteries, organic electrode batteries, solid-state batteries, and Li–CO2 batteries), and to the hybridized LIBs (e.g., metal halide perovskite batteries).

Lithium-ion batteries: outlook on present, future, and hybridized technologies

Phase transition induced recrystallization and low surface potential barrier leading to 10.91%-efficient CsPbBr3 perovskite solar cells

Materials with the formula Fe2–xYxMo3O12 (x = 0.2, 0.4, 0.5, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, and 1.8) have been synthesized, and their structures, phase transitions, hygroscopicity, and thermal expansion properties have been studied by Raman spectroscopy, X-ray diffraction, and differential scanning calorimetry. It is found that Fe2–xYxMo3O12 crystallize in a single monoclinic for x ≤ 0.4 and a single orthorhombic structure for x ≥ 0.5. The monoclinic-to-orthorhombic phase transition temperature can be effectively decreased by increasing the contents of Y3+ so that Fe1.5Y0.5Mo3O12 crystallizes already in orthorhombic at room temperature and keeps this structure till very low temperatures (lower than 103 K). Two kinds of water species are found to present in Fe2–xYxMo3O12, one having little influence on the motions of the polyhedra, whereas another interacting strongly with the polyhedra and even causing a cell volume to contract. The amount of crystal water decreases with reducing the content of Y3+ so that...

Structures, Phase Transition, and Crystal Water of Fe2–xYxMo3O12

Lead-free double perovskite materials have attracted much interest for optoelectronic applications due to their nontoxicity and high stability. In this work, centimetre-sized Cs2AgBiBr6 single crystals were successfully grown using methylammonium bromide (MABr) as the flux by a top-seeded solution growth (TSSG) method. The low-temperature crystal structure of Cs2AgBiBr6 single crystals was determined and refined. To investigate the interface problems between Cs2AgBiBr6 single crystals and electrodes, the optical band gap, X-ray photoelectron spectroscopy (XPS), and ultraviolet photoemission spectroscopy (UPS) measurements were performed on Cs2AgBiBr6 single crystals. More importantly, we investigated the photodetectors based on Cs2AgBiBr6 single crystals with different contact electrodes (Au, Ag, and Al). It is found that a good Ohmic contact with Ag electrodes enables excellent photo-response behaviors. Furthermore, we studied the photodetectors based on Cs2AgBiBr6 single crystals using Ag electrodes under room and low temperature conditions, which underwent phase transition. Cs2AgBiBr6 single crystal photodetectors show clear differences at room and low temperatures, which is caused by the work function changes of Cs2AgBiBr6 single crystals induced by the reversible phase transition. These attractive properties may enable opportunities to apply emerging double perovskite single-crystalline materials for high-performance optoelectronic devices.

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Wentao Song

Papers

Lithium-ion batteries: outlook on present, future, and hybridized technologies

Phase transition induced recrystallization and low surface potential barrier leading to 10.91%-efficient CsPbBr3 perovskite solar cells

Structures, Phase Transition, and Crystal Water of Fe2–xYxMo3O12

Interface engineering strategies towards Cs2AgBiBr6 single-crystalline photodetectors with good Ohmic contact behaviours

High Efficient Hole Extraction and Stable All‐Bromide Inorganic Perovskite Solar Cells via Derivative‐Phase Gradient Bandgap Architecture