The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

Spinels with the formula of AB2O4 (where A and B are metal ions) and the properties of magnetism, optics, electricity, and catalysis have taken significant roles in applications of data storage, biotechnology, electronics, laser, sensor, conversion reaction, and energy storage/conversion, which largely depend on their precise structures and compositions. In this review, various spinels with controlled preparations and their applications in oxygen reduction/evolution reaction (ORR/OER) and beyond are summarized. First, the composition and structure of spinels are introduced. Then, recent advances in the preparation of spinels with solid-, solution-, and vapor-phase methods are summarized, and new methods are particularly highlighted. The physicochemical characteristics of spinels such as their compositions, structures, morphologies, defects, and substrates have been rationally regulated through various approaches. This regulation can yield spinels with improved ORR/OER catalytic activities, which can furth...

Spinels: Controlled Preparation, Oxygen Reduction/Evolution Reaction Application, and Beyond

Lithium-metal batteries (LMBs), as one of the most promising next-generation high-energy-density storage devices, are able to meet the rigid demands of new industries. However, the direct utilization of metallic lithium can induce harsh safety issues, inferior rate and cycle performance, or anode pulverization inside the cells. These drawbacks severely hinder the commercialization of LMBs. Here, an up-to-date review of the behavior of lithium ions upon deposition/dissolution, and the failure mechanisms of lithium-metal anodes is presented. It has been shown that the primary causes consist of the growth of lithium dendrites due to large polarization and a strong electric field at the vicinity of the anode, the hyperactivity of metallic lithium, and hostless infinite volume changes upon cycling. The recent advances in liquid organic electrolyte (LOE) systems through modulating the local current density, anion depletion, lithium flux, the anode-electrolyte interface, or the mechanical strength of the interlayers are highlighted. Concrete strategies including tailoring the anode structures, optimizing the electrolytes, building artificial anode-electrolyte interfaces, and functionalizing the protective interlayers are summarized in detail. Furthermore, the challenges remaining in LOE systems are outlined, and the future perspectives of introducing solid-state electrolytes to radically address safety issues are presented.

Reviving Lithium-Metal Anodes for Next-Generation High-Energy Batteries

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verifi ed by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm −2 with a high sulfur loading (4.2 mg S cm −2 ) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm −2 ) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries.

Nitrogen-Doped Mesoporous Carbon Promoted Chemical Adsorption of Sulfur and Fabrication of High-Areal-Capacity Sulfur Cathode with Exceptional Cycling Stability for Lithium-Sulfur Batteries

Reduction/Evolution Catalysts for Low-Temperature Electrochemical Devices Dengjie Chen,†,⊥,∇ Chi Chen,†,⊥ Zarah Medina Baiyee,† Zongping Shao,‡,§ and Francesco Ciucci*,†,∥ †Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China ‡State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry & Chemical Engineering, Nanjing Tech University, No. 5 Xin Mofan Road, Nanjing 210009, China Department of Chemical Engineering, Curtin University, Perth, Western Australia 6845, Australia Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China

Nonstoichiometric Oxides as Low-Cost and Highly-Efficient Oxygen Reduction/Evolution Catalysts for Low-Temperature Electrochemical Devices

Magnesium-based hydrogen storage alloys have attracted much interest because of their high hydrogen storage capacity, low weight, low material cost and easy accessibility [1]. However, their hydrides are too stable to be used at room temperatures and around atmospheric pressure. Mg–Ni mixed in some ranges using ball-milling and refined to an amorphous state exhibits high rate of H2 absorption/desorption kinetics. Ball milling the alloy (ingots prepared by arc-melting technique) in H2 is the most widely used method to refine the grains of hydrides; however it is time consuming, expensive and energyinefficient. To produce hydrogen storage alloys, especially for magnesium-based alloys hydriding combustion synthesis (HCS) was firstly proposed by Akiyama et al in 1997 [2]. HCS can yield a high active (ultrafine) product in a combined single-step synthesis of metal alloys with its hydriding, and possess the advantages like short processing time, high product purity, low energy requirement, etc. [3]. In the present research, sub-micron Mg95-Ni5 alloys have been prepared using fast, simple and costeffective hydrating combustion synthesis (HCS). Prepared alloys are characterized for their micro-structural, hydrogenation kinetics and electrochemical properties. The microcrystalline Mg and Ni were mixed in acetone using ultra-sonication treatment and dried-mixture was allowed to undergo the thermal profile in specially designed reactor. The thermal profile comprise the heating the reactor to 590°C for 1h in H2 gas at 2MPa and cooling to 400°C which is maintained for 4h. Figure 1 shows the XRD pattern of the HCS prepared and hydrided Mg-Ni alloy. Here, it can be seen that preparation of alloy and in-situ its hydrogenation is achieved in a combined step. Apart from this combined advantage the process time was only 6hrs, which is very less compared to that of conventional ball-milling duration to achieve the same effect. However, it is also observable that the prepared alloy is not completely hydrided as the XRD pattern shows the peaks corresponding to unreacted Mg. By analysing the XRD intensity of different phase peaks we obtained the phase percentages which confirm that more than 70% of initial Mg is converted to β-MgH2 phase. This reveals the slight optimization in synthesis procedure (thermal profile) is desired to achieve the complete conversion. The surface area (SA) of HCS prepared samples and precursor Mg was determined using BET. The HCS prepared MgH2-Ni alloy exhibits higher surface area (SA = 10.52m/g) than that of flat-surfaced Mg (precursor) (SA = 4.39m/g) which can be attributed to the nano-granular surface morphology of HCS prepared sample (inset of Fig.1). Inset of figure 1 shows the FE-SEM of HCS prepared sample and that of precursor Mg, which clearly indicates the presence of nano-granules (avg. grain size is ~80nm) on the surface of clusters. Figure 2 presents absorption/desorption kinetic data of HCS prepared sample for first 3 cycles at 400°C. From figure 2, it is evident that that the HCS prepared samples requires activation. During first desorption measurement, the prepared hydride powder desorbs (curve 1) the negligible amount of H2. However, subsequent desorption curves (curve 3 and 5) showed initiation of immediate desorption

http://ma.ecsdl.org/content/MA2011-02/7/359.full.pdf

Choong-Nyeon Park

Papers

Thermokinetic and Electrochemical Characteristics of Mg-Ni (95:5) Alloy Synthesized Using Hydriding Combustion

A study of the hydriding kinetics of titanium-iron and its alloys