Jiulin Wang

Lithium (Li) metal is an ideal anode material for rechargeable batteries due to its extremely high theoretical specific capacity (3860 mA h g−1), low density (0.59 g cm−3) and the lowest negative electrochemical potential (−3.040 V vs. the standard hydrogen electrode). Unfortunately, uncontrollable dendritic Li growth and limited Coulombic efficiency during Li deposition/stripping inherent in these batteries have prevented their practical applications over the past 40 years. With the emergence of post-Li-ion batteries, safe and efficient operation of Li metal anodes has become an enabling technology which may determine the fate of several promising candidates for the next generation energy storage systems, including rechargeable Li–air batteries, Li–S batteries, and Li metal batteries which utilize intercalation compounds as cathodes. In this paper, various factors that affect the morphology and Coulombic efficiency of Li metal anodes have been analyzed. Technologies utilized to characterize the morphology of Li deposition and the results obtained by modelling of Li dendrite growth have also been reviewed. Finally, recent development and urgent need in this field are discussed.

Zinc metal is an attractive anode material for next-generation batteries. However, dendrite growth and limited Coulombic efficiency (CE) during cycling are the major roadblocks towards the widespread commercialization of batteries employing Zn anodes. In this work we report the novel adoption of triethyl phosphate (TEP) as a solvent and co-solvent with aqueous electrolytes to obtain a highly stable and dendrite-free Zn anode. Stable Zn plating/stripping for over 3000 h was obtained, accompanied by a CE of 99.68 %. SEM images of the Zn anodes revealed highly porous interconnected dendrite-free Zn deposits. The electrolyte displayed good compatibility with both Zn anodes and potassium copper hexacyanoferrate (KCuHCf) cathodes for Zn ion batteries (ZIBs). The full cell showed a long cycling stability and high rate capability. The present work is a contribution towards cost-effective and safe battery systems.

Prussian blue and its analogues have received particular attention as superior cathodes for Na-ion batteries due to their potential 2-Na storage capacity (∼170 mAh g(-1)) and low cost. However, most of the Prussian blue compounds obtained from the conventional synthetic routes contain large amounts of Fe(CN)6 vacancies and coordinated water molecules, which leads to the collapse of cyano-bridged framework and serious deterioration of their Na-storage ability. Herein, we propose a facile citrate-assisted controlled crystallization method to obtain low-defect Prussian blue lattice with greatly improved Na-storage capacity and cycling stability. As an example, the as-prepared Na2CoFe(CN)6 nanocrystals demonstrate a reversible 2-Na storage reaction with a high specific capacity of 150 mAh g(-1) and a ∼ 90% capacity retention over 200 cycles, possibly serving as a low cost and high performance cathode for Na-ion batteries. In particular, the synthetic strategy described in this work may be extended to other coordination-framework materials for a wide range of energy conversion and storage applications.

Polyacrylonitrile/graphene (PAN/GNS) composites have been synthesized via an in situ polymerization method for the first time, which serve as a precursor to prepare a cathode material for high-rate rechargeable Li–S batteries. It is observed from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the PAN nanoparticles, less than 100 nm in size, are anchored on the surface of the GNS and this unique structure is maintained in the sulfur composite cathode material. The electrochemical properties of the pyrolyzed PAN-S/GNS (pPAN-S/GNS) composite cathode have been evaluated by cyclic voltammograms, galvanostatic discharge–charge cycling and electrochemical impedance spectroscopy. The results show that the pPAN-S/GNS nanocomposite, with a GNS content of ca. 4 wt.%, exhibits a reversible capacity of ca. 1500 mA hg−1sulfur or 700 mA hg−1composite in the first cycle, corresponding to a sulfur utilization of ca. 90%. The capacity retention is relatively stable at 0.1 C. Even up to 6 C, a competitive capacity of ca. 800 mA hg−1sulfur is obtained. The superior performance of pPAN-S/GNS is attributed to the introduction of the GNS and the even composite structure. The GNS in the composite materials works as a three-dimensional (3-D) nano current collector, which could act not only as an electronically conductive matrix, but also as a framework to improve the electrochemical performance.