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Composites consisting of graphene nanosheets (GNSs) decorated with amorphous TiO 2 thin films were synthesized by an atomic layer deposition (ALD) technique. It was revealed that the TiO 2 thin films were uniformly deposited onto the worm-like GNSs. When used as anode materials in lithium ion batteries (LIBs), the TiO 2 –GNS composites deliver a stable capacity of ~ 140 mAh g − 1 after 100 cycles at a specific current of 100 mA g − 1 as well as superior rate capability, accounting for a sustainable 95 mAh g − 1 capacity at a specific current of 1200 mA g − 1 . It is believed that the remarkable electrochemical performance lied in the unique features of the composites, i.e., the amorphous nature of the TiO 2 films and the large surface area of GNSs. The former rendered short Li + diffusion pathways in TiO 2 thin film, while the latter offered excellent electronic conductivity as well as a large intimate contact area between the electrolyte and TiO 2 . This work laid a venue for designing new electrodes for high-performance LIBs. [ABSTRACT FROM AUTHOR]

The electrochemical reaction kinetics of the porous core–shell structured Ni/NiO anode for Li ion battery application is systematically investigated by monitoring the electrochemical impedance evolution for the first time. The electrochemical impedance under prescribed condition is measured by using impedance spectroscopy in equilibrium conditions at various depths of discharge (DOD) during charge–discharge cycles. The Nyquist plots of the binder-free porous Ni/NiO electrode are interpreted with a selective equivalent circuit composed of solution resistance, solid electrolyte interphase (SEI) film, charge transfer and solid state diffusion. The impedance analysis shows that the change of charge transfer resistance is the main contribution to the total resistance change during discharge, and the surface configuration of the obtained electrode may experience significant change during the first two cycles. Meanwhile, the increase of internal resistance reduced the utilization efficiency of the active material may be another convincing factor to increase the irreversible capacity. In addition, the impedance evolution of the as-prepared electrode during charge–discharge cycles reveals that the slow growth of the SEI film is responsible for the capacity fading after long term cycling. As a result, several strategies are summarized to optimize the electrochemical performances of transition metal oxide anodes for lithium ion batteries. [ABSTRACT FROM AUTHOR]

A sol–gel method was employed to synthesize LiMn 2 O 4 cathode for lithium ion batteries. Calcination treatment with citric acid results in the reduction of external active materials of the cathode, finally a novel layer coating of MnO was proposed on the surface of LiMn 2 O 4 . The structures and morphologies of the as-prepared samples were characterized by XRD, Raman, SEM and HRTEM techniques. It was found that the reaction between LiMn 2 O 4 and citric acid derived carbon occurred during coating process, and the resultant layer was verified to be MnO uniformly coated onto the cathode. Electrochemical performances show that the amount of coating exhibits a significant effect on LiMn 2 O 4 performance, and the optimized MnO coating could exhibit improved battery performance of the LiMn 2 O 4 cathode. The obtained improvement is attributed to decreased Mn dissolution into electrolyte upon cycling resulting from the MnO coating. [ABSTRACT FROM AUTHOR]

A rutile and anatase mixed crystal phase of nano-rod TiO 2 and TiO 2 –reduced graphene oxide (TiO 2 –RGO) nanocomposites with small particle size were prepared via a facile hydrothermal approach with titanium tetrabutoxide and graphene oxide as the precursor. Hydrolysis of titanium tetrabutoxide and mild reduction of graphene oxide were simultaneously carried out. Compared with traditional multistep methods, a novel green synthetic route to produce TiO 2 –RGO without toxic solvents or reducing agents was employed. TiO 2 –RGO as anode of lithium ion batteries was characterized by extensive measurements. The nanocomposites exhibited notable improvement in lithium ion insertion/extraction behavior compared with TiO 2 , indicating an initial irreversible capacity and a reversible capacity of 295.4 and 112.3 mA h g −1 for TiO 2 –RGO after 100 cycles at a high charge rate of 10 C. The enhanced electrochemical performance is attributed to increased conductivity in presence of reduced graphene oxide in TiO 2 –RGO, a rutile and anatase mixed crystal phase of nano-rod TiO 2 /GNS composites, small size of TiO 2 particles in nanocomposites, and enlarged electrode–electrolyte contact area, leading to more electroactive sites in TiO 2 –RGO. [ABSTRACT FROM AUTHOR]

Solid‐state electrolytes (SEs) with high anodic (oxidation) stability are essential for achieving all‐solid‐state Li‐ion batteries (ASSLIBs) operating at high voltages. Until now, halide‐based SEs have been one of the most promising candidates due to their compatibility with cathodes and high ionic conductivity. However, the developed chloride and bromide SEs still show limited electrochemical stability that is inadequate for ultrahigh voltage operations. Herein, this challenge is addressed by designing a dual‐halogen Li‐ion conductor: Li3InCl4.8F1.2. F is demonstrated to selectively occupy a specific lattice site in a solid superionic conductor (Li3InCl6) to form a new dual‐halogen solid electrolyte (DHSE). With the incorporation of F, the Li3InCl4.8F1.2 DHSE becomes dense and maintains a room‐temperature ionic conductivity over 10−4 S cm−1. Moreover, the Li3InCl4.8F1.2 DHSE exhibits a practical anodic limit over 6 V (vs Li/Li+), which can enable high‐voltage ASSLIBs with decent cycling. Spectroscopic, computational, and electrochemical characterizations are combined to identify a rich F‐containing passivating cathode‐electrolyte interface (CEI) generated in situ, thus expanding the electrochemical window of Li3InCl4.8F1.2 DHSE and preventing the detrimental interfacial reactions at the cathode. This work provides a new design strategy for the fast Li‐ion conductors with high oxidation stability and shows great potential to high‐voltage ASSLIBs. [ABSTRACT FROM AUTHOR]

A competitive complexation strategy has been developed to construct a novel electrocatalyst with Zn‐Co atomic pairs coordinated on N doped carbon support (Zn/CoN‐C). Such architecture offers enhanced binding ability of O2, significantly elongates the O−O length (from 1.23 Å to 1.42 Å), and thus facilitates the cleavage of O−O bond, showing a theoretical overpotential of 0.335 V during ORR process. As a result, the Zn/CoN‐C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions with a half‐wave potential of 0.861 and 0.796 V respectively. The in situ XANES analysis suggests Co as the active center during the ORR. The assembled zinc–air battery with Zn/CoN‐C as cathode catalyst presents a maximum power density of 230 mW cm−2 along with excellent operation durability. The excellent catalytic activity in acid is also verified by H2/O2 fuel cell tests (peak power density of 705 mW cm−2). Discrete zinc/cobalt bimetallic sites were supported on N‐doped carbon (Zn/CoN‐C) through a competitive complexation stretegy. The as‐prepared Zn/CoN‐C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions, and the assembled Zn–air batteries and H2/O2 fuel cell show excellent power density and stability, which demonstrate suitability for practical applications. [ABSTRACT FROM AUTHOR]

A competitive complexation strategy has been developed to construct a novel electrocatalyst with Zn‐Co atomic pairs coordinated on N doped carbon support (Zn/CoN‐C). Such architecture offers enhanced binding ability of O2, significantly elongates the O−O length (from 1.23 Å to 1.42 Å), and thus facilitates the cleavage of O−O bond, showing a theoretical overpotential of 0.335 V during ORR process. As a result, the Zn/CoN‐C catalyst exhibits outstanding ORR performance in both alkaline and acid conditions with a half‐wave potential of 0.861 and 0.796 V respectively. The in situ XANES analysis suggests Co as the active center during the ORR. The assembled zinc–air battery with Zn/CoN‐C as cathode catalyst presents a maximum power density of 230 mW cm−2 along with excellent operation durability. The excellent catalytic activity in acid is also verified by H2/O2 fuel cell tests (peak power density of 705 mW cm−2). [ABSTRACT FROM AUTHOR]

The hierarchical V 2 O 5 nanofibers cathode materials with diameter of 200–400 nm are successfully synthesized via an electrospinning followed by annealing. Powder X-ray diffraction (XRD) pattern confirms the formation of phase-pure product. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) obviously display the hierarchical porous nanofibers constructed by attached tiny vanadium oxide nanoplates. Electrochemical behavior of the as-prepared product is systematically studied using galvanostatic charge/discharge testing, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). It turns out that in comparison to the commercial V 2 O 5 and other unique nanostructured materials in the literature, our V 2 O 5 nanofibers show much enhanced lithium storage capacity, improved cyclic stability, and higher rate capability. After 100 cycles at a current density of 800 mA g −1 , the specific capacity of the V 2 O 5 nanofibers retain 133.9 mAh g −1 , corresponding to high capacity retention of 96.05%. More importantly, the EIS at various discharge depths clearly reveal the kinetics process of the V 2 O 5 cathode reaction with lithium. Based on our results, the possible approach to improve the specific capacity and rate capability of the V 2 O 5 cathode material is proposed. It is expected that this study could accelerate the development of V 2 O 5 cathode in rechargeable lithium ion batteries. [ABSTRACT FROM AUTHOR]