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Highly ordered mesoporous antimony-doped tin oxide (ATO) materials, containing different amount of antimony in the range of 0-50mol%, are prepared via a nanoreplication method using a mesoporous silica template. The mesoporous ATO materials thus obtained exhibit high electrical conductivity, high reversible capacity, superior cycle stability and good rate capability as anode materials for lithium-ion batteries, compared to those of pure mesoporous tin oxide. Amongst the ATO materials in this work, the mesoporous ATO material with 10mol% of antimony has highest discharge capacity of 1940mAhg-1 (charge capacity of 1049) at the 1st cycle, best cycle performance (716mAhg-1 at 100th cycle) and excellent rate capability, which are probably due to the enhanced electrical conductivity as well as reduced crystalline size. Ordered mesoporous antimony-doped tin oxide (ATO) materials with Ia3d mesostructure were obtained using nanoreplication method. The electrical conductivity of meso-ATO-10 is drastically enhanced, compared to that of meso-ATO-0. Moreover, the Sb-doping results in the high capacity retention (67% at 100th cycle) as well as excellent rate capability. We believe that the Sb-doping reduces the possibility of aggregation of the metallic tin toward larger crystals and accommodates the electrochemically induced volume change during Li alloying-dealloying process. [ABSTRACT FROM AUTHOR]

In order to develop high energy density Li rechargeable batteries, nano-sized materials have attracted attention as the active materials. Mesoporous materials consist of the micrometre-sized particles, and they have high surface area due to their mesopore and thin wall thickness of framework. Here, we synthesize a highly ordered mesoporous RuO 2 to investigate the effect that the mesoscopic structure has on the capacity and their corresponding reaction mechanism of Li rechargeable battery. The synthesized mesoporous RuO 2 shows an initial discharge capacity of 1366 mAh g −1 on mesoporous RuO 2 , which is higher than that of commercial RuO 2 . Our findings via In situ X-ray analysis techniques combined with electrochemical analysis demonstrate that the additional capacity of mesoporous RuO 2 is resulted from the enhanced interfacial reaction between Ru metal and Li 2 O formed by conversion reaction of RuO 2 . Nano-size effects of mesoporous structure such as high surface area, easy electron transport, and small domain would enable to improve the interfacial reaction of highly ordered mesoporous RuO 2 . The understanding of this relationship between structural engineering and electrochemical properties provides the insight into development of high energy density anode materials in next generation Li rechargeable battery. [ABSTRACT FROM AUTHOR]

Optimized porous structure is a prerequisite for high performance Li‒O 2 battery cathode. Macroporous-mesoporous carbon (MMC) is fabricated via a nano-replication method using mesoporous SiO 2 (KIT-6) containing NiO as the template. By varying the amount of NiO in the KIT-6/NiO composite template, the amount of macropores inside MMC is easily controlled. The as-prepared MMC exhibits a highly porous structure with abundant ordered mesopores along with macropores that are larger than 200 nm in size. When the MMC is applied as the cathode material in a Li‒O 2 battery, the cell exhibits greatly improved electrochemical performance in comparison to a cell using conventional ordered mesoporous carbon (OMC) without macropores. Systematic studies indicate that while mesopores in the OMC are clogged with Li 2 O 2 formed during the early stage of discharge, the MMC sufficiently accommodates a large amount of Li 2 O 2 in the pores. In addition, Li 2 O 2 with poor crystallinity forms on the cathode containing MMC during subsequent discharge processes, which can be due to the accumulated side product and the limited size of pores. The formation of amorphous Li 2 O 2 and the expedited mass transport through the interconnected meso- and macropores of MMC can attribute to the improved electrochemical performance of the MMC cathode material. [ABSTRACT FROM AUTHOR]

We developed highly promising solid polymer electrolytes (SPEs) based on a novel cross-linker containing star-shaped phosphazene with poly(ethylene oxide) (PEO) branches with very high ionic conductivity (7.6 × 10 −4 S cm −1 ), improved mechanical stability, and good electrochemical stability for all-solid-state lithium batteries. In particular, allyl groups were introduced at the ends of the cross-linker in order to overcome the easy self-polymerization of existing cross-linking acrylate end groups. A novel semi-interpenetrating network (semi-IPN) SPE was prepared by in-situ radical polymerization of a precursor solution containing lithium salt, poly(ethylene glycol) dimethyl ether as a plasticizer, and a mixture of pentaerythritol tetrakis(3-mercaptopropionate) and a synthesized hexakis(allyloxy)cyclotriphosphazene ( thiol-ene PAL) as the cross-linker. Batteries employing LiFePO 4 as the cathode, lithium foil as the anode, and the SPE thin film as the electrolyte were assembled and tested. At ambient temperature, the initial discharge capacity was 147 mAh/g at 0.1 °C and 132 mAh/g at 0.5 °C, and 97% of the capacity was retained at the 100th cycle. All-solid-state pouch-package lithium cells assembled with the SPEs exhibited stable electrochemical performance, even under a severely wrinkled state. These outstanding properties of SPEs based on thiol-ene PAL demonstrate feasibility for practical battery applications with improved reliability and safety. [ABSTRACT FROM AUTHOR]

Three dimensional (3D) porous self-assembled MoO 2 /graphene microspheres are successfully synthesized via microwave-assisted hydrothermal process in a short reaction time followed by thermal annealing. Such rationally designed multifunctional hybrid nanostructure is constructed from interconnected MoO 2 nanoparticles (3–5 nm), which is self-assembled into ordered nanoporous microspheres via strong electrostatic attraction between graphene sheets and MoO 2 nanoparticles. The MoO 2 /graphene hybrid structure delivers a high reversible capacity with significantly enhanced cycling stability (∼1300 mAh g −1 after 80 cycles at C/10 rate) and excellent rate capability (913 and 390 mAh g −1 at 2C and 5C rates, respectively), when used as an anode material. The microspheres are interconnected and well encapsulated by the flexible graphene sheets, which not only accommodates large volume change but also increases the electrical conductivity of the hybrid structure. Moreover, nanoporous voids present in the 3D framework facilitate effective electrolyte penetration and make a direct contact with the active MoO 2 nanoparticles, thereby greatly enhancing lithium ion transport. The strategic combination of self-assembly, nanoporous voids, 3D network and intriguing properties of graphene sheets provides excellent electrochemical performance as anode materials for Lithium ion battery applications. [ABSTRACT FROM AUTHOR]

Transition metal oxides have been intensively developed for use as anode materials to overcome the capacity limitations of commercial graphite. In this study, a highly ordered mesoporous NiO electrode material is fabricated using a hard templating method, and exhibits a reversible capacity of approximately 940 mAh g−1 that is much higher than the theoretical value based on the conversion reaction (717 mAh g−1). Combined analyses that include synchrotron-based X-ray techniques and controlled X-ray photoelectron spectroscopies attribute the lithium storage behaviors to both the conversion reaction of NiO framework and the reversible electrolyte-derived surface layer. Interestingly, the contribution of the reversible electrolyte-derived surface layer (∼440 mAh g−1) to the capacity is comparable to that of the conversion reaction with NiO (∼500 mAh g−1). The results also demonstrate that incomplete conversion occurs due to the high bonding energy of Ni–O in the framework during the electrochemical reaction, and prove that the distinctive nano-structural characteristics of the mesoporous NiO surface cause the reversible behavior of the electrolyte-derived surface layer. [Display omitted] • Ordered mesoporous NiO has an abnormally high electrochemical capacity. • The abnormal high capacity is due to the electrolyte-derived surface layer. • The conversion reaction of NiO is partially irreversible during cycling. [ABSTRACT FROM AUTHOR]

The continuous activation of electrolyte-derived surface layer contributes the abnormal high specific capacity and capacity increase of ordered mesoporous Co 3 O 4 anode material. [Display omitted] • The anomalous electrochemical phenomenon of ordered mesoporous Co 3 O 4 anode material. • The reversible conversion reaction for mesoporous Co 3 O 4 by low bond strength. • The significance of mesoporous structure on the electrolyte-derived surface layer. Nanostructured engineering is one of the strategies for optimizing transition metal oxides as anode materials in lithium-ion batteries. Among them, mesoporous structures have received significant attention due to their intrinsic properties which are related to porous structure. This structure provides short Li-ion diffusion pathways and acts as a buffer for volume changes during electrochemical reactions, affecting various electrochemical properties and performances. One of the intriguing aspects of the mesoporous structure effect is that it sometimes triggers a negative fading. Herein, we observed that ordered mesoporous Co 3 O 4 exhibits a higher reversible capacity and anomalous cycle behavior that capacity increases during cycling, known as a negative fading, compared to bulk Co 3 O 4. Moreover, the observed capacity is even higher than its theoretical capacity. Mesoporous Co 3 O 4 exhibits stable and more reversible conversion reactions, and even gradually activated electrolyte-derived surface layer formation/decomposition during cycling. Based on combined synchrotron-based X-ray analyses and electrochemical tests, we found the weaker Co-O and Co-Co bond strength in mesoporous material than those in the bulk material, gives rise to a more reversible conversion reaction during cycling. In addition, the distinctive structural properties of mesoporous leads to the further formation/decomposition of electrolyte-derived surface layer, resulting in the negative fading. [ABSTRACT FROM AUTHOR]

Nanostructured materials for lithium-ion batteries (LIBs) have many advantages over bulk electrode materials, and therefore, such materials should be effectively utilized in next-generation batteries. Herein, we identify that the superior performances of mesoporous Mn 2 O 3 results from the different lithium storage behaviors of mesoporous and bulk Mn 2 O 3. X-ray absorption spectroscopy (XAS) and bond strength calculation show that mesoporous Mn 2 O 3 has a larger capacity than bulk Mn 2 O 3 owing to an additional oxidation of Mn2+ to a higher oxidation state during charging, as well as an additional reversible reaction during cycling because the weaker Mn–O bond strength of mesoporous Mn 2 O 3 requires much less strength to break or form atomic bonds during the electrochemical reactions. Furthermore, the combined results of X-ray photoelectron spectroscopy and soft XAS indicate that an additional lithium storage reaction through the reversible formation–decomposition of the electrolyte-derived surface layer occurs more in mesoporous Mn 2 O 3 than in bulk Mn 2 O 3. Consequently, the improvement in the lithium storage behavior of mesoporous Mn 2 O 3 due to the increasing specific surface area and decreasing particle size with the progression of cycles, also affects their cycle performances. This study provides a better understanding of the synergistic relationship between nanostructures and the electrochemical performances of anode materials for LIBs. • Comparison of lithium storage behaviors between mesoporous Mn 2 O 3 and bulk Mn 2 O 3. • Weaker Mn–O bond strength of mesoporous Mn 2 O 3 causes further oxidation reaction. • Capacity due to the electrolyte-derived surface layer is larger in mesoporous Mn 2 O 3. • Structural changes after cycling affect the cycle performance of mesoporous Mn 2 O 3. [ABSTRACT FROM AUTHOR]