Co3O4 hollow dodecahedrons with controllable interiors are prepared through direct pyrolysis of ZIF-67 and exhibit high performance for Li-ion storage.

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Popcorn-derived porous carbon flakes have been successfully fabricated from the biomass of maize. Utilizing the "puffing effect", the nubby maize grain turned into materials with an interconnected honeycomb-like porous structure composed of carbon flakes. The following chemical activation method enabled the as-prepared products to possess optimized porous structures for electrochemical energy-storage devices, such as multilayer flake-like structures, ultrahigh specific surface area (S: 3301 m g), and a high content of micropores (microporous surface area of 95%, especially the optimized sub-nanopores with the size of 0.69 nm) that can increase the specific capacitance. The as-obtained sample displayed excellent specific capacitance of 286 F g at 90 A g for supercapacitors. Moreover, the unique porous structure demonstrated an ideal way to improve the volumetric energy density performance. A high energy density of 103 Wh kg or 53 Wh L has been obtained in the case of ionic liquid electrolyte, which is the highest among reported biomass-derived carbon materials and will satisfy the urgent requirements of a primary power source for electric vehicles. This work may prove to be a fast, green, and large-scale synthesis route by using the large nubby granular materials to synthesize applicable porous carbons in energy-storage devices.

Monodisperse sulfonated polystyrene (SPS) microspheres are employed as both the template and carbon source to prepare MoS2 quasi-hollow microspheres-encapsulated porous carbon. The synthesis procedure involves the hydrothermal growth of MoS2 ultrathin nanosheets on the surface of SPS microspheres and subsequent annealing to remove SPS core. Incomplete decomposition of SPS during annealing due to the confining effect of MoS2 shells leaves residual porous carbon in the interior. When being evaluated as the anode materials of Li-ion batteries, the as-prepared C@MoS2 microspheres exhibit excellent cycling stability (95% of capacity retained after 100 cycles) and high rate behavior (560 mAh g(-1) at 5 A g(-1)).

We report the designed synthesis of Co 1,3,5-benzenetricarboxylate coordination polymers (CPs) via a straightforward hydrothermal method, in which three kinds of reaction solvents are selected to form CPs with various morphologies and dimensions. When tested as anode materials in Li-ion battery, the cycling stabilities of the three CoBTC CPs at a current density of 100 mA g(-1) have not evident difference; however, the reversible capacities are widely divergent when the current density is increased to 2 A g(-1). The optimized product CoBTC-EtOH maintains a reversible capacity of 473 mAh g(-1) at a rate of 2 A g(-1) after 500 galvanostatic charging/discharging cycles while retaining a nearly 100% Coulombic efficiency. The hollow microspherical morphology, accessible specific area, and the absence of coordination solvent of CoBTC-EtOH might be responsible for such difference. Furthermore, the ex situ soft X-ray absorption spectroscopy studies of CoBTC-EtOH under different states-of-charge suggest that the Co ions remain in the Co(2+) state during the charging/discharging process. Therefore, Li ions are inserted to the organic moiety (including the carboxylate groups and the benzene ring) of CoBTC without the direct engagement of Co ions during electrochemical cycling.

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Monovalent Li-substitution has been proven to be an effective strategy to resolve the pivotal problems confronted with P2-type layered Mn oxides, such as cooperative Jahn–Teller distortions of Mn3+ ions and drastic P2-(OP4)-O2 phase transformations occurring during desodiation. However, the cycling stability of most Li+-substituted P2-Na x Li y Mn1–y O2 remains far from satisfactory. We herein develop a facile Ti-substitution method to improve the cyclability by taking Na0.72Li0.24Mn0.76O2 (NLMO) as an example. As expected, the novel layered oxide cathode Na0.72Li0.24Ti0.10Mn0.66O2 (NLMTO-0.1) is able to deliver a very high reversible capacity of 165 mA h g–1 for over 80 cycles within the voltage range of 1.5–4.5 V (vs Na metal), which is among the best for the reported Na-storage cathode materials. Moreover, the structure–property relationship of Ti4+ substitution is scrutinized by an arsenal of 23Na/7Li solid-state nuclear magnetic resonance, dual-mode electron paramagnetic resonance, and synchrotron X-ray diffraction techniques. The results unequivocally substantiate that Ti substitution can effectively reduce the Li+/Mn4+ ordering in TMO2 slabs, assist the reversible migration of Li+ during Na+ extraction/intercalation, and ultimately enhance the reversibility of the oxygen redox process. This work provides a comprehensive insight into the structure chemistry in developing high-capacity and high-stability layered oxide cathodes.

Superionic conductors with ionic conductivity on the order of mS cm −1 are expected to revolutionize the development of solid-state batteries (SSBs). However, currently available superionic conductors are limited to only a few structural families such as garnet oxides and sulfide-based glass/ceramic. Interfaces in composite systems such as alumina in lithium iodide have long been identified as a viable ionic conduction channel, but practical superionic conductors employing the interfacial conduction mechanism are yet to be realized. Here we report a novel method that creates continuous interfaces in the bulk of composite thin films. Ions can conduct through the interface, and consequently, the inorganic phase can be ionically insulating in this type of bulk interface superionic conductors (BISCs). Ionic conductivities of lithium, sodium, and magnesium ion BISCs have reached 1.16 mS cm −1 , 0.40 mS cm −1 , and 0.23 mS cm −1 at 25 °C in 25 μm thick films, corresponding to areal conductance as high as 464 mS cm −2 , 160 mS cm −2 , and 92 mS cm −2 , respectively. Ultralow overpotential and stable long-term cycling for up to 5000 h were obtained for solid-state Li metal symmetric batteries employing Li ion BISCs. This work opens new structural space for superionic conductors and urges for future investigations on detailed conduction mechanisms and material design principles.