cond., low charge transfer resistance and mitigates issues of vol. This superior anode performance is ascribed to the reduced size of α-MnO 2 domains that are well dispersed in an RGO matrix, which affords good ionic/elec. ![]() The anodes exhibit excellent rate capability in a wide range of rate testing from 0.2 to 10 C, without showing capacity decay. The results show that this more » composite maintains a high capacity of 615 mAh g -1 even after 200 cycles at a high current rate of 1 C (830 mA g -1), and with a high Coulombic efficiency near 99%. Here, the rationally designed Ni-α-MnO 2/RGO was tested in galvanostatic half coin cells for Li + charge-discharge studies. The synthesis approach is easy to scale up and suitable for industrial applications. In this study, a solid-state synthetic strategy is presented that successfully combines nanosize (~ 50 nm) nickel doped α-MnO 2 with reduced graphene oxides as highly stable composite anodes in lithium ion batteries. Applications of manganese oxides in secondary batteries are limited by low electrical conductivity and rapid capacity fading because of electrode pulverization and aggregation. Manganese oxides have been frequently used as cathodes in primary batteries. The understanding generated in this work provides a totally new set of guiding principles for materials engineers working to optimize hard carbon for Na-ion battery applications. Our combined first principles calculations and experimental studies revealed a new trapping mechanism, showing that the high binding energies between B-doping induced defects and Na-ions are responsible for the irreversible capacity. Furthermore, we observe that the highly defective B-doped hard carbon suffers a tremendous irreversible capacity in the first desodiation cycle. While opening the interlayer spacing through P or S doping extends the low-voltage capacity plateau, and increasing the defect concentration with P or B doping high first sodiation capacity is achieved. Specifically, P, S and B doping was used to engineer the density of local defects in graphenic layers, and to modify the spacing between the layers. more » Here, we present two key discoveries: first that characteristics of hard carbon s structure can be modified systematically by heteroatom doping, and second, that these changes greatly affect Na-ion storage properties, which reveal the mechanisms for Na storage in hard carbon. Although as an amorphous carbon, hard carbon possesses a subtle and complex structure composed of domains of layered rumpled sheets that have local order resembling graphene within each layer but complete disorder along the c-axis between layers. Holding back the development of these batteries is that a complete understanding of the mechanism of Na-ion storage in hard carbon has remained elusive. Hard carbon is the candidate anode material for the commercialization of Na-ion batteries the batteries that by virtue of being constructed from inexpensive and abundant components open the door for massive scale up of battery-based storage of electrical energy. Such excellent cycle performance, high reversible capacity, and good rate capability enabled this hard carbon to be a promising candidate as anode material for Na-ion battery application. In addition, the more » hard carbon originated from the PVC nanofibers exhibited good cycling stability and rate performance: the initial discharge capacities were 389, 228, 194, 178, 147 mAh/g at the current density of 12, 24, 60, 120, and 240 mA/g, respectively, retaining 211 mAh/g after 150 cycles. The hard carbon obtained from PVC nanofibers achieved a high reversible capacity of 271 mAh/g and an initial Coulombic efficiency of 69.9%, which were much superior to the one from commercial PVC, namely, a reversible capacity of 206 mAh/g and an initial Coulombic efficiency of 60.9%. These as-prepared hard carbon samples were used as anode materials for Na-ion batteries. ![]() Two types of hard carbon materials were synthesized through direct pyrolysis of commercial polyvinyl chloride (PVC) particles and pyrolysis of PVC nanofibers at 600-800 degrees C, respectively, where the nanofibers were prepared by an electrospinning PVC precursors method.
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