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High-performance anodes for rechargeable Li-ion batteries are produced by nanostructuring of transition metal oxides on a conductive support. Here, we demonstrate a hybrid material of MnO2 directly grown onto fabrics of carbon nanotube fibres, which exhibits notable specific capacities over 1100 and 500 mA h g−1 at discharge current densities of 25 mA g−1 and 5 A g−1, respectively, with a coulombic efficiency of 97.5%. Combined with 97% capacity retention after 1500 cycles at a current density of 5 A g−1, both capacity and stability are significantly above literature data. Detailed investigations involving electrochemical and in situ synchrotron X-ray scattering studies reveal that during galvanostatic cycling, MnO2 undergoes an irreversible phase transition to LiMnO2, which stores lithium through an intercalation process, followed by a conversion mechanism and pseudocapacitive processes. This mechanism is further confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. The fraction of pseudocapacitive charge storage ranges from 27% to 83%, for current densities from 25 mA g−1 to 5 A g−1. The firm attachment of the active material to the built-in current collector makes the electrodes flexible and mechanically robust, and ensures that the low charge transfer resistance and the high electrode surface area remain after irreversible phase transition of the active material and extensive cycling. [ABSTRACT FROM AUTHOR]

Uniform colloidal building-blocks enable the creation of more stable, structurally sophisticated materials. Here we describe a simple polymer-mediated approach to generate grams of monodisperse, single-crystal α-Mn2O3 nanocrystals bound by {111} facets. The technique is inspired in part by biomineralization, where organisms use macromolecular matrices or compartments to trigger the oriented nucleation and growth of crystalline phases. Polyvinylpyrrolidone (PVP) behaves as a polymeric nano-reactor by coordinating to the manganese (Mn) precursor while recruiting the NOx oxidizing agent from solution to drive the co-precipitation of the manganese oxide. PVP also serves as a molecular template to guide the nucleation of trigonal bipyramids composed of Mn3O4. The porosity of the Mn3O4 particles indicates that they form non-classically via oriented attachment instead of atom-by-atom. The particles are further oxidized and transform into single-crystal α-Mn2O3 octahedra. This co-precipitation approach is advantageous because it can generate large amounts of monodisperse nanocrystals at low economic cost. α-Mn2O3 is an alternative lithium ion battery (LIB) anode material that is earth abundant and has ∼2.7 times higher capacity than conventional graphite anodes. We assembled the monodisperse α-Mn2O3 octahedra into LIB anodes to examine their performance in a realistic device. The α-Mn2O3 octahedra exhibit good rate performance, cycling stability, coulombic efficiency and morphology retention during extended lithiation–delithiation cycles compared to previous reports for this material. We attribute the improved electrochemical performance of the α-Mn2O3 octahedra to the lack of agglomeration in the uniformly distributed electrode and improved lithiation of single crystalline α-Mn2O3 nanoparticles. [ABSTRACT FROM AUTHOR]

Amorphous and turbostratic porous carbon spheres are synthesized through a template-free spray pyrolysis method. Anodes composed of these non-graphitic carbon spheres outperformed the commercial graphitic carbon anodes in rechargeable Li-ion batteries. A discharge capacity of 378 mA h g−1, which is equivalent to the theoretical limit of 372 mA h g−1, is achieved at a current density of 0.1 C (37.2 mA g−1). At a higher charge–discharge rate of 1 C, electrochemically most active turbostratic carbon spheres exhibited a reversible specific capacity of 270 mA h g−1, which is 4-fold higher compared to those of commercial graphitic carbon anodes. After 100 charge–discharge cycles at current densities of 0.1 C and 1 C, carbon spheres retained stable specific capacities of 365 and 250 mA h g−1, respectively. Spectroscopic and microscopic investigation of porous carbon anodes after 100 galvanostatic cycles illustrated an excellent structural stability of turbostratic carbon spheres during the lithiation–delithiation process. The notably higher electrochemical performance of carbon spheres is explained by their disordered crystal structure and porosity, which resulted in lower impedance and superior rate performance. This study demonstrates porous turbostratic carbon spheres having a higher charge potential and sloping profile as promising anodes for rechargeable Li-ion batteries. [ABSTRACT FROM AUTHOR]

A new method was developed to synthesize nanosheet-assembled TiO2–B microflowers for Li-ion batteries. Significantly higher electrochemical performance of these microflowers compared to other TiO2–B nanostructures was attributed to their hierarchical microstructure and exposed (1 1̅ 0) facets of the individual nanosheets. [ABSTRACT FROM AUTHOR]