There is a need to develop high-capacity, stable anode materials for the next generation of lithium ion batteries that will power consumer electronics and automobiles of the future. This report describes a systematic experimental and theoretical evaluation of a series of hydrogenated fullerenes (C60H x ) for use as high-capacity anodes in lithium ion batteries. It was discovered that there is an optimal degree of hydrogenation for C60 to achieve reversible lithiation. Under the optimized conditions, C60H x was found to have a stable capacity of 588 mAh/g for over 600 cycles at a current density of 0.05 A/g. Extended cycling studies at higher current densities demonstrated that this material is stable for 2000 cycles. Theoretical modeling of this system determined that electronic structure changes due to hydrogenation is responsible for the favorable interaction of Li+ with C60H x . This study represents a unique methodology for increasing anode capacity and optimization of an anode’s electrochemical properties by controlling the hydrogen content of the active material.

Abstract:In this study, we analyze and compare the physical and electrochemical properties of an all solid-state cell utilizing LiBH 4 as the electrolyte and aluminum as the active anode material. The system was characterized by galvanostatic lithiation/delithiation, cyclic voltammetry (CV), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Constant current cycling demonstrated that the aluminum anode can be reversibly lithiated over multiple cycles utilizing a solid-state electrolyte. An initial capacity of 895 mAh/g was observed and is close to the theoretical capacity of aluminum. Cyclic voltammetry of the cell was consistent with the constant current cycling data and showed that the reversible lithiation/delithiation of aluminum occurs at 0.32 V and 0.38 V (vs. Li + /Li) respectively. XRD of the aluminum anode in the initial and lithiated state clearly showed the formation of a LiAl (1:1) alloy. SEM-EDS was utilized to examine the morphological changes that occur within the electrode during cycling. This work is the first example of reversible lithiation of aluminum in a solid-state cell and further emphasizes the robust nature of the LiBH 4 electrolyte. This demonstrates the possibility of utilizing other high capacity anode materials with a LiBH 4 based solid electrolyte in all-solid-state batteries.

Partially-unzipped multiwalled carbon nanotubes (PUCNTs) combine the chemical structure and basic mechanical properties of multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) with exceptionally high graphene-edge content. As a result, PUCNTs can be effectively oxidized for dispersion in aqueous solutions and have a specific surface area that is larger than that of MWCNTs with a comparable aspect ratio. Thus, the incorporation of relatively small concentrations of PUCNTs in cement composites may result in significant physicomechanical enhancements. In the proof-of-concept study presented here, cement paste specimens were manufactured with oxidized PUCNT concentrations of 0, 0.001, and 0.005% in weight of cement (wt%), that is, one order of magnitude smaller than lower-bound concentrations for MWCNTs reported in the literature. Stable dispersion in water was verified through dynamic light scattering analysis. Physicomechanical changes and PUCNT dispersion in the cement matrix were investigated through uniaxial compression tests on 25 × 25 × 76 mm prism specimens, and visual inspection of scanning electron microscopy (SEM) micrographs, respectively. The incorporation of 0.001 wt% and 0.005 wt% of PUCNTs resulted in an average increase in compressive strength of 10% and 29%, respectively, compared with plain cement paste. In both instances, representative SEM micrographs show the preferential formation of cement hydrates in cement paste that accorded with well-dispersed PUCNTs.