A simple and scalable method is developed to prepare highly wrinkled graphene sheets – carbon nanospheres (WG-CN) composite for ultra high energy density supercapacitor application. Here, we introduce a novel simple paraffin wax candle flame technique for the simultaneous reduction of graphene oxide (GO) and deposition of carbon nanospheres on the graphene sheets. This is followed by introducing permanent wrinkles to the composite. The WG-CN composite exhibit the high specific capacitance values of 290 F g-1 and 253.7 F g-1 (138.5 F cm-3) for 6M KOH and EMIMBF4 ionic liquid electrolytes respectively. The ultra high energy density values of 108 Wh Kg-1 and 58.9 Wh L-1 has been obtained at the power density of 3955 W Kg-1 and 2157 W L-1 simultaneously. These attractive performances exhibited by the WG-CN composite supercapacitor electrode make them potential candidate for future energy storage devices. The key to success of this composite is the ability to make full utilization of the high intrinsic specific surface area of the nanocomposite.

In the present work, NaI – LiBH4 system fabricated by ball milling were post annealed and their variation of Li+ ion conductivity were investigated. From the change of lattice parameters by post annealing, it was suggested that unreacted LiBH4 existed in as-milled sample further dissolved into NaI, which implied an enhancement of the sample homogeneity. On the other hand, the segregation of LiI was anticipated when ball milled 15NaI·LiI (BH4 free sample) was annealed at 423 K. Li+ conductivity was decreased by post anneal process and compositional dependence of an activation energy for Li+ conduction was indicated for the homogeneous NaI – LiBH4 system.

Ag7Fe3(P2O7)4 is a 3D structured material which has been recently studied as a possible cathode material for lithium batteries. Notably, Na7Fe3(P2O7)4 is reported to be a fast-ion conductor, yet poor electrical conductor. Here, partial replacement of Na+ for Ag+ yielded Na2Ag5Fe3(P2O7)4 pyrophosphate framework where the formation of Ag metal is proposed to increase the intrinsic low electrical conductivity of this polyanion electrode. Specifically, the Ag5Na2Fe3(P2O7)4 -Ag composite is synthesized via chemical reduction of Ag7Fe3(P2O7)4 using NaBH4. The occupancy of Ag+ and Na+ in each site was determined via Rietveld analysis of the diffraction pattern. Electrochemistry of the Ag5Na2Fe3(P2O7)4 -Ag metal composite was explored with voltammetry and galvanostatic charge/discharge cycling. The Ag5Na2Fe3(P2O7)4 -Ag metal composite electrodes displayed good rate capability assisted by the presence of Ag metal from the chemical reduction and in-situ electrochemical formation of a Ag conductive network.

In this study, we conducted the first energy dispersive x-ray diffraction (EDXRD) experiments on Li/Li1.1V3O8 coin cells discharged to different lithiation levels in order to investigate the phase transitions upon electrochemical reduction. The phase transformation from layered Li-poor α to Li-rich α to defect rock-salt β phase was confirmed with cells of different lithiation stages. No spatial localization of phase formation was observed throughout the cathodes under the conditions of this measurement.

Cryptomelane type manganese dioxides (α-MnO2, OMS-2) are interesting potential cathode materials due to the ability of their one dimensional (1D) tunnels to reversibly host various cations including Li+ and an accessible stable 3+/4+ redox couple. Here, we synthesized metal cation free OMS-2 materials where the tunnels were occupied by only water and hydronium ions. Water was subsequently removed from the tunnels. Cation free OMS-2 and Dry-OMS-2 were used as cathodes in Li based batteries to investigate the role of tunnel water on their electrochemistry. The initial discharge capacity was higher for Dry-OMS-2 (252 mAh/g) compared to OMS-2 (194 mAh/g), however, after 100 cycles Dry-OMS-2 and OMS-2 delivered 137 mAh/g and 134 mAh/g, respectively. Li+ ion diffusion was more facile for Dry-OMS as evidenced by rate capability, at 400 mA/g. Dry-OMS-2 delivered 135mAh/g whereas OMS-2 delivered ∼115 mAh/g. This first report of the impact of tunnel water on the electrochemistry of OMS-2 type materials demonstrates that the presence of tunnel water in OMS-2 type materials negatively impacts the electrochemistry.

Micro-scale energy storage devices are of great importance to the advancement of low maintenance, high power electronics. They can easily be used in applications that extract energy from mechanical, solar, thermal and thermoelectric sources. Several of these devices have achieved mean areal capacitance of 1.5 mF cm-2 and maximal energy and power densities of 6.6 mJ cm-2 and 44.9 mW cm-2, respectively. It has been demonstrated that a smaller interspace enhances the performance. Currently, these types of devices are only made possible by using several micro-fabrication steps and techniques that are cost prohibitive and limit the larger scale manufacturability. We present a simple but highly scalable and cost effective method in fabricating high power interdigitated micro energy storage devices using binder-free carbon nanotubes membranes and laser irradiation to obtain interspaces on the order of 75 μm. The binder-free electrode devices show higher power density and an improved frequency response, compared to what has been reported in the literature. Additionally, we observed significant reduction in cell resistance leading to enhancement in cell capacitance, and consequently, an increase in energy density.

The majority of improvements to LIB technology have come through the development of new novel cathode materials. One promising cathode material is Li2FeSiO4 (LFS), desirable for its low cost and high theoretical capacity. However, the ionic conduction and transport mechanisms within this material are still not well understood, and require further investigation to improve upon cycling rate performance. To this end combined measurements of XRD & XANES have been performed in operando on LFS during electrochemical cycling, i.e. at selected electrochemical states of charge during the formation cycle the crystalline structure and the transition metal oxidation state as well as the site symmetry were characterized via the two aforementioned techniques. These in operando measurements expose once more a charging rate-dependent phase evolution during the formation cycle, which can be well characterized using a simplified equivalent circuit analogue.

At high activation energy, kinetic processes require the accumulation of several excitations in order to take place. This accumulation implies an entropy, which we call multi-excitation entropy. This explains the isokinetic rule, which itself explains the existence of isoequilibrium relations. Understanding the implications of these effects helps clarify the microscopic mechanisms in kinetic processes, including hydrogen storage, and transport of protons, and potentially, of other ions, in condensed matter.