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Here, we present a comprehensive study of choice of electrolyte, anode and cathode to develop commercially viable non-flammable sodium-ion battery. We report hard carbon (HC) vs. Na using ether-based non-flammable electrolyte (1 ​M NaBF4 in tetraglyme) and compare storage performance, thermal stability and SEI formation with those obtained using carbonate-based electrolyte (1 ​M NaClO4 in EC:PC = 1:1 v/v). The results shows that 1 ​M NaBF4 in tetraglyme works as a better electrolyte than carbonate-based electrolyte for HC anode. We present and compare storage performances of pristine and aliovalent-doped Na3V2(PO4)3 (NVP) vs. Na. Doped-NVP outperforms pristine cathode in terms of specific capacity and rate capability. 18650-type non-flammable sodium-ion cells fabricated using modified NVP vs. HC exhibits energy density of 60 ​Wh kg−1. When discharged at a high rate close to 5C, the cell successfully retains 83% of its storage capacity obtained at low rate. When cycled at C/5, doped NVP vs. HC 18650 ​cell retains 90% of its initial capacity after 200 cycles.

We report the synthesis, characterization, and performance evaluation of tungsten (W) incorporated vanadium oxide (VO2) nanocomposite cathode material for improved lithium storage performance. VO2 nanorods, 100–200 nm in diameter and 1–3 μm in length are synthesized using a hydrothermal method. W incorporation at different weight percent results in the VO2 morphology shifting from rods to a sheet type structure. The lithium storage performance of VO2 has improved remarkably by increasing the loading of W to an optimal level, which influence the intercalation/ deintercalation of lithium ions into the expanded lattices of VO2. The maximum specific capacity observed for the optimal VO2/W4 composite was 381 mAh/g at a current density of 0.1 C. Cyclic voltammetry measurements showed the presence of an electroactive V3+/V4+ redox couple, leading to lower peak separation and voltage polarization differences. Superior charge storage performance was observed with the VO2/W4 composite as compared to the VO2 based devices.

NASICON-structured Li1+xZr2-xLax(PO4)3 (x = 0–0.2) solid electrolytes are prepared by sol-gel method. The influence of substitution of La3+ for Zr4+ on the ionic conductivity, morphology, and structure of the parent compound LiZr2(PO4)3 (LZP) is investigated. Rietveld refinement of powder x-ray diffraction data reveals that the La3+ substitution stabilizes the LZP in the highly conducting rhombohedral R 3 ¯ c phase at room temperature. La3+ substituted LZP display enhanced ionic conductivity, showing the highest ionic conductivity of 0.72 × 10−4 S/cm at room temperature for the composition Li1.1Zr1.9La0.1(PO4)3. The improvement in conductivity of LZP with another aliovalent substituent, Mg2+, whose ionic radii is similar to Zr4+ (0.72 A) is also investigated. Further, the activation energy decreases from 0.53 eV for the parent LZP to 0.42 eV for x = 0.1 La3+ substituted LZP. Lithium-ion transference number obtained by direct current polarization for Li1.1Zr1.9La0.1(PO4)3 is 0.99, confirming the high ionic conducting nature of the solid electrolyte. Cyclic voltammetry recorded for Li1.1Zr1.9La0.1(PO4)3 shows electrochemical stability window up to ∼4.0 V vs. Li. In particular, La3+ substituted NASICON-type LZP (x = 0.1) exhibits good chemical and structural stability after exposing to air, water, Li metal, acidic and basic solutions.

In this article, we report a high-performing fluorophosphate-based cathode material for sodium-ion battery, namely NaVPO4F, synthesised by a facile one-step soft template method. We compared physical and electrochemical properties between the NaVPO4F materials synthesised using V2O3 and V2O5 as starting precursors. FESEM images show that the samples consist of particles of size in the range 200–800 nm. The synthesised NaVPO4F using V2O5 cycled vs. sodium metal at 0.1 C is able to deliver a high discharge capacity of 133 mAh g−1, with a flat discharge plateau at 3.33 V. At a moderate current rate of 1 C, it still manages to achieve a reversible discharge capacity of 121 mAh g−1, and retains 82% of its initial capacity after 2500 cycles. Notably, this electrode material exhibits impressive long-term cyclability at high rates, where it is able to retain 81 and 77% of respective initial discharge capacities even after 10,000 cycles at 10 and 20 C. This durable performance of NaVPO4F using V2O5 precursor is attributed to the good electrode surface integrity owing to negligible volume changes as confirmed by FESEM experiment.

Viability of room-temperature rechargeable in-situ sodium plated batteries (INPBs) with bare Cu current collector foil as anode is reported which operated by sodium plating-stripping on Cu foil during each charge-discharge cycle, respectively. Using 1M NaBF4 in tetraglyme electrolyte, an Na2Fe2(CN)6//Cu INPB delivered 336Wh/kg specific energy density with 76% retention in 100cycles. Keywords: In-situ sodium plating, Anode-free, Current collector anode, Non-dendritic, NaBF4 in tetraglyme, Na2Fe2(CN)6

The individual physico-chemical processes in lithium-ion batteries namely solid-state diffusion and charge transfer polarization are difficult to be tracked by impedance spectroscopy due to simultaneous contributions from cathode and anode. A deeper understanding of various polarization processes in lithium-ion batteries is important to enhance storage performance and cycle life. In this context, the polarization processes occurring in cylindrical 18650 cells comprising different cathodes against graphite anode (LiNi 0.2 Mn 0.2 Co 0.6 O 2 vs. graphite; LiNi 0.6 Mn 0.2 Co 0.2 O 2 vs. graphite; LiNi 0.8 Co 0.15 Al 0.05 O 2 vs. graphite and LiFePO 4 vs. graphite) are investigated by deconvolution of impedance spectra across various states of charge. Further, cathodes and anodes are extracted from the investigated 18650-type cells and tested in half-cells against Li-metal as well as in symmetric cell configurations to understand the contribution of cathode and anode to the full cells of various battery chemistries studied. Except for the LiFePO 4 vs. graphite cell, the polarization resistance in graphite of other cells are found to be higher than those of the investigated cathodes, proving that the polarization in lithium-ion battery is largely influenced by the graphitic anode. Furthermore, the charge transfer polarization resistance encountered by the cathodes investigated in this work is found to be a strong function of the states of charge.

Here we report a polyanion-based cathode material for sodium-ion batteries, Na 2 MnSiO 4 , registering impressive sodium storage performances with discharge capacity of 210 mAh g −1 at an average voltage of 3 V at 0.1 C, along with excellent long-term cycling stability (500 cycles at 1 C). Insertion/extraction of ∼1.5 mol of sodium ion per formula unit of the silicate-based compound is reported and the utilisation of Mn 2+ ⇋ Mn 4+ redox couple is also demonstrated by ex-situ XPS. Besides, this study involves a systematic investigation of influence of the electrolyte additive (with different content) on the sodium storage performance of Na 2 MnSiO 4 . The electrolyte additive forms an optimum protective passivation film on the electrode surface, successfully reducing manganese dissolution.

In this article, we propose key design criteria to synthesis carbon coated α-Li3V2(PO4)3 positive electrode material for high power lithium batteries. A facile and scalable one-pot soft template method is adopted to synthesize α-Li3V2(PO4)3/C (LVP/C), which exhibits unique morphology of micron-size mesoporous secondary particles comprising interconnected primary nanoparticles showing good storage and rate performances with long cycle life. This cathode material displays high discharge capacities of 178, 90 and 59 mAh.g−1 at 0.1C, 30C and 80C, respectively. The mesoporous LVP/C with a 3D lithium diffusion network exhibits better rate performance (90 mAh.g−1 at 30C) as compared to the known phosphate, silicate or oxide cathode materials for lithium-ion batteries (LIBs). In addition, LVP/C electrode material retains 80% (at 1C) and 100% (at 20C) of its initial capacity after 1,000 cycles. The phase transitions during delitiation/litiation are discussed at different cutoff voltages, corresponding to the number of moles of lithium involved in the redox reactions. The reversibility of electrochemical extraction/insertion processes are confirmed using operando XRD measurements. Observed storage performances can be attributed not only to high crystallinity of LVP/C calcined at 800°C for 6 h; also to the unique mesoporous architecture of this carbon coated cathode material forming high packing density during the soft template synthesis. Obtained dense packed mesoporous architecture of LVP/C allows favourable (i) electrolyte wettability for lithium-incorporation from the electrolyte and (ii) long electronic wiring by the well-connected carbon coating towards the current collector.

We report here thermal behaviour and various components of heat loss of 18650-type LiFePO4/graphite cell at different testing conditions. In this regard, the total heat generated during charging and discharging processes at various current rates (C) has been quantified in an Accelerating Rate Calorimeter experiment. Irreversible heat generation, which depends on applied current and internal cell resistance, is measured under corresponding charge/discharge conditions using intermittent pulse techniques. On the other hand, reversible heat generation which depends on entropy changes of the electrode materials during the cell reaction is measured from the determination of entropic coefficient at various states of charge/discharge. The contributions of irreversible and reversible heat generation to the total heat generation at both high and low current rates are evaluated. At every state of charge/discharge, the nature of the cell reaction is found to be either exothermic or endothermic which is especially evident at low C rates. In addition, electrochemical impedance spectroscopy measurements are performed on above 18650 cells at various states of charge to determine the components of internal resistance. The findings from the impedance and thermal loss analysis are helpful for understanding the favourable states of charge/discharge for battery operation, and designing better thermal management systems.

We report the synthesis of low and high temperature polymorphs of Li 2 MnSiO 4 and dependence of lithium storage performance on such polymorphs. Two polymorphs namely, Pmn 2 1 (low temperature/orthorhombic polymorph) and P 2 1 / n (high temperature/monoclinic polymorph) are isolated by controlling the calcination temperature. Among them the electrochemical performance of Pmn 2 1 is found to be better than P 2 1 / n . Orthorhombic polymorph ( Pmn 2 1 ) of carbon coated Li 2 MnSiO 4 exhibits an impressive discharge capacity of 262 mAh g −1 at 0.1C and rate performance up to 5C; in contrast P 2 1 / n delivers only a discharge capacity of 164 mAh g −1 at 0.1C at room temperature. Notably, the capacity of Pmn 2 1 phase is almost 1.5–2 times higher than P 2 1 / n phase at all current rates. Capacity retention of 90% is reported for orthorhombic polymorph until 30 cycles at 0.1C. Further the voltage profiles and polarization of orthorhombic phase are much better than the monoclinic phase. Such perceivable differences in the rate performances and voltage profiles is argued to be due to variations in the activation energy barrier and hopping distance of lithium-ion in the crystal structures. Besides the role of polymorphism, we also show here that the structural stability during cycling is critical in retaining high storage performance.

A new sodium storage pathway is unveiled for the anode Na2Ti3O7 which involves the newly discovered intermediate phase of Na3 − xTi3O7. Details about this Na2Ti3O7 ⇋ Na3 − xTi3O7 sodium storage pathway and how it relates to the conventional Na2Ti3O7 ⇋ Na4Ti3O7 pathway are mentioned. This Na2Ti3O7 ⇋ Na3 − xTi3O7 pathway has the lowest redox voltage of 0.2 V vs Na/Na+ ever reported for any non-carbon based sodium-ion battery anode along with moderately high capacity approaching 89 mAh/g, negligible polarization, excellent rate performance (up to 80 C, or 45 s response) and good cycle life till 1500 cycles. These results indicate this pathway's potential as an anode for sodium-ion batteries meant for diverse applications. Keywords: Na2Ti3O7, Na3 − xTi3O7, Lowest voltage anode, Voltage step, Sodium-ion battery

Two new organic dyes based on trifluorenylamine donor and cyanoacrylic acid acceptor have been synthesized and characterized by optical and electrochemical measurements and density functional theory calculations. It is found that the trifluorenylamine donor is beneficial to red-shift the absorption and to lower the oxidation potential when compared to the triphenylamine donor. The variations in the photovoltaic performance of the dyes are corroborated by the dye loading data, incident photon to current conversion efficiency and the interfacial kinetic parameters estimated from the intensity modulated photovoltage/photocurrent spectral measurements. A dye with fluorene and bithiophene segments in the π-linker exhibited device efficiency up to 5.8%. The enhanced power conversion efficiency exhibited by this dye when compared to its analogue containing diphenylaminofluorne donor is attributed to its superior anti-aggregation ability and the comparatively prolonged electron lifetime.

Palladium nanoparticles decorated graphene (Gra/Pd nanocomposite) was synthesized by simultaneous chemical reduction of graphene oxide and palladium salt in a single step. The negatively charged graphene oxide (GO) facilitates uniform distribution of Pd 2+ ions onto its surface. The subsequent reduction by hydrazine hydrate provides well dispersed Pd nanoparticles decorated graphene. Different amount of Pd nanoparticles on graphene was synthesized by changing the volume to weight ratio of GO to PdCl 2 . X-ray diffraction studies showed FCC lattice of Pd with predominant (1 1 1) plane. SEM and TEM studies revealed that thin graphene nanosheets are decorated by Pd nanoparticles. Raman spectroscopic studies revealed the presence of graphene nanosheets. The electro-catalytic activity of Gra/Pd nanocomposites toward methanol and ethanol oxidation in alkaline medium was evaluated by cyclic voltammetric studies. 1:1 Gra/Pd nanocomposite exhibited good electro-catalytic activity and efficient electron transfer. The kinetics of electron transfer was studied using chronoamperometry. Improved electro-catalytic activity of 1:1 Gra/Pd nanocomposite toward alcohol oxidation makes it as a potential anode for the alcohol fuel cells.

An architecture featuring carbon coated, interconnected nano-grains constructed with mesopores is developed for LiMnPO 4 cathode material. This architecture facilitates enhanced lithium ionic and electronic transports; favours improved lithium storage performance. Mesoporous LiMnPO 4 /C electrode delivers discharge capacity of 140 mAh g −1 at 0.05 C using galvanostatic cycling mode. This best electrochemical response of LiMnPO 4 /C at constant current mode is complemented by diffusion studies using cyclic voltammetry and impedance spectroscopy. Further, the interdependence of lithium storage performance on carbon content, milling time (2, 4, 6 and 10 h), grain size and porous characteristics (surface area, pore size and pore volume) is also discussed. Finally, the feasibility of LiMnPO 4 /C cathode is evaluated against Li 4 Ti 5 O 12 /C anode in a full cell.

Metal oxide semiconductors are promising interfacial materials for organic photovoltaics (OPVs) because of their electrical properties and solution processability. In this article, we report the fabrication of poly(3-hexylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester (P3HT:PCBM) OPV devices incorporating solution-based NiO interfacial layers that show promising enhancements of the device photocurrent and stability. We discuss the impact of parasitic shunt and series resistances on device performance as well as the ambient degradation of these devices, studied with intensity modulated photocurrent spectroscopy (IMPS). The results showed that charge extraction was predominantly affected by degradation via decrease in carrier mobility and increased trapping/recombination, revealing the physical mechanism behind the degradation observed. 2012 Elsevier Ltd. All rights reserved.

The present work demonstrates the usefulness of nickel oxide as a hole transporting material in solid state dye-sensitized solar cells (SSDSSCs). We report on the photovoltaic performances of sensitized TiO2/NiO heterojunctions, and demonstrate that the TiO2 film thickness and morphology, as well as NiO film thickness, have significant effects on the photovoltaic behaviour of TiO2/NiO SSDSSC. Under 1 sun AM1.5G simulated illumination, the SSDSSCs demonstrated best photovoltaic performance with a short circuit photocurrent density, open circuit voltage, fill factor and efficiency of 0.91 mA cm−2, 780 mV, 40% and 0.3%, respectively. This study draws attention to the feasibility of enhancing the photovoltaic performance in SSDSSC devices through development of appropriately designed sensitized TiO2/NiO heterojunctions.

The present work is devoted to a systematic investigation of ionic and electronic conductivity as well as chemical Li-diffusivity in single crystalline LiFePO 4 as a function of crystallographic orientation over an extended temperature range. Besides chemical analysis of the elemental ratio of the crystal, we also determined the Fe occupancy on the lithium lattice positions by single crystal X-ray diffraction and synchrotron X-ray radiation followed by Rietveld refinement. AC impedance as well as improved DC polarization/depolarization measurements have been carried out using electronically as well as ionically blocking cells. The activation energies obtained for electronic and ionic conductivities are in the range of 0.55–0.59 eV and of 0.62–0.74 eV, respectively, depending on the orientations. The ionic conductivity is much smaller than the electronic conductivity along all three axes and the electronic conductivity, ionic conductivity and chemical diffusivity of Li ion are found to be effectively two-dimensional (i.e., isotropic in the b–c plane).

Me/LiX nanocomposites (Me – transition metal and X = F or O) exhibit extra lithium storage, with pseudo-capacitive behavior and high-rate performance. While LiX surface layers or the interfacial core serves as hosts for extra Li, atoms of contacting transition metal serve as electron sinks, depending on Me electronegativity. To verify the mechanism, we have performed comparative DFT-LCAO calculations on the polar Ti|Li|Li2O(111) and non-polar Cu|Li|LiF(001) interfaces with extra Li atoms inserted inside both 2D interfaces, gradually changing their concentration. Theoretical calculations confirm validity of this interfacial model for explanation of the extra storage capacity at low potentials. The diffusion barrier for extra Li atom along the Me/LiX interface is markedly smaller than the Li penetration barrier into the bulk.

In this paper, we highlight the field of nano-ionics which in contrast to the well established field of nano-electronics is still in status nascendi. We present some of our recent findings of different physical phenomena in the field of nano-ionics with special emphasis in the context of lithium batteries, addressing the following anomalies in various properties: (a) enhanced storage, Coulombic efficiency and excess storage at low potential due to interfacial insertion reaction, (b) thermodynamic aspects giving rise to excess cell voltage and curved shapes instead of plateau regions during multiphase co-existence and (c) transport behavior in a new class of soft matter electrolytes that combines high ionic conductivities at room temperature with the favorable properties of ‘soft matter’. Thus we emphasise here that the nano-ionics is relevant not only for fundamental science, but also important for technological applications.

Nanocrystalline tin oxide (SnO2) material with different grain sizes was synthesized by using a chemical precipitation method. This material was characterized by using the X-ray diffraction and transmission electron microscopy. The electrical properties of compressed nanocrystalline SnO2 were studied by using impedance spectroscopy. AC conductivity data for SnO2 material having grain sizes between 9 and 34 nm were analyzed using a power law. The exponent n is found to be 0.5 for bulk (34 nm) and unity for material with grain size below 18 nm. The results show a universal behavior for very low average grain sizes and the non-universal behavior for larger grain sizes even at room temperature.

Ionic conductivity of a series of fluorite-type solid solutions Pb1-xYxF2+x (0.007 ≤ x ≤ 0.222) has been measured in the frequency range 100 Hz – 3 MHz and in the temperature range 25–250oC under vacuum. The conductivity decreases and the activation energy increases gradually upon increasing the yttrium content up to ∼ 4.5 mol % of Y3+ whereas, beyond that and up to 22 mol % of Y3+, the ionic conductivity increases and the activation energy decreases. Thus two distinct regions in the general composition Pb1-xYxF2+x could be delineated, in one the polarizability factor predominates over the number of extra-interstitial F anions and vice-versa in the other region. These results indicate the competing effects between the disorder caused by interstitial F anions and the polarizability of the host and guest cations.

Dielectric constant ( e ′) and dielectric loss tangent (tan δ ) of gadolinium substituted Ni–Zn ferrites have been investigated in the high frequency range 1–15 MHz by an HP 4192A impedance analyser controlled by a PC. The values of complex dielectric constant ( e ″) have been computed from e and tan δ . Plot of e ′ and tan δ vs. frequency show a normal dielectric behaviour of spinel ferrites. A qualitative explanation is given for the composition and frequency dependence of dielectric constant and dielectric loss tangent.

Melt quenching of a 1:4 mixture of NH4I and AgI was attempted in order to achieve rapid, large-scale synthesis of NH4Ag4I5 (“145”). The characterization of the as-quenched and annealed samples through DCS, IR and X-ray diffraction reveal (i) the thermodynamic evidence for “145” through endotherms at 235°C (incongruent melting) and −75°C (phase transition); (ii) disordered NH4+ groups and (iii) the need to anneal at temperatures below 147°C to obtain pure “145” phase. Crystallization from KI solution offers another attractive method for synthesis of stable “145”.

The high-temperature plastic phase (α-phase) of lithium sulphate with FCC structure has been stabilized at ambient by programmed quenching of the melt, aided by a few per cent of lithium carbonate which arrests the cubic to monoclinic phase transformation. The metastable phase thus obtained has been characterized by X-ray diffraction ( a = 6.98(4) A), differential scanning calorimetry (endothermic humps at 351 and 542°C in QL 200 ), a.c. electrical conductivity, infrared and electron spin resonance spectroscopy. DSC experiments provide unequivocal thermodynamic characterization of α-phase. Electrical conductivity of this phase is enhanced by ∼6 orders relative to the insulating monoclinic phase, with an activation energy of 0.4 eV, characteristic of α-Li 2 SO 4 . The micro-crystalline phase obtained by quenching at 300°C shows a two-slope Arrhenius plot (1.13 and 0.05 eV) with a knee separating them. The activation energy for high-temperature conductivity decreases systematically from 1.13 to 0.18eV, upon prolonged isothermal annealing suggestive of molecular relaxation leading to the optimization of Li + conduction paths. The i.r. spectra reflect the quenched-in disorder by way of broadening of peaks characteristic of SO 2− 4 and of the stabilizer CO 2− 3 ions. The ESR spectra of quenched Li 2 SO 4 , upon X-irradiation has given interesting microscopic evidence of a dynamically disordered C0 2− 3 by way of an intense isotropic (g ≈ 2.009) spectrum characteristic of the tumbling CO 3 − radical.

An ESR study on 60AgI-30Ag2O-10B2O3 (300–473 K) is reported. The spectra showed two Ag2+ centres at RT. The origin of these centres is discussed in light of the model structure of Minami et al. and our DSC results.

DSC, a.c. electrical conductivity and IR spectra of quenched Li2So4 are employed to investigate the nature of the f.c.c. superionic (high temperature) phase stabilized at ambient temperatures by quenching. DSC results suggest a two-state phase transition in the range 520–570°C with the enthalpies of the two stages depending sensitively on quenching temperature, pointing to the existence of two structurally distinct SO2-4 groups, one of which is possibly involved in superionic conduction. Electrical conductivity is enhanced by many orders of magnitude with lower activation energy compared to the purely low temperature phase. IR spectra contain features that provide additional evidence for co-operative rotations of distinct SO2-4 group (characteristic of plastic phase) as a feasible mechanism for enhanced Li+ ion conduction.