The development and the characterization of a nanostructured binder-free anode for lithium-ion batteries exploiting the germanium high theoretical specific capacity (1624 mAh g(-1) for Li22Ge5 alloy) is herein presented. This anode secures remarkable performances in different working conditions attaining a 95% capacity retention at 1C (i.e., 1624 mA g(-1)) after 1600 cycles at room temperature and a specific capacity of 1060 mAh g(-1) at 10C and 450 mAh g(-1) at 60C. The nanostructured binder-free germanium-based anode shows also strong resilience in terms of temperature tests, being it tested from-30C to +60C. Indeed, the specific capacity remains unaltered from room temperature up to +60C, while at 0C the cell is still retaining 85% of its room temperature capacity. In a full-cell configuration with LiFePO4 as cathode, the Ge anode showed a stable specific capacity above 1300 mAh g(-1) for 35 cycles at C/10. Concerning the fabrication procedure, a two-step realization process is applied, where a Plasma Enhanced Chemical vapor Deposition (PECVD) is employed to grow a germanium film on a molybdenum substrate followed by hydrofluoric acid (HF) electrochemical etching, the latter having the scope of nanostructuring the Ge film. Finally, compositional, morphological, and electrochemical characterizations are reported to fully investigate the properties of the binder-free nanostructured germanium anode here disclosed.

Recent studies on anatase TiO2 have demonstrated its capability of performing as an anode material for sodium-ion batteries (SIBs) even though, due to poor conductivity, realistic applications have not yet been foreseen. In order to try to address this issue, herein, we shall introduce a cost effective and facile route based on the co-precipitation method for the synthesis of Mo-doped anatase TiO2 nanoparticles with AlF3 surface coating. The electrochemical measurements demonstrate that the Mo-doped anatase TiO2 nanoparticles deliver an ∼40% enhanced reversible capacity compared to pristine TiO2 (139.8 vs. 100.7 mA h g-1 at 0.1 C after 50 cycles) due to an improved electronic/ionic conductivity. Furthermore, upon AlF3 coating, the overall system can deliver a much higher reversible capacity of 178.9 mA h g-1 (∼80% increase with respect to pristine TiO2) with good cycling stability and excellent rate capabilities of up to 10 C. The experimental results indicate that the AlF3 surface coating could indeed effectively reduce the solid electrolyte interfacial resistance, enhance the electrochemical reactivity at the surface/interface region, and lower the polarization during cycling. The improved performance achieved using a cost-effective fabrication approach makes the dually modified anatase TiO2 a promising anode material for high-performance SIBs.

In the present study, Al2O3 is utilized for the first time as coating agent on nanostructured anatase TiO2 in order to investigate its effect on sodium-ion batteries performance. Our results show that the Al2O3 coating, introduced by a facile two-step approach, provides beneficial effects to the TiO2-based anodes. However, the coated TiO2 still suffers of capacity fading upon cycling when using 1.0 M of NaClO4 in propylene carbonate (PC) as electrolyte. To address this issue, the influence of different electrolytes (NaClO4 salt in various solvents) is further studied. It is found that the modified TiO2 exhibits significant improvements in cycling performance using binary ethylene carbonate (EC) and PC solvent mixture without the need of the commonly used fluoroethylene carbonate (FEC) additive. Under the best configuration, our battery could deliver a high reversible capacity of 188.1 mAh g(-1) at 0.1C after 50 cycles, good rate capability up to 5C, and remarkable long-term cycling stability at 1C rate for 650 cycles. This excellent performance can be ascribed to the synergistic effects of surface and interface engineering enabling the formation of a stable and highly ionic conductive interface layer in EC:PC based electrolyte which combines the native SEI film and an 'artificial' SEI layer of irreversibly formed Na - Al - O.

Solvothermal synthesis of Ge–MWCNT.

A Li-ion battery anode based on few-layer graphene flakes and ultra-small Si nanoparticles shows a remarkable stability during cycling (0.04% capacity fading per cycle). Our approach offers a viable approach to develop new generation Li-ion battery anodes.

Recently, intensive efforts are dedicated to convert and store the solar energy in a single device. Herein, dye-synthesized solar cell technology is combined with lithium-ion materials to investigate light-assisted battery charging. In particular we report the direct photo-oxidation of lithium iron phosphate nanocrystals in the presence of a dye as a hybrid photo-cathode in a two-electrode system, with lithium metal as anode and lithium hexafluorophosphate in carbonate-based electrolyte; a configuration corresponding to lithium ion battery charging. Dye-sensitization generates electron-hole pairs with the holes aiding the delithiation of lithium iron phosphate at the cathode and electrons utilized in the formation of a solid electrolyte interface at the anode via oxygen reduction. Lithium iron phosphate acts effectively as a reversible redox agent for the regeneration of the dye. Our findings provide possibilities in advancing the design principles for photo-rechargeable lithium ion batteries.

P2-Na2/3[NixMny]O2-based cathode materials are promising candidates for Na-ion batteries. The cycling performance of these cathodes was usually reported to drop at working voltages over 4.2 V, due to the P2/O2 irreversible phase transition. Here we demonstrate a colloidally assisted two-step synthesis to phase pure P2-Na0.43Ni0.25Mn0.75O1.9. The adopted synthetic route and the chosen Na:Ni:Mn ratio (0.43:0.25:0.75) leads to a cathode material that can withstand long charge/discharge cycles at working voltages up to 4.4 V. The XRD pattern recorded on the de-sodiated electrode (4.4 V) does not evidence the presence of any peak related to the O2 phase, corroborating the effective suppression of the P2/O2 phase transition upon Na+ intercalation/deintercalation. The discharge capacity delivered at relatively low current (C/10) is 109 mAh g-1, with a capacity retention exceeding the 93% in 20 cycles. At the high current of 1C the delivered discharge capacity is 94 mAh g-1.

Despite the considerable initial optimism behind its development and prospective commercialization, the Li/air battery chemistry has now reached a mature stage of development, which has served to highlight the main underlying technological limitations, as well as what can realistically be expected from it. One of the main challenges is the control of the discharge product morphology, that is, Li2O2, onto the positive electrode. In this article, we show how the three-phase configuration required to ensure cell operation can be induced in a two-phase system made of mesoporous carbon and an ionic liquid electrolyte [N-butyl-N-methylpyrrolidinium bis(trifluoromethane sulfonyl)imide, Pyr14TFSI] by means of an oxygen-bubbling device (OBD) and a peristaltic pump. The use of a non-flammable, non-volatile electrolyte ensures long-term, extensive discharging (up to 4.78 mAh cm−2), as well as operation at temperatures higher than room temperature.

LiMnPO4 is an attractive cathode material for the next-generation high power Li-ion batteries, due to its high theoretical specific capacity (170 mA h g(-1)) and working voltage (4.1 V vs Li+/Li). However, two main drawbacks prevent the practical use of LiMnPO4: its low electronic conductivity and the limited lithium diffusion rate, which are responsible for the poor rate capability of the cathode. The electronic resistance is usually lowered by coating the particles with carbon, while the use of nanosize particles can alleviate the issues associated with poor ionic conductivity. It is therefore of primary importance to develop a synthetic route to LiMnPO4 nanocrystals (NCs) with controlled size and coated with a highly conductive carbon layer. We report here an effective surface etching process (using LiPF6) on colloidally synthesized LiMnPO4 NCs that makes the NCs dispersible in the aqueous glucose solution used as carbon source for the carbon coating step. Also, it is likely that the improved exposure of the NC surface to glucose facilitates the formation of a conductive carbon layer that is in intimate contact with the inorganic core, resulting in a high electronic conductivity of the electrode, as observed by us. The carbon coated etched LiMnPO4-based electrode exhibited a specific capacity of 118 mA h g(-1) at 1C, with a stable cycling performance and a capacity retention of 92% after 120 cycles at different C-rates. The delivered capacities were higher than those of electrodes based on not etched carbon coated NCs, which never exceeded 30 mA h g(-1). The rate capability here reported for the carbon coated etched LiMnPO4 nanocrystals represents an important result, taking into account that in the electrode formulation 80% wt is made of the active material and the adopted charge protocol is based on reasonable fast charge times.

A binder-free graphene anode for Li-ion batteries showing a reversible specific capacity of ∼500 mA h g−1after 100 cycles is demonstrated.

Graphene showcases several key properties that can address emerging technological needs, in particular for the storage of energy in the ever-growing market of portable and wearable electronic devices.[1] The challenge is now to develop high quality graphene flakes in large volumes to ultimately suit the needs of an industrial-scale production.[2] Liquid-phase exfoliation (LPE) of graphite [3] is emerging as a promising tool for mass production of graphene flakes, which can be prepared in the form of inks.[4,5] In particular, graphene produced by LPE is being considered a promising material for anode in Li-ion battery.[6,7] Here we report the fabrication of graphene-based anodes by LPE of graphite in NMethyl2pyrrolidone (NMP). This method allows us to obtain graphene flakes with controlled morphological properties of single layer (SLG) and few layers (FLG) graphene flakes with lateral size of ~100nm (Fig a). A solvent exchange process is used to remove the NMP and re-disperse the flakes, at a higher concentration (5g/l), in ethanol. We then formed a graphene film by drop-casting the graphene flakes at ambient conditions on a copper foil, without any binder or conductive agents, typically used in conventional LIBs. The electrochemical tests of SLGand FLG-based anodes in a half-cell configuration demonstrate a reversible specific capacity of ~ 500 mAh g -1 after 100 cycles at a current density of 100 mA g -1 , with coulombic efficiency >99.5% (Fig b). More importantly, the as-produced SLGand FLG-based anode is assembled in a full-cell configuration with commercial LiNi0.5Mn1.5O4 (LNMO) as cathode. The full cell shows promising electrochemical results, such as very high flat-plateau voltage profile at 4.7 V and a reversible specific capacity of ~100 mAh gLNMO -1 . Hence, our work successfully achieved an advanced method for graphene based electrodes fabrication, with advantages of fast deposition, low cost and scalable production method. Our process opens the way to enhance the specific capacity, energy densities, lifetime and safety of LIBs, as well as minimize their cost and environmental impacts. References [1] F. Bonaccorso et al. Science 347 1246501, 2015 [2] F. Bonaccorso et al., Mater. Today 15, 564, 2012 [3] Y. Hernandez et al. Nat.Nano 9 563, 2008 [4] F. Torrisi et al. ACS Nano 4 2992, 2012 [5] A. Capasso et al. Solid State Comm. 224, 53, 2015 [6] J. Hassoun et al. Nano Lett. 14 4901, 2014 [7] H. Sun et al. J. Mater. Chem. A DOI:10.1039/c5ta08553e 2016

LiNi0.5Mn1.5O4 (LNMO) composite electrodes having the same formulation as to percentage of active material mass, binder and carbons, including reduced graphene oxide, were characterized in EC: DMC – 1M LiPF6 by cyclic voltammetry, charge/discharge cycles and impedance spectroscopy. The results demonstrate the beneficial effect on the electrode cycling stability in increasing C-rate to 1C, in limiting the charge voltage at 4.8 V and in covering the LNMO by partially reduced graphene oxide. The paper also discusses the evaluation of lithium diffusion coefficient in LNMO from cyclic voltammetry data in regard to the discrepancies reported in literature on this matter.

Carbon-doped TiO2-bronze nanowires were synthesized via a facile doping mechanism and were exploited as active material for Li-ion batteries. We demonstrate that both the wire geometry and the presence of carbon doping contribute to the high electrochemical performance of these materials. Direct carbon doping for example reduces the Li-ion diffusion length and improves the electrical conductivity of the wires, as demonstrated by cycling experiments, which evidenced remarkably higher capacities and superior rate capability over the undoped nanowires. The as-prepared carbon-doped nanowires, evaluated in lithium half-cells, exhibited lithium storage capacity of ∼306 mA h g(-1) (91% of the theoretical capacity) at the current rate of 0.1C as well as excellent discharge capacity of ∼160 mAh g(-1) even at the current rate of 10 C after 1000 charge/discharge cycles.

Low volatility, thermal and electrochemical stability and good conductivity of ionic liquids (ILs) make them “key electrolytes” for the development of Li/O2 batteries which are considered the most promising high-energy systems for a market success of electric vehicles of long driving range. Particularly, hydrophobic pyrrolidinium salts of bis(trifluoromethanesulfonyl)imide feature a high stability toward superoxide that is formed during the discharge/recharge of Li/O2 batteries. Under the European LABOHR Project, the oxygen redox reaction (ORR) and O2 diffusion coefficient and solubility, which are crucial parameters for Li/O2 battery operation, have been investigated in such ILs and related to the physical-chemistry properties of the electrolytes. It has also been demonstrated that ILs provide a real possibility for the development of rechargeable Li/O2 batteries that can safely operate even above room temperature. The main achievements of this study are here reported and discussed Acknowledgement Work funded by the European Commission in the 7th Framework Programme FP7-2010-GC-ELECTROCHEMICAL STORAGE, under contract no. 265971 “Lithium-Air Batteries with split Oxygen Harvesting and Redox processes” (LABOHR). All the partners of the LABOHR Project are acknowledged for the fruitful discussions on Li/O2 batteries with ionic liquids. References [1] www.labohr.eu [2] S. Monaco, A. M. Arangio, F. Soavi, M. Mastragostino, E. Paillard, S. Passerini, Electrochimica Acta 83 (2012) 94–104. [3] F. Soavi, S. Monaco, M. Mastragostino, Journal of Power Sources 224 (2013) 115 – 119. [4] S. Monaco, F. Soavi, M. Mastragostino, J. Phys. Chem. Lett. 4 (2013) 1379−1382.

In this work, the electrochemical stability and lithium plating/stripping performance of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) are reported, by investigating the behavior of Li metal electrodes in symmetrical Li/electrolyte/Li cells. Electrochemical impedance spectroscopy measurements and galvanostatic cycling at different temperatures are performed to analyze the influence of temperature on the stabilization of the solid electrolyte interphase (SEI), showing that TFSI-based ionic liquids (ILs) rank among the best candidates for long-lasting Li–air cells.

In the last few years, much research effort is being focused on rechargeable lithium–air (O2) batteries which feature a theoretical specific energy comparable to that of gasoline. While these cutting-edge batteries are at their early stage of development with many challenges to be overcome, they are the most promising candidates to power electric vehicles with long driving range. In the frame of the European LABOHR Project we are investigating the use of hydrophobic ionic liquid (IL)-based electrolytes in these batteries. Basic studies of the oxygen redox reaction in N-butyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide at home-made catalyst-free porous carbon electrode demonstrated that O2mass transport in IL becomes crucial at the fastest battery discharge rates, which are of interest for automotive applications. The study also demonstrated that it is possible to overcome this limitation by new flow-cell designs, and the main achievements are reported and discussed. Acknowledgement Work funded by the European Commission in the 7th Framework Programme FP7-2010-GC-ELECTROCHEMICAL STORAGE, under contract no. 265971 “Lithium-Air Batteries with split Oxygen Harvesting and Redox processes” (LABOHR). All the partners of the LABOHR Project are acknowledged for the fruitful discussions on Li/O2 batteries with ionic liquids. References [1] www.labohr.eu [2] S. Monaco, A. M. Arangio, F. Soavi, M. Mastragostino, E. Paillard, S. Passerini, Electrochimica Acta 83 (2012) 94–104. [3] F. Soavi, S. Monaco, M. Mastragostino, Journal of Power Sources 224 (2013) 115 – 119. [4] S. Monaco, F. Soavi, M. Mastragostino, J. Phys. Chem. Lett. 4 (2013) 1379−1382.

The use of ionic liquid (IL)-based electrolytes and porous carbonaceous cathodes is today one of the most promising strategies for the development of rechargeable Li/O2 batteries. Enhancing Li/O2 battery cyclability at high discharge rate is a key issue for automotive applications. O2 reduction at a meso-macroporous carbon electrode in N-butyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI):LiTFSI 9:1 is here investigated. The study demonstrates that oxygen electrode response in IL at high discharge currents is dominated by O2 mass transport in IL. A novel configuration of flow-Li/O2 battery that operates at high discharge rate is reported.

Li/O-2 batteries are a breakthrough in battery technology for powering long-range electric vehicles. The viability of high efficiency, rechargeable Li/O-2 battery is demonstrated by the use of catalyst-free mesomacroporous carbon cathode and N-butyl-N-methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid-based electrolyte. The carbon electrode, obtained by a simple, low-cost template method, features a high specific capacity of 2500 mAh g(-1) at 2.6 V vs. Li+/Li and, more importantly, a recharge potential lower than 3.8 V vs Li+/Li that prevents secondary reactions in the ionic liquid detrimental for battery rechargeability and makes it possible to reach a recharge efficiency of 90%. (C) 2012 Elsevier B.V. All rights reserved.