Mn dissolution is the main drawback of LiMn2O4 cathodes, leading to capacity fading and anode poisoning. It is well known that improved capacity/cycling performances have been obtained by the Al2O3...

It is well known that the Al2O3 coating of the LiMn2O4 cathodes leads to improvement of the performance of these electrodes. However, the effect of the coating on the fundamental processes occurring on the interface with the active material which results in the formation of the solid permeable interphase is yet to be investigated. These effects should be more pronounced in the first cycle when a dynamic interaction of the active material at high voltage with the electrolyte and binder leads to the formation of this passivation layer. Here, we present a detailed investigation of the solid permeable interphase formation in alumina-coated and uncoated LiMn2O4 electrodes using X-ray absorption spectroscopy and analysis on the electrodes at the predesigned charging/discharging states. We demonstrate that the alumina coating leads to modification of the solid permeable layer and its dynamics. We also discuss the possible influences of interface modifications via coating on the battery performance.

Spinel metal oxide nanoparticles are promising alternative anode materials for Li-ion batteries showing enhanced cycling performances and specific theoretical capacity resulting from a combination of alloying and conversion reactions during dis-/charge. In this work, we study the effect of the initial lithium insertion into carbon-coated ZnFe2O4 anodes by X-ray absorption spectroscopy. We are able to closely monitor the structural changes and the electronic structure in-situ and in-operando. For low lithium uptake (up to 0.3 Li+ per formula unit) the initial crystalline structure is not significantly modified. Further lithium insertion causes the migration of Zn atoms from tetrahedral 8a sites into vacant octahedral 16c sites, and Fe is gradually reduced from Fe3+ to Fe2+ upon lithium insertion. In the early stage of lithiation (up to 2 Li+ per formula unit) we find no evidence of Zn reduction. Also, a gradual damping of EXAFS signals, linked to the increasing structural disorder, is observed.

Fe3O4 nanoparticles synthesized by a base catalyzed method are tested in an All-Solid-State (ASLB) battery using a sulfide electrolyte. The pristine nanoparticles were morphologically characterized showing an average size of 12 nm. The evaluation of the electrochemical properties shows high specific capacity values of 506 mAhg(-1) after 350 cycles at a specific current of 250 mAg(-1), with very high stability and coulombic efficiency. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.

The preparation and the structural, morphological and electrochemical characterization of a Silicon/V2O5 nanosheets composite (Si@V2O5), as an active anode material for Li-ion batteries, are here reported. The nanocomposite material, aimed at mitigating the morphological instability issues commonly plaguing Si-based anodes, is prepared by a H2O2-based low-impact synthesis, while the electrode processing involves the use of Polyacrylic Acid (PAA) binder. The electrolyte formulation is optimized as well, by employing Vinylene Carbonate (VC) additive, in order to maximize cycling stability and performance. Preliminary results report specific capacities of 932 mAhg(-1) and 759 mAhg(-1) after 50 cycles at 500 mA g(-1) and 1000mA g(-1), respectively. The Si@V2O5 electrode also shows remarkable rate capability performance. (c) 2018 Elsevier Ltd. All rights reserved.

The article deals with the optimization of an anode based on commercial manganese oxide. Several parameters are considered in order to enhance capacity, rate capability and long-term cycleability. Particularly, Polyacrylic Acid as a green binder with enhanced mechanical features is proposed, while Vinylen Carbonate is added to a standard carbonate-based electrolyte system in order to enhance the stability of passivation layer and of electrode/electrolyte interface. The role of a reversible “gel-like” layer toward interfacial stability is investigated as well. Several structural, morphological and electrochemical investigation techniques are applied in order to fully characterize the behavior of baseline and modified electrodes and cells. This process results in an optimized system able to deliver, in a half-cell vs. metal Li, specific capacity values up to 725mAhg−1 at 1C-rate, stable for 100 cycles, and relevant rate capability, confirming a major influence of electrode and electrolyte formulation toward electrochemical performance.

Pristine LiMn2O4, synthetized by solid-state route, is coated by an Al2O3 layer through co-precipitation method, in order to enhance the electrochemical performances and stability of the cathode, especially at high temperatures. Structural analysis by X-ray diffraction and morphological characterization by scanning and transmission electron spectroscopy reveal phase pure and crystalized nanomaterial forming clusters. The cycling performances of pristine and modified materials are investigated by galvanostatic cycles at several charge/discharge rates. A detailed analysis of the interfacial properties, and of their impact toward cycling behavior, is carried out by combining galvanostatic cycles at 1C and electrochemical impedance spectroscopy at T = 25 degrees C and T = 50 degrees C. The results show that the electrode/electrolyte interface of Al2O3-modified LiMn2O4 is stabilized by suppressing Mn dissolution, resulting in improved cycleability, especially at high temperatures. These results are corroborated by X-ray photoelectron spectroscopy studies, which confirm the suppression of Mn dissolution for the Al2O3-coated material. (c) 2017 Elsevier Ltd. All rights reserved.

Fe3O4 nanoparticles synthesized by a base catalyzed method are tested as anode material for Li-ion batteries. The pristine nanoparticles are morphologically characterized showing an average size of 11 nm. Electrodes are prepared using high-molecular weight Poly (acrylic acid) as improved binder and ethanol as low cost and environmentally friendly solvent. The evaluation of electrochemical properties shows high specific capacity values of 857 mA hg(-1) after 200 cycles at a specific current of 462 mAg(-1), as well as an excellent rate capability with specific current values up to 18480 mAg(-1). To the best of our knowledge, this is the first report of Fe3O4 nanoparticles cycling with PAA as binder. (C) 2016 Elsevier B.V. All rights reserved.

A graphene/silicon nanocomposite has been synthesized, characterized and tested as anode active material for lithium-ion batteries. A morphologically stable composite has been obtained by dispersing silicon nanoparticles in graphene oxide, previously functionalized with low-molecular weight polyacrylic acid, in eco-friendly, low-cost solvent such as ethylene glycol. The use of functionalized graphene oxide as substrate for the dispersion avoids the aggregation of silicon particles during the synthesis and decreases the detrimental effect of graphene layers re-stacking. Microwave irradiation of the suspension, inducing reduction of graphene oxide, and the following thermal annealing of the solid powder obtained by filtration, yield a graphene/silicon composite material with optimized morphology and properties.Composite anodes, prepared with high-molecular weight polyacrylic acid as green binder, exhibited high and stable reversible capacity values, of the order of 1000 mAh g(-1), when cycled using vinylene carbonate as electrolyte additive. After 100 cycles at a current of 500 mA g(-1), the anode showed a discharge capacity retention of about 80%. The mechanism of reversible lithium uptake is described in terms of Li-Si alloying/dealloying reaction. Comparison of the impedance responses of cells tested in electrolytes with or without vinylene carbonate confirms the beneficial effects of the additive in stabilizing the composite anode. (C) 2014 Elsevier B.V. All rights reserved.