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The local structural and electronical transformations occurring along the first charge and discharge cycle of Li- and Mn-rich Li[Li0.2Ni0.16Mn0.56Co0.08]O2 cathode material have been characterized by X-ray absorption spectroscopy at several complementary edges. The irreversible spinel formation, occurring at the expenses of the cycling layered phase during the first charge, is quantified (about 10%) and spatially localized. The local strains induced by the Ni oxidation have been evaluated. They induce the formation of a low spin Mn3+ in the layered structure in parallel to the irreversible formation of the spinel phase in the particles bulk. The charge balance has been quantified for all the elements along the first charging cycle, confirming a reversible oxygen oxidation along the charge. Overall, these quantitative results provide an experimental basis for modeling aimed to control the structure and its evolution, for instance, hindering the spinel formation for the benefit of the material cycle life., This research was supported by the Spanish Government, through the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURE CEX2019-000917-S), and the projects MAT2017-91404-EXP, RTI2018-096273-B-I00, and RTI2018-097753-B-I00 with FEDER cofunding. D.T. participates in the FLOWBAT 2021 platforms promoted by the Spanish National Research Council (CSIC). The HIU authors acknowledge the basic funding from the Helmholtz Association.

Energy-dependent full field transmission soft X-ray microscopy (TXM) is able to give a full picture at the nanometer scale of the chemical state and spatial distribution of oxygen and other elements relevant for battery materials, providing pixel-by-pixel absorption spectrum. We show different methods to localize chemical inhomogeneities in Li1.2Mn0.56Ni0.16Co0.08O2 particles with and without VOx coating extracted from electrodes at different states of charge. Considering the 3d(Mn,Ni)-2p(O) hybridization, it has been possible to discriminate the chemical state of Mn and Ni in addition to the one of O. Different oxidation states correspond to specific features in the O-K spectra. To localize sample regions with specific compositions we apply two different methods. In the first, the pixel-by-pixel ratios of images collected at different key energies clearly highlight local inhomogeneities. In the second, introduced here for the first time, we directly correlate corresponding pixels of the two images on a xy scatter plot that we call phase map, where we can visualize the distributions as function of thickness as well as absorption artifacts. We can select groups of pixels, and then map regions with similar spectral features. Core-shell distributions of composition are clearly shown in these samples. The coating appears in part to frustrate some of the usual chemical evolution. In addition, we could directly observe several further aspects, such as: distribution of conducting carbon; inhomogeneous state of charge within the electrode; molecular oxygen profiles within a particle. The latter suggests a surface loss with respect to the bulk but an accumulation layer at intermediate depth that could be assigned to retained O2., This research was funded by Spanish Government, through the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURE CEX2019-000917-S), and the projects MAT2017-91404-EXP, RTI2018-096273-B-I00 and RTI2018-097753-B-I00 with FEDER cofunding. D.T. participates in the FLOWBAT 2021 platforms promoted by the Spanish National Research Council (CSIC). The HIU authors acknowledge the basic funding from the Helmholtz Association.

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 1000 mA g−1, respectively. The Si@V2O5 electrode also shows remarkable rate capability performance.

Even though electrochemically inactive, the binding agent in lithium-ion electrodes substantially contributes to the performance metrics such as the achievable capacity, rate capability, and cycling stability. Herein, we present an in-depth comparative analysis of three different aqueous binding agents, allowing for the replacement of the toxic N-methyl-2-pyrrolidone as the processing solvent, for high-energy Li1.2Ni0.16Mn0.56Co0.08O2 (Li-rich NMC or LR-NMC) as a potential next-generation cathode material. The impact of the binding agents, sodium carboxymethyl cellulose, sodium alginate, and commercial TRD202A (TRD), and the related chemical reactions occurring during the electrode coating process on the electrode morphology and cycling performance is investigated. In particular, the role of phosphoric acid in avoiding the aluminum current collector corrosion and stabilizing the LR-NMC/electrolyte interface as well as its chemical interaction with the binder is investigated, providing an explanation for the observed differences in the electrochemical performance.

A tin-decorated reduced graphene oxide, originally developed for lithium-ion batteries, has been investigated as an anode in sodium-ion batteries. The composite has been synthetized through microwave reduction of poly acrylic acid functionalized graphene oxide and a tin oxide organic precursor. The final product morphology reveals a composite in which Sn and SnO2 nanoparticles are homogenously distributed into the reduced graphene oxide matrix. The XRD confirms the initial simultaneous presence of Sn and SnO2 particles. SnRGO electrodes, prepared using Super-P carbon as conducting additive and Pattex PL50 as aqueous binder, were investigated in a sodium metal cell. The Sn-RGO showed a high irreversible first cycle capacity: only 52% of the first cycle discharge capacity was recovered in the following charge cycle. After three cycles, a stable SEI layer was developed and the cell began to work reversibly: the practical reversible capability of the material was 170 mA&middot, h&middot, g&minus, 1. Subsequently, a material of formula NaLi0.2Ni0.25Mn0.75O was synthesized by solid-state chemistry. It was found that the cathode showed a high degree of crystallization with hexagonal P2-structure, space group P63/mmc. The material was electrochemically characterized in sodium cell: the discharge-specific capacity increased with cycling, reaching at the end of the fifth cycle a capacity of 82 mA&middot, 1. After testing as a secondary cathode in a sodium metal cell, NaLi0.2Ni0.25Mn0.75O was coupled with SnRGO anode to form a sodium-ion cell. The electrochemical characterization allowed confirmation that the battery was able to reversibly cycle sodium ions. The cell&rsquo, s power response was evaluated by discharging the SIB at different rates. At the lower discharge rate, the anode capacity approached the rated value (170 mA&middot, 1). By increasing the discharge current, the capacity decreased but the decline was not so pronounced: the anode discharged about 80% of the rated capacity at 1 C rate and more than 50% at 5 C rate.

This study reports the investigation of several compounds as electrolyte additives for Li[Li0.2Mn0.56 Ni0.16 Co0.08]O2 (a.k.a lithium rich NMC) cathode material. Among the compounds investigated via electrochemical and ex-situ analytical techniques, i.e. XRD, XPS and RAMAN spectroscopy, only 1,3-propane sultone and tris(trimethylsilyl) borate show a beneficial effect on the capacity retention and coulombic efficiency of the layered cathode. The results suggest that the improved capacity retention of the cells containing the two above-mentioned additives mainly originates from their participation in the formation of the cathode passive layer, which prevents the dissolution of the metals from the cathode material. Additionally, the borate additive reduces the lithium consumption upon the passive layer formation thus leaving a higher amount of lithium available in the electrolyte. Graphite/Li[Li0.2Mn0.56 Ni0.16 Co0.08]O2 cells containing the borate additive in the electrolyte showed 85% capacity retention after 485 cycles, confirming the feasibility of its employment for practical applications.

Lithium-rich transition-metal-oxide cathodes are among the most promising materials for next generation lithium-ion-batteries because they operate at high voltages and deliver high capacities. However, their cycle-life remains limited, and individual roles of the transition-metals are still not fully understood. Using bulk-sensitive X-ray absorption and emission spectroscopy on Li[Li0.2Ni0.16Mn0.56Co0.08]O2, we inspect the behavior of Mn, generally considered inert upon the electrochemical process. During the first charge Mn appears to be redox-active showing a partial transformation from high-spin Mn4+ to Mn3+ in both high and low spin configurations, where the latter is expected to favor reversible cycling. The Mn redox-state with cycling continues changing in opposition to the expected charge compensation and is correlated with Ni oxidation/reduction, also spatially. The findings suggest that strain induced on the Mn−O sublattice by Ni oxidation triggers Mn reduction. These results unravel the Mn role in controlling the electrochemistry of Li-rich cathodes., This work has been partially financed by the Spanish Ministry of Economy and Competitiveness, through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015- 0496). The HIU authors kindly acknowledge the basic funding of the Helmholtz Association.

The EU-funded collaborative MARS-EV Project (FP7, grant agreement 609201) has been targeting inter alia the realization of aqueous electrode processing technologies for high-energy lithium-ion positive electrodes with a particular focus on achieving the high recycling requirements established by the European Commission in its Battery Directive 2006/66 EG, stipulating a minimum recycling rate of 50%. Indeed, the aqueous electrode fabrication does not only allow for avoiding the use of environmentally hazardous, toxic, and expensive organic solvents as well as the need for super-dry conditions up to the cell assembly, but moreover a facilitated recycling process due to the water-soluble binding agents. Additionally, of great importance with regard to the latter is the careful selection of the cathode chemistry – not least with respect to economic aspects. Herein, we summarize the results and progresses obtained within MARS-EV, highlighting their importance for the realization of environmentally friendly lithium-ion batteries for a sustainably electrified transportation.

A graphene-based composite containing Sn and Sb is synthesized and characterized. Structural and morphological characterizations demonstrate the achievement of multilayer graphene with anchored SnSb nanoparticles. The composite is tested as active material for lithium-ion battery anodes and, as a result of the use of poly acrylic acid binder and vinylene carbonate electrolyte additive, remarkable electrochemical performance are achieved in terms of stable cycling stability and specific gravimetric capacity (468 mAh g−1 after 75 cycles with a capacity retention of about 80%). Moreover, impedance spectroscopy analysis further demonstrates the enhanced stability obtained by using, together with vinylene carbonate electrolyte additive, poly acrylic acid binder instead of poly vinylidene difluoride.

A comparative investigation on binder induced chemical and morphological evolution of Li4Ti5O12 electrodes was performed via X-ray photoemission spectroscopy, scanning electron microscopy, and electrochemical measurements. Composite electrodes were obtained using three different binders (PAA, PVdF, and CMC) with 80:10:10 ratio of active material:carbon:binder. The electrochemical performances of the electrodes, were found to be intimately correlated with the evolution of the microstructure of the electrodes, probed by XPS and SEM analysis. Our analysis shows that the surface chemistry, thickness of the passivation layers and the morphology of the electrodes are strongly dependent on the type of binders that significantly influence the electrochemical properties of the electrodes. These results point to a key role played by binders in optimization of the battery performance and improve our understanding of the previously observed and unexplained electrochemical properties of these electrodes.

The electrochemical behavior of a composite anode based on tin oxide nanoparticles embedded in electrically conductive graphene matrix is reported. The composite has been synthetized through microwave reduction of poly acrylic acid functionalized graphene oxide and a tin oxide organic precursor both dispersed in ethylene glycol. The poly acrylic functionalization of graphene oxide partially prevent the re-stacking of the graphene layers. In addition, poly acrylic acid acts as a surfactant favoring an optimized dispersion of the metal and, after thermal decomposition, contributes in creating a carbon layer for an improved conductivity. The final product morphology reveals a composite in which SnO 2 nanoparticles are homogenously distributed into the reduced graphene oxide matrix. Graphene/SnO 2 nanocomposite electrodes, prepared using Super-P carbon as conducting additive and polyvinylidenedifluoride as binder, exhibit high rate capability and cycle life during galvanostatic charge/discharge tests. After more than 140 cycles, mostly performed at 500 mA g −1 , the electrodes show a remarkable stable specific capacity of about 430 mAh g −1 with a Coulombic efficiency close to 100%.The morphological stability of the electrode is also confirmed by impedance spectroscopy analysis, which shows solid-electrolyte interphase related resistance values constant up to 100 cycles.

The poor electrochemical performance of Li-ion batteries at low temperature is one of the major technical barriers to their practical application as energy sources. Here we report an attempt to improve the low-temperature electrochemical behavior of Li4Ti5O12 (LTO) anodes by replacing pristine Super-P with a Cu/Super-P composite in the electrodes composition. The composite, consisting of copper nanoparticles supported on Super-P carbon (Cu/Super-P), has been synthesized via a fast one-pot microwave-assisted polyol procedure. The comparison between the electrochemical performances of electrodes manufactured with pristine Super-P and of those that used the Cu/Super-P shows that the synthesized composite is indeed effective in enhancing the low-temperature electrochemical behavior of LTO anodes. Galvanostatic cycling demonstrates that much higher capacities are obtained within the investigated temperature range (from 20 to −30 °C), regardless of the applied C-rate. Furthermore, the study of the differential capacity plots clearly shows that lower polarization is achieved when the Cu/Super-P composite replaces pristine Super-P.

This work reports the synthesis and characterization of an amorphous V2O5 cryogel/graphene nanosheet composite as a high-performance cathode material. The optimization of electrode processing is conducted by using the environmentally friendly poly acrylic acid as the binder and ethanol as the solvent. The nanocomposite material shows outstanding capacity values, exceeding 300 mAhg−1 reversible capacity upon galvanostatic cycling tests at 280 mAg−1 (C/2 charge/discharge rate), and more than 100 mAhg−1 at 5600 mAg−1 (10C). A subsequent electrochemical impedance spectroscopy study gives useful insights into the cathode/electrolyte interface.

This paper describes the preparation and characterization of a high-voltage lithium-ion battery based on Sn-decorated reduced graphene oxide and LiNi0.5Mn1.5O4 as the anode and cathode active materials, respectively. The Sn-decorated reduced graphene oxide is prepared using a microwave-assisted hydrothermal synthesis method followed by reduction at high temperature of a mixture of (C6H5)2SnCl2 and graphene oxide. The so-obtained anode material is characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and electron diffraction spectroscopy. The LiNi0.5Mn1.5O4 is a commercially available product. The two materials are used to prepare composite electrodes, and their electrochemical properties are investigated by galvanostatic charge/discharge cycles at various current densities in lithium cells. The electrodes are then used to assemble a high-voltage lithium-ion cell, and the cell is tested to evaluate its performance as a function of discharge rate and cycle number. © 2015, Springer-Verlag Berlin Heidelberg.

International audience; Herein, we present the upscaled synthesis of nanoparticulate Li4Ti5O12 (LTO) by means of flame spray pyrolysis (FSP), yielding high phase purity and appropriate morphology for application as high-power lithium-ion anode material. Electrodes based on this optimized LTO nanopowder, carboxymethyl cellulose (CMC) as binder, and copper as current collector revealed excellent rate performance, providing specific capacities of 133, 131, 129, 127, 124, and 115 mAh g(-1) when applying C rates of 1C, 2C, 5C, 10C, 20C, and 50C, respectively. Targeting the commercial application of thus synthesized nanoparticles, we optimized also the electrode composition, comparing three different binding agents (CMC, PVdF, and poly(acrylic acid), PAA) and substituting the copper current collector by aluminum. The results of this comparative analysis show, that the combination of nanoparticulate LTO, CMC, and an aluminum current collector appears most suitable toward the realization of environmentally friendly and cost-efficient lithium-ion anodes, presenting very stable cycling performance for more than 1000 cycles at 10C without substantial capacity decay. (C) The Author(s) 2015. Published by ECS. 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.

In order to increase the energy density of lithium-ion batteries, novel cathode materials have attracted much attention due to their high operating voltage [1]. However, their practical application is still limited due to the poor stability of the cathode / alkyl carbonate-based electrolyte interface. In fact, the working potential of many high voltage cathode is beyond the electrochemical stability window of the conventional carbonate-based electrolytes (< 4.3 V vs. Li+/Li), thus leading to the electrolyte oxidative decomposition [2]. This phenomenon, besides reducing the energy stored in the cell, might even results in the formation of decomposition products (e.g., HF) leading to metal dissolution, and hence material capacity fading. Many strategies, such as the use of alternative electrolyte system or the coating of the material, have been proposed in order to enable the use of high-voltage cathodes [3]. However, using electrolyte additives is one of the most efficient and economic strategy for alleviating the undesired reactions among cathode and electrolyte [4]. In fact, electrolyte additives can be sacrificially decomposed to form a protective layer on cathode surface, thus avoiding further electrolyte decomposition reactions. In addition, electrolyte additives can even scavenge water or other impurities and/or stabilize the lithium salt, extending therefore the cycle life of the high-voltage cathodes. In this study, the investigation of additives’ effects in enhancing the cathode cycling stability and efficiency will be presented via a combination of electrochemical techniques, such as impedance spectroscopy and ex-situ analytical techniques, i.e. XRD, XPS and RAMAN. The feasibility of the electrolyte additives employment for practical application will be demonstrated showing full-cell studies with graphite as anode. [1] A. Kraytsberg, Y. Ein-Eli, Advanced Energy Materials, 2 (2012) 922-939. [2] S. Tan, Y.J. Ji, Z.R. Zhang, Y. Yang, ChemPhysChem, 15 (2014) 1956-1969. [3] N.-S. Choi, J.-G. Han, S.-Y. Ha, I. Park, C.-K. Back, RSC Advances, 5 (2015) 2732-2748. [4] S.S. Zhang, J. Power Sources, 162 (2006) 1379-1394.