On the relevance of the polar β-phase of poly(vinylidene fluoride) for high performance lithium-Ion battery separators

Separator membranes based on poly(vinylidene fluoride), PVDF, poly(vinylidene fluoride-co-trifluoroethylene), PVDF-TrFE, poly(vinylidene fluoride-co-hexafluropropylene), PVDF-HFP and poly(vinylidene fluoride-co-chlorotrifluoroethylene), PVDF-CTFE were prepared by solvent casting method using N,N-dimethylformamide (DMF) as solvent. In all cases, the same polymer/solvent ratio and solvent evaporation temperature were used. For all membranes, porous microstructure is achieved with a degree of porosity larger than 50%. The β-phase content as well as degree of crystallinity were different for each membrane, which were lower for the co-polymer membranes when compared with PVDF. On the other hand, the observed ionic conductivity values, electrolyte uptake, tortuosity and MacMullin number were similar for all membranes. The electrochemical performance of the separator membranes was evaluated in Li/C–LiFePO4 half-cell configuration showing good cyclability and rate capability for all membranes. Among the all separator membranes, PVDF-TrFE demonstrate the best electrochemical performance, with a discharge capacity value of 87 mAh.g-1 after 50 cycles with a capacity retention of 78 % at 2C.Finally, the correlation between the β-phase content in the membranes and the cycling performance was demonstrated (which was significant at high-C rates): larger β-phase contents, leading higher polarity, facilitates faster lithium ion migration within the separator for similar microstructures.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the projects PTDC/CTM-ENE/5387/2014 and UID/CTM/50025/2013 and grants SFRH/BD/90215/2012 (J.C.D.) and SFRH/BPD/112547/2015 (C.M.C.). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support) and from the Basque Government Industry Department under the ELKARTEK Program. Authors are grateful to the Government of the Basque Country for financial support (Grupos de Investigación, IT718-13). The authors thank Solvay, Timcal and Phostech for kindly supplying the high quality materials.info:eu-repo/semantics/publishedVersio

Co(OH)2@MnO2 nanosheet arrays as hybrid binder-free electrodes for high-performance lithium-ion batteries and supercapacitors

Co(OH)2@MnO2 nanosheet arrays were directly grown on nickel foam via two-step electrodeposition method with subsequent heat treatment at 170 °C. The hybrid electrode, where the electrodeposited Co(OH)2 and MnO2 nanosheets were inlayed with each other, was formed and employed as a binder-free anode material for a lithium-ion battery (LIB) and as an electrode for a supercapacitor (SC). For both applications, LIB and SC, the Co(OH)2@MnO2 nanosheet electrode exhibited appreciable cycling stability with high specific capacity as well as specific capacitance and rate capability. The excellent electrochemical performances of this hybrid nanosheet electrode were probably ascribed to their unique 3D architecture, which provides large active sites for efficient electrochemical reactions and the synergistic effects of the two active materials. The electrodeposition method appears to be suitable for the fabrication of binder-free, nanostructured, hybrid arrays, and as demonstrated here, the Co(OH)2@MnO2 nanosheet could potentially be used as a high-performance LIB and SC electrode material

Lithium antimonite: A new class of anode material for lithium-ion battery

LiSbO(3) has been synthesized by chemical mixing followed by thermal treatment at 800 degrees C. Field emission scanning electron microscopy revealed bar shaped Multifaceted grains, 0.5-4 mu m long and 0.5-1 mu m wide, that cluster together as soft agglomeration. 2032 type coin cell vs Li/Li(+) shows a flat charge-discharge plateau together with low Li intercalation/de-intercalation potential (0.2/0.5 V). A high discharge capacity of 580 mA h g(-1) has been obtained in the 1st cycle with 100% Coulombic efficiency. About 96% of the Coulombic efficiency is retained up to the 12th cycle, but at the 1501 cycle, the Coulombic efficiency drops down to 88%. AC impedance spectroscopy shows an increase in electrolyte resistance (R(s)) from 4.43 Ohm after the initial cycle to 12.4 Ohm after the 15th cycle indicating a probable dissolution of Sb into the electrolyte causing the capacity fading observed. (c) 2009 Elsevier B.V. All rights reserved

Lithium hexaoxo antimonate as an anode for lithium-ion battery

The aims of this study were to synthesize lithium hexaoxo antimonate (Li7SbO6) by a solid-state method with thermal treatment at 700°C in a stream of dry oxygen and to investigate its electrochemical properties as an anode in lithium-ion coin cells. X-ray powder diffraction analyses confirm a rhombohedral crystal structure with lattice parameters of a = b = 0·5411 nm and c = 1·5030 nm. Li7SbO6 is electrochemically active with lithium intercalation and deintercalation potentials of ≈0·8 and ≈1·0 V against Li/Li+, respectively. While the initial reversible capacity is low (66 mA h g−1 at 0·05 mA cm−2), an excellent rate performance with no significant fading has been observed up to 100 continuous cycles. Even at very high rates of 5 mA cm−2 (37 C) and 10 mA cm−2 (106 C), 51% and 48% of capacity is retained, with nearly 100% Coulombic efficiency demonstrating the potential of this material for high-rate applications

LiSb3O8 as a prospective anode material for lithium-ion battery

Electrochemical properties of LiSb3O8 were investigated as an anode in lithium-ion coin cells. Li insertion in this material occurs in a single step at 0.75 V vs Li/Li+, but the corresponding Li extraction takes place in two successive stages at 1.12 and 1.4 V. Reversible capacities of 305 and 297 mAh/g could be obtained at 0.1 and 0.2 mA/cm2, respectively, up to 50 cycles

Hematite microdisks as an alternative anode material for lithium-ion batteries

In this work, hematite microdisks (500 nm to 1 μm in diameter, ∼200 nm in thickness) have been synthesized by a facile hydrothermal method which exhibited good cycling stability at a current density of 200 mA g−1 and 1000 mA g−1, and excellent rate performance at various current densities ranging from 100 mA g−1 to 4000 mA g−1.acceptedVersio

Nanomaterials for Electrochemical Energy Conversion and Storage Technologies

In this modern era, our society faces a serious energy crisis due to increasing human population. Energy consumption starts from small-scale electronic gadgets to high power consuming electric vehicles. To supply power on demand, researchers focus on alternative renewable energy resources including solar energy, wind energy, hydropower, geothermal energy, and bioenergy. Effectively, energy conversion and storage technologies such as solar cells, fuel cells, secondary batteries, supercapacitors, and other self-powered systems are under rigorous investigation. The efficient energy conversion and storage performance of those technologies rely on material properties of their electrode, electrolyte, and other device components. It is recently known that nanostructuring of device components leads to enhanced efficiency in terms of robustness and reliability of the energy conversion and storage systems. Moreover, the nanostructured materials have attracted great interest due to their unique physicochemical and electrochemical properties. Hence, the utilization of such materials in nanodimensions will create enormous impact on the efficiency of various energy conversion and storage devices. The main objective of this special issues is to identify the significant research paradigms of nanomaterials and their potential impacts on applications. In particular, focus of this issue is on the synthesis and characterization of nanostructured materials for various applications such as supercapacitors, batteries, photoelectrochemical, and thermal enhancement systems. The highlights of the published articles are summarized as follows. In this special issue, Y. Yuan et al. synthesized the porous activated carbon materials from Pleurotus eryngii-based biomass material via carbonization, followed by KOH activation and utilized it for supercapacitor applications. The as-prepared activated carbon presented a large specific area with high porosity which exhibited a maximum specific capacitance of 195 F g-1 with 93% capacitance retention after 15000 cycles. It is known that Pleurotus eryngii is one of the readily available sources of carbon materials, potentially suitable for supercapacitor applications. Also, this biomass can be the resource for development of porous activated carbon for other energy conversion and storage devices in the future. Further, B.-X. Zou et al. synthesized hierarchical porous N, O-doped carbon composites by combining low molecular weight phenol resin and silk fibers in various combinations using a hydrothermal method and carbonization process. The as-prepared electroactive materials showed a low resistance and good surface area with hierarchical porosity. The low molecular phenol resin and silk fiber combination increases the surface area and enhanced the electron transport within the active materials. The fabricated symmetric device delivered a maximum energy density of 7.4 Wh kg-1 and power density of 90.1 W kg−1 using aqueous electrolyte