Matteo Destro

Aqueous processing of cellulose based paper-anodes for flexible Li-ion batteries

Cellulose fibers were used as novel bio-sourced binder to manufacture flexible cellulose/graphite paper-anodes for Li-ion batteries by means of a simple water-based filtration process easily up-scalable capitalizing conventional papermaking technologies. Paper-anodes showed excellent tensile properties with Young moduli ranging between 60 and 450 MPa, discharge capacity values up to 300/350 mA h g-1 and cycling performances comparable with conventional polymer-bonded graphite anodes.

Flexible cellulose/LiFePO4 paper-cathodes: toward eco-friendly all-paper Li-ion batteries

Today most of commercial Li-ion batteries (LIBs) are manufactured using toxic solvents and synthetic polymer binders. In order to lower the cost and the environmental impact of LIBs an effort must be made to identify low-cost and environmentally friendly materials and processes. In this work, flexible, self-standing and easily recyclable LiFePO4 cathodes are obtained using cellulose fibers as biosourced binder and a quick, aqueous filtration process, easily upscalable capitalizing the well-established papermaking know-how. The obtained paper-cathodes show very good mechanical properties, with Young’s modulus as high as 100 MPa, discharge capacity values up to 110 mAh g−1 and very good cycling performances, comparable with conventional polymer-bonded LiFePO4 cathodes. Moreover, a complete paper-cell, constituted by a paper-cathode, a paper-separator and a paper-anode is presented, showing good cycling performances in terms of specific capacity, efficiency and stability.

Unveiling the controversial mechanism of reversible Na storage in TiO2 nanotube arrays: Amorphous versus anatase TiO2

Due to their inherent safety, low cost, and structural stability, TiO2 nanostructures represent a suitable choice as anode materials in sodium-ion batteries. In the recent years, various hypotheses have been proposed regarding the actual mechanism of the reversible insertion of sodium ions in the TiO2 structure, and previous reports are often controversial in this respect. Interestingly, when tested as binder- and conducting additive-free electrodes in laboratory-scale sodium cells, amorphous and crystalline (anatase) TiO2 nanotubular arrays obtained by simple anodic oxidation exhibit peculiar and intrinsically different electrochemical responses. In particular, after the initial electrochemical activation, anatase TiO2 shows excellent rate capability and very stable long-term cycling performance with larger specific capacities, and thus a clearly superior response compared with the amorphous counterpart. To obtain deeper insight, the present materials are thoroughly characterized by scanning electron microscopy and ex situ X-ray diffraction, and the insertion of sodium ions in the TiO2 bulk phases is systematically modeled by density functional theory calculations. The present results may contribute to the development of more systematic screening approaches to identify suitable active materials for highly efficient sodium-based energy storage systems.

Aqueous processing of paper separators by filtration dewatering: towards Li-ion paper batteries

Despite the high number of research articles regarding the development of new high performance electrolytes for Li-ion batteries, relatively little work has been carried out for the investigation of green, mechanically robust, safe and commercially applicable paper separators. In this work, newly elaborated paper separators made of natural cellulose fibres are prepared by filtration dewatering. Paper separators show high porosity, wettability and mechanical robustness along with remarkable ion transport characteristics. The novel approach is conceptually validated by constant current charge/discharge cycling in a lab-scale Li-ion all-paper “pouch” cell assembled with a four-layer handsheet stacking separator in combination with a graphite-based paper-anode and a LiFePO4-based paper-cathode. This unravels the possibility of implementing the newly elaborated paper separators in safe, green and cost effective energy storage devices especially as they are obtained by rapid, low-cost and eco-friendly water-based paper-making techniques.

Novel multiphase electrode/electrolyte composites for next generation of flexible polymeric Li-ion cells

An innovative multiphase electrode/electrolyte composite is proposed here, which is obtained by a fast, versatile and easily scalable UV-induced free-radical photo-polymerisation technique. This novel configuration consists of a methacrylic-based polymer electrolyte directly formed in situ at the interface of different electrode films (i.e. commercial graphite and hydrothermally synthesized LiFePO4). Conformal coatings are confirmed by SEM analysis which indicates an intimate interfacial adhesion between the electrode material particles and the polymer electrolyte. Laboratory-scale lithium pouch cells assembled by contacting a lithium metal counter electrode over the as-prepared electrode/electrolyte composites display good ambient temperature charge/discharge characteristics, at the level of the corresponding lithium cells in liquid electrolyte, along with very stable cyclability even at high current rates. In addition, preliminary results of a laboratory-scale Li-ion polymer cell, assembled by contacting the LiFePO4 cathode with the graphite anode, both in situ coated with the polymer electrolyte, are presented. The obtained findings outline the practical relevance of the novel procedure adopted which leads to the preparation of composite films with interesting performance, particularly for the next generation of flexible all-solid-state Li-ion microbatteries.

UV-Induced Radical Photo-Polymerization: A Smart Tool for Preparing Polymer Electrolyte Membranes for Energy Storage Devices.

In the present work, the preparation and characterization of quasi-solid polymer electrolyte membranes based on methacrylic monomers and oligomers, with the addition of organic plasticizers and lithium salt, are described. Noticeable improvements in the mechanical properties by reinforcement with natural cellulose hand-sheets or nanoscale microfibrillated cellulose fibers are also demonstrated. The ionic conductivity of the various prepared membranes is very high, with average values approaching 10-3 S cm-1 at ambient temperature. The electrochemical stability window is wide (anodic breakdown voltages > 4.5 V vs. Li in all the cases) along with good cyclability in lithium cells at ambient temperature. The galvanostatic cycling tests are conducted by constructing laboratory-scale lithium cells using LiFePO4 as cathode and lithium metal as anode with the selected polymer electrolyte membrane as the electrolyte separator. The results obtained demonstrate that UV induced radical photo-polymerization is a well suited method for an easy and rapid preparation of easy tunable quasi-solid polymer electrolyte membranes for energy storage devices.

Flexible Cellulose-Based Electrodes: Towards Eco-friendly All-paper Batteries

In the present work an easy paper-making technique is used for the manufacture of low cost and low environmental impact all-paper-based Li-ion cells. The cells are composed of two paper-like electrodes, prepared using micrometric-sized graphite (anode) and LiFePO4 (cathode) as active materials and truly natural microfibrillated cellulose as binder, and paper hand-sheets soaked in a standard liquid electrolyte solution as separator between them. The specific capacity obtained is even superior to that of standard PVdF-binded cell assembled with the same electrodes, and remains stable over prolonged cycling, indicating that the cellulose fibres do not affect the cycling stability. In this study, no organic solvents or synthetic polymer binders are used all along the production of the cell components which, in addition, can be easily re-dispersed in water by simple mechanical stirring as well as common paper handsheets

Combined Structural, Chemometric, and Electrochemical Investigation of Vertically Aligned TiO2 Nanotubes for Na-ion Batteries

In the challenging scenario of anode materials for sodium-ion batteries, TiO2 nanotubes could represent a winning choice in terms of cost, scalability of the preparation procedure, and long-term stability upon reversible operation in electrochemical cells. In this work, a detailed physicochemical, computational, and electrochemical characterization is carried out on TiO2 nanotubes synthesized by varying growth time and heat treatment, viz. the two most significant experimental parameters during preparation. A chemometric approach is proposed to obtain a concrete and solid multivariate analysis of sodium battery electrode materials. Such a statistical approach, combined with prolonged galvanostatic cycling and density functional theory analysis, allows identifying anatase at high growth time as the TiO2 polymorph of choice as an anode material, thus creating a benchmark for sodium-ion batteries, which currently took the center stage of the research in the field of energy storage systems from renewables.

Siloxane Diacrylate-based All-Solid Polymer Electrolytes for Lithium Batteries

Fully solid polymer electrolyte (SPE) membranes were prepared by UV induced free radical polymerisation (UV-curing) of acrylated siloxane polyalkyleneoxide copolymers in the presence of different lithium salts. The main chain contains locally mobile segments of ethoxy groups as part of the copolymer, and these moieties can provide coordination sites for the mobility of Li+ ions. The materials are produced through a solvent free procedure, and used as ion-conducting media as well as a separator in high temperature lithium-based batteries. The preparation process is easy, simple and versatile. The final product obtained demonstrates good mechanical integrity due to the highly cross-linked nature of the polymer network, and wide thermal stability. The membranes are also soft, easy to manage and transparent. They also exhibit acceptable ionic conductivity and wide electrochemical stability window