Davide Beneventi

Cellulose-based Li-ion batteries: a review

Li-ion batteries (LIBs) are the most employed power source in portable electronics (e.g., cellular phones, laptop computers…) and are accounted as very promising storage/power systems for future electric/hybrid-electric powered transportation. However for their future development, low production costs and environmental friendliness will be key parameters. In this context, the introduction of water processable biosourced polymers such as cellulose and its derivatives is very interesting and is emerging as a viable route toward the development of green materials and processes for LIB manufacturing. The present review briefly introduces the Li-ion technology and gives an overview on cellulose and cellulose derivatives for the elaboration of separators, electrolytes and electrodes.

Role of surfactant structure on surface and foaming properties

Abstract The influence of surfactant structure on interface properties was estimated from measurements of the static and dynamic surface tension and the interface complex modulus, as obtained from an image analysis technique based on the oscillating bubble method. A simplified kinetic model of surfactants molecular adsorption at the gas–liquid interface was introduced and the rate of adsorption was determined from measurements of the dynamic surface tension. The mean life time of foams generated from bubbling air through different surfactant solutions was measured using a modified Bikerman device. The major conclusion arising from this study, as expected from basic considerations, was that the chain length of the hydrophobic part of the surfactant plays a determining role with respect to both the kinetic migration to the interfaces and the ensuing surface activity, as shown by the extent of phase delay and foam stability.

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.

Preparation of highly hydrophobic and lipophobic cellulose fibers by a straightforward gas-solid reaction.

This work describes a very simple, rapid, and efficient approach to the hydrophobization and lipophobization of cellulose fibers through their reaction with gaseous trichloromethylsilane (TCMS). The characterization of the modified surface involved FTIR-ATR and solid-state (29)Si NMR spectroscopy, scanning electron microscopy (SEM), and contact angle measurements with different liquids. The modification generated an inorganic coating around the fibers, associated with the construction of a three-dimensional network of Si-O-Si bridges partly bound to the polysaccharide macromolecules. This coating conferred both a high hydrophobicity and a lipophobicity to the samples even when the treatments applied modest TCMS quantities and reaction times as short as 30 s. The green connotation of this novel process constitutes an additional positive feature.

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.

Photoluminescence of 2,7-Poly(9,9-dialkylfluorene-co-fluorenone) Nanoparticles: Effect of Particle Size and Inert Polymer Addition

Stable nanoparticle dispersions of 2,7-poly(9,9-dialkylfluorene-co-fluorenone) (PFFO) and of PFFO/cellulose acetate butyrate (CAB) mixtures with particle size ranging between 5 and 500 nm were prepared by miniemulsification in the presence of a cationic surfactant. Photoluminescence spectra of nanoparticle dispersions showed that the decrease of particle size and of the PFFO/CAB mass ratio induced the progressive suppression of the PFFO excimer emission band at 535 nm. This behavior was associated with the limited ordered structure and π-stacking arrangement of PFFO molecules when confined within nanoparticles smaller than 150 nm or in the presence of CAB molecules. All nanoparticle dispersions displayed high dimensional stability; however, the relative intensity of the excimer emission band increased upon aging reflecting excimer formation due to the high mobility of PFFO chains (T(g) -20 °C) or fluorene moiety oxidation.

Surfactant (TTAB) role in the preparation of 2,7-Poly(9,9-dialkylfluorene-co-fluorenone) nanoparticles by miniemulsion.

The role of tetradecyltrimethylammonium bromide (TTAB) and its partition between water, chloroform, and the chloroform/water interface during the miniemulsification of a photoluminescent polymer was investigated by indirect interfacial tension/elasticity measurements. Dynamic interfacial tension and elasticity measurements showed the presence of a gas-liquid phase transition at the chloroform/water interface and the formation of a rigid interface, which was supposed to promote emulsion stability. The parameters of the adsorption isotherms and the TTAB partition coefficient were obtained from surface tension isotherms. Dynamic surface tension measurements performed after TTAB water/chloroform extraction were used to compute TTAB partition between water, chloroform, and the chloroform/water interface. Model calculations allowed identifying (for the tested conditions) the minimum size of emulsion droplets before the onset of instability and the segregation of a sizable amount of TTAB in the final polymer nanoparticles, which induced a shift in the 2,7-poly(9,9-dialkylfluorene-co-fluorenone) (PF) photoluminescence emission band. The size of the emulsion droplets of the final polymer particles and the amount of segregated TTAB were in good agreement with the corresponding experimental values.

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

Photoluminescent Patterned Papers Resulting from Printings of Polymeric Nanoparticles Suspension

The printability of a copolyfluorene-fluorenone (PFFO) photoluminescent nanoparticle aqueous suspension on commercial tracing paper was here investigated. The nanoparticles suspension was obtained by miniemulsification of a suitable preformed photoluminescent organic polymer. The structural, physicochemical, and rheological characteristics of the nanoparticles suspension were first studied before considering its printability by inkjet and flexography techniques. The native properties of the nanoparticles suspension revealed to be more suitable for inkjet printing which was successfully used to print photoluminescent patterns using a very low amount of PFFO.