Kinetics, isotherm, thermodynamic, and adsorption mechanism studies of La(OH)3-modified exfoliated vermiculites as highly efficient phosphate adsorbents

Exfoliated two-dimensional (2D) sheets can readily stack to form flexible, free-standing films with lamellar microstructure. The interlayer spaces in such lamellar films form a percolated network of molecularly sized, 2D nanochannels that could be used to regulate molecular transport. Here we report self-assembled clay-based 2D nanofluidic channels with surface charge-governed proton conductivity. Proton conductivity of these 2D channels exceeds that of acid solution for concentrations up to 0.1 M, and remains stable as the reservoir concentration is varied by orders of magnitude. Proton transport occurs through a Grotthuss mechanism, with activation energy and mobility of 0.19 eV and 1.2 × 10(-3) cm(2) V(-1) s(-1), respectively. Vermiculite nanochannels exhibit extraordinary thermal stability, maintaining their proton conduction functions even after annealing at 500 °C in air. The ease of constructing massive arrays of stable 2D nanochannels without lithography should prove useful to the study of confined ionic transport, and will enable new ionic device designs.

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Self-assembled two-dimensional nanofluidic proton channels with high thermal stability

Lithium ion batteries are now the dominant power for electronics and will change the power supply for vehicles and help to smoothly integrate renewable energy sources such as solar and wind to grid. In lithium ion batteries with liquid electrolytes, the organic solvents are flammable and unstable at high voltage. Especially in lithium metal batteries (LMB) where lithium dendrites can grow, the solvents can be ignited once the dendrites shortcircuit with the cathodes. To meet the high energy density and safety requirement, it is desirable to develop solid state electrolytes with high stability and mechanical strength. The solid state electrolytes can be classified into two categories: inorganic electrolytes and solid polymer electrolytes (SPE). Inorganic electrolytes typically have ionic conductivity at room temperature (10−2–10−4 S cm−1) close to or even higher than liquid electrolyte. However, their stiffness and friability result in poor film processability and high interface resistance with electrodes.[1–7] SPE are composed of lithium salts dissociated in the polymer matrix in which Li+ is allowed to transport along with the segment motion of the polymer chains. As a result, SPE are stretchable and flexible, and thus compatible with the current film-based battery technology. However, the low ionic conductivity (<10−6 S cm−1) of SPE at ambient temperature and high-temperature instability restrict their wide utilization.[8–15] Great efforts have been devoted to improving the performance of SPE. Increasing the content of Li salts or decreasing the crystallinity of polymers with composite polymers or block copolymers were able to increase the ionic conductivity by orders of magnitude.[16–18] However, other properties of SPE such as the film forming property were decreased, leading to poor mechanical strength and thermal resistance. A successful strategy was rigid-flexible coupling that applied cellulose nonwoven to support the softened SPE.[11] Another widely employed approach is to add ceramic fillers which can interact with both the salt anions and the polymer segments to promote local amorphization and enhance Li+ transport.[19–24] Accordingly, the interaction can be tailored by screening fillers with Solid state electrolytes are the key components for high energy density lithium ion batteries and especially for lithium metal batteries where lithium dendrite growth is an inevitable obstacle in liquid electrolytes. Solid polymer electrolytes based on a complex of polymers and lithium salts are intrinsically advantageous over inorganic electrolytes in terms of processability and film-forming properties. But other properties such as ionic conductivity, thermal stability, mechanical modulus, and electrochemical stability need to be improved. Herein, for the first time, 2D additives using few-layer vermiculite clay sheets as an example to comprehensively upgrade poly(ethylene oxide)-based solid polymer electrolyte are introduced. With clay sheet additives, the polymer electrolyte exhibits improved thermal stability, mechanical modulus, ionic conductivity, and electrochemical stability along with reduced flammability and interface resistance. The composite polymer electrolyte can suppress the formation and growth of lithium dendrites in lithium metal batteries. It is anticipated that the clay sheets upgraded solid polymer electrolyte can be integrated to construct high performance solid state lithium ion and lithium metal batteries with higher energy and safety.

Simultaneously Enhancing the Thermal Stability, Mechanical Modulus, and Electrochemical Performance of Solid Polymer Electrolytes by Incorporating 2D Sheets

Lithium ion-selective membrane with 2D subnanometer channels

The aim of this review is to provide an in-depth overview on the use of inorganic nano-sized entities for the generation of nanocomposite materials in the form of films and coatings for food packaging applications. According to recent trends toward “green” strategies, special focus has been dedicated to the development of nanocomposite coatings obtained using biopolymers as the main polymer matrix. After a first introductive part, the discussion has been addressed to the use of inorganic fillers, metals and metal-oxides, zeolites, and graphene. For each class of filler, a first ‘in-depth’ description of the most relevant physicochemical properties for the food packaging sector has been followed by case-by-case references to recent developments and envisaged implementations. The technical aspects that may be crucial in the design and end use of (bio)nanocomposite coatings have been covered in the last part of this work, which also includes an updated list of current applications on nano-sized inorganic fillers in the food packaging field.

https://pubs.rsc.org/en/content/articlepdf/2014/ra/c4ra01778a

Y.C. Arango

Papers

X-ray diffraction studies of the thermal behaviour of commercial vermiculites