Gel electrolytes based on lithium modified silica nano-particles

Advanced Materials Based on Polymers and Ionic Liquids

Ionic liquids (ILs) are ambient temperature molten salts, which have attracted considerable attention owing to their unique properties. In this contribution, we review advanced materials composed of ILs and polymers for the basis of a new design protocol to fabricate novel materials. As electrolytes for electrochemical devices, cross-linked polymers containing ILs (ion gels) are endowed with functional properties inherited from ILs and mechanical consistency derived from polymers. To create such materials, micro-phase separation of block copolymers and colloidal arrays in the ILs are utilized. Based on the molecular design of task-specific ILs, the resultant ion gels are applicable as electrolytes for actuator, fuel cell, and secondary battery applications. Thermo- and photo-responsive polymers in ILs are also highlighted, whereby such stimuli elicit changes in the solubility of the self-assembly of block copolymers and colloidal arrays in the ILs. Further, thermo- and photo-reversible changes in the self-assembled structure can be exploited to demonstrate sol-gel transitions and fabricate photo-healable materials.

Highly Conductive Solid-State Hybrid Electrolytes Operating at Subzero Temperatures

We report a unique, highly conductive, dendrite-inhibited, solid-state polymer electrolyte platform that demonstrates excellent battery performance at subzero temperatures. A design based on functionalized inorganic nanoparticles with interconnected mesopores that contain surface nitrile groups is the key to this development. Solid-state hybrid polymer electrolytes based on succinonitrile (SN) electrolytes and porous nanoparticles were fabricated via a simple UV-curing process. SN electrolytes were effectively confined within the mesopores. This stimulated favorable interactions with lithium ions, reduced leakage of SN electrolytes over time, and improved mechanical strength of membranes. Inhibition of lithium dendrite growth and improved electrochemical stability up to 5.2 V were also demonstrated. The hybrid electrolytes exhibited high ionic conductivities of 2 × 10^-3 S cm^-1 at room temperature and >10^-4 S cm^-1 at subzero temperatures, leading to stable and improved battery performance at subzero temperatures. Li cells made with lithium titanate anodes exhibited stable discharge capacities of 151 mAh g^-1 at temperatures below -10 °C. This corresponds to 92% of the capacity achieved at room temperature (164 mAh g^-1). Our work represents a significant advance in solid-state polymer electrolyte technology and far exceeds the performance available with conventional polymeric battery separators.

Hybrid materials science: a promised land for the integrative design of multifunctional materials

For more than 5000 years, organic-inorganic composite materials created by men via skill and serendipity have been part of human culture and customs. The concept of "hybrid organic-inorganic" nanocomposites exploded in the second half of the 20th century with the expansion of the so-called "chimie douce" which led to many collaborations between a large set of chemists, physicists and biologists. Consequently, the scientific melting pot of these very different scientific communities created a new pluridisciplinary school of thought. Today, the tremendous effort of basic research performed in the last twenty years allows tailor-made multifunctional hybrid materials with perfect control over composition, structure and shape. Some of these hybrid materials have already entered the industrial market. Many tailor-made multiscale hybrids are increasingly impacting numerous fields of applications: optics, catalysis, energy, environment, nanomedicine, etc. In the present feature article, we emphasize several fundamental and applied aspects of the hybrid materials field: bioreplication, mesostructured thin films, Lego-like chemistry designed hybrid nanocomposites, and advanced hybrid materials for energy. Finally, a few commercial applications of hybrid materials will be presented.

25th anniversary article: polymer-particle composites: phase stability and applications in electrochemical energy storage

Polymer-particle composites are used in virtually every field of technology. When the particles approach nanometer dimensions, large interfacial regions are created. In favorable situations, the spatial distribution of these interfaces can be controlled to create new hybrid materials with physical and transport properties inaccessible in their constituents or poorly prepared mixtures. This review surveys progress in the last decade in understanding phase behavior, structure, and properties of nanoparticle-polymer composites. The review takes a decidedly polymers perspective and explores how physical and chemical approaches may be employed to create hybrids with controlled distribution of particles. Applications are studied in two contexts of contemporary interest: battery electrolytes and electrodes. In the former, the role of dispersed and aggregated particles on ion-transport is considered. In the latter, the polymer is employed in such small quantities that it has been historically given titles such as binder and carbon precursor that underscore its perceived secondary role. Considering the myriad functions the binder plays in an electrode, it is surprising that highly filled composites have not received more attention. Opportunities in this and related areas are highlighted where recent advances in synthesis and polymer science are inspiring new approaches, and where newcomers to the field could make important contributions.

From colloidal stability in ionic liquids to advanced soft materials using unique media

Owing to their fascinating properties, ionic liquids (ILs) are now receiving a great deal of attention as alternatives to organic solvents and electrolyte solutions and as synthetic and dispersion media for colloidal systems. Colloidal stability is an essential factor in determining the properties and performance of colloidal systems combined with ILs. The remarkable properties of ILs primarily originate from their highly ionic nature. Although such high ionic strength often causes colloidal aggregation in aqueous and organic suspensions, some colloidal particles can be well suspended in ILs without any stabilizers. In the first part of this article, we focus on recent experiments conducted to investigate the colloidal stability of bare and polymer-grafted silica nanoparticles and on the surface force between silica substrates and ILs. Three different repulsions between colloidal particles (i.e., electrostatic, steric, and solvation forces) are also highlighted, after which a possible interpretation of the results in terms of the stabilization mechanism in ILs both in the presence and in the absence of stabilizers is proposed. The latter part of this article provides an overview of our recent studies on colloidal soft materials with ILs. On the basis of the dispersed states of the silica colloids in ILs, two different soft materials, a colloidal gel and a colloidal glass in ILs, were fabricated. The relationship between their functional properties, such as ionic transport, rheological properties, and optical properties, and the microstructure of the colloidal materials is also described.

Voltammetry and redox charge storage capacity of ferrocene-functionalized silica nanoparticles

We describe the electrochemistry of 15 nm diameter silica nanoparticles densely functionalized with ferrocene (FcSiO(2)) through siloxane couplings. Each nanoparticle bears approximately 600 Fc sites, as measured by potentiometric titration (590 Fc) and diffusion-controlled voltammetry (585 Fc) and estimated by XPS (630 Fc). The nanoparticle ferrocene coverage amounts to ca. a complete monolayer of ferrocene sites, which react electrochemically without mutual interactions and which are apparently fully accessible for diffusion-controlled electrode reactions. Diffusion-controlled voltammetry of the FcSiO(2) nanoparticles was observed in dilute methanol dispersions and in more concentrated slurry phases formed in methanol/acetonitrile mixtures. Electrochemical studies reveal interesting behavior in the dilute and more concentrated solutions. Because of the large nanoparticle surface area/volume ratio, the ferrocene-coated silica nanoparticles are capable of storing up to 5 x 10(7) C/m(3) of redox charge as dry phases and 6 x 10(5) C/m(3) in the concentrated slurries.