International audienceHybrid materials based on layered double hydroxides (LDHs) exhibit great potential in diverse fields such as health care, polymer composites, environment, catalysis, and energy generation. Indeed, the compositional flexibility and the scalability of LDH structures, their low cost, and their ease of synthesis have made hybrid LDHs extremely attractive for constructing smart and high-performance multifunctional materials. This review provides a comprehensive and critical overview of the current research on multifunctional hybrid LDHs. Organic–inorganic hybrid LDHs, intercalated and surface-immobilized structures, are both specifically addressed. The new trends and strategies for hybrid LDH synthesis are first described, and then the potential of the latest hybrid LDHs, polymer LDH nanocomposites, and LDH bio-nanocomposites are presented. Significant achievements published from ≈2010, including authors' results, which employ hybrid LDH assemblies in materials science, medicine, polymer nanocomposites, cement chemistry, and environmental technologies, are specifically addressed. It is concluded with remarks on present challenges and future prospects

Electrochemical insertion of Li into a series of "nanocomposites" comprised of alternating V,O, sheets and conductive polymer layers [polypyrrole (PPY) and polyaniline (PANI)] was examined and compared to the pristine V,O, material in terms of reversibility, Li site occupancy, and Li diffusion coefficients, and to the materials after oxidation treatment. The electrochemical characteristics are very sensitive to the nature of the polymer, its content, and location. The presence of surface polymer hinders Li insertion in these materials (by comparison to materials without surface polymer) and appears to result in the partial entrapment of Li ions. For modified [PANI],VV2O,, polymer incorporation results in better reversibility and increased Li capacity in the nanocomposite.[PPY]0,40V,O2 displays a greater first discharge capacity than the respective PANI material, but is not as cyclable as in O,-[PANI],,4V,O,. 0,-treatment results in the reformation of a high-potential Li site that is lost during the reductive intercalative polymerization. Li chemical diffusion coefficients are greater for the 0 2 -[PANI]V,20 nanocomposite than the xerogel by one order of magnitude, resulting in better performance at high current densities. Most important, the electrochemical response of these nanocomposites is greater than the sum of the two components (inorganic and organic), underlining the synergy of these hybrid materials.

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A nanocomposite comprised of conductive poly(aniline) chains interleaved between the layers of sol‐gel derived V2O5 displays desirable properties as a positive electrode in a Li battery. The reversible capacity of false[PANI]yV2O5 (after mild oxygen treatment) is higher than the V2O5 xerogel at intermediate discharge/charge rates at constant current. Li insertion is completely reversible in this modified hybrid material even after deep reduction to 3Li per formula unit, whereas the increased cell polarization exhibited for the xerogel in the same discharge state leads to partial irreversibility. Relaxation studies (GITT) demonstrate that Li diffusion is more rapid in the polymer nanocomposite for x(Li) < 2.0. The effect of the conductive polymer is to facilitate the insertion/deinsertion of the lithium ions between the layers.

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The layered double hydroxides (LDHs) Zn2Al(OH)6Cl·nH2O, Zn2Cr(OH)6Cl·nH2O, and Cu2Cr(OH)6Cl·nH2O have been shown to undergo staged intercalation reactions with succinate and tartrate anions. Monitoring the process in situ using energy-dispersive X-ray diffraction reveals the formation of second-stage intermediates caused by the filling of every second layer. Depending on the nature of the organic anion, the Bragg peaks of the second-stage intermediates and the fully organic exchanged materials emerge in two distinct sequences indicating two exchange pathways. For tartrate exchange, the fully exchanged material is not observed until the intermediate has gone through its maximum and the chloride precursor has disappeared completely, while for succinate exchange, the final state of intercalation and the second-stage intermediate simultaneously appear. Similar staging has previously been reported only for LiAl2(OH)6Cl·2H2O. These results demonstrate that staging in the intercalation of LDH does not involve a structural order of the host and cannot be explained by a tactoid mechanism.