Nanogels are nanosized crosslinked polymer networks capable of absorbing large quantities of water. Specifically, smart nanogels are interesting because of their ability to respond to biomedically relevant changes like pH, temperature, etc. In the last few decades, hybrid nanogels or composites have been developed to overcome the ever increasing demand for new materials in this field. In this context, a hybrid refers to nanogels combined with different polymers and/or with nanoparticles such as plasmonic, magnetic, and carbonaceous nanoparticles, among others. Research activities are focused nowadays on using multifunctional hybrid nanogels in nanomedicine, not only as drug carriers but also as imaging and theranostic agents. In this review, we will describe nanogels, particularly in the form of composites or hybrids applied in nanomedicine.

Fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are the most frequently used electrolyte additives to enhance the lifetime of anode materials in Li-ion batteries, but for silicon it is still ambiguous when FEC or VC is more beneficial. Herein, a low-cost nanostructured silicon/carbon anode derived from HSiCl3 is tailored by the rational choice of the additive, to obtain an anode material outperforming current complex silicon structures. We demonstrate highly reversible areal capacities of up to 5 mAh/cm2 at 4.4 mg/cm2 mass loading, a specific capacity of 1280 mAh/gAnode, a capacity retention of 81 % after 500 deep-discharge cycles versus lithium metal and successful full-cell tests with high-voltage cathodes meeting the requirements for real application. Electrochemical impedance spectroscopy and post-mortem investigation provide new insights in tailoring the interfacial properties of silicon-based anodes for high performance anode materials based on an alloying mechanism with large volume changes. The role of fluorine in the FEC-derived interfacial layer is discussed in comparison with the VC-derived layer and possible degradation mechanisms are proposed. We believe that this study gives a valuable understanding and provides new strategies on the facile use of additives for highly reversible silicon anodes in Li-ion batteries

Since the resurgence of interest in lithium–sulfur (Li–S) batteries at the end of the 2000s, research in the field has grown rapidly. Li–S batteries hold great promise as the upcoming post-lithium-ion batteries owing to their notably high theoretical specific energy density of 2600 W h kg⁻¹, nearly five-fold larger than that of current lithium-ion batteries. However, one of their major technical problems is found in the shuttling of soluble polysulfides between the electrodes, resulting in rapid capacity fading and poor cycling stability. This review spotlights the foremost findings and the recent progress in enhancing the electrochemical performance of Li–S batteries by using nanoscaled metal compounds and metals. Based on an overview of reported functional metal-based materials and their specific employment in certain parts of Li–S batteries, the underlying mechanisms of enhanced adsorption and improved reaction kinetics are critically discussed involving both experimental and computational research findings. Thus, material design principles and possible interdisciplinary research approaches providing the chance to jointly advance with related fields such as electrocatalysis are identified. Particularly, we elucidate additives, sulfur hosts, current collectors and functional interlayers/hybrid separators containing metal oxides, hydroxides and sulfides as well as metal–organic frameworks, bare metal and further metal nitrides, metal carbides and MXenes. Throughout this review article, we emphasize the close relationship between the intrinsic properties of metal-based nanostructured materials, the (electro)chemical interaction with lithium (poly)sulfides and the subsequent effect on the battery performance. Concluding the review, prospects for the future development of practical Li–S batteries with metal-based nanomaterials are discussed.

Silicon is a promising negative electrode for secondary lithium-based batteries, but the electrochemical reversibility of particularly nanostructured silicon electrodes drastically depends on their interfacial characteristics, commonly known as the solid electrolyte interface (SEI). The beneficial origin of certain electrolyte additives or different binders is still discussed controversially owing to the challenging peculiarities of interfacial post-mortem investigations of electrodes. In this work, we address the common difficulties of SEI investigations of porous silicon/carbon nanostructures and study the addition of a fluoroethylene carbonate (FEC) as a stabilizing additive as well as the use of two different binders, carboxymethyl cellulose/styrene-butadiene rubber (CMC/SBR) and polyacrylic acid (PAA), for the SEI formation. The electrode is composed of silicon nanocrystallites below 5 nm diameter allowing a detailed investigation of interfacial characteristics of silicon owing to the high surface area. We first performed galvanostatic long-term cycling (400 times) and carried out comprehensive ex situ characterization of the cycled nanocrystalline silicon electrodes with XRD, EDXS, TEM and XPS. We modified the preparation of the electrode for post-mortem characterization to distinguish between electrolyte components and the actual SEI. The impact of the FEC additive and two different binders on the interfacial layer is studied and the occurrence of diverse compounds, in particular LiF, Li₂O and phosphates, is discussed. These results help to understand general issues in SEI formation and to pave the way for the development of advanced electrolytes allowing for a long-term performance of nanostructured Si-based electrodes.