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The fabrication of all solid-state 3D micro-supercapacitor is challenging for powering connected and miniaturized emerging electronics devices in the frame of the future Internet of Things paradigm. Here we highlight the design of a specific solid electrolyte based on ethylmethylimidazolium bis(trifluoromethanesulfonate)imide confined within polyvinylidenefluoride which enables to meet the requirements of safety, easy packaging, and leakage free 3D micro-supercapacitors. This ionogel-based microdevice (2 mm × 2 mm footprint area) exhibits good cycling stability over 30 000 cycles with an areal energy density of 4.4 µWh.cm-2 and a power density of 3.8 mW.cm-2. It can also sustain the high temperature reflow soldering process (~250 °C-5 min) without damage, which is performed to directly bond surface mounted miniaturized devices onto printed circuit boards. This strategy not only provides a reference for the design of high-performance 3D interdigitated micro-supercapacitors, but also paves the way to their further implementation in miniaturized electronic chips for Internet of Things applications. [ABSTRACT FROM AUTHOR]

Solid ionogel electrolytes are rather competitive compared to liquid carbonate based electrolyte regarding ionic conductivity but they show much better safety. It is striking that the ionogels presented here are obtained within few minutes by UV curing which triggers the formation of the polymer host network confining N-methyl,N-propylpyrrolidinium bis-(trifluoromethyl)sulfonylimide with lithium bis-(trifluoromethyl)sulfonylimide salt at the concentration of 1M. This fast and easy process allows for obtaining all-solid like micro-batteries. Herein the effect of mesh size and ethylene oxide content of various host networks is deciphered. An optimum balance between mesh size, ethylene oxide and lithium content is identified. The ionogel formed from trimethylolpropane ethoxylate triacrylate and 1,6-hexanediol diacrylate confining 90% wt of ionic liquid shows a mesh size close to 5 nm, with an enhanced fragility of the confined ionic liquid, as referred to that of the bulk one. Along with these last features, its ethylene oxide content allows a very good lithium ion diffusion. At room temperature and at C/5 cycling rate, prototype batteries LiFePO4 ionogel Li metal battery can restitute 70% of the initial capacity during up to 1200 cycles. [ABSTRACT FROM AUTHOR]

Ionogels based on in situ crosslinking of chitosan in the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIm Ac) are synthesized, and studied from macroscopic properties to preferred interactions at the host matrix/EMIm Ac interface. It is highlighted that the imidazolium cations of the ionic liquid (IL) show preferred interactions with the chitosan host matrix. This exemplifies how the confinement of ILs, through an interface effect, can induce the breakdown of aggregated regions found systematically in bulk ILs and can increase the fragility of ILs. These biopolymer based ionogels could find application as biosensors and in the field of energy. [ABSTRACT FROM AUTHOR]

Confining ionic liquids (ILs) with added lithium salt within silica host networks enhances their fragility and improves their conductivity. Overall, conductivity measurements, Raman spectroscopy of the TFSI anion and NMR spectroscopy of the lithium cation show segregative interaction of lithium ions with the SiO2 host matrix. This implies at IL/SiO2 interfaces a breakdown of aggregated regions that are found systematically in bulk ILs. Such destructuration due to the interface effect determines the fragility and thus results locally at the interface in short relaxation times, low viscosity, and good ionic conductivity. The “destructuration” of ion pairs or domains makes ILs within ionogels a competitive alternative to existing solid ionic conductors in all-solid devices, such as lithium batteries and supercapacitors. [ABSTRACT FROM AUTHOR]

We have developed flexible polymer-gel electrolytes based on a polyacrylate cross-linked matrix that confines an ionic liquid doped with a lithium salt. Free-standing solid electrolyte membrane is obtained after UV photo-polymerization of acrylic monomers dissolved inside the ionic liquid/lithium salt mixture. The liquid precursor of the photo-ionogel may also be directly deposited onto porous composite electrode, which results in all-solid state electrode/electrolyte stacking after UV illumination. Minor variations in the polymer component of the electrolyte formulation significantly affect the electrochemical behavior in LiFePO 4 /lithium and lithium/lithium cells. The rate performance increases with an increase of the ionic conductivity, which decreases with the polymer content and decreases with increasing oxygen content in the polyacrylate matrix. Their fairly low modulus endow them weak and beneficial pressure-sensitive-adhesive character. X-Rays Tomography shows that the solid-state photo-ionogel electrolytes keep their integrity upon cycling and that their surface remains smooth. The coulombic efficiency of LiFePO 4 /lithium cells increases with an increase of the adhesive strength of the photo-ionogel, suggesting a relationship between the contact intimacy at the lithium/photo-ionogel interface and the efficiency of the lithium striping/plating. In lithium/lithium cells, only the photo-ionogels with the higher adhesion strength are able to allow the reversible striping/plating of lithium. [ABSTRACT FROM AUTHOR]

This work demonstrates ink-jet printed LiFePO 4 -based composite porous electrodes for microbattery application. As binder and dispersant, we found that aqueous inks with more suitable rheological properties with respect to ink-jet printing are prepared with the low molecular weight poly-acrylic-co-maleic acid copolymer, rather than with the carboxymethyl cellulose standard binder of the lithium-ion technology. The ink-jet printed thin and porous electrode shows very high rate charge/discharge behavior, both in LiPF 6 /ethylene carbonate-dimethyl carbonate (LP30) and lithium bis(trifluoromethane)sulfonylimide salt (Li-TFSI) in N-methyl-N-propylpyrrolidinium bis(trifluoromethane)suflonylimide ionic liquid (PYR13-TFSI) electrolytes, as well as good cyclability. [ABSTRACT FROM AUTHOR]

Ink-jet printing of ionogel for low-cost microbattery is presented. Such an approach allows to provide liquid-like electrolyte performances for all-solid microdevices. Ink-jet printing process is possible thanks to sol precursor of the ionogel. This full silica based ionogels confining ionic liquid are known to be thermal resistant, serving safety and technologies requiring solder reflow. High ionic conductivity and compatibility with porous composite electrodes allow reaching good electrochemical cycling performance: full Li-ion cell with LiFePO 4 and Li 4 Ti 5 O 12 porous composite electrodes shows a surface capacity of 300 μAh cm −2 for more than 100 cycles. Such surface capacities are very competitive as compared to those obtained for microdevices based on expensive PVD processes. [ABSTRACT FROM AUTHOR]

In this work we have investigated the charge storage mechanism of MnO 2 electrodes in ionic liquid electrolytes. We show that by using an ionic liquid with a cation that has the ability to form hydrogen bonds with the active material (MnO 2) on the surface of the electrode, a clear faradaic contribution is obtained. This situation is found for ionic liquids with cations that have a low pKa, i.e. protic ionic liquids. For a protic ionic liquid, the specific capacity at low scan rate rates can be explained by a densely packed layer of cations that are in a standing geometry, with a proton directly interacting through a hydrogen bond with the surface of the active material in the electrode. In contrast, for aprotic ionic liquids there is no interaction and only a double layer contribution to the charge storage is observed. However, by adding an alkali salt to the aprotic ionic liquid, a faradaic contribution is obtained from the insertion of Li+ into the surface of the MnO 2 electrode. No effect can be observed when Li+ is added to the protic IL, suggesting that a densely packed cation layer in this case prevent Li-ions from reaching the active material surface. • Hydrogen bonding between MnO 2 and an IL cation important for charge storage. • A faradaic contribution from MnO 2 is observed with a protic IL, due to a redox reaction. • Capacity explained by a densely packed layer of standing cations on the surface. • For aprotic ILs only double layer charge storage is observed. [ABSTRACT FROM AUTHOR]