This study establishes an approach to 3D print Li‐ion battery electrolytes with controlled porosity using a dry phase inversion method. This ink formulation utilizes poly(vinyldene fluoride) in a mixture of N‐methyl‐2‐pyrrolidone (good solvent) and glycerol (weak nonsolvent) to generate porosity during a simple drying step. When a nanosized Al2O3 filler is included in the ink, uniform sub‐micrometer pore formation is attained. In other words, no additional processing steps such as coagulation baths, stretching, or etching are required for full functionality of the electrolyte, which makes it a viable candidate to enable completely additively manufactured Li‐ion batteries. Compared to commercial polyolefin separators, these electrolytes demonstrate comparable high rate electrochemical performance (e.g., 5 C), but possess better wetting characteristics and enhanced thermal stability. Additionally, this dry phase inversion method can be extended to printable composite electrodes, yielding enhanced flexibility and electrochemical performance over electrodes prepared with only good solvent. Finally, sequentially printing this electrolyte ink over a composite electrode via a direct write extrusion technique has been demonstrated while maintaining expected functionality in both layers. These ink formulations are an enabling step toward completely printed batteries and can allow direct integration of a flexible power source in restricted device areas or on nonplanar surfaces.
A novel metal supported Solid Oxide Fuel Cell has been developed, capable of operating at temperatures of 500-600°C. The rationale behind the materials used to construct this fuel cell type is given, and results presented from cell and short stack testing, including durability and thermal cycling trials. This new fuel cell variant is shown to be tolerant of carbon monoxide durable, robust to thermal and redox cycling, and capable of delivering technologically relevant power densities.
Thin-film batteries that can be folded, bent, and even repeatedly creased with minimal or no loss in electrochemical performance have been demonstrated and systematically evaluated using two dynamic mechanical testing approaches for either controlled bending or creasing of flexible devices. The results show that mechanically robust and flexible Li-ion batteries (Li4Ti5O12//LiFePO4) based on the use of a nonwoven multiwalled carbon nanotube (MWNT) mat as a current collector (CC) exhibited a 14-fold decrease in voltage fluctuation at a bending strain of 4.2%, as compared to cells using traditional metal foil CCs. More importantly, MWNT-based full-cells exhibited excellent mechanical integrity through 288 crease cycles, whereas the foil full-cell exhibited continuously degraded performance with each fold and catastrophic fracture after only 94 folds. The enhancements due to MWNT CCs can be attributed to excellent interfacial properties as well as high mechanical strength coupled with compliancy, which allow the batteries to easily conform during mechanical abuse. These results quantitatively demonstrate the substantial enhancement offered in both mechanical and electrochemical stability which can be realized with traditional processing approaches when an appropriate choice of a flexible and robust CC is utilized.
Graphene has opened up new opportunities
for scientific and technological
innovations because of its astonishing electrical, mechanical, chemical,
and thermal properties. For instance, graphene-based nanocomposites
have found extensive applications in Li-ion batteries (LIBs) as scientists
and engineers seek to achieve superior electrochemical performances.
The laboratory module reported herein includes both chemical fabrication
and electrochemical characterizations of graphene nanosheets (GNSs).
The GNS powders are fabricated through the chemical exfoliation of
graphite, and the resulting morphological and structural changes are
evaluated by means of scanning electron microscopy and X-ray diffraction.
Li storage electrochemical characteristics of GNSs are then assessed
via galvanostatic chronopotentiometry and compared with that of graphite,
a commonly used anode material in LIBs. This novel laboratory module,
suitable for a wide range of students with a general chemistry background,
has been successfully implemented in a multidisciplinary laboratory
and lecture course entitled Experimental Nanomaterials and Nanoscience.
Because the laboratory connects chemistry and materials engineering
to a real-world application, it raises students’ interest in
and awareness of nanomaterials’ contribution to the renewable
and clean energy field.
Billions of internet connected devices used for medicine, wearables, and robotics require microbattery power sources, but the conflicting scaling laws between electronics and energy storage have led to inadequate power sources that severely limit the performance of these physically small devices. Reported here is a new design paradigm for primary microbatteries that drastically improves energy and power density by eliminating the vast majority of the packaging and through the use of high‐energy‐density anode and cathode materials. These light (50–80 mg) and small (20–40 µL) microbatteries are enabled though the electroplating of 130 µm‐thick 94% dense additive‐free and crystallographically oriented LiCoO2 onto thin metal foils, which also act as the encapsulation layer. These devices have 430 Wh kg−1 and 1050 Wh L−1 energy densities, 4 times the energy density of previous similarly sized microbatteries, opening up the potential to power otherwise unpowerable microdevices.
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