Continuous novelty as the basis for creative advance in rapidly developing different form-factor microelectronic devices requires seamless integrability of batteries. Thus, in the past decade, along with developments in battery materials, the focus has been shifting more and more towards innovative fabrication processes, unconventional configurations, and designs with multi-functional components.We present here, for the first time, a novel concept and feasibility study of a 3D-microbattery printed by fused-filament fabrication (FFF). The reversible electrochemical cycling of 3D printed lithium iron phosphate (LFP) and lithium titanate (LTO) composite polymer electrodes vs. the lithium metal anode has been demonstrated in cells containing conventional non-aqueous and ionic-liquid electrolytes. We believe that by using comprehensively structured interlaced electrode networks it would be possible not only to fabricate free form-factor batteries but also to alleviate the continuous volume changes occurring during charge and discharge.

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Printed secondary batteries have market potential in two main fields -highly customized personal electronic devices, and smallscale battery production. While many different technologies may be utilized to produce a printed battery, drop-on-demand (DoD) dispensing has the advantage of being highly tailor-made, notably with the ability to produce both very thin and thick batteries. We report the cathode printing protocols, morphology and electrochemical properties of patterned electrodes. Our electrode inks are aqueous, with obvious environmental and processing benefits. We chose to study the lithium iron phosphate (LFP) cathode because of its excellent electrochemical performance. DoD-printed LFP cathodes exhibit close to theoretical capacity value, highrate capability and close to 100% coulombic efficiency. The similarity of the voltage profiles, electrochemical performance and impedance components of the AC spectra of lithium cells with printed LFP cathodes to those of commercial electrodes, indicates that printing does not alter the charge/discharge mechanism of active electrode material.

Here, we studied for the first time the kinetics of the chemical reactions between oxide-free silicon and electrolytes and the composition and morphology of the surface film formed during these reactions. We found that the kinetics of these reactions is swift; a few nm passivating film is formed during a few milliseconds and a complete passivation takes place in about 30 seconds. XPS study show a passivating film consisting of large organic molecules or polymers containing C-O, C=O, C-F x and O-C-F moieties, SiF x , SiO x F y , some SiO 2 and small amounts of LiF. Containing only traces of Li, it cannot serve as an SEI and may lead to lesser uniformity of the SEI formed on top of it.