Silicon‐Microtube Scaffold Decorated with Anatase TiO₂ as a Negative Electrode for a 3D Litium‐Ion Microbattery

Abstract

Smart integrated miniaturized microsystems require harvesting and storage power sources in order to be autonomous. From the energy point of view, commercially available lithium-ion microbatteries with planar topology do not have suffi cient performance to address the challenging autonomy of microsystems. In aiming for this goal, new concepts based on 3D topologies have been published [ 1 ] in last ten years. By developing a 3D topology, the surface area, and thus the capacity, of the device is increased. The fabrication of high-surfacecapacity devices at the microscale is performed by 1) nano-/micro-structuring a substrate and 2) making a conformal deposition of an electrochemically active thin fi lm on the 3D topology. To achieve conformal deposition on steps and other 3D features, electrodeposition (ED) or highvacuum atomic layer deposition (ALD) are required. The gain obtained with the 3D topology is referred to as the ratio between the 3D and 2D surface areas, and it is known as the area enlargement factor (AEF). The energy density is drastically increased in the 3D topology compared to the planar topology. The power density is also enhanced because the thickness of the 3D deposited material is kept relatively low; the diffusion length of the lithium ions inside the electrode material is reduced, leading to an increase in the charge/discharge rate of the 3D microstorage device.Interdigitated 3D lithium-ion microbatteries based on carbon micro-electromechanical system (C-MEMS) technology with a surface capacity close to 125 µA h cm -2 have been reported [ 2,3 ] by Dunn and co-workers. The micromachining of silicon or glass substrates has been performed by the Peled group [ 4,5 ] in order to fabricate a liquid-based 3D lithium-ion microbattery. Microcontainers fi lled with the battery materials have reached 1 mA h cm -2 under 2 V; the exacerbated surface capacity is clearly enhanced due to the 3D topology. Recently, an interdigitated lithium-ion microbattery based on porous electrodes has been reported with power and energy capabilities greatly enhanced by the 3D porous network. [ 6 ] Simon and co-workers [ 7 ] have developed a nano-architectured aluminum-based 3D metallic current-collector; on top of the 3D nanostructure, a thin layer of anatase TiO 2 polymorph was deposited by ALD. An AEF of 10 is exhibited between the measured 2D and 3D surface capacity. An interesting concept using top-down and bottom-up approaches has been published by Gerasopoulos et al. [ 8 ] using low-aspectratio gold micropillars decorated with biological nano-objects (tobacco mosaic virus, TMV); an enhancement of the surface capacity of a V 2 O 5 thin fi lm deposited by ALD was demonstrated using this novel structure. Previously, Gerasopoulos [ 9 ] et al. reported the ALD of TiO 2 onto biological scaffolds composed of TMV. The TMV nanostructures had been covered beforehand by a nickel conductive layer. The bio-templating approach [ 10 ] has also been used by Kim et al. to fabricate a TiO 2 3D nanonetwork based on peptide assembly; a h...

Structural Optimization of 3D Porous Electrodes for High-Rate Performance Lithium Ion Batteries

“…Due to our ultra-thick (200 μm) electrode design, the footprint power and energy density is much higher than that of thin electrodes reported previously. 24,32,55,56 Finally, our electrodes are very stable as demonstrated by the long-term cycle test results shown in Figure S5, Supporting Information.…”

Titanium dioxide nanotrees for high-capacity lithium-ion microbatteries

“…[7][8][9][10] The rapid expansion of integrated microsystems has stimulated widespread interests to develop high-performance lithium ion microbatteries, which are used to provide on-board energy for smart medicine, microsensors, microelectromechanical systems (MEMS) and radio-frequency identification (RFID). In contrast, three-dimensional (3D) electrodes, such as nanowire arrays, satisfy the requirements of both high areal capacity and short transport lengths in microbatteries; [14][15][16][17][18] however, their areal/volumetric capacity is hindered by the insufficient surface area and the considerable free space among adjacent nanowires. In contrast, three-dimensional (3D) electrodes, such as nanowire arrays, satisfy the requirements of both high areal capacity and short transport lengths in microbatteries; [14][15][16][17][18] however, their areal/volumetric capacity is hindered by the insufficient surface area and the considerable free space among adjacent nanowires.…”

Latest advances in the manufacturing of 3D rechargeable lithium microbatteries

“…This previous work inspired another interesting design that has been recently developed consisting of a silicon microtube scaffold into which one could conformally deposit all the battery components (see Figure 8a) [48]. Prior the fabrication of the scaffold, the area enlargement factor was calculated for different geometrical parameters (outer diameter, inner depth and structure pitch) to optimize the 3D-MLIB.…”