Microfabrication Strategies for Silicon Anodes in On-Chip and Miniaturized Batteries.

The rapid expansion of autonomous microsystems, implantable sensors, wireless sensor nodes, Internet-of-Things devices, distributed electronics, and heterogeneous system-on-chip platforms has intensified the demand for compact electrochemical energy-storage systems that can be integrated directly with microfabricated devices. Among the various negative electrode materials, silicon is particularly attractive for miniaturized lithium-ion batteries because of its high theoretical lithium-storage capacity, abundance, compatibility with mature semiconductor processing, and direct availability as both an active material and a structural platform. However, the practical implementation of silicon anodes in on-chip and miniaturized batteries remains difficult because lithiation-induced volume expansion, fracture, unstable solid-electrolyte interphase formation, loss of electrical contact, and process-integration constraints become more severe as the battery footprint is reduced to the microscale. In contrast to conventional slurry-cast silicon electrodes, silicon anodes for microbatteries can exploit microfabrication strategies such as thin-film deposition, photolithography, deep reactive ion etching, metal-assisted chemical etching, nanoimprint lithography, laser patterning, template-assisted growth, atomic layer deposition, and wafer-level encapsulation. These methods enable deterministic control over electrode geometry, areal loading, porosity, current-collector contact, diffusion length, mechanical compliance, interfacial chemistry, and compatibility with complementary metal-oxide-semiconductor and microelectromechanical-system platforms. This review summarizes the recent progress in microfabrication strategies for silicon anodes in on-chip and miniaturized batteries, emphasizing the relationship between the process route, electrode architecture, mechanical stability, electrochemical performance, and manufacturability.