1D Buliding Block Strategies for High Energy Density Li-Ion Batteries

Abstract

Ever-increasing demand for high-performance portable electronics, electric vehicles (EVs) and grid-scale energy storage systems (ESSs) has been in relentless pursuit of advanced energy storage systems with reliable electrochemical properties. Among a vast variety of rechargeable power sources, undoubtedly, lithium-ion batteries have been most widespread and still garnered considerable attention due to their well-customized battery characteristics. From the electrode architecture point of view, most conventional electrodes are characterized with simple and random pile-up of electrode active materials, carbon powder conductive additives and polymer binders on top of metallic foil current collectors. Unfortunately, such a stereotyped electrode architecture often gives rise to non-uniform and sluggish electron/ion transport particularly in their through-thickness direction and is also vulnerable to structural disruption upon mechanical deformation. In particular, the poorly-developed electron/ion conduction pathways of the electrodes eventually provoke unwanted electrochemical polarization, which becomes more serious at harsh operating conditions such as high-mass loading electrodes and fast charge/discharge current densities that are urgently needed for high-energy EV batteries. Due to these unavoidable limitations, the conventional electrode architecture has posed a formidable challenge to sustainable progress of battery performance, thus pushing us to search for alternative solutions. Here, we demonstrate a new class of all-nanomat lithium-ion batteries (LIBs) based on one-dimensional (1D) building elements interweaved into heteronanomat skeletons. Among various electrode materials, silicon (Si), over-lithiated layered oxide (OLO) materials and redox-active organic materials are chosen as model systems to explore the feasibility of this new cell architecture and achieve unprecedented cell capacity. Nanomat electrodes, which are completely different from conventional slurry-cast electrodes, are fabricated through concurrent electrospinning (for polymeric nanofibers) and electrospraying (for electrode materials/carbon nanotubes (CNTs)). Electrode active material powders are compactly embedded in the spatially interweaved polymeric nanofiber/CNT heteromat skeletons, which play a crucial role in constructing three-dimensional (3D)-bicontinuous ion/electron transport pathways and in removing metallic foil current collectors. Driven by the aforementioned structural/chemical uniqueness, the all-nanomat electrodes show exceptional improvement in electrochemical performance as well as mechanical deformability, which lie far beyond the values achievable with conventional LIB technologies.