Ultra-low Content Induced Intercalation Anomaly of Graphite Anode Enables Superior Capacity at Sub-zero Temperatures

Abstract

The rapid development of energy storage devices has pushed Li-ion batteries (LIBs) bear down for higher performance, better safety, lower cost, and capable to operate in wide range temperatures. However, most LIBs are used only in favorable environments rather than extreme conditions such as in ocean exploration, tropical areas, high altitude drones, and polar expeditions. When chronically or periodically exposed to these harsh environments, conventional LIBs will fail to operate due to hindered ion conductivity, interfacial issues, and sluggish desolvation of Li-ion. Additionally, graphite has been recognized as the-state-of-the-art LIBs negative electrode due to their mechanical stability, electrical conductivity, cost-efficiency, and abundant availability. However, limited Li+ storage capacity of 372 mA h g-1 via LiC6 coordination has become a bottleneck and hindered its further application for next-generation LIBs. Here we reported intercalation anomaly under ultra-low graphite content that enables super-lithiation stage in the electrode. The ultrahigh rate capability (2200 mA h g-1 at 1C and 1100 mA h g-1 at 30C) in graphite anode was achieved by reducing its amount within the electrode and adding more conductive filler in the electrode creating a highly conductive system. When operated at -20 °C, the ultra-low graphite anode keeps 50% capacity (1100 mA h g-1) of room temperature, and ranks the best among LIB anodes toward commercialization. Systematical spectroscopy analysis reveals that additional capacitive behavior and a distinct structural evolution, which leads to Li+ intercalation anomaly up to LiC2, within ultra-low graphite content electrode significantly improve graphite electrode capacity beyond 372 mA h g-1. Additionally, when the battery operated at sub-zero temperature, this unique electrode structure with higher conductive environment help to overcome the sluggish desolvation process at interface and slow diffusion in the bulk electrodes. This finding shed a new light in the graphite chemistry and pave the way on the development of anode-less lithium-ion batteries..